Changes in Cloud Cover, Precipitation, and Summer Temperature in North America from 1982 to 2009

Abstract

n North America (NA), trends in summer surface air temperatures vary on decadal time scales, and some regions have temperature trends that exhibit a lack of warming in 1982?2009. From a surface energy balance perspective, the summer mean daily maximum temperature change can be affected by changes in solar heating that are associated with cloud cover change and changes in surface evaporative cooling caused by different precipitation and land surface wetness, but little is known about regional cloud cover and precipitation feedbacks to decadal temperature trends. Changes in cloudiness and precipitation and their connections with summer mean daily maximum temperature variations in NA were investigated using observation-based products of temperature and precipitation and satellite-derived cloud cover and radiation products. Results show that summer mean daily maximum temperature variance is largely explained by changes in cloud cover and precipitation. Cloud cover effect dominates at the high and middle latitudes of NA, and precipitation is a more dominant factor in the southern United States. The results indicate that cloud cover is either the major indicator of the summer mean daily maximum temperature changes (the effect) or the important local factor influencing the changes (the cause). Cloud cover is negatively correlated with mean daily maximum temperature variation in spring and autumn at the middle latitudes of NA but not at the high latitudes.