Mausam, (IS82), 33, I, 45·50

551.553 : 551.54

On dynamic initialization experiment in Indian region"

s. s. SINGH, (MRS.) A. A. KULKARNI and D. R. SIKKA

Indian Institute of Tropical Meteorology, Pune

( Received 19 October /979)

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ABSTRACf. A comparative performance of dynamic initialization (01) and static initializa.lion (SI) schemes for balancing initial wind and pressure fields for primitive equation barotropicmodel in Indian region has been investigated. For the purpose of dynamic initialization experimentthe set of model equations are integrated forward and backward around the initial time followingEuler backward time difference scheme without restoration of aoy variable. For static initializationthe nonlinear balance equation is solved to obtain the balance height field from non-divergent wind.

The resul ts of initialization experiments from both the schemes are compared and discussed. Theinitial fields from 01 scheme are found to be superior than those based on 51 scheme ,

1. Introduction

The large-scale atmospheric motions are norm­ally in quasi-nond ivergent hydrostatic balanceand small scale fluctuations are rapidly restoredtowards a balanced state througb tbe adjustmentprocesses and by dissipative forces. However, theobserved mass and motion fields show largeimbalances due to inaccurate observatio ns andanalyses. Thus, state of quasi-nondivergent hy­drostatic balance in the initial field known asinitialization is the basic prerequisite of inilialdata for successful integration of numericalmodels.

Basically, there are two approaches, viz., staticinitialization and dynamic initialization . Theexamples of static initializalion are:

(a) The solution of balance equation andomega equation and

(b) the normal mode initialization.

Normal mode initializalion is based on theidea of expanding initial data into normal modesor free oscillations of linear or nonlinear versionsof the model. The model amplitude thought tobe unrealistically large can be set to zero orconsiderably reduced. Recently a number of

"The paper was presented in the "Monsoon Prediction" symposium held al Indian Inst itute of Tec::hnolo8)'.New Delhi during 11· 18 March 1919.

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