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Modeling air quality has always been a challenge in global models constrained by coarse grids. Here, the variable‐resolution Community Atmosphere Model with full chemistry based on the scalable spectral element (SE) dynamical core (MUSICAv0) is applied in simulating air pollution with a finer grid resolution of ∼0.25° over East Asia (SE_VR), in contrast to the same model with a uniform resolution of ∼1.0° (SE_UR). Two nudging experiments and four free‐running experiments are conducted to investigate the capabilities of SE_VR in modeling the air pollution and aerosol‐planetary boundary layer (PBL) interactions over China. Results show the regional refinement in SE_VR is essential for simulating haze events over complex terrain areas attributed to its better performance in representing the local vertical and horizontal dispersion conditions. SE_VR shows prominent advantages over SE_UR in simulating surface ozone because of better resolving spatial segregation of NOx and volatile organic compounds (VOC) chemical regimes and subsequently representing more detailed chemical processes related to ozone formation, although the model generally overestimates surface ozone over China. Further analysis of SE_VR shows the daytime radiative effect of black carbon (BC) aerosols lowers PBL height by 12.0% (17.9%), and leads to an increase of PM2.5 by 14.5% (10.8%) under the moderate (severe) air pollution conditions over Sichuan Basin. However, SE_UR has deficiencies in simulating BC‐PBL interactions due to its inability to reproduce the strong inverse temperature structure caused by BC aerosols in the lower atmosphere layer. Our results highlight the value of variable‐resolution global models for simulating air pollution and its interactions with climate. Plain Language Summary: Air pollution has been demonstrated to be harmful to humans and the living environment over East Asia. Simulations of air pollution are traditionally performed with regional or global models. However, uncertainties remain in air quality simulations due to insufficient resolution to resolve the regional‐scale processes in global models or the inconsistency of chemical and physical schemes between regional and global models. In this work, we conduct experiments using a variable‐resolution global climate model to explore the improvement of regional refinement in simulating the air quality and aerosol‐PBL interactions over China. The experiment with grid refinement over East Asia simulates PM2.5 and ozone concentrations better, as well as improving the aerosol‐PBL interaction simulations. The finer grids are more essential in improving the haze event simulation at the complex terrain regions due to better presenting the local vertical and horizontal dispersion conditions associated with the accumulation and aggregation of pollutants. Finer grids show prominent advantages in the representation of spatial segregation of NOx and VOC chemical regimes, improving the ozone simulation over China. Moreover, refinement grids reproduce the strong inverse temperature structure caused by BC aerosols in the low atmosphere and improve simulations of the impacts of BC‐PBL interactions on air quality. Key Points: The MUSICAv0 model with regional refinement over East Asia improves haze event simulations, especially in complex terrain areasFiner grids can resolve a greater range of NOx and volatile organic compounds (VOC) chemical regimes, significantly reducing the ozone overestimation in coarser gridsFiner grids improve the boundary layer representation of black carbon featured by stronger inverse temperature structure in the lower atmosphere [ABSTRACT FROM AUTHOR]

The unexpected emergence of the 2019 coronavirus disease (COVID‐19) pandemic resulted in anthropogenic emissions changes, which have significant consequences for the regional and global climate. However, the long‐term impacts of emission reductions and recovery scenarios on regional climate change in China remain unknown. We use the COVID Model Intercomparison Project (CovidMIP) simulations to project climate change in China in the mid‐21st century under four recovery emission pathways in the post‐COVID era. We found that the temporary emission cut during the COVID‐19 lockdown under the 2‐year‐blip scenario has limited long‐term impact on regional climate change. Anthropogenic emissions are reduced under moderate and stringent greening recovery pathways, leading to reductions of 0.17 ± 0.09°C and 0.35 ± 0.10°C in surface air temperature (SAT) relative to the SSP2‐4.5 baseline in China, respectively. Although the reduction of greenhouse gas emissions decreases SAT, the simultaneous enhanced surface solar radiation due to reduced aerosol concentrations partly offsets the GHG‐induced cooling. Additionally, the weakened aerosol‐cloud interactions associated with reduced aerosols increase the national precipitation by 1.30 ± 0.88 mm month−1 (1.63 ± 1.11%) and 1.91 ± 0.60 mm month−1 (2.39 ± 0.77%) in two green scenarios. As a comparison, regional precipitation decreases by 0.40 ± 0.53 mm month−1 (0.50 ± 0.66%) in the fossil‐based recovery scenario. Therefore, long‐term climate change is more dominated by the emission recovery pathways rather than short‐term emission reduction during the pandemic for China. Plain Language Summary: The COVID‐19 pandemic led to reductions in CO2 and aerosol emissions globally during 2020. This has substantial implications for climate at both the regional and global scales. Here, we use the simulations from CovidMIP to project climate change in China by the midcentury under different COVID‐19 recovery emission pathways. We find that the short‐term emission reduction during the pandemic has limited impacts on the long‐term climate change, which is more dominated by the emission recovery after the pandemic. Under the greening recovery pathway similar to carbon neutrality, reduced CO2 mitigates warming while reduced aerosols increase precipitation in China compared to the baseline climate. Key Points: Short‐term emission reduction during the pandemic has limited impacts on the long‐term climate changeThe cooling from reduced greenhouse gas is partly offset by the warming from reduced aerosols under the greening recovery pathwaysWeakened aerosol‐cloud interactions increase precipitation in China under a carbon neutral pathway [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is predominant variable for water management in various types of ecosystems, and it has been intensively studied through in situ measuring and modeling methods. However, it is challenging to measure actual ET and upscale it to regional level for karst landscapes, where aquifers typically show remarkable and rapid responses to precipitation events. There is an urgent need to quantify water fluxes to provide reliable evidence for the protection and sustainable management of karst water resources. Therefore, in this study, five plots were built to observe actual ET based on Thermal Dissipation Probes, redesigned ventilated chamber and in‐site microlysimeters in a karst watershed in southwest China. Then, three models (Penman‐Monteith‐Leurning, PML; Remote Sensing‐Priestley and Taylor; and Hargreaves) were constructed to upscale ET estimation to the regional level based on Landsat‐8 images and MODIS data. The results showed that: (a) The PML model performed better than other models (p < 0.01) with higher R2 values (0.72 for MODIS images and 0.87 for Landsat‐8 images); (b) Daily ET exhibited significant seasonal variability and different spatial distribution, and yearly ET exhibited well related with soil thickness (R2 = 0.58); (c) Daily ET had a slightly positive correlation with DEM, however, had a negative correlation with ground temperature. This study is helpful to improve accuracy of measured and estimated ET by combining remote sensing data, and it has important implications for upscaling it to regional level. It suggests that ET is strongly regulated by constant supply of water, vegetation coverage, and available energy in karst catchments. Plain Language Summary: Evapotranspiration (ET) process bonds water, energy cycle, and carbon cycles. Aiming to characterize ET processes and impact controls at regional level for karst landscapes, five plots were built to observe actual ET, and three models were selected to upscale ET estimation to the regional level using Landsant‐8 and MODIS data in this study. The results showed that the Penman‐Monteith‐Leurning model performed the best and additional validation data observed in experimental spots were identified and corresponded with satellite data. Vegetation coverage and the density of conducting tissue (e.g., LAI) both contributed to ET seasonality and the spatial distribution differences. Soil thickness is a key prediction for the ratio distribution of yearly evapotranspiration to precipitation in karst watershed in southwest China. Key Points: Multiple models based on different data sources exhibited different accuracy on evapotranspiration simulation in karst basinYearly evapotranspiration distribution is well related with soil thicknessGround temperature exhibited negative correlation with daily evapotranspiration [ABSTRACT FROM AUTHOR]

Drought can develop rapidly over a short period, the so‐called "flash drought". The widely used standardized precipitation evapotranspiration index (SPEI), with traditional time scales longer than 1 month, cannot easily capture flash drought signals. Here, the SPEI with a 5‐day (pentad) time scale was proposed to investigate flash droughts in China from 1980 to 2017. New criteria for flash droughts based on the high‐resolution index were also developed. Flash droughts were stronger and longer in western and northern China. The intensity and duration of mild, moderate, and severe flash droughts increased during the study period, while severe flash droughts showed the largest increase. The high‐resolution SPEI permits us to examine the process of a drought event, that is, how a mild flash drought develops into a severe flash drought. The contribution of precipitation deficit to the duration of mild flash droughts was 50%. As the intensity of flash droughts increased, the contribution of high temperature and increased net radiation to flash drought duration increased from 50% (mild flash droughts) to 74% (severe flash droughts). When flash droughts occurred, Northwestern China and Southwestern China were dominated by unusually weak water vapor transport, while Northeastern China, Northern China, Southern China ,and Middle‐Lower Yangtze were mainly dominated by abnormal downward motion. The downward motion was generally accompanied by clear sky conditions with fewer clouds, higher air temperature, and higher surface solar radiation, which accelerated and amplified flash droughts triggered by initial precipitation deficits. Plain Language Summary: In recent years, a rapidly developing drought has attracted widespread attention, and it is known as the "flash drought". However, existing drought indices do not capture the signals of flash drought event life cycles. In this study, the existing drought index (SPEI) was upgraded to a higher temporal resolution to explore the spatial distribution and temporal changes in flash droughts in China. The results showed that the flash drought was intense and long‐lasting in western and northern China. In the past 38 yr, flash droughts have become more intense and more difficult to recover from, especially severe flash droughts. As the intensity of flash droughts increased, the impact of precipitation decreased, while temperature and net radiation gradually played leading roles. Flash droughts in Northwestern China and Southwestern China were mainly related to weak water vapor transport, while they were affected by strong downward motion in Northeastern China, Northern China, Southern China, and Middle‐Lower Yangtze. The downward motion was generally accompanied by clear sky conditions with fewer clouds, higher air temperature, and higher surface solar radiation, which accelerated and amplified flash droughts triggered by initial precipitation deficits. Key Points: A high temporal resolution drought index and new criteria were developed to identify flash droughts over ChinaThe intensity and duration of the flash drought increased significantly from 1980 to 2017 over China, especially the severe flash droughtThe precipitation deficit initiated a mild flash drought, and interactions with air temperature and net radiation amplified the drought intensity [ABSTRACT FROM AUTHOR]

Lake ice sublimation plays an important role in lake water budget, while there is huge uncertainty in estimation of lake ice sublimation and its proportion in annual lake total water vapor flux. In the present study, we investigated the annual total water vapor flux and ice sublimation at 15 frozen lakes or lake groups in China using three different methods, namely, the Community Land Model (CLM) simulations (Penman‐Monteith equation and pan observations) that considers (could not reflect) heat storage of lakes; the potential changes of lake total water vapor flux and ice sublimation with climate warming were also predicted. The results illustrate that the annual lake total water vapor flux obtained from Penman‐Monteith equation, pan observation, CLM simulation decreased in sequence, and ice sublimation obtained from pan observation, Penman‐Monteith equation, CLM simulation decreased in sequence. The lake ice sublimation from CLM occupied 7.4%–26.6% of corresponding annual lake total water vapor flux during 1950s–2010s in different regions of China. The ice sublimation and its proportion in lake total water vapor flux from these three methods were all highly correlated, with R2 being 0.86–0.97. The annual lake total water vapor flux will significantly increase in all frozen‐lake regions in China with the climate warming. Climate warming potentially reduce sublimation at most lakes. Key Points: Community Land Model (CLM) method is more accurate than pan and P‐M methods in calculating lake ice sublimationIce sublimation from CLM occupied 7.4%–26.6% of lake total water vapor fluxAnnual lake total water vapor flux will significantly increase in China with climate warming [ABSTRACT FROM AUTHOR]

Periods of dimming and brightening have been recorded in observational datasets of surface solar radiation (SSR) between the mid‐20th century and present day. Atmospheric components affect SSR, including aerosols and clouds, though studies disagree somewhat about the relative effect of each component in different regions. Current Earth system models (ESMs) are unable to simulate observed trends in SSR. This study includes an investigation into observed SSR variations between 1961 and 2014 and an evaluation of the effects of cloud cover variations and impacts of aerosol extinction, using timeseries of SSR and cloud cover from in‐situ measurements. Historical simulations by 42 ESMs participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) have also been studied and compared to observations. The observational study indicates that cloud cover has had a dampening effect on the variations of SSR and that emissions of aerosol and aerosol precursors are the main cause of the general trends in observed SSR in four regions—China, Japan, Europe, and the United States—during 1961–2014. The study of simulated SSR in CMIP6 yields the conclusion that current ESMs remain unable to simulate the magnitude of observed dimming and brightening in China, Japan, and the United States, but that the European SSR trends between 1961 and 2014 are fairly well reproduced in the ESMs. A rough quantification of the regional surface radiation extinction efficiency of aerosol and precursor emissions in the simulations is found to agree with observed values in Europe, but not in the other three regions. Plain Language Summary: Measurements of incoming sunlight at the Earth's surface between the 1960s and the 1980s show a substantial downward trend globally, and between the 1980s and the 2000s an upward trend has followed, albeit weaker. These two trends are often called dimming and brightening, respectively. The reasons for dimming and brightening are not clear, although evidence supports the role of atmospheric components, prominently aerosol emissions and clouds; changes in aerosol emissions and clouds can cause changes in incoming sunlight at the surface because of their ability to absorb or reflect sunlight on its way through the atmosphere. In this study, measurements of incoming sunlight at the surface are investigated and compared with simulations from state‐of‐the‐art Earth system models (ESMs). The study reinforce evidence that aerosol emission changes have been causal to observed regional dimming and brightening, and suggests that cloud cover changes have not caused the trends. The study also finds that ESMs are unable to compute dimming and brightening trends in several regions, which may suggest that the models are not accurately reproducing the atmospheric processes that cause the trends. Key Points: This study supports evidence that dimming and brightening trends between 1961 and 2014 in China, Japan, Europe and the United States were caused by variations in aerosol‐ and aerosol precursor emissions, and not by cloud cover changesResults confirm and reinforce previous indications that Coupled Model Intercomparison Project phase 6 simulations are able to reproduce surface solar radiation trends observed in Europe, but not in China, Japan, and the United States [ABSTRACT FROM AUTHOR]

Solar radiation received at the Earth's surface (Rs) is comprised of two components, the direct radiation (Rd) and the diffuse radiation (Rf). Rd, the direct beam from the sun, is essential for concentrated solar power generation. Rf, scattered by atmospheric molecules, aerosols, or cloud droplets, has a fertilization effect on plant photosynthesis. But how Rd and Rf change diurnally is largely unknown owing to the lack of long‐term measurements. Taking advantage of 22 years of homogeneous hourly surface observations over China, this study documents the climatological means and evolutions in the diurnal cycles of Rd and Rf since 1993, with an emphasis on their implications for solar power and agricultural production. Over the solar energy resource region, we observe a loss of Rd which is relatively large near sunrise and sunset at low solar elevation angles when the sunrays pass through the atmosphere on a longer pathway. However, the concentrated Rd energy covering an average 10‐hr period around noon during a day is relatively unaffected. Over the agricultural crop resource region, the large amounts of clouds and aerosols scattering more of the incoming light result in Rf taking the main proportion of Rs during the whole day. Rf resources and their fertilization effect in the main crop region of China further enhances since 1993 over almost all hours of the day. Key Points: The loss of direct radiation over China since 1993 is relatively large at sunrise and sunset with little effect on solar power generationThe diffuse component dominates solar radiation normally near sunrise and sunset, but for the whole day over the main sown area of ChinaThe diffuse fraction is further enhanced in the main sown area of China over almost all hours of the day since 1993 [ABSTRACT FROM AUTHOR]

Pan evaporation decrease has been reported worldwide over the past decades. A recent increasing pan evaporation trend has been found globally. Remarkably, most studies on Chinese pan evaporation change were based on simulations involving meteorological variables, including temperature, radiation (sunshine duration [SSD]), wind speed, and relative humidity (RH), due to the pan evaporation observation inconsistency caused by the micro‐pan (D20) replacement with large pan (E601) around 2002. In addition, a large‐scale humidity sensor replacement across China occurred since the 2000s can cause an inconsistency of RH and in turn lead to that of simulated pan evaporation. Therefore, the recent pan evaporation trends independent of the observed RH in China should be revisited. In this study, we (a) generate merged D20 pan evaporation from 1988 to 2017 according to E601 observations under the constant conversion coefficient assumption between the evaporation observations of these pans in the same month of every year at each station, and (b) propose a framework based on the PenPan‐D20 model to attribute pan evaporation change into specific humidity (instead of RH or vapor pressure deficit in previous studies), SSD, air temperature, and wind speed, since RH and vapor pressure deficit are not independent from air temperature. The results show a significant 2.68 mm/a/a upward pan evaporation trend (p < 0.05) across China from 1988 to 2017, which was primarily driven by the rising air temperature. Humidity sensor replacement causes an ∼2.2% inconsistency in RH, which produces nonnegligible errors in simulated pan evaporation trend. Key Points: We generated a long‐term merged D20 pan evaporation series from 1988 to 2017Pan evaporation across China exhibits a 2.68 mm/a/a increasing trend from 1988 to 2017 and is dominated by the rising air temperatureAn ∼2.2% inconsistency occurs owing to the replacement of relative humidity sensors since the 2000s across China [ABSTRACT FROM AUTHOR]

It is important to understand the hydroclimate history of water‐deficient regions, such as the Alxa desert of northwest China. However, there are few high‐resolution proxy records for the hydroclimate changes over the past centuries in the Alxa desert. Fortunately, there are many tree‐ring hydroclimate reconstructions from the nearby mountains. However, the hydroclimate correlations between the Alxa desert and adjacent mountains are unclear. Here, we collected high‐quality data from 43 meteorological stations in northwest China (1960–2017). We found increasing mean temperatures in the study area, both on seasonal and annual timescales. We also found that while relative humidity had mostly decreased in the Mt. Qilian and Alxa desert, precipitation and the standardized precipitation evapotranspiration index (SPEI) increased mostly. In the Mt. Helan and Hasi ranges, relative humidity, precipitation, and SPEI all showed decreasing trends. Empirical orthogonal function analysis indicated that precipitation, relative humidity, and SPEI in the Mt. Qilian were similar to the corresponding conditions in the central and western Alxa desert. Hydroclimate conditions in the Mt. Helan and Hasi ranges were correlated with data from the eastern desert. Tree‐ring records of precipitation and SPEI from the mountains were used to validate the hydroclimate correlations during the instrumental period. We found strong similarities between hydroclimatic changes in the Mt. Qilian and those in the central and western Alxa desert, on both annual and decadal timescales, from 1877 to 2006. Tree‐ring width chronologies from mountainous areas were shown to faithfully represent the hydroclimatic history of the desert area. Plain Language Summary: Northwestern China has faced serious ecological challenges over the past five decades, including intensified desertification and declining lake levels. Understanding the regional hydroclimate history is necessary to manage water resources in this water‐deficient region. However, there are few climate proxies for these desert areas. In contrast, high‐resolution tree‐ring climate proxies have been studied intensively in the nearby mountains. This study attempts to find reliable correlations between mountain and desert hydroclimate. We found increasing mean temperatures over the entire study area. We also found that precipitation, relative humidity, and drought index data from the western and central desert were strongly correlated with data from Mt. Qilian, while data from the eastern desert were correlated with those from the Helan and Hasi mountain ranges. When relative humidity decreased mostly in the Mt. Qilian, precipitation and SPEI mostly increased; in the Mt. Helan and Hasi areas, relative humidity, precipitation and SPEI mostly decreased. Tree‐ring records from the mountains were compared to validate these correlations. Significant correlations were found between the precipitation reconstructions from the central desert and Mt. Qilian from 1877 to 2006. We also used tree‐ring width chronologies to show that they could represent the hydroclimatic history of the Alxa desert. Key Points: Precipitation and SPEI indicate wetter trends in Mt. Qilian but drier trends in Mt. Helan and Hasi ranges from 1960 to 2017Precipitation, relative humidity, and SPEI in western and central (eastern) Alxa desert resemble conditions in Mt. Qilian (Helan and Hasi)Tree‐ring proxies from nearby mountains can faithfully represent the hydroclimate history of the Alxa desert [ABSTRACT FROM AUTHOR]

This study quantifies the influences of climate variation and vegetation greening on the changes in evapotranspiration (ET) over 110 humid catchments of China from 1982 to 2016. A process‐based model considering climate and vegetation changes is employed to estimate ET. The simulated ET compared well with the observed values based on the flux measurements and water balance equation, with the coefficients of determination above 0.62. During the study period, environmental change of the study area was characterized by the increases in air temperature and leaf area index, that is, climate warming and vegetation greening. Annual ET increased at 104 catchments with the trends ranging from 0.01 to 6.2 mm yr−2. The numerical experiment approach and sensitivity method are used to attribute ET changes to climate variation and vegetation greening. The results show that the contributions of climate variation to ET changes estimated by the two methods are 90.6% and 91.3%, respectively, whereas the contributions of vegetation greening to ET changes are only 9.4% and 8.7%, indicating that climate variation controls ET changes in the study area. However, vegetation greening alters the proportions of ET components, which contributes 59.0%–62.0% to the increase in the ratio of transpiration to ET. This study quantifies the roles of climate and vegetation changes in the dynamics of ET, suggesting that more concerns should be paid on the interactions between ecological processes and hydrological cycle in humid regions. Key Points: Evapotranspiration changes are attributed to climate variation and vegetation greening over 110 humid catchments in ChinaClimate variation controls the dynamics of evapotranspiration over the humid regionVegetation greening has limited influences on evapotranspiration but mainly alters evapotranspiration partitioning [ABSTRACT FROM AUTHOR]

Increasing energy and food demands require an understanding of not only the availability and variability of total solar radiation (R) but also its partitioning into direct (Rd) and diffuse (Rf) components, which are key elements for solar power generation and plant photosynthesis, respectively. Potential inhomogeneities in surface solar radiation observations, however, add uncertainties to the published patterns and trends of Rd and Rf over China. To exclude inhomogeneous time series and outliers, a data quality control process has been applied to the surface observations of Rd and Rf. The homogeneous data show that, in response to the global dimming and brightening phenomena in R, decadal changes can also be observed in the Rd and Rf trends over China with the actual transition occurring in the mid‐2000s. Since the 1960s, Rd dimming has mainly distributed over eastern China with intensive anthropogenic activities, with recoveries especially from 2008 onward over regions with high Rd energy potential. Rf, on the other hand, had further enhanced since the 1960s especially over the high Rf proportion areas but has decreased in the recent decade over the northern region. The summer season shows the most significant decadal trends in Rd and Rf. Under clear‐sky conditions, that is, ruling out cloud effects, the transitions in Rd and Rf trends become more remarkable, pointing to atmospheric aerosols as the main driving force. In addition, dramatic Rd and Rf variations are observed in the subsequent years after large volcanic eruptions. The varying Rd and Rf proportions are in line with recent governmental control on SO2 emissions over China. Key Points: Homogeneous observations show a recent transition to brightening in direct radiation and to dimming in diffuse radiation over China since 2008Clear‐sky trends suggest an impact of volcanic eruption on the dramatic changes in solar radiation over China during the early 1990sGovernmental control on pollutant emissions may have contributed to the variations of direct and diffuse radiation proportions over China [ABSTRACT FROM AUTHOR]

Having recognized the limitations in spatial representativeness and/or temporal coverage of (i) current ground ETa observations and (ii) land surface model‐ and remote sensing‐based ETa estimates due to uncertainties in soil and vegetation parameters, a calibration‐free nonlinear complementary relationship (CR) model is employed with inputs of air and dew‐point temperature, wind speed, and net radiation to estimate 0.1°, monthly ETa over China during 1982–2012. The modeled ETa rates were first validated against 13 eddy‐covariance measurements, producing Nash‐Sutcliffe efficiency values in the range of 0.72–0.94. On the basin scale, the modeled ETa values yielded a relative bias of 6%, and a Nash‐Sutcliffe efficiency value of 0.80 in comparison with water‐balance‐derived evapotranspiration rates across 10 major river basins in China, indicating the CR‐simulated ETa rates reliable over China. Further evaluations suggest that the CR‐based ETa product is more accurate than seven other mainstream ETa products. The 31‐year mean annual ETa value decreases from the southeast to the northwest in China, resulting in a country average of 406 ± 15 mm/year. The country‐representative annual ETa rates slightly decreased with a rate of −0.5 mm/year (p = 0.86) during 1982–2012. Annual ETa increased significantly over most parts of western and northeastern China but decreased significantly in many regions of the North China Plain as well as in the eastern and southern coastal regions. The present CR‐based method, with its calibration‐free nature and minimal data requirement, could help future calibrations/verifications of the more complex and more data‐intensive land surface model‐ and remote sensing‐based models. Key Points: Development and validation of a monthly, 0.1‐degree ETa data set (1982–2012) for China by the latest complementary relationshipThe new ETa data require only basic meteorological variables and are more accurate than seven previously available ETa productsETa increased significantly in most parts of western and northeastern China, but opposite trends occurred in the North China Plain and eastern and southern China [ABSTRACT FROM AUTHOR]

The MODerate‐resolution Imaging Spectroradiometer (MODIS) provides spatially contiguous measurements of terrestrial biophysical variables, which can be used to estimate the terrestrial latent heat flux (LE). MODIS‐derived shortwave infrared reflectance (SWIR) metrics (SWIRs) are sensitive to the soil moisture and vegetation water stress. In this study, we used the MODIS‐derived SWIRs with eddy covariance flux measurements obtained from 25 flux tower sites representing 10 different land cover types within China to evaluate the sensitivity of SWIRs to ground‐measured evaporation fraction and LE. The water constraint metrics determined using the MODIS‐derived SWIR generally corresponded better with the ground‐measured evaporation fraction values than those obtained without using SWIR. The MODIS‐derived SWIRs were used as proxies for the soil and vegetation water supply constraints in a revised Priestley‐Taylor algorithm to estimate the terrestrial LE. The estimated LE using the MODIS‐derived SWIRs generally corresponded well with the ground‐measured LE (0.56 ≤ R2 ≤ 0.97) for most of the flux tower sites. Regional algorithm sensitivity analysis using the MODIS‐derived SWIRs as water supply proxies demonstrated that water limitations reduce LE by more than 53% over China, and the atmospheric vapor pressure deficit and relative humidity are not sufficient to characterize both the atmosphere demand and water supply for LE estimation. Our results demonstrate the potential of using MODIS‐derived SWIRs to characterize soil and vegetation water supply factors for determining LE, where the relatively high spatial and temporal resolutions (500 m and daily) are closer to the scale of the eddy covariance ground measurements. Key Points: MODIS‐derived SWIR corresponded better with EF than those without using SWIRMODIS‐derived SWIRs were used as proxies for water supply to estimate LEMODIS‐derived SWIR can be used to detect the impacts of water stress on LE [ABSTRACT FROM AUTHOR]