North Pole - Winter Snow & Sea Ice [HD]

Описание: This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over the Northern Hemisphere from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior day's value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a gray cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in land cover.

Credit: NASA/Goddard Space Flight Center, The SeaWiFS Project and GeoEye, Scientific Visualization Studio, and George Riggs (NASA/SSAI).