Diurnal precipitation regimes in the global tropics
Diurnal precipitation regimes in the global tropics
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DOI：
10.1175/2007jcli2051.1
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发表时间：
2008-06-01
影响因子：
4.9
通讯作者：
Wang, Bin
中科院分区：
文献类型：
--
作者：
Kikuchi, Kazuyoshi;Wang, Bin
利用1998 - 2006年两个互补的热带降雨测量使命（TRMM）数据集（3B 42和3G 68）记录了全球热带降水的日变化，试图提供一个统一的日周期视图和评估数值模式性能的指标。3B 42资料具有更好的空间覆盖性，3G 68资料提供了更准确的日相位信息。第一和第二经验正交函数（ERF）模式代表昼夜循环，占3B 42中总方差的89%。第三和第四模态代表半日循环，占总方差的10%。这两个数据集产生一致的空间结构和时间演变，但它们有不同的优势：来自3B 42的模式表现出更少的噪音，而3G 68产生了一个可以说更准确的昼夜相位。来自3G 68系统的昼夜相位导致3B 42约3小时。三个热带昼夜循环制度（海洋，大陆和沿海）确定根据振幅，峰值时间和相位传播特性的昼夜降水。海洋状况的特点是中等振幅和清晨峰值[ 0600 - 0900当地太阳时（LST）]，主要出现在太平洋，大西洋和印度洋的海洋辐合区。相比之下，大陆体制的特点是振幅大，下午峰值（1500 - 1800 LST），这是特别明显的南美洲和赤道非洲附近的维多利亚湖。无论是海洋和大陆的制度表现出很少的空间相位传播。然而，沿海地区，不仅表现出大的振幅，但也显着的相位传播。还可以确认两个次级制度，它们常常沿着同一陆海边界同时存在。海滨海岸的特点是近海阶段的传播，与峰值出现在傍晚到中午的第二天（2100 - 1200 LST），而陆侧海岸的政权有向陆阶段的传播与峰值出现在中午到傍晚（1200 - 2100 LST）。沿海体系在海洋大陆、印度次大陆、澳大利亚北方、从墨西哥延伸到厄瓜多尔的美洲西海岸、赤道非洲西海岸和巴西东北部的陆地-海洋边界上沿着很突出。请注意，昼夜周期的振幅取决于季节，但昼夜相位特征不依赖于季节。这种分析所建议的基本机制，特别是在沿海地区，也进行了讨论。
Diurnal variations of the global tropical precipitation are documented by using two complementary Tropical Rainfall Measuring Mission (TRMM) datasets (3B42 and 3G68) for 1998 -2006 in an attempt to provide a unified view of the diurnal cycle and a metric for evaluating numerical model performance. The 3B42 data have better spatial coverage; the 3G68 data offer more accurate diurnal phase information. The first and second empirical orthogonal function (EOF) modes represent the diurnal cycle and account for 89% of the total variance in 3B42. The third and fourth EOF modes, which account for 10% of the total variance, represent the semidiurnal cycle. Both datasets yield consistent spatial structures and temporal evolution, but they have different advantages: the patterns derived from 3B42 exhibit less noise, while 3G68 yields an arguably more accurate diurnal phase. The diurnal phase derived from 3G68 systematically leads 3B42 by about 3 h.Three tropical diurnal cycle regimes (oceanic, continental, and coastal) are identified according to the amplitude, peak time, and phase propagation characteristics of the diurnal precipitation. The oceanic regime is characterized by moderate amplitude and an early morning peak [ 0600 -0900 Local Solar Time (LST)], found primarily in the oceanic convergence zones in the Pacific, Atlantic, and Indian Oceans. In contrast, the continental regime features a large amplitude and an afternoon peak (1500 -1800 LST), which is particularly pronounced in South America and equatorial Africa near Lake Victoria. Both the oceanic and continental regimes show little spatial phase propagation. The coastal regime, however, shows not only large amplitude but also prominent phase propagation. Two subregimes can also be recognized, often concurring along the same land -sea boundary. The seaside coastal regime is characterized by offshore phase propagation, with peaks occurring from late evening to noon of the next day (2100 -1200 LST), whereas the landside coastal regime has landward phase propagation with peaks occurring from noon to evening (1200 2100 LST). The coastal regime is prominent along the land -sea boundaries of the Maritime Continent, the Indian subcontinent, northern Australia, the west coast of America extending from Mexico to Ecuador, the west coast of equatorial Africa, and Northeast Brazil. Note that the amplitude of the diurnal cycle is dependent on season, but the diurnal phase characteristics are not. The underlying mechanism suggested by this analysis, especially over the coastal areas, is also discussed.