熱帶海洋渦流熱通量與東亞大氣環流之相關的初步探討

A Preliminary Study on the Connection of the Tropical Sea Surface Heat Fluxes to the Atmospheric Circulation over the East Asia

王溫和(Wen-Ho Wang) ； 林松錦(Song-Chin Lin)

《大氣科學》 25卷2期 (1997/06) Pp. 173-194

摘要

本文主要目的在於探討熱帶海洋地區渦流熱通量的變化與東亞地區大氣環流的可能關係。分析1982～1993年春季期間（二～五月），氣候型態的變化以ENSO事件為主。ENSO發生期間，在中太平洋、北美洲地區的上層高度場具有PNA的型態，而在東亞地區，中、低緯度間的高度場變化則呈現反相關係。若將潛熱通量分別與海溫及OLR作相關分析，結果顯示在不同地區此三者彼此間的關係會有所不同。中太平洋地區海溫的增加能有效加強潛熱通量的大小，而潛熱通量的增加也可使對流活動更易發展。但在西太平洋地區則出現不同的特性，海溫的增加並無法使潛熱通量增加，而潛熱通量的增強也無助於對流的產生。這種結果可能與該區的環流型態及潛熱通量特性有關。利用遙相關的方法證實，南海地區與暖池區的潛熱通量變化與東亞地區大氣環流型態間有相當的關聯性存在。經分析發現兩地區的潛熱通量與東亞主槽位置的高度場變化具有明顯的反相關係，同時在南海地區的潛熱通量與華南地區低層高度場有很強的正相關係，此現象似乎意謂上層槽線加深有利冷高壓南下，海面上在冷空氣的吹拂下可使潛熱通量快速增加。從整體型態來看，南海地區潛熱通量似乎有助於中緯度地區波動結構的增強。暖池區的潛熱通量則可使中、低緯度間高度場的變化呈現南北正負相反的關係型態，而此相關性在ENSO年會因潛熱通量的增強而變得更加明顯。此外，在延遲交互相關的分析中，發現與南海地區潛熱通量相關的中緯度波列結構會有向東移動的趨勢。而與暖池區潛熱通量相關之中、低緯度間的南北反相結構也有向北移動的情形，而且隨著系統的北移伴有一組織性的正相關結構由熱帶地區逐漸地向東亞地區移動，因而使東亞地區高度場與暖池區潛熱通量兩者間的相關係數跟著變化，這種現象可能與暖池區潛熱通量有利於對流發展的特性有關。

關鍵字

渦流通量 ； 東亞大氣環流 ； 遙相關

並列摘要

The purpose of this study is to explore the possible connection between the tropical sea surface heat fluxes and the atmospheric circulation over the East Asia. Climate data of spring season (February ~ May) spanning 1982 to 1993 indicate the ENSO events are the major climatic variation. During the ENSO period, a PNA pattern was revealed in the upper level height fields over the Central Pacific and North America areas. Over the East Asia, there exists a negative correlation between the height fields of middle and low latitudes. Correlation analyses of surface latent heat flux with sea surface temperature and OLR, respectively, show different characteristics at different areas. Over the Central Pacific ocean, warming of sea surface temperature can effectly increase the surface latent heat flux and, consequently, promote the convective activities. However, over the West Pacific ocean, increasing of latent heat flux does not intensify the convection. Such results could be related to the strength of circulation and the increasing mechanism of surface latent heat flux.Results of teleconnection analysis depict that the variations of surface heat flux at the South China Sea and the warm pool area do have influences on the atmospheric circulation over the East Asia. While the surface heat flux at both areas are negatively correlated with the major trough over East Asia, surface heat flux at South China Sea is positively correlated with the low-level height field over the southern China area. It seems that the intensification of the upper-level trough favors the southward movement of cold-high pressure, and consequently increases the surface latent heat flux due to advection of cold air over the ocean. The overall teleconnection patterns indicate that the surface heat flux at the South China Sea can intensify the wave-like structure in the middle latitudes and the surface heat flux at the warm pool is associated with a positive-negative coupled correlation between low and middle latitudes. These patterns seem more prominent in the ENSO years due to the enhancement of surface latent heat fluxes. Further study with the lagged cross-correlation analysis, it is found that the middle latitude wave-like structure in association with the surface heat flux at the South China Sea tends to move eastward and the positive-negative coupled pattern in association with the warm pool tends to move northward. As the coupled pattern moves northward, an organized positive correlation structure also moves toward the East Asia area from the warm pool. This leads to the variation of correlation coefficients between the surface heat flux at the warm pool and the height field in the East Asia area. Also, this phenomenon may be linked to the previous finding that the surface latent heat flux at the warm pool is favorable for the development of convection.

並列關鍵字

Surface fluxes ； Atmospheric circulation over the East Asia ； Teleconnection