Links between Snow Cover, Surface Skin Temperature, and Rainfall Variability in the North American Monsoon System

Abstract

The influence of land?atmosphere interactions on the variability of the North American monsoon system (NAMS) is investigated using the Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder, the Climate Prediction Center (CPC) gauge precipitation, and observed snow water equivalent (SWE). Three hypotheses are tested regarding the connection between land surface variables and precipitation in the NAMS region. First, there is a weak negative correlation between 1 April SWE and subsequent surface temperature in the southern Rocky Mountains (SRM) region. However, this connection persists only until June and, therefore, cannot directly influence monsoon rainfall in July and August. Second, there is a negative correlation between SRM surface temperature and NAMS precipitation during the monsoon season, rather than the positive correlation previously proposed. Third, there is a highly significant negative correlation between rainfall and surface temperature within the NAMS region. On the monthly timescale, surface temperature decreases by ?4 K per 1 mm day?1 increase in rainfall, consistent with a positive soil moisture?rainfall feedback. The substantial variability of SRM skin temperature (?10 K) may modulate the temperature gradient between land and ocean. However, these skin temperature anomalies persist only for ?1 month, so their effects are variable throughout the monsoon season.