七月中、低纬地区定常波动和加热场的模拟特征

SIMULATED PROPERTIES OF STATIONARY WAVES AND HEATING FIELDS IN THE MID-AND-LOW LATITUDES IN JULY

本文利用P-σ混合坐标原始分程球带模式的最新版本,对七月中、低纬地区的定常波动及非绝热加热场进行了数值模拟。结果表明,模式成功地模拟出了北半球夏季对流层中波数为2的定常波动。高层波峰出现在大陆,波谷出现在海洋上,低层则相反。南半球的副热带高压带也模拟出来了。降水量的模拟也是成功的,特别是位于ITCZ中的积云对流性降水。加热场的模拟结果指出,七月份的热源区除了主要分布在北半球的几个主要大陆上,还分布在热带海洋上ITCZ所在区;其余的广大洋面则显示出冷源的性质。其中热带海洋的热源以潜热加热为主(主要分布于大气的中高层),大陆上的热源有的以感热为主(主要分布于大气的低层),有的仍以潜热加热贡献较大。海洋的冷源是由长波辐射冷却造成的。

The latest version of a global numerical model with zonal domain, p-sigma vertical coordinate and primitive equations is used to simulate the stationary waves and diabatic heating fields in the mid-and-low latitudes in July. The results show that the model successfully simulated the stationary waves with wave number 2 in the mid troposphere in northern summer with the wave peaks and troughs in the upper level appearing over the continents and the oceans, respectively. The case is just reversed in the lower level. The subtropical high belt in the Southern Hemisphere and the rainfall amount, especially that due to convection within the ITCZ, are also well simulated. The simulated heating fields reveal that the main heating sources are located over the continents of the Northern Hemisphere and the ITCZ belt in the tropical oceans and sinks are over the vast areas of the oceans. The heat sources over the oceans come from the condensation at the upper levels, while some of the heat sources over land areas are induced by the sensible heating in the lower layers of the atmosphere and some of them are mainly resulted from latent heating. The sinks over the oceans are induced by long wave radiative cooling.