Search

The synchronicity of rain and heat in the summer of China's monsoon region provides sufficient water and heat resources for maize growth. However, the intra-annual distribution of precipitation and the probability of extreme precipitation have been inevitably altered by the ongoing climate change, thus affecting the matching degree between precipitation and crop water requirements (MDPCWR). Evaluating the extent to which the MDPCWR will change in the future is of great importance for food security and the sustainable management of water resources. In this study, considering that different growth stages of crops have different sensitivities to water stress, the AquaCrop model was used to calculate the MDPCWR more accurately. In addition, a cumulative distribution function-transform (CDF-t) method was used to remove the bias of 11 global climate models (GCMs) under two typical emission scenarios (SSP2-4.5 and SSP5-8.5) from phase six of the Coupled Model Intercomparison Project (CMIP6). A comprehensive investigation was conducted on how maize growth, water consumption, and the MDPCWR will respond to future climate change with CO2 concentration enrichment in the Huang–Huai–Hai (3H) region in China by driving a well-tested AquaCrop model with the bias-corrected GCMs outputs. The results indicate the following: (1) The CDF-t method can effectively remove seasonal bias, and it also performs well in eliminating the bias of extreme climate events. (2) Under the SSP2-4.5 scenario, the average maximum temperature will increase by 1.31 °C and 2.44 °C in 2021–2050 and 2051–2080, respectively. The average annual precipitation will increase up to 96.8 mm/year, but it will mainly occur in the form of heavy rain. (3) The increased maize evapotranspiration rate does not compensate for the decreased crop water requirement (up to −32 mm/year), due to a shorter growth cycle. (4) The farmland cultivation layer is not able to hold a significant amount of precipitation, due to the increased frequency of heavy rains, resulting in increased irrigation water requirements for maize over the next two periods, with the maximum value of 12 mm/year. (5) Under different scenarios, the projected future MDPCWR will decrease by 9.3–11.6% due to changes in precipitation patterns and crop water requirements, indicating that it will be more difficult for precipitation to meet the water demand of maize growing in the 3H region. The results can provide comprehensive information to understand the impact of climate change on the agricultural water balance and improve the regional strategy for water resource utilization in the 3H region. [ABSTRACT FROM AUTHOR]

As the only connecting term between water balance and energy budget in the earth-atmospheric system, evapotranspiration ( ET ) is considered the most excellent indicator for the activity for the water and energy cycle. Under the background of global change, regional ET estimates, components partitioning as well as their spatial and temporal patterns recognition are of great importance in understanding the hydrological processes and improving water management practices. This is particularly true for the Tibetan Plateau (TP), one of most sensitive and vulnerable region in response to the environment change in the earth. In this study, with flux site observation data and monthly ET data from the monthly water balance method incorporating the terrestrial water storage changes from the Gravity Recovery and Climate Experiment satellite (GRACE) production as the multiple validations, the long-term daily ET in the TP was retrieved by a modified Penman-Monteith-Leuning (PML) model with considering evapotranspiration over snow covered area during 1982–2012. The spatial and temporal changes of partitioned three components of ET , i.e., soil evaporation ( E s ), transpiration through the stomata of plant ( E c ) and canopy interception ( E i ), were investigated in the TP. Meanwhile, how the ET components contribute to ET changes and respond to the change in environmental factors in the TP was revealed and discussed. The results indicate that E s dominates ET in most areas of the TP with the mean annual ratio of 65.7%, except southeastern regions where the vegetation coverage is high. Although regional average ET and three main components all present obvious increase trends during the past decades, high spatial heterogeneity for their trends are identified in the TP. Moreover, a mixed changing pattern can be apparently found for E s in southeastern area, E c and E i in northwestern and southeastern area. Spatially, the ET variation are mainly attributed to change in E s , followed by E c and E i . In addition, compared with evaporation-related meteorological variables, precipitation and leaf area index (LAI) provide the more dominated contributions to the changes of ET and E i in the TP, while LAI is overwhelming contribution factor for E c changes. As for E s changes, although precipitation play the important role, the effects of other factors are also non-negligible. [ABSTRACT FROM AUTHOR]

• A combined subgrid-scale irrigation scheme is incorporated into WRF model. • The climatic effects of irrigation in grid and subgrid scale are evaluated. • Summer irrigation cooling effects reduce warm bias in surface air temperature. • Irrigation impacts local/remote precipitation by altering large-scale circulation. Characterizing climatic effects of agricultural irrigation is of great importance and challenging to understand the full influence of water management on the Earth's environment and hydroclimatic cycle. The investigation of the local and remote climatic responses to irrigation in the middle and lower reaches of the Yangtze River (MLRYR), a typical humid region, was previously unidentified. A novel combined subgrid-scale irrigation scheme for wheat (dynamic irrigation) and rice (fixed irrigation) was developed and incorporated into the Weather Research and Forecasting (WRF) modeling framework. The comprehensive climatic effects on energy balance, temperature, precipitation and the planetary boundary layer, were assessed by numerical experiments with irrigation off/on for ten crop growth seasons from 2007 to 2016. Both the simulated irrigation amounts of wheat and rice were generally in agreement with actual values. Surface energy and water budgets have been substantially altered by irrigation, and the magnitudes were dependent on the irrigation amounts. Irrigation increased latent heat flux and reduced sensible heat flux, especially during summer. The warm bias in the simulation without consideration of irrigation was reduced by the cooling effects of irrigation. The mean surface air temperature decreased significantly by 0.12–0.24 °C and 0.4–0.8 °C for spring and summer, respectively. Meanwhile, irrigation presented stronger cooling effects on daytime temperature than nighttime temperature, resulting in the reductions of diurnal temperature range in irrigated area. Moreover, the irrigation-induced increase of geopotential height and anomalous anticyclones led to the decreases in precipitation over the MLRYR. The changes of precipitation in remote areas were generally related to the irrigation induced large-scale circulation change. Furthermore, although the climatic effects of irrigation in grid scale were not relatively high due to the relatively low irrigation fraction, they exhibited apparently stronger in the subgrid scale, which can be used to investigate the impacts of climatic effects of irrigation on crop growth. [ABSTRACT FROM AUTHOR]