Meteorological drought monitoring combined with GNSS precipitable water vapor and measured precipitation: a case study of GNSS stations in Hubei Province

The atmospheric precipitable water vapor (PWV) derived from Global Navigation Satellite System (GNSS) provides new data for monitoring meteorological disasters such as heavy rainfall. In this study, we constructed the monthly Precipitation Efficiency (PE) meteorological drought index from a comprehensive perspective of atmospheric water vapor and precipitation, based on daily PWV and precipitation data from five GNSS stations in Hubei Province during 2011-2022. The characteristics and advantages of the index was verified using Standardized Precipitation Index (SPI), Meteorological Drought Composite Index (MCI) and Standardized Precipitation Evapotranspiration Index (SPEI). The results are as follows. (1) The variation of atmospheric water vapor in Hubei Province has good spatial consistency, while precipitation has strong local variation characteristics. The correlation coefficients of PWV at five GNSS stations are all greater than 0.98, and the correlation coefficients of rainfall are between 0.66 and 0.90. A combination of these two factors could reflect the comprehensive variations in large-scale PWV and local precipitation. (2) PE index was well correlated with SPI, MCI and SPEI (correlations ranging from 0.56 to 0.85), indicating the effectiveness of PE. (3) The correlation coefficient of PE between GNSS stations (0.50~0.81) is the smallest among the four indexes, indicating that the PE meteorological drought index has the ability to reflect the difference of local drought characteristics. PE index indicates that Xiangfan was a high-frequency site of severe drought during 2011-2022. Drought events in Wuhan site frequently occurred in autumn season and lasted a long time. Results confirmed the effectiveness and advantages of the drought indices constructed from GNSS PWV in characterizing drought evolution and spatial distribution.