Brief communication: Improving ERA5-Land soil temperature in permafrost regions using an optimized multi-layer snow scheme

• Published in: The Cryosphere
• Main Authors: Cao, Bin, Arduini, Gabriele, Zsoter, Ervin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: article; Verlagsveröffentlichung; permafrost; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-16-2701-2022; https://noa.gwlb.de/receive/cop_mods_00061829; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00061213/tc-16-2701-2022.pdf; https://tc.copernicus.org/articles/16/2701/2022/tc-16-2701-2022.pdf

We previously reported a notable warm bias in ERA5-Land soil temperature in permafrost regions that was supposedly being caused by an underestimation of snow density. In this study, we implemented and evaluated a new multi-layer snow scheme in the land surface scheme of ERA5-Land, i.e., HTESSEL, with revised snow densification parameterizations. We compared permafrost soil temperatures from the numerical experiments with observations and the original ERA5-Land with a single-layer snow scheme. The revised HTESSEL significantly improved the representation of soil temperature in permafrost regions compared to ERA5-Land. The daily warm bias in winter was reduced by about 0.6–3.0 ∘C across the 522 observing stations in high-latitude permafrost regions, and the resulting modeled near-surface permafrost extent was improved (11.0–12.9×106 km2 during 2001–2018), comparing reasonably with observed estimates for continuous and discontinuous permafrost areas. We therefore suggest that a better-resolved snow scheme with a multi-layer snow profile should be included in next-generation reanalyses as a first step towards improving the representation of permafrost.