【作者】 李春为；

【导师】 傅培健；

【作者基本信息】 兰州大学 ， 大气物理学与大气环境， 2008， 硕士

【摘要】 兰州大学半干旱气候和环境观测站（SACOL）地处中国黄土高原西南部,属于典型的半干旱地区。SACOL作为唯一在黄土高原地区不间断观测的CEOP站点,自2005年9月建站以来取得了很多宝贵的观测资料。本文利用SACOL站2006年5月1日至2007年4月30日的边界层气象常规数据、动量通量、CO₂和H₂O通量、各辐射分量以及潜热和感热通量资料,对该站点的平流场特征、湍流场特征,以及各辐射分量变化规律和地表能量平衡问题进行了分析。结论如下:1、SACOL常年盛行东南风和西北风;水平风速的日变化与垂直风速和摩擦风速的日变化相比表现了很好的一致性;湿度和气压具有明显的日变化特征;CO₂浓度与CO₂通量的日变化规律基本相似,呈现出单峰单谷型;SACOL所处地区生态系统薄弱,植被的光合与吸收作用对该地区CO₂浓度的影响表现的不明显。2、由于海拔比平原地区高以及晴天次数相对较多,所以该地区日照资源丰富;地表反照率季节变化明显,数值介于同处于西北地区的张掖绿洲和敦煌戈壁之间,地表反照率受地表植被和降雪等天气过程影响明显;大气逆辐射与地面长波辐射随大气温度和地表温度变化明显。3、土壤温度日变化表现为准正弦曲线,峰值发生时间随土壤深度而滞后,日变化振幅随深度而减小。降水与土壤湿度有着很好的相关性,深层土壤的湿度的变化与浅层相比存在一定的位相滞后。4、白天,从上午到下午,能量闭合率是逐渐升高的。夜晚,能量不闭合情况比较显著的原因主要是因为湍流强度低。对于SACOL地区,由于空气湿度很低,导致感热通量比潜热通量要大很多,波文比年平均值为1.42。5、利用同处于半干旱区的通榆观测站2003年6-8月的观测资料,对其地表能量平衡状况进行分析,并将SACOL与之对比:两地的净辐射大小基本相同,但潜热和感热通量相差很多,可见虽然同属半干旱区,由于夏季干湿状况不同,两地的地表能量分配差别很大。更多还原

【Abstract】 Semi-Arid Climate and Environmental Observatory of Lanzhou University （SACOL） is located in southwest China’s Loess Plateau and it is typically semi-arid area. As the only uninterrupted observation CEOP site in Loess Plateau region, since the foundation in September 2005, SACOL has achieved a lot of valuable data.In this paper, we use the conventional meteorological data of the boundary layer, momentum flux, CO₂ and H₂O flux, the radiation components and the latent heat and sensible heat flux of SACOL from May 1st, 2006 to April 30th, 2007 to analyze the average field characteristics, the characteristics of turbulence and the change law of radiation and the surface energy balance problems.Our conclusions are as follows:1. Southeast winds and northwest winds prevail in SACOL all the year round; the diurnal variation of horizontal wind speed and vertical wind speed, friction wind speed show good consistency; humidity and atmosphere pressure have obvious diurnal variation characteristics; the change laws of CO₂ concentration and fluxes of CO₂ are basically similar, presenting a single peak-valley-type; the ecological system in SACOL is weak; consequently, the effect of vegetation photosynthesis and absorption upon the concentration of CO₂ in this region is not obvious.2. Because the elevation of SACOL is higher than plain areas and there are relatively more sunny days, the resources of sunshine in SACOL region is rich ; the surface albedo’s seasonal change is obvious, and its value is between that of Zhangye oasis and Dunhuang Gobi which are located in the northwest areas. The albedo is affected significantly by surface vegetation, snowfall and other weather conditions. The atmospheric counter radiation and terrestrial long-wave radiation change with the air temperature and surface temperature significantly.3. The diurnal variation of soil temperature performs like sine curve. The peak time lags with the increase of soil’s depth, and the amplitude of diurnal variation decreases with depth. The precipitation and soil moisture have a very good correlation; and the moisture variation of deep soil has a certain phase lag compared to shallow soil.4. The energy closure rate is gradually increasing from morning to afternoon. The main reason why energy imbalance is more serious at night is the low intensity of turbulence. In SACOL area, as the air humidity is very low, sensible heat flux is much larger than latent heat flux. The annual average ratio of Bowen is 1.42.5. By using the observation data from June to August 2003 of Tongyu Observation which is also located in the semi-arid area, we analyze its surface energy balance condition and make comparison with SACOL: the net radiations of the two places are basically the same, but latent heat and sensible heat flux of the two places are different obviously. Although they are located in the same semi-arid area, owing to different humidity condition in summer, their surface energy distributions are quite different.更多还原