Thermally Direct Mesoscale Circulations Caused by Land Surface Roughness Anomalies
Thermally Direct Mesoscale Circulations Caused by Land Surface Roughness Anomalies
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DOI：
10.1029/2023gl105150
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发表时间：
2023-08
影响因子：
5.2
通讯作者：
Yu Cheng;K. McColl
中科院分区：
文献类型：
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作者：
Yu Cheng;K. McColl
森林砍伐、城市化和风力发电场的建设可以改变地表粗糙度，从而进一步影响地表热通量，进而影响天气和气候。地表粗糙度异常可以通过改变平均风速动态地触发辐合。在这里，我们报告了一个新的机制，粗糙度异常导致热直接中尺度环流和异常降水。为了研究这一机制，我们在具有规定表面粗糙度异常的理想化陆地表面上进行云允许模拟。异常高的粗糙度增加了近地面的湍流混合，从而降低了地表温度和向外的长波辐射。增加的地面净辐射部分转化为较大的感热通量，触发了由差异加热驱动的中尺度环流。因此，高粗糙度异常上的降水量通常大于低粗糙度背景下的降水量。这种新机制在气候模型中不存在，可能与风力发电场，城市和森林的风暴形成有关。
Deforestation, urbanization and construction of wind farms can change the land surface roughness, which can further influence surface heat fluxes and thus weather and climate. Land surface roughness anomalies can dynamically trigger convergence through changing mean wind speed. Here, we report a new mechanism, in which roughness anomalies cause thermally direct mesoscale circulations and anomalous precipitation. To study this mechanism, we conduct cloud‐permitting simulations over an idealized land surface with prescribed surface roughness anomalies. Anomalously high roughness increases turbulent mixing near the surface, which decreases land surface temperature and outgoing longwave radiation. The additional surface net radiation partly goes into greater sensible heat flux, which triggers mesoscale circulations driven by differential heating. As a result, precipitation over the high‐roughness anomaly is generally larger than that over the low‐roughness background. This new mechanism, not present in climate models, may be relevant to storm formation over wind farms, cities and forests.