北京奥林匹克森林公园地表反照率动态及其影响因素

Dynamics of surface albedo and its controlling factors in Beijing Olympic Forest Park

地表反照率是地表能量和水文循环的关键要素。本研究基于2013—2015年对北京奥林匹克森林公园城市绿地生态系统气象要素的连续观测,探讨城市绿地生态系统地表反照率的动态及其影响因素。结果表明:地表反照率日变化为08:30—12:00逐渐减小,12:00—17:00比较接近,早晨与下午的反照率差异为0.03,地表反照率日变化不对称的主要因素是早晨植物叶片表面的露水;地表反照率的季节变化特征为冬季(0.15)>春季(0.13)>秋季(0.12)>夏季(0.11),在生长期内,地表反照率受空气温度和土壤含水量的共同影响;在展叶期,地表反照率主要受空气温度的影响,与空气温度呈线性负相关,而与土壤含水量没有相关性;在完全展叶期和落叶期,地表反照率受空气温度和土壤含水量共同的影响,与空气温度和土壤含水量均呈负指数相关,但当空气温度大于24.0℃时,空气温度对其无影响。

Surface albedo is a key factor of surface energy and hydrological cycles. Based on continuous monitoring of meteorological factors in an urban greenland in the Beijing Olympic Forest Park from 2013 to 2015,we explored the dynamics of surface albedo and its controlling factors.The diurnal variation in surface albedo gradually decreased from 08: 30 am to 12: 00 pm,and then remained relatively constant to 17: 00 pm. Surface albedo in the morning was 0. 03 higher than that in the afternoon. The asymmetry of daily surface albedo was due to the formation of dew on leaf surface in the morning. Surface albedo was the highest in winter( 0. 15) and lowest in summer( 0.11). Surface albedo in spring and autumn was 0.13 and 0.12,respectively. During the growing season,surface albedo was affected by temperature and soil water content. During leaf expanding period,surface albedo was mainly affected by air temperature but not by soil water content,showing a negative linear relationship with air temperature. During expanding leaf and deciduous periods,surface albedo was affected by both air temperature and soil water content,showing a negative exponential relationship with air temperature and soil water content. However,surface albedo was decoupled with air temperature when it was greater than 24.0 ℃.