Spatiotemporal change and trend analysis of potential evapotranspiration over the Loess Plateau of China during 2011–2100

Abstract

The spatiotemporal change and trend of annual potential evapotranspiration (PET) over the Loess Plateau of China from 2011 to 2100 are assessed in this work. PET is calculated using the Hargreaves model with monthly mean, maximum, and minimum temperatures and a 1km spatial resolution, which are generated using the Delta downscaling method and general circulation models (GCMs) with four representative concentration pathway (RCP) scenarios. The PET trend is detected via Mann–Kendall and Sen’s slope estimator tests. The following results are drawn: (1) the Delta downscaling method shows a favorable performance in detecting GCM monthly temperatures based on the mean absolute error and regression analysis between downscaled data and independent surface observations. Among the 28 GCMs, the NorESM1-M and GISS-E2-R models show the best performance in reproducing the monthly mean/maximum and minimum temperatures over the Loess Plateau, respectively; (2) the average annual PET over this region will increase by 12.7%–23.9% from 1961 to 1990 to the end of this century (2071–2100). However, these increments show strong spatial variations; (3) the annual PET during the 2011–2100 period at each grid of the region demonstrates a significantly increasing trend under each RCP scenario, while RCP2.6, RCP4.5, RCP6.0, and RCP8.5 have average magnitudes of trend of 10.4mm/10yr, 17.7mm/10yr, 21mm/10yr, and 29.7mm/10yr, respectively; (4) the annual PET with significant trends during the other three periods (2011–2040, 2041–2070, and 2071–2100) present various spatial distributions in their magnitudes of trend under the aforementioned RCP scenarios. RCP2.6 showed a significant decrease during 2041–2070 and 2071–2100, although such trends are only observed at 0.3% and 1.2% of the Loess Plateau, respectively; and (5) the spatial results provide some information, such as locations and area ratios, which are valuable in assessing future PET changes and trends. These spatiotemporal results represent the PET changes and trends in detail and provide insights for developing flexible adaptation and mitigation strategies to combat the effects of global warming in this region.