Echo climatology, impact of cities, and initial convection studies: New horizons opened using 17 years of Conterminous US radar composites

Radar data offer information on precipitation climatology that is simply not available or archived elsewhere: how often does it rain at any particular location? At what time? And with what intensity distribution? What are the geographical and temporal patterns of precipitation occurrence, formation, and decay? What is the climatology of severe weather? Answers to these questions invariably trigger more questions about the processes causing these patterns as well as suggest some answers. These tend to be of a different nature than those arising from individual case studies because the specificity of atmospheric conditions leading to one storm instead of another are being washed out. What are left are the persistent features that often or always influence precipitation occurrence which, in the end, are the most important to get right both in the context of process studies and of numerical modeling.

Here, U.S. composites of radar data from 1995 to 2013 are used to demonstrate the possibilities offered by such a data set. Three topics are touched: a) daily and annual cycles of precipitation and convection, and what they can teach us about precipitation mechanisms; b) the influence of weekly activity cycles and of cities on precipitation, and on the power and challenges of looking for a small signal in even such a large dataset; and c) the spatial distribution of the appearance of convection, and what it reveals on the importance of terrain properties for these events.