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

• Main Authors: Cao, Bin, Arduini, Gabriele, Zsoter, Ervin
• Format: Text
• Language: English
• Published: 2022
• Subjects: permafrost
• Online Access: https://doi.org/10.5194/tc-2022-71; https://tc.copernicus.org/preprints/tc-2022-71/

We previously reported a notable warm bias in ERA5-Land soil temperature in permafrost regions that was supposedly being caused by an underestimation of the 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 parametrizations. 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, and the resulting modelled near-surface permafrost extent was improved (11.0–12.9 × 10 6 km 2 ), 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.