Understand the Data behind DroughtView

Base Maps

Basemaps appear under all other layers. They will appear if you move the marker on the Opacity Bar all the way to the left. Click the bubble next to the basemap you would like to display in the panel.

Imagery     High spatial resolution satellite image data for the world.

Topographic     Digitized version of USGS topo quads (note you need to be zoomed in to see the quads)

Streets     A map representing major roads.

Terrain     Map showing physiographic features including contour lines when zoomed in

MODIS NDVI (Near Real Time 8 Day)     Near Real-Time NDVI Map showing a rolling average of NDVI values for the past 8 days using NASA's colormap (note the colormap differences with the MODIS NDVI maps below)

MODIS EVI (Near Real Time 8 Day)     Near Real-Time EVI Map showing a rolling average of NDVI values for the past 8 days using NASA's colormap (note the colormap differences with the MODIS EVI maps below)

MODIS Greenness and VIIRS Greenness

Vegetation data fine-tuned for DroughtView that can be browsed through time. Note that these data can be displayed as time-enabled raster overlays or as time series data using the time series tool. MODIS Data are available from 2000 to the present and VIIRS data are available from 2012 to present. All MODIS products on DroughtView are computed using Terra MODIS Version 6.1 data generated every 16 days at a spatial resolution of 250 meters. All VIIRS products are computed using Suomi NPP VIIRS Version 1 data generated every 8 days at a spatial resolution of 500 meters

Normalized Difference Vegetation Index (NDVI) data are a measure of surface greenness computed using red and near-infrared surface reflectance measurements. Remotely sensed measures of surface greenness are linked to several characteristics of vegetation such as growth, density, and type. For example, NDVI values of broad forested areas typically are higher than those of grasslands. Another satellite-derived measure of surface greenness we use for DroughtView is the Enhanced Vegetation Index or EVI. The EVI differs slightly from NDVI in its calculation to better detect changes in surface greenness for areas with higher vegetative cover.

Actual Actual products are colored from tan (less vegetation) to dark green (dense vegetation) and represent the raw EVI or NDVI data.

Difference from Period Difference from Period products are colored from orange(less green than the previous period) to blue(more green than the previous period).

Difference from Year Difference from Year products are colored from orange(less green than the previous year) to blue(more green than the previous year).

Difference from Ten Year Average Difference from Ten Year Average products are colored from orange(less green than the ten year average) to blue(more green than the ten year average). These products show the difference in greeness for the period selected from an average computed for 2013 - 2022 for that same period

Difference from Five Year Average Difference from Five Year Average products are colored from orange(less green than the five year average) to blue(more green than five year average). These products show the difference in greeness for the period selected from an average computed for 2018 - 2022 for that same period.

Climate Data

Climate-related products fine-tuned for DroughtView. With the exception of the drought outlooks, they can be browsed through time.

Climate Prediction Center Drought Outlooks This data layer shows the current Climate Prediction Center (CPC) drought outlook maps (which can also be viewed online at https://www.cpc.ncep.noaa.gov/products/Drought/), which are based on on the US Drought monitor, but also guided by short- and long-range statistical and dynamical forecasts. They are valid for the current time only.

Drought Monitor (Data since 2019 are displayed) This data layer shows the U.S. Drought Monitor, a weekly mapping of drought conditions based on climatic, hydrologic, and soil moisture information along with related impacts. The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the U.S. Department of Agriculture, and the National Oceanic and Atmospheric Administration.

Snow Water Equivalent (Data since 2002 are displayed) Shown are SWE data from the University of Arizona SWANN snowpack dataset. These data have 30 arcsecond (~1 km) resolution. In addition, there are layers showing the departure from and percentage of normal (based on 1982-2016 averages).

Water Year Precipitation (Data since 2002 are displayed) Shown are precipitation data from Oregon State University's PRISM climate group displayed as water year cumulative daily sums for each date. These data have 2.5 arcminute (~4 km) resolution and are widely considered to be precipitation dataset available for the western United States. In addition, there are layers showing the departure from and percentage of normal (based on 1982-2016 averages).

Places and Boundaries

These are overlying vector layers that provide spatial context to the raster data (below).

USA Federal Lands     Provided by ESRI ArcGIS Online, this data layer shows federal and tribal land areas of the United States symbolized by managing agency. The display of these management areas is scale dependent, with greater detail appearing as one zooms into a location.

Forest Service Allotments (Vector)     This dataset contains Rangeland Management Units for each national forest across the US. Each National Forest grazing allotment, or Rangeland Management Unit (RMU), is a designated area of land available for livestock grazing, managed by the Forest Service, and may be subdivided into pastures necessary for grazing management. This layer includes Allotments, Exclosures (domestic livestock excluded within the allotment boundary), General Resource Areas (National Forest Service land not within an allotment boundary) and Wild Horse/Burro territories (herd management areas with identified appropriate management Levels for wild horse/burro populations).

BLM Grazing Allotments     Made available by the BLM, this data layer includes BLM Grazing Allotments. In addition to public lands under the jurisdiction of the Bureau of Land Management, allotments may include private lands, State lands, and lands under the jurisdiction of other federal agencies

USGS HUCs     Made available by the USGS through The National Map, this layer shows the Watershed Boundary Dataset that defines perimeters of drainage areas formed by local and regional terrain. The display of watershed boundaries is scale dependent, with greater detail appearing as one zooms in to a location. In this context, the Watershed Boundary Dataset has six levels of detail that include region, subregion, basin, subbasin, watershed, and subwatershed. Depending on the zoom level, individual watersheds are labeled by a 2-, 4-, 6-, 8-, 10-, or 12-digit HUC, or hydrologic unit code, respectively.

Roads and Borders     This is the roads and borders layer from Google.

Fire Data

These are fire layers from the Monitoring Trends in Burn Severity (MTBS). A variety of fire layers can be displayed, including current fires, MODIS fire detections, fire perimeters for both the current year as well as those from the past, as well as burn severity maps.

Rangeland Productivity Maps

These are raster overlays showing the annualized rangeland production, as calculated by the US Forest Service. This raster dataset shows estimates of annual production (calculated using NDVI from the Landsat Thematic Mapper Suite from 1984 to 2018 at 250 m resolution) of rangeland vegetation and should be useful for understanding trends and variability in forage resources. Both the annual production values (in lbs/acre) and z-scores (showing relative annual productivity). These can be visualized on DroughtView as static maps, viewed and downloaded from DroughtView using the time series tool, or the entire dataset is available for download from the US Forest Service Rangelands Website.