Improvement and Verification of Freezing-Thawing Process Parameterization of BCC_AVIM Land Surface Process Model

Abstract

In this paper， considering the importance of the freezing-thawing process to the land-atmosphere interaction， and referring to the research and works on the parameterization scheme of the freeze-thaw process by domestic and foreign scholars， the parameterization scheme of the freezing-thawing process of the BCC_AVIM land surface process model is improved and vitrificated.The improvements mainly include： （1） adding the concept of supercooled water， improving soil freezing judgment conditions and updating standards for ice content； （2） adding the concept of equilibrium temperature to replace the constant freezing temperature in the original scheme； （3）Adding the impermeable fraction in hydraulic conductivity’s parameterization scheme.The modified and original schemes were used to simulate the two freeze-thaw processes of Maqu Station in 2018 -2019 and 2019 -2020 respectively.Comparing with the original scheme during the freezing and thawing process， it is found that modified scheme （1） increase the simulation of temperature in the frozen state， also reduce the temperature’s amplitude， and change the trend closer to the measurement data； （2） increase the simulation of water content in the frozen state， and the trend of water content of modified scheme has a better correlation with the measurement data； （3） delay the date of ice generation in the soil， advance the melting date of ice， and decrease the simulation of maximum ice content； （4） The simulation of the transition date at each stage of the freeze-thaw process is closer to the actual measurement； （5） The new scheme has a better simulation improvement effect for strong freeze-thaw years than weak freeze-thaw years.

Keywords

• freeze-thaw process
• bcc_avim land surface process model
• parameterization scheme
• soil water and heat