A comparison of airborne in situ cloud microphysical measurement with ground-based C-band radar observations in deep stratiform regions of African squall lines

Abstract : This study addresses clouds with significant ice water content in the stratiform regions downwind of the convective cores of African squall lines in the framework of the French–Indian satellite project MEGHA-TROPIQUES, observed in August 2010 (MT2010) next to Niamey (2°W, 13.5°N) in the southern western part of the Niger. The objectives included comparing the IWC-Z relationship for precipitation radars in deep stratiform anvils, collocating reflectivity observed from ground radar with the calculated reflectivity from in-situ microphysics for all aircraft locations inside the radar range and interpreting the role of the large ice crystals on the reflectivity of cm radars by the analysis of their microphysical characteristics as ice crystals larger 5 mm frequently occurred. It was found that in the range of 20-30 dBZ IWC and C-band reflectivity are not really correlated. Cloud regions with high IWC caused by important crystal number concentrations can lead to the same reflectivity factor as cloud regions with low IWC formed by a few millimeter sized ice crystals.