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2 results on '"Rauchöcker, Andreas"'

1. Cold‐air pool development in a small Alpine valley.

Author

Rauchöcker, Andreas, Rudolph, Alexander, Stiperski, Ivana, and Lehner, Manuela

Subjects
*METEOROLOGICAL research, *WEATHER forecasting, *HEAT losses, *ADVECTION, *VALLEYS, *COOLING, *ATMOSPHERIC temperature
Abstract

A field campaign in a valley near Seefeld, Austria, well known for the frequent occurrence of cold‐air pools, was conducted to identify the processes leading to the formation and erosion of the cold‐air pool. Here, we focus on a case study in January 2020 that featured cold‐air pool formation interrupted by a wind disturbance. Simulations with the Weather Research and Forecasting model were performed at a horizontal grid spacing of 40 m and compared with measurement results. The model was able to reproduce the intense cooling in the beginning of the night and the cold‐air pool erosion in the middle of the night caused by the wind disturbance, but stronger winds than observed prevented the cold‐air pool from fully re‐establishing in the model after the disturbance. The dominant cooling processes were long‐wave radiative heat loss and turbulent exchange, both of which are parametrized and cool the air locally. Advection was the most important warming contribution during the cold‐air pool disturbances, especially its cross‐valley and vertical components. Owing to numerical constraints and the shallow nature of the cold‐air pool, its extent was limited to the lowest model level. Further improvements to the cold‐air pool's representation in the model would require a finer grid resolution. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Characteristics of a cold air pool near Seefeld, Austria : numerical modeling results

Author

Rauchöcker, Andreas and Rauchöcker, Andreas

Abstract

Numerical simulations with the Weather Research and Forecast (WRF) model were used to study the processes involved in cold air pool formation at a valley near Seefeld, Austria. Due to the frequent occurrence of cold air pools at that valley and their role in improving the efficiency of technical snow production, a field campaign was conducted between December 2019 and March 2020 there. Based on that measurement data, undisturbed cold air pool formation periods were selected for simulation, one of which was described in more detail. Two WRF simulations were performed for that case, one with snow cover and one without snow cover. The simulation with snow cover proved superior in reproducing measurement results, although the cold air pool development was disturbed in both simulations. While the cold air pool dissolved occasionally during the night for both cases, they also included periods with significant accumulation of cold air at the valley floor. It was found that such cold air pooling periods were longer and more frequent and nighttime temperatures were lower if snow cover was included in the simulations. The cold air pool cooled by 6~K during the night for both simulations. However, warm air advection in the simulation with snow cover resulted in 2.5~K warming already before sunrise. The dominant cooling processes during cold air pooling periods were longwave radiative heat loss and turbulent exchange, both of which were parameterized. Vertical advection also contributed significantly to cooling, but only when horizontal advection caused warming at the same time. Both horizontal advection components were associated with warming and dissolution events of the cold air pool. Individual cooling rates and average contributions to temperature tendency were larger for the simulation with snow cover. Net tendency and its contributions of the simulation without snow cover were still larger than those reported for idealized simulations of a larger-scale alpine valley. In, by Andreas Rauchöcker, Masterarbeit University of Innsbruck 2022

Published
2022

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