The term "snow cover" refers to deposits of snow on the surface of the Earth. Some snow deposits, as seen at the poles and at very high altitudes, are permanent, and others are seasonal and might wax and wane over time. Meteorologists monitor snow cover as part of their overall surveys of weather conditions. The levels of snow cover can provide important clues to environmental health and might help with forecasting activities.
Satellites can take images of the Earth to collect snow cover data. As long as clouds do not obscure the image, the satellite can quickly identify the reflective areas where snow is present and can beam this data to collectors on Earth. Computer programs can analyze satellite data to return a finished map showing how much snow is present in the surveyed area. Researchers also can manually test the snow to determine the depth of the deposits and identify densely layered deposits known as snow pack.
In climate terms, the presence or absence of snow can be an indicator. If snow lingers unusually late or melts early, it can be a sign that the climate in the area is shifting. Although some variation in timing is expected from year to year, it should be consistent overall. Likewise, very late or early snows in the fall and winter can also be a sign for concern.
The reflective nature of snow allows it to play a role in global temperatures, and it is of interest to climate scientists. They might look at data on snow deposition over time to connect the snow with fluctuations in temperature. They also can create models to see what would happen in the event of a radical increase or decrease in snow cover worldwide.
Additionally, snow provides a source of water. Thin snow cover can be a warning sign to prepare for possible drought in the summer and fall, because there will not be enough snowmelt to meet the needs of a population if enough rain does not fall. This can affect waterways as well as human populations. Water management authorities track snow cover data to determine whether they need to take conservation measures or other steps to protect the water supply.
Recent snow cover data is often available through government agencies that handle weather and related topics. It also can be found through colleges and universities that have climate and meteorology programs. Some organizations create computer applications that provide regular automatic updates for people who want to closely track snow conditions.