基于湿位涡场的悬空波导预报研究

Elevated duct forecast based on moist potential vorticity fields

基于美国国家环境数据中心(NCEP)的再分析数据(FNL)和探空数据,利用美国宾夕法尼亚州立大学和美国国家大气研究中心的第5代区域中尺度数值模式(MM5)模拟分析了悬空波导出现时的湿位涡场特征,分析表明湿位涡场负中心剧烈变化区域分布与悬空波导的区域分布一致。湿位涡是动力和热力相结合的参数,在研究中便于机理和预报分析,由于湿位涡的不可渗透性,因此,湿位涡的发展变化只能沿着等熵面移动,其负中心区和梯度剧烈增大区也只能沿着等相当位温面移动,由于其移动速度和方向是可知的,因此,悬空波导的移动速度和方向也是可知和可预报的,从而为悬空波导的预报开辟了一种新思路和途径。

Characteristics of moist potential vorticity fields when elevated duct ap- pears are simulated with the numerical Mesoscale Model 5 （MMS） based on Nation- al Centers for Environmental Pridiction（NCEP） final operational global analysis （FNL） data and sounding data. Simulated result shows that the elevated duct re- gion occrus in the center that negative moist potential vorticity fields changes rapid- ly. Moist potential vorticity is a combined parameter that denotes dynamics and thermodynamics process, and can be used to mechanism and forecast research. With its impervious property, moist potential vorticity can only move along isen- tropic surface, and its negative center and gradient acutely augmenting regions can only move along potential equivalent temperature surface too. Since move velocity and direction of the moist potential vorticity are knowable, the move velocity and direction of elevated duct are knowable and foreeastable, which presents a new way to elevated duct forecast.