Light blue lines in the plots made through the OCS data pages indicate climatological averages, computed as described below.

Reynolds and Smith AOI SST Climatology (1971 - 2000)

The AOI SST climatology is an optimum interpolation analysis of sea surface temperature with an adjusted base period of 1971 to 2000, on a global 1 degree by 1 degree by 1 month grid.

For further information, see:

Smith, T. M. and R. W. Reynolds, 1998: A high resolution global sea surface temperature climatology for the 1961-90 base period. J. Climate, 11, 3320-3323.

Xue, Y., T.M. Smith and R.W. Reynolds, 2002: A new SST climatology for the 1971-2000 base period and interdecadal changes of 30-year SST normals. J. Climate in revision.

ICOADS Winds, Sea Level Pressure, Air Temperature, Relative Humidity (1971 - 2000)

The ICOADS climatologies of zonal and meridional wind, wind speed, wind direction, sea level barometric pressure, air temperature, and relative humidity are shown on time-series plots of OCS data for comparison with observations.

Subsurface Temperature, Salinity, and Sigma-Theta (1955-2006)

The World Ocean Atlas 2009 temperature climatology is shown in profile plots. The salinity and sigma-theta climatologies are shown in both profile plots of salinity and sigma-theta, and in time-series plots of sea surface salinity and sea surface density. Sigma-Theta is computed from temperature and salinity as described below.

For more information see www.nodc.noaa.gov/OC5/WOD/docwod.html

Smoothing of World Ocean Atlas Data

Due to the sparse sampling of the World Ocean Atlas data, we have applied smoothing with triangle filters of width 21 degrees in X, 3 degrees in Y, and 3 months in time. The time range of the input data for the climatology was divided into five decades: 1955-1964, 1965-1974, 1975-1984, 1985-1994, and 1995-2006. A climatology was computed for each decade, and then these decadal climatologies were averaged together.

Sigma-theta is computed as follows:

Salinity is combined with potential temperature computed from the World Ocean Atlas temperature climatology to compute the potential density anomaly (sigma-theta) defined as 

sigma-theta = 1/V(S,Theta,P) - 1000 kg m-3

where V is specific volume, S is salinity, Theta is potential temperature and P is set to zero. The algorithms used in these calculations are from "Algorithms for computation of fundamental properties of seawater" by Fofonoff and Millard (UNESCO technical papers in marine science, 44, 1983).

Shortwave Radiation (1983-2007)

The shortwave solar radiation climatology was computed from the monthly mean net shortwave radiation analysis of the International Satellite Cloud Climatology Project (ISCCP) which is hosted on the OAFlux Project site at the Woods Hole Oceanographic Institution. Net shortwave radiation was converted to incoming shortwave by dividing by the albedo of the ocean surface 0.945.

Longwave Radiation (1983-2007)

The longwave radiation climatology was computed from the monthly mean net longwave radiation analyis of the International Satellite Cloud Climatology Project (ISCCP) which is hosted on the OAFlux Project site at the Woods Hole Oceanographic Institution. Net longwave is converted to upwelling longwave using the equation

LW = sbc * (SST + rkel)**4 - LWnet / epslw

where SST is the OAFlux sea surface temperature, the emissivity epslw = 0.97, the Stefan-Boltzman constant sbc = 5.67e-8 W/(m^2 K^4), and rkel = 273.15 converts degree centrigade to degree kelvin.

Xie-Arkin Precipitation (1979 - 2002)

The monthly analysis of precipitation from Xie-Arkin (2011) was used to compute a climatology. Smoothing was applied using triangle filters of widths 21° in X, 3° in Y, and 3 months in time.

Sea Surface Fluxes

Climatologies of sea surface fluxes of latent, sensible, and net heat, net shortwave and longwave radiation, specific humidity, and evaporation, are computed from OAFlux Project data, from the Woods Hole Oceanographic Institution. The base period for the OAFlux climatologies is 1983-2007. The climatology of evaporation minus precipitation is computed from the climatologies of OAFlux evaporation minus Xie-Arkin precipitation. Climatologies of zonal and meridional wind stress and wind stress magnitude are computed from ERS12 satellite data using the base period 1991-2000.