黄土高原陇东地区有着特殊的气候背景和下垫面,对这一地区陆气相互作用特征和影响因素的观测分析对改进和发展陆面过程模式以及气候变化研究有重要意义。利用陇东平凉陆面过程与灾害天气观测研究站连续一年的陆面过程观测资料,分析了雨养农田降水量、土壤含水量、辐射、反照率和能量通量的季节变化,以及降水、土壤含水量和农业生产活动对能量分配的影响。结果表明,陇东地区降水量季节分布不均,土壤含水量有明显季节差异,随降水有明显波动;辐射通量的季节变化较为规律,短波辐射的日均值受天气状况影响,波动较大;地表反照率呈明显的季节变化,全年正午反照率最大值为0.83,出现在降雪后,生长季随着作物的生长,反照率下降至0.2以下,农作物收割以后的裸土反照率随降水变化明显,反照率与土壤体积含水量呈明显的线性相关关系;湍流能量通量日循环和季节变化明显,地表能量分配在很大程度上受降水影响,同时农业生产活动也对其有较大影响,主导能量通量有较大的月际波动,潜热通量月平均日变化峰值最大为240.8 W · m~(-2),出现在5月,感热通量为192.5 W · m~(-2),出现在4月;在年尺度上,正午净辐射多被感热通量消耗,感热通量约占35%,潜热通量约占32%,低于灌溉农田;在冬小麦快速生长季(3 5月),潜热通量约占34%,远低于灌溉的冬小麦田,研究站点的蒸散发过程受到水分限制。
英文摘要:
It's important to understand the land-atmosphere interactions over the semi-arid area of Loess Plateau, which featured by special climate and unique underlying surfaces. Seasonal variability of precipitation,soil moisture, radiation,albedo and energy fluxes,especially the influence of rain,soil moisture and agricultural production activities to the energy partition,were analyzed systematically,using a full year observations over a rain-fed cropland at the Pingliang Land Surface Process & Severe Weather Research Station. The results showed that the seasonal distribution of precipitation was uneven,gave rise to the significant seasonal differences in soil moisture. Radiative components had seasonal cycles. Shortwave radiation fluctuated with weather conditions,while longwave radiation was less affected. Surface albedo had significant seasonal variations:the maximum midday mean value(0.83)occurred after snow,then dropped to less than 0.2 during crop growth,afterwards,it fluctuated with precipitation after crop harvest. There was a linear relationship between albedo and soil moisture. Turbulent energy fluxes had diurnal cycle and seasonal variations. The partition of energy was largely affected by the changes in precipitation as well as agricultural production activities. The main consumer of the available energy was different among months,monthly mean diurnal cycle of the latent(sensible)heat flux attained maximum in May(April),which was 240.8(192.5)W·m~(-2). On an annual scale,the largest consumer of midday net radiation was sensible heat flux,which accounted for about 35% of Rn. While the latent heat flux was about 32% of Rn,which was lower than irrigated croplands. During the rapid growing season of winter wheat(March to May),the average midday LE/Rn was about 34%,which was much lower than irrigated winter wheat agro-ecosystem, indicating that it was water limited in our study site.