论文部分内容阅读
土壤水汽吸附是陆面非降水性水分的重要来源之一,尤其在干旱和半干旱地区其贡献有时甚至能达到与降水同样量级,对旱作农业和生态环境具有重要影响.但由于对土壤水汽吸附观测比较困难,国际上对该问题研究至今仍不多.本文利用L-G大型称重式蒸渗计观测与微气象和常规气象观测相结合,建立了土壤水汽吸附的定量观测估算方法.在此基础上,分析了典型半干旱区定西的近地层大气风、温和湿等气象要素及土壤湿度、温度和地表可利用能量等土壤环境要素对土壤水汽吸附的影响特征,研究了土壤水汽吸附量、吸附频率和吸附强度的日变化和年变化及其随天气条件的变化特征,对比分析了土壤水汽吸附量对陆面水分收支的贡献.研究发现,半干旱区的土壤水汽吸附受多种小气候要素和土壤环境因素共同影响,一般在近地层相对湿度在6~5 0%、风速在3~4 m s-1、湿度日变幅较大及出现逆湿和弱不稳定,且土壤含水量较低和地表温度不太高的情况下,土壤水汽吸附现象更容易发生,土壤湿度与水汽吸附之间具有负反馈机制.而且,水汽吸附频率和吸附量具有很明显的日和年变化特征,水汽吸附量变化明显受吸附频率控制.水汽吸附主要发生在下午;年峰值出现在1 2月份,谷值出现在6月份,其变化特征具有明显的区域特点.旱季水汽吸附量明显超过了降水对水分收支贡献.
Soil water vapor adsorption is one of the important sources of non-precipitation water on land surface, especially in the arid and semi-arid areas, and its contribution sometimes reaches the same magnitude as precipitation, which has a significant impact on dry farming and ecological environment.But due to soil Water vapor adsorption observation is more difficult, the international research on the issue is still not much.This paper uses the LG large-scale weighing vaporization meter observation and micro-meteorology and conventional meteorological observation combined to establish a quantitative observation and estimation of soil moisture adsorption. Based on this, the meteorological elements such as atmospheric wind and mild wetness of the near-surface layer in the typical semi-arid area and the impact of soil environmental factors such as soil moisture, temperature and available energy on soil moisture adsorption on soil moisture were analyzed. , Diurnal and annual variation of adsorption frequency and adsorption intensity and its variation with the weather conditions, the contribution of soil water vapor adsorption to the water budget of land surface was comparatively analyzed.It was found that the adsorption of soil water vapor in the semi-arid region was affected by a variety of Microclimate factors and soil environmental factors together, usually in the near-surface layer of relative humidity 6 ~ 50%, wind speed in 3 ~ 4 m s-1, humidity Soil moisture vapor adsorption phenomenon is more likely to occur under the condition of large daily variation, adverse and weak instability, low soil moisture content and low surface temperature. There is a negative feedback mechanism between soil moisture and water vapor adsorption. Moreover, the frequency and amount of adsorption of water vapor have obvious diurnal and annual variation characteristics, and the change of water vapor adsorption quantity is obviously controlled by the adsorption frequency. The water vapor adsorption mainly occurs in the afternoon; the annual peak appears in January and the valley value appears in June, The characteristics of its variation have obvious regional characteristics.The water vapor adsorption capacity in the dry season obviously exceeds the contribution of precipitation to the water budget.