Irrigation significantly impacts climate across local, regional, and remote scales. This critical agricultural practice transforms local land surface properties, leading to increased soil moisture and consequent changes in the surface energy balance. Such changes typically result in cooler local surface temperatures due to higher latent heat flux from enhanced evapotranspiration. Beyond its local effects, irrigation substantially influences regional climate and hydrology. The introduction of additional moisture into the atmosphere from irrigated areas can alter regional atmospheric dynamics, potentially affecting cloud formation and modifying precipitation patterns. While irrigation practices can be beneficial for agriculture, they may also have unintended consequences on regional climates, including altering rainfall distribution. Furthermore, the implications of irrigation can extend to remote climate systems. Irrigation-induced redistribution of heat and moisture can influence atmospheric circulation patterns and atmospheric wave dynamics, impacting hydroclimate far beyond the immediate area of irrigation. These remote effects underscore the interconnected nature of global climate systems and the extensive impact of localized human activities like irrigation.

In sum, irrigation exerts a cascading influence on climate systems at various scales. It reshapes local surface conditions, drives changes in regional atmospheric processes, and has potential implications for remote climates. Comprehending these complex interactions is crucial for formulating sustainable irrigation strategies and addressing the broader climatic impacts of such practices.

How to cite: Lo, M.-H. and Chen, H.-C.: Impacts of irrigation on local, regional, and remote climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1607, https://doi.org/10.5194/egusphere-egu24-1607, 2024.

Precipitation recycling, characterized by the contribution of local evapotranspiration (ET) to local precipitation, is a critical component of the
regional water cycle. In the US Corn Belt, vast croplands and irrigation applications have markedly modified surface energy and water balance, which in
turn modulates precipitation recycling. However, previous studies often neglected the complex hydrological and crop physiological processes at land surface with an oversimplified assumption. In this study, we aim to understand the precipitation recycling in the US Corn Belt with explicit shallow groundwater dynamics, crop growth, and irrigation processes in the WRF model, with the water vapor tracer (WVT) capability to track ET directly from croplands. We found that the croplands exhibit a strong cooling effect on air temperatures and increasing summer precipitation. The increase in precipitation can be attributed to enhanced precipitation recycling, ranging from 11 to 22%, and much stronger seasonality during summer growing seasons. Such cooling effect and contribution to precipitation recycling is more significant in a drought year compared to normal and wet years, depending on both large-scale moisture advection and local moisture source. Our results have important implications to modeling ecohydrology and agricultural management in the Earth system, understanding precipitation recycling in the entire water cycle and designing sustainable water resource governance.

How to cite: Zhang, Z., He, C., Chen, F., Miguez-Macho, G., Liu, C., and Rasmussen, R.: US Corn Belt enhances regional precipitation recycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1391, https://doi.org/10.5194/egusphere-egu24-1391, 2024.

The Three Gorges Dam (TGD), as the largest hydropower project, resulting in increasing water area from 408km² to 1084km² and extending waterway into 660 km. It is obvious that land use change would influence regional precipitation, but affected region owing to the TGD is on dispute. Moreover, the highest resolution of previous studies is 1.5 km, however the width of artificial lake formed by the TGD is about 1.1 km. To this end, we address the need of a higher resolution of numerical simulation by running weather research and forecast (WRF) model with 3 two-way nested domains. Two simulations under different land use (with or without TGD) are compared. Results showed that regional precipitation is suppressed owing to TGD to some extent. More precisely, increasing precipitation happens in downwind region, whereas decreasing precipitation occurs upwind region. Besides, water surface expansion leads to a reduction in surface temperature within 0~5 km of surrounding area. The TGD construction increase specific humidity and surface within 5 km buffer. That is because water surface expansion results in moisture surplus in nearby region.

How to cite: Peng, P., Zhang, Y., and Di, X.: Impacts of the Three Gorges Dam on regional precipitation: based on high resolution simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17252, https://doi.org/10.5194/egusphere-egu24-17252, 2024.

Irrigation is an anthropogenic forcing to the Earth-system that alters the water and heat budgets at the land surface, leading to changes in regional hydro-climate conditions over a range of spatiotemporal scales. These impacts of irrigation are anticipated to escalate in the future due to increased food demand and the pervasive effects of climate change. Thus, it is imperative to better understand the nature, extent, and mechanisms through which irrigation affects the Earth's system. However, despite its increasing importance, irrigation remains a relatively nascent component in the Earth-system modeling community, necessitating advancements in modeling and a deepened understanding.

Our research aims to improve the quantitative understanding of the impacts of irrigation and groundwater use as anthropogenic drivers on regional climate and environmental changes. To this end, we developed an improved Earth-system modeling framework that is based on MIROC-ES2L (Hajima et al 2020 GMD) coupled with hydrological human-activity modules (Yokohata et al. 2020 GMD). This model enables the simulation of a coupled natural-human interaction including hydrological dynamics associated with irrigation processes. Employing this Earth-system model, we carried out a numerical experiment in T85 spatial resolution, utilizing an AMIP style set-up. Here, our ensemble simulation allows for statistical quantification of the irrigation impact differentiating them from the uncertainties arising due to natural variability.

Through our investigation, we have identified specific regions and seasons where irrigation exerts a discernible influence on regional hydro-climate. Notably, our results show substantial disparities—larger than or comparable to inter-annual variability—between simulations incorporating and excluding the irrigation process, particularly in heavily irrigated regions such as Pakistan and India. Our model demonstrates that the introduction of moisture into the soil through irrigation alters the hydrological balance of the land surface, consequently influencing the overlying atmosphere. Conversely, we found significant uncertainty in the impact estimate for some regions, even those heavily irrigated, such as the central United States and eastern China, indicating the challenges of robustly estimating irrigation impacts with limited samples. This underscores the necessity for an appropriate statistical approach to evaluate the impact of irrigation, considering the inherent variability. Furthermore, our study delves into estimating regional variations in the contributions of groundwater and surface water use to these impacts. Emphasizing the importance of a more nuanced understanding of regional characteristics in irrigation impact assessments, our research underscores the significance of coupled earth system models in comprehending and predicting the intricate interplay between human activities and the Earth's climate system.

How to cite: Satoh, Y., Pokhrel, Y., Kim, H., and Yokohata, T.: Estimating the impact of irrigation and groundwater pumping on regional hydroclimate using an Earth System Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9778, https://doi.org/10.5194/egusphere-egu24-9778, 2024.

By 2030, over 300 million hectares worldwide will be irrigated, constituting the second most significant anthropogenic influence on land use following urbanisation. Our study focuses on an irrigated Terrestrial Environmental Observatories (TERENO)/Integrated Carbon Observation System (ICOS) site in Germany, unveiling irrigation's immediate effects on soil moisture, latent heat flux, skin and soil temperature. As we strive to seamlessly integrate irrigation processes into the ECMWF Integrated Forecasting System (IFS), our investigation extends to an offline model, ECLand, including dynamical vegetation. Introducing a perturbed precipitation field offers a refined perspective of mimicking irrigation. The feedback provides us with insights into the coupling of simple irrigation representation on thermodynamic variables, ensuring optimal benefits for the IFS. After verification with remote sensing data, the next step involves coupling water fluxes to stomatal conductance via photosynthesis, shedding light on the preliminary influence of irrigation on enhanced vegetation growth. This aims to untangle irrigation effects of increased soil moisture and greening. 

How to cite: Weber, K. M. F., Magnusson, L., Balsamo, G., Choulga, M., Boussetta, S., Pedruzo Bagazgoitia, X., and Arduini, G.: Irrigation impact on thermodynamics in weather forecast modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13419, https://doi.org/10.5194/egusphere-egu24-13419, 2024.

The recent years have shown increasing interest and effort to include simulation of irrigation in Earth System Models to better account for the effects of this anthropogenic process on climate. We present here preliminary results about the impacts of simulated irrigation on surface-atmosphere interactions using LMDZ and ORCHIDEE, the atmosphere and land surface components of the IPSL Climate Model. The DYNAMICO-LMDZ configuration, coupling the physics of LMDZ to the recent icosahedral dynamical core DYNAMICO, is run as a Limited Area Model (LAM) to conduct a regional study over North-Eastern Spain. The simulation domain encompasses the Ebro valley where the LIAISE (Land-surface Interactions with the Atmosphere In Semi-Arid Environment) field campaign was conducted in 2021. This campaign was specifically designed to provide better understanding of the local and regional impacts of irrigation and the surface heterogeneities it creates. A new representation of irrigation, based on a soil moisture deficit approach, has recently been developed in ORCHIDEE and simulations are run with and without it to assess the impacts of simulated irrigation in the model. Direct effects at the land-surface interface (soil moisture, turbulent fluxes, temperature) are studied first, before focusing on the structure of the boundary layer and precipitations. Field observations from the campaign are used to evaluate the model, and the outputs will also be compared to higher-resolution simulations that have been conducted using the Meso-NH model in the context of the LIAISE project. The impacts of irrigation will be studied using various resolutions of the LAM from 10 to 50km, to better understand the scales at which land-surface coupling processes can be explicitly resolved by the dynamics of the model, and assess the importance of parametrizating these processes.

How to cite: Tiengou, P., Ducharne, A., Cheruy, F., Meurdesoif, Y., and Arboleda, P.: Regional impacts of simulated irrigation in the IPSL climate model., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6236, https://doi.org/10.5194/egusphere-egu24-6236, 2024.

The global water cycle has undergone considerable changes since pre-industrial times due to global climate change and land-use changes. These drivers will almost certainly continue to change during the course of this century. However, where, how, and to which extent terrestrial moisture recycling will change as a result remains unclear.

Mutually consistent scenarios of climate change and land-use changes for the 21^st century are provided by the Shared Socioeconomic Pathways (SSPs). The SSPs provide a framework of five different narratives involving varying degrees of challenges associated with mitigation or adaptation. From each narrative follow different implications for emissions, energy, and land use. The SSPs serve as the conceptual framework behind the sixth generation of the Coupled Model Intercomparison Project, CMIP6.

Terrestrial moisture recycling is often assessed using atmospheric moisture tracking models. An example is UTrack, a Lagrangian model to track moisture through three-dimensional space. Here we present a new forward-tracking version of UTrack that is forced by output of a CMIP6 model to study how terrestrial moisture recycling may change across the globe until the end of the  21^st century in a range of SSPs, from mild to severe: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. For this forcing, we chose the Norwegian Earth System Model version 2, or NorESM2. It has a temporal resolution of one day and a spatial resolution of 1.25° × 0.9375° at eight pressure levels.

We find that across the 21^st century, the global terrestrial moisture recycling ratio decreases with the severity of the Shared Socioeconomic Pathways (SSPs). We calculate a decrease in global terrestrial precipitation recycling by 2.1% with every degree of global warming. Because the SSPs represent internally consistent scenarios of both global warming and global land cover changes, it is hard to distinguish the relative contributions of these two, but the evidence points at a major influence of global warming on moisture recycling.

We find spatial differences in trends in recycling ratios, but which are broadly consistent among SSPs. If a change in precipitation (either drying or wetting) coincides with an increase in terrestrial precipitation recycling ratio, we call it land-dominated. We call the change in precipitation ocean-dominated if it coincides with a decrease in terrestrial precipitation recycling ratio. Land dominance tends to occur in regions with already large terrestrial precipitation recycling ratios, mainly interior South America (land-dominated drying) and eastern Asia (land-dominated wetting). Land-dominated drying may also happen in eastern Europe, in central America and in subtropical sub-Saharan Africa. Ocean-dominance, mainly in the form of wetting, is found primarily in the high northern latitudes and in central Africa.

We also simulated the changes in basin recycling for the 27 major river basins of the world, confirming the overall tendency of decreasing recycling with severity of the SSP, as well as its spatial variations.

How to cite: Staal, A., Meijer, P., Nyasulu, M. K., Tuinenburg, O., and Dekker, S.: Global terrestrial moisture recycling in Shared Socioeconomic Pathways, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8049, https://doi.org/10.5194/egusphere-egu24-8049, 2024.

The availability of fresh water over land may become increasingly scarce under climate change. Future large scale tree cover changes can either enhance or mitigate this water scarcity. Previous work focused mostly on the impact of tree cover change in our current climate. Instead, we investigate the impact of climate change and future global tree cover change on precipitation, evapotranspiration, and runoff (water availability) in a future climate. To do so, multiple datasets and methodologies are combined; data from five CMIP6 models, a future tree cover change dataset, six Budyko models and a moisture recycling dataset. With this interdisciplinary data-driven approach the separate and combined effects of future climate change and future large-scale tree cover change can be quantified. The changes in water availability are studied on grid cell level (1 by 1 degrees), averaged over the globe, and aggregated for selected river basins (Yukon, Mississippi, Amazon, Danube and Murray-Darling).

Globally averaged, future climate change results in an increase in runoff where future tree cover change decreases the runoff. Both effects are of similar magnitude and lead to a limited net effect in water availability compared to the present climate. However, locally, the effects of tree cover change and climate change can be substantial, resulting in changes in water availability of more than 100 mm/year, either positive or negative. For the five selected river basins different responses in direction and magnitude of water availability are found due to future tree cover change under climate change. In all catchments, except the Mississippi basin, the climate change signal dominates over the tree cover change signal. For the Mississippi basin we find a dominant impact of tree cover change, opposite to the climate change signal, resulting in reduced water availability.

How to cite: Benedict, I., Engel, F., Roebroek, C. T. J., and Hoek van Dijke, A. J.: Hydrological implications of future tree cover change and climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12725, https://doi.org/10.5194/egusphere-egu24-12725, 2024.

Land use and cover change (LULCC) is an important climatic forcing. However, it is challenging to quantify the responses of local precipitation to LULCC forcing due to the complex interaction between the land surface and atmosphere. The ecologically fragile Loess Plateau (LP) of China has experienced evident changes in precipitation patterns, but the underlying mechanism remains unclear. The biophysical effects of LULCC on precipitation and the water vapor balance in the LP region were quantified based on the LULCC forcing experiments from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). We found that the selected 11 Earth system models (ESMs) reproduced the general spatial pattern of annual precipitation on the LP region, with slight overestimation in the southern LP. The multimodel ensemble (MME) average showed that global LULCC forcing exerted a negative effect on long-term mean precipitation in this region during the period of 1850-2014. In particular, it decreased evidently during the period from 1850 to 1960, with a reduction of approximately 14.1 mm. However, a positive effect was detected for the period of 1961-2014, with an increase of 6.4 mm in annual precipitation. This is largely related to the intensified water vapor transport in the southern boundary and westerly belt of the LP region resulting from global LULCC forcing. Furthermore, water vapor balance analysis showed that global LULCC forcing resulted in a divergence in water vapor transport within the LP region, leading to a net water vapor output to the surrounding regions. These findings highlight the importance of considering global LULCC, in addition to regional LULCC, in studying regional climate change and associated impacts on the water cycle.

How to cite: Qiu, L.: Importance of biophysical forcing of global land cover to local precipitation and water vapor budget on the Loess Plateau of China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5039, https://doi.org/10.5194/egusphere-egu24-5039, 2024.

The ecological restoration benefits in the Yellow River Basin (YRB) are significant, characterized by increased vegetation and reduced sediment. However, afforestation has resulted in elevated water consumption, posing a threat to the sustainability of ecological functions and socio-economic water use. Previous studies treating evapotranspiration (ET) as absolute water consumption and neglecting the precipitation increase from water recycling, have introduced considerable uncertainty and limited our understanding and prediction of the process. By combining GLEAM ET data and UTrack data, we depicted the contribution of ET in the YRB to local and surrounding basin precipitation .Our study reveals a substantial increase in ET in the YRB from 1980 to 2020. ET in this basin contributes to precipitation in both local and downstream areas through moisture recycling. On average, ET contributes 107 mm/yr of precipitation locally (21%), with the primary contribution from the Upper and Middle region. Additionally, ET contributes 63, 23, 20, and 20 mm/yr of precipitation to the Haihe River Basin, Yangtze Basin, Huaihe River Basin, and Songliao River Basin, respectively. Alongside the increase in ET, its contribution to precipitation is also rising, diminishing outward from the YRB. The increased ET brings about approximately 11 mm/yr of additional precipitation to YRB, offsetting about a quarter of the ET increase. We also provide a schematic diagram illustrating the water cycle in the YRB, elucidating the proportions of each component. This work contributes to a clearer understanding of the basin's hydrological processes, offering scientific support for water resource management and sustainable development in the changing conditions of the YRB.

How to cite: Zhang, H. and Wang, S.: Increased evapotranspiration in the Yellow River basin brings additional precipitation locally and downwindwards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8107, https://doi.org/10.5194/egusphere-egu24-8107, 2024.

Precipitation can originate from evaporated water over oceans and land in remote locations or from local terrestrial sources. The precipitation due to these local sources is called recycled precipitation. Recycled precipitation has been used extensively to study land-atmosphere interaction and has shown to be helpful when studying the relationship between atmospheric or terrestrial variables and precipitation. Mountainous areas such as the Himalaya, Tibetan Plateau, Alps, Andes, and the Rocky Mountains are a hotspot for high local recycling and land-atmosphere interaction. The North West Himalaya (NWH) has drawn attention recently to the issue of climate change due to the region's drastically reduced rainfall and rapidly rising temperature over the past century. Climate change also affects the large number of processes involved in land-atmosphere interaction. The complex topography and heterogeneous climate of NWH makes it challenging to understand the land-atmosphere interaction in this region. In this study, we use an Eulerian water tagging method implemented into the Weather Research and Forecasting (WRF) model to study land-atmosphere interaction in NWH. This method is considered one of the most accurate techniques to quantify recycled precipitation. We simulated summer (June, July, August, and September) and winter (December, January, February, and March) precipitation in the NWH for twenty years from 2001 to 2020.

Results show that, due to availability of more thermal energy the summer experienced more recycling than winter. The western disturbances in winter and southwest monsoon during summer contributes to the locally evapotranspirated moisture and affects the recycling ratio of NWH. However, the irregular western disturbances lead to high variability in the winter recycling ratio. Our analysis shows a strong diurnal cycle of recycling ratio in NWH which peaks in the afternoon. The trend analysis from twenty years although did not show any significant trend in recycled precipitation, other variables affecting land-atmosphere interaction such as soil moisture, latent heat and 2-meter air temperature showed significant trends in NWH. We also studied land-atmosphere interaction over two contrasting regions: the foothills of Himalaya and the high-elevation region. The recycled precipitation was high in the lower elevations during summer and at higher elevations during winter. We also found higher land-atmosphere interaction during summer at higher elevations and during both summer and winter at foothills. However, due to continuous precipitation along the foothills of NWH, a brief shift in soil moisture to a wet regime is expected during monsoon which reduces the influence of soil moisture on the atmosphere leading to low land-atmosphere interaction. However, good land-atmosphere interaction exists throughout the summer in the higher Himalaya, where this change in regime is not apparent.

How to cite: Navale, A. and Lanka, K.: Land-Atmosphere Interactions over North West Himalaya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-544, https://doi.org/10.5194/egusphere-egu24-544, 2024.

The Tibetan Plateau (TP) has been termed the “Asian water tower” and it plays an important role in regulating the Asian water cycle, which affects billions of people. Although the areal mean evaporation of the TP is not high, the total evaporation integrated over the vast terrain of the TP is huge and may strongly influence downwind regions. However, the ultimate fate of this evaporation moisture remains unclear. This study tracked and quantified TP-originating moisture using an extended WAM2Layers model. The findings reveal that the involvement of moisture from the TP in the downwind precipitation is most pronounced near the eastern boundary of the TP and gradually diminishes eastward. Consequently, the TP moisture ratio in precipitation reaches the highest of over 30% over the central-eastern TP. 44.9–46.7% of TP annual evaporation is recycled over the TP, and 65.1–66.8% of the TP evaporation is reprecipitated over terrestrial China. Moisture recycling of TP origin shows strong seasonal variation, with seasonal patterns largely determined by precipitation, evaporation and wind fields. High levels of evaporation and precipitation over the TP in summer maximize local recycling intensity and recycling ratios. Annual precipitation of TP origin increased mainly around the northeastern TP during 2000–2020. This region consumed more than half of the increased TP evaporation. Further analyses showed that changes in reprecipitation of TP origin were consistent with precipitation trends in nearby downwind areas: when intensified TP evaporation meets intensified precipitation, more TP moisture is precipitated out. This study also analyzed the uncertainty due to different tracking modes in WAM2Layers, i.e., backward and forward moisture tracking. In forward moisture tracking, the annual precipitation recycling ratio (PRR) of the TP was estimated to be 26.9–30.8%. However, due to the non-closure issue of the atmospheric moisture balance equation, the annual PRR in backward tracking could be ~6% lower.

How to cite: Zhang, C., Chen, D., Tang, Q., Huang, J., and Yan, M.: Fate and changes in moisture evaporated from the Tibetan Plateau (2000–2020), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15039, https://doi.org/10.5194/egusphere-egu24-15039, 2024.

How to cite: Insua Costa, D., Keune, J., Koppa, A., Massari, C., and G. Miralles, D.: Analysis of moisture recycling at unprecedented resolution in the western Mediterranean region , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19575, https://doi.org/10.5194/egusphere-egu24-19575, 2024.

To improve our understanding of how we are connected globally through water flows, at scales relevant to policy and management, is imperative for global water stewardship. It is therefore crucial to describe the fate of moisture in the atmosphere by evaluating the global moisture inter-dependencies at the country level.  However, few studies have addressed global moisture inter-dependencies at the country level.

In this study, we present a novel dataset of country-to-country atmospheric moisture flows, including both terrestrial and oceanic sources, and propose an approach to assure the closure of the global and country-scale atmospheric water balance. By adopting an analogy with international trade analysis, we employ an iterative proportional fitting method to adjust the bilateral exchanges of water vapor from sources to sinks, ensuring that the total imported (exported) atmospheric moisture equals the total precipitation (evaporation) derived from ERA5 on an annual basis. 

Relevant analysis to understand water inter-dependencies between countries and regions can be performed from the bilateral matrix we present. We assess the terrestrial moisture recycling ratio (TMR) as the portion of countries’ or regions’ precipitation originating from terrestrial evaporation. Furthermore, we estimate a global TMR of 36%, while we find the highest TMRs are those of Eastern Asia (64%), Eastern Europe (68%), and Central Africa (79%). The bilateral structure of the dataset allows also to shed light on key links (and relative weights) dominating the exchange of atmospheric moisture between two countries or regions, thus supporting inter-countries water governance. For example, Central Africa receives 80% of its terrestrially sourced precipitation from Eastern Africa, while Eastern Europe evenly gets moisture from four distinct links, Eastern Asia, Central Asia, Southern Europe and Northern Europe, covering 70% of its import from terrestrial sources. 

Future studies can leverage the dataset to explore nations’ links in the global atmospheric moisture flow network and assess their role in the global hydrological cycle.

How to cite: Fahrländer, S. F., De Petrillo, E., Tuninetti, M., Andersen, L. S., Monaco, L., Ridolfi, L., and Laio, F.: Reconciling bilateral connections of atmospheric moisture within the hydrological cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16857, https://doi.org/10.5194/egusphere-egu24-16857, 2024.