中国北方不同气候区晴天陆面过程区域特征差异

Regional Differences in the Characteristics of Clear-Sky Land Surface Processesin Distinct Climatic Zones over Northern China

采用2008年7～9月份观测的中国干旱—半干旱区实验观测协同与集成研究资料,将我国北方干旱—半干旱区根据气候类型和地理位置划分为西北干旱区、黄土高原区和东北冷区三个区域,分析了干旱—半干旱区陆面热量平衡和辐射平衡日变化的区域差异。结果显示:不同气候区域的地表辐射和能量过程差异明显,而这种差异主要源于大气和土壤中可利用水分的不同,因而区域差异的分析也可归结于探讨陆面辐射和能量过程对不同强弱干旱气候的响应特征。在辐射平衡的比较方面:晴天的总辐射在各区域呈现随纬度上升而递减的趋势;反射辐射在东北冷区最小而在西北干旱区最大;大气逆辐射在东北冷区最明显,在黄土高原区最弱;地表长波辐射在西北干旱区最强而在东北冷区最弱。在能量平衡方面:西北干旱区的地表可利用能量的70%左右用于加热大气,小部分消耗于蒸发和加热土壤;黄土高原区可利用能量中用于加热大气的能量占30%,蒸发水分的消耗能量约50%;东北冷区接近一半的可利用能量用于蒸发,另一半的大部分消耗于加热大气。

By dividing the semi-arid and arid regions into three parts：arid region in the northwest,Loess Plateau,and cold region in the northeast,the regional differences in the diurnal variation of land surface radiation and energy processes in the semi-arid and arid regions are investigated using the data measured during July and September,2008,provided by the Experimental Co-observation and Integral Research in the Semi-arid and Arid Regions over northern China.The results show that pronounced regional differences in land surface radiation and energy processes are seen in distinct climatic zones and the differences are primarily attributed to the regional differences in available water either in land or in the atmosphere.Consequently,the studies of the regional differences in land surface processes to a large extent are the analyses on how the arid climate for different intensities affects the land surface processes.For radiation components,downward short-wave radiation decreases with the latitude increasing,and the upward short-wave radiation is largest in the arid region and smallest in the cold region.The downward long-wave radiation is strongest in the cold region and weakest in the Loess Plateau while the upward long-wave radiation is obvious in the arid region and weak in the cold region.For energy components,70% of the land surface available energy is consumed by heating the atmosphere in the arid region,and the remaining 30% is used for evaporation and heating the soil.In the Loess Plateau,however,only 30% of energy goes to atmosphere heating and 50% is lost to evaporation.Roughly half the energy is lost to evaporation in the cold region,and most of the other half is used for heating atmosphere.