Boundary Layer Studies above lake Erken using Modelling and UAV

Sammanfattning: Internal boundary layers (IBLs) above lakes, created primarily by the autumn differential of land and lake surface temperatures, present a unique way of studying the lake-atmosphere coupling within the boundary layer. The small and mobile unmanned aerial vehicles (UAVs) contribute to new research areas within the boundary layer, offering high spatial resolution measurements to complement already existing observations. In this study a UAV was used for profile measurements in order to investigate the presence of an IBL on October 17th, 2019, at lake Erken in central Sweden, and evaluate the suitability of using UAVs for these kinds of studies. The measurements were compared with WRF model simulations during the same time period and with a highest spatial resolution of 333.33 m, but neither the measurements nor the simulation found evidence of an IBL above Erken. To find the most suitable model setup, several different setups were tested in a sensitivity analysis of another case that investigated if the simulation could capture a sea breeze circulation and the warm air advection at Erken in early May, 2018. The model setup that best fit the measurements and observations were using the Kessler microphysics scheme, Quasi-Normal Elimination Scale (QNSE) boundary layer scheme and Community Land Model (CLM) 4.5 lake physics scheme, successfully capturing a sea breeze circulation on May 1st. The use of the CLM 4.5 lake physics scheme proved very important for obtaining accurate lake water temperatures. However, none of the model setups accurately captured the warm air advection and thus, further tests are required in order to produce improved results.