华西秋雨天气过程中GPS遥感水汽总量演变特征

利用成都地区地基GPS观测网2007年9-11月的观测数据, 结合自动气象站资料计算出30 min间隔GPS遥感的大气水汽总量(GPS-PWV)。将成都地区秋季降雨分为阵性降雨和连续性降雨(秋绵雨), 结合其他气象要素资料, 分析了GPS-PWV变化与成都秋雨之间的关系。结果表明:高值的水汽总量是产生降水的必要条件; 不同的降水过程, GPS-PWV的变化幅度、极值水平和持续时间存在明显差异。水汽的增长、上升运动的增强和温度的减少是造成阵性降水的主要原因; 而秋绵雨过程中, 水汽的增长和地面露点温度差与降水过程有较好的对应关系。

The Evolution Features of Precipitable Water Vapor Derived from Ground based GPS During Autumn Rain Weather Process in West China

Based on the principle of deriving precipitable water vapor with ground-based GPS,the estimates of total zenith delay are calculated using ZTD data from the ground-based GPS network in Chengdu Plain during the period of September to November 2007.Precipitable water vapor (PWV) derived from GPS are obtained at 30-minute interval combining meteorological data from automatic weather stations.The autumn rain is classified as showery rain and continuous precipitation in Chengdu Plain,and the relationship between GPS-PWV and autumn rain is analyzed.It shows that precipitation always happens in high value phase of water vapor,so the high precipitable water vapor is necessary for rain in most cases.Precipitation happen when the PWV anomaly is positive,and the PWV anomaly is always higher than 1 when a rainstorm occurs.The variation range of showery in autumn is large.The GPS-PWV always increases 12 hours before the precipitation.When GPS-PWV is higher than the base value of the month or acutely increases in the adjacent time,a shower is likely to occur.High GPS-PWV level and weak updrafts just lead to small rain.But the increasing of precipitable water with strong ascending motion and the decreasing of temperature always causes shower.During continuous precipitation in autumn in Chengdu Plain,the accumulation of water vapor is very important,strong precipitation often happens when water vapor rises once again.If the precipitable water vapor maintains the high level,it may rain within 12 hours.If the water vapor falls to the base value of the month then rise to above that within 12 hours,it indicates the beginning of another phase of precipitation.GPS-PWV variation range,extremum level and duration are different in different rain process.These results may be referential for applying precipiatable production derived from ground-based GPS network in precipitation forecast.