湿热地区雨水温度预测及降雨期间典型城市地表的能量特征

Rainwater Temperature Prediction and Typical Urban Surface Energy Characteristics During Rainfall in the Hot-Humid Region

降雨期间地表能量分配发生的变化,是认识和把握降雨对城市气候和建筑能耗影响的关键,而作为降雨期间特有的能量项,雨水显热在其中发挥重要作用。基于能量平衡理论和雨水温度测试仪的开发,本文通过夏秋冬三季降雨、微气候和地表能量的系统性观测,研究湿热地区雨水温度预测方法及降雨期间典型城市硬质水泥地面的能量特征。结果表明,开发的雨水温度测试仪可准确测量(量程0~100℃,精度±0.15℃,采样时间6 s)各等级降雨事件的近地雨水温度。降雨开始前后近地空气温度和湿球温度均大幅降低,并在降雨后0.2~1.1 h进入稳定期,稳定期中近地雨水温度较距地1.5m高处空气湿球温度恒定低3.0℃,据此可通过空气参数预测雨水温度。秋冬季降雨过程中,不透水地面持续释放下层蓄热,各散热项占比潜热(34%~65%)最大,对流换热(11%~34%)其次,净辐射(3%~21%)较小,雨水显热占比(5%~19%)在降雨强度较小时与净辐射相当,降雨强度较大时显著提升,最高可达46%。本研究在推进雨水温度和降雨期间地表能量变化认识的同时,为多雨湿热地区的城市气候和建筑热性能研究提供重要参考。

Changes in surface energy allocation during rainfall are the key to understanding and controlling the influences of rainfall on urban climate and building energy consumption,and as a specific energy term during rainfall,rain sensible heat plays an important role in it.Based on the energy balance principle and the development of the new rainwater temperature tester,this study investigated the predicting method for rainwater temperature and the energy characteristics of a typical urban cement surface during rainfall in the hot-humid region through systematic observations of precipitation,microclimate and surface energy in three seasons of summer,autumn and winter.The results show that the new tester can accurately measure the near-surface rainwater temperature in various rainfall events(range 0-100℃,accuracy±0.15℃,sampling time 6 s).The air temperature and wet bulb temperature near the surface both decreased significantly before and after the start of rain,and entered a stable stage within 0.2 to 1.1 h after rainfall.During the stable period,the near-surface rainwater temperature was consistently 3.0℃lower than the air wet-bulb temperature at a height of 1.5 m above the ground,based on which the rainwater temperature can be predicted by using the air parameters.In the rainfall events in autumn and winter,the impervious urban surface constantly released the heat storage of the layer beneath,and for the proportions of heat dissipation items,latent heat(34%-65%)was largest,followed by convection heat transfer(11%-34%),and net radiation(3%-21%)was smallest.The proportion of rain sensible heat(5%-19%)closed to that of net radiation when the rainfall intensity was small,while significantly increased up to 46%for large rainfall intensity.This study promotes the understanding of rainwater temperature and surface energy changes during rainfall,as well as provides important references for the studies on urban climate and building thermal performance in the rainy and hot-humid regions.