CRTF Telecon - 02-25-2015

Summary by Xiquan Dong and Erica Dolinar:

Climate Reanalysis Task Force (CRTF) Teleconference
February 25, 2015 2:00 pm (EST)

Presentations

- NOAA Objective Sea Surface Salinity (SSS) Analysis (P. Xie, Y. Xue, and A. Kumar; NOAA Climate Prediction Center)
o Production of analysis products and real-time operational applications
o Collaborative effort between
 NESDIS/NODC
 NESDIS/STAR
 NWS/CPC
o NOAA Blended Analysis of Surface Salinity (BASS)
 Global ocean analysis on 1° × 1° grid
 Monthly (or finer) time scale starting in January 2010
o Large scale salinity distributions from in-situ (Argo/buoy) and Level-2 retrievals (SMOS and Aquarius)
o Blend Strategy; 2 step approach
 Bias correction of satellite retrievals
 Blend the in-situ observations with the bias corrected retrievals
o After the adjustments, statistics show improvements in bias, RMSE, and correlation
o Salinity PDFs match well after adjustments
o OI combining of in-situ measurements and retrievals (not the analysis)
 Tropical and global results are best for the blended analysis
o NODC analysis defined by interpolating in-situ measurements with distance-weighting
 Analysis error is largest over high latitudes
o SSS correlations with precipitation and evaporation
o Questions:
 Why does the analysis not fix the reduced SSS in the tropical Pacific?

- Assessing the uncertainties in Atmospheric Reanalyzed Surface Freshwater Budgets using satellite-based freshwater products and ocean salinity observations (Lisan Yu and Xiangze Jin; Woods Hole Oceanographic Institution with collaborators Y. Xue and A. Kumar; NOAA)
o Uncertainties in surface freshwater flux products (e.g. precipitation and evaporation) including the mean pattern, seasonal cycle, and trends
 NCEP1, NCEP2, CFSR, Era-I, JRA-55, MERRA, 20CRv2
o Satellite precipitation products (OAFlux, GPCP, CMAP)
o Focusing on E-P and salinity change (ΔS/Δt)
o Most reanalyses over predict global precipitation (P) and evaporation (E) (smaller standard deviation in E)
o Zonal averages and time series (long-term and annual average)
o Issues with CFSR and MERRA
 Artificial jump in the trends of E and P near 1998
o Where does E-P contribute most to salinity change?
 Eastern tropical Pacific and eastern tropical Atlantic
o Era-I produces the best E-P product compared to observations
o Questions:
 Can the artificial jump in CFSR and MERRA be attributed with ENSO?

Other orders of business
- Technical Workshop at NCEP (Early May)

I will contribute a 20-min talk on "Using satellite salinity observations to evaluate the atmospheric reanalyzed evaporation-precipitation products".

Lisan

I can talk about 30 minutes on "Evaluation of tropical Pacific observing system using NCEP and GFDL ocean data assimilation system:
Impacts of Argo data on salinity analysis"

Yan

NCEP and GFDL have done coordinated Ocean Observing System Experiments and hindcast forecast runs to access the relative role of TAO/TRITON and Argo data on the quality of ocean reanalysis and ENSO forecast skill. We found that assimilation of Argo salinity is critical in constraining model salinity biases and improving
model salinity variability in both systems. Improvement in salinity analysis leads to a significant improvement in
sea surface height and surface current analysis, which are known to influence ENSO predictability. Therefore, variations in freshwater fluxes and their impacts on salinity variability
are important components of the air-sea coupled system, and should be well represented by climate reanalysis.

Yan from CPC/NCEP