A quasi-geostrophic omega equation was solved at seven standard levels over the Australian region for two synoptic situations, one analysed objectively and the other manually. Frictional and orographic influences, introduced at the lower boundary, did not extend to 500 mb but significantly affected lower levels. Decreasing the grid length resulted in a systematic increase in computed vertical velocities, but the scale characteristics of the geopotential and temperature fields determined whether there was additional synoptic detail in the vertical velocity pattern. A systematic decrease in computed vertical velocities was associated with the truncation error of low order approximations to the Laplacian and Jacobian operators. Much of the systematic effect of a coarser grid could be compensated by a higher order operator. Discrepancies between some large scale features of computed vertical velocity patterns and corresponding satellite cloud mosaics emphasized the need for a quasi-objective method of "feeding back" the cloud information to the geopotential and temperature analyses.
R.S. Seaman (Mon,) studied this question.