Skip to main content
U.S. flag

An official website of the United States government

Observing Sierra Nevada Mountain Snowpack 2000-2019 with Terra MODIS

Video Transcript
Right-click and save to download

Detailed Description

The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor is located aboard NASA’s Terra and Aqua satellites. These data are crucial for studying changes that have occurred on the surface of the Earth, including during times of drought.

This video uses images produced from Terra MODIS Surface Reflectance data over the Sierra Nevada Mountain Range to show changes in the snowpack from 2000 to 2019. You might notice these images don’t look like what the earth looks like to our eyes. That is because these images are shown using a blue-SWIR-SWIR band combination (3-6-7). This band combination is used to map snow and ice because snow and ice are very reflective at blue wavelengths in the visible part of the spectrum. So here snow and ice will appear as bright red-orange, vegetation as green, bare soil and deserts as bright cyan, clouds as white and peach, and water as dark blue or black.

Observe how the changes in the snowpack (in red) are shown in the image to see how much snow exists in the Sierra Nevada mountains. Scientists use measurements of snowpack as a key indicator of drought, as the water from the melting snowpack is a source of fresh water for Californians. The California Department of Water Resources measures the snowpack in the mountains every year on April 1, to provide consistent data and to study the size of the snowpack. Notice how in the drought years, for example 2003 and 2015, the snowpack is smaller in size than it is during the wetter years, for example 2005 and 2019. Lesser amounts of snowpack can be problematic during times of drought, as water resources for California residents can be limited. To learn more about these data and other data products distributed by the LP DAAC, please visit

The LP DAAC is one of twelve NASA Earth Observing System Data and Information System (EOSDIS) DAACs and operates as a partnership with the United States Geological Survey (USGS). It is located at the USGS Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. 

Learn more about the LP DAAC at Want updates sent directly to your inbox? Sign up for the LP DAAC listserv:




Public Domain.