92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012
Quantitative Differences Between Lightning and Non-Lightning Convective Rainfall Events As Observed with Dual-Polarimetric Radar and MSG Satellite Data
Hall E (New Orleans Convention Center )
Retha Matthee, Univ. of Alabama in Huntsville, Huntsville, AL; and J. R. Mecikalski

Radar and lightning observations from the NASA African Monsoon Multidisciplinary Analyses (NAMMA) experiment are analyzed in concert with Meteosat Second Generation, Spinning Enhanced Visible and Infrared Image (SEVIRI) data to evaluate the differences between lightning and non–lightning producing convective storms. Many studies have been performed on convective storms using either radar, lightning or satellilte data alone, yet the combined use of these three datasets is unique. Data from a small population of convective events within NAMMA during August and September 2006 were determined to be optimal for this study as the cumulus cloud and convective storms initiated in clear–sky conditions (not obscured by higher cirrus), such that good SEVIRI data could be analyzed.

Observations from the NASA Polarimetric Doppler Weather Radar (NPOL) located at Kawsara, Senegal in West Africa were used in conjunction with SEVIRI infrared and retrieved microphysical fields to determine attributes of growing convective clouds (updraft strength, glaciation, cloud depth), while using Very Low Frequency (VLF) Arrival Time Difference (ATD) lightning data obtained from the UK Met Office. Once these three datasets were co–located in time and space, several events (lightning and non–lightning) were analyzed as clouds grew from the cumulus to cumulonimbus scale. As the clouds evolved, dual–polarimetric fields of horizontal reflectivity (Zh), differential reflectivity (Zdr), correlation (ρhv), as well as difference reflectivity (Zdp) were used to distinguish various hydrometeors from each other and the results were analyzed to help understand the changing microphysical structure within the clouds. Since ice processes are important for lightning generation, correlation between infrared indicators of cloud–top glaciation are compared in time and space, in addition to how SEVIRI–based cloud optical thickness and particle effective radius compare between storm types. The main attributes obtained from radar observations of cumulus that went on to produce lightning were that the reflectivity core descended before the first CG lightning occurred, reflectivities of greater than 30 dBZ at temperatures colder than -10°C (mixed phase) were recorded for approximately 30 minutes or more, coupled to fast cloud growth rates as well as higher volumes of ice. In contrast, non–lightning events showed slower cloud growth rates, and microphysical structures containing little ice microphysics. These results compare well with previous studies. Closer comparative analysis of the lightning events is presently being performed with the hopes of seeing variations in in–cloud to cloud–top relationships between satellite and radar fields.

The presentation will highlight all main findings of this study, while providing a discussion on how the combined use of data from multiple platforms can be used to improve weather observations, toward enhanced products for weather forecasting.

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