In order to determine the characteristics of dew amount and its inducing factors in the semi-arid area of loess hilly region of China, a year-long in-situ monitoring experiment was carried out in Ansai County of Shaanxi Province, using a leaf wetness sensor (LWS). Results showed that the annual cumulative dew amount in Ansai area in the water year of 2015-2016 was 29.85 mm with a daily maximum of 0.82 mm. The amount of dew condensation manifested two strong characteristics: the daily and seasonal changes. The majority of daily dew amount appeared from 18:00 o'clock to 7:00 o'clock, and the seasonal dew changes showed that the maximum yield of dew occurred in the autumn, followed by the summer, with the least amount in spring and winter. With respect to spatial and temporal distribution, rain and dew were highly complementary as dew occurred mainly in the cloudless nights, but it was more conducive to dew condensation during the days right before and after the rain events. Relative air humidity and the difference between air temperature and dew point were the main factors influencing dew condensation. Dew amount was significantly positively correlated to relative humidity (r=0.726, P<0.01), and negatively correlated to air temperature-dew point difference (r=-0.725, P<0.01). Wind speed and direction affected dew condensation to some extent, but dew amount was weakly correlated to wind speed (r=0.133, P<0.01) and wind direction (r=0.219, P<0.01).
为探明中国黄土丘陵半干旱区露水量特征及其影响因子,利用叶片湿度传感器(LWS)在陕西安塞县进行1年的监测试验.结果表明: 安塞地区2015—2016水文年露水总量为29.85 mm,日最大露水量可达0.82 mm.露水凝结量主要呈现日变化和季节变化两种特征,日变化过程中露水凝结量大多发生在18:00至次日7:00;季节变化中露水在秋季凝结量最大,夏季次之,春、冬季最少.在时空分布上,露水和降雨高度互补,露水大多产生于晴朗无云夜间,但降雨前后几天更有利于露水凝结.空气相对湿度和气温-露点差是影响露水凝结的主要因素,露水量与相对湿度呈显著正相关(r=0.726,P<0.01),与气温-露点差呈显著负相关(r=-0.725,P<0.01);风速、风向在一定程度上影响露水凝结,但风速(r=0.133,P<0.01)、风向(r=0.219,P<0.01)与露水量之间的相关性较弱.
Keywords: dew amount; drainfall; loess hilly region; meteorological factors.