基于LAS观测的城镇感热通量时空特征及影响因素

Spatial-temporal characteristics and influencing factors of sensible heat flux based on LAS in a town

利用2018年4月—2019年4月南京盘城大孔径闪烁仪(Large Aperture Scintillometer,LAS)观测数据,分析了城镇感热通量的时空变化特征及影响因素。结果表明:1)南京城镇感热通量呈单峰型日变化特征,白天明显大于夜间,且白天晴天明显大于阴天,夜间晴天略小于阴天,晴、阴天小时感热通量年平均分别在2.25~200.53 W·m^(-2)、13.10~132.52 W·m^(-2)波动。2)城镇感热通量夏季明显大于冬季,8月昼、夜分别为112.19、23.54 W·m^(-2),2月昼、夜分别为35.57、11.57 W·m^(-2)。3)晴天白天条件下,不同风向(通量贡献源区)城镇感热通量存在显著差异,即随着不透水层占比的增加,净辐射分配到感热通量的比例明显提高,当占比大于60%时提高趋势不明显。4)以莫宁-奥布霍夫长度判断大气稳定度为标准,C^(2)_(n)法在计算感热通量的5种大气稳定度判断方法中的误判率较低且数据源于LAS,是比较适宜城镇夜间大气稳定度的判断方法。5)在影响城镇感热通量的地表参数中,有效高度变化的影响最大,风速变化的影响较大特别在秋冬季节更为明显,波文比变化对城镇感热通量的影响较小,温度、地表粗糙度和零平面位移变化的影响可忽略不计。

This study analyzes the spatial-temporal characteristics and influencing factors of sensible heat flux based on data observed by the Large Aperture Scintillometer(LAS)from April 2018 to April 2019 in Pancheng town.The results indicate the following:1)In the town,the sensible heat flux exhibits a unimodal diurnal variation pattern,significantly larger during the daytime compared to the nighttime.The sensible heat flux is significantly higher on clear days than on cloudy days and slightly lower at night compared to cloudy days.The average hourly sensible heat flux ranges between 2.25—200.53 W·m^(-2)and 13.10—132.52 W·m^(-2)for clear and cloudy days,respectively.2)The sensible heat flux is significantly higher in summer than in winter.In August,the values during the daytime and at night are 112.19 and 23.54 W·m^(-2),respectively.In February,the values during the daytime and at night are 35.57 and 11.57 W·m^(-2),respectively.3)On clear days with inflows from different directions,notable differences in sensible heat fluxes are observed in the town.As the proportion of impervious layers increases,the proportion of net radiation allocated to sensible heat fluxes also increases significantly.When the proportion exceeds 60%,the upward trend becomes less evident.4)Using the Monin-Obukhov length as a criterion for judging atmospheric stability,the C^(2)_(n)method exhibits a low misjudgment rate among the five methods when using LAS data,making it a more suitable method for determining atmospheric stability at night in the town.5)Among the surface parameters affecting sensible heat flux,changes in effective height have the greatest impact.Changes in wind speed have a larger effect,especially in autumn and winter.The change in Bowen s ratio has a minor effect,while the effects of changes in temperature,roughness length,and displacement height are negligible.