Vertical motions of the tropical convective cloud spectrum over Darwin, Australia
Vertical motions of the tropical convective cloud spectrum over Darwin, Australia
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澳大利亚达尔文上空热带对流云谱的垂直运动
DOI：
10.1002/qj.2520
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发表时间：
2015
影响因子：
8.9
通讯作者：
C. Williams
中科院分区：
文献类型：
--
作者：
C. Schumacher;S. N. Stevenson;C. Williams
来自澳大利亚达尔文的三个月的廓线观测被分成七种云类型(浅、中、深对流云；弱而强的层状雨；过渡性和只有冰的铁锤)，以提供整个季风季热带对流云全谱的垂直速度统计。与过去的研究一致，对流上升气流的高度和强度随着对流云高度的增加而增加。浅、中、深对流的平均最大值分别为0.3m的S−1、0.6m的S−1和2.5m的S−1。深对流极值接近18m，S−1在8公里以上，而所有对流云类型的下沉气流最大值都在4公里以下。层状垂直速度比活跃对流中弱且变化较小，最大平均值为lt；0.25m S−1。但是，与近地面反射率(从而雨率)较大的层状雨区比较弱的层状雨区有较强的中尺度上、下气流。近地面少雨或无雨的砧状云也表现出中尺度的上下气流，但垂直速度剖面至少向上移动了2公里。此外，落锤上升气流仅为层状雨区强度的20-50%。总体而言，垂直运动的统计数据在季风前、活跃和抑制期间是相似的。每种云类型的垂直速度分布也与反射率分布大体一致(即最强的上升气流通常与最大的反射率有关)，这使得动力和微物理云特性之间存在一定的联系。例如，在深对流中，高于0°C水平的强上升气流与支持冷雨增长过程重要性的强倾斜反射率廓线有关，而较强的垂直运动与具有强劲亮带的层状雨有关。
Three months of profiler observations from Darwin, Australia are separated into seven cloud types (shallow, mid‐level, and deep convective; weak and robust stratiform rain; and transitional and ice‐only anvil) to provide vertical velocity statistics on the full spectrum of tropical convective clouds over the course of a monsoon season. Consistent with past studies, convective updraughts increase in height and magnitude as the convective cloud height increases. Shallow/mid‐level/deep convection has a mean maximum value of 0.3 m s−1 at 3 km/0.6 m s−1 at 5 km/2.5 m s−1 at 8 km. Deep convective extremes approach 18 m s−1 above 8 km while downdraughts in all convective cloud types are maximum below 4 km. Stratiform vertical velocities are weaker and less varied than in active convection, with maximum mean values <0.25 m s−1. However, stratiform rain regions associated with larger near‐surface reflectivities (and thus rain rates) have stronger mesoscale up‐ and downdraughts than weaker stratiform rain regions. Anvil cloud with little or no rain near the surface also exhibits mesoscale up‐ and downdraughts, but the vertical velocity profile is shifted up in height by at least 2 km. In addition, anvil updraughts were only 20–50% of the magnitudes in the stratiform rain region. Overall, the vertical motion statistics were similar across the pre‐, active and suppressed monsoon periods. The vertical velocity distributions for each cloud type were also generally consistent with the reflectivity distributions (i.e. the strongest updraughts were often linked to the largest reflectivities), allowing for some linkages between the dynamical and microphysical cloud properties. For example, strong updraughts above the 0 °C level in deep convection are associated with strongly sloping reflectivity profiles supporting the importance of cold rain growth processes, and stronger vertical motions are associated with stratiform rain that has a robust bright band.