Premium
Daytime convective development over land: A model intercomparison based on LBA observations
Author(s) -
Grabowski W. W.,
Bechtold P.,
Cheng A.,
Forbes R.,
Halliwell C.,
Khairoutdinov M.,
Lang S.,
Nasuno T.,
Petch J.,
Tao W.K.,
Wong R.,
Wu X.,
Xu K.M.
Publication year - 2006
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 - 10.1256/qj.04.147
Subject(s) - sunrise , diurnal cycle , noon , convection , environmental science , daytime , entrainment (biomusicology) , climatology , sunset , convective available potential energy , meteorology , atmospheric sciences , sensible heat , convective inhibition , convective boundary layer , latent heat , boundary layer , planetary boundary layer , geology , geography , mechanics , combined forced and natural convection , natural convection , physics , astronomy , rhythm , acoustics , turbulence
This paper investigates daytime convective development over land and its representation in single‐column models (SCMs) and cloud‐resolving models (CRMs). A model intercomparison case is developed based on observations of the diurnal cycle and convection during the rainy season in Amazonia. The focus is on the 6 h period between sunrise and early afternoon which was identified in previous studies as critical for the diurnal cycle over summertime continents in numerical weather prediction and climate models. This period is characterized by the formation and growth of a well‐mixed convective boundary layer from the early morning temperature and moisture profiles as the surface sensible‐ and latent‐heat fluxes increase after sunrise. It proceeds with the formation of shallow convective clouds as the convective boundary layer deepens, and leads to the eventual transition from shallow to deep precipitating convection around local noon. To provide a benchmark for other models, a custom‐designed set of simulations, applying increasing in time computational domain and decreasing spatial resolution, was executed. The SCMs reproduced the previously identified problem with premature development of deep convection, less than two hours after sunrise. The benchmark simulations suggest a possible route to improve SCMs by considering a time‐evolving cumulus entrainment rate as convection evolves from shallow to deep and the cloud width increases up to an order of magnitude. The CRMs featuring horizontal grid length around 500 m are capable of capturing the qualitative aspects of the benchmark simulations, but there are significant differences among the models. Two‐dimensional CRMs tend to simulate too rapid a transition from shallow to deep convection and too high a cloud cover. Copyright © 2006 Royal Meteorological Society