Simulations of low-level jets at the Tiksi observatory (Laptev Sea, Siberia) using the regional climate model CCLM and evaluation using SODAR observations for the winter 2014/15

Low-level jets (LLJs) are important features in the Arctic climate system. The forecast of LLJs in polar regions is highly relevant for logistic operations, particularly for aircrafts, as well as for wind energy and air pollution transport. LLJs were investigated during 2014/15 at the Tiksi observatory in the Laptev Sea region. Besides the routine synoptic observations, data from a meteorological tower and SODAR (Sound Detection And Ranging) data were available from October 2014 to September 2015. The SODAR yields vertical profiles of the wind speed and wind direction with a vertical resolution of 10 m and a temporal resolution of 20 min (height range 30-550 m). These measurements were used to evaluate simulations performed with the regional climate model CCLM with 5 km resolution, which was run with nesting in ERA5 data in a forecast mode. CCLM simulations agreed well with near-surface and SODAR observations and represented the LLJ structures very well. However, SODAR measurements were mostly limited to wind speeds <12 m/s since the echo was typically too weak for higher winds. The CCLM data showed that LLJs occur frequently for wind speeds being too high for the SODAR. 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 LLJ events could be obtained only with the model data. The simulations showed that LLJs at Tiksi occur in about 70% of all profiles. When only LLJs in the range of the SODAR and with wind speeds of less than 10m/s were considered, only about 20% of all profiles showed LLJs, which was the same amount as found in the SODAR profiles. LLJs with at least 3 h duration were simulated for the same days as the observations in about 80% of all cases.