- 期刊
GPS估計可降水量：WVR約束法
Precipitable Water from GPS: A WVR Constraint Approach
摘要
本文應用中央氣象局（Central Weather Bureau；CWB）台北及花蓮氣象站，從民國87年3月18日至25日所蒐集的全球定位系統（Gobal Positioning System；GPS）、氣球探空、雙頻水氣輻射計（Water Vapor Radiometer；WVR）和地面逐時氣象觀測資料，以WVR觀測約束GPS觀測，估計可降水量。在僅有台北站設有一套WVR的情況下，GPS估計可降水量主要步驟有四：1.應用科學軟體Bernese 4.0處理GPS資料，求解台北和花蓮兩個氣象站大氣相對濕遲延量；2.使用WVR觀測估計台北站絕對濕遲延量；3.比較台北站GPS和WVR濕遲延量，來計算GPS濕遲延補償量；4.以補償花蓮氣象站GPS濕遲延量，來估計絕對濕遲延量，並且由此求出可降水量。結果顯示，GPS計算出的花蓮站濕遲延量、可降水量的平均值（標準差）分別為22.7（3.30）、3.72（0.55）cm，對應的氣球探空觀測分別為24.9（2.99）、4.04（0.50）cm。由於兩種異質觀測的時、空解析度截然不同，GPS較氣球探空觀測低估濕遲延量、可降水量分別為2.16、0.32cm。
並列摘要
This paper presents observations of Precipitable Water (PW) from Global Positioning System (GPS). GPS, radiosonde, Water Vapor Radiometer (WVR), and hourly surface meteorological observations collected at Central Weather Bureau's (CWB) Taipei and Hualien weather stations from March 18 to 25, 1998, were utilized. The only WVR was installed at the Taipei site. Four major procedures are proceeded to derive PW from GPS data. First, Bernese GPS Software version 4.0 was used to estimate relative wet delay over the Taipei and Hualien sites. Second, absolute wet delay was determined from WVR at the Taipei site. Third, offset in wet delay was computed by subtracting GPS-from WVR-observed wet delay at the Taipei site. Fourth, wet delay derived from GPS data at the Hualien site was compensated by the offset to determine absolute wet delay, and PW given surface meteorology. It is found that the averages (standard deviations) of GPS-derived wet delay and PW are 22.7 (3.30) and 3.72 (0.55) cm, respectively. The corresponding observations from radiosondes are 24.9 (2.99) and 4.04 (0.50) cm, respectively. Since the two kinds of instruments are distinctive in terms of their measuring characteristics in time- and spatial-resolutions, GPS observations underestimate wet delay and PW by 2.16 and 0.32 cm, respectively.