利用GPS垂向位移监测西南地区干旱事件

GPS垂向位移包含了陆地水储量变化引起的地球弹性形变信息。本文利用中国大陆构造环境监测网(陆态网)31个GPS台站2010年8月—2016年12月的垂向位移数据,分析我国西南地区的干旱事件。结果表明,GPS垂向位移的季节性变化与降雨、GRACE反演的水储量、河流水位变化具有较强的负相关关系,其异常变化(非季节性变化)与我国使用的综合气象干旱指数(CI)、GRACE干旱强度指数(GRACE-DSI)相关性较强(相关系数约为-0.70),而与标准化降水蒸散指数(SPEI)的相关性较弱。相比于CI干旱指数,GPS垂向位移能更好地探测短期降雨急剧减少引起的干旱事件。数据缺失影响了GRACE-DSI探测干旱的准确性,而SPEI的波动较大,且存在高估某些短期降雨严重性的情况。研究结果展示了GPS在干旱监测方面的可靠性和优势。

Detecting droughts in Southwest China from GPS vertical position displacements

The solid Earth responds elastically to terrestrial water storage (TWS) changes. Here global positioning system(GPS)vertical position data at 31 stations from 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 experiment(GRACE) as well as river water level variations. GPS vertical position anomalies (the nonseasonal 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 in detecting droughts caused by abrupt precipitation deficits in a short time period. 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.