An Objective Climatology of Tropical Cyclone Diurnal Pulses in the Atlantic Basin
An Objective Climatology of Tropical Cyclone Diurnal Pulses in the Atlantic Basin
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DOI：
10.1175/mwr-d-18-0368.1
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发表时间：
2019-01
影响因子：
3.2
通讯作者：
Sarah D. Ditchek;J. Molinari;Kristen Corbosiero;R. Fovell
中科院分区：
文献类型：
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作者：
Sarah D. Ditchek;J. Molinari;Kristen Corbosiero;R. Fovell
利用风暴中心红外亮度温度成像，对1982 - 2017年大西洋盆地热带气旋进行了6 h红外亮度温差场分析。通过确定红外差值、冷云顶面积覆盖和寿命的临界阈值，客观地定义了冷云顶脉冲。长寿命冷却脉冲（≥9小时）出现在总天数的45%，在80%的大飓风日、64%的小飓风日、46%的热带风暴日和24%的热带低气压日出现。这些冷却脉冲以8到14 m s - 1的速度向外传播。短暂的冷却脉冲（3-6 h）占26.4%。有些没有冷却脉冲的日子发生了相反的事件，这些事件被标记为升温脉冲。长寿命的升温脉冲在8.5%的时间内出现，并以与冷却脉冲相同的速度向外传播。只有12.2%的日子没有符合标准的脉冲，这表明脉冲在热带气旋中几乎无处不在。冷脉冲向外传播前的环境与暖脉冲和无脉冲日不同，在0000 ~ 0300 LT之间有更有利的条件增强内核对流：更高的海表温度和海洋热含量，整个对流层更多的水分，以及更强的低层涡度和高层辐散。
Storm-centered IR brightness temperature imagery was used to create 6-h IR brightness temperature difference fields for all Atlantic basin tropical cyclones from 1982 to 2017. Pulses of colder cloud tops were defined objectively by determining critical thresholds for the magnitude of the IR differences, areal coverage of cold-cloud tops, and longevity. Long-lived cooling pulses (≥9 h) were present on 45% of days overall, occurring on 80% of major hurricane days, 64% of minor hurricane days, 46% of tropical storm days, and 24% of tropical depression days. These cooling pulses propagated outward between 8 and 14 m s−1. Short-lived cooling pulses (3–6 h) were found 26.4% of the time. Some days without cooling pulses had events of the opposite sign, which were labeled warming pulses. Long-lived warming pulses occurred 8.5% of the time and propagated outward at the same speed as their cooling pulse counterparts. Only 12.2% of days had no pulses that met the criteria, indicating that pulsing is nearly ubiquitous in tropical cyclones. The environment prior to outward propagation of cooling pulses differed from warming pulse and no pulse days by having more favorable conditions between 0000 and 0300 LT for enhanced inner-core convection: higher SST and ocean heat content, more moisture throughout the troposphere, and stronger low-level vorticity and upper-level divergence.