Dr. Leighton presented a seminar titled “Characterizing Raindrop Size Distributions Observed in Hurricanes”.
RESUMEN:
One of the main applications of radar measurements is to estimate rainfall rate based on its power-law relationships with radar reflectivity. Different relationships have been obtained for different weather scenarios. Hurricanes, in comparison with other severe weather systems, have a much longer life cycle and travel across much greater zonal and meridional extent. Therefore, in order to accurately estimate the rainfall for a specific time at a specific location in a hurricane, the power-law relationship with constant coefficients needs to be improved. This study demonstrated that the rainfall estimation can be improved greatly by including the information of drops sizes. In numerical models, the accurate representation of raindrop size distributions (as well as ice, snow and graupel) is a crucial component of the microphysics parameterization scheme and can be obtained by fitting an analytical function to the observed raindrop size distributions. We fit gamma distributions to the raindrop size distributions observed in hurricanes using a refined fitting method that greatly improved the fitting performance. The results from the fitted gamma distributions show that intercept and slope are closely related. An empirical relation deduced from least-square fitting captures 92% of the variance in the data. The remaining 8% can be captured by including the impact of liquid water content. This empirical relation between intercepts and slopes can be used to improve the analytical representations of raindrop size distributions in bulk microphysics parameterization schemes.
A recording of the presentation is available here.
