Observational studies of the general circulation of the Tropics: long term mean values
Observational studies of the general circulation of the Tropics: long term mean values
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DOI：
10.1002/qj.49709540404
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发表时间：
1969-04
影响因子：
8.9
通讯作者：
J. Kidson;D. G. Vincent;R. Newell
中科院分区：
文献类型：
--
作者：
J. Kidson;D. G. Vincent;R. Newell
在北纬45°至南纬30°之间的298个台站的数据已处理为1957年7月至1964年12月的数据。12 - 2月和6 - 8月两个三个月季节的平均风场和温度场以及动量和热通量。对流层的结果是通过对长期台站资料的客观分析得到的，而平流层的结果是通过纬度带资料得到的，奇数年和偶数年的数据权重相等，因此实际上已经消除了两年分量。热带对流层平均温度横截面的季节变化不大，梯度也很小。在南部夏季，最高温度在5°S附近，但在6月至8月期间，由于大陆上更强的加热，最高温度上升到20°N。在热带平流层，季节变化是从12 - 2月的较低温度到6 - 8月的较高温度。平均纬向风型显示，6 - 8月热带东风偏强，在对流层上层纬度范围较大。所得到的哈德利环流看起来相当合理，冬季半球环流占主导地位并延伸到赤道上空。虽然对流层动量通量的所有三个分量都得到了评估，但平流层的动量通量只得到瞬态涡的贡献。在赤道对流层上层观测到一股强通量直接进入夏季半球。对流层中层的感热通量在两个半球的热带地区是向赤道方向的，并且注意到向夏季半球的少量输送。这种向赤道方向的通量除北半球夏季外，在两个半球都是反梯度的。总能量的平均运动输运大约比赤道的涡旋输运大一个数量级，为冬季半球提供能量。计算了热带对流层动能和有效势能的纬向和涡旋形式，以及它们之间除有效势能和动能之间的瞬态涡旋转换外的所有转换。平均而言，动能含量约为可用势能含量的两倍，动量通量的转换大于热通量的转换。然而，平均运动的转换在24°N-24°S范围内是最大的，导致纬向动能的恢复时间约为3-5天。这种转变似乎足够大，足以抵消中纬度地区的破坏。综合起来，这里提出的结果给出了热带环流的一致模式。直接哈德利电池被看作是由涡流通量分布的热量和动量的来源。平均电池的能量供应被认为是其上升分支的凝结潜热。
Data from 298 stations between 45°N and 30°S have been processed for the period July 1957 to December 1964. The mean wind and temperature fields are presented together with the momentum and heat fluxes for two three month seasons, December-February and June-August. The tropospheric results were obtained from objective analysis of the long term station means and the stratospheric results from latitude band means giving equal weight to data from odd and even years so that the biennial component has been virtually eliminated. The mean temperature cross-sections show little seasonal variation in the tropical troposphere and gradients are small. The maximum temperature is in the vicinity of 5°S during the southern summer but moves to 20°N during June-August as a consequence of stronger heating over the continents. In the tropical stratosphere the seasonal variation is from lower temperatures in December-February to higher temperatures in June-August. The mean zonal wind pattern shows the tropical easterlies to be stronger and to occupy a greater range of latitudes in the upper troposphere during June-August. The Hadley circulation obtained appears quite reasonable with the winter hemisphere cell predominating and extending over the Equator. Although all three components of the momentum flux were evaluated for the troposphere, only the transient eddy contribution could be obtained for the stratosphere. A strong flux is observed in the upper equatorial troposphere directed into the summer hemisphere. The sensible heat-flux in the middle troposphere is equatorward in the Tropics of both hemispheres and a small transport into the summer hemisphere is noted. This equatorward flux is countergradient in both hemispheres except during the northern summer. The mean motion transport of total energy is about an order of magnitude larger than the eddy transport at the Equator and supplies energy to the winter hemisphere. The zonal and eddy forms of kinetic energy and available potential energy have been evaluated for the tropical troposphere together with all conversions between them except for that by transient eddies between available potential energy and kinetic energy. On the average, kinetic energy contents are about twice as large as available potential energy contents and the momentum flux conversions are larger than those involving heat fluxes. The conversion by the mean motions, however, is largest of all over the range 24°N-24°S and leads to a rejuvenation time of some 3–5 days for the zonal kinetic energy. This conversion appears to be sufficiently large to offset the destruction in middle latitudes. Taken together, the results presented here give a consistent pattern for the tropical circulation. The direct Hadley cell is seen as a source of both heat and momentum which are distributed by the eddy fluxes. The energy supply for the mean cell is thought to be the latent heat of condensation in its ascending branch.