This animation compares snow cover between December and February of 2001-02 with the same time period in 2002-03 using 8-day composite snow maps. The snow cover from the winter of 2002-03 is shown in white while the areas that had snow in 2001-02 but not in 2002-03 are shown in blue.

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over Asia 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 days 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 grey 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 landcover.

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over Europe 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 days 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 grey 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 landcover.

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over North America 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 days 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 grey 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 landcover.

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 days 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 grey 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 landcover.

This animation shows daily snow cover over North America from September 1, 2002 through June 30, 2003. The sea ice climatology indicates the average extent of the sea ice during each month.

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 days 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 grey 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 landcover.

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides data in 36 spectral bands, some of which are used in an algorithm to map global snow cover. The animation shows the dynamic behavior of the advance and retreat of continental snow cover over Asia for the winter of 2001-02 from MODIS-derived 8-day composite snow maps with a spatial resolution of about 5 km.

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides data in 36 spectral bands, some of which are used in an algorithm to map global snow cover. The animation shows the dynamic behavior of the advance and retreat of continental snow cover over Europe for the winter of 2001-02 from MODIS-derived 8-day composite snow maps with a spatial resolution of about 5 km.

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides data in 36 spectral bands, some of which are used in an algorithm to map global snow cover. In this animation, a time series of global snow cover from MODIS-derived 8-day composite snow maps with a spatial resolution of about 5 km shows the dynamic behavior of the advance and retreat of continental snow cover over North America during the winter of 2001-02.

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides data in 36 spectral bands, some of which are used in an algorithm to map global snow cover. The animation shows a time series of MODIS snow-cover maps of the Sierra Nevada Mountains in California, derived from MODIS-derived daily snow maps with 500-m resolution for the winter and spring of 2001.

During the last few decades, the permanent snow and ice on the summit of Mount Kilimanjaro has almost completely disappeared, at the rate of about a foot and a half of glacial ice lost per year. This loss is primarily due to increasing average annual temperatures in the region, and scientists are speculating that the glaciers could be completely gone from Kilimanjaro by the year 2015. This ice cap formed more that 11,000 years ago, and 80% of the ice fields have been lost in only the last century. The shrinkage is illustrated here in Landsat images from 1993, 2000, and 2002, with the 1993 image showing a significant ice cap and the more recent images showing only small glaciers and snow regions remaining.

The amount of snow covering the land has both short and long term effects on the environment. From season to season, snow coverage and depth affect soil moisture and water availability, which directly influence agriculture, wildfire occurrences, and drought. In the long term, the part of the Earths surface covered by snow reflects up to 80 or 90 percent of the incoming solar radiation as opposed to the 10 or 20 percent that uncovered land reflects, and this has important consequences for the Earths climate. Satellites identify the snow cover precisely by looking at the difference between light reflected off snow in the visible and the infrared wavelengths. This visualization shows the snow cover over North America from October, 2001, through April, 2002, as measured by the MODIS instrument on the Terra satellite. Since this instrument cannot measure snow cover through clouds, 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 covered in snow until the instrument takes a valid measurement showing less than 40% coverage in that same area. In this animation, snow coverage is measured every 8 days.

The amount of snow covering the land has both short and long term effects on the environment. From season to season, snow coverage and depth affect soil moisture and water availability, which directly influence agriculture, wildfire occurrences, and drought. In the long term, the part of the Earths surface covered by snow reflects up to 80 or 90 percent of the incoming solar radiation as opposed to the 10 or 20 percent that uncovered land reflects, and this has important consequences for the Earths climate. Satellites identify the snow cover precisely by looking at the difference between light reflected off snow in the visible and the infrared wavelengths. This visualization shows the snow cover in the Northern Hemisphere from September, 2002, through June, 2003, as measured by the MODIS instrument on the Terra satellite. Since this instrument cannot measure snow cover through clouds, 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. It is possible to see topographic features in the snow cover such as the Rocky Mountains and the Himalayas, and large snow coverage paths from storms that cross the plains of the United States and Russia can also be seen.

A time-series of snow cover derived from 8-day composite snow maps between December 2001 and February 2002 is animated.