This document summarizes a study of near-nadir microwave brightness temperatures from NOAA satellites over Antarctica: 1) Measurements from NOAA-18, NOAA-19, and METOP-A showed little diurnal variability in Antarctic winter months due to 24-hour nighttime. 2) Differences between ascending and descending measurements were used to determine intersatellite/intersensor calibration biases, showing Antarctica is useful for calibration validation. 3) Long-term monitoring of instrument performance on NOAA-18 and NOAA-19 showed microwave humidity sounder and AMUS-A measurements remained stable over multiple time periods from launch.

1. A STUDY OF THE NOAA NEAR-NADIR MICROWAVE HUMIDITY SOUNDER BRIGHTNESS TEMPERATURES OVER ANTARCTICA Tsan Mo, Yong Han, and FuzhongWengNOAA/NESDISCenter for Satellite Applications and Research (STAR)IEEE IGARSS, Vancouver, CanadaJuly 29, 2011

2. 7/29/2011IEE IGARSS 20112INTRODUCTION●Antarctica: Long winter months with ~24-hour nighttime● Minimal diurnal variability in data● Data used in this report: NOAA-18 and NOAA-19 MHS over Antarctica (82o-70oS) NOAA-18 and NOAA-19 AMSU-A over Antarctica● Ascending and Descendingtime series ● 30-day mean near-nadir bright temperatures (BT) ● ∆T =(Ascending - Descending) to demonstrate diurnal effect● ∆T = (NOAA18 - NOAA19) to determine Intersatellite/intersensor Calibration Bias (ICB)

3. 7/29/2011IEE IGARSS 20113Microwave Humidity Sounder (MHS)● MHS (built by EUMETSAT) has flown onboard NOAA-18, NOAA-19, and MEOP-A since May 20, 2005● MHS central channel frequencies

4. Local Equatorial Crossing Times (LECT) & Operational Statuses of the NOAA and METOP Satellites 7/29/2011IEE IGARSS 20114

5. NOAA-19 On-orbit Verification of NE∆T:AMSU-A (Ch.1-15) and MHS (Ch.16-20)7/29/2011IEE IGARSS 20115

6. Long-Term Monitoring of Instrument Performance for Life ● Instrument performances are continuously monitored for life of mission● Calibration counts, NE∆T, and housekeeping sensors are monitored and posted on NOAA/STAR Online Monitoring Website● Sample results are shown on following slides7/29/2011IEE IGARSS 20116

7. NOAA-18 MHS NE∆T & Ch.Gain7/29/2011IEE IGARSS 20117NE∆T (K)

8. NOAA-19 MHS NE∆T & Ch.Gain7/29/2011IEE IGARSS 20118NE∆T (K)

9. NOAA-18 MHS Ch. 1NE∆T:● Ten days● Thirty days● One Year● Life time since launch 7/29/2011IEE IGARSS 20119

10. ● Ascending (++) and descending (xx) 30-day mean MHS BT near nadir from NOAA-18 & NOAA-19 ● Feb. 10 – Dec. 31, 2009 over Antarctica. ● NOAA-19 was launched on Feb. 6, 2009.7/29/2011IEE IGARSS 201110NOAA-18 and NOAA -19 MHS BT Over ANTARCTICA

11. (a) ∆T=Ascending – Descending(b) ∆T=NOAA18-NOAA19●Little diurnal effect during the Antarctic winter months ● ICBs (defined as mean over days of 90- 240) are small● NOAA-19 data are available only after day 40 as it was launched on 6 February 20097/29/2011IEE IGARSS 201111

12. Ascending Local Equator Crossing Time (LECT)7/29/2011IEE IGARSS 201112

13. ●7/29/2011IEE IGARSS 201113AMSU-A:∆T= NOAA18 –NOAA19 Differences of 30-day mean brightness temperatures between NOAA-18 and NOAA-19 measurements at nadir over Antarctica. The NOAA-19 data are available only after day 40 as it was launched on 6 February 2009.● Relative channel biases, which are defined as the mean ΔT values over July when the Antarctica is nearly 24-hour nighttime● The vertical lines indicate the inter-year location.

14. 7/29/2011IEE IGARSS 201114Summary● BOTH AMSU-A and MHS BT over Antarctica show that there is minimal diurnal variability in the winter months with 24-hour nighttime● These measurements over Antarctica provide a practical approach to determine the Intersatellite/intersensor Calibration Biases (ICBs)● It shows that Antarctica is good natural site for cal/val of space-borne microwave radiometers (MR)● Establishment of a natural site for calibration reference is an important addition to the few tools available to date for cal/val of space-borne MR

15. REFERENCES● Tsan Mo, “Calibration of the NOAA AMSU-A Radiometers With Natural Test Sites,” IEEE Transe. Geosci. Remote Sens., 2011, in press● Tsan Mo,"A Study of the NOAA Near-Nadir AMSU-A Brightness Temperatures over Antarctica, " J. Atmospheric and Oceanic Technology, 27, 995-1004, DOI: 10.1175/2010JTECHA1417.1, June 2010.● STAR Online Monitoring Website: (N. Sun, STAR Webmaster)http://www.star.nesdis.noaa.gov/smcd/spb/icvs/satmonitoring_n19_amax.php7/29/2011IEE IGARSS 201115

16. 7/29/2011IEE IGARSS 201116Thank You

17. Climate Trends from NOAA-15 AMSU-A Measurements7/29/2011IEE IGARSS 201117●Channel 15 measurements are closest to the Earth’s surface●Channel 9 measurements are near the tropopause.●Channels 15 and 1-8 measurements are at multiple levels in troposphere ●Channels 10-14 measurements are at multiple levels in stratosphere●The chart on the right shows the climate trends at multiple levels of atmosphere from 0 to 50 km.●Troposphere is warming and stratosphere is coolingNOAA-15 AMSU-A Data from May 1998 through Dec. 2007 are used to derive these trends. Data at Channels 6 and 11 are not used due to channel failuresT. Mo, (2009), JGR, 114, D11110

18. NOAA-18 AMSU-ANE∆T7/29/2011IEE IGARSS 201118

19. 7/29/2011IEE IGARSS 201119MHS NEEAR-NADIR MEASUREMENTS OVER ANTARCTICA ● Ascending and descending 30-day MHS mean brightness temperatures near nadir from: (a) NOAA-18, (b) NOAA-19, and (c) METOP-A measurements over Antarctica in 2010.