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Drigeard E.,CNRS Laboratory of Physics and Meteorology | Fontaine E.,CNRS Laboratory of Physics and Meteorology | Wobrock W.,CNRS Laboratory of Physics and Meteorology | Schwarzenbock A.,CNRS Laboratory of Physics and Meteorology | And 8 more authors.
Journal of Applied Meteorology and Climatology | Year: 2015

This study addresses clouds with significant ice water content (IWC) in the stratiform regions downwind of the convective cores of African squall lines in the framework of the French-Indian satellite Megha-Tropiques project, observed in August 2010 next to Niamey (13.5°N, 2°E) in the southwestern part of Niger. The objectives included comparing the IWC-Z reflectivity 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 large ice crystals in the reflectivity of centimeter radars through analysis of their microphysical characteristics as ice crystals larger than 5mmfrequently 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. © 2015 American Meteorological Society.

Rennie S.J.,Center for Australian and Weather Climate Research
Meteorological Applications | Year: 2014

Australia's migratory insects, including the Australian Plague Locust (Chortoicetes terminifera Walker), were observed with Doppler weather radar during the austral spring and summer of 2010-2011. On occasion, the presence of a dumbbell pattern in the reflectivity indicated insects taking a common orientation. Using the radial velocity, the average orientation and direction of travel of the insects were determined. Common orientation was most clearly observed shortly before or after dawn, and occasionally in the evening. However, signs of orientation were observed in different migrant populations throughout the day. The cases selected for this study described a daily cycle of migration phases and associated atmospheric conditions. The weather was characterized using surface observations, analysis charts and numerical weather prediction model fields. Migrating insects were profuse during convective weather. Insects often aggregated into layers, particularly in the vicinity of the nocturnal inversion. © 2013 Royal Meteorological Society.

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