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Katrina: Ultra-High Resolution (Aug. 28, 2005)

QuikSCAT/SeaWinds Ultra-High Resolution Observation of Tropical Cyclones

Resolution enhancement algorithms such as those used for making enhanced resolution sigma-0 images over land, can also be applied to QuikSCAT and SeaWinds over-ocean data due the high sampling density. Further, enhanced resolution backscatter images can be generated from single pass, single azimuth look measurements, enabling wind retrieval at the pixel resolution of the imagery—about 2.5 km posting.

Compared with standard resolution winds, ultra-high resolution winds provide additional storm structure such as inner core size and structure and the presence of multiple eyewalls. The 2.5 km winds are also able to observe storms nearer to the shore than 25 km winds. Because of the additional storm detail, center fixes are more accurately obtained from resolution enhanced winds than standard resolution winds. (See Halterman, R. R., and D.G. Long, "Comparison of Hurricane Eye Determine Using Standard and Ultra-High Resolution QuikSCAT Winds," Proceedings of the International Geoscience and Remote Sensing Symposium, Denver, Colorado, 31 Jul. – 4 Aug. 2006.)

Several image/data products for every (over 6000 in total) QuikSCAT/SeaWinds observation of National Hurricane Center (NHC) or Joint Typhoon Warning Center (JTWC) tracked tropical cyclones from 1999 through 2005 are being distributed through the Scatterometer Climate Record Pathfinder (SCP) anonymous file Site in the data/qscat/HRStorms directory. The file directory structure and the available products are described below. Real-time ultra high resolution wind and related products based on our algorithms are available from NOAA courtesy of Paul Chang.

The QuikSCAT/Storm co-location text file is available here. For each QuikSCAT/Storm co-location it includes information about the time/date of the observation, the QuikSCAT/SeaWinds rev number, the interpolated NHC/JTWC best-track storm location, and other information from the best-track files. Note: This file includes both QuikSCAT and SeaWinds storm co-locations. All SeaWinds co-locations occur during the 2003 year and are differentiated from QuikSCAT co-locations by their much lower rev number (e.g. 1700 vs. 19900).

Please note that ultra-high resolution winds are an experimental product produced from NRT data and have significant limitations, particularly near coasts. Performance varies across the swath. Ambiguity removal performance is somewhat worse than conventional 25 km winds. Product validation continues and is encouraging but does point to the fact that the high resolution estimates are noisy and can be biased, particularly at low wind speeds. Note that ultra high
Katrina: Standard Resolution (Aug. 28, 2005)
resolution winds currently have no rain flag, but show clear evidence of rain contamination (e.g. individual convective systems can be distinguished in many places.).

Data is available via file, though a web page inteface is available (it loads slowly due to its large size). The file site sub-directory structure is: ftp.scp.byu.edu/data/qscat/HRStorms/<BASIN>/<SEASON>/<STORM>/<FILE>

  • <BASIN> = Two letter NHC/JTWC abreviation for storm basin: Atlantic (AL), Eastern Pacific (EP), Central Pacific (CP), Indian Ocean (IO), Southern Hemisphere (SH), and Western Pacific (WP).

  • <SEASON> = Four digit NHC/JTWC storm season (year).

  • <STORM> = NHC/JTWC Storm name (all-caps). Note: for IO, SH, and WP storms, the storm name is of the form <BASIN><NUMBER>_<SEASON> (e.g. WP01_2000) where <NUMBER> is the JTWC storm number (two-digit) within the season.

  • <FILE> = Filename of the form QS_S1Bnnnnn.YYYYDDDHHMM.*_NAME_mmddyy_*, where nnnnn is the 5 digit QuikSCAT rev number, NAME is the storm name, and mm is the month, dd is the day of the month, and yy, is the two digit year of the day of collection. YYYY is the 4 digit year, DDD is the 3 digit day of the year, HH is the hour, MM is minute the data were post-processed. For SeaWinds-derived files, the initial QS in the filename is changed to SW.

The images/products available through the SCP anonymous file Site include:

  • *_map_all.gif = Standard resolution wind ambiguity images for all ambiguities.

  • *_map_sel.gif = Standard resolution wind ambiguity images for the L2B selected ambiguity.

  • *_WRave3_LowRes_map.gif = Standard resolution L2B wind field images.

  • *_ha.gif = Enhanced resolution Sigma-0 images for H-Pol Aft-looking.

  • *_hf.gif = Enhanced resolution Sigma-0 images for H-Pol Fore-looking.

  • *_va.gif = Enhanced resolution Sigma-0 images for V-Pol Aft-looking.

  • *_vf.gif = Enhanced resolution Sigma-0 images for V-Pol Fore-looking.

  • *_me.gif = Enhanced resolution Sigma-0 images of the mean of the four Sigma-0s.

  • *_WRave3_map.gif = Enhanced resolution wind field images.

  • *_WRave2.gz = gzipped Enhanced resolution wind field binary data file (no ambiguity selection smoothing).

  • *_WRave3.gz = gzipped Enhanced resolution wind field binary data file (with ambiguity selection smothing).

All images are plotted on a lat/lon grid. Single pass ocean backscatter images have 2.5 km/pixel image resolution. The *.gif image sizes are on the order of 1500x1500 pixels.

Software (C, Fortran, Matlab, IDL) for reading BINARY high resolution wind files (*_WRave3) files are available from the Scatterometer Climate Record Pathfinder (SCP) anonymous file Site in the software/HRsoftware/HRwind subdirectory. Contact David Long for additional high resolution wind files.