大氣中，水的三態變化是影響天氣的主要動能，但是水氣分布極為不均，時空變化很大，因此監測大氣可降水量的變化是預測天氣非常重要的指標。近年來科學家利用GPS可在任何環境下進行全天候的監測可降水量（Precipitable Water），其已達高精度（2mm）成效。本研究採用2008年5、6月台灣上空條件相當的鄰近GPS站之資料，分析在劇烈天候下GPS測站周遭的環境特徵、地形與可降水量的關係。研究發現鄰近GPS測站於逐日同時刻可降水量變化一致，具有高度的正相關，顯示當地的水氣變化相同。若探討高程變化大的台灣中部五個GPS測站，則高度愈高，可降水量愈低。而緯度相當、距海岸遠近不同的GPS測站，發現位於都市且鄰近水域測站之可降水量比鄰近測站高。但位於較高測站之可降水量比鄰近的測站低；顯示出高程對於可降水量之影響比距水域遠近大。

Because the moisture at the atmosphere is not evenly distributed and its changes in time and space are greatly varied, therefore, observing the change of precipitable water at the atmosphere is a very important index in predicting the weather. In recent years, scientists can observe the change in precipitable water by using GPS in all environments, and it produces good results. This research used the data from selected Taiwan GPS stations and analyzed the relationships of precipitable water at the atmosphere for the GPS stations between different environments and topography. Our research indicates that the change of precipitable water for the GPS stations nearby has no difference at the same time period in one day, showing that the change of moisture is the same for the stations nearby. When discussing the five GPS stations in the central range of Taiwan, the more the height is, the lower the precipitable water becomes. It is found that if the GPS stations are located at cities and closer to the water districts, the precipitable water is higher, and the precipitable water is lower when the GPS stations are in higher elevations, showing that the height affects much more than the distance from the water districts.

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