青藏高原冬季雪盖增大对夏季东亚大气环流影响的数值试验

利用二维非线性能量（Ｅ－ε）闭合的边界层数值模式,研究了中纬度地区海岸日间局地海风环流的特征,并对不同海风特性条件下的ＴＩＢＬ高度廓线用幂指数关系进行了数学拟合。对大量的数值试验结果分析表明,ＴＩＢＬ廓线幂指数（α）的取值与海风特性有关,其大小在０．４－１．１之间,α＝０．５只在海风充分发展时的陆上适用,文中还给出了不同海风发展程度（阶段）下的α取值。     

海岸线熏烟扩散模式

该文导出一个无需作常涡扩散系数或“面源”假设的海岸线熏烟扩散模式。根据二维理论和观测资料对热力内边界层（TIBL）高度公式进行了简化。分析和预测结果表明:在海岸线附近,应尽可能将高污染源设置在远离海岸或靠近海岸线处,避免设置在有效源高度与当地TIBL高度相等的地点附近。     

海岸地区TIBL廓线与局地海风环流的数值试验

对三次ＥｌＮｉｎｏ发生前后的ＥＣＭＷＦ资料用滤波方法（带通,低通）进行分析,得到的结果清楚地表明,在ＥｌＮｉｎｏ发生前热带季节内振荡较强,而伴随ＥｌＮｉｎｏ发生,季节内振荡明显减弱,这种能量变化最明显的地区是赤道东太平洋地区;对于周期在９０天以上的热带准定常波,伴随ＥｌＮｉｎｏ的发生其能量明显增加,这种增加反映最显著的区域是从大西洋往西一直到西太平洋。对中纬度（２５－３５°Ｎ）及中高纬度（４０－５０°Ｎ）地区的准定常波能量分析表明,中纬度地区的准定常波能量比低纬大,准定常波能量变化在中纬度（２５－３５°Ｎ）表现出与低纬能量变化一致的情形,即伴随着ＥｌＮｉｎｏ的发生,准定常波能量增加;中高纬度（４０－５０°Ｎ）只在亚洲大陆（１００－１７０°Ｅ）表现出与热带一致的能量变化。结果还显示,热带季节内振荡在低层的东传对赤道西风异常及对ＥｌＮｉｎｏ的发生、发展起着很重要的作用。     

Turbulent Transport atthe Thermal Internal Boundary-Layer top:Wavelet Analysis of Aircraft Measurements

Aircraft measurements of turbulent fluxes ofscalars collected during the BEMA campaignat the Mediterranean Spanish coast havebeen analysed using wavelet techniques. The analysis aimsat characterising the boundary-layerstructure present during a period ofthe campaign with particular attention to therole of the Thermal Internal Boundary Layer (TIBL) in regulatingthe exchange processes with the overlyingfree atmosphere. The analysis of the dataobtained by flying through the turbulentlayer reveals the presence of characteristicstructures as the aircraft crossesthe TIBL top. These occur in a specific space and scale range. Comparisons of the result of the analysisobtained for different types of scalarsgive evidence that the region correspondingto the detected scales can be identifiedwith the entrainment zone of the TIBL.     

海陆风环流及其湍流特征模拟试验

本文建立了一个采用上实用的Ｅ－ε闭合方案的边界层模式。作为应用，模拟研究了海陆风环流、陆上和海上热力风边界层以及湍流特征。结果表明，海风环流中的湍流能量大于陆风环流中的。     

NUMERICAL EXPERIMENTS ON THE TIBL PROFILES AND THE LOCAL SEA BREEZE CIRCULATION IN COASTAL AREAS

A two-dimensional nonlinear PBL numerical model using an energy closure (E-ε)method has been employed to study the sea breeze circulation and TIBL in coastal areas. The main characteristics of sea breeze obtained from numerical experiments agree with those from general observation facts. The depth of sea breeze ranges from 300 to 900 meters, maximum velocity from 1.5 m/s to 4 m/s, and its height from 100 m to 300 m. The agreement between comparisons reveals that the performance of the model is good, and the selected experiment conditions are reasonable. This paper refits the function of TIBL profiles using the Weisman's formula and the exponent value is considered to change with the different states of sea breeze. Numerical experiment results indicate that the exponent of the TIBL profile, ranging from 0.4 to 1.1, is related to the strength and depth of the sea breeze. The exponent of 0.5 is suitable only when sea breeze is fully developed. This paper also gives various exponents under different sea breezes.     

NUMERICAL MODELLING OF THE THERMAL INTERNAL BOUNDARY-LAYER EVOLUTION USING ATHENS FIELD EXPERIMENTAL DATA

The Boundary Layer Transformation Model(BLTM) is tested against data on the observed depth ofthe thermal internal boundary layer (TIBL).The model is based on a semi-empiricaltheory of the atmospheric boundary layer and takes into account theinfluence of the sea-land temperaturedifference and other meteorological conditionsduring the TIBL development. The measurementswere carried out during ATHens InternalBoundary Layer EXperiment (ATHIBLEX) in 1989and 1990. It is found that the BLTM results arein good qualitative agreement with theobserved TIBL depths. The reason for thediscrepancies between the observed andcomputed depths is explained by the differentdefinitions of the TIBL adopted.     

Analysis and numerical simulation of the meteorological observations at a tropical coastal site Chennai in India

Meteorological measurements were carried out at North Chennai semi rural area during pre-monsoon period as a part of an air quality study program. Analysis of the data showed the effects of coastal terrain namely the land-sea breeze circulation, temperature cooling during the sea breeze, difference in onset times at these sites etc. Sea breeze onset was observed with a sharp turning of the wind from westerly to south easterly associated with rise in wind speed. Advection speed of the front was about 2.0 m s^− 1. A simple mesoscale meteorological model (MAM-I) developed at Kalpakkam for coastal atmospheric dispersion estimation was used to simulate the observed characteristics. All the major features observed could be simulated by the model while significant difference was noticed in sea breeze frontal movement. MAM results were also inter-compared with MM5. There were no significant differences in the estimate of mean parameters by both the models. It is concluded that the simple model, which takes less run time in a desktop PC, is adequate enough for practical application of providing wind field for plume dispersion models at coastal sites.