What Determines the Number and the Timing of Pulses in Afternoon Precipitation in the Green Ocean Amazon (GoAmazon) Observations?
Yang Tian, Yunyan Zhang, Stephen A. Klein
Abstract
Abstract Using GoAmazon observations over the central Amazon, we investigate double‐pulse events of afternoon precipitation for the first time. Relative humidity is the dominant factor in determining the onset timing and the number of pulses of precipitation. A moister free troposphere on single‐pulse days features heavy precipitation in the early afternoon, which stabilizes the atmosphere and prohibits further convection. On early–onset double‐pulse days, weaker precipitation from shallower convection in the first pulse leads to less consumption of atmospheric instability, making the environment favorable for a second pulse of stronger precipitation. A cluster tracking algorithm using the scanning radar reflectivity is developed to examine the relationship between precipitation pulses. Through explicitly tracking convective clusters that exist from the first to the second pulse, convective aggregation plays a more dominant role to the survival of clusters with larger final size, and on average around 20% of cluster survivals are due to natural growth.