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Accuracy of Diagnostic Heat and Moisture Budgets Using SESAME-79 Field Data as Revealed by Observing System Simulation Experiments

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  • 1 National Center for Atmospheric Research, Boulder, CO 80307
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Abstract

The accuracy of diagnostic heat and moisture budgets using the AVE-SESAME 1979 data is investigated through a series of observing system simulation experiments. The four-dimensional (including time) data set provided by a mesoscale model is used to simulate rawinsonde observations taken during the AVE-SESAME 1979 regional-scale experiment. Budget calculations using the simulated data set show that the average root-mean-square error is about 5°C day−1 for the heat budget and 2 g kg−1 day−1 for the moisture budget, on a spatial scale of 550 × 550 km and a temporal scale of 6 h. These magnitudes of error indicate difficulties in diagnosing the heating rate in weak convective systems. However, for strong convective systems, such as the 10–11 April 1979 case, the convective effects can be estimated with the AVE-SESAME data. The influences of observational frequency, objective analysis, observational density, vertical interpolation, and observational errors on the budget results are also studied. It is shown that the temporal and spatial resolution of the SESAME regional network is marginal for diagnosing the convective effects on a horizontal scale of 550 × 550 km, and so improved resolution in space and time is needed in future field programs in order to obtain improved budget results.

Abstract

The accuracy of diagnostic heat and moisture budgets using the AVE-SESAME 1979 data is investigated through a series of observing system simulation experiments. The four-dimensional (including time) data set provided by a mesoscale model is used to simulate rawinsonde observations taken during the AVE-SESAME 1979 regional-scale experiment. Budget calculations using the simulated data set show that the average root-mean-square error is about 5°C day−1 for the heat budget and 2 g kg−1 day−1 for the moisture budget, on a spatial scale of 550 × 550 km and a temporal scale of 6 h. These magnitudes of error indicate difficulties in diagnosing the heating rate in weak convective systems. However, for strong convective systems, such as the 10–11 April 1979 case, the convective effects can be estimated with the AVE-SESAME data. The influences of observational frequency, objective analysis, observational density, vertical interpolation, and observational errors on the budget results are also studied. It is shown that the temporal and spatial resolution of the SESAME regional network is marginal for diagnosing the convective effects on a horizontal scale of 550 × 550 km, and so improved resolution in space and time is needed in future field programs in order to obtain improved budget results.

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