- 期刊
地面微波輻射偵測大氣中可降水量之動態
Ground-Based Radiometric Sensing of Atmospheric Dynamics in Precipitable Water Vapor
摘要
我們利用水氣微波輻射儀（Water Vapor Radiometer；WVR）觀測大氣中的可降水量（Precipitable Water Vapor；PWV）及液態水（Cloud Liquid Water；CLW）路徑總含量，並以觀測結果說明其動態。觀測資料乃於民國八十七年三月十八日到二十五日間在台北氣象站所蒐集，包含了23.8及31.4 GHz兩種頻率的亮度溫度（亮溫）。觀測時水平角設定在東西及南北走向兩方向轉換，仰角則設定在15°（北╱東）及165°（南╱西）間，每15°做一次觀測。水氣微波輻射儀觀測結果顯示，在天頂方向（仰角90°）可降水量變化範圍約由晴天的2.4 cm到陰雨天的6.5 cm，液態水則介於晴天的0 μm到陰雨天的7840 μm間。在仰角15°及165°間觀測結果顯示，成層化（stratified）大氣之假設，隨著仰角偏離天頂方向而逐漸失真。
並列摘要
Utilizing a ground-based, dual-channel water vapor radiometer (WVR), measurements on the integrated precipitable water vapor (PWV) and cloud liquid water (CLW) of the atmosphere were obtained. These two sets of data are used t describe atmospheric dynamics. They were inferred from WVR observations of the brightness temperatures and optical depths at 23.8 and 31.4 GHz collected at the Central Weather Bureau's (CWB) Taipei weather station on March 18-25, 1998. During the field campaign, the WVR was initially installed due east, but was turned north periodically. An elevation mirror was applied to guide the atmospheric emission to the receiver. It is designed to rotate perpendicularly to the WVR itself so that it can be automatically adjusted to scan the atmosphere every 15° at angles between 15° (north/east) and 165° (south/west). WVR observations show that the PWV has a variation from 2.4 cm for clear skies to 6.5 cm for cloudy/rainy conditions at zenith, while the CLW varies from 0 to 7840 μm for the corresponding situations. In other words, atmospheric dynamics in PWV and CLW are clearly observable. In addition, PWV and CLW observations at angles from 15° to 165° indicate that the stratified atmosphere becomes a less appropriate assumption with angles departing from zenith.