1 Daily OI Analysis for Sea Surface Temperature NOAA’s National Climatic Data Center Asheville, NC Richard W. Reynolds (NOAA, NCDC) Thomas M. Smith (NOAA, NCDC) Chunying Liu (NOAA, NCDC) Dudley B. Chelton (Oregon State University) Kenneth S. Casey (NOAA, NODC) Michael G. Schlax (Oregon State University)

2 The Good, the Bad and the Ugly NOAA’s National Climatic Data Center Asheville, NC Richard W. Reynolds (NOAA, NCDC) Thomas M. Smith (NOAA, NCDC) Chunying Liu (NOAA, NCDC) Dudley B. Chelton (Oregon State University) Kenneth S. Casey (NOAA, NODC) Michael G. Schlax (Oregon State University)

3 Daily OI: Products All products on 0.25° spatial grid AVHRR only –AVHRR Pathfinder Daily OI: January 1985-end of Pathfinder data (currently December 2005) –AVHRR Operational Daily OI: January 2006-present AMSR + AVHRR –AMSR + AVHRR Pathfinder Daily OI: June 2002 to end of Pathfinder data (currently December 2005) –AMSR + AVHRR Operational Daily OI: January present Test and use other satellite data: TRMM, ATSR, MODIS, ATSR, etc.

4 Top: AVHRR Pathfinder Bottom: AMSR-E For AVHRR: Absolute latitudes > 40° have roughly only 5 days of data Number of days increases toward the tropics Drop offs due to cloud cover For AMSR: Absolute latitudes > 40° have more than 20 days of data Drop offs due to precipitation in ITCZ and SPCZ Jan '03: Number of Days with Nighttime Obs 4

5 3-Day Gulf Stream Average Gradients Data –AVHRR –AMSR Analyses –Weekly OI.v2: AVHRR –Daily RTG-SST: AVHRR –Daily OI: AVHRR only –Daily OI: AMSR+AVHRR Missing Data: AMSR & AVHRR Daily OI resolution improved over OI.v2 AMSR+AVHRR best analysis resolution

6 3-Day Average Agulhas Gradients Data –AVHRR –AMSR Analyses –Weekly OI.v2: AVHRR –Daily RTG-SST: AVHRR –Daily OI: AVHRR only –Daily OI: AMSR+AVHRR Daily OI resolution improved over OI.v2 AMSR+AVHRR best analysis resolution Features partly fixed by topography

7 3-Day Eastern Tropical Pacific Gradients Daily OI resolution improved over OI.v2 AMSR+AVHRR best analysis resolution High Gradients in AVHRR lost in analyses Features are progress waves not partly fixed by topography

8 Random + Sampling Error OI Derived Sampling error dominant term Sampling and random error reduced by observations –Lower for AMSR+AVHRR

9 Bias Error Bias error derived from EOT modes used in correction –From modes supported by satellite data but not by in situ data –Bias error consider independent if from different satellites –Thus error lower for AMSR+AVHRR than AVHRR-only Total error: Sum Bias and Random + Sampling Variances

10 Ocean Coverage (%) Day and Night Coverage for –AVHRR Pathfinder ~12% –AVHRR Operations ~ 8% –AMSR ~40% Note Pathfinder coverage better then Operation –Pathfinder cloud contamination? AMSR coverage considerably better than AVHRR –Note data drop outs

11 Gulf Stream Gradient Index Index: –70°W-40°W –35°N-50°N Analyses –Weekly OI.v2 –RTG-SST –AVHRR-only –AMSR+AVHRR Seasonal cycle range –Similar minimum for daily analyses –Maximum roughly 40% for AVHRR+AMSR

12 Agulhas Gradient Index Index: –20°E-50°E –50°S-35°S Analyses –AVHRR-only –AMSR-only –AMSR+AVHRR AMSR drop out: 29 Oct - 5 Nov '03 –AMSR-only and AMSR+AVHRR indices drop –AVHRR+AMSR drop limited by AVHRR

13 SSTs & Gradients: 3-Day Average Data –AMSR Analyses –Daily OI: AVHRR only –Daily OI: AMSR+AVHRR Precipitation data void near 35°N & 130°W –Noise near boundary leads to OI interpolation errors –Note gradients

14 Analysis Differences: With respect to: Daily OI AMSR+AVHRR Top Panels - Analyses with bias correction –Weekly OI.v2 –Daily OI: AVHRR-only Bottom Panels - Analyses without bias correction –Daily OI: AVHRR-only –Daily OI: AMSR-only Daily OI: AVHRR-only without bias correction has largest biases

15 Data Anomalies 35°N-40°N, 70°W-60°W Day-to day noise related more to sampling than diurnal cycle Daily resolution difficult without more data Some smoothing needed for Daily OI

16 Data Anomalies: 11 Jan '03 AVHRR day & night –Note data scarcity AMSR day & night –Note swath width & precipitation –Day night differences may not always be due to diurnal warming

17 AMSR Data Anomalies: Jan '03 Differences appear to be strongly related to sampling –In particular region: 50°N-55°N, 50°W-40°W Similar differences for AVHRR

18 Data Anomaly Lag 1 Autocorrelation (r): Jul '02-Dec '05 Include temporal e-folding scale in OI based on r – 0<r<1

19 Long Term Data Anomalies: Jul '02-Dec '05 AMSR anomalies larger than AVHRR Day-night AMSR difference greater than day-night AVHRR difference –Due to tuning AVHRR to buoys?

20 To Maintain Credibility: Stress both the good and bad news Keep the descriptions short –Users will not read documentation Keep the number of products small –Users will not read documentation Keep data formats simple –Users will not read documentation