Evaluation of Vertical Profiles and Atmospheric Boundary Layer Structure Using the Regional Climate Model CCLM during MOSAiC

Abstract

Regional climate models are a valuable tool for the study of the climate processes and climate change in polar regions, but the performance of the models has to be evaluated using experimental data. The regional climate model CCLM was used for simulations for the MOSAiC period with a horizontal resolution of 14 km (whole Arctic). CCLM was used in a forecast mode (nested in ERA5) and used a thermodynamic sea ice model. Sea ice concentration was taken from AMSR2 data (C15 run) and from a high-resolution data set (1 km) derived from MODIS data (C15MOD0 run). The model was evaluated using radiosonde data and data of different profiling systems with a focus on the winter period (November–April). The comparison with radiosonde data showed very good agreement for temperature, humidity, and wind. A cold bias was present in the ABL for November and December, which was smaller for the C15MOD0 run. In contrast, there was a warm bias for lower levels in March and April, which was smaller for the C15 run. The effects of different sea ice parameterizations were limited to heights below 300 m. High-resolution lidar and radar wind profiles as well as temperature and integrated water vapor (IWV) data from microwave radiometers were used for the comparison with CCLM for case studies, which included low-level jets. LIDAR wind profiles have many gaps, but represent a valuable data set for model evaluation. Comparisons with IWV and temperature data of microwave radiometers show very good agreement.

Evaluation of the Planetary Boundary Layer Height From ERA5 Reanalysis With MOSAiC Observations Over the Arctic Ocean

“…Additionally, a selection of the near-surface tower measurements including 2-m pressure, temperature, humidity, u of the wind component, and v of the wind component were processed into hourly-averaged values around the times of the radiosonde profiles. Although the sounding data sets used in this study have been assimilated into ERA5 (Heinemann et al, 2023;Kirbus et al, 2023;Svensson et al, 2023), there may remain a notable bias in the reanalysis data attributed to disparities between the physical assumptions made by the ERA5 model and the actual observations (Fréville et al, 2014;Yu et al, 2021). Furthermore, ERA5 primarily relies on model simulations, with observations serving as a supplementary source rather than the primary driver of the data (Belmonte Rivas & Stoffelen, 2019;Hersbach et al, 2020).…”

“…A recent year-long expedition, the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), conducted in the central Arctic from October 2019 to September 2020, has provided valuable highresolution, year-round atmospheric observation data (Shupe et al, 2022) offering a valuable opportunity to assess the quality of reanalysis PBLH under the rapidly changing "new Arctic" climate. The sounding data sets utilized in this study have been assimilated into ERA5 (Heinemann et al, 2023;Kirbus et al, 2023;Svensson et al, 2023). However, a discernible bias persists in the assimilated data, stemming from disparities between the physical assumptions of the ERA5 model and actual observations (Fréville et al, 2014;Yu et al, 2021).…”