The various Climatologies used by the TAO Project to compute anomalies
are briefly described below.
Reynolds and Smith SST Climatology (1981 - 2010)
The SST climatology was constructed at the National Centers for Environmental Prediction (NCEP) by merging monthly SST fields of ERSST.v3b (Smith et al., 2008) for 1981 with OI.v2 SST (Reynolds et al., 2002) for 1982-2010. The source files for this climatology are located at this website. The file Note_SST_Climatology_1981-2010.doc on this website has further information. Also on the website are graphics showing small differences (generally less than 0.3C) between this and the previous climatology with base period 1971-2000.
For further information, please see:
Reynolds, R. W., N. A. Rayner, T. M. Smith, D. C. Stokes and W. Wang, 2002: An improved in situ and satellite SST analysis for climate. J. Climate, 15, 1609-1625.
Smith, T.M., R. W. Reynolds, T. C. Peterson, and J. Lawrimore, 2008: Improvements to NOAA’s historical merged land-ocean surface temperature analysis (1880-2006). J. Climate, 21, 2283-2296.
Xue, Y., T. M. Smith, and R. W. Reynolds, 2003: Interdecadal changes of 30-yr SST normals during 1871-2000. J. Climate, 16,1601-1612.
Subsurface Temperature Climatology (Tropical Pacific Ocean, 1920s-1991)The Kessler temperature climatology is a 4-D objective analysis of historical XBT and CTD temperatures, which uses estimates of the correlation lengths in longitude, latitude, and time to grid the data. The data used in the analysis consist of all available CTD observations from the 1960s through 1991, plus earlier hydrocast station data, some as early as the 1920s. The XBT data range in time from 1970 to 1987. Basic data sets and procedures are described in Kessler (1990) and Kessler and McCreary (1993).
After merging of XBT and CTD data, we further smoothed the climatologies to eliminate unrealistic features related to uneven data distribution in space and time. We then blended this climatology with the Reynolds and Smith SST climatology to ensure consistency between surface anomalies appearing in vertical and horizontal temperature analyses. Blending was done such that surface values were set to Reynolds and Smith and values between 0 and 50 m generated by linear interpolation between SST and Kessler values at 50 m. Any discontinuities across 50 m were smoothed out and any near surface temperature instabilities generated by this blending were eliminated. As a final step, monthly values were smoothed with a 1-2-1 filter in time to eliminate small amplitude month-to-month noise variations.
This climatology is used to compute subsurface temperature anomalies, and to grid temperature data in Longitude-Depth and Latitude-Depth sections. A special exception to this is along 95°W for Latitude-Depth sections. Since we have data at 12°N during the EPIC program, which are located outside the domain of the modified Kessler climatology (extending only to 10°N), we use instead the Bureau of Meteorology Research Center (BMRC) temperature climatology (Smith, 1995) at all latitudes along 95°W so that the anomalies in the 95°W depth-section plots are coherent and extend to 12°N. This introduces a small inconsistency between anomalies shown in the depth-longitude and latitude-depth section plots at 95°W. For more information on how these TAO data are gridded, see the Depth-Longitude Gridding and Latitude-Depth Gridding web pages.
For additional information see:
Kessler, W.S., 1990: "Observations of long Rossby waves in the northern tropical Pacific". J. Geophysical Research, 95(C4), 5183-5217 (abstract),
Kessler, W.S. and J.P. McCreary, 1993: "The annual wind-driven Rossby wave in the subthermocline equatorial Pacific". J. Phys. Oceanogr., 23(6), 1192-1207 (abstract)
Smith, N. R., 1995: "An improved system for tropical ocean sub-surface temperature analyses". J. Atmos. Oceanic Technol., 12, 850-870.
Subsurface Temperature Climatology (Alantic and Indian Oceans, 1955-2006)The World Ocean Atlas 2009 temperature climatology is used to compute subsurface temperature anomalies, and to grid temperature data in longitude-depth and latitude-depth sections at locations other than the tropical Pacific. It is also used in time series and profile displays. Due to the sparse sampling of the input data used to create this climatology, 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.
For additional information see www.nodc.noaa.gov/OC5/WOD/docwod.html
ICOADS Winds (1971 - 2000)The ICOADS climatologies of zonal and meridional wind, scalar wind speed, and wind direction, are used for computing TAO wind anomalies, and for gridding zonal and meridional Winds and scalar wind speed in the latitude-time section plots. To make plots of TAO winds and their anomalies see the TAO/TRITON Display and Delivery page. For information on the gridding methods mentioned above, see the Latitude-Time Gridding web page.
ICOADS Relative Humidity (1971 - 2000)The ICOADS relative humidity (RH) climatology is used for computing TAO RH anomalies, and for gridding RH in the latitude-longitude maps and latitude-time section plots. For example plots of RH see the "Assorted Plots" on the TAO/TRITON Data Display page. For information on these gridding methods, see the Latitude-Longitude Gridding and Latitude-Time Gridding web pages.
ICOADS Sea Level Barometric Pressure (1971 - 2000)The ICOADS sea level pressure (SLP) climatology is used for computing SLP anomalies, and for gridding SLP in the latitude-time section plots. For information on gridding methods, see the Latitude-Time Gridding web page.
20°C Isotherm DepthThe 20°C isotherm depth climatology was computed from the Kessler temperature climatology (see above), by linear interpolation of depth versus temperature. This climatology is used in the tropical Pacific ocean.
Similarly, for the Atlantic and Indian oceans, a 20°C isotherm depth climatology was computed from the World Ocean Atlas 2009 temperature climatology (see above).
These climatologies are used for computing 20°C isotherm depth anomalies, and for gridding 20°C depths in the latitude-longitude maps and latitude-time section plots. To make plots of 20°C depth see the TAO/TRITON Data Display page. For information on these gridding methods, see the Latitude-Longitude Gridding and Latitude-Time Gridding web pages.
Dynamic HeightThe dynamic height climatology was computed from the Kessler temperature climatology (Pacific ocean) and the World Ocean Atlas 2009 temperature climatology (Atlantic and Indian oceans) by vertically integrating the specific volume anomaly using a set of long-term mean temperature-salinity relations, one for each grid location, derived from the World Ocean Atlas 2009.
These climatologies are used to compute dynamic height anomalies, and for gridding dynamic heights in the latitude-longitude maps and time section plots. For example plots of dynamic height see the TAO/TRITON Display and Delivery page. For information on these gridding methods, see the Latitude-Longitude, Time-Logitude, and Latitude-Time gridding pages.
Salinity and Sigma-Theta (1955-2006)The World Ocean Atlas 2009 includes salinity and temperature climatologies. These climatologies are used to compute anomalies, as well as in time series and profile displays. The salinity and temperature climatologies are used to compute a climatology of sigma-theta, which is used to compute sigma-theta anomalies. Due to the sparse sampling of the input data used to create these climatologies, 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).
For additional information see www.nodc.noaa.gov/OC5/WOD/docwod.html
Shortwave Radiation (1983-2007)The shortwave solar radiation climatology was computed from monthly mean net shortwave radiation analyis of the International Satellite Cloud Climatology Project (ISCCP) which is hosted on the OAFlux Project ftp 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 (1945-1989)The outgoing longwave radiation climatology from the "ATLAS of Surface Marine Data" (da Silva et al, 1994) is used to compute anomalies.
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 Ocean CurrentsThe surface current climatology from Reverdin et al (1994) is used to compute anomalies.
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