黄河源区若尔盖站冻融期土壤温、湿度的模拟与改进

Simulation and Improvement of Soil Temperature and Moisture at Zoige Station in Source Region of the Yellow River during Freezing and Thawing

利用陆面过程模式CLM3.5对黄河源区若尔盖站进行了一年的数值模拟试验,通过比较土壤温度、土壤含水量的观测值与模拟值,检验了该模式在黄河源季节性冻土地区的模拟能力。结果表明,模式对土壤温度的模拟,非冻结期较好,深层土壤温度稍偏高;冻结期模拟值偏低,冻结深度偏大。对土壤含水量的模拟,在冻融期出现了较大偏差,含水量骤降(冻结)、骤增(消融)的时间均较观测提前。模式土壤热传导参数化方案中的土壤基质热导率计算偏大是造成土壤温、湿度偏差的主要原因。将Johansen土壤基质热导率方案替换了原模式参数化方案后,模拟结果有一定的改进,土壤温度暖舌、冷舌的模拟深度显著减小,冻结期土壤温度模拟偏低的现象也得到了改进,土壤含水量骤降、骤增的时间与观测更为接近。

Using observational data from Zoige Station in the source region of the Yellow River,the model CLM3.5 was employed to do a single point simulation.Comparison of the observed and simulated values of soil temperature and moisture verifies the applicability of the model in the seasonal frozen soil area of the source region of the Yellow River.The simulated soil temperature is better during the non-freeze period,though the values are much higher at the deep layer than the observation.But a bias occurs during the freezing period.The simulated temperature is lower and the simulated freezing depth is deeper than the observation.The simulation of soil moisture indicates the start time of freeze and thaw is ahead of time.The thermal conductivity of soil matrix in the model is too large may be the main reason for the deviation.So the sensitive experiment which replaces the original parameterization scheme with the Johansen scheme was done.The new simulated result shows the significant improvement to the original.It matches the observation more closely in the freezing depth and the start time of freeze and thaw.The phenomenon which the simulated temperature is lower than the observation during the freezing period is also improved to some extent.