SODAR observations and model simulations of the wind field structure in the atmospheric boundary layer at Severnaya Zemlya (Siberia) during YOPP

Abstract

Measurements of the atmospheric boundary layer (ABL) structure were performed for three years (October 2017–August 2020) at the Russian observatory “Ice Base Cape Baranova” (79.280° N, 101.620° E) using SODAR (Sound Detection And Ranging). These measurements were part of the YOPP (Year of Polar Prediction) project “Boundary layer measurements in the high Arctic” (CATS_BL). ABL measurements and near-surface observations were used for verification of the regional climate model COSMO-CLM (CCLM) with a 5 km resolution for 2017–2020. The SODAR showed a topographical channeling effect for the wind field in the lowest 100 m. The verification of the CCLM with near-surface data of the observatory showed good agreement. The comparison with SODAR data showed a positive bias for the wind speed of about 1.0-1.5 m/s. The CCLM data showed the frequent presence of low-level jets (LLJs) associated with the topographic channeling. Although SODAR wind profiles are limited in range and have a lot of gaps, they represent a valuable data set for model verification. However, a full picture of the ABL structure and the climatology of channeling events could be obtained only with the model data. LLJs were detected in 37% of all profiles and most LLJs were associated with channeling, particularly LLJs with a jet speed ≥15 m/s (which were 29% of all LLJs). The analysis of the simulated 10m wind field showed that the 99%-tile of the wind speed reached 18 m/s and clearly showed a dipole structure of channeled wind at both exits of Shokalsky Strait. The climatology of channeling events showed that this dipole structure was caused by the frequent occurrence of channeling at both exits. Channeling events lasting at least 12 h occurred on about 62 days per year at both exits.