How to cite: Schmidt, L. and Hohenegger, C.: OCELAND: A Conceptual Model to Explain the Partitioning of Precipitation between Land and Ocean , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2709, https://doi.org/10.5194/egusphere-egu22-2709, 2022.

Land cover and land management changes (LCLMC) have often been highlighted as crucial regarding climate change mitigation (e.g., enhanced carbon uptake on land through afforestation), but their potential for adaptation has also been suggested (e.g., local cooling through irrigation). Regarding the latter, the effects of LCLMC on the climate remain uncertain. LCLMC can have strong implications on surface moisture fluxes and have even been linked to changes in large scale atmospheric circulation. Here, we study the effects of three LCLMC (i) global afforestation, (ii) global cropland expansion and (iii) large-scale irrigation extension on climate by employing three fully coupled Earth System Models (CESM, MPI-ESM, and EC-EARTH). Sensitivity simulations were performed under present-day conditions and extreme LCLMC, of which the effects on moisture fluxes and atmospheric circulation are investigated. We do this by first analyzing the surface moisture fluxes using monthly precipitation and evaporation data to perform a moisture convergence analysis, before performing a moisture tracking analysis with the Water Accounting Model (WAM-2 layers) , this model solves the atmospheric moisture balance and requires sub-daily data from the sensitivity experiments as an input.

Here we focus on the results from CESM, cropland expansion has shown to cause an average shift southward of the Intertropical convergence zone as well as a weakening in westerlies strength and consequent decrease in moisture transport. This causes an increase in continental moisture sources over most of the Northern Hemisphere. Afforestation, in contrast, shows an average shift northward of the Intertropical convergence zone and enhanced westerlies and moisture transport. Lastly, irrigation expansion enhances the moisture convergence over areas where irrigation is applied, causing an increase in both precipitation and evapotranspiration.

How to cite: De Hertog, S., Lopez Fabara, C. E., Havermann, F., Guo, S., Pongratz, J., Manola, I., Luo, F., Coumou, D., Davin, E. L., Seneviratne, S. I., Lejeune, Q., Schleussner, C.-F., and Thiery, W.: Sensitivity of global surface moisture dynamics under changed land cover and land management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-412, https://doi.org/10.5194/egusphere-egu22-412, 2022.

Land cover alteration due to anthropogenic activities modify land surface properties in absorbing, reflecting and emitting radiation as well as infiltrating, evaporating and storing water. This consequently modifies surface energy and water fluxes and, thus, climatic conditions. Progressive surface sealing results in higher runoff rates, less groundwater recharge, inhibited diurnal evaporative cooling and increased substrate heat storage, leading to augmented heat exchange by convection and, consequently, to an intensification of urban heat. We have identified a profound and robust relationship between the individual fluxes of the surface energy balance. From this, we derived an index including decisive aspects of land-atmosphere interactions and its feedbacks for assessment of the implication of surfaces to the climate system. The Surface Thermal Contribution Index (STCI) is intuitive to understand and can be calculated directly from Normalised Difference Vegetation Index (NDVI), from climate models or using data from on-site measurements. We provide a comprehensive framework to measure ecological and human systems responses to changes in land-atmosphere interactions and resulting feedbacks under global warming as well as critical malfunctions related to environmental and human well-being. Here, we use the index to map the partitioning of surface energy and water fluxes and assess surface thermal contribution at global to intra-urban microscale. Our results show that increasing global land evapotranspiration from 1999 to 2020, visible through a higher proportion of latent heat fluxes, is primarily observable in forested and irrigated regions and dominant on the northern hemisphere. Regional aridity, visible through a higher proportion of sensible and substrate heat fluxes, in combination with the 2019 European heatwave inhibited diurnal intra-urban evaporative cooling indicating that current urban adaptation measures cannot cope with decreasing water availability. Results confirm the hypotheses that land evapotranspiration should increase in a warming climate accompanied by increasing land aridity, amplified by land-atmosphere feedbacks, and thus reaffirm an intensification of the global water cycle. Although increasing latent heat fluxes favour surface cooling, land-atmosphere feedbacks lead to a decrease in surface water availability with increasing evapotranspiration, due to an acceleration in the transfer of water into the atmosphere. Global warming intensifies the global water cycle and increases the water holding capacity of the atmosphere as defined by the Clausius-Clapeyron relation. This further decreases surface water availability. The combination of increasing temperatures, land aridity and frequency of extreme heat events deteriorates urban vegetation health, diminishes the evaporative cooling effect and eventually leads to degradation of urban ecosystems. We conclude that green infrastructure interventions to reduce urban heat will not cope with future consequences, by means of regional water scarcity, if not irrigated extensively, which in turn will increase the pressure on local water resources and global water challenges. We stress the importance of restoring natural surface energy and water balances for climate-sensitive development. With global cities projected to shift to warmer and drier conditions, increasing resilience requires more comprehensive urban water management that sustainably provides sufficient water availability to avoid fatalities of ecological and human systems and maintain the evapotranspiration-driven cooling effect for successful urban heat mitigation.

How to cite: Back, Y., Bach, P., Jasper-Tönnies, A., Rauch, W., and Kleidorfer, M.: Mapping ecological and human systems responses to land-atmosphere interactions altered by climate change , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3411, https://doi.org/10.5194/egusphere-egu22-3411, 2022.

Land-use changes in the Amazon affect precipitation patterns, as the forest enhances precipitation levels regionally due to tree transpiration. However, it remains unclear to what extent such changes can influence precipitation. Recent studies used hydrological and atmospheric models to estimate the contribution of tree transpiration to precipitation but assumed that precipitation decreases proportionally to the transpired portion of atmospheric moisture. Here, we relaxed this assumption by, first, relating observed hourly precipitation levels to atmospheric column water vapor in a relatively flat study area encompassing a large part of the Amazon. We found that the effect of column water vapor on hourly precipitation was strongly nonlinear, showing a steep increase in precipitation above a column water vapor content of around 60 mm. Next, we used published atmospheric trajectories of moisture from tree transpiration across the whole Amazon to estimate the transpiration component in column water vapor in our study area. Finally, we estimated precipitation reductions for column water vapor levels without this transpired moisture, given the nonlinear relationship we found. Although loss of tree transpiration from the Amazon causes a 13% drop in column water vapor, we found that it could result in a 55%–70% decrease in precipitation annually. Consequences of this nonlinearity might be twofold: although the effects of deforestation may be underestimated, it also implies that forest restoration may be more effective for precipitation enhancement than previously assumed.

How to cite: Baudena, M., Tuinenburg, O. A., Ferdinand, P. A., and Staal, A.: Effects of land-use change in the Amazon on precipitation are likely underestimated, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5410, https://doi.org/10.5194/egusphere-egu22-5410, 2022.

Soil moisture plays a crucial role in partitioning surface fluxes. Several studies in past have highlighted the role of soil moisture in Land-Atmosphere (L-A) interactions. Understanding such interactions through regional climate models helps improve the simulation of global and regional hydrological processes. On the contrary, shallow subsurface groundwater also affects soil moisture variations. This calls for an accurate representation of physical processes involved in soil moisture interactions with groundwater. In addition, Shallow groundwater is known to act as a source and sink to the overlying soil layer during dry and wet seasons respectively. In this study, we analyze the impact of two different groundwater models in the Weather Research and Forecast (WRF) model coupled with the Noah-MP land surface model over the Ganga basin, India. Two experiments were carried out, one with the default-free drainage approach (CTL) and another with Miguez-Macho groundwater model (GW). The period of study was between 2008-2014. Preliminary analysis revealed that GW simulations improved soil moisture for the top and bottom-most soil layers. Reduction in temporal dry bias by around 91mm was observed for precipitation during the monsoon season. Dry bias in latent heat flux over the region also improved by 28 W/m². GW run improved soil moisture and precipitation representation compared to CTL run. In summary, our results advocate the need for a better representation of groundwater within coupled regional climate models for improved simulation of hydrological processes

How to cite: Huggannavar, V. and Jayaluxmi, I.: Ground Water Effects on Soil Moisture and Regional Climate using WRF-NoahMP Model Over Ganga Basin, India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10113, https://doi.org/10.5194/egusphere-egu22-10113, 2022.

Water use efficiency (WUE) is an important indicator of carbon and water cycles in terrestrial ecosystems. However, little is known about differences in water use efficiency at the leaf scale (WUE_Leaf) and ecosystem-scale (WUE_ECO) and response to environmental variables, particularly in plateau ecosystems with gradient effects. We obtained leaf carbon isotope data and calculated leaf-scale water use efficiency on the Qinghai-Tibet Plateau through field surveys and literature collection and calculated ecosystem-scale water use efficiency based on remote sensing data (MODIS). The study analyzed the differences between leaf-scale WUE and ecosystem-scale WUE in terms of vegetation type and spatial distribution and explored the response of water use efficiency to changes in environmental factors at both scales. The results found that the two water use efficiency scales showed different vegetation type trends and spatial distribution. At the leaf scale, WUE_Leaf showed grasses (10.91 mmol/mol) > trees (9.55 mmol/mol) > shrubs (8.34 mmol/mol), and spatially as a whole showed higher in the western high altitudes (Grasses) than in the low eastern altitudes (Trees). In contrast, at the ecosystem scale, WUE_Eco shows trees (1.17 g C/kg H2O) > shrubs (1.05 g C/kg H2O) > grasses (0.53 g C/kg H2O), while at the spatial scale, the eastern low elevation region (Forests) is greater than the western high elevation region (Grasslands). Climate (MAT) and vegetation (EVI) factors are the most important environmental variables affecting the variation of WUE at leaf and ecosystem scales, respectively, on the Tibetan plateau. The effect of altitude on water use efficiency is not caused by the vegetation type, although the WUE varies among vegetation types. Conversely, the effect of elevation is influenced by the interaction between environmental conditions and vegetation. These results suggest that the appropriate water use efficiency scale should be selected for specific purposes in carbon and water cycle studies. When the focus is on the influence of climate on the carbon-water cycle, leaf-scale water use efficiency is more appropriate, while if the effect of vegetation, ecosystem-scale water use efficiency would be more appropriate.

How to cite: Wang, X., Chen, G., Wu, M., Li, X., Wu, Q., Wang, P., Zeng, H., Yang, R., and Tang, X.: Mechanistic differences of leaf and ecosystem-scale water use efficiencies on the Qinghai-Tibet Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-634, https://doi.org/10.5194/egusphere-egu22-634, 2022.

Central Asia is a semiarid to arid region that is sensitive to hydrological changes. We use the Community Atmosphere Model, version 5 (CAM5), equipped with a water-tagging capability, to investigate the major moisture sources for climatological precipitation and its long-term trends over central Asia. Europe, the North Atlantic Ocean, and local evaporation, which explain 33.2% ± 1.5%, 23.0% ± 2.5%, and 19.4% ± 2.2% of the precipitation, respectively, are identified as the most dominant moisture sources for northern central Asia (NCA). For precipitation over southern central Asia (SCA), Europe, the North Atlantic, and local evaporation contribute 25.4% ± 2.7%, 18.0% ± 1.7%, and 14.7% ± 1.9%, respectively. In addition, the contributions of South Asia (8.6% ± 1.7%) and the Indian Ocean (9.5% ± 2.0%) are also substantial for SCA. Modulated by the seasonal meridional shift in the subtropical westerly jet, moisture originating from the low and midlatitudes is important in winter, spring, and autumn, whereas northern Europe contributes more to summer precipitation. We also explain the observed drying trends over southeastern central Asia in spring and over NCA in summer during 1956–2005. The drying trend over southeastern central Asia in spring is mainly due to the decrease in local evaporation and weakened moisture fluxes from the Arabian Peninsula and Arabian Sea associated with the warming of the western Pacific Ocean. The drying trend over NCA in summer can be attributed to a decrease in local evaporation and reduced moisture from northern Europe that is due to the southward shift of the subtropical westerly jet.

How to cite: Jiang, J.: Tracking moisture sources of precipitation over Central Asia: A study based on the water-source-tagging method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6735, https://doi.org/10.5194/egusphere-egu22-6735, 2022.

From 1998 until now, the Chinese government has implemented numerous policies and programs, such as the Grain for Green Program, the Three-North Shelter Forest Program, and the Beijing-Tianjin Sand Control Program, to restore ecosystems and to improve environmental protection in the agro-pastoral ecotone of Northern China (APENC). However, it remains unclear how the large-scale vegetation restoration modulates the regional moisture cycle in the APENC. To fill this gap, we investigated the variations of observed precipitation and estimated evapotranspiration from 1995 to 2015. The evapotranspiration is estimated by the Priestley-Taylor Jet Propulsion Laboratory model with dynamic vegetation (DV). The precipitation recycling ratio calculated by the Dynamic Recycling Model is used to analyze the impacts of vegetation restoration on regional moisture recycling. Our results show that the precipitation and ET under the DV were significantly increased during the period of 1995-2015, with the increasing rate of 4.42 mm yr^-1 and 2.13 mm yr^-1, respectively. The precipitation recycling ratio was also significantly increased during the study period, showing positive feedback of vegetation restoration on precipitation. The atmospheric water budget analysis shows that vegetation restoration noticeably modifies the annual mean values of water transport terms in the regional water cycle, indicating an indirect effect on local precipitation. Our findings help better understand the impacts of land cover change on local water resources, which in turn supports local water resource management and decision making.

How to cite: Wang, X., Zhang, B., Zhang, Z., Kunstmann, H., and He, C.: Investigating impacts of large-scale vegetation restoration on water recycling processes in the agro-pastoral ecotone of Northern China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9371, https://doi.org/10.5194/egusphere-egu22-9371, 2022.

North-central Ukraine is vulnerable to temperature increases and precipitation pattern changes associated with climate change. With water management becoming increasingly important, information on current water sources and moisture recycling is critically needed. Isotope ratios of oxygen (δ¹⁸O) and hydrogen (δ²H) in precipitation are sensitive to these variables and allow comparisons across the region. For this study, precipitation was collected over a period of one year from Kyiv and Cherkasy and local meteoric water lines were created for both cities. The δ²H and δ¹⁸O values from collected precipitation and published ³H data for Kyiv from the year 2000 show an influence of the North Atlantic Oscillation (NAO) and provide information about processes affecting precipitation along the storm trajectory. The δ¹⁸O values also show correlation with temperature, indicating that precipitation patterns may be affected by the rising temperatures in the region, as predicted by recent regional studies using Representative Concentration Pathway scenarios and the global climate model GFDL-ESM2M. When compared to backtracked storm trajectory data, clear relationships emerged between water isotope ratios, storm paths, and likely moisture recycling. These results show that when isotopic data are used with backtracked storm trajectories and NAO cycles, a more complete idea of regional processes can be formed, including addition of water vapor from more localized sources. Overall, δ²H, δ¹⁸O, ³H, and backtracked storm trajectory data provide more regional and local information on water vapor processes, improving climate-change-driven precipitation forecasts in Ukraine.

How to cite: Avery, E., Samonina, O., Kryshtop, L., Vyshenska, I., Fryar, A. E., and Erhardt, A. M.: Use of Isotopes in Examining Precipitation Patterns in North-Central Ukraine, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6246, https://doi.org/10.5194/egusphere-egu22-6246, 2022.

Plants play a key role in the hydrological cycle, yet their contribution to extreme rainfall remains uncertain. Here we show that more than half of the vast amounts of water accumulated in the recent Germany and Belgium floods were supplied by vegetation (41% from transpiration, 11% from interception loss). We found that intercontinental transport of moisture from North American forests (which contributed more than 463 billion liters of water to the event) was a more important source than evaporation over nearby seas, such as the Mediterranean or the North Sea. Our results demonstrate that summer rainfall extremes in Europe may be strongly dependent on plant behavior and suggest that significant alterations in vegetation cover, even of remote regions, could have a direct effect on these potentially catastrophic events.

How to cite: Insua Costa, D., Senande Rivera, M., Miguez Macho, G., and Llasat Botija, M. C.: Vegetation fueled summer 2021 floods in Germany and Belgium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12711, https://doi.org/10.5194/egusphere-egu22-12711, 2022.

Land use changes are the major anthropogenic alterations which are considered to have an important impact on the climate system. In semiarid regions such as the the Southeastern Spain where water is the major limiting factor for ecosystems functioning and human development, knowledge about future water availability is of high importance above all in the context of climate change. To better understand the potential impact of land use change on the regional climate, we used the Weather Research and Forecasting (WRF) model to simulate the impact of different land use scenarios on precipitation in the Jucar Basin in Southeastern Spain. We conducted three different scenarios: (1) increasing the tree cover areas, (2) removing the tree cover and increasing the shrubland areas, and (3) increasing the urban areas in the coastal areas. Preliminary results show that increasing the tree cover areas will likely increase the annual precipitation (approximately +3%) in the region, and mostly affecting the autumn period (+8%) with respect to the actual land use scenario. Removing the tree cover and increasing the urban areas resulted in reduced precipitation above all during the spring season (-3%).

How to cite: Moutahir, H., Beneto, P., Arnault, J., Zhang, Z., Laux, P., Khodayar, S., and Kunstmann, H.: The impact of different land use change scenarios on precipitation in a semiarid Mediterranean area in Southeastern Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12789, https://doi.org/10.5194/egusphere-egu22-12789, 2022.

Climate and land are closely intertwined through multiple interface processes. On one hand, land endows means for agriculture practices and agroforestry systems thus contributing to the food and materials supply; on the other, climate change may lead to significant impacts in land use and efficient water availability and management. Therefore, the study of these interactions and the impact of the bioclimatic shifts, since land use, plays a relevant role in the climatic system is highly relevant.

Towards this aim, in this study, 1‒km observational gridded datasets are used to assess changes in the Köppen–Geiger and Worldwide Bioclimatic (WBCS) Classification Systems in mainland Portugal. As such, two past periods were analyzed: 1950–1979 and 1990–2019. A compound bioclimatic-shift exposure index (BSEI) is defined to identify the most exposed regions to recent climatic changes. The temporal evolution of land cover with vineyards between 1990 and 2018, as well as correlations with areas with bioclimatic shifts, are then analyzed.

Results show significant climatic changes between the two periods with an increase of 18.1% in the Warm Mediterranean with hot summer (CSa) climate in Portugal. This increase was followed by a 17.8% decrease in the Warm Mediterranean with warm summer (CSb) climate. Furthermore, the WBCS Temperate areas also reveal a decrease of 5.11%. Arid and semi-arid ombrotypes areas increased, whilst humid to sub-humid ombrotypes decreased. Thermotypic horizons depict a shift towards warmer classes. BSEI highlights the most significant shifts in northwestern Portugal.

Overall results show that vineyards have been displaced towards regions that are either the coolest/humid, in the northwest, or the warmest/driest, in the south. Since vineyards in southern Portugal are commonly irrigated, options for the intensification of these crops in this region may threaten the already scarce water resources and challenge the future sustainability of this sector. As similar problems can be found in other regions with Mediterranean-type climates, the main findings of this study can be easily extrapolated to other wine producer countries worldwide.

Acknowledgement: This work was supported by National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020.

Keywords: Köppen-Geiger Climate Classification, Worldwide Bioclimatic Classification System (WBCS), Vineyards, Portugal.

How to cite: Andrade, C., Fonseca, A., and A. Santos, J.: Land use options for Viticulture in Portugal in light of bioclimatic shifts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7400, https://doi.org/10.5194/egusphere-egu22-7400, 2022.