TROPICAL ATMOSPHERIC NONLINEAR STEADY RESPONSE SOLUTION UNDER EFFECTS OF PAIRED HEAT SOURCES OF CONTRASTING NATURE*

Based on steady semi-geostrophic model equations,analysis is carried out of the linear and nonlinear modification/response of the tropical atmosphere to the forcing of ideal paired heat sources of contrasting nature.Resuits show that the linear part is dominant in the steady response but the nonlinear modification is quite noticable in the neighborhood of the heat source and between the paired sources,and the barotropic mode and second baroclinic mode play a different role in the modification,with the barotropic(second baroclinic)mode modification depending largely on the Rossby wave self-interaction(the magnitude due to the Kelvin-Rossby wave interaction)between the paired sources.     

热带大气对EI Nion和La Nina的动力响应

利用1951－1992年的热带太平洋每月海表温度资料，采用3－5年带通滤波，得到SSTA在这种时间尺度的低频振荡（LF），SSTA的LF振荡的经验正交分析第1主分量的时突变化突出地表现了E1 Nino和La Nina循环的特征。对热带大气环流850hPa月风场异常进行3－5年带通滤波，再对纬向风作经验正交分析，得到第1主分量明显地表现了热带大气环流在纬向上不均匀分布的循环特征。为了探讨上述两个循环的物理关系，建立了一个简单的热带大气模式，其中包括蒸发，感热和风场之间的反馈以及凝结潜热和流场的反馈作用。当E1 Nino和La Nina所形成的SSTA为定常已知的分布时，模拟了热带大气纬向风和降水对海表温度异常的响应。     

EFFECT OF THE NONLINEAR TERM ON MOVEMENT AND DEVELOPMENT OF TROPICAL CYCLONE

The dynamics of tropical cyclone is investigated in a nondivergent barotropic model with nobasic flow. The effect of nonlinear term on the movement and development of tropical cyclone isemphatically demonstrated. The advection of asymmetric vorticity by the symmetric flow (AAVS)produces the small-scale gyres (SSGs). The SSGs counterclockwise rotate around the tropicalcyclone center. The interaction of SSGs with the large-scale beta gyres (LSBGs) leads to theoscillation in translation speed and vacillation in translation direction for tropical cyclone. Theadvection of symmetric vorticity by the asymmetric flow (ASVA) steers the symmetric circulationof tropical cyclone. The ventilation flow vector determined by the asymmetric flow is closecorrelated with the motion vector of tropical cyclone. The nonlinear advection of relative vorticityis an order of magnitude greater than the linear advection of planetary vorticity, However, theasymmetric circulation created by the planetary vorticity advection provides a background conditionfor anomalous motions of the tropical cyclone. The combination of the linear and nonlinear effectsresults in accelerated, decelerated, changing direction and/or counterclockwise looping motions ofthe tropical cyclone.     

INTERANNUAL VARIATIONS OF ATMOSPHERIC HEAT SOURCES AND MOISTURE SINKS OVER THE EQUATORIAL PACIFIC AND THEIR RELATIONS TO THE SST ANOMALIES

The interannual variations of atmospheric heat sources and moisture sinks over the Equatorial Pacific and their relations with the SST anomalies are studied using ECMWF reanalysis data from 1979 to 1993. It is found by singular value decomposition (SVD)…     

EFFECT OF THE NONLINEAR TERM ON MOVEMENT AND DEVELOPMENT OF TROPICAL CYCLONE*

The dynamics of tropical cyclone is investigated in a nondivergent barotropic model with no basic flow. The effect of nonlinear term on the movement and development of tropical cyclone is emphatically demonstrated. The advection of asymmetric vorticity by the symmetric flow(AAVS) produces the small-scale gyres(SSGs). The SSGs counterclockwise rotate around the tropical cyclone center. The interaction of SSGs with the large-scale beta gyres(LSBGs) leads to the oscillation in translation speed and vacillation in translation direction for tropical cyclone. The advection of symmetric vorticity by the asymmetric flow(ASVA) steers the symmetric circulation of tropical cyclone. The ventilation flow vector determined by the asymmetric flow is close correlated with the motion vector of tropical cyclone. The nonlinear advection of relative vorticity is an order of magnitude greater than the linear advection of planetary vorticity, However, the asymmetric circulation created by the planetary vorticity advection provides a background condition for anomalous motions of the tropical cyclone. The combination of the linear and nonlinear effects results in accelerated, decelerated, changing direction and/or counterclockwise looping motions of the tropical cyclone.     

热带太平洋上空大气热源、水汽汇的年际变化及其与海温异常之间的联系

利用ECMWF(1979～1993年)的再分析资料计算分析了热带太平洋上空大气热源及水汽汇的年际变化及其与海表温度异常之间的联系。通过SVD的分析,发现大气热源的垂直积分〈Q1〉和水汽汇垂直积分〈Q2〉异常与SST异常有着较高正相关关系的热带太平洋区域主要集中在170 E以东的5 S～5 N之间的一个狭长带中。分析大气热源和水汽汇的空间结构,则发现在赤道太平洋中、东部地区,除了最低层(962.5 hPa)和最高层(85 hPa)以外,对流层其余各层Q1、Q2异常与SST异常都存在较高的正相关关系;而在赤道西太平洋地区,850 hPa层以下,Q1异常与SST异常为负相关关系,在962.5 hPa相关系数甚至为 -0.59,其余各层Q1、Q2异常与SST异常也只有很弱的正相关关系。