可降水量的變化及掌握，對從事大氣研究方面來說，是一項非常重要的課題。當一些氣象事件例如降雨及颱風的發生，皆與可降水量的變化息息相關。
本研究利用不同儀器觀測可降水量的變化作探討與比較，分別討論以下四個主題：逆溫、逆濕的影響、反演可降水及液態水的分佈情形、仰角及方位角的變化及GPS、WVR和RAOBs( Radiosonde Observation )三者之間的比較。其中，逆溫、逆濕造成的大氣不穩定性，間接影響到WVR及GPS觀測可降水量的反演係數。而不同仰角的觀測，因相應的光程改變，PW及LWP會有變化。至於不同方位的觀測會受到區域天氣的影響，而GPS、WVR及RAOBs等三種觀測儀器，特徵差異大。
觀測結果中發現，利用WVR與GPS觀測可降水量的分析，是一項可行的技術。且能有效的改善氣球探空在時間解析度上的不足，而在不同月份上的觀測，可看出季節對可降水量的影響。另外，經由降雨事件的過濾排除，可降低WVR觀測時的差異。

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