Overview

The use of satellite imagery provides a unique vantage point for observing seasonal dynamics of the landscape. The U.S. Geological Survey's EROS Data Center has developed a data set of seasonal metrics derived from multitemporal Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) observations for the conterminous United States. NDVI values are first composited over a 2-week time period to reduce cloud contamination, atmospheric perturbations, and variable illumination and viewing geometry. The data are then 'smoothed' to facilitate time-series analyses (Swets and others, 1999) and derivation of the seasonal metrics (Reed et. al., 1994). A set of 12 seasonal metrics (e.g., total integrated NDVI, start of season, end of season) are then derived from the smoothed NDVI values. The data are free and currently include the following (for years 1989 to current):

Bi-weekly smoothed NDVI
Seasonal Metrics:
	Total Integrated NDVI
	Start of Season Date
	End of Season Date
	Start of Season NDVI

More information about the data set and methods used in developing the metrics can be found in the articles in the References section below and the 'readme' files included in the Data section.

References

Reed, B.C., and E. Bartels, 1999. Phenological Characterization (abs.) in Proceedings of Pecora 14 Conference, Denver, Colorado, December 1999.

Schwartz, M.D. and B.C. Reed, 1999. Surface phenology and satellite sensor-derived onset of greenness: an initial comparison. International Journal of Remote Sensing, Vol. 20, No. 17, pp. 3451-3457.

Swets, D.L., B.C. Reed, J.R. Rowland, S.E. Marko, 1999. A weighted least-squares approach to temporal smoothing of NDVI. In 1999 ASPRS Annual Conference, From Image to Information, Portland, Oregon, May 17-21, 1999, Proceedings: Bethesda, Maryland, American Society for Photogrammetry and Remote Sensing, CD-ROM, 1 disc.

Reed, B.C., 1998. Derivation of phenological metrics. Proceedings of the Northern Great Plains Regional Workshop on Climate Change and Climate Variability. pp. 47-56.

Yang, L., B.K. Wylie, L.L. Tieszen, B.C. Reed, 1998. An analysis of relationships among climate forcing and time-integrated NDVI of grasslands over the U.S. Northern and Central Great Plains. Remote Sensing of Environment, 65: 25-37.

Reed, B.C., 1997. Applications of the U.S. Geological Survey's global land cover product. Acta Astronautica, Vol. 41, Nos. 4-10, pp. 671-680.

Reed, B.C. and K. Sayler, 1997. A method for deriving phenological metrics from satellite data, Colorado 1991-1995. Impact of Climate Change and Land Use in the Southwestern United States, an electronic workshop. ( http://geochange.er.usgs.gov/sw/impacts/biology/Phenological-CO/)

Reed, B.C. and Yang, L. 1997. Seasonal Vegetation Characteristics of the United States. Geocarto International 12(2): 65-71.

Tieszen, L.L, B.C. Reed, N.B. Bliss, B.K. Wylie, and D.D DeJong 1997. NDVI Characteristics, potential C3 and C4 grass production and d13C values in grassland land cover classes of the Great Plains. Ecological Applications. 7(1)m 1997, pp. 59-78.

Outland, J.C., L.L. Tieszen, D.D. DeJong, and B.C. Reed, 1997. A functional analysis of ecosystem performance in selected Kuchler types of the Northern Great Plains - NDVI and metrics of land cover classes [abs], in Pecora Thirteen, Human interactions with the Environment - Perspectives from Space, Sioux Falls, South Dakota, August 20-22, 1996, Proceedings: Bethesda, Maryland, American Society of Photogrammetry and Remote Sensing.

Reed, B.C., T.R. Loveland, and L.L. Tieszen, 1996. An approach for using AVHRR data to monitor U.S. Great Plains grasslands: Geocarto International, v. 11, no. 3, p. 13-22.

Reed, B.C., J.F. Brown, D. VanderZee, T.L. Loveland, J.W. Merchant, D.O. Ohlen, 1994. "Measuring phenological variability from satellite imagery," Journal of Vegetation Science 5: 703-714.

Contact

Project Coordinator:	Bradley Reed
Phone:	605-594-6012
Email:	reed@usgs.gov