GLDAS Snowpack 2000 - Present

<div>Melting snowpack is a key part of the spring water budget in many parts of the world. Like a natural reservoir, snowpack stores winter precipitation and releases it as runoff over the course of many months. Where summer rains are scarce snowpack provides crucial base flow without which rivers might go dry. Where summer rains are torrential, this exacerbates the flooding and can lead to the loss of lives. </div><div><br /></div><div>This map contains a historical record showing the water stored in snowpack during each month from March 2000 to the present. It is not a map of snow depth, but of snow water equivalent, which is the amount of water that would be produced if all the snow melted. For fresh snow, this can be anywhere from 5% to 20% the depth of the snow, depending on temperature (snow tends to be fluffier at lower temperatures). As the snow settles and melts, it becomes more dense, up to 40% or 50% in the spring. Temperature, albedo (the reflective property of the snow), density, and volume all affect the melting rate of the snowpack. Additionally, melting rate is influenced by wind, relative humidity, air temperature and solar radiation.</div><div><br /></div><div><font size='3'>Dataset Summary<br /></font><br /></div><div>The GLDAS Snowpack layer is a time-enabled image service that shows average monthly snowpack from 2000 to present, measured in millimeters of snow water equivalent. It is calculated by NASA using the Noah land surface model, run at 0.25 degree spatial resolution using satellite and ground-based observational data from the <a href='https://ldas.gsfc.nasa.gov/' target='_blank'>Global Land Data Assimilation System</a>  (GLDAS-2.1). The model is run with 3-hourly time steps and aggregated into monthly averages. Review the complete list of model <a href='https://ldas.gsfc.nasa.gov/gldas/GLDASforcing.php' target='_blank'>inputs</a><span>, explore the </span><a href='https://hydro1.gesdisc.eosdis.nasa.gov/data/GLDAS/GLDAS_NOAH025_M.2.1/' target='_blank'>output</a> data (in GRIB format), and see the full Hydrology <a href='https://disc.gsfc.nasa.gov/datasets?keywords=Hydrology' target='_blank'>Catalog</a> for all related data and information!</div><div><br /></div><div><b>Phenomenon Mapped:</b> Snowpack</div><div><b>Units:</b> Millimeters</div><div><b>Time Interval:</b> Monthly</div><div><b>Time Extent:</b> 2000/01/01 to present</div><div><b>Cell Size: </b>28 km</div><div><b>Source Type:</b> Scientific</div><div><b>Pixel Type</b>: Signed Integer</div><div><b>Data Projection:</b> GCS WGS84</div><div><b>Mosaic Projection:</b> Web Mercator Auxiliary Sphere</div><div><b>Extent:</b> Global Land Surface</div><div><b>Source:</b> NASA</div><div><b>Update Cycle:</b> Sporadic</div><div><font size='3'><br /></font></div><div><font size='3'>What can you do with this layer?</font></div><div><font size='3'><br /></font></div><div>This layer is suitable for both visualization and analysis. It can be used in ArcGIS Online in web maps and applications and can be used in ArcGIS Desktop. Is useful for scientific modeling, but only at global scales. The GLDAS snowpack data is useful for modeling, but only at global scales. </div><div><br /></div><div>By applying the &quot;Calculate Anomaly&quot; processing template, it is also possible to view these data in terms of deviation from the mean, instead of total snowpack. Mean snowpack for a given month is calculated over the entire period of record - 2000 to present.</div><div><br /></div><div><b>Time:</b> This is a time-enabled layer. By default, it will show the first month from the map's time extent. Or, if time animation is disabled, a time range can be set using the layer's multidimensional settings. If you wish to calculate the average, sum, or min/max over the time extent, change the mosaic operator used to resolve overlapping pixels. In ArcGIS Online, you do this in the &quot;Image Display Order&quot; tab. In ArcGIS Pro, use the &quot;Data&quot; ribbon. In ArcMap, it is in the 'Mosaic' tab of the layer properties window. The minimum time extent is one month, and the maximum is 8 years. </div><div><br /></div><div><b>Important:</b> You must switch from the cartographic renderer to the analytic renderer in the processing template tab in the layer properties window before using this layer as an input to geoprocessing tools.</div>