Characterization of droughts during 2001–2014 based on remote sensing: A case study of Northeast China

Northeast China, the most important region for commercial grain farming in China, is vulnerable to drought due to high fluctuation in monthly rainfall. Timely, accurate and effective drought monitoring is very essential for securing the output of grain farming. In this study, three widely used drought indices were compared using satellite soil moisture data and their capability for drought monitoring was evaluated in Northeast China. Three indices are Normalized Monthly Precipitation Anomaly Percentage (NPA), Vegetation Health Index (VHI) and Normalized Vegetation Supply Water Index (NVSWI). In order to know the relationship between rainfall and drought especially over different local climate zones and give a more detail strategy for crop irrigation, a time-lag relationship is investigated based on the TRMM 3B43 monthly precipitation and NVSWI. Tendency rate (slope) was used to characterize the change of drought events in the region for the period 2001–2014. Results showed that: (1) the three selected indices were suitable for drought monitoring, with NVSWI performing the best in terms of the highest correlation with soil moisture, (2) an obvious time-lag was observed between rainfall and drought with the time lag being one month for all three climate zones, (3) drought occurred more frequently in spring and winter, while in summer drought occurred more easily in the west than in the east in Northeast China, (4) overall the frequency of drought was decreasing from 2001 to 2014 in Northeast China.