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.

Mapbox Outdoors     A general-purpose map with curated tilesets and specialized styling tailored to hiking, biking, and the most adventurous use cases.

Google Satellite Map     High spatial resolution image data compiled and served by Google.

World Shaded Relief     This layer portrays surface elevation as shaded relief.

Places and Boundaries    

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

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).

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.

Arizona Grazing Allotments     Made available by the Arizona Game & Fish Department, this data layer includes Arizona State Land Department, Bureau of Land Management, and U.S. Forest Service allotments for the state of Arizona.

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.

Raster Overlays    

Raster Overlays contain a number of vegetation and precipitation products fine tuned for DroughtView that can be browsed through time. They can be displayed as raster overlays or as timeseries data using the timeseries tool.

Vegetation Index Products (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).

Drought Monitor (Data since 2002 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).

Fire Data    

Monitoring Trends in Burn Severity (MTBS) is an interagency program whose goal is to consistently map the burn severity and extent of large fires across all lands of the United States from 1984 to present. This includes all fires 1000 acres or greater in the western United States and 500 acres or greater in the eastern Unites States. The extent of coverage includes the continental U.S., Alaska, Hawaii and Puerto Rico. MTBS data are freely available to the public and are generated by leveraging other national programs including the Landsat satellite program, jointly developed and managed by the USGS and NASA. Landsat data are analyzed through a standardized and consistent methodology, generating products at a 30 meter resolution dating back to 1984. One of the greatest strengths of the program is the consistency of the data products which would be impossible without the historic Landsat archive, the largest in the world.