陇中黄土高原夏季陆面辐射和热量特征研究

利用兰州大学半干旱气候与环境观测站(SACOL)的观测资料,分析了陇中黄土高原夏季陆面辐射和热量收支的特征.通过研究不同典型天气条件对陆面过程微气象特征的影响,发现地表反射率在晴天会出现早晨偏大的不对称结构;晴天与多云天气相比不平衡量较大,而阴天时的阵性降水会使局地能量收支出现不平衡.利用最小二乘法(OLS)线性回归得到的夏季平均不闭合度是19.6%.在半干旱区云和降水对辐射和能量收支的影响不容忽视,达到约25%的削弱程度,比极端干旱的敦煌荒漠区要大,又进一步证明了半干旱区夏季的平均气候特征与云量较多的多云天气(5≤Mean total cloud amount<8)接近.另外,7月日平均波恩比最大是4.1,平均是1.95,比极端干旱区的敦煌波恩比小1个数量级,说明榆中所处的黄土高原半干旱区比敦煌所处的极端干旱区在气候上要湿润很多.

Research on Characteristics of Land-surface Radiation and Heat Budget over the Loess Plateau of Central Gansu in Summer

Utilizing the data observed at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), characteristics of land surface radiation and energy budget over the Loess Plateau of central Gansu in summer are analyzed in this paper. By studying the impacts of different weather conditions on micrometeorological characteristics, the asymmetric structure of diurnal variation of surface albedo appears in the morning of sunny days with larger albedo values. The surface energy budget on a sunny day has a larger amount of imbalance, compared with that on a cloudy day. Besides ,the shower on an obscure day can also lead to large energy imbalance. The unclosure of energy balance obtained by using OLS(Ordinary Least Squares) linear regression method is 19.6%.In the semi-arid area，the clouds and the precipitation cause about 25％ disturbances to each component of energy balance. Weakening impact of clouds and precipitation on surface energy budget is apparent and much stronger than Dunhuang Gobi. Furthermore, it shows that the mean climatic characteristics in summer relatively close to those of cloudy days with more clouds(5≤Mean total cloud amount <8). Moreover, the maximum daily average Bowen ratio in July reaches 4.1 and the monthly mean value is 1.95. The Bowen ratio in Yuzhong is much smaller than that in Dunhuang Gobi, which indicates the semi arid area is more humid than the extreme arid area.