Chairpersons: Laura Rontu, Stefan Wacker
Satellite observations of cloud properties are of critical importance for a number of established, operational, and emerging applications serving a wide user community. Examples include the support to nowcasting activities in National Weather Services for the anticipation of evolving severe storms, icing risk evaluation for air traffic, estimation of surface radiation for photovoltaic systems. Numerical Weather Prediction Models (NWP), whilst generally not directly assimilating cloud products, use them for model evaluation and, in the context of climate change, Thematic Climate Data Records from level-2 products can support Climate Analysis. Cloud products are also direct inputs to several level-2 retrievals such as Atmospheric Motion Vectors (AMV), for which quality cloudy pixel identification and height assessment are crucial for their use in NWP.
Similarly, satellite observations of aerosol properties provide support to regulatory and legislative activities in Member States to support air quality monitoring and climate products, particularly in case of dust storms or volcanic ash events. The Copernicus Atmosphere Monitoring Service (CAMS) facilitates the use of the data for this purpose and has a need for high quality near-real time operational aerosol products for use in data assimilation. High quality aerosol products are becoming increasingly important for NWP and climate modelling due to the influence of aerosols on the radiation budget and their role in cloud processes and precipitation.
The potential for EUMETSAT to provide state of the art cloud products will significantly increase with the Meteosat Third Generation (MTG) and the EUMETSAT Polar System programme Second Generation (EPS-SG) and with the possibility of deriving cloud properties from the Copernicus Sentinel-3 instruments. Improvements include higher spatial resolution and richer spectral coverage, which together will allow more accurate cloud detection, estimation of the cloud phase, layering, altitude and spatial inhomogeneity, at the same time maintaining continuity with the legacy products based on current instruments.
Moreover, EUMETSAT, as the only European agency providing aerosol products for near real time services, will significantly benefit from the new suite of instruments, such as dedicated aerosol polarimeter (3MI), the Multi Angle Polarimeter (MAP) from the Copernicus CO2M mission and from synergy between sensors. These new sensors will allow the exploration of the new information from multi-angle, multi-spectral polarimetric observations together with other instrument classes, to improve estimates of the aerosol optical depth, aerosol type, optical characteristics and layer height.
The talk will provide an overview of the activities within EUMETSAT to prepare for the challenges and opportunities offered by the new imagers and spectrometers on board of the upcoming geostationary and polar orbiting missions, will outline the potential for development of multi-instrument synergistic products, and discuss the plans for calibration and validation of level-2 products against surface and satellite-borne reference datasets.
How to cite: Bozzo, A., Chimot, J., Fougnie, B., Guermazi, H., Jackson, J., Jafariserajehlou, S., Lutz, H. J., Marbach, T., Martins, E., Sasi, S., Spezzi, L., Vazquez Navarro, M., and Watts, P.: EUMETSAT plans for cloud and aerosol products from the next generation geostationary and polar orbiting satellites, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-402, https://doi.org/10.5194/ems2022-402, 2022.
The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) generates and distributes high quality long-term climate data records (CDR) of energy and water cycle parameters, which are freely available.
In 2022, a new version of the “Surface Solar Radiation data set – Heliosat” will be released: SARAH-3. As the previous editions, the SARAH-3 climate data record is based on satellite observations from the first and second METEOSAT generations and provides various surface radiation parameters, including global radiation, direct radiation, sunshine duration, photosynthetic active radiation and others. SARAH-3 covers the time period 1983 to 2020 and offers 30-minute instantaneous data as well as daily and monthly means on a regular 0.05° x 0.05° lon/ lat grid. Compared to previous versions, the data quality of SARAH-3 has been substantially improved over snow-covered surfaces, e.g, in the Alpine region, by the use of an internally derived snow mask. SARAH-3 will be accompanied by a near-realtime data processing, which enables operational applications, e.g., climate monitoring
In this presentation, an overview of the SARAH climate data record and example applications will be given. A focus will be on the SARAH-3 developments and validation with surface observations. Further, SARAH-3 will be used for the analysis of climate variability and potential trends in Europe during the last decades. The data record reveals that there is a positive trend of surface solar radiation in Europe during the last decades, which is superimposed by decadal and regional variability. The most significant brightening during the last decades is estimated for spring.
How to cite: Pfeifroth, U., Drücke, J., Trentmann, J., and Hollmann, R.: Surface Solar Radiation based on Satellite Observations – the new SARAH-3 Climate Data Record, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-656, https://doi.org/10.5194/ems2022-656, 2022.
As part of a restructuring of the solar radiation measurement network, the German Meteorological Service (DWD) is pursuing the goal of expanding its high-quality surface measurements using pyranometers (to 42 stations) while discontinuing measurements with other instruments. At the same time, surface solar radiation products from satellite data are progressively improving in quality and can be used to compensate for the reduction of ground measurements and to increase the spatial coverage of solar radiation information over Germany. For this purpose, the project DUETT aims at a merging of solar radiation data from the 42 pyranometer stations and near real-time data based on measurements from METEOSAT-SEVIRI (with a spatial resolution of about 5 km). As products, hourly data of the global horizontal irradiance (GHI) and the sunshine duration (SDU) will be provided on a 2 x 2 km grid for Germany with a time delay of 15 minutes after each full hour.
Merging is performed in three main steps: 1. Time aggregation to derive hourly data from instantaneous 15-minute measurements of the satellite; 2. Determination of deviations between hourly satellite and ground measurements; 3. Interpolation of the deviations to target grid of 2 km resolution using Ordinary Kriging. These three basic steps involve an 'optical flow' technique to generate intermediate images of the satellite data, a correction algorithm for the clear-sky satellite data to consider the impact of varying water vapour columns on surface radiation and a regression approach to reduce systematic deviations between satellite and station data. We present the latest version of the merging procedure for both radiation parameters GHI and SDU. The steps of the algorithms are illustrated, strategies for correcting systematic errors in the satellite data are shown and open issues are discussed. Furthermore, validation results based on independent validation data and based on cross validation will be presented.
How to cite: Brinckmann, S., Klameth, A., and Trentmann, J.: Combination of satellite and ground measurements of hourly surface solar radiation data in Germany, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-96, https://doi.org/10.5194/ems2022-96, 2022.
Satellite images in the solar spectrum provide high-resolution cloud and aerosol information and present promising observations for data assimilation and model evaluation. While visible channels contain information on the cloud distribution and cloud optical thickness, near-infrared channels are in addition more sensitive to cloud microphysical properties and can be used to distinguish between water and ice clouds. The assimilation of these channels is therefore expected to improve the vertical cloud structure and correct errors in effective droplet and ice particle radii.
The direct assimilation of satellite radiance in operational systems has so far been restricted to infrared and microwave observations. This is because sufficiently fast and accurate forward operators for visible and near-infrared radiances were not yet available, which is related to the fact that multiple scattering makes radiative transfer at solar wavelengths complicated and standard radiative transfer solvers computationally expensive. MFASIS, a 1D radiative transfer method based on compressed look-up tables, is sufficiently accurate and orders of magnitude faster, but limited to visible channels and clouds.
After discussing the limitations in the current version of MFASIS that prevent it from simulating near-infrared channels accurately, we present an alternative approach that increase the accuracy significantly for near-infrared channels. In this novel approach, the look-up tables are replaced by a neural network reducing the computational costs and allowing for additional input parameters. Those parameters enable us to describe the vertical distribution of cloud parameters, in particular the effective radius profiles, more accurately. We will demonstrate that the errors are reduced considerably, compared to the original MFASIS method. The new approach is tested for the SEVIRI 1.6mu channel using model output from IFS and the convective-scale data assimilation system KENDA, which is based on the ICON-D2 model.
How to cite: Baur, F., Scheck, L., Stumpf, C., Köpken-Watts, C., Bach, L., and Potthast, R.: Efficient generation of synthetic near-infrared satellite images for model evaluation and data assimilation, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-374, https://doi.org/10.5194/ems2022-374, 2022.
Global horizontal irradiance (GHI) is the primary driver for photovoltaic (PV) technology. For PV system design and monitoring, hourly and sub-hourly GHI from reanalysis and satellite-based data are frequently used, especially in data-poor regions like Sub-Saharan Africa. However, the use of these datasets is uncertain and need to be assessed in detail. In this study, we evaluated the performance of state-of-the-art reanalysis and satellite-based datasets (ERA5, CAMS, MERRA-2 and SARAH-2) with in situ measurements of hourly GHI for the main climatic zones (Guinea, Savannah, and Sahel) in West Africa. The in situ measurements come from novel regional and national meteorological networks consisting of 51 automatic weather stations in Burkina Faso and Ghana. The performance assessment was done for the year 2020 for different weather conditions (cloudy, clear and all sky). The effects of clouds and aerosols were also investigated. Moreover, a new overall performance measure is introduced for joint evaluation of different standard measures, such as the root-mean-square error and the index of agreement. The results show that the data from SARAH-2 performs best under cloudy-sky conditions, while ERA5 performs worse under all atmospheric conditions. The low performance under cloudy skies for all datasets is the result of a large bias observed during the Harmattan period, when the region has a high concentration of aerosols. The average diurnal variation of GHI shows good agreement between the in situ measurements, the satellite and the reanalysis data under clear and all-sky conditions, but an overestimation under cloudy skies at some stations. The new overall performance value clearly indicates hourly GHI from SARAH-2 is the best alternative for assessing solar energy in West Africa.
How to cite: sawadogo, W., Bliefernicht, J., Fersch, B., Salack, S., Guug, S., Diallo, B., Ogunjobi, K. O., Nacoulma, G., Tanu, M., Meilinger, S., and Kunstmann, H.: In Situ Based Performance of Satellite- and Reanalysis-derived Hourly Global Horizontal Irradiance Products over West Africa, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-52, https://doi.org/10.5194/ems2022-52, 2022.
Chairpersons: Stefan Wacker, Laura Rontu
Radiation in the atmosphere provides the energy that drives atmospheric dynamics and physics on all scales, from cloud particle growth to global weather and climate. Radiation schemes in global weather and climate models make assumptions to simplify the complex interaction of radiation with the Earth system. Capturing cloud-radiation interactions is particularly challenging since clouds vary strongly on small spatial and temporal scales not resolved in the models, and interact strongly with radiation. Uncertainties in these assumptions in the radiation scheme and the cloud, aerosol, gas and surface inputs lead to uncertainties in multiple weather and climate processes, such as energy balance, cloud development and dynamics.
The modular radiation scheme ecRad (Hogan and Bozzo, 2018, Rieger et al. 2019) is operational in ICON at DWD since April 2021 and provides the opportunity to vary parametrisations and assumptions individually to determine their impact. Several options are available for the radiation solver, cloud vertical overlap and horizontal inhomogeneity treatment and cloud hydrometeor optical property parametrisations. The solver SPARTACUS is the only radiation solver in a global model that can treat 3D radiative effects.
Using global satellite and surface data and high-resolution surface radiation measurements gathered during the FESSTVaL campaign (https://fesstval.de), we evaluate the radiation and cloud parametrisations on local to global scales and investigate the sensitivity of radiation results to model assumptions and cloud properties and the role of cloud-radiation interactions. In ICON, ecRad improves the global radiation balance, model physics and forecast performance as evaluated against observations.
References:
Hogan, R. J., & Bozzo, A. (2018), A flexible and efficient radiation scheme for the ECMWF model. Journal of Advances in Modeling Earth Systems, 10, 1990-2008. https://doi.org/10.1029/2018MS001364
Rieger, Daniel, Martin Köhler, Robin J. Hogan, Sophia A. K. Schäfer, Axel Seifert, Alberto de Lozar and Günther Zängl (2019). ecRad in ICON - Implementation Overview, Reports on ICON
How to cite: Schäfer, S., Köhler, M., Hogan, R., Ahlgrimm, M., Rieger, D., Schlemmer, L., Sakradzija, M., Mol, W., van Heerwarden, C., and Jakub, F.: Radiation and cloud parametrisation in ICON on local to global scales, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-632, https://doi.org/10.5194/ems2022-632, 2022.
Within the framework of the project NUKLEUS (Actionable local climate information for Germany) first long-term simulations with COSMO 6.0 and ICON-CLM based on the latest release ICON NWP 2.6.4 have been performed. These simulations were driven by ERA5 reanalysis data, which were downscaled to the EUR-11 EURO-CORDEX grid having a resolution of about 12 km. To capture the whole EURO-CORDEX domain with the ICON-CLM, a R13B05 icosahedral grid with a shifted North pole was chosen. The simulation period covers more than two decades starting from 1981.
In our presentation we aim to study the basic behaviour of transient ICON-CLM hindcasts in “local area mode” configuration. First evaluation results showed ‘questionable’ results for specific periods. After detailed analysis for the reasons of the model deficits, sensitivity experiments were carried out with purely lateral nudging and additional upper boundary nudging for ICON but for COSMO as well. It will be shown that the integration of both models leads to comparable solutions and a comparable level of sensitivity to weaker atmospheric forcing.
Furthermore to the search for an optimal configuration / Keeping in mind a first ‘optimal’ configuration, the performance of ICON-CLM and COSMO-CLM is investigated. In addition to a standard evaluation of relevant climatological parameters, the characteristics of radiative fluxes, clouds and the water budgets are analyzed. Systematic differences as well as similarities between both model simulations will be emphasized during this presentation. We will in particular focus on the impact of different aerosol climatologies on the model's quality.
How to cite: Petrik, R.: Towards transient aerosols in ICON-CLM - Impact of different aerosol climatologies, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-622, https://doi.org/10.5194/ems2022-622, 2022.
ACCORD is a NWP consortium for development of limited-area short-range numerical weather prediction (NWP) system, representing 26 European and North-African national weather services. Various cloud microphysics and radiation schemes available in ACCORD framework are being developed to account for aerosol impact on the cloud, precipitation and fog formation as well as on the direct and indirect aerosol effects on radiation transfer. As a short-range limited area NWP system, ACCORD does not aim at fully integrated representation of weather-aerosol-chemistry dynamics but relies on external climatological and near-real-time aerosol data, currently obtained from Copernicus Atmosphere Monitoring Service (CAMS). Preliminary results of single-column and full model experiments in cases of dust intrusion and very clean air illustrate the interactions, sensitivities and uncertainties of the forecast, related to the choices of aerosol source data, parametrization schemes and their settings.
Currently, the HARMONIE-AROME model within ACCORD uses monthly climatologies of total aerosol optical depth at 550 nm of four aerosol types (land, sea, urban and desert) for radiation parametrizations only. These data come in coarse global grid and represent the average conditions. Radiation impacts of dust and carbon aerosols, that can be significant especially during dust intrusions and wildfires, cannot really be taken into account. On the other hand, currently the aerosol impact on liquid and ice cloud formation and evolution are not taken into account at all. The most important aerosol impacts on cloud microphysics are presumably related to the water-soluble aerosol like sulfates and sea salt, that are abundant but regionally variable in the atmosphere.
The possibility to use near-real-time aerosol as an external source in the high-resolution NWP system requires that the model is adapted to use these data in an optimal way. For radiation, this means better definition of the aerosol optical properties depending on the species and wavelengths as well as on the real-time atmospheric humidity at different elevations. For the single-band radiation schemes, aerosol optical depths of the aerosol mixture for short-wave and long-wave bands are obtained as weighted averages, based on the data of aerosol mass mixing ratios and the prescribed aerosol inherent optical properties. Considering cloud-precipitation microphysics, droplet number concentration and specific cloud ice content depend on aerosol. These influence the cloud, precipitation and fog evolution and also, via the cloud particle size, the radiation transfer in clouds.
How to cite: Rontu, L., Sekula, P., and Sljivic, A.: ACCORD aerosols, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-45, https://doi.org/10.5194/ems2022-45, 2022.
How to cite: Flemming, J., Remy, S., Inness, A., Ades, M., Parrington, M., Garrigues, S., Hogan, R., Haiden, T., and Engelen, R.: The impact of the dust transport events over Europe in March 2022 on the weather forecast with the ECMWF model, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-627, https://doi.org/10.5194/ems2022-627, 2022.
In the context of global warming, the share of renewable energy sources (RES) is drastically increasing. A promising source to transit towards a more sustainable energy system is solar energy. However, like many others RES, solar energy is intermittent with high spatio-temporal variability and high dependence on weather conditions, so that the control over production is limited. As a consequence surface solar irradiance (SWD) forecasts based on Numerical Weather Prediction (NWP) models are essential to help incorporating solar energy into the electrical grid and ensure the network stability.
The performances of NWP models in terms of solar radiation have rarely been studied, though, especially over large domains and long periods. However, the growing interest from various end users including the photovoltaic community is now shedding light on this critical question. Errors in NWP models can be consequent. For instance the annual mean bias and RMSE for 2020 amount 18Wm-2 and 97Wm-2, respectively, for AROME, the operational NWP model of Météo-France at 1.3km horizontal resolution. Our objectives is to characterize the performance of AROME for solar radiation, which will allows in a second step to improve these performances by refining the physical parameterizations impacting solar radiation, primarily the microphysical scheme and the radiative code.
To this end, a full year of hourly AROME forecasts is compared to corresponding in-situ SWD measurements from the network of pyranometers operated by Météo-France. This network gathers about 180 high-quality pyranometers over metropolitan France. A thorough analysis of cloud satellite products is also carried on to identify situations which contribute most to radiation errors. Then physical processes are prioritized to be improved in AROME to reduce errors.
Results show that the first source of errors occurs when the sky is cloudy in both model and observations with an annual bias of 24Wm-2 (contributing to 89% of the total bias) against 3Wm-2 in clear skies (contributing to 3% of the total bias). The missed cloudy situations and the false alarms contribute respectively to 14% and -6% of the total bias. While part of the bias in clear sky condition is due to an unrealistic representation of aerosols in AROME, the bias in cloudy conditions seems to be mostly related to incorrect cloud optical properties. Further investigations allows to split these errors into liquid water path and effective radius errors, and to focus on the most problematic cloud types. In particular, not accounting for snow in the radiation scheme contributes to the positive bias, and misrepresenting cirrus clouds seem to contribute mostly to solar radiation errors.
How to cite: Magnaldo, M.-A., Libois, Q., Lac, C., Riette, S., and Fontaine, E.: Evaluation of surface solar irradiance forecasts by the NWP model AROME, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-235, https://doi.org/10.5194/ems2022-235, 2022.
Clouds are highly variable in their structure as well as phase, resulting in a potentially large influence on actinic flux densities. Chemistry-transport models rely on accurate simulations of actinic flux densities to reproduce the essential impact of photolysis processes, thus the need for accurate radiative transfer calculations in the presence of clouds arises. Current studies show that under clear sky conditions simulated and measured UV/VIS actinic flux densities are typically within 10%, independent of wavelength. On the other hand, the impact of clouds on actinic radiation is more difficult to reproduce correctly when dependent on cloud structure, phase and position, flux densities can be significantly smaller or greater compared to clear sky conditions.
Following a similar approach by Ryu et al., 2016, UV/VIS spectral actinic flux densities were calculated utilizing cloud products from geostationary satellites (NASA SatCORPS). In this work, the latest version of the libRadtran model has been used, as well as aerosol properties (MODIS, MOD08_D3), surface albedos (MODIS) and total ozone columns (TEMIS, MSR-2) from polar-orbiting satellites as key input to simulate actinic flux densities in a range 280-650 nm. The evaluation of the model results is made by comparison with measured data from several campaigns with the research aircraft HALO (High Altitude and Long Range Research Aircraft) with a total of around 90 flights.
Using the NASA SatCORPS products (cloud phase, cloud optical depth, cloud top height, cloud liquid or ice water content and cloud particle size) 1-D radiative transfer calculations were conducted. Radiative properties of water clouds are reliably reproduced using look-up tables based on pre-conducted radiative transfer calculations using Mie theory. On the other hand, ice clouds and their correct parametrizations are challenging because of the wide range of possible ice crystal variations. Moreover, small-scale variations captured by the highly resolved aircraft measurements cannot be reproduced completely, due to the lower spatial and temporal resolution of satellite observations. The final intent of this study is to assess the quality of the radiative transfer modelled actinic flux densities and their potential to improve chemistry-transport models.
How to cite: Kremer, A., Bohn, B., Palikonda, R., and Smith Jr., W. L.: 1D Radiative Transfer Model Calculations of Solar Actinic Flux Densities with Satellite Cloud Products – Comparison with Airborne Measurements on HALO, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-516, https://doi.org/10.5194/ems2022-516, 2022.
The amount of solar radiation that reaches the Earth’s surface is strongly influenced by clouds and aerosols. This results in a complex pattern of radiation at the surface with cloud shadows and regions with enhanced solar radiation. Cloud enhancements can cause surface irradiances up to 25% higher than under clear sky conditions. Insight into these peaks is valuable to operators of the electricity grid, as these peaks can cause grid voltages to exceed the safety limits. Furthermore, the radiation at the surface impacts the surface fluxes, boundary layer turbulence and clouds. Therefore, proper modelling of surface radiation is important for predictions of solar energy production and for detailed weather forecasts. Current 1D calculations of radiative transfer cannot capture the complex pattern of surface radiation, whereas 3D calculations are very costly. In this study, we developed a simple method to account for the 3D radiative effects at the surface in LES. The horizontal spreading of the diffuse radiation is accounted for by applying a spatial filter to the surface diffuse radiation field. With this filter, we add only little extra complexity to the existing 1D calculation. Therefore, our method is computationally efficient. The filtering of the diffuse radiation is applied to the results of a Large Eddy Simulation for a summer day in Cabauw, the Netherlands, on which shallow cumulus clouds formed during the day. The results of the LES simulation are compared to detailed high-quality observations (1Hz). Without the filtering, the cloud enhancements are not captured at all, and the probability distribution of global radiation is unimodal, whereas the observed distribution is bimodal. After filtering, our results closely match with the observations. The probability distribution of global radiation is now bimodal and cloud enhancements are simulated. We found that small changes in the filter width do not strongly influence the results. Furthermore, we showed that the width of the filter can be parameterized as a linear function of one variable related to the cloud field, e.g. the maximum cloud size or the cloud base height. Hence, this work presents a proof-of-concept for our method to come to more realistic surface irradiances by filtering diffuse radiation at the surface.
How to cite: Tijhuis, M., van Stratum, B., and van Heerwaarden, C.: A computationally efficient parameterization for 3D radiative effects at the surface in large-eddy simulations, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-41, https://doi.org/10.5194/ems2022-41, 2022.
Clouds strongly regulate how much radiation reaches the earth’s surface. Due to scattering and absorption processes within clouds, surface radiation can be highly variable both in space and time. Accurately capturing the high surface heterogeneity of solar radiation is important, for example for grid operators who need to ensure the safe ingestion of solar energy into the energy grid. In Numerical Weather Predictions and Large-Eddy-Simulations, radiation is often computed using one-dimensional radiative transfer, even though this can produce unrealistic surface irradiance fields. Applying three-dimensional radiative transfer is much more accurate because of the possibility of the horizontal transfer of radiation. However, applying three-dimensional radiative transfer in simulations is for most applications still too expensive.
In this study we investigated cloud-radiation interactions by applying either one-dimensional or three-dimensional radiative transfer using Large-Eddy-Simulations. The performance of the respective simulations were weighted against high quality surface observations from the Baseline Surface Radiation Network at Cabauw. We simulated/ observed a case representing a summer’s day in the Netherlands where shallow cumulus developed late in the morning and dissipated again later in the afternoon.
Simulations where one-dimensional radiative transfer was applied did not reproduce the observations well. Although being over a factor ten slower, simulations with three-dimensional radiative transfer applied did resemble observations much better. Still, for the simulations with three-dimensional radiative transfer the underestimation of diffuse radiation was considerable.
To speed up the three-dimensional radiative transfer simulations we investigated an option that allowed the radiative transfer calculations to not fully converge. Using this incomplete solve option we found that biases in global radiation, sensible and latent heat remained smaller than for one-dimensional radiative transfer simulations, when we compared both to a fully solved three-dimensional radiative transfer run.
With this work, we aimed to provide an insight into the relevance of three-dimensional radiative transfer application in shallow cumulus cloud fields emphasizing the need for further development of computationally efficient three-dimensional radiative transfer solvers in LES.
How to cite: Wiltink, J., Veerman, M., Maier, R., van Heerwaarden, C., Jakub, F., and Mayer, B.: One- and Three-Dimensional radiative effects in shallow cumulus cloud fields: Large-Eddy Simulations and Observations, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-283, https://doi.org/10.5194/ems2022-283, 2022.
Chairpersons: Laura Rontu, Stefan Wacker
In this paper, we apply the method of radiative closure to the measurement dataset of supersite DWD/MOL-RAO (Deutscher Wetterdienst, Meteorological Observatory Lindenberg – Richard Assmann Observatory) in Lindenberg (Tauche) Germany.
The MOL-RAO observatory is a supersite for measurements of atmospheric parameters and ground-based radiative transfer measurements. We use these measurements as input files to perform high accuracy radiative transfer simulations for cloud-free conditions. Some of the measured atmospheric parameters included in the input files are water vapour, ozone, aerosol optical depth for different wavelengths, single scattering albedo, and atmospheric pressure. For longwave simulations, water vapour and temperature profiles with good precision and estimated vertical positions of aerosol layers are provided as inputs.
We compare the results of the high accuracy simulations with ground-based radiation measurements from the highest WMO quality standards. The comparisons are conducted for every minute for broadband radiation (solar diffuse, direct and global) and every six minutes for spectral measurements (direct and global) in the range 290 - 1000 nm with a spectral resolution of 1nm.
After comparing the high accuracy simulation results with broadband and spectral radiation measurements for the same timestamps, we evaluate and improve both the simulation procedure and the measurement of input parameters (atmospheric composition, aerosol amount and properties). This method is called the 'radiative closure.' In the paper, we also present sensitivity analyses to investigate the influence of the different atmospheric parameters on the radiation, particularly the aerosol properties for the radiation in solar wavelengths, vertical profiles of temperature and water vapour, and aerosol properties for the thermal radiation.
How to cite: Doppler, L., Wacker, S., Mäusle, S. J., Riedel, J., and Balakrishnan, P.: Radiative closure (simulation ↔ measurements) with a complete input/output measurement dataset of supersite Meteorological Observatory Lindenberg (Germany), EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-262, https://doi.org/10.5194/ems2022-262, 2022.
Boundary-layer clouds trigger large fluctuations in solar surface irradiance and in surface heat fluxes. The incoming radiation in shadows is almost an order of magnitude less than under clear sky, while peaks near clouds shadows can sometimes reach a 50% increase with respect to clear sky, due to scattering of sunlight in cloud edges. Performing large-eddy simulation (LES) with realistic surface solar irradiance patterns under broken clouds remains a challenge. First, this is due to the absence of spatial radiation observations that capture individual cloud shadows at a typical LES resolution (~50 m), second, because cloud fields need to be accurate up to a very high detail level and, third, the 3D aspects of radiative transfer needs to taken into account.
The Shedding Light On Cloud Shadows (SLOCS) project aims to overcome these challenges by i) gathering spatial observations in a spatial grid fine enough to capture individual clouds with a novel instrument, and ii) further developing 3D radiative transfer models for LES with optimal balance between detail level and performance. The FESSTVaL campaign in Lindenberg, Germany in early summer 2021 provided a unique opportunity for the SLOCS team to address those challenges. In FESSTVaL, we performed grid measurements of radiation, while benefiting from complementary boundary-layer and cloud observations of other research groups. In addition, FESSTVaL brought a boundary-layer modelling community together ranging from people working on NWP models to people working on fine-scale LES. This permitted comparison of the ability of different modelling techniques to capture surface irradiance variability driven by clouds.
Here, we will present the design and the results of LES of four selected case studies based on FESSTVaL data: one clear sky case, two shallow cumulus cases with different cloud depths, and one deep convection case with cold pools. First, we will show how we have extended and accelerated the RTE+RRTMGP radiation model to take into account 3D interactions between clouds and radiation, to enable comparison against our grid observations near the Falkenberg measurement tower. Second, we will present the outcome of the LES of the four cases and evaluate simulated solar and turbulence surface fluxes, boundary layer structures and cloud properties against FESSTVaL observations. Third, we will show a comparison between our own 25 m resolution large-eddy simulations with GPU-accelerated MicroHH against 100 m resolution simulations of the ICON large-eddy model and 2 km resolution simulations of the ICON NWP model. In our analyses, we compare the different modelling techniques in their ability to reproduce the FESSTVaL cases. This comparison will address the balance between grid resolution and domain size as well as the necessity for lateral inflow and outflow boundary conditions in modelling accurate surface solar irradiance fluxes.
How to cite: van Heerwaarden, C., Veerman, M., Mol, W., van Stratum, B., Tijhuis, M., Heusinkveld, B., and Sakradzija, M.: The Shedding Light On Cloud Shadows project: measuring and simulating surface solar irradiance under broken clouds, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-187, https://doi.org/10.5194/ems2022-187, 2022.
Clouds cast shadows and locally enhance solar irradiance through absorbing and scattering sunlight, resulting in fast and large solar irradiance fluctuations on the surface.
The resulting spatiotemporal variability poses a challenge for solar energy production amidst increasing need for reliable renewable energy. It furthermore influences biological processes and the exchange of water and energy. Yet, no numerical weather prediction model is able to reproduce the observed local properties of irradiance, due to the complexity of radiative transfer and its dependence on accurately resolved cloud fields. Improving the radiative transfer models, whether it involves running full Monte Carlo raytracing in academic setups or simplified paramerizations, ultimately requires observations for validation. However, dense spatial observation of irradiance on the scale of cloud shadows are rare. Even single 1D time series are rarely available at high enough temporal resolution to capture irradiance variability.
In ongoing work, we provide those missing observations using a dense network of our custom, low-cost radiometers that we deployed at two field campaigns in summer 2021, FESSTVaL (Germany) and LIAISE (Spain). I will present our gathering and analyses of these new and detailed observations of surface irradiance to address knowledge gaps in our physical understanding and provide validation datasets for models. The instruments, which sample at 10 Hz, are able to closely match expensive conventional instruments, and combined with skyview imagery, the spatial observations are directly linked to observed clouds. Information about atmospheric water content can be retrieved using the information from water vapour absorption bands.
To complement these short term spatial data, long-term statistics of irradiance variability are derived from a 10-year 1 Hz resolution dataset from the Baseline Surface Radiation Network station in Cabauw, the Netherlands. Distributions and typical spatio-temporal scales of cloud shadows and irradiance peaks can be related to cloud type and meteorological conditions. The gathering and study of these datasets will lead to a better understanding of the physics. E.g., whether the dominant mechanism driving irradiance peaks is either forward scattering in transparent parts of clouds or 'reflections' from cloud sides. Furthermore, these datasets will help validate models, and ultimately improve our ability to accurately forecast irradiance variability at the small scales.
How to cite: Mol, W., Heusinkveld, B., Hartogensis, O., and van Heerwaarden, C.: Observing Cloud-Driven Surface Irradiance Patterns, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-50, https://doi.org/10.5194/ems2022-50, 2022.
Clouds modify surface solar irradiance fields by scattering and absorbing radiation. The spatial distribution of surface irradiance drives horizontal heterogeneity in the surface heat and moisture fluxes, which may affect the further development of boundary layer clouds. Additionally, spatial variability of solar irradiance affects the electricity production by solar energy. However, accurately capturing the spatial distribution of surface solar irradiance in cloud-resolving models is not straightforward. Radiative transfer in the atmosphere is generally solved using 1D two-stream approximations, which are computationally efficient but neglect the horizontal energy transport by radiation. Alternatively, realistic surface solar irradiance fields can be computed using Monte Carlo ray tracing methods, which are highly accurate but computationally expensive and therefore often only used for a limited number of cloud fields. Moreover, ray traced irradiance fields are only as accurate as the input cloud fields and therefore still require validation by observations, which are generally only available as single point measurements at a relatively coarse temporal resolution. In this study, we make use of a dense spatial grid of radiation measurements that was set-up during the FESSTVaL measurement campaign in Germany, and aim to provide a unique validation of the spatial variability in surface irradiance fields produced by a suite of radiative transfer approximations. First, we run large-eddy simulations of three different days during the campaign, two days with shallow and one day with deep convection, to generate high-resolution cloud fields that can be validated using LIDAR observations. Radiative fluxes are then computed for each cloud field using the two-stream approximation, Monte Carlo ray tracing, and a number of approximations for three dimensional radiative transfer such as tilted columns and the TenStream solver. The comparison of these various radiative transfer techniques against observations may contribute to a better understanding of the spatial variability of surface solar irradiance under cumulus clouds. Moreover, this can give a better insight into which radiative transfer approximations can capture the surface irradiance variability to sufficient accuracy for solar energy applications.
How to cite: Veerman, M., Mol, W., van Stratum, B., and van Heerwaarden, C.: 3D Radiative Transfer through Cumulus Clouds, Comparing Modeling to Observations, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-149, https://doi.org/10.5194/ems2022-149, 2022.
For more than 70 years measurements of the global and diffuse solar surface radiation have been taken within the DWD measurement network. Since 2006 those two radiation quantities are recorded with a temporal resolution of 1 minute at currently more than 30 stations.
At Meteorological Observatory in Lindenberg, we developed a new optimal estimation-based retrieval algorithm to estimate the AOD from ground-based global and diffuse broadband radiation measurements, measurements of the total column water vapor from GNNS, and ozone from the satellite-borne instrument OMI. The suitability of using the global surface radiation as a source to estimate the Aerosol Optical Depth (AOD) at certain wavelength based on radiative transfer simulations was already shown in several studies. Adding the information on the diffuse surface radiation increases the information content on the aerosol size distribution. Thereby we could reduce the error between the AOD derived from broadband measurements and the AOD derived from photometric measurements. Comparisons of the derived AOD with 7 collocated AERONET sites in Germany show a very good agreement with a monthly mean difference below 0.02 in the AOD. The differences in the AODs can be simply described by the differences in observed airmass and larger measurement errors of the broadband observations.
With the radiative transfer model, used in the retrieval algorithm as a forward model, we calculate for each measurement the incoming surface radiation for a cloud and aerosol-free atmosphere to estimate the direct aerosol effect for the daily mean AOD. For this reason, the estimated direct aerosol effect is limited to days with at least 10 minutes of cloud-free observations.
In our presentation, we will show validation results of the algorithm as well as trend analysis of the AOD and direct aerosol effect in Germany at available pyranometer sites since 2006.
How to cite: Filipitsch, F., Doppler, L., Seifert, A., and Wacker, S.: Estimation of the spectral aerosol optical depth from broadband surface radiation measurements and quantification of the direct aerosol effect in Germany, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-546, https://doi.org/10.5194/ems2022-546, 2022.
The German Weather Service (DWD) initiated the operational observation of solar global and diffuse radiation at the Observatory Potsdam in 1937. Nowadays, these components are observed at 35 stations using thermopile-based pyranometers. Most of the stations are also equipped with a pyrgeometer to record the downwelling long-wave radiation.
The solar radiation experienced major decadal variations in Germany over the past 80 years. While a significant decrease between 1950 and 1985 occurred, a continuous increase can be observed since 1985 with some of the highest annual means ever recorded in the past five years. The decrease in the second half of the 20th century with the subsequent increase is commonly referred to as dimming and brightening. While these variations were most likely due to anthropogenically caused variations in the aerosol load, the recent increase is not yet fully understood. Since aerosol loads have stabilized at low levels at the beginning of the 21th century, the direct aerosol effect might be less prominent at present. Instead, changes in cloudiness may have become more important.
In order to disentangle the observed trends in the radiative fluxes and to determine the contribution from aerosols and clouds separately we also use radiation data from the BSRN station at the Meteorological Observatory Lindenberg. The station was established in 1994 and high accuracy measurements of downwelling long-wave radiation and all three components of downwelling short-wave radiation (global, diffuse and direct) have been recorded continuously since then. We use a 1-dim. Radiative Transfer Model (RTM) to calculate the short- and long-wave cloud-free fluxes in order to quantify the cloud radiative effect. Similar, we estimate the direct aerosol effect. Preliminary results indicate a decrease in the cloud radiative effect over the past 20 year, which can imply a decrease in cloud cover but may also include a shift towards a different cloud type and/or a change in microphysical cloud properties. Finally, we present methods which can be used to determine the spectral AOD and the cloud-radiative effect for sites or periods when no direct observations of the spectral AOD and no information about the vertical temperature and humidity structure of the atmosphere for thermal RTM calculations are available.
How to cite: Wacker, S., Doppler, L., Becker, R., and Filipitsch, F.: The impact of clouds and aerosols on the radiative fluxes in Germany over the past 70 years from a surface perspective, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-533, https://doi.org/10.5194/ems2022-533, 2022.
The ASPIRE project aims to contribute to the scientific knowledge of interdisciplinary aspects that are related with solar radiation by investigating the effect of various atmospheric parameters such as clouds, aerosols, water vapor and absorbing trace gases to the Spectral Solar Irradiance (SSI) reaching the Earth’s surface. Such aspects deal with solar energy research and technology (e.g. Photovoltaic Systems, PV), impact on health (melanoma, skin cancer and Vitamin D efficiency), agriculture (photosynthetically active radiation, PAR, and crop production) and the complexity of the SSI determination through an atmosphere with various spectral absorbing, scattering and reflecting atmospheric constituents.
The project has four specific objectives: (a) To investigate the effect of atmospheric composition in different solar spectral regions, (b) To assess the impact of atmospheric composition on UV Index, Vitamin D and PAR, (c) To improve PV efficiency based on spectral solar data for various atmospheric composition cases, (d) To evaluate the performance of the Solar Energy Nowcasting SystEm (SENSE) using real solar spectra. The means to fulfil these objectives is a sophisticated atmospheric field experiment that has been held in the city of Athens, Greece, with a unique set of instrumentation and a synergistic approach on the retrieved datasets. Atmospheric composition and solar radiation related measurements and models are coordinated in ASPIRE in order to contribute to the following scientific advancements:
How to cite: Eleftheratos, K., Raptis, I.-P., Kouklaki, D., Kazadzis, S., Psiloglou, B., Founda, D., Kosmopoulos, P., Fountoulakis, I., Benetatos, C., Gierens, K., Kazantzidis, A., and Richter, A.: Atmospheric parameters affecting SPectral solar IRradiance and solar Energy (ASPIRE), EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-526, https://doi.org/10.5194/ems2022-526, 2022.
Solar energy nowcasting is a valuable asset in managing energy loads and having real-time information on solar irradiation availability. SENSE is an operational-ready system which exploits satellite retrieved images from the EUMETSAT’s Meteosat Second Generation for cloud microphysics information above a certain location, modelled aerosol optical properties data from the Copernicus Atmospheric Monitoring Service (CAMS), in conjunction with Radiative Transfer Model (RTM) simulations in order to retrieve the Global Horizontal Irradiance (GHI) and the Direct Normal Irradiance (DNI) spectrally (280 - 2800 nm). For a full year period (December 2020-December 2021) a campaign was held in Athens (Greece) in the framework of the “Atmospheric parameters affecting Spectral solar Irradiance and solar Energy” (ASPIRE) project. For the needs of the campaign a number of ground-based instruments were operating, including two pyranometers, a pyrheliometer, a cloud camera, a CIMEL sunphotometer, a BREWER and a PANDORA spectroradiometer and a Precision Spectral Radiometer (PSR).
In this study, we evaluate the integrated outputs of SENSE in W/m2, at 15-minute frequency against the ground-based recordings, for the period of the campaign. A separate assessment of the SENSE’s inputs (cloud and aerosol optical properties) is performed in respect to ground-based retrievals. Finally, deviations between SENSE and measurements are linked to deviations between climatological/satellite-based atmospheric parameters and those retrieved from the ground-based measurements. The detailed evaluation of SENSE inputs and outputs using detailed ground-based data advances our present-day knowledge about the uncertainties of SENSE products, thus improving our understanding of the renewable energy merit in the total energy use for Greece. This effort is important for SENSE users such as the Greek Independent Power Transmission Operator and the Public Power Corporation Renewable of Greece.
How to cite: Raptis, I.-P., Eleftheratos, K., Kazadzis, S., Kosmopoulos, P., Gierens, K., Fountoulakis, I., Papachristopoulou, K., Kouklaki, D., Kazantzidis, A., Benetatos, C., and Psiloglou, V.: Evaluation of the Solar Energy Nowcasting System (SENSE) using Multiple Ground Based Measurements, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-204, https://doi.org/10.5194/ems2022-204, 2022.
The atmospheric aerosols and their direct radiative effects play an essential role on the variability of solar resources on the earth’s surface and, consequently, solar energy potential production, especially in the proximity of aerosol anthropogenic and natural sources. In this work, we investigate the direct impact of total and dust aerosols on two different downwelling surface solar irradiance (DSSI) components, the Global Horizontal Irradiance (GHI) and Direct Normal Irradiance (DNI), under clear-sky conditions and their implications on solar energy. The study focuses on the broader Mediterranean Basin, over a 18-year time period, between 2003 and 2020. In this framework, various studies using total aerosol and dust optical depth (AOD and DOD, respectively) from the satellite-derived ModIs Dust AeroSol (MIDAS) and the model based from the Copernicus Atmospheric Monitoring Service (CAMS) have been appeared in the literature. In this study we use ground-based measurements from the AErosol RObotic NETwork (AERONET) to assess results from the aforementioned datasets/studies. Based on the retrievals of aerosol optical properties from the ground-based measurements, a sensitivity analysis was performed to determine the dependence of the GHI and DNI from aerosol optical properties variability using different time scales and aerosol inputs/datasets with different spatiotemporal resolution. Finally, deviations of the total aerosols/dust effects on DSSI resulting from three datasets (satellite, CAMS, ground-based) are presented and discussed and the reasons of such deviations are presented. The importance of this research lies in the fact that understanding the sensitivity of solar energy applications to the spatiotemporal variability of aerosols and dust, is vital for a sustainable energy transition, energy planning and the efficiency of current and future solar energy related investments.
How to cite: Kouklaki, D., Papachristopoulou, K., Fountoulakis, I., Raptis, I.-P., Kazadzis, S., and Eleftheratos, K.: Direct effect of Aerosols on Surface Solar Radiation (GHI and DNI) for Solar Energy: sensitivity study using CAMS, satellite-based and ground-based measurements , EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-400, https://doi.org/10.5194/ems2022-400, 2022.
The shortwave cloud effect (SCE) is understood as the difference between potential and measured global radiation. The time-space variability of SCE is mainly modified by cloudiness and its type. Proper diagnosis of SCE is a crucial factor from the point of view of climate change modelling, as cloudiness is particularly important in the Earth's energy balance. However, the impact of cloudiness on the changes in SCE is still not well understood.
This research quantifies the SCE depending on cloudiness and cloud types in GZM (Metropolis Górnośląsko-Zagłębiowska) which represent the most urbanized part of Poland. Moreover, the study also assesses long-term variability and trends in SCE and cloudiness. The research is based on unique hourly data of global radiation (W/m2) which, due to its specific location in the center of GZM, represent urban area conditions. The hourly potential global radiation was calculated using the Bird and Hulstrom model. Then the SCE (W/m2) was calculated as the difference between the potential and the measured global radiation. Data on cloudiness, cloud level (CL-Low, CM-Mid, CH-High), and its type were obtained from the synoptic station in Katowice, located 9.6 km from the FNS station. Trends for SCE, cloudiness, and cloud types were calculated by using Mann-Kendall Test. The data covers the years 2002-2021.
In 2002-2021, the annual SCE reaches –145.3 W/m2. During the year, SCE varied from –203.2 (May) to –76.7 (December) W/m2. The strongest SCE was –335.2 W/m2 in May 2010, which may have been due to the contribution of the Eyjafjallajökull volcano eruption (Iceland), whose volcanic ash reduced the transparency of the atmosphere, strengthening the SCE. The weakest SCE occurred in December 2013, reaching –51.3 W/m2.
The SCE during the occurrence of a given cloud level showed that the SCE is the strongest during CL occurrence. The annual average of SCE reached –95.6 W/m2. The weakest annual SCE was found for CM and CH, reaching –23.0 and –32.5 W/m2, respectively. In the annual course of SCE during the occurrence of CL, the SCE was strongest from June to August, reaching –150 W/m2. The SCE for CM was most intense (–36.1 W/m2 on average) from July to October, which coincided with increased CM level cloud frequency in this part of the year.
The trend analysis revealed a reduction in monthly SCE from +6.6 (January) to +27.6 (July) W/m2 per decade (SCE takes negative values, thus positive trends indicate weakening of the effect). The weakening of SCE in these particular months may have been linked to the significant decrease (p<0.05) in the CL frequency (–39.6 hours per decade). Strengthening of SCE in September (–9.4 W/m2 per decade) may have been related to the increase (p<0.1) of CH (26.0 hours per decade).
How to cite: Zajączkowski, D. and Łupikasza, E.: Shortwave cloud effect and its trends in Southern Poland (2002-2021), EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-143, https://doi.org/10.5194/ems2022-143, 2022.
Balloon-based soundings have been carried out for more than 100 years and have since formed an important database and reference for characterizing the 3-dimensional structure of the atmosphere. In addition to the meteorological standard variables trace gases, aerosol and radiation profiles have recently also been recorded using radiosondes.
Since this is significantly more expensive equipment compared to a standard radiosonde, some more effort is required to enable safe soundings and transfer back home for each case. The repetition rates of the soundings are consequently much lower than those of the operational measurements.
The measurement conditions during the sounding differ significantly from the usual conditions for radiation measurements near the ground: temperatures down to -85°C at the tropopause level, rapid temperature changes of more than 50 K/h at an ascent rate of 5 m/s and possible impacts of liquid and iced cloud droplets on the observations need to be handled. This requires adjustments to the acquisition of measured values and a careful selection of the launch time.
At Lindenberg Meteorological Observatory (52.21° north, 14.12° east) of the German Weather Service, a total of 68 all-season sounding flights have been carried out since April 2015 with modified radiosondes of the Meteolabor SRS-C34 and SRS-C50 type with added upward and downward solar and terrestrial radiation.
This presentation is discussing and interpreting the observational results of individual cloudless cases as well as soundings passing low, medium and high clouds. The downward fluxes are significantly modified below the tropopause. On the other hand, reflected radiation and terrestrial radiation are not only subject to local changes, even up to an altitude of 34 km, which can be quantified by including data on land use and cloud cover.
In addition, we will show the result of a case study where the radiative fluxes observed in and around clouds are used to validate corresponding numerical simulations performed with the ICON-ART model.
How to cite: Becker, R., Wacker, S., Doppler, L., Filipitsch, F., and Philipona, R.: In situ observation of radiative fluxes from surface to lower stratosphere, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-406, https://doi.org/10.5194/ems2022-406, 2022.
The Arctic shows an increased climate warming rate. There still exist uncertainties around the role that cloud feedback mechanisms play in this. In our study, we want to address these uncertainties. For that, we created a semi operational setup with daily cloud-resolving simulations over Svalbard. For these simulations with 600 m resolution, we use the ICOsahedral Non-hydrostatic model in the large eddy mode (ICON-LEM). The setup uses a two-moment microphysical parameterization and can handle heterogeneous surfaces. We apply the operational forecasts from the global ICON model as lateral boundary conditions. The advantage of this setup is that we can step away from focussing on single cases and instead look at many different types of large scale and local conditions.
We created and evaluated several months of these simulations using observations from Ny-Ålesund (Svalbard) for comparison. The supersite “AWIPEV” is located there. It includes a microwave radiometer, daily radiosondes, a rain gauge and other remote sensing instruments. In addition, we were able to use the Cloudnet data set that provides a classification of the hydrometeors. We found that the model captures general features such as the wind flow, integrated water vapour, temperature and relative humidity profiles very well. The cloud occurrence was overestimated by the model but still lies in a climatologically realistic range.
As the large scale dynamics are accurately simulated, this gives us the foundation to scrutinize the details of the cloud microphysical parameterization. As the next step, we investigate the shortcomings we could see in greater detail. One example is the more efficient production of cloud ice in the model than what was observed. For the analysis of specific microphysical processes, we are working on a software package which should enable the independent running of certain microphysical processes. This will make entangling the contributions of each process simpler and clearer while saving computational resources. Further, we show that for the Arctic, we must consider that standard nuclei concentrations, as used in models developed for the mid-latitudes do not represent the Arctic state. The goal in the long term is to improve the microphysical parameterization so that the model can better represent Arctic mixed-phase clouds.
How to cite: Kiszler, T., Ebell, K., Chellini, G., Kneifel, S., and Schemann, V.: Investigating the representation of microphysical processes in Arctic mixed-phase clouds in ICON-LEM, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-542, https://doi.org/10.5194/ems2022-542, 2022.
In the past years different methods have been developed to infer cloud cover from radiation data. Since surface cloud observations are scarce in Antarctica but broadband radiation instruments are more common and widespread, such methods could be very useful to reconstruct information whenever and wherever radiation measurements are available. The present work is centred on data from Marambio (64°14’50.6’’S - 56°37’39.3’’W) and Professor Julio Escudero (62°12’57’’S - 58°57’35’’W) stations, which are situated on opposite sides of the Antarctic Peninsula, respectively on Seymour and King George islands. At Marambio, from July 2019, a SPN1 (DeltaT Devices) sunshine pyranometer provides global shortwave and diffuse radiation data, and a NR01 (Hukseflux) net radiometer measures, for both shortwave and longwave radiation, the upward and downward components. At Escudero, both shortwave and longwave downward radiation observations are made, respectively, by a SMP21/22 pyranometer (from December 2016) and a SGR4 pyrgeometer (from December 2017), both by Kipp&Zonen, although with some interruptions in winter. Quality check of the data sets is made, when possible, applying the tests recommended by the Baseline Surface Radiation Network, even if the stations are not part of it. The control procedure shows a good quality of the measurements: generally, and for most variables, over 99% of the data pass the physically possible and extremely rare limits tests. At Marambio, in the worst case, 6% of the data fail the tests, whereas for Escudero only 2%. A first analysis of the radiation data does not show unusual results but it is noteworthy that, despite the lower solar elevation angles, irradiance is comparable to that of mid-latitudes, thanks to the greater transparency of the atmosphere in the Antarctic region. To infer cloud cover and estimate its effect on radiation measurements, two methods are chosen, each exploiting a particular broadband radiation component. The first is the Long et al.[1] method, which exploits measured shortwave downward and diffuse radiation components; the second is APCADA[2], based on longwave downward radiation measurements. Alongside them, meteorological parameters are also required and they are provided by the respective national meteorological services. As both sites are located in the peninsula, frequent cloudy sky conditions are expected from the results, which will depend on the performance of the methods in a peculiar environment such as Antarctica, different for solar elevation, humidity and surface cover from where the methods were developed and mainly tested.
Bibliography
[1] Long C. N., Ackerman T. P., Gaustad K. L., and Cole J. N. S. (2006): Estimation of fractional sky cover from broadband shortwave radiometer measurements, J. Geophys. Res., 111, doi: 10.1029/2005JD006475
[2] Dürr B. and Philipona R. (2004): Automatic cloud amount detection by surface longwave downward radiation measurements, J. Geophys. Res., 109, doi.org/10.1029/2003JD004182
How to cite: Frangipani, C., Lupi, A., Vitale, V., Ochoa, H. A., Gulisano, A. M., Rowe, P., and Cordero, R.: Broadband radiation data in the Antarctic Peninsula and estimation of cloud cover from two different methods, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-451, https://doi.org/10.5194/ems2022-451, 2022.
The Arctic region is showing the most intense warming of the globe, because of different regional feedback mechanisms. Both observed and projected warming rates reach a maximum in the autumn and winter seasons (Bintanja and Krikken, 2016), when the Arctic surface energy budget is dominated by longwave radiation. Indeed, due to the seasonal variation of the of shortwave radiation, the longwave radiation plays a key role in the Arctic, where the annual total Downward Longwave Irradiance (DLI) is usually more than twice as large as the annual downward shortwave irradiance. Nevertheless, surface longwave irradiance measurements in the Arctic are particularly scarce, and satellite retrievals of surface radiation budget based on satellite data are notoriously problematic at high latitudes.
High resolution observations of DLI, surface temperature, water vapour surface partial pressure and column amount, zenith sky IR radiance and vertical temperature profile derived by a microwave radiometer are routinely carried out at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5 N, 68.8 W), in North Eastern Greenland (https://ofcsg2dvf1.dwd.de/fmlurlsvc/?fewReq=:B:JVs5MjYzOSV1PjEtMyVqZz4zMjkzMiVwamRtYnd2cWY+MTVnMjJiYmU6ZztgZ2dlYDBiNWVnO2U1NjtiNmE6OjtgNTcwNGBnMSV3PjI1NjEzOjI2NTslcmpnPjE3OkJJUDtOMzI1NDM3LjE3OkJJUDtNMzI1NDM3JXFgc3c+UHdmZWJtLVRiYGhmcUNndGctZ2YlYD43OiVrZ28+Mw==&url=https%3a%2f%2fwww.thuleatmos-it.it%2f ). In the frame of the CLouds And Radiation in the Arctic and Antarctica (CLARA2) project, a celiometer has been installed in November 2019 with the aim of strengthening the cloud observational capability at the Observatory already including, among the other instruments, upward- and downward-looking pyranometers and pyrgeometers operating at THAAO since July 2016.
Preliminary statistical results for cloud base altitude, cloud depth, liquid water path (LWP), temperature profiles and presence/intensity of temperature inversion at THAAO will be shown. Analysis on the relationship between LWP and IR downward irradiance and radiance in cloudy and clear sky is also presented.
References
Bintanja, R., Krikken, F. Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing. Sci Rep 6, 38287 (2016). https://ofcsg2dvf1.dwd.de/fmlurlsvc/?fewReq=:B:JVs5MjYzOSV1PjEtMyVqZz4zMjkzMiVwamRtYnd2cWY+MjRnOzY0ZjQ3Ojc1ZTAwNDM2NWAxYjE1NTVmNzo3N2YwYDAyNDRnMyV3PjI1NjEzOjI2NTslcmpnPjE3OkJJUDtOMzI1NDM3LjE3OkJJUDtNMzI1NDM3JXFgc3c+UHdmZWJtLVRiYGhmcUNndGctZ2YlYD42MSVrZ28+Mw==&url=https%3a%2f%2fdoi.org%2f10.1038%2fsrep38287
How to cite: Pace, G., Di Iorio, T., Di Sarra, A., Iaccarino, A., Meloni, D., Muscari, G., Cacciani, M., Cimini, D., Larosa, S., and Romano, F.: Preliminary results from the CLouds And Radiation in the Arctic and Antarctica (CLARA2) project, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-711, https://doi.org/10.5194/ems2022-711, 2022.
