Intercomparison of Planetary Boundary-Layer Parametrizations in the WRF Model for a Single Day from CASES-99 |
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| Authors: | Hyeyum Hailey Shin Song-You Hong |
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| Institution: | (1) Global Environment System Research Laboratory, National Institute of Meteorological Research, 45 Gisangcheong-gil, Dongjak-gu, Seoul, 156-720, Republic of Korea;(2) Department of Atmospheric Sciences, Pusan National University, 30, Jangjeon-dong, Geumjeong-gu, Busan, 609-735, Republic of Korea;(3) Marine Meteorology Division, Korea Meteorological Administration, 45 Gisangcheong-gil, Dongjak-gu, Seoul, 156-720, Republic of Korea |
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| Abstract: | This study compares five planetary boundary-layer (PBL) parametrizations in the Weather Research and Forecasting (WRF) numerical
model for a single day from the Cooperative Atmosphere-Surface Exchange Study (CASES-99) field program. The five schemes include
two first-order closure schemes—the Yonsei University (YSU) PBL and Asymmetric Convective Model version 2 (ACM2), and three
turbulent kinetic energy (TKE) closure schemes—the Mellor–Yamada–Janjić (MYJ), quasi-normal scale elimination (QNSE), and
Bougeault–Lacarrére (BouLac) PBL. The comparison results reveal that discrepancies among thermodynamic surface variables from
different schemes are large at daytime, while the variables converge at nighttime with large deviations from those observed.
On the other hand, wind components are more divergent at nighttime with significant biases. Regarding PBL structures, a non-local
scheme with the entrainment flux proportional to the surface flux is favourable in unstable conditions. In stable conditions,
the local TKE closure schemes show better performance. The sensitivity of simulated variables to surface-layer parametrizations
is also investigated to assess relative contributions of the surface-layer parametrizations to typical features of each PBL
scheme. In the surface layer, temperature and moisture are more strongly influenced by surface-layer formulations than by
PBL mixing algorithms in both convective and stable regimes, while wind speed depends on vertical diffusion formulations in
the convective regime. Regarding PBL structures, surface-layer formulations only contribute to near-surface variability and
then PBL mean properties, whereas shapes of the profiles are determined by PBL mixing algorithms. |
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