Analysis of meteorological drought characteristics in Beijing based on Standardized Precipitation Index

Standardized Precipitation Index(SPI) of all the selected stations at different time scales were calculated to analyze the annual trend of meteorological drought grade at different time scales, summarize the spatial distribution characteristics of meteorological drought frequency and SPI values of severe drought years, using monthly precipitation data of 20 rainfall representative stations in Beijing from 1956 to 2016. The results show that the yearly variation trend of 1-month and 3-month SPI values is consistent with the spatial distribution trend of drought frequency, meanwhile, the SPI values have the drastic fluctuation over time without obvious fluctuation cycle. The drought frequency decreases from northwest to southeast. The 12-month SPI values have a weaker fluctuation, and the drought frequency decreases from southeast and northwest to the central. The spatial distribution of SPI values in the above three time scales in 1999 and 2002 was consistent, among which the drought in 1999 showed a decreasing trend from southeast to northwest, and the drought in 2002 showed a decreasing trend from northeast to southwest.