Vegetation Indices

The MODerate-resolution Imaging Spectroradiometer (MODIS) platform on board NASA's Terra and Aqua satellites contain sensors for deriving vegetation indices. Each satellite operates on 16-day interval to provide consistent spatial and temporal comparisons of vegetation canopy greenness; a composite property of leaf area, chlorophyll and canopy structure. Two vegetation indices are derived from atmospherically-corrected reflectance in the red, near-infrared, and blue wavebands; the normalized difference vegetation index (NDVI), and the enhanced vegetation index (EVI).  EVI minimizes canopy-soil variations and improves sensitivity over dense vegetation conditions. MODIS data is produced by the National Aeronautics and Space Administration (NASA).

Evapotranspiration (ET) is the sum of evaporation and plant transpiration expressed as inches of water. Potential evapotranspiration (PET) is the evaporation that would occur if sufficient water were available. The MODerate-resolution Imaging Spectroradiometer (MODIS) platform on board NASA's Terra and Aqua satellites contain sensors for producing MODIS ET and PET data. The MODIS ET and PET methodology and algorithms were developed at the University of Montana by the MODIS Global Evapotranspiration Project. Data are distributed by the University of Montana's Numerical Terradynamic Simulation Group (NTSG).

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Vegetation Indices

Online map of mean annual Normalized Difference Vegetation Index

Online map of mean annual Normalized Difference Vegetation Index (Web application)

Image of mean annual Normalized Difference Vegetation Index map (JPEG)

Print version of mean annual Normalized Difference Vegetation Index map (PDF)

Mean annual Normalized Difference Vegetation Index (NDVI) for the years 2000-2013 from MODIS. An NDVI value of zero means no green vegetation and close to 0.8 - 0.9 indicates the highest possible density of green leaves. MODIS data is produced by the National Aeronautics and Space Administration (NASA).

For the Terra MODIS satellite platform each 1-kilometer square area of monthly NDVI values was averaged for each year in the period 2000 to 2013.  The 14-year annual mean was calculated from the annual means for all years in the period 2000-2013.

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Online map of mean monthly Normalized Difference Vegetation Index

Online map of mean monthly Normalized Difference Vegetation Index (Web application)

Image of mean monthly Normalized Difference Vegetation Index map (JPEG)

Print version of mean monthly Normalized Difference Vegetation Index map (PDF)

Mean monthly Normalized Difference Vegetation Index (NDVI) for the years 2000-2013 from MODIS. An NDVI value of zero means no green vegetation and close to 0.8 - 0.9 indicates the highest possible density of green leaves. MODIS data is produced by the National Aeronautics and Space Administration (NASA).

For the Terra MODIS satellite platform each 1-kilometer square area of monthly NDVI values was averaged for each month in the period 2000 to 2013 to create a 14-year monthly mean.

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Online map of mean annual Enhanced Vegetation Index

Online map of mean annual Enhanced Vegetation Index (Web application)

Image of mean annual Enhanced Vegetation Index map (JPEG)

Print version of mean annual Enhanced Vegetation Index map (PDF)

Mean annual Enhanced Vegetation Index (EVI) for the years 2000-2013 from MODIS. EVI responds to canopy structural variations and canopy type whereas the Normalized Difference Vegetation Index (NDVI) responds to the presence of chlorophyll. MODIS data is produced by the National Aeronautics and Space Administration (NASA).

For the Terra MODIS satellite platform each 1-kilometer square area of monthly EVI values was averaged for each year in the period 2000 to 2013.  The 14-year annual mean was calculated from the annual means for all years in the period 2000-2013.

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Online map of mean monthly Enhanced Vegetation Index

Online map of mean monthly Enhanced Vegetation Index (Web application)

Image of mean monthly Enhanced Vegetation Index map (JPEG)

Print version of mean monthly Enhanced Vegetation Index map (PDF)

Mean monthly Enhanced Vegetation Index (EVI) for the years 2000-2013 from MODIS not filtered for snowpack. EVI is considered a proxy measure of vegetation "greenness". A higher EVI means healthier, more active, and less stressed vegetation. MODIS data is produced by the National Oceanic and Atmospheric Administration (NASA).

For the Terra MODIS satellite platform each 1-kilometer square area of monthly EVI values was averaged for each month in the period 2000 to 2013 to create a 14-year monthly mean.

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Evapotranspiration

Online map of mean annual evapotranspiration

Online map of mean annual evapotranspiration (Web application)

Image of mean annual evapotranspiration map (JPEG)

Print version of mean annual evapotranspiration map (PDF)

Mean annual evapotranspiration (ET) for the years 2000-2012 from MODIS. ET is the sum of evaporation and plant transpiration as inches of water. MODIS ET data is produced and distributed by the MODIS Global Evapotranspiration Project (MOD16) at the University of Montana.

Monthly evapotranspiration was summed for each 1-kilometer square area for each year in the period 2000-2013. The 14-year annual mean was calculated from the annual totals for all years in the period 2000-2013.

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Online map of mean monthly evapotranspiration

Online map of mean monthly evapotranspiration (Web application)

Image version of mean monthly evapotranspiration map (JPEG)

Print version of mean monthly evapotranspiration map (PDF)

Mean monthly evapotranspiration (ET) for the years 2000-2013 from MODIS. ET is the sum of evaporation and plant transpiration as inches of water. MODIS ET data is produced and distributed by the MODIS Global Evapotranspiration Project (MOD16) at the University of Montana.

Monthly evapotranspiration was averaged for each 1-kilometer square area for each month in the period 2000-2013 to obtain an overall monthly mean for the 14-year period.

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Online map of mean annual potenatial evapotranspiration

Online map of mean annual potential evapotranspiration (Web application)

Image of mean annual potential evapotranspiration map (JPEG)

Print version of mean annual potential evapotranspiration map (PDF)

Mean annual potential evapotranspiration (PET) for the years 2000-2013 from MODIS. PET is the evaporation that would occur if sufficient water were available. PET is provided and distributed by the MODIS Global Evapotranspiration Project (MOD16) at the University of Montana.

Monthly potential evapotranspiration was summed for each 1-kilometer square area for each year in the period 2000-2013. The 14-year annual mean was calculated from the annual totals for all years in the period 2000-2013.

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Online map of mean monthly potential evapotranspiration

Online map of mean monthly potential evapotranspiration (Web application)

Image of mean monthly potential evapotranspiration map (JPEG)

Print version of mean monthly potential evapotranspiration map (PDF)

Mean monthly potential evapotranspiration (PET) for the years 2000-2013 from MODIS. PET is the evaporation that would occur if sufficient water were available. PET is produced and provided by the MODIS Global Evapotranspiration Project (MOD16) at the University of Montana.

Monthly potential evapotranspiration was averaged for each 1-kilometer square area for each month in the period 2000-2013 to obtain an overall monthly mean for the 14-year period.

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Measures of Drought

Online map of annual Drought Severity Index

Online map of mean annual Drought Severity Index (Web application - tabbed)

Online map of mean annual Drought Severity Index (Web application - time slider)

Image of annual Drought Severity Index map (JPEG)

Print version of annual Drought Severity Index map (PDF)

Annual Drought Severity Index (DSI) for the years 2000-2011. The DSI is a single index ranging from negative (drier than normal) to positive (wetter than normal). The statewide mean allows for year to year comparisons. DSI was developed at the University of Montana as part of the MODIS global terrestrial evapotranspiration project.

There are several methods for drought assessment and monitoring. Drought indices are designed to integrate data from numerous sources and represent that result as an index. In 2013 the Numerical Terradynamic Simulation Group (NTSG) research laboratory at The University of Montana published a Drought Severity Index (DSI) that leverages the MODerate-resolution Imaging Spectroradiometer (MODIS) satellite platform. The DSI provides a measure of wetness relative to normal and displays the magnitude and spatial extent of drought.  This method provides a higher-resolution continuous surface than typically found, and allows for a more localized assessment of drought. There is significant future work that can adapt this product for future application in Montana. DSI is displayed for each year the product is available.

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