The MODIS Brightness Temperature, Band 31 layer is the brightness temperature, measured in Kelvin (K), calculated from the top-of-the-atmosphere radiances. It does not provide an accurate temperature of either clouds nor the land surface, but it does show relative temperature differences which can be used to distinguish features both in clouds and over clear land. It can be used to distinguish land, sea ice, and open water over the polar regions during winter (in cloudless areas).

The MODIS Brightness Temperature layer is calculated from MODIS Calibrated Radiances and is available from both the Terra (MOD02) and Aqua (MYD02) satellites. The sensor and imagery resolution is 1 km, and the temporal resolution is daily.

References: MODIS - MODIS Calibrated Radiances