Vertical moistening by AMMA mesoscale convective systems.
Résumé
The apparent heat source Q1 and the apparent moisture sink Q2 are crucial parameters for precipitating systems studies since they allow evaluating their contribution in water and energy transport and inferring some of the mechanisms responsible for their evolution along their lifetime. In this paper, a new approach is proposed to estimate Q2 budgets from radar observations within precipitating areas at the scale of the measurements, i.e. either convective scale or mesoscale, depending on the selected retrieval zone. This approach relies upon a new analysis of the radar reflectivity based on the concept of the classical VAD analysis. Q2 is deduced from velocity and reflectivity fields, following five steps i) mixing ratio retrieval using empirical relations; ii) radial wind analysis using the VAD analysis; iii) radar reflectivity analysis using a new analysis called RAD (Reflectivity Azimuth Display); iv) retrieval of mixing ratio derivatives; and v) Q2 retrieval. The originality and the main interest of the present approach with respect to previous ones rely on the fact it uses radar data alone and is based on a relatively low cost analysis allowing future systematic application on large datasets. In the present paper this analysis is described and its robustness evaluated and illustrated on three cases observed during the AMMA SOP field experiment (15 June-15 September) by means of the RONSARD radar. Results are analysed in terms of the convective or stratiform character of observed precipitation.
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