Detecting Droughts in Southwest China from GPS Vertical Position Displacements

Abstract

The solid Earth responds elastically to terrestrial water storage (TWS)changes. Here global positioning system (GPS) vertical position data at 31 stations from the crustal movement observation network of China (CMONOC) from August 2010 to December 2016 are used to detect droughts in Southwest China. Monthly GPS vertical position displacements respond negatively to precipitation changes and TWS changes observed by gravity recovery and climate experiments(GRACE) as well as river water level variations. GPS vertical position anomalies (the non-seasonal term) are well correlated negatively (correlations of about -0.70) with the commonly used meteorological composite index (CI) in China and the GRACE drought severity index (GRACE-DSI),but less correlated with the standardized precipitation evapotranspiration index (SPEI). Compared to CI, GPS vertical position anomalies have the advantage of detecting droughts caused by abrupt precipitation deficits in a short time. GRACE-DSI is less accurate in drought monitoring for some periods due to the missing data, while the severity of abrupt precipitation absent in some cases can be overestimated from SPEI with big variability. This study shows the reliability and advantages of GPS data in drought monitoring.

Keywords

• |gps vertical displacement|terrestrial water storage|grace|drought