Global Daytime Distribution of Overlapping Cirrus Cloud from NOAA's Advanced Very High Resolution Radiometer

Data from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) instrument are used to provide the mean July and January global daytime distributions of multilayer cloud, where multilayer cloud is defined as cirrus overlapping one or more lower layers. The AVHRR data was taken from multiple years that were chosen to provide data with a constant local equator crossing time of 2:30-3:00 PM. The cloud overlap detection algorithm is used in NOAA's Extended Clouds from AVHRR (CLAVR-x) processing system. The results between 60°N and 60°S indicated that roughly 20% of all clouds and roughly 40% of all ice clouds were classified as cirrus overlapping lower cloud (cirrus overlap). The results show a strong July – January pattern that is consistent with the seasonal cycle in convection. In some regions, cirrus overlap is found to be the dominant type of cloud observed. The distributions of overlapping cirrus cloud presented here are compared with results from other studies based on rawinsondes and manual surface observations. Comparisons are also made with another satellite derived study that used coincident infrared and microwave observations over the tropical oceans during a six month period