Evolution of precipitation and convective echo top heights observed by TRMM radar over the Indian Ocean during DYNAMO
Evolution of precipitation and convective echo top heights observed by TRMM radar over the Indian Ocean during DYNAMO
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DYNAMO 期间 TRMM 雷达观测到的印度洋降水和对流回波顶高度的演变
DOI：
10.1002/2014jd022934
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
R. Houze
中科院分区：
文献类型：
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作者：
S. Powell;R. Houze
热带降雨测量任务的雷达数据显示了2011-2012年马登-朱利安涛动（DYNAMO）场运动动力学期间印度洋和海洋大陆对流要素回波顶的演变。回波顶高呈双峰分布，中等高度的积雨云构成“密集模态”，而垂直扩展的积雨云构成“深模态”。从10月到1月，印度洋大部分地区的季节内时间尺度主导了这些模态的变化。在海洋大陆上空，对流回波顶高没有明显的季节内信号。在探测到季内振荡的地区，雷达回波在小于1周的时间尺度上由以密集模态为主演变为以深层模态对流为主。密集回波面积覆盖比深回波面积增加早2 ~ 8 d。这些卫星衍生的结果证实，在个别DYNAMO观测点观测到的对流加深的时间尺度与印度洋大尺度对流的时间尺度是一致的。再分析所描述的纬向风、温度和湿度的季节内变化也与DYNAMO期间雨水探空观测所得的结果一致。因此，最近版本的“放电-充放电”假说所描述的对流逐渐形成并不能准确描述DYNAMO期间观测到的MJO事件之前对流的演变，尽管云湿润过程可能在一周或更短的时间尺度上仍然相关。
Radar data from the Tropical Rainfall Measuring Mission show the evolution of echo tops of convective elements over the Indian Ocean and Maritime Continent during the Dynamics of the Madden‐Julian Oscillation (DYNAMO) field campaign of 2011–2012. Echo top heights exhibited a bimodal distribution wherein cumulonimbi of moderate height constituted a “congestus mode” while vertically extensive cumulonimbus made up a “deep mode.” An intraseasonal time scale dominated variability in these modes from October to January over much of the Indian Ocean. Over the Maritime Continent, there was no clear intraseasonal signal in convective echo top heights. Where the intraseasonal oscillation was detected, radar echoes evolved from being dominated by the congestus mode to being characterized by more deep mode convection on time scales of less than 1 week. The areal coverage of congestus echoes began to increase 2–8 days prior to the rise in area of deep echoes. These satellite‐derived results confirm that the time scale for convective deepening seen at individual DYNAMO observational sites is consistent with that of convection on the large scale over the Indian Ocean. Intraseasonal variability of zonal wind, temperature, and humidity as depicted by reanalysis is also consistent with that derived from rawinsonde observations during DYNAMO. Thus, the gradual buildup of convection as depicted by recent versions of the “discharge‐recharge” hypothesis does not accurately describe evolutions of convection prior to MJO events observed during DYNAMO, although cloud moistening processes may still be relevant on time scales of 1 week or less.