An Improved Near-Surface Specific Humidity and Air Temperature Climatology for the SSM/I Satellite Period

Abstract

A near-surface specific humidity (Qa) and air temperature (Ta) climatology on daily and 0.258 grids was constructed by the objectively analyzed air-sea fluxes (OAFlux) project by objectively merging two recent satellite-derived high-resolution analyses, the OAFlux existing 18 analysis, and atmospheric reanalyses. The two satellite products include the multi-instrument microwave regression (MIMR) Qa and Ta analysis and the Goddard Satellite-Based Surface Turbulent Fluxes, version 3 (GSSTF3), Qa analysis. This study assesses the degree of improvement made by OAFlux using buoy time series measurements at 137 locations and a global empirical orthogonal function (EOF) analysis. There are a total of 130 855 collocated daily values for Qa and 283 012 collocated daily values for Ta in the buoy evaluation. It is found that OAFlux Qa has a mean difference close to 0 and a root-mean-square (RMS) difference of 0.73 g kg 21, and Ta has a mean difference of 20.038C and an RMS difference of 0.458C. OAFlux shows no major systematic bias with respect to buoy measurements over all buoy locations except for the vicinity of the Gulf Stream boundary current, where the RMS difference exceeds 1.88C in Ta and 1.2 g kg 21 in Qa. The buoy evaluation indicates that OAFlux represents an improvement over MIMR and GSSTF3. The global EOF-based intercomparison analysis indicates that OAFlux has a similar spatial-temporal variability pattern with that of three atmospheric reanalyses including MERRA, NCEP-1, and ERA-Interim, but that it differs from GSSTF3 and the Climate Forecast System Reanalysis (CFSR).

An Intermodel Approach to Identify the Source of Excessive Equatorial Pacific Cold Tongue in CMIP5 Models and Uncertainty in Observational Datasets

“…However, we notice that the qa values of both MIMR and GSSTF3 are even higher averaged over the global ice-free ocean than those of the OAFlux analysis (see Fig. 4a of Jin et al 2015), particularly in the tropical oceans (see Figs. 5a and 7a of Jin et al 2015).…”

“…4a of Jin et al 2015), particularly in the tropical oceans (see Figs. 5a and 7a of Jin et al 2015). This implies that the error of an LHF underestimation due to the overestimated qa would not be reduced in the ongoing OAFlux product (so far the new OAFlux data are not obtained online as the work is still going on).…”

“…On the other hand, NCEP analyses are indeed found to be too moist above the tropical Pacific based on the comparison with in situ measurements (Large and Yeager 2009). In recent years, the OAFlux project is devoting great effort to constructing a higher-resolution product of qa by objectively merging two recent satellite-derived analyses [i.e., the multi-instrument microwave regression (MIMR; Jackson et al 2009) and the Goddard Satellitebased Surface Turbulent Fluxes, version 3 (GSSTF3; Shie et al 2012)] with the existing OAFlux analysis and atmospheric reanalyses (Jin et al 2015). However, we notice that the qa values of both MIMR and GSSTF3 are even higher averaged over the global ice-free ocean than those of the OAFlux analysis (see Fig.…”

The Global Ocean Water Cycle in Atmospheric Reanalysis, Satellite, and Ocean Salinity

“…CFSR is the only reanalysis that features a weakly coupled atmosphere-ocean-land reanalysis; all the other reanalyses are atmospheric-only reanalyses in which the atmospheric state is forced by the imposed SST boundary conditions at the ocean surface. The inclusion of weakly coupled data assimilation in CFSR has a potential for better depiction of the overall atmosphere-ocean feedback processes than the uncoupled data assimilations (Wen et al 2012;Kumar and Hu 2012;Jin and Yu 2013).…”

Variations of the Global Net Air–Sea Heat Flux during the “Hiatus” Period (2001–10)

“…The objective synthesis was based on a least squares estimator that seeks the optimal values for the fluxrelated variables that best fit input data sources. The version used here is the new 0.258 gridded analysis that has been recently developed using satellite observations from 1987 to present (Yu and Jin 2014a,b;Jin et al 2015). Different from the previous 18 version, no reanalysis products are used in this new analysis.…”