Abstract
Soil moisture (SM) plays an important role in the climate system, and the effects of SM anomalies on climate can persist from month to season. The seasonal frozen-thawing zone (SFTZ) in the northern hemisphere (NH), which is associated with large inter-annual variability in spring SM, is important from land–atmosphere interaction perspective. In this study, by assimilating spring SM in the SFTZ through indirect soil nudging (ISN) in the Weather Research and Forecasting (WRF) model, the effects of correcting spring SM biases in the SFTZ on subsequent summer precipitation simulations in the NH are investigated. The results indicated that correcting spring SM biases in the SFTZ improves the subsequent summer precipitation simulations in the NH. Correcting spring SM biases in the SFTZ significantly adjusts energy and moisture evolution on the land surface from spring to summer. Specifically, the correction of SM biases by assimilating SM in SFTZ in the spring can clearly reduce the biases of sensible heat flux (SH) and latent heat flux (LH) in the summer. This affects land–atmosphere interactions over NH, leading to correcting the negative biases of the geopotential height in the middle troposphere in June and July, as well as larger biases of water vapor transport and its divergence during the summer. The results imply that spring SM in the SFTZ is a potential signal for predicting summer precipitation in the NH.
Highlights
Land–atmosphere interactions play a critical role in climate variation
This study investigated the impacts of correcting Soil moisture (SM) biases in the seasonal frozen-thawing zone (SFTZ) over the Northern Hemisphere (NH) on the subsequent summer precipitation simulation, using the indirect soil nudging (ISN) method in the Weather Research and Forecasting (WRF) model
The results suggest that correcting biases of spring SM in the SFTZ can improve the land–atmosphere interaction processes in the spring and summer
Summary
Land–atmosphere interactions play a critical role in climate variation. Soil moisture (SM) variability changes surface albedo and soil heat capacity, which affect the surface sensible heat flux (SH), latent heat flux (LH), and radiation budget (e.g., Amenu et al, 2005; Song et al, 2009). Statistical analysis suggests that the seasonal frozen-thawing zone (SFTZ) in the NH shows the largest inter-annual variability in spring SM (Yang et al, 2016) This suggests that the characteristics and patterns of atmospheric circulation will be changed by the significant SM anomalies induced by freeze–thaw processes in soil when air passes through the mid-latitude SFTZ during the spring (Yang et al, 2016; Yang and Wang, 2019a, Jiang and Wang, 2020). Considering the evident SM biases in SFTZ (Yang et al, 2016), the contribution of correcting spring SM in the SFTZ to summer precipitation predictions remains unclear. (3) What are the possible mechanisms linked to the improvement in summer precipitation simulations by correcting spring SM biases over the SFTZ?
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
