SoWMEX/TiMREX 實驗期間無線電探空系統比對校驗及應用

Abstract

本研究探討2008年4月15、16日和2008年10月4、5日與11、12日在板橋探空測站所舉行的三種探空儀交叉比對的實驗結果，並應用於SoWMEX/TiMREX實驗中東沙島探空資料的時間序列分析，以了解該實驗期間南中國海地區之大氣剖面的變化。 參與SoWMEX/TiMREX實驗中的其中三種探空儀─Graw DFM-06、Vaisala Radiosonde RS92-SGP、Meisei RS2-80，個別搭載了不同的感測元件，為了解這三種探空儀在同樣參數上的感測元件系統性誤差，我們參考了WMO在2005年於Vacoas, Mauritius針對不同廠牌型號之探空儀的交叉比對實驗方式，於板橋探空站進行了12次三種探空儀的群組施放，並根據這些探空儀交叉比對實驗結果將Graw與Meisei兩種探空儀資料修訂至與Vaisala RS92相近。氣壓比對結果發現，近地面Graw DFM-06較Vaisala RS92低1hPa、壓力差異隨高度逐漸減少；Meisei RS2-80在初升空時會高出Vaisala RS92約10hPa，差距隨高度縮小至2.5hPa左右。溫度方面，Graw DFM-06和Vaisala RS92於量測之氣溫差值在近地面兩者相差大約0~0.2℃，到達高空(對流層頂)則相差將近0.3~0.75℃，兩者系統性誤差呈線性關係；Meisei RS2-80和Vaisala RS92量測之氣溫在低層大氣兩者差異不大，但當探空儀抵達-20℃左右高度(~300hPa)時，Meisei RS2-80隨日夜不同會高出0.5~1.0℃。溼度方面，在近地面層三款探空儀彼此的差異較小，但是到達300hPa高度以上時，其他兩種探空儀則會高出Vaisala RS92約5~10%。此外，我們針對Meisei RS2-80的ATR高空風導所進行的天線仰角、方位角滑動平均處理後的氣球軌跡平滑修正方式，有效改善板橋和東沙島原始探空資料風場品質。 得到不同探空儀之間的系統性誤差與修訂方式之後，我們將Meisei RS2-80的修訂方式用以修正SoWMEX/TiMREX 實驗期間東沙島Meisei探空資料，以了解實驗期間南中國海地區氣象參數在季風過渡期期間三波密集降雨期間南海北部高空大氣的微妙變化。季風過渡期晴空時段，反應出氣壓和氣溫升高；每一降雨發生期間，氣壓下降、氣溫偏低以及高濕度大氣變化，尤其在1500公尺至6000公尺高度特別顯著。風向風速部分，從季風肇始的中低層緯向風向轉變成西風，經向風速也轉變成偏南風，並且在過渡期間的密集降雨時段可以清晰辨識出低層噴流。季風肇始前與完全建立後整層空氣柱加溫的現象也相當明顯。

The purpose of this study is to carry out the inter-comparison of radiosondes at Banchiao sounding station on April 14-15, October 4-5 and October 11-12 of 2008. The results are then applied to diagnose the time series of atmospheric profiles over Dungsha island in SoWMEX/TiMREX. The radiosondes used in SoWMEX / TiMREX are Graw DFM-06, Vaisala RS92, and Meisei RS2-80 own different types of sensors and measurement methods. In order to understand the deviation among these radiosondes, 12 groups of co-flights were launched, which was referred the WMO radiosondes’ inter-comparison campaign at Vacoas, Mauritius in 2005. From these 12 inter-comparison experiments, we provided the deviation of Graw DFM-06 and Meisei RS2-80 compared to Vaisala RS92 and the curve-fitting function for correction. For pressure deviation, the results indicated that DFM-06 is lower 1 hPa than the RS92 and decrease the deviation with height. RS2-80 has over ~10 hPa after launch and deviation decreased to 2.5 hPa with height. For temperature deviation, DFM-06 was 0~0.2℃ near the surface and 0.3~0.75℃ near the tropopause to RS92. Their temperature deviation has good linear regression. RS2-80 has diurnal deviation about 0.5~1.0℃ to RS92. For relative humidity deviation, three radiosondes close to each other but RS92 has 5~10% dry deviation over 300hPa than the other two. According to these inter-comparison results, we validated the RS2-80 sounding data at Dongsha Island in SoWMEX / TiMREX and diagnosed the characteristics of time evaluation of Monsoon signal over North South China Sea region. We found the pressure and temperature field has reasonable decrease during storm systems (higher humidity) passing the island, specially on the lower atmosphere layer (1500~6000m). The zonal wind field in the lower atmosphere also turns to the east abruptly with northward wind component, and the lower level jet (LLJ) could be identified clearly. The air temperature of total column has significant contrast before and after the monsoon onset, too.