Drought is defined as an extended period of deficient rainfall relative to the average for a region. Satellite imagery can be used to help identify areas of drought over time. Near real-time monitoring of drought conditions can be useful for monitoring crops and forecasting yield. There are several global/regional scale systems in place that report on drought, food shortages and forecasting crop yields including the USGS Famine Early Warning Systems Network (FEWS NET) and Group on Earth Observations Global Agricultural Monitoring (GEO GLAM) crop monitor.

Users can visualize imagery related to drought in Worldview or download data through NASA's Land, Atmosphere Near real-time Capability for Earth observation (LANCE) using the links below.

Corrected Reflectance Imagery

MODIS and VIIRS Corrected Reflectance imagery are available only as near real-time imagery. The imagery can be visualized in Worldview and Global Imagery Browse Services (GIBS). More:

Information on MODIS Corrected Reflectance Imagery layers including

• Corrected Reflectance True Color (Bands 1-4-3)
• Corrected Reflectance (Bands 3-6-7)
• Corrected Reflectance (Bands 7-2-1)

Information on VIIRS Corrected Reflectance Imagery layers including

• Corrected Reflectance True Color (Bands I1-M4-M3)
• Corrected Reflectance (Bands M3-I3-M11)
• Corrected Reflectance (Bands M11-I2-I1)

Browse Corrected Reflectance imagery in Worldview

For more on the difference between Corrected Reflectance and Surface Reflectance Imagery

Land Surface Reflectance

In comparison with the MODIS Corrected Reflectance product, the MODIS Land Atmospherically Corrected Surface Reflectance product (MOD09) is a more complete atmospheric correction algorithm that includes aerosol correction, and is designed to derive land surface properties.

Product: Instrument, Platform and Download Link	Description	Browse imagery in Worldview
MODIS (Aqua) MYD09 MODIS (Terra) MOD09	doi:10.5067/MODIS/MYD09.NRT.061 (Aqua) and doi:10.5067/MODIS/MOD09.NRT.061 (Terra) More information on MODIS Land Surface Reflectance Products including: MODIS (Aqua/Terra) Land Surface Reflectance True Color (Bands 1-4-3) MODIS (Aqua/Terra) Land Surface Reflectance True Color (Bands 7-2-1) MODIS (Aqua/Terra) Land Surface Reflectance True Color (Bands 1-2-1)	True Color Bands 1-2-1 Bands 7-2-1
VIIRS (Suomi NPP) VNP09_NRT	VIIRS Land Surface Reflectance  The VIIRS Surface Reflectance provides continuity with the EOS-MODIS Land Surface Reflectance product.The Suomi NPP/VIIRS surface reflectance products are estimates of surface reflectance in each of the VIIRS reflective bands I1-I3, M1-M5, M7, M8, M10, and M11. Surface reflectance for each moderate-resolution (750m) or imagery-resolution (375m) pixel is retrieved separately for the Level-2 products and is obtained by adjusting top-of-atmosphere reflectance to compensate for atmospheric effects. Corrections are made for the effects of molecular gases, including ozone and water vapor, and for the effects of atmospheric aerosols. The inputs to the surface reflectance algorithm include top-of-atmosphere reflectance for the VIIRS visible bands (VNP02MOD, VNP02IMG), the VIIRS cloud mask and aerosol product (NPP-CMIP_L2), aerosol optical thickness (NPP_VAOTIP_L2, NPP_VAMIP_L2), and atmospheric data obtained from a reanalysis (surface pressure, atmospheric precipitable water, and ozone concentration). All surface reflectance products are produced for daytime conditions only.	Coming soon

Land Surface Temperature

Land Surface Temperature layer shows the temperature of the land surface in Kelvin (K). This measurement differs from air temperature measurements as it provides the temperature of whatever is on the surface of the earth for example, bare sand in the desert, ice and snow covered area, a leaf covered tree canopy and even the temperature of man-made buildings and roads. Land Surface Temperature is useful for monitoring changes in weather and climate patterns and used in agriculture to allow farmers to evaluate water requirements for wheat, or determine frost damage in orange groves.

Product: Instrument, Platform and Download Link	Description	Browse imagery in Worldview
MODIS (Terra) MOD11_L2 MODIS (Aqua) MYD11_L2	MODIS Land Surface Temperature and Emissivity The MODIS Land Surface Temperature and Emissivity (LST&E) product is available from both Terra and Aqua satellites. The sensor and imagery resolution is 1 km, and the temporal resolution is daily. doi:10.5067/MODIS/MOD11_L2.NRT.061 and doi:10.5067/MODIS/MYD11_L2.NRT.061	Land Surface Temp (Day/Night)
VIIRS (Suomi NPP) VNP21_NRT	VIIRS Land Surface Temperature and Emissivity VIIRS/Suomi NPP Land Surface Temperature and Emissivity 6-Min L2 Swath 750m NRT products doi:10.5067/VIIRS/VNP21_NRT.001	Coming soon

Snow Cover

The MODIS snow cover layer shows the presence of snow cover over land and water bodies as an index related to the presence of snow. It is based on a Normalized Difference Snow Cover Index (NDSI) that is derived from the cloud free snow reflectance sensed by the MODIS instrument, and hence this layer shows presence of snow during day time and under cloud clear condition only. NDSI snow cover though could be retrieved in the valid range of (0, 1.0) at every pixel, additional tests like surface temperature screening linked with the surface height is used for accurate detection. Snow is precipitation that forms from water vapor in the atmosphere where temperatures are below 0° Celsius. If the ground temperature is also below freezing, snow will accumulate on the ground as bright, white layer of snowpack. Snow cover reflects sunlight back into the atmosphere, helping to cool the Earth’s surface. Snowmelt is used for drinking water, water for crop irrigation, and can moisturize soil to reduce the risk of wildfire in many areas in the world. When snow melts in the spring, too much snow can cause springtime flooding.

Product and Download Link	Description	Browse imagery in Worldview
MODIS (Terra) MOD10_L2 MODIS (Aqua) MYD10_L2	MODIS Snow Cover (Normalized Difference Snow Index) The MODIS Snow Cover layer is available from both the Terra and Aqua satellites. The sensor and imagery resolution is 500 m and the temporal resolution is daily. doi:10.5067/MODIS/MOD10_L2.NRT.061 and doi:10.5067/MODIS/MYD10_L2.NRT.061	Snow Cover

Snow Water Equivalent

The AMSR2 Snow Water Equivalent layer indicates the amount of water that is contained in snowpack in the Northern and Southern Hemispheres measured in millimeters (mm). Another way to think of it is if all the snow were melted instantaneously, it would be the depth of that water. The snow water equivalent layer is useful for assessing the amount of water that is present in the snowpack and can be used to assess surface runoff when the snow melts and to assess water availability for regions in lower elevations. The Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument is a conically scanning passive microwave radiometer sensing microwave radiation at 12 channels and 6 frequencies ranging from 6.9 to 89 GHz aboard the Global Change Observation Mission – Water 1 (GCOM-W1) satellite.

Product and Download Link	Description	Browse imagery in Worldview
AMSR2 (GCOM W-1) A2_DySno_NRT	AMSR2 Snow Water Equivalent This layer is part of the GCOM-W1 AMSR2 Level-3 Snow Water Equivalent (SWE) data set, which contains snow water equivalent (SWE) data and quality assurance flags mapped to the Northern and Southern Hemisphere 25 km Equal-Area Scalable Earth Grids (EASE-Grids). As NRT Tb Level -1R data are received from JAXA throughout the day, partial daily products are generated and identified with a product maturity code of "P" in the filename. Once all Level-1R inputs are available, the complete daily product contains product maturity code "R" (near Real time) in the filename. Incremental processing makes data available to the user as it is received, rather than at the end of the day. The imagery resolution is 2 km and sensor resolution is 5 km. The temporal resolution is daily (partial NRT files updated throughout the day to a final product).	AMSR2 Snow Water Equivalent

Vegetation Indices

Vegetation indices are used for monitoring of vegetation conditions and can be used to identify areas undergoing land cover changes. These data may be used as input for modeling global biogeochemical and hydrologic processes and global and regional climate. These data also may be used for characterizing land surface biophysical properties and processes including primary production and land cover conversion. Vegetation indices also provide information on the health of vegetation and can assist farmers and resource managers monitor the health and development of their crops and fields over the growing season.

LANCE produces a daily 8-day rolling vegetation indices product, which includes both Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), and an 8-day rolling surface reflectance product (MOD09Q1N).

Product: Instrument, Platform and Download Link	Description	Browse imagery in Worldview
MODIS (Terra) MOD13Q4N (250m) MOD13A4N (500m)	MODIS rolling 8-day NDVI The MODIS NDVI layer is a measure of the greenness and health of vegetation. The index is calculated based on how much red and near-infrared light is reflected by plant leaves. The index values range from -0.2 to 1 where higher values (0.3 to 1) indicate areas covered by green, leafy vegetation and lower values (0 to 0.3) indicate areas where there is little or no vegetation. Areas with a lot of green leaf growth, indicates the presence of chlorophyll which reflects more infrared light and less visible light, are depicted in dark green colors, areas with some green leaf growth are in light greens, and areas with little to no vegetation growth are depicted in tan colors. MODIS rolling 8-day EVI The MODIS EVI is also used as a measure of the greenness and health of vegetation. It is calculated in a similar fashion as NDVI but it corrects for distortions caused by ground cover beneath the canopy vegetation and distortions in reflected light caused by particles in the air by using the blue band to remove residual atmosphere contamination caused by smoke and sub-pixel thin cirrus clouds. The EVI is more effective in areas with large amounts of chlorophyll such as rainforests. The index values range from -0.2 to 1 where higher values (0.3 to 1) indicate areas covered by green, leafy vegetation and lower values (0 to 0.3) indicate areas where there is little or no vegetation.	NDVI and EVI (rolling 8-day)