Initiations of Mesoscale Convective Systems in the Middle Reaches of the Yangtze River Basin Based on FY‐4A Satellite Data: Statistical Characteristics and Environmental Conditions
Initiations of Mesoscale Convective Systems in the Middle Reaches of the Yangtze River Basin Based on FY‐4A Satellite Data: Statistical Characteristics and Environmental Conditions
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DOI：
10.1029/2023jd038630
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发表时间：
2023-11
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影响因子：
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通讯作者：
Yanan Fu;Jianhua Sun;S. Fu;Yuanchun Zhang;Zheng Ma
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作者：
Yanan Fu;Jianhua Sun;S. Fu;Yuanchun Zhang;Zheng Ma
根据风云四号A卫星亮温观测结果，2018-2021年暖季（4-9月）长江中游地区识别出800个中尺度对流系统（MCS），分为准静止型（QS）和外移型（OM，即移出源区）。之后，使用区域重叠和光流的混合方法向后跟踪 MCS 的启动。然后，分析了QS-MCS和OM-MCS的主要特征及其各自的天气环流和环境参数。 QS-MCS 主要发生在 7 月和 8 月，并且主要在下午启动。 OM-MCS 主要发生在 6 月和 7 月，分别在中午和深夜有两个起始峰值。 QS-MCS 主要在山区发起。相比之下，OM-MCS 主要起源于平原地区。与 OM-MCS 相比，QS-MCS 在强度上表现出显着的昼夜变化，并且发展更快。利用k-means算法将总共285天的环流（没有热带气旋的直接影响）客观地分为三种模式。 Ⅰ型与低空急流密切相关，与典型梅雨锋具有最相似的特征，是最有利于MCS启动的环流类型。 II型以西北风为主，低层对流层有相对稳定的层。模式 III 具有干绝热层甚至超绝热层，这有助于降低层的稳定性。
Based on the brightness temperature observed by the Fengyun‐4A satellite, eight hundred mesoscale convective systems (MCSs) are identified in the middle reaches of the Yangtze River Basin during the warm seasons (April–September) of 2018–2021, and these MCSs are categorized into the quasistationary (QS) type and the outward‐moving (OM; i.e., moving beyond the source region) type. Afterward, the initiations of the MCSs are backward tracked using a hybrid method of areal overlapping and optical flow. Then, the main features of QS‐MCSs and OM‐MCSs and their respective synoptic circulations and environmental parameters are analyzed. The QS‐MCSs primarily occur in July and August and are mainly initiated in the afternoon. The OM‐MCSs mostly occur in June and July with two initiation peaks at noon and late night, respectively. The QS‐MCSs are mainly initiated in mountainous areas. In contrast, the OM‐MCSs are mainly initiated in plain areas. Compared to the OM‐MCSs, the QS‐MCSs show notable diurnal variation in intensity and develop more rapidly. Circulations of a total of 285 days (without direct influences from tropical cyclones) are objectively classified into three patterns by using the k‐means algorithm. Pattern‐I, which is closely related to low‐level jets, shows the most similar features to those of typical Mei‐yu fronts, and it acts as the most favorable circulation type for MCS initiations. Pattern‐II is dominated by northwesterlies, with a relatively stable layer in the low‐level troposphere. Pattern‐III features a dry‐adiabatic or even a superadiabatic layer that contributes to decreasing the layer stability.