VIP15 v004

Vegetation Index and Phenology (VIP) Vegetation Indices 15 Days Global 0.05 Deg CMG


PI: Kamel Didan

Description

The NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Vegetation Index and Phenology (VIP) global datasets were created using Advanced Very High Resolution Radiometer (AVHRR) N07, N09, N11, and N14 datasets (1981 - 1999) and Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra MOD09 surface reflectance data (2000 - 2014). The VIP Vegetation Index (VI) product was developed to provide consistent measurements of the Normalized Difference Vegetation Index (NDVI) and modified Enhanced Vegetation Index (EVI2) spanning more than 30 years of data from multiple sensors. The EVI2 is a backward extension of AVHRR. Vegetation indices such as NDVI and EVI2 are useful for assessing the biophysical properties of the land surface, and are used to characterize vegetation phenology. Phenology tracks the seasonal life cycle of vegetation, and provides information on the biotic response to environmental changes.

The VIP15 VI data product is provided twice monthly at 0.05 degree (5600 meter (m)) spatial resolution in geographic (Lat/Lon) grid format. The data are stored in Hierarchical Data Format-Earth Observing System (HDF-EOS) file format. The VIP15 VI product contains 12 Science Datasets (SDS) which include the calculated VIs (NDVI and EVI2) as well as quality assurance/pixel reliability, the input Visible/Near Infrared (VNIR) surface reflectance data, and viewing geometry. The Blue and Middle Infrared (MIR) surface reflectance data are only available for the MODIS era (2000 - 2014). Gaps in the daily product are filled using long term mean VI records derived from the more than 30 year time series of data, and are indicated as gap-filled in the Pixel Reliability SDS. A low resolution browse image showing NDVI as a color map is also available.

The VIP15 dataset includes two composites per month. The first composite is generated from day 1 to 15, and the second composite includes the remaining days of the month. This dataset consists of 24 files per year.

Characteristics

Collection and Granule

Collection

Characteristic Description
CollectionMEaSUREs VIP
DOI10.5067/MEaSUREs/VIP/VIP15.004
File Size~90 MB
Temporal ResolutionMulti-Day
Temporal Extent1981-01-01 to 2014-12-31
Spatial ExtentGlobal
Coordinate SystemGeographic Latitude and Longitude
DatumWorld Geodetic System (WGS84)
File FormatHDF-EOS
Geographic DimensionsGlobal

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers12
Columns/Rows7200 x 3600
Pixel Size5600 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
CMG 0.05 Deg 15Days NDVI Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days NDVI NDVI 16-bit signed integer -15000 to -12000 N/A -10000 to 10000 0.0001
CMG 0.05 Deg 15Days EVI2 Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days EVI2 EVI2 16-bit signed integer -15000 to -12000 N/A -10000 to 10000 0.0001
CMG 0.05 Deg 15Days VI Quality Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days VI Quality Bit Field 16-bit unsigned integer 65535 N/A 0 to 65534 N/A
CMG 0.05 Deg 15Days Pixel Reliability¹ Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Pixel Reliability Rank 8-bit signed integer -4 to -1 N/A 0 to 11 N/A
CMG 0.05 Deg 15Days Composite Day of the Year Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Composite Day of the Year Day 16-bit signed integer -1 N/A 1 to 366 N/A
CMG 0.05 Deg 15Days RED reflectance Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Red Reflectance N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
CMG 0.05 Deg 15Days NIR reflectance Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Near Infrared Reflectance N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
CMG 0.05 Deg 15Days BLUE reflectance² Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Blue Reflectance N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
CMG 0.05 Deg 15Days MIR reflectance² Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Middle Infrared Reflectance N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
CMG 0.05 Deg 15Days Solar Zenith Angle Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Solar Zenith Angle Degree 16-bit signed integer 0 N/A 1 to 18000 0.01
CMG 0.05 Deg 15Days View Zenith Angle Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days View Zenith Angle Degree 16-bit signed integer 0 N/A 1 to 18000 0.01
CMG 0.05 Deg 15Days Relative Azimuth Angle³ Climate Modeling Grid (CMG) 0.05 Degree resolution 15 Days Relative Azimuth Angle Degree 16-bit signed integer 0 N/A -18000 to 18000 0.01

¹Fill/No Data Value and Valid Range are listed in the Pixel Reliability table.

²BLUE and MIR SDS are only available for MODIS (2000-2014). The Middle Infrared reflectance data used for AVHRR was generated using a MODIS based model that correlates the Red and NIR with the MIR band. The model is then applied to AVHRR Red/NIR to generate false MIR reflectance data useful for image generation.

³The Relative Azimuth Angle is passed along from the input data.

NDVI and EVI2 Fill Values

Value Description
-12000 No Data - High Latitude
-13000 No Data
-14000 Antarctica
-15000 Water

Pixel Reliability Legend

Value Description
0 Excellent
1 Good
2 Acceptable
3 Marginal
4 Pass
5 Questionable
6 Poor
7 Cloud Shadow
8 Snow
9 Cloud
10 Estimated
11 Long Term Average
-1 No Data
-2 No Data - High Latitude
-3 Antarctica
-4 Water

Product Quality

See the Algorithm Theoretical Basis Document (ATBD) and User Guide Section 4.5 for Quality Assurance information .

Known Issues

The Relative Azimuth Angle (RAA) for the input MODIS data is computed based on absolute values of the finer resolution pixels resulting in positive values and has minor usefulness.

The RAA for the input AVHRR data contain values in the -360° to 360° range. The routine to restrict the values in the -180° to 180° range was accidentally missed and can be corrected using the following routine from the Long Term Data Record Data Format Descriptions Document:

SinRelativeAz=sin(RAA) CosRelativeAz=cos(RAA) Correct-RAA = atan2(SinRelativeAz,CosRelativeAz)

Documentation

Using the Data

Tools

Citation

DOI: 10.5067/MEaSUREs/VIP/VIP15.004

About the Image

Global view of the 15 Day NDVI, August 16, 2014.