Baoqing Zhang
College of Water Resources and Architectural Engineering, Northwest A&F University

In this study, we analyzed the spatial and temporal trends of climatic change during the main growing season for vegetation between 1970 and 2010 on the Loess Plateau. To accomplish this, we created a new multimodal wherein we combined the Variable Infiltration Capacity model for simulating watershed hydrological processes and PDSI for climatic change detection and estimation. The simulation results and the grids system of VIC were applied to substitute for the two-layer bucket-type model to do the hydrological accounting, which greatly improved the physical mechanism of PDSI and expanded its application range. Our results suggested that the climate of the study area has experienced a drying and warming trend during the past four decades, particularly in spring. Except for some individual years and regions, there was a perpetuation of water deficit over the Loess Plateau both in spring and summer. The spatial distribution of drought frequency increased from southeast to northwest on the Loess Plateau in spring, while drought frequency in summer decreased from southeast to northwest. The climate in the southern part of the Loess Plateau, which accounts for 23.3% of the study region, showed a significant drying and warming trend in spring over the past four decades. Since a large part of the study region frequently suffered from water deficiency during main growing season, people living in such drought-prone areas should take measures to prevent the adverse effect of drought on agricultural production and regional food security.