利用2013年10月1日至2014年5月31日黄河源区鄂陵湖流域的土壤温度资料首先划分土壤不同冻融阶段,然后在每个阶段各选取一次降雪过程,分析了降雪对土壤温湿变化的影响。结果表明:在土壤冻结阶段,雪后晴天(有雪覆盖)土壤净输出的热量减少,5 cm 和10 cm 土壤日最低温度明显升高,20 cm 土壤日最低温度升至0 ℃以上,导致20 cm 土壤达到完全冻结的时间延长;在土壤消融阶段,降雪当天土壤净输入的热量减少,5 cm 和10 cm 土壤日最高温度突降至0℃以下,导致5 cm 和10cm土壤达到完全消融的时间增加。在以上两个阶段的降雪过程中,积雪不仅可通过自身的消融增加浅层土壤湿度,还可通过改变浅层土壤温度间接影响浅层土壤湿度,而在土壤完全冻结阶段,积雪对土壤温度虽有影响,但对土壤湿度的直接和间接影响都较小。在整个土壤冻融阶段,与由土壤冻结和消融引起的土壤湿度变化相比,降雪引起的土壤湿度变化较小。
英文摘要:
As two integral parts of the cryosphere,snow cover and frozen soil both have important impacts on climate system,and the interaction between them makes it complicated to analyze the their influences on climate change in areas where snow cover and frozen soil coexist. In order to investigate the influence of snow cover on the thermal regime and hydrological process of frozen soil,different soil freezing and thawing stages was divided into soil freezing stage,frozen stage and thawing stage by soil temperature data observed from October1, 2013 to May 31,2014 in source region of the Yellow River,then the effects of snowfall on soil temperature and moisture were analyzed in each stage. During soil freezing stage,the ground surface net heat flux decreased during the snowfall day and the following sunny days(with snow cover),which resulted in an obvious increase of the soil daily minimum temperature at depths of 5 cm and 10 cm and led to a rise of the soil daily minimum temperature at depth of 20 cm to above 0 ℃. This could delay the soil freezing process at the depth of 20 cm. During soil thawing stage,the ground surface net heat flux decreased during the snowfall day. As a result,the soil daily minimum temperature at depths of 5 cm and 10 cm dropped to below 0 ℃ and thus prolonged the process of soil thawing at these layers. In the snowfall process of the soil freezing and thawing stages,snow cover could not only change the soil moisture by thawing,but also change soil moisture by influencing soil temperature. During soil frozen stage,snow cover had an effect on soil temperature,but it had little effect on soil moisture. During the soil freezing-thawing,compared to the change of soil moisture caused by soil freezing and thawing,the change of soil moisture caused by snow thawing is smaller.