Please note that the machine on which these AVHRR data are processed has reached its life expectancy and will no longer be available as of 02 June 2008 until further notice.
The AVHRR Polar Pathfinder Twice-Daily 1.25 km EASE-Grid Composites are a collection of products for both poles, consisting of twice-daily gridded and calibrated satellite channel data and derived ... parameters. Data include five Advanced Very High Resolution Radiometer (AVHRR) channels, clear sky surface broadband albedo and skin temperature, solar zenith angle, satellite elevation angle, sun-satellite relative azimuth angle, surface type mask, cloud mask, orbit mask, time of acquisition, and ice motion vectors. Data are composited onto two grids per day based on common local solar times and scan angle. Reduced-resolution data (25 km) derived from the 1.25 km data are available to assist users in selecting these data. AVHRR local area coverage (LAC) and High Resolution Picture Transmission (HRPT) level 1b data are used to generate the Polar Pathfinder products at grid spacings of 1.25 km. AVHRR Polar Pathfinder data extend poleward from 48.4 degrees north and 53.2 degrees south latitudes, from August 1993 through December 1998 for the Northern Hemisphere, and from April 1992 through January 1996 for the Southern Hemisphere. Data are in 1-byte and 2-byte integer grid format. Ice motion vectors are in ASCII text format. Data are available on 8-mm tape or by ftp. Distribution formats available: North: 104 MB (2-byte), 52 MB (1-byte), 8 MB (ice motion) South: 82 MB (2-byte), 41 MB (1-byte), 6.3 MB (ice motion).
Channel data are accurate to within approximately +/- 0.2 percent based on sensor noise level of 0.4 data number (DN). Temperatures are accurate to within approximately 2 degrees Kelvin. Relative albedos in adjacent grid cells are accurate to within approximately 5 percent. However, absolute albedo values are approximate. Accuracies for the products are difficult to determine, given the limited ... nature of existing case studies. Also, conditions vary substantially across the large product domains and over time. Plans are being developed to further define product accuracies for snow-covered areas, sea ice, and ice sheets. Based on studies to date, accuracies in general are approximately +/- 2 degrees Kelvin for AVHRR-derived skin temperatures and +/- 0.05 degrees for surface albedo. Much of this error is likely due to uncertainties in the performance of the cloud detection methods. For clear sky conditions, accuracies for albedo and temperature products are expected to be in the range noted in the Barrow test, with temperatures accurate to +/- 0.5 degrees Celsius. Data and related information will be updated as appropriate. Additional comparisons with in situ measurements of albedo and temperature are planned. See also Maslanik et al. (2000) for other accuracy discussions relative to SHEBA data.
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Province or State:
Cracknell, A.P. 1997. The Advanced Very High Resolution Radiometer. London: Taylor & Francis. Csiszar, I. and G. Gutman. 1999. Mapping global land surface albedo from NOAA AVHRR. Journal of Geophysical Research 104(D6):6215-6228. Emery, W.J., C.W. Fowler, and J.A. Maslanik. 1995. Satellite remote sensing of ice motion, in Oceanographic Applications of Remote Sensing, M. Ikeda and F.W. Dobson ... eds. Boca Raton: CRC Press, pp. 367-379. Goodison, B.E. 1989. Determination of areal snow water equivalent on the Canadian prairies using passive microwave satellite data. IGARSS '89, Proceedings 3:1243-1246. Gustafson, G.B. et al. 1994. Support of Environmental Requirements for Cloud Analysis and Archive (SERCAA), Phillips Laboratory, Hanscom Air Force Base, Scientific Report No. 2, PL-TR-94-2114, 100 pp. Hutchinson, T.A. and T.A. Scambos. 1997. High-resolution polar climate parameters derived from 1-km AVHRR data. Proceedings of the Eighth Symposium on Global Climate Change Studies, American Meteorological Society, Long Beach, CA, pp. 284-289. Key, J. 1999. The cloud and surface parameter retrieval (CASPR) system for polar AVHRR. Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison. Key, J. and A.J. Schweiger. 1998. Tools for atmospheric radiative transfer: Streamer and FluxNet. Computers and Geosciences 24(5): 443-451. Key, J., J. Collins, C. Fowler, and R.S. Stone. 1997. High-latitude surface temperature estimates from thermal satellite data. Remote Sensing of the Environment 61: 302-309. Kidwell, K.D. 1995. NOAA Polar Orbiter Data User's Guide, U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, NESDIS. Maslanik, J.A., J. Key, C. Fowler, T. Nguyen, 2000. AVHRR-derived regional cloud and surface conditions during SHEBA and FIRE-ACE. Journal of Geophysical Research, in press. Maslanik, J., C. Fowler, J. Key, T. Scambos, T. Hutchinson, and W. Emery, 1998. AVHRR -based Polar Pathfinder products for modeling applications. Annals o f Glaciology 25: 388-392. Meier, W.N., J.A. Maslanik, J.R. Key, and C.W. W. Fowler. 1997. Multiparameter AVHRR-derived products for Arctic climate studies, Earth Interactions, Vol. 1. Ninnis, R.M., W.J. Emery, and M.J. Collins. 1986. Automated extraction of pack ice motion from advanced very high resolution radiometer imagery. Journal of Geophysical Research 91(C9): 10,725-10,734. Rao, C.R.N. and J. Chen. 1999. Revised post-launch calibration of channels 1 and 2 of the Advanced Very High Resolution Radiometer on board the NOAA-14 spacecraft. Rao, C.R.N. and J. Chen. 1994. Post-launch calibration of the visible and near-infrared channels of the Advanced Very High Resolution Radiometer on NOAA-7, -9, and -11 Spacecraft. NOAA Technical Report NESDIS 78, 22 pp. Rao, C.R.N. 1993. Nonlinearity corrections for the thermal infrared channels of the AVHRR: Assessment and recommendations. NOAA Technical Report, NESDIS 69, 31 pp. Rosborough, G.W., D.G. Baldwin, and W.J. Emery. 199 4. Precise AVHRR image navigation. IEEE Transactions in Geosciences and Remote Sensing 32(3):644-657. Saunders, R.W. and K.T. Kriebel. 1988. An improved method for detecting clear sky and cloudy radiances from AVHRR data. International Journal of Remote Sensing 9(1): 123-150. Schweiger, A., C. Fowler, J. Key, J. Maslanik, J. Francis, R. Armstrong, M.J. Brodzik, T. Scambos, T. Haran, M. Ortmeyer, S. Khalsa, D. Rothrock, and R. Weaver. 1999. P-Cube: A multisensor data set for polar climate research. Proceedings on the 5th Conference on Polar Meteorology and Oceanography, American Meteorological Society, Dallas, TX, 15-20 Jan., 136-141. Schweiger, A.J. and J.R. Key. 1992. Arctic cloudiness: Comparison of ISCCP-C2 and Nimbus-7 satellite-derived cloud products with a surface-based cloud climatology. Journal of Climate 5(12): 1514-1527. Stowe, L.L., E.P. McClain, R. Carey, P. Pellegrino, and G.G. Gutman. 1991. Global distribution of cloud cover derived from NOAA/AVHRR operatio nal satellite data. Advances in Space Research 11(3): 51-54. Stroeve , J.C., J.E. Box, C. Fowler, T. Haran, and J. Key, 2000. Intercomparison between in situ and AVHRR Polar Pathfinder-derived surface albedo over Greenland. Remote Sensing of the Environment, in press. Stroeve, J.C., 2000. Assessment of Greenland albedo variability from the AVHRR Polar Pathfinder data set. Journal of Geophysical Research, submitted for publication. Suttles, J.T., R.N. Green, P. Minnis, G.L. Smith, W.F. Staylor, B.A. Wielicki, I.J. Walker, D.F. Young, V.R. Taylor, and L.L. Stowe. 1988. Angular radiation models for Earth-Atmosphere system. Volume I-Shortwave radiation, NASA Reference Publication 1184, 144 pp. Walton, C.C., J.T. Sullivan, C.R.N. Rao, and M.P. Weinreb. 1998. Corrections for detector nonlinearities and calibration inconsistencies of the infrared channels of the advanced very high resolution radiometer. Journal of Geophysical Research 103(C2):3323-3337. Yamanouchi, T., K. Suziki, and S. Kawaguchi. 1987. Detection of clouds in Antarctica from i nfrared multispectral data of AVHRR. Journal of Meteorological Society Japan 65(6): 949-961.