University of Arizona


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 roads Map.

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 timeseries data using the timeseries tool. MODIS Data begin in 2002 and VIIRS data begin in 2012

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 EVI, or the Enhanced Vegetation Index. The EVI differs slightly from NDVI in its calculation in order to better detect changes in surface greenness for areas with higher vegetative cover. NDVI and EVI products are viewable on DroughtView from two different sensors. 250-meter 16-day composite Moderate-resolution Imaging Spectroradiometer (MODIS) imagery from 2000 to the present and 500-meter 8-day composite and Visible Infrared Imaging Radiometer Suite (VIIRS) from 2012 to the present.

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 from orange(less green than previous period) to blue(more green than previous period).

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

Difference from Average    Difference from Average products are colored from from orange(less green than overall average) to blue(more green than overvall average).

Climate Data    

Precipitation products fine tuned for DroughtView that can be browsed through time. Drought Monitor (Data since 2019 are displayed) This data layer shows the current 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.

PRISM Precipitation Data (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 has 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 in to a location.

Forest Service Allotments (Vector)     This dataset contains Rangleland 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 land not within an allotment boundary) and Wild Horse/Burro territories (herd management area 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 fcan 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 calcualted 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 here as static maps, viewed and downloaded here using the timeseries tool, or the entire dataset is available from: