NASA MODIS Image of the Day: January 25, 2007 – Cirrus Reflectance
Cirrus clouds are thin, wispy clouds high in the sky that can be hard to see with the unaided eye. They typically form at an altitude of 6,000 meters (20,000 feet) or higher, where the air temperature is below freezing. Cirrus clouds are composed mostly of tiny ice crystals.
They are scientifically interesting because they allow most incoming sunlight to pass through them, but they help to contain heat emitted from the surface. Thus, cirrus clouds exert a warming influence on Earth’s surface. Key questions scientists are trying to answer today is: Will more cirrus clouds form as Earth continues to warm this century, thereby establishing a positive feedback loop? And, how will the additional cirrus clouds that form from airplane contrails affect Earth’s climate?
These maps of cirrus were produced using data collected by the MODIS on the Aqua satellite. The MODIS sensor has a unique band for measuring infrared light at a wavelength of 1.38 micrometers — a wavelength that NASA scientists recently found is highly sensitive to cirrus.
In these images, bright white pixels indicate regions completely covered by cirrus clouds. Greyish-white pixels show partial cirrus cover and dark pixels indicate little or no cirrus. The images represent the average cirrus cloud fraction over the Earth during December 1, 2006 and January 1, 2007. This image was retrieved NEO (Nasa Earth Observations) where a number of MODIS datasets can be downloaded. You can view a higher resolution image here.
