海盐核对华南沿海一次暖区暴雨的影响

Effect of sea salt aerosols on a warm-sector heavy rainfall event over coastal Southern China

采用中尺度数值天气模式WRF-Chem 4.1.2,模拟了2014年在华南沿海地区发生的一次暖区强降水事件。通过进行3个不同海盐核排放强度(CTL,LOW,HIGH)试验,从降水落区、水成物分布、微物理过程以及潜热释放方面,探讨了海盐气溶胶浓度对暖区暴雨的影响。研究结果表明,海盐核浓度对降水落区有一定的影响,低海盐核排放下的降水区域更分散,而高海盐核排放下的降水区域更集中。低(高)海盐核排放情况下,降水中的云凝结核浓度减少(增加)、雨水和霰的混合比增加(减少)、云微物理过程尤其是云水自动转化成雨水及云水被雨水收集过程增强(减弱)、潜热释放增加(减小)以及上升运动增强(减弱),导致累计降水增多(减小)及降雨率增大(减小)。

This study used the Weather Research and Forecasting model coupled with Chemistry(WRFChem)version 4.1.2 to simulate a warm-sector heavy rainfall(WSHR)event that occurred over coastal Southern China in 2014.To investigate the effects of the concentration of sea salt aerosols(SSA)on the development of WSHR,different levels of SSA emission were incorporated in three separate experi‐ments(CTL,LOW,and HIGH).The distribution of precipitation and hydrometeors,the microphysical processes,and the release of latent heat resulting from the rainfall in all three simulations were ana‐lyzed.Results show that SSA mass concentration can affect the rainfall area:the LOW experiment shows dispersed rainfall,whereas the HIGH experiment presents concentrated rainfall.Under the situa‐tion of low(high)SSA emission:the concentration of cloud condensation nuclei during rainfall de‐creases(increases),the mixing ratio of rain and graupel increases(decreases),and microphysical pro‐cesses,particularly the automatic conversion of cloud water into rainwater and accretion of cloud water by rain,are enhanced(weakened),more(less)latent heat is released,and the updrafts are enhanced(weakened);these result in an increase(decrease)of accumulated precipitation and rain rate.