European Climate Change Research Articles

Mechanisms of European summer drying under climate change

AbstractThe geography of Europe as a continental landmass, located between the arid Sahara and the cold high latitudes (both are dry in terms of absolute humidity), dictates the reliance during summer of Southern Europe (south of 45°N) on stored water from winter and spring, and of Northwestern Europe on a small concentrated low-level moisture jet from the North Atlantic. In a recent study, we explained the projected winter precipitation decline over the Mediterranean under climate change as due to shifts in upper tropospheric stationary waves and to the regional-scale land-water warming contrast. Here, based on the analysis of observations and output from Coupled Model Intercomparison Project phase 5 models,we expand this theory further, documenting howthe winter precipitation decline expands into Southern Europe during spring, dictated by similar dynamical mechanisms, depleting soil moisture and setting the stage for drier summers via soil moisture-precipitation feedbacks. Over Northwestern Europe, an anomalous anticyclonic circulation west of the British Isles displaces the low-level moisture jet northwards, limiting moisture supply, and reducing low-level relative humidity (RH) and rainfall. Finally, we discuss how this comprehensive perspective of European summer climate change can help better understand the variations across model projections, and pave the way for their reduction.

Comprehensive evaluation of satellite-based and reanalysis soil moisture products using in situ observations over China

Abstract. Soil moisture (SM) plays a critical role in the water and energy cycles of the Earth system; consequently, a long-term SM product with high quality is urgently needed. In this study, five SM products, including one microwave remote sensing product – the European Space Agency's Climate Change Initiative (ESA CCI) – and four reanalysis data sets – European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis – Interim (ERA-Interim), National Centers for Environmental Prediction (NCEP), the 20th Century Reanalysis Project from National Oceanic and Atmospheric Administration (NOAA), and the ECMWF Reanalysis 5 (ERA5) – are systematically evaluated using in situ measurements during 1981–2013 in four climate regions at different timescales over the Chinese mainland. The results show that ESA CCI is closest to the observations in terms of both the spatial distributions and magnitude of the monthly SM. All reanalysis products tend to overestimate soil moisture in all regions but have higher correlations than the remote sensing product except in Northwest China. The largest inconsistency is found in southern Northeast China region, with an unbiased root mean square error (ubRMSE) value larger than 0.04. However, all products exhibit certain weaknesses in representing the interannual variation in SM. The largest relative bias of 144.4 % is found for the ERA-Interim SM product under extreme and severe wet conditions in northeastern China, and the lowest relative bias is found for the ESA CCI SM product, with the minimum of 0.48 % under extreme and severe wet conditions in northwestern China. Decomposing mean square errors suggests that the bias terms are the dominant contribution for all products, and the correlation term is large for ESA CCI. As a result, the ESA CCI SM product is a good option for long-term hydrometeorological applications on the Chinese mainland. ERA5 is also a promising product, especially in northern and northwestern China in terms of low bias and high correlation coefficient. This long-term intercomparison study provides clues for SM product enhancement and further hydrological applications.

European cities facing climate change: water management issue

The article provides an overview of spatial and legal solutions related to the issue of water management in cities in the context of climate change. The aim of the research is to identify the main differences between the traditional and integrated approaches to water-related infrastructure based on case studies of European Cities at different scales. Gathering, ordering and comparing adequate solutions will allow to establish guidelines for the development of Polish cities and point out directions for architects and urban planners designing urban spaces. The comparison of good examples with theory would make it possible to verify whether practise corresponds with theory, and whether it can actually - through the synergy of measures – bring new quality to urban areas.

Understanding drivers of wild oyster population persistence

Persistence of wild Pacific oyster, Magallana gigas, also known as Crassostrea gigas, has been increasingly reported across Northern European waters in recent years. While reproduction is inhibited by cold waters, recent warm summer temperature has increased the frequency of spawning events. Although correlation between the increasing abundance of Pacific oyster reefs in Northern European waters and climate change is documented, persistence of wild populations may also be influenced by external recruitment from farmed populations and other wild oyster populations, as well as on competition for resources with aquaculture sites. Our understanding of the combined impact of the spawning frequency, external recruitment, and competition on wild population persistence is limited. This study applied an age-structured model, based on ordinary differential equations, to describe an oyster population under discrete temperature-related dynamics. The impact of more frequent spawning events, external recruitment, and changes in carrying capacity on Pacific oyster density were simulated and compared under theoretical scenarios and two case studies in Southern England. Results indicate that long term persistence of wild oyster populations towards carrying capacity requires a high frequency of spawning events but that in the absence of spawning, external recruitment from farmed populations and other wild oyster populations may act to prevent extinction and increase population density. However, external recruitment sources may be in competition with the wild population so that external recruitment is associated with a reduction in wild population density. The implications of model results are discussed in the context of wild oyster population management.

Garry oak ecosystem stand history in Southwest British Columbia, Canada: implications of environmental change and indigenous land use for ecological restoration and population recovery

In the Pacific Northwest of North America, endangered Garry oak ecosystems have a complex history that integrates effects of Holocene climate change, Indigenous land management, and colonial settlement during the Anthropocene. In western Canada, Garry oak and Douglas fir recruitment corresponds with the end of the Little Ice Age (LIA; ca. 1870), after the collapse of Indigenous populations but in some cases prior to European settlement. We examined establishment patterns at three sites in southwest British Columbia, each with different edaphic characteristics based on slope, exposure, and drainage. At our Somenos Marsh site on Vancouver Island, we see a clear relationship between Indigenous occupation, subsequent European settlement, and development of an oak woodland, indicating that Indigenous land management was important for development of many Garry oak ecosystems. However, at the Tumbo Cliff site (Tumbo Island, BC), shallow soil xeric conditions, regional climate, and periodic fire were likely drivers of stand and ecosystem development. Finally, at the deep soil Tumbo Marsh site, Garry oak established and grew quickly when conditions were favorable, following the early twentieth century conversion of a saltwater tidal flat into a freshwater marsh. Combining site level historical records, site characteristics, and dendrochronological data provides a greater understanding of the local and regional factors that shape the unique structures of Garry oak ecosystems at each site. This information can be integrated into restoration and fire management strategies for Garry oak ecosystems as well as elucidate the timing of European settler and climate change impacts on these ecosystems.

Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone

Measurements of significant wave height from satellite altimeter missions are finding increasing application in investigations of wave climate, sea state variability and trends, in particular as the means to mitigate the general sparsity of in situ measurements. However, many questions remain over the suitability of altimeter data for the representation of extreme sea states and applications in the coastal zone. In this paper, the limitations of altimeter data to estimate coastal Hs extremes (<10 km from shore) are investigated using the European Space Agency Sea State Climate Change Initiative L2P altimeter data v1.1 product recently released. This Sea State CCI product provides near complete global coverage and a continuous record of 28 years. It is used here together with in situ data from moored wave buoys at six sites around the coast of the United States. The limitations of estimating extreme values based on satellite data are quantified and linked to several factors including the impact of data corruption nearshore, the influence of coastline morphology and local wave climate dynamics, and the spatio-temporal sampling achieved by altimeters. The factors combine to lead to considerable underestimation of estimated Hs 10-yr return levels. Sensitivity to these factors is evaluated at specific sites, leading to recommendations about the use of satellite data to estimate extremes and their temporal evolution in coastal environments.

Prolonged duration and increased severity of agricultural droughts during 1978 to 2016 detected by ESA CCI SM in the humid Yunnan Province, Southwest China

Droughts in humid regions may have more severe consequences owing to a lack of drought-resistant measures and awareness. The Yunnan Province, in the humid southwestern part of China, experienced an extreme drought from 2009 to 2010. However, few studies have systematically explored agricultural droughts in this region. Based on revised global multi-source microwave-based SM products, the European Space Agency's Climate Change Initiative Soil Moisture (ESA CCI SM) data, the 10-day-scale soil moisture (SM) series was constructed and applied to detect droughts and analyze changes in drought characteristics, including duration, area, frequency, intensity, and severity. The results suggest that the intensity of agricultural drought in the Yunnan Province decreased, while the drought frequency increased. Drought duration increased by 20 days, collectively leading to a significant increase in drought severity in the last decade. Qujing in the east was most sensitive to agricultural drought, followed by Kunming and Chuxiong in the central area. The southwest region was prone to long drought and maintained an upward trend in terms of drought area. Regional SM with complicated temporal-spatial change patterns cannot be attributed to a single trend of “dry to dryer, wet to wetter”. This study may provide insights into drought analysis in other humid regions.

The Challenge of Climate Change for Coastal Tourism in the Azores

Abstract The case study provides an overview of coastal tourism in the Azores and the probable future impacts of climate change on the islands. It summarizes the findings of a recent study undertaken by an international team of experts, including the authors, to determine how serious the impacts are, in particular on tourism. It considers these effects in the light of European and worldwide climate change mitigation policies. Information Adapted from ‘Chapter 10: Case Study Portugal: Addressing Tourism Development and Climate Change in Small Atlantic Islands: the Case of the Azores’. In: Jones A. and Phillips M. (eds) Global Climate Change and Coastal Tourism . CABI, pp. 125-137. © CAB International 2018

Assessing the role and consistency of satellite observation products in global physical–biogeochemical ocean reanalysis

Abstract. As part of the European Space Agency's Climate Change Initiative, new sets of satellite observation products have been produced for essential climate variables including ocean colour, sea surface temperature, sea level, and sea ice. These new products have been assimilated into a global physical–biogeochemical ocean model to create a set of 13-year reanalyses at 1∘ resolution and 3-year reanalyses at 1∕4∘ resolution. In a series of experiments, the variables were assimilated individually and in combination in order to assess their consistency from a data assimilation perspective. The satellite products, and the reanalyses assimilating them, were found to be consistent in their representation of spatial features such as fronts, sea ice extent, and bloom activity. Assimilating multiple variables together often resulted in larger mean increments for a variable than assimilating it individually, providing information about model biases and compensating errors which could be addressed in the future development of the model and assimilation scheme. Sea surface fugacity of carbon dioxide had lower errors against independent observations in the higher-resolution simulations and was improved by assimilating ocean colour or sea ice concentration, but it was degraded by assimilating sea surface temperature or sea level anomaly. Phytoplankton biomass correlated more strongly with net air–sea heat fluxes in the reanalyses than chlorophyll concentration did, and the correlation was weakened by assimilating ocean colour data, suggesting that studies of phytoplankton bloom initiation based solely on chlorophyll data may not provide a full understanding of the underlying processes.

Extended Categorical Triple Collocation for Evaluating Sea Ice/Open Water Data Sets

A method to extend categorical triple collocation (CTC) to five data sets, three of which must have conditionally independent errors, is presented. The method is shown to enable comparison of three passive microwave sea ice concentration data sets, and can easily be extended to for use with more data sets. The method is evaluated in the Gulf of Saint Lawrence, on the east coast of Canada, during the freeze-up period. It is found that the ice concentration data set from the European space agency sea ice climate change initiative (ESA-SICCI) and the NASA Team 2 (NT2) algorithms have higher balanced accuracy than that from the Artist sea ice (ASI) algorithm.

Auswirkungen der Corona-Krise auf die europ\xe4ische Klimaschutzpolitik

ZusammenfassungNeben vielen anderen negativen Folgen hat die Corona-Krise auch direkte Auswirkungen auf den EU-weiten Handel mit Emissionszertifikaten für Treibhausgasemissionen. Dieser stellt einen Eckpfeiler der europäischen Klimaschutzpolitik dar. Den kurzfristig geringer zu erwartenden Treibhausgasemissionen stehen aufgrund der erwarteten Rezession mittel- und langfristig niedrigere Preise für Emissionsrechte gegenüber. Diese machen die gegenwärtigen Produktionstechnologien tendenziell attraktiver. Dadurch wird eine wesentliche Zielsetzung europäischer Klimaschutzpolitik, der ökonomisch-rationale Wechsel der Unternehmen auf klimafreundlichere Produktionstechnologien, erschwert.

Round Robin Assessment of Radar Altimeter Low Resolution Mode and Delay-Doppler Retracking Algorithms for Significant Wave Height

Radar altimeters have been measuring ocean significant wave height for more than three decades, with their data used to record the severity of storms, the mixing of surface waters and the potential threats to offshore structures and low-lying land, and to improve operational wave forecasting. Understanding climate change and long-term planning for enhanced storm and flooding hazards are imposing more stringent requirements on the robustness, precision, and accuracy of the estimates than have hitherto been needed. Taking advantage of novel retracking algorithms, particularly developed for the coastal zone, the present work aims at establishing an objective baseline processing chain for wave height retrieval that can be adapted to all satellite missions. In order to determine the best performing retracking algorithm for both Low Resolution Mode and Delay-Doppler altimetry, an objective assessment is conducted in the framework of the European Space Agency Sea State Climate Change Initiative project. All algorithms process the same Level-1 input dataset covering a time-period of up to two years. As a reference for validation, an ERA5-based hindcast wave model as well as an in-situ buoy dataset from the Copernicus Marine Environment Monitoring Service In Situ Thematic Centre database are used. Five different metrics are evaluated: percentage and types of outliers, level of measurement noise, wave spectral variability, comparison against wave models, and comparison against in-situ data. The metrics are evaluated as a function of the distance to the nearest coast and the sea state. The results of the assessment show that all novel retracking algorithms perform better in the majority of the metrics than the baseline algorithms currently used for operational generation of the products. Nevertheless, the performance of the retrackers strongly differ depending on the coastal proximity and the sea state. Some retrackers show high correlations with the wave models and in-situ data but significantly under- or overestimate large-scale spectral variability. We propose a weighting scheme to select the most suitable retrackers for the Sea State Climate Change Initiative programme.

Remote sensing linear trends of the Gulf Stream from 1993 to 2016

The Gulf Stream (GS) transports a massive amount of heat northward to high latitudes and releases sensible and latent heat to the atmosphere, playing an important role in the North Atlantic and European climate change. The change trends of the GS transport and pathway are still uncertain to date. Our analyses of altimeter observations from 1993 to 2016 indicate that the linear trends in surface maximum speed, transport, and latitudinal location of the GS are significant east of 61° W at the 95% level while they are small and not significant between 72° W and 61° W. The weakening trend of the GS during the period from 1993 to 2016 is accompanied with a southward-shifting path, which is associated with the decline of the North Atlantic Oscillation (NAO) and possibly reduction in the Atlantic meridional overturning circulation (AMOC).

The effect of considering polar vortex dynamics in the validation of satellite total ozone observations

The main aim of this paper is to demonstrate the magnitude in which validation results of space-based total ozone column, TOC, measurements are affected by the location of the polar vortex. Potential Vorticity is used as an indicator to determine the polar vortex's boundary and surface area, provided by ERA-Interim reanalysis datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF). The total ozone measurements that were examined fall within the hemispherical winter-spring period, focusing on middle and high latitudes on both hemispheres. The space-based total ozone data produced by the GODFIT (GOME-type Direct FITting) v4 algorithm as applied to the OMI/Aura, GOME-2/Metop-A and Metop-B observations, part of the European Space Agency's Ozone Climate Change Initiative project, are compared to TOC measurements from Brewer and Dobson spectrophotometers archived at the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) repository. The satellite-to-ground collocations were classified depending on whether both satellite and ground-based measurements are inside or outside the polar vortex (matched) or one measurement is inside whereas the other one is outside the polar vortex (mismatched). It is shown that the matched cases present an improved agreement between satellite and ground TOC measurements compared to the mismatched cases. Considering all examined stations for GOME2-A, GOME2-B, and OMI, the mean bias for the mismatched cases was found to be 2.22 ± 0.4%, 1.84 ± 0.57%, and 1.93 ± 0.39% respectively, while for the matched cases was found to be 1.46 ± 0.17%, 1.69 ± 0.22%, 1.7 ± 0.19% respectively. For the three satellite sensors, the mismatched cases do not exceed 3.3% of the total available collocations per station during the winter-spring period between years 2007 and 2017, where applicable. Hence, on a global scale, the exclusion of mismatched collocated measurements does not cause significant changes and the resulting impact on the validation of the satellite TOCs is small. However, when considering single stations consistently affected by the polar vortex, we conclude that mismatched cases should be excluded from the comparisons.

Satellite-based global-scale irrigation water use and its contemporary trends

Irrigated agriculture is important for satisfying the increasing world food demand, but it interrupts the natural hydrological cycle by applying additional water to crops. Accurate information regarding irrigation water use (IWU) is a prerequisite to exploit land surface modeling and to quantify the uncertainty of climate projections. In this study, the global IWU was estimated for 2000–2015 by combining satellite-based soil moisture (SM) observations from the European Space Agency's Climate Change Initiative (ESA CCI) and the model estimated SM from European ReAnalysis-5 (ERA5). Considering irrigation as an unmodeled hydrological process in ERA5 and the ability of ESA CCI SM to capture the irrigation patterns, the global IWU was estimated by solving the water balance equations for ESA CCI and ERA5 SM. Owing to the global absence of ground-truth data for IWU, the IWU estimates were compared with the reported irrigation water withdrawals (IWWs) provided by Food and Agriculture Organization. The results indicated that satellite-based SM observations have the potential to identify global irrigation. All three ESA CCI products (active, passive, and merged) discerned the global irrigated areas satisfactorily, and the estimated IWU captured the pattern of the country-level IWWs (R = 0.77, 0.72, and 0.81 for active, passive, and merged products, respectively). However, the estimated IWU substantially underestimated the reported IWWs (bias of −76.55, −76.01, and −73.93 km3 for active, passive, and merged products, respectively) due to the coarse spatial resolution (0.25° × 0.25°) of the microwave remote sensing products and the inclusion of supplemental water in the IWWs, which was lost during distribution to crops. Trend analysis of the IWU indicated an increasing trend of the IWU in the first decade of the 21st century. However, in recent years the trend has reversed due to advances in agriculture technology and the adoption of water-efficient irrigation methods.

Comparison of soil moisture products from microwave remote sensing, land model, and reanalysis using global ground observations

AbstractHigh‐quality soil moisture (SM) datasets are in great demand for climate, hydrology, and other fields, but detailed evaluation of SM products from various sources is scarce. Thus, using 670 SM stations worldwide, we evaluated and compared SM products from microwave remote sensing [Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) (C‐ and X‐bands) and European Space Agency's Climate Change Initiative (ESA CCI)], land surface model [Global Land Data Assimilation System (GLDAS)], and reanalysis data [ECMWF Re‐Analysis‐Interim (ERA‐Interim) and National Centers for Environmental Prediction (NCEP)] under different time scales and various climates and land covers. We find that: (a) ESA CCI and GLDAS have the closest values to the in situ SM on the annual scale, whereas others overestimate the SM; ERA‐Interim (averaged R = 0.58) and ESA CCI (averaged R = 0.54) correlate best with the in situ data, while GLDAS performs worst. (b) Overall, the deviations of each product vary in seasons. ESA CCI and ERA‐Interim products are closer to the in situ SM at seasonal scales, and AMSR‐E and NCEP perform worst in December–February and June–August, respectively. (c) Except for NCEP and ERA‐Interim, others can well reflect the intermonthly variation of the in situ SM. (d) Under various climates and land covers, AMSR‐E products are less effective in cold climates, whereas GLDAS and NCEP products perform poorly in arid or temperate and dry climates. Moreover, the Bias and R of each SM product differ obviously under different forest types, especially the AMSR‐E products. In summary, SM from ESA CCI is the best, followed by ERA‐Interim product, and precipitation is an important auxiliary data for selecting high‐quality SM stations and improving the accuracy of SM from GLDAS. These results can provide a reference for improving the accuracy of the above SM products.

Adapting scenarios for climate adaptation: Practitioners’ perspectives on a popular planning method

Scenario planning is a popular decision-support method that is increasingly being applied to climate change adaptation. However, evaluation of scenario planning for adaptation is lacking. In this paper we summarise a science-policy session held at the European Climate Change Adaptation Conference in May 2019, where practitioners explored the strengths and weaknesses of scenario planning for climate adaptation and identified modifications to enhance the method’s utility. Eight case studies spanning three scenario planning types (problem-focused, actor-focused and reflexive-interventionist) from varied socio-cultural contexts were presented by the authors, followed by discussion amongst the 40 participants. Strengths focussed on opportunities provided by scenario planning for stakeholder participation, and raising their awareness about future risks, vulnerability and uncertainty. Participatory scenario planning was most useful for building stakeholder consensus at the local scale (e.g. communities, neighbourhoods) over shorter timeframes (e.g. 20 years). Weaknesses centred on the inability of scenarios to generate quantitative predictions and concrete adaptation solutions. This was partly attributed to practitioners’ limited understanding of stakeholder politics and power dynamics, and the resulting lack of integration of scenario exercises within decision-making processes. Scenarios were also limited by being static, and participatory processes were resource-intensive. Suggested modifications were to develop iterative scenario planning embedded within decision-making cycles. Such ‘transient scenarios’ could absorb system feedbacks and updated information to prioritise adaptation responses, thus actively contributing to ongoing adaptation pathways. Applying monitoring, evaluating and learning would enable reflexive refinement of the method, adapting it to become an agile approach applicable to varied socio-cultural and political contexts.

Enhanced Climate Change Response of Wintertime North Atlantic Circulation, Cyclonic Activity, and Precipitation in a 25-km-Resolution Global Atmospheric Model

Abstract Wintertime midlatitude cyclone activity and precipitation are projected to increase across northern Europe and decrease over southern Europe, particularly over the western Mediterranean. Greater confidence in these regional projections may be established by their replication in state-of-the-art, high-resolution global climate models that resolve synoptic-scale dynamics. We evaluated the representation of the wintertime eddy-driven and subtropical jet streams, extratropical cyclone activity, and precipitation across the North Atlantic and Europe under historical (1985–2011) and RCP8.5 sea surface temperature forcing in an ensemble of atmosphere-only HadGEM3-GA3.0 simulations, where horizontal atmospheric resolution is increased from 135 to 25 km. Under RCP8.5, increased (decreased) frequency of northern (southern) eddy-driven jet occurrences and a basinwide poleward shift in the upper-level westerly flow are simulated. Increasing atmospheric resolution significantly enhances these climate change responses. At 25-km resolution, these enhanced changes in large-scale circulation amplify increases (decreases) in extratropical cyclone track density and mean intensity across the northern (southern) Euro-Atlantic region under RCP8.5. These synoptic changes with resolution impact the overall climate change response of mean and heavy winter precipitation: wetter (drier) conditions in northern (southern) Europe are also amplified at 25-km resolution. For example, the reduction in heavy precipitation simulated over the Iberian Peninsula under RCP8.5 is ~15% at 135 km but ~30% at 25-km resolution. Conversely, a shift to more frequent high extratropical cyclone (ETC)-associated precipitation rates is simulated over Scandinavia under RCP8.5, which is enhanced at 25 km. This study provides evidence that global atmospheric resolution may be a crucial consideration in European winter climate change projections.

Contributions of climate change and groundwater extraction to soil moisture trends

Abstract. Climate change affects water availability for soil, and groundwater extraction influences water redistribution by altering water demand, both of which significantly affect soil moisture. Quantifying their relative contribution to the changes in soil moisture will further our understanding of the mechanisms underlying the global water cycle. In this study, two groups of simulations were conducted with and without groundwater (GW) extraction (estimated based on local water supply and demand) from 1979 to 2010 using the Chinese Academy of Sciences land surface model, CAS-LSM, with four global meteorological forcing datasets (GSWP3, PRINCETON, CRU-NCEP, and WFDEI). To investigate the contribution of climate change and GW extraction, a trajectory-based method was used. Comparing the simulated results with the in situ dataset of the International Soil Moisture Network (ISMN) and the satellite-based soil moisture product of the European Space Agency's Climate Change Initiative (ESA-CCI) indicated that the CAS-LSM reasonably reproduced the distribution of soil moisture and matched the temporal changes well. Globally, our results suggested a significant decreasing trend in surface soil moisture (0–10 cm, 0.98×10-4 mm3 mm−3 yr−1) over the 32-year period tested. The drying trends were mainly observed in arid regions such as the tropical desert regions in North Africa and the Arabian Peninsula, while the wetting trends were primarily in tropical forested areas in South America and northeastern Asia. Climate change contributed 101.2 % and 90.7 % to global drying and wetting trends of surface soil moisture, respectively, while GW extraction accounted for −1.2 % and 9.3 %, respectively. In deep soil, GW extraction contributed 1.37 % and −3.21 % to the drying and wetting trends, respectively. The weak influence of GW extraction may be because this activity occurs in limited areas. GW extraction contributed more than 35 % to the change in surface soil moisture in wetting areas where GW overexploitation occurs. GW is mainly extracted for irrigation to alleviate soil water stress in semiarid regions that receive limited precipitation, thereby slowing the drying trend and accelerating the wetting trend of surface soil. However, GW exploitation weakens the hydraulic connection between the soil and aquifer, leading to deeper soils drying up. Overall, climate change dominated the soil moisture trends, but the effect of GW extraction cannot be ignored.

Characterizing satellite‐derived soil moisture and its relationship with rainfall over India

AbstractUnderstanding the spatial and temporal variations of soil moisture is important since the feedback between soil moisture and precipitation is a key control of the climate. This is also important as soil moisture data is a key input in regional climate models. The inter‐annual and inter‐decadal variability of soil moisture has been investigated here using the European Space Agency's Climate Change Initiative active and passive combined soil moisture product over different climate regimes of India. The observed soil moisture and rainfall are positively correlated and their relationship in this study suggests that both positive and negative feedback occur. The analysis showed an increasing soil moisture trend with a significant increase in the monsoon and autumn seasons for the past two decades over central India, where the frequency of extreme precipitation increased in the same period. An overall increase in soil moisture over the western arid region is also significant. A decreasing trend in soil moisture prevailed throughout the monsoon season over eastern India, where monsoon depressions make landfall, signalling the recent climate trends over the Indian subcontinent.