8.5 Characterization of turbulence over a complex terrain in real convective boundary layer

Tuesday, 21 June 2016: 4:30 PM
Bryce (Sheraton Salt Lake City Hotel)
Raj K. Rai, PNNL, Richland, WA; and L. K. Berg, B. Kosovic, J. D. Mirocha, M. Pekour, and W. J. Shaw

Finely resolved numerical simulation of the atmospheric boundary layer (ABL) provides a deep insight into the processes taking place within the ABL, such as transport of mass and momentum. This work employs large eddy simulation (LES) within the framework of Weather Research and Forecasting (WRF) model to study the ABL turbulence in a real convective ABL over an area of complex terrain. The WRF configuration includes six nested domains – 3 WRF mesoscale and 3 LES microscale, with the finest LES horizontal grid spacing of 30 m. The simulation results from the center of the innermost LES domain (5 x 5 km) are compared with the data from tower-mounted sonic anemometers in terms of first and second order statistical quantities at two heights. The results for the mean, turbulence, and energy spectrum show good agreement between the measured and simulated data. Furthermore, the analyses of the LES data from other spatial locations exhibits a great deal of spatio-temporal variability. Similarly, a TKE budget analysis performed to the LES data shows that there is a comparable contribution from horizontal component of the budget terms in developing the TKE in this area of complex terrain. In future, such spatio-temporal variation of turbulence in regions of complex terrain can be quantified by comparing the turbulence observed over flat terrain in a similar stability condition. The observed variability of turbulence, then, can be included in mesoscale model with the goal of improving the turbulence parameterization.
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