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Convective Processes Resolved by a Mesoscale Rawinsonde Network

J. C. FankhauserNational Center for Atmospheric Research, Boulder, Colo.

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Abstract

Guidelines followed in designing and operating a special mesoscale rawinsonde network are discussed. Objective data reduction and analysis techniques are developed and applied to the wind, temperature and moisture data measured during a selected thunderstorm case. The goal is to appraise the sounding system's limitations and reliability for resolving the mesoscale circulations associated with convective processes. A consistent four-dimensional synoptic portrayal of the variables is achieved by accounting for balloon drift, differing station-to-station and sounding-to-sounding ascent rates, and departures from scheduled release time.Temporal variations in the spatial distributions of computed divergence and kinematic vertical motion are in good qualitative agreement with the location and intensity of thunderstorm radar echoes, after further objective adjustments are applied to compensate for the assumed character of wind measurement and analysis errors. For the purpose of assessing data and analytical credibility, independent estimates of the energy related to diabatic heating are obtained by evaluating thermodynamic energy and moisture continuity equations. Comparative results indicate that the network upper-air data and the methods adopted for its synthesis are internally consistent. On the other hand, the distribution and magnitude of the resolved kimematic and dynamic features demonstrate that the results are clearly a function of observational spacing and do not necessarily pertain to individual convective processes.

Abstract

Guidelines followed in designing and operating a special mesoscale rawinsonde network are discussed. Objective data reduction and analysis techniques are developed and applied to the wind, temperature and moisture data measured during a selected thunderstorm case. The goal is to appraise the sounding system's limitations and reliability for resolving the mesoscale circulations associated with convective processes. A consistent four-dimensional synoptic portrayal of the variables is achieved by accounting for balloon drift, differing station-to-station and sounding-to-sounding ascent rates, and departures from scheduled release time.Temporal variations in the spatial distributions of computed divergence and kinematic vertical motion are in good qualitative agreement with the location and intensity of thunderstorm radar echoes, after further objective adjustments are applied to compensate for the assumed character of wind measurement and analysis errors. For the purpose of assessing data and analytical credibility, independent estimates of the energy related to diabatic heating are obtained by evaluating thermodynamic energy and moisture continuity equations. Comparative results indicate that the network upper-air data and the methods adopted for its synthesis are internally consistent. On the other hand, the distribution and magnitude of the resolved kimematic and dynamic features demonstrate that the results are clearly a function of observational spacing and do not necessarily pertain to individual convective processes.

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