Some Examples of Numerical Weather Prediction, with the Special Emphasis on the Development and Maintenance of Relatively Small Scale Cyclones

Abstract

The non-adiabatic heating due to the latent heat released by the condensation of water vapor through the simply parameterized convective activity is incorporated in the quasigeostrophic four-level numerical prediction model which is in operational use at Japan Meteorological Agency. This effect is so formulated that the heating takes place only over the cyclonic domain and the amount of heating is assumed to be proportional to the intensity of the relative vorticity at the lowest level. An air column resolved in the four level model is heated, at first over its lowest layer (700-900mb) alone (Version B), secondly over its lower two layers (500-700 and 700-900mb) at a certain distributive proportion of heating (Version C) and at the third over its whole three layers (300-500, 500-700 and 700-900mb) at some rate of distribution of heat (Version D).
Comparing a few examples of numerical weather prediction by means of the nonadiabatic model mentioned above with the observed patterns and with results of the operational routine model which has no parameterized convective heating (Version A), we observe that
(1) the relatively small scale cyclones and the cyclonic circulation of typhoons are well reproduced in surface prognostic charts by Versions B, C and D, though the predicted deepning of the disturbances does not cease, but that
(2) the retardation of the predicted displacements of typhoons is common in all the versions, and also
(3) when we cannot successfully forecast the upper level pattern, the inclusion of the heating exaggerates the error, and that
(4) Version B distorts the vertical structure of the disturbances, that Version C well describes the development of cyclones in the lower troposphere and that Version D seems to be appropriate for simulating the behavior of typhoons.