A meteorological overview of the second Pacific Exploratory Mission in the Tropics
A meteorological overview of the second Pacific Exploratory Mission in the Tropics
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第二次太平洋热带考察团的气象概况
DOI：
10.1029/2001jd900173
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Yongti Zhu
中科院分区：
文献类型：
--
作者：
H. Fuelberg;R. Newell;D. Westberg;J. Maloney;J. Hannan;B. Martin;M. Avery;Yongti Zhu
总结了1999年2月至4月期间美国宇航局第二次热带太平洋探索使命（PEM-B）期间中太平洋盆地的气象条件。描述了PEM-B过程中的平均流动模式。近地表的重要特征包括副热带反气旋、南太平洋辐合带（SPCZ）和热带辐合带（ITCZ）。ITCZ具有双重结构，在北纬15 °和南纬15 °处有分支。ITCZ和SPCZ都是广泛云量和对流的区域。大范围的闪电发生在太平洋盆地周围的陆地和南太平洋中部。PEM-B发生在热带太平洋海面温度相对较低的拉尼娜时期。与气候学相比，PEM-B期表现出位于其典型位置以西的深对流，强于正常的东风信风，相对较强（弱）的北方（南方）半球急流，位于其正常位置以西的SPCZ，以及跨越赤道的对流层上部气旋风偶。PEM-B期间的环流模式进行了比较PEM-A发生在1996年8月至9月。PEM-B的ITCZ组织性较差，南半球急流较弱，北方半球急流较强，中太平洋对流增强。最后，选定的航班的气象条件进行了讨论，利用流线，10天后向轨迹，热力学探测，和卫星图像。飞机采样的空气包裹被发现来自或经过不同的地区，包括亚洲，南美洲，南部非洲和澳大利亚。在前10天期间，一些包裹仍在太平洋上空。
Meteorological conditions over the central Pacific Basin are summarized during NASA's second Pacific Exploratory Mission in the Tropics (PEM-B) which was conducted during February-April 1999. Mean flow patterns during PEM-B are described. Important features near the surface include subtropical anticyclones, the South Pacific Convergence Zone (SPCZ), and the Intertropical Convergence Zone (ITCZ). The ITCZ is found to exhibit a double structure, with branches at ∼5°N and ∼5°S. Both the ITCZ and SPCZ are areas of widespread cloudiness and convection. Extensive lightning occurs over the land masses surrounding the Pacific Basin and over the central South Pacific Ocean itself. PEM-B occurs during a La Nina period of relatively cold sea surface temperatures in the tropical Pacific. Compared to climatology, the PEM-B period exhibits deep convection located west of its typical position, stronger than normal easterly trade winds, a relatively strong (weak) northern (southern) hemispheric jet stream, the SPCZ located west of its normal position, and an upper tropospheric cyclonic wind couplet that straddles the equator. Circulation patterns during PEM-B are compared with those of PEM-A which occurred during August-September 1996. PEM-B is found to exhibit a less organized ITCZ, a comparatively weak jet stream in the Southern Hemisphere, a relatively strong jet stream in the Northern Hemisphere, and enhanced convection over the central Pacific. Finally, meteorological conditions for selected flights are discussed utilizing streamlines, 10-day backward trajectories, thermodynamic soundings, and satellite imagery. Air parcels sampled by the aircraft are found to originate or pass over diverse regions, including Asia, South America, southern Africa, and Australia. Some parcels remain over the Pacific Ocean during the preceding 10-day period.