Subject: NOAA-18, SBUV/2, Calibration Update, Topic: Change to Operational NOAA-18 SBUV/2 calibration Satellite(s) Involved: NOAA-18 Instrument(s) Involved: SBUV/2 Product(s) Involved/Affected: Total and Profile Ozone distributed via daily and orbital Product Master File (PMF) in Binary and BUFR format Date/Time(UTC) of Initial Implementation: 4 March, 2006, Time ~1500 UTC Contact Person(s) Name/Email/Phone Number for Questions: Donna.McNamara@noaa.gov 301-763-8142 ext. 145 Web site(s) that contain other relevant information (where applicable): http://www.osdpd.noaa.gov/PSB/OZONE/OZONE.html Details/Specifics of Change: This message is to notify users of an update to NOAA-18 calibration. This is the follow-on calibration change initially mentioned in the Mar 15 notification message regarding a calibration table change for NOAA-18. All available calibration changes have now been updated in operations. NASA contract scientists, who provide our calibration updates report "While we have applied our best efforts to creating the updated NOAA-18 calibration, there are still some significant differences between SSAI test processing results at the Equator and concurrent ozone data from NOAA-16 and NOAA-17. The NOAA-18 profile ozone values are significantly lower at layer 5 and above, with differences reaching 15-20% at 1 hPa. NOAA-18 best total ozone values are approximately 3-5 DU lower than NOAA-16 data, and approximately 6-8 DU lower than NOAA-17 data. We are working to understand the origin of the inconsistencies between NOAA-18 calibration data and results from other SBUV/2 instruments, and will notify you if we develop an improved calibration." Layer 5 is 32 MB and above. On a positive note, we have noticed in our testing that this change increases total ozone at the very highest latitude, bringing it more closely in line with NOAA-16 and NOAA-17. -- Donna P. McNamara Physical Scientist NOAA/NESDIS/OSDPD/SSD/PIB 5200 Auth Rd., Rm 510 Camp Springs MD 20746 Phone: (301)763-8142x145 Fax: (301)899-9196