Infrared Weather Satellite Images
The satellite also measures the temperature of the clouds and the surface of the Earth with an infrared sensor. This allows for the detection of changes in the temperature of clouds and that of the surface during the day and at night. Clouds are usually colder than the surface (land or water). The temperature of the clouds also indicates how tall they are since temperature is inversely proportional to height in the atmosphere. With colorized infrared imagery, gray is relatively warm, blues cooler, red indicates clouds that are the coldest, tallest, and most likely to produce rain.
The colder the cloud the more likely it is to produce rain. The temperature structure of clouds also tells the meteorologist how hard it may be raining and whether the storm may be producing severe weather. In the absence of clouds, the satellite measures the temperature of the surface, which could be land or ocean.
The infrared image can also be used to monitor sea-surface temperature (SST). Since about 70% of the Earth is ocean, this allows the scientist to study how changes in SST (such as El Nino and La Nina) are related to global weather events (such as droughts, hurricanes, and floods).