The impact of rain rate, raining patch size, and spacing on southeastern Pacific cloud fraction transitions

Abstract

Rain-induced cold pools are one mechanism by which transitions in cloud fraction in marine stratocumulus over the southeast Pacific occur. We use CloudSat/CALIPSO to identify raining patches within stratocumulus over the southeast Pacific, and then calculate the cloud fraction surrounding each raining patch, nearest-neighbor distance (spacing), mean rain rate, and raining patch size (extent). The spatial patterns show that as cloud fraction decreases and rain rate increases from east to west, a minimum in spacing exists between 80 °W-100 °W, but the maximum extent occurs further west. Holding spacing constant, cloud fraction decreases with rain rate but increases with extent. Additionally, cloud fraction is generally lower between 80 °W-100 °W when cells are large. This behavior is consistent with the idea that heavier rainfall associated with larger cells may result in possible cold pool interactions that could drive lower cloud fractions around the largest cells producing the most intense rainfall.