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Dynamical models of two‐dimensional downdraughts
Author(s) -
Thorpe A. J.,
Miller M. J.,
Moncrieff M. W.
Publication year - 1980
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.49710644906
Subject(s) - inflow , parametrization (atmospheric modeling) , outflow , mechanics , sink (geography) , storm , computer simulation , numerical models , jump , numerical modeling , meteorology , physics , environmental science , geology , geophysics , cartography , quantum mechanics , geography , radiative transfer
Observational and numerical model data have indicated the crucial role of the downdraught in the motion, structure and regeneration of severe storms. This paper considers downdraught dynamics in two dimensions, using both a numerical and an analytical model. In the numerical model the downdraught is produced and maintained by a constant heat sink. The adjustment of an ambient inflow, and the resultant downdraught and potential regeneration of storm cells, is simulated. To elucidate physical principles, steady analytical models are also described in which a simple parametrization of downdraught thermodynamics is used. Two distinct types of individual draught dynamics, labelled symmetric and jump, have been identified allowing a qualitative description of six dynamically consistent updraughts and downdraughts. In particular, a cold symmetric downdraught and a cold jumptype updraught are analysed, the former having negative, the latter positive outflow shear. These analytical solutions agree well with steady states developed by the numerical model. The numerical model is also used to describe the propagation of downstream and upstream gust fronts, and these results are in good agreement with atmospheric and tank data.