東亞地區冷空氣變性過程之數值研究

The Numerical Study of Cold Air Transfer Process on East Asia

侯昭平(Jou-Ping Hou) ； 余青樺(Ching-Hua Yu) ； 張智昇(Chih-Sheng Chang) ； 張龍耀(Lung-Yao Chang) ； 蔡世樵(Shih-Chiao Tsai) ； 李亞偉(Ya-Wei Lee) ； 黃椿喜(Treng-Shi Huang)

《大氣科學》 42卷3期 (2014/12) Pp. 273-300

摘要

本研究使用Weather Research and Forecasting Model（WRF model）3.5.1版模擬2010年1月13日影響黃海、東海海面之冷氣團變性過程及海面上淺對流的發展，模擬結果中，大陸冷高壓自華北引入大量冷空氣，流經黃海、東海及臺灣北部海面，並使洋面上出現大量形狀不一的海上層積雲，冷空氣離岸一段距離後，細長條狀的雲系（雲街）開始出現，通過洋面時間更長後，海上層積雲則轉變為塊狀雲系（開放胞）。海上層積雲出現的位置，自大陸北方到東南方沿岸，有成雲位置自北而南，離岸越遠的特徵；大於7×10^(-3)s-^(1)的強垂直風切可以形成雲街，但垂直風切接近7×10^(-3)s^(-1)時，亦能形成開放胞。海洋大氣邊界層自離岸後快速上升，冷空氣屬性亦從乾冷轉為暖濕，離岸較遠的黃海和東海，海洋邊界層因劇烈海氣交互作用，使此區邊界層上方出現了因浮力震盪引發的重力波；固定位置的分析中，發現冷空氣具逐時增溫且變濕的日變化特性，而非絕熱項分析則顯示，相同位置可感熱和潛熱通量均出現逐時下降的情形，但可感熱和潛熱通量均存在離岸越遠，通量值越大的特徵，Bowen ratio分析顯示，離岸越近，可感熱通量的影響越重要，離岸越遠，轉變為潛熱通量的影響越重要。

關鍵字

淺對流 ； 雲街 ； 開放胞 ； 海氣交互作用 ； 可感熱通量 ； 潛熱通量

並列摘要

The development of shallow convection and the properties change process of cold air mass are simulated with a numerical model Weather Research and Forecasting (WRF) Model V3.5.1 on January 13^(th), 2010. Our simulation results show that continental cold high pressure brought a lot of cold air from North-East China which passes over the Yellow Sea and East China Sea make a large number of different shapes of marine stratocumulus. Cloud streets formed away from the coast line over warm open water of ocean and changed its shapes to mass clouds (open cells) as cold air outbreak for further distance. The locations of maritime stratocumulus, from the north to the south-east coast of mainland China, have characteristics of late to form clouds from coastline to further ocean. Strong vertical wind shear more than 7 × 10^(-3) s^(-1) can form clouds streets but when vertical wind shear is close to 7 × 10^(-3) s^(-1) open cells will show up. The depth of boundary layer of marine rises rapidly away from coastline. The properties of cold air changes from cold and dry to warm and humidity. Gravity waves induced by buoyancy oscillations which come from sever air sea interaction over top of marine boundary layer. Fix position analysis showed that cold air have characteristics of hourly warm and wet with the diurnal variation. Non-adiabatic analysis showed that sensible and latent heat fluxes decline hourly at the same position, but sensible and latent heat fluxes are greater when farther offshore. Bowen ratio analysis showed that when offshore closer, the more important impact may be on sensible heat flux. The more close to coastline, the more important of sensible heat flux. The latent heat flux is more important in an oppositely direction.

並列關鍵字

Shallow Water Convection ； Cloud Street ； Open Cell ； Air-Sea Interaction ； Sensible Heat Flux ； Latent Heat Flux ； Bowen Ratio