The Italian space industry, and specifically Leonardo S.p.A., has gained unique skills at an international level in the development of space-qualified power laser sources with for lidar Earth observation applications (Aeolus, EarthCARE). Moreover, Leonardo S.p.A. and the Italian optical industry, has a consolidated technical-scientific knowledge and consolidated experience in the design and development of lidar receiver sub-systems (telescopes, optical devices and sensors) with  space applications. The Italian Space Agency (ASI) intends to benefit from long-term expertise to design and develop a lidar system for Earth observation applications. Two separate feasibility studies, one focusing of technical aspects and one focusing on scientific aspects, are presently underway to define mission goals and a possible instrument layout.
CALIGOLA has a primary focus on the atmosphere, but also a strong focus on the study of the Ocean-Earth-Atmosphere system and the mutual interactions within it. Exploiting the three Nd: YAG laser emissions at 354.7, 532 and 1064 nm and the elastic (Rayleigh-Mie) and Raman lidar echoes from atmospheric constituents, CALIGOLA is conceived to carry out three-wavelength particle backscatter and depolarization ratio and two-wavelength particle extinction profile measurements from aerosols and clouds to be used to retrieve their microphysical and dimensional properties. Furthermore, measurement of the elastic backscattered echoes from the sea surface and the underlying layers, and their degree of depolarization, CALIGOLA will be exploited to characterize sea optical properties (ocean color) and the suspended particulate matter, which are needed to study the seasonal and inter-annual phytoplankton dynamics and to improve the understanding of the role of phytoplankton in marine biogeochemistry, in the global carbon cycle and in the response of marine ecosystems to climate variability. A specific measurement channel will be dedicated to fluorescence measurements from atmospheric aerosols and marine chlorophyll, for the purpose of aerosol typing and for characterizing ocean primary production. Aerosol fluorescence measurements at 680 nm/460 nm are also planned for the purpose of aerosol typing. CALIGULA will also allow accurate measurements of the small-scale variability of the earth's surface elevation primarily associated with variations in the terrain, vegetation and forest canopy height.
The CALIGOLA project is explicitly included the on-going Three-Year Activity Plan (2021-2023) of the Italian Space Agency, with a scheduled tentative launch window of 2026-2028. The considered strategy to develop the above described space lidar mission in such a short time relies on the maximum exploitation of subsystems already developed at national level for space applications, with a high TRL (TRL>7), ultimately leading to a space mission with high impact and scientific timeliness. The Phase A study of the technological feasibility of the laser source is on-going, commissioned by ASI to Leonardo S.p.A., and scientific studies in support of the mission also on-going, with the University of Basilicata being the leading scientific institution. The Italian Space Agency is willing to pursue this mission in a coordinated way with one or more other European or extra-European Space Agencies, with a bilateral or multi-lateral contributed mission approach, and, in this regard, any interest from other Agencies is welcome and desired.

How to cite: Di Girolamo, P., Cosentino, A., Longo, F., Franco, N., Dionisi, D., Summa, D., Lolli, S., Suetta, E., Perna, A., and Zoffoli, S.: Cloud Aerosol Lidar for Global Scale Observations of the Ocean-Land-Atmosphere System – CALIGOLA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5644, https://doi.org/10.5194/egusphere-egu22-5644, 2022.

The evolution of wind gusts is difficult to observe as gusts are short-lived and small-scale phenomena. They occur with certain weather configurations (e.g. fronts, cold pools) and may already differ very locally. The question arises if individual gust observations can be taken as representative of their surroundings or if significant differences can already be apparent on the meso-gamma scale (2-20 km). Within the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) different phenomena in the atmospheric boundary layer are studied with a variety of measurement instruments. This involved installing three StreamLine DWL systems from Halo Photonics at a distance of 6 km apart from each other. DWLs allow the retrieval of wind vector profiles and offer an alternative to classic meteorological tower observations, since they can be flexibly deployed at any electrified site. However, short-lived gusts are more difficult to capture than a persistent mean wind. A wind vector has to be obtained from different radial velocity measurements that are made sequentially, which limits the achievable temporal resolution. Therefore, we have developed a new retrieval method for deriving wind measurements that is suitable for different scan configurations and different time resolutions respectively different numbers of radial velocities. A fast continuous scanning mode (CSM), that completes a full observation cycle within 3.4 seconds and measures about eleven radial Doppler velocities is a suitable DWL configuration for deriving wind gusts, as shown by comparisons with measurements of a sonic anemometer at 90.3 m a.g.l. on the meteorological tower in Falkenberg. The fast CSM configuration was operated on the DWLs during the summer months 2021 at the three different sites. Their surrounding area is predominantly flat farmland, minimizing topographic impacts. This set-up allows us to observe the spatial-temporal evolution of gusts at the meso-gamma scale. Examples will be presented that illustrate the variability of wind gusts as observed during FESSTVaL.

How to cite: Steinheuer, J., Beyrich, F., Detring, C., Fiedler, S., Friederichs, P., and Löhnert, U.: Sub-mesoscale evolution of spatial wind gust patterns measured with three Doppler lidars in a triangle configuration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7336, https://doi.org/10.5194/egusphere-egu22-7336, 2022.

The atmospheric planetary boundary layer (ABL) represents the lower region of the atmosphere directly in contact with the earth's surface and strongly influenced by this surface. In this layer physical quantities such as flow velocity, temperature and humidity exhibit rapid fluctuations associated with turbulent motion and vertical mixing.

Characterization of the planetary boundary layer is of primary importance in a variety of fields such as weather forecasting, climate change modeling and air quality forecasting and therefore it is very important to determine it correctly. The structure of ABL can be complex and highly variable.  In this work different techniques to estimate the ABL height are compared. A first technique makes use of the pure rotational Raman lidar signals, which are strongly dependent on temperature. A second technique makes use of the  water vapor roto-vibrational Raman lidar signals in the lower troposphere. Further techniques based on the Morphological Image Processing Approach (MIPA) are also considered. In the present research work, we consider the measurements from the University of Basilicata Raman lidar system BASIL collected in the period 16-21 October 2012 in the frame of HyMex SOP1 [1,2,3].

References:

[1] Di Girolamo, P., R. Marchese, D. N. Whiteman, B. B. Demoz, Rotational Raman Lidar measurements of atmospheric temperature in the UV. Geophysical Research Letters, 31, L01106, ISSN: 0094-8276, doi: 10.1029/2003GL018342, 2004.

[2] Vivone, G., D'Amico G., Summa D., Lolli S., Amodeo A., Bortoli D., and Pappalardo G.. Atmospheric boundary layer height estimation from aerosol lidar: a new approach based on morphological image processing techniques Atmos. Chem. Phys., 21, 4249–4265, 2021 https://doi.org/10.5194/acp-21-4249-2021.

[3] Summa, D., P. Di Girolamo, D. Stelitano, and M. Cacciani, Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches, Atmos. Meas. Tech., 6, 3515–3525, 2013, www.atmos-meas-tech.net/6/3515/2013/doi:10.5194/amt-6-3515-2013

How to cite: Summa, D., Di Girolamo, P., Vivone, G., Franco, N., Giuseppe, D., and De Rosa, B.: ABL determination by Raman lidar with different approaches in the frame of HyMeX SOP1, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7792, https://doi.org/10.5194/egusphere-egu22-7792, 2022.

Aviation affects the Earth’s radiation budget through a combination of multiply processes which warm the atmosphere. Linear contrails and contrail cirrus induced by water vapor and soot emissions from air traffic in the upper atmosphere are expected to contribute a large part of the climate impact of avation. Furthermore, contrails cause a significant increase in cirrus optical thickness as well as an indirect effect on the microphysical properties of naturally formed cirrus clouds. During the first lockdown in April 2020, air traffic over Europe was significantly reduced to about 80% compared to the year before. This unique situation provides a good opportunity to study the effect of air traffic on cirrus. Based on the analysis of the spaceborne lidar measurements with CALIPSO, we found a significant reduction in the particle linear depolarization ratio (PLDR) of cirrus clouds measured in April 2020 compared to the previous years 2014-2019 under normal conditions, especially at colder temperatuers (T < -50^oC). However, we note that civil aviation over Europe before the COVID-19 pandemic (i.e., before March 2020) grew strongly in terms of CO2 emission and flight densities, e.g. on average by 233 MTon/year over Germany, over the past years (2010-2019, especially 2013-2019, source: EUROCONTROL). In order to study the aviation effects of cirrus properties in a longer period (with, of course, milder change in air traffic than the case due to the COVID lockdown), we further extend our analysis to all the observations from Mar. 2010 to Feb. 2020. We found a long-term trend of 0,0087/year (~2.4% per year) in PLDR for all the cirrus observations (day+night) and a trend of 0.0107/year for only the day-time observations at altitudes between 6 and 13 km. In addition, seasonal variations of PLDR are also drived showing higher PLDR-values in winter than in summer for all the measurements as well as for the measurements in different altitude bins. In the end, we compared the background meteorological conditions including the ambient temperature, relative humidity, and vertical updrafts determined with ECMWF and analyzed the correlation between PLDR and the corresponding CO2 emissions as a proxy of air traffic densities.

Key words: CALIPSO; Cirrus cloud; Lidar; Depolarization ratio; PLDR; COVID-19

How to cite: Li, Q. and Groß, S.: Aviation-induced changes in cirrus clouds over Europe during COVID-19 and in a ten-year period before COVID-19 , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9144, https://doi.org/10.5194/egusphere-egu22-9144, 2022.

The Atmospheric Thermodynamic LidAr in Space (ATLAS) is a mission concept proposed to the European Space Agency in the frame of “Earth Explorer-11 Mission Ideas” Call by a team of researchers, with the aim to develop the first Raman Lidar in space capable to measure simultaneously atmospheric temperature and water vapour mixing ratio profiles with high temporal and spatial resolutions. Accurate measurements of these profiles are essential to understand water and energy cycles, as well as the prediction of extreme events, that nowadays still show huge deficiencies on all temporal and spatial scales (1). Such measurements would have a revolutionary impact on our understanding of the Earth system and would close the gap in our observational capabilities from the surface to the lower troposphere.

The specifications of the different lidar sub-system, as well as the expected capability to provide measurements with high temporal and spatial resolution in the low and middle troposphere, have already been established with an analytical simulation model (2,3). These simulations considered different atmospheric models and conditions to estimate the statistical uncertainty on water vapour and temperature measurements. New studies have been now performed to estimate the performances along several dawn-dusk orbits. An end-to-end simulator has been developed and used to estimate the statistical and systematic uncertainties. The input data, comprehensive of thermodynamic and optical parameters, have been extracted from the GEOS-5 Nature Run and have been chosen to perform simulations with different solar zenith angles and therefore different background contributions. The model includes information on cloud fraction and optical thickness, so it was also possible to consider the performances in cloudy conditions. The simulations show promising results, both in clear and cloudy conditions and with different background contributions. A comprehensive study of the assessed performances will be presented at the conference.

The simulated measurements obtained from the simulator will be also used as input observations in the Weather Research and Forecasting model (WRF). The aim is to estimate the impact of global measurements from a space-borne Raman Lidar in terms of skill-scores, obtained by the comparison of the weather forecast output with and without the assimilation of the simulated lidar data.

1 - Wulfmeyer, Hardesty, Turner, Behrendt, Cadeddu, Di Girolamo, et al. A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles. Reviews of Geophysics. 2015; 53(3):819–95.

2 - Di Girolamo, Behrendt, Wulfmeyer. Space-borne profiling of atmospheric thermodynamic variables with Raman lidar: performance simulations. Opt Express,OE. 2 aprile 2018; 26(7):8125–61.

3 - Di Girolamo, Behrendt, Wulfmeyer. Spaceborne profiling of atmospheric temperature and particle extinction with pure rotational Raman lidar and of relative humidity in combination with differential absorption lidar: performance simulations. Appl Opt, AO. 10 aprile 2006; 45(11):2474–94.

How to cite: Franco, N., Di Girolamo, P., Summa, D., De Rosa, B., Behrendt, A., and Wulfmeyer, V.: Performance assessment of the space-borne Raman Lidar ATLAS – Atmospheric Thermodynamic LidAr in Space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11817, https://doi.org/10.5194/egusphere-egu22-11817, 2022.

The Lidar Emitter and Multispecies greenhouse gases Observation iNstrument (LEMON) objective is the development and test of a new Differential Absorption Lidar (DIAL) sensor concept for greenhouse gases and water vapor for spaceborne, airborne or ground-based measurements. The innovative instrument is based on a versatile transmitter. The concept of the measurement was recently preliminarily tested for water vapor in a co-dedicated field campaign from 13 to 24 September 2021 over the Aubenas airfield (France, 44° 32' N 4° 22' E). This campaign was also an opportunity to test different approaches for the measurement of the vertical water vapor profile using classical meteorological probes embarked on meteorological balloons and on an airplane, a vibrational Raman lidar WALI (Weather Atmospheric LIdar), a cavity ring-down spectrometer (CRDS) and of course a first version of the LEMON lidar named WaVIL (Water Vapor and Isotope Lidar). The field campaign involved an instrumented van with two lidars and three ULAs carrying various payloads: a backscatter Rayleigh-Mie lidar to identify atmospheric structures from the local to regional scales, a CRDS for water vapor isotope measurements and in situ samplers to characterize cloud-related forcing on atmospheric water vapor concentrations. The measurement strategy adopted made it possible to follow the evaporation of water vapor throughout the course of a thunderstorm and to sample an intrusion of dry air from high altitudes. It also provided initial answers as to the potential of the WaViL instrument for measuring the main isotope of water vapor and its secondary isotope HDO. The measurement campaign will be presented, as well as the first associated results.

How to cite: Hamperl, J., Chazette, P., Totems, J., Dherbecourt, J.-B., Melkonian, J.-M., Nicolas, P., Raybaut, M., Clémençon, A., Geyskens, N., Geneau, P., Flamant, C., Zannoni, D., Sodemann, H., Steen-Larsen, H. C., Monod, A., Durand, A., Ravier, S., and Schwarzenboeck, A.: Demonstration of water vapor and Isotopes measurement from lidar using a multi-platform, multi-instrumental approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12076, https://doi.org/10.5194/egusphere-egu22-12076, 2022.

The Aeolus mission offers unique opportunities for lidar surface returns (LSR) applications considering its incidence angle (~37.5^o) and the operated wavelength (~355 nm). Previous Aeolus-oriented studies have indicated that the contrast between LSR over dark and bright surfaces is expected to be particularly pronounced at 355 nm. We evaluated this surmise by comparing new LSR estimates from novel Aeolus prototype processor (using an optimal estimation approach) with various types of land for the Intensive Observation Period of Aeolus (September 2019) and an additional period during the same year. We discerned a very clear LSR gradient between the signal from water (mostly weak, but variable) and the signal from land (mostly strong), whereas the strongest LSR was found over white surfaces (ice or snow). Moreover, the sensitivity of LSR to the type of surface was also identified as the gradient between the brightest surfaces (snow/ice, sparse vegetation) and the dark surfaces (herbaceous forest, mangrove, wetland) was significant. Specifically, besides Antarctica and Greenland, the strongest returns over land were reported over the snow-covered areas of Tibet and Andes, followed by the arid areas of Northern America, Northern Africa and Middle East. Notably, the LSR from water was not always low as the average LSR estimate over water exhibited the strongest variability (~0.001 – 0.042 sr^-1) and yielded most statistical outliers. The application of sea ice mask from MERRA-2 model revealed that most strong LSR cases over water were associated with the undetected ice. The masking of detected ice has resulted in the dramatic reduction of the average LSR over water. As a result, the related LSR variability over water was dwindled by the factor of ~10 down to ~0.001 – 0.004 sr^-1 and >95% of outliers disappeared. Our findings about the sensitivity of Aeolus surface returns to the type of surface are beneficial because statistically robust LSR estimates over ocean lay the foundation for the Aeolus LSR-based Aerosol Optical Depth (AOD) retrieval over ocean. This retrieval can be established based on the fundamental link between LSR, near-surface wind speed and AOD over sea surface.

How to cite: Labzovskii, L., van Zadelhoff, G.-J., Donovan, D., De Kloe, J., and Josset, D.: How sensitive are Aeolus Lidar Surface Returns (LSR) to the types of surface? Insights for LSR-based retrieval of AOD over ocean by using Aeolus., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12079, https://doi.org/10.5194/egusphere-egu22-12079, 2022.