Moisture Variability over the Tropical Western Pacific Ocean
Moisture Variability over the Tropical Western Pacific Ocean
复制标题
热带西太平洋的水分变化
DOI：
10.2151/jmsj.81.317
复制
发表时间：
2003
影响因子：
3.1
通讯作者：
K. Yoneyama
中科院分区：
文献类型：
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作者：
K. Yoneyama
本文利用海洋观测船的探空资料，研究了热带西太平洋暖池区的水汽变率特征。这里使用的数据收集在北方夏季和冬季从1993年到2001年的9年期间。探空资料分为五个纬向风垂直切变模式，然后检查的共同和奇异特征的水分变率。结果表明，频繁发生的高相对湿度集中在945百帕，和560百帕，任何风切变条件下，如以前发现的热带海洋和全球大气/耦合海洋-大气响应实验（TOGA COARE）的研究。在低层东风条件下，我们还在845 hPa发现了另一个小峰。这些功能的程度调制的风切变模式的差异。一个有趣的特点是，总可降水量的变化很好地代表了天气尺度对流层中层水分的变化。然而，总的水分收支和边界层中的水分变化之间的密切关系也得到了小于几天的时间尺度（特别是日周期）。我们研究了极端干燥的空气条件作为一个因素调制对流层中层水分。后向气包轨迹表明，暖池上方干空气的入侵有两条主要途径。在第一种情况下，气团可以追溯到高纬度和对流层上部。对于这种类型，与发展中纬度斜压波，如Rossby波破碎，反气旋赤道流是负责注入亚热带干空气到热带-米山和帕森斯提出的TOGA COARE干事件。在第二种类型中，气包可以追溯到对流层上部，但在中东太平洋的低纬度地区。在这种情况下，空气包起源于信风，通过该地区的干空气注入的反气旋赤道流与斜压波的发展在副热带地区。本文还讨论了干空气条件与大尺度特征的关系。
In this paper, we study the characteristics of moisture variability over the tropical western Pacific warm pool region using sounding data obtained through the use of research vessels. Data used here were collected in both boreal summer and winter seasons over a nine-year period from 1993 through 2001. Sounding data are categorized into five zonal wind vertical shear modes, and then examined for common and singular features of moisture variability. The results show frequent occurrences of high relative humidity centered around 945 hPa, and 560 hPa, for any wind shear conditions, as previously found in the Tropical Ocean and Global Atmosphere/ Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) studies. We also found another small peak at 845 hPa in low-level easterly conditions. The degree of these features is modulated by wind shear mode differences. An interesting feature is that the variation of total precipitable water is well represented by the synoptic scale mid-tropospheric moisture variation. However, a close relation between the total moisture budget and the moisture variation in the boundary layer is also obtained for a time scale of less than a few days (especially the diurnal cycle). We investigated extremely dry air conditions as one factor modulating mid-tropospheric moisture. Backward air parcel trajectories show that there are two major routes for the intrusion of dry air over the warm pool. In the first, the air parcel could be traced back to higher latitudes and the upper troposphere. For this type, anticyclonic equatorward flow associated with developing mid-latitude baroclinic waves, such as Rossby wave breaking, is responsible for injecting subtropical dry air into the Tropics—as proposed by Yoneyama and Parsons for TOGA COARE dry events. In the second type, the air parcel could be traced back to the upper troposphere, but within lower latitudes in the central-eastern Pacific. For this case, the air parcel originates from the trade winds that passed over the region where dry air was injected by the anticyclonic equatorward flow associated with the baroclinic wave development in the subtropical region. The relationship between dry air conditions and large-scale features is also discussed.
哥伦比亚大学拉蒙特-赫蒂地球观测站（美国）
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