These maps combine high-resolution daytime surface temperatures derived from satellite observations for both land and sea and display them with a common color scale. Displaying these high-resolution data with a common color scale makes evident the large difference between surface heating on land versus the sea. It also shows the relatively small seasonal variation in sea surface temperature over the globe relative to land temperatures. The larger seasonal variation in average temperature of the northern hemisphere relative to the southern hemisphere, a result of the larger land area in the northern hemisphere, is also evident.
Land surface temperature data are from the MODIS sensor on NASA's Terra satellite while the sea surface temperatures (SST) are from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) sensor on NASA's Aqua satellite. Both source datasets are monthly composite averages used to minimize holes in the daily data created by cloud cover. Despite the compositing, there are still holes in data coverage from cloud cover as well as gaps between land and sea data created by floating sea ice. These holes are filled by lower-resolution source data derived from the Atmospheric Infrared Sounder instrument (AIRS) instrument aboard the Aqua satellite.