识别土壤湿度状态和夏季MCS启动之间的相互作用机制在弱强迫的同视环境中,使用对流允许模拟
Rachel Gaal1, James L Kinter2, Paul A Dirmeyer2
1Department of Atmospheric Science Rosenstiel School of Marine and Atmospheric Science University of Miami Miami FL USA.
概括
土壤湿度模式影响中等尺度对流系统 (MCS) 的发展. 在发射点西南的干燥土壤可以通过改变大气条件导致更早的MCS事件.
科学领域:
- 大气科学 大气科学
- 水文学的水文学
- 气象学 天气学
背景情况:
- 中等层次的对流系统 (MCS) 是重要的天气现象,特别是在北极夏季.
- 了解影响MCS启动的因素对于改善天气预报至关重要.
- 土壤湿度 (SM) 是一个关键的陆地表面变量,可以影响大气过程.
研究的目的:
- 为了确定土壤湿度 (SM) 状态和弱强迫突触尺度MCS事件的发生之间的相互作用机制.
- 调查SM异质性如何影响MCS启动时间和地点.
- 探索近地表面大气变量在SM驱动的MCS发展中的作用.
主要方法:
- 利用天气研究和预报 (WRF) 模型对美国大平原的灵敏度研究.
- 用一个均干燥的SM贴片 (5°×5°) 进行模拟,该贴片以记录的MCS启动点为中心.
- 对97个模拟的MCS病例 (2004-2017年) 进行了以风暴为中心的SM,2m温度和2m湿度的复合分析.
主要成果:
- 在模拟的MCS启动地点周围观察到干燥到湿的SM的SW-to-NE梯度.
- 这种SM梯度影响了近地表流动,在2m温度和2m湿度下产生了对齐的梯度.
- 在干燥SM扰动的模拟中,MCS启动发生较早 (∼1-2小时),特别是在SM过渡区的干燥侧.
结论:
- 土壤湿度异质性,结构为SW-to-NE梯度,可以驱动MCS启动弱强 synoptic环境.
- 主要机制涉及SM影响近地表流动,改变温度和湿度,并影响行星边界层的生长.
- 低水平风场与有组织的SM梯度的对齐对于SM驱动的MCS启动至关重要.
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