Numerical investigation of boundary-layer evolution and nocturnal low-level jets: local versus non-local PBL schemes
Document ID: 256
Zhang, Kesu1
Mao, Huiting1
Civerolo, Kevin2
Berman, Stephen3
Ku, Jia-Yeong2
Rao, S. Trivikrama1
Doddridge, Bruce G.4
Philbrick, C. Russell5
Clark, Richard D.6
1 University at Albany, Department of Earth and Atmospheric Sciences, Albany, NY, U.S.A.
2 New York State Department of Environmental Conservation, Albany, NY, U.S.A.
3 College at Oneonta, Earth Sciences Department, Oneonta, NY, U.S.A.
4 University of Maryland, Department of Meteorology, College Park, MD, U.S.A.
5 The Pennsylvania State University, Department of Electrical Engineering, University Park, PA, U.S.A.
6 Millersville University of Pennsylvania, Department of Earth Sciences, Millersville, PA, U.S.A.
Abstract
Numerical simulations of the evolution of the planetary boundary layer (PBL) and nocturnal low-level jets (LLJ) have been carried out using MM5 (version 3.3) with four-dimensional data assimilation (FDDA) for a high pollution episode in the northeastern United States during July 15–20, 1999. In this paper, we assess the impact of different parameterizations on the PBL evolution with two schemes: the Blackadar PBL, a hybrid local (stable regime) and non-local (convective regime) mixing scheme; and the Gayno–Seaman PBL, a turbulent kinetic energy (TKE)-based eddy diffusion scheme. No FDDA was applied within the PBL to evaluate the ability of the two schemes to reproduce the PBL structure and its temporal variation. The restriction of the application of FDDA to the atmosphere above the PBL or the lowest 8 model levels, whichever is higher, has significantly improved the predicted strength and timing of the LLJ during the night. A systematic analysis of the PBL evolution has been performed for the primary meteorological fields (temperature, specific humidity, horizontal winds) and for the derived parameters such as the PBL height, virtual potential temperature, relative humidity, and cloud cover fraction. There are substantial differences between the PBL structures and evolutions simulated by these two different schemes. The model results were compared with independent observations (that were not used in FDDA) measured by aircraft, RASS and wind profiler, lidar, and tethered balloon platforms during the summer of 1999 as part of the NorthEast Oxidant and Particle Study (NE-OPS). The observations tend to support the non-local mixing mechanism better than the layer-to-layer eddy diffusion in the convective PBL.
Keywords: Blackadar PBL, Gayno–Seaman PBL, low level jets, meteorological modeling, MM5, planetary boundary-layer
| Citation: | "Numerical investigation of boundary-layer evolution and nocturnal low-level jets: local versus non-local PBL schemes", Zhang, K., H. Mao, K. Civerolo, S. Berman, J. Ku, S. T. Rao, B. G. Doddridge, C. R. Philbrick, R. D. Clark, Environmental Fluid Mechanics, Vol. 1, Issue 2, Wolters Kluwer, Dordrecht, The Netherlands, June 2001, pp. 171 - 208, DOI: 10.1023/A:101155740, ISSN: 1573-1510 |