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Modification of the convective adjustment time‐scale in the Kain–Fritsch eta scheme for the case of weakly forced deep convection over the Tibetan Plateau region
Author(s) -
Wang Chenghai,
Wu Di,
Zhang Feimin
Publication year - 2019
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3535
Subject(s) - convection , parametrization (atmospheric modeling) , convective available potential energy , plateau (mathematics) , meteorology , precipitation , geology , weather research and forecasting model , convective inhibition , advection , turbulence , scale (ratio) , climatology , atmospheric sciences , mechanics , environmental science , physics , mathematics , natural convection , combined forced and natural convection , radiative transfer , mathematical analysis , quantum mechanics , thermodynamics
There is general uncertainty about the representation of clouds and convective precipitation in almost all models. Efforts to handle the convective parametrization scheme (CPS) in the grey zone (∼1–5 km horizontal grid spacing) are still imperative to the community, especially for the case of weakly forced deep convection. This study proposes a new convective adjustment time‐scale ( τ ) for the Kain–Fritsch eta (KFeta) scheme in the Weather Research and Forecasting (WRF) model at high resolution, which differs from the current scale‐aware function. The validation was made in three cases of weakly forced deep convection over the Tibetan Plateau. The results confirmed that modifying τ improves the simulation performance. In particular, the modified τ improved the simulated precipitation pattern, horizontal scale and intensity over the original scheme, which could be attributed to the enhanced rate at which convective instability generated by external factors (e.g. large‐scale advection and surface turbulent fluxes) is removed by the parametrized convection. When τ is appropriately chosen, the CPS can be implemented in high‐resolution simulations.