平流层—对流层交换研究进展

PROGRESSES IN THE STUDY OF STRATOSPHERE-TROPOSPHERE EXCHANGE

平流层与对流层之间的物质输送和混合 (STE)是控制自然和人为排放的化学痕量物质对大气成分影响的一个重要过程。STE可以影响温室气体在上对流层和下平流层中的垂直分布 ,进而影响气候。要预报全球气候变化就必须了解平流层与对流层之间动力、化学及辐射的耦合。从STE研究的尺度问题 ,热带和中纬度地区STE研究以及我国STE研究现状进行了评述。STE具有多种尺度和形式 ,热带外平流层由波强迫驱动的全球尺度环流 ,可以诊断长时间尺度的STE ,它不能充分描述短时间尺度过程。热带外低平流层环流不能简单地描述为纬向平均 ,要正确描述痕量气体的分布必须包含纬向非对称的天气尺度过程。热带地区的滴漏管理论提供了一个新的诊断STE框架。

The Stratosphere-Troposphere Exchange (STE) of air mass and chemical species is an important process influencing the effects of trace chemical species emitted from natural and anthropogenic sources on the atmospheric composition. STE may affect climate by altering the vertical distributions of greenhouse gases in the upper troposphere and low stratosphere. Dynamical, chemical and radiative coupling between stratosphere and troposphere are among the many important processes that must be understood for prediction of global change. The paper reviews some main progresses in STE studies focusing on scale questions, researches in tropic and mid-latitude areas and also in China. STE are multi-scale interaction processes. The wave in the extra-tropical stratosphere induced forces drive a kind of global-scale circulation, which is a useful measure of global-scale stratosphere-troposphere exchange, especially on seasonal or longer timescales. But it is not suitable for describing short timescale processes . The circulation in the extra-tropical lower stratosphere cannot be simple regarded as zonal averaged. The distribution of some trace species cannot be simulated exactly if the model excludes the latitudinal asymmetry synoptic scale processes. The theory of “leaky pipes” presents a new quantitative diagnostic frame work to interpret measured results and compare them with model results. Tropopause folding and cut-off low in mid-latitude were well studied in the past.