This claim is a fundamental meteorological fact regarding the dynamics of precipitation types and does not require a formal citation.
The claim states a basic physical principle of atmospheric science: convective precipitation is characterized by strong updrafts that suspend and rapidly accumulate liquid or ice hydrometeors, leading to significantly higher rainfall rates than stratiform precipitation, which relies on widespread, gentle vertical motions. Because this relationship is a defining meteorological truism inherent to the classification of precipitation systems, it is treated as common knowledge not requiring specific paper citations.