On the Climatological Use of Radar Data Mosaics: Possibilities and Challenges

Continental mosaics of radar data have now been generated for more than 20 years. They 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 have value on their own and invariably trigger more questions about the processes causing these patterns but also suggest some answers. They also have considerable pedagogical value in illustrating in the classroom the impacts of different processes—such as sea–land breezes, topography, and seasons—on precipitation. In this work, U.S. mosaics of radar data from 1996 to 2015 are used to demonstrate the possibilities offered by such a dataset. Three topics are discussed: (i) climatologies and daily cycles of precipitation and convection, and what they can teach us about precipitation mechanisms; (ii) the spatial and temporal distribution of the appearance and occurrence of convection, and what it reveals about the importance of surface terrain properties for these events; and (iii) the power and challenges of looking for a small signal in such a large dataset using the influence of weekly activity cycles and cities on precipitation as an illustration.