Lesson 1
Meteorological Satellite Orbits
Lesson 2
Review of Radiative Transfer
Lesson 3
Visible Image Interpretation
Lesson 4
Infrared Image Interpretation
Lesson 5
Multispectral Image Interpretation
Lesson 6
Fires & Aerosols
Lesson 7
Lesson 8
Lesson 9
Fog and Stratus
Lesson 10
Lesson 11
Lesson 12
Lesson 13
Global Circulation
Lesson 14
Synoptic Scale
Lesson 15
Global Circulation
Lesson 16
Satellite Oceanography
Lesson 17

Snow Index - NDSI

Identifying snow cover is important for weather and hydrological forecasting. To detect the presence of snow, recent satellite instruments include observations at 0.66 and 1.6mm. The atmosphere is transparent at both these wavelengths, while snow is very reflective at 0.66 mm and not reflective at 1.6mm . The Normalized Difference Snow Index:


NDIV is used to monitor the extent of snow cover. At visible wavelengths (e.g. 0.66 microns), snow cover is just as bright as clouds, and is therefore difficult to distinguish from cloud cover. However, at 1.6 microns, snow cover absorbs sunlight, and therefore appears much darker than clouds. This allows the effective discrimination between snow cover and clouds. Values of NDSI < 0.4 typically indicate the presence of snow. The following image demonstrates the ability to separate clouds from snow using observations at these wavelengths.

MODIS image

Red regions are snow covered, white regions are cloudy.

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