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【Background】 Latent heat flux (LE) impacts carbon dynamics and energy budget in the terrestrial ecosystem. Its accurate estimation is essential to understanding energy budget and surface-atmosphere interactions on the Earth surface. Satellite imageries have been used to calculate LE at global scale, but most of them overlooked the impact of vegetation diversity at pixel scale. 【Objective】 Considering that carbon flow and heat flux in ecosystems are closely related through photosynthesis and that plants are diverse, calculating LE using sub-pixel data should improve its accuracy, especially for complex ecosystems. 【Method】 Here, a dynamic vegetation model, LPJ-GUESS, was proposed to improve the satellite-based PT-hybrid algorithm, by using a parameter fv to represent the proportions of different PFTs in a pixel. 【Result】 Validation against ground-true data obtained from 49 flux tower sites in the world showed that the proposed model increased the square of correlation coefficient from 0.63 to 0.74, and reduced the root mean square error from 17.1 W/m2 to 11.7 W/m2. Estimation of the global LE from 1982 to 2014 revealed the proposed method was more effective for low latitude areas than for other areas, and that for areas on the same latitude, the LE showed complicated spatial distribution. 【Conclusion】 Sub-pixel method was coupled with the LE algorithm for the first time to calculate surface latent heat flux. It significantly improved the accuracy and can be used to estimate spatiotemporal distribution of LE at different scales.

This study investigated the change in precipitation concentration due to global warming based on the output of one experiment (a scenario of 1% CO2 increase per year) from 12 general circulation models provided by the Coupled Model Intercomparison Project Phase 5 (CMIP5). Two different indices were used to describe precipitation concentration: (a) concentration index (CI), which measures the evenness of total precipitation on wet days, and (b) precipitation concentration degree (PCD), which measures the evenness of the annual precipitation distributions over time. We found that widespread increases in CI were distributed over all land areas except for some arid areas, indicating a less uniform distribution of precipitation on wet days in a warming climate caused by CO2 increasing. We also found that the spatial patterns of changes in PCD are complex, with large regional differences. All of the results suggest a global‐scale readjustment of precipitation distribution in magnitude and timing. This kind of readjustment may have significant impacts on climatic and hydrological events and thus cause severe ecological and environmental damage. [ABSTRACT FROM AUTHOR]

As one of the most influential oceanic and atmospheric oscillations in the Earth system, El Niño‐Southern Oscillation (ENSO) has modulated numerous geophysical processes. This is particularly true for the Yangtze River Basin (YRB), which is vulnerable to Asian Monsoon and faces serious hydrological hazards. In this study, the co‐variability between lag–lead precipitation and sea surface temperature anomalies was evaluated utilizing singular value decomposition (SVD) method. Moreover, certain teleconnections between ENSO and streamflow were identified by wavelet methods. In addition, the contribution of related atmospheric variables was revealed by composite analysis. Results indicate that there are strong associations in lag–lead seasons between the wet condition (dry condition) and September–November (December–February) mature ENSO phase. Significant common power and coherence signals between the ENSO indices and the streamflow occur in the 4–8, 8–16 and 16–32 seasonal scales. Meanwhile, the activity cycle of the ENSO indices ahead of streamflow increases from the mid‐lower reaches to the source region. In addition, the Western Pacific Subtropical High is strengthened during the mature ENSO phase. Anomalous sinking motions and divergent water vapour flux occupy the YRB, reducing the precipitation and leading to the dry condition in the source region until the following March–May. On the other hand, ascending movements and abundant water vapour flux coming from northern Pacific, equatorial western Pacific and the Bay of Bengal result in the wet condition in the mid‐lower reaches. [ABSTRACT FROM AUTHOR]

Reference evapotranspiration (ET0), which is an indicator of atmospheric evaporation demand over a hypothetical reference surface, is expected to alter along with global climate change. In this study, the changes and driving forces of historical ET0 and its future projections in Xinjiang, China, were comprehensively conducted. The trend analysis revealed that regional ET0 decreased significantly at a rate of −4.1 mm/year2 during 1961–1993 and increased at a rate of 3.4 mm/year2 during 1994–2010. To explore the possible causes, the contributions of major climatic variables to the ET0 trends were derived based on the differential equation method. During 1961–1993, the decreasing trend of ET0 was primarily ascribed to the wind speed. The integrated negative effect from the decrease in wind speed (U) and increase in relative humidity (RH) was more significant than the positive effect from the increase in air temperature (T), resulting in the decrease in ET0. During 1994–2010, combined with increasing T and decreasing RH, the increase in U offset the effect of the net radiation (Rn) decrease and led to an increase in ET0. Future ET0 projections over three periods (2010–2039, 2040–2069, and 2070–2099, which are named as 2020s, 2050s, and 2080s, respectively) were conducted based on the general circulation models under two representative concentration pathways scenarios (RCP4.5 and RCP8.5). A continuous increasing trend in ET0 was demonstrated in the 21st century. The increase in ET0 will increase the irrigated water resource consumption and bring new challenge to water resource management in this area. [ABSTRACT FROM AUTHOR]

Future changes in reference evapotranspiration (ET0) are of increasing importance in assessing the potential impacts on hydrology and water resources systems of more pronounced climate change. This study assesses the applicability of the Statistical Downscaling Model (SDSM) in projecting ET0, and investigates the seasonal and spatial patterns of future ET0 based on general circulation models (GCMs) across the Haihe River Basin. The results indicate that SDSM can downscale ET0 well in term of different basin-averaged measures for the HadCM3 and CGCM3 GCMs. HadCM3 has a much superior capability in capturing inter-annual variability compared to CGCM3 and thus is chosen as the sole model to assess the changes in future ET0. There are three homogeneous sub-regions of the Haihe River Basin: Northwest, Northeast and Southeast. Change points are detected at around 2050 and 2080 under the A2 and B2 scenarios, respectively. The Northwest is revealed to have a slight to strong increase in ET0, while the Northeast and the Southeast tend to experience a pattern change from decrease to increase in ET0. EDITOR M.C. Acreman ASSOCIATE EDITOR J. Thompson [ABSTRACT FROM AUTHOR]