Suppressed Daytime Convection Over the Amazon River
Suppressed Daytime Convection Over the Amazon River
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DOI：
10.1029/2020jd033627
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
M. Wu;J.‐E. Lee;D. Wang;M. Salameh
中科院分区：
文献类型：
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作者：
M. Wu;J.‐E. Lee;D. Wang;M. Salameh
我们调查了地面条件和降水对流之间的相互作用，通过比较亚马逊河对周围的森林。尽管几十公里内的天气条件相似，但河流表面白天比周围的森林凉爽，晚上温暖。我们分析了20年的高分辨率卫星降水数据，并证实了以前的研究结果，即整个亚马逊流域的白天降雨量减少。减少的百分比在干湿过渡季节最大。此外，个别支流的减少百分比显着相关的表面温度的拉普拉斯，这导致热驱动的地面辐散和抑制本地对流。此外，在雨季，大西洋沿岸附近的支流夜间降雨量增加。一个区域气候模式，然后模拟与河流相关的当地降雨异常。在河流上方，水分在白天降雨前在地表附近发散，并在地表上方会聚，部分原因是湿度的水平梯度。与河流不同的是，边界层内的水汽辐合对森林地区上方的降雨更为关键。我们的研究表明，强烈的热反差可以在潮湿的热带地区推导非均匀对流是很重要的。
We investigated the interaction between surface conditions and precipitating convection by comparing the Amazon River against the surrounding forest. Despite similar synoptic conditions within a few tens of kilometers, the river surface is substantially cooler than the surrounding forest during the day and warmer at night. We analyzed 20 years of high‐resolution satellite precipitation data and confirmed previous findings of daytime rainfall reduction over the river for the whole Amazon Basin. The percentage reduction is strongest during the dry‐to‐wet transition season. In addition, the percentage reduction of individual tributary is significantly correlated with the Laplacian of surface temperature, which causes thermally driven surface divergence and suppresses local convection. Additionally, nighttime rainfall is enhanced over tributaries near the Atlantic coast during the wet season. A regional climate model then simulates the local rainfall anomalies associated with the river. Above the river, moisture diverges near the surface and converges above the surface before the daytime rainfall, partially driven by the horizontal gradient of humidity. Unlike the river, moisture convergence within the boundary layer is more critical for the rainfall above the forest region. Our studies suggest that strong thermal contrast can be important in deriving heterogeneous convection in moist tropical regions.