The following are additional analyses in support of the PACS Program. The choice of analyses was made by John M. Wallace and Todd P. Mitchell of the Joint Institute for the Study of the Atmosphere and Ocean of the University of Washington.
Climatological June-July-August Preciptiation from Legates/MSU and GPI (1986-95)
a) land data from Legates & Willmott and ocean data from the Microwave Sounding Unit, and b) data from GPI. The digital values are available as a netCDF file.
Eastern Pacific Cold Season Precipitation in Warm and Cold Years, and Difference Map
The top and middle panels show typical cold season precipitation in the years 1979-92 during warm and cold ENSO episodes, respectively. The precipitation is estimated from the Microwave Sounding Unit measurements. The difference between these maps, divided by 2, is shown in the bottom panel. Precipitation amounts at 8° N, 125° W are the same in ENSO warm and cold episodes. The cold season is defined as July through November. Similar analyses can be found in Mitchell and Wallace (1996, J. Climate, 9, 3149-3161).
Eastern Pacific Cold Season Sea Surface Temperature (SST) in Warm and Cold Years, and Difference Map
The top and middle panels show typical cold season SST in the years 1979-92 during warm and cold ENSO episodes, respectively. Contour interval is 1° C, and the 27° C isotherm is thickened. The difference between these maps, divided by 2, is shown in the bottom panel (contour interval of 0.25° C, with zero contour thickened). The cold season is defined as July through November. Similar analyses can be found in Mitchell and Wallace (1996, J. Climate, 9, 3149-3161).
Mean August-September Precipitation in the Eastern Pacific from MSU and GPI Estimates, and their difference
The top and middle panels are for MSU and GPI, respectively. Increases in shading intensity for precipitation amounts > 10, 30, & 50 cm month-1. Bottom panel is the difference, MSU minus GPI. Heavy contour indicates no difference, and shading indicates MSU > GPI by 10, 20, 30, & 40 cm month-1. Clipperton Island is located at 10.3°N, 109° W..
Tropical Land Temperature and Eq. Pacific Sea Surface Temperature Anomalies (° C/4)
Land temperatures in the tropics are strongly influenced by the ENSO phenomenon, as captured by variations in Eq. Pacific cold tongue SST anomalies. The strongest correlations (0.72) are found with the land temperatures lagging cold tongue SST by 4 months. A similar strong relationship is found for data back to 1900.Land temperature anomalies are averaged between 20° N to 20° S for the tropical belt, and the sea surface temperature (SST) anomalies are averaged for the equatorial Pacific cold tongue region (6° N to 6° S, 180-90° W). Both series have been smoothed with a 5-point running mean, and the SST anomalies have been divided by 4 so that they can be plotted on the same ordinate as the land temperature. Compressed PostScript files are available for both color and in black and white versions of this plot. Gridded analyses of land surface temperature anomalies, from which the time series was derived, were prepared by Phil Jones and collaborators. Documentation and digital values for the gridded land data may be obtained here. Additional analyses and digital values of the cold tongue SST anomaly time series are available elsewhere on this page. Analysis by Alison McLaren (alison@atmos.washington.edu).
Western & Central Eq. Pacific Zonal Wind Anomalies (m s-1) (shading) & CTI (C)
Historical Record: 1854-1992
The monthly-mean time series have been smoothed with successive 9- and 5-point running means. Digital values are available here.
Equatorial Pacific Island Precipitation Index and Cold Tongue Sea Surface Temperature Anomalies (° C)
The historical record 1890-1992:
Compressed PostScript files are available for both color and in black and white versions of this plot.
As is well known, island precipitation in the equatorial Pacific is strongly influenced by the ENSO phenomenon, as captured by variations in Eq. Pacific cold tongue SST anomalies.
The tropical land precipitation index is the average of normalized anomalies in the region 12° N to 12° S, 152.5° E to 82.5° W, and the cold tongue index is the average of sea surface temperature (SST) anomalies in the region 6° N to 6° S, 180-90° W. The precipitation index has been standardized with respect to the period 1950-89. Both series comprise seasonal means and have been smoothed with a 5-point running mean. Gridded analyses of land precipitation anomalies, from which the time series was derived, were prepared by Jon Eischeid and collaborators. Documentation and digital values for the gridded land data may be obtained here. Digital values for the precipitation index may be obtained here. Additional analyses and digital values of the cold tongue SST anomaly time series are available elsewhere on this page.
Tropical Non-Pacific Land Precipitation Index and Cold Tongue Sea Surface Temperature Anomalies (° C)
The historical record 1870-1992:
The precipitation index values have been multiplied by (-1).
Compressed PostScript files are available for both color and in black and white versions of this plot.
Tropical land precipitation outside of the Pacific basin region is suppressed during warm episodes of the ENSO phenomenon, as captured by variations in Eq. Pacific cold tongue SST anomalies.
The precipitation index is the average of normalized anomalies in the region 28° N to 28° S, 82.5° W to 152.5° E, and the cold tongue index is the average of sea surface temperature (SST) anomalies in the region 6° N to 6° S, 180-90° W. The precipitation index has been standardized with respect to the period 1950-89. Both series comprise seasonal means and have been smoothed with a 5-point running mean. Gridded analyses of land precipitation anomalies, from which the time series was derived, were prepared by Jon Eischeid and collaborators. Documentation and digital values for the gridded land data may be obtained here. Digital values for the precipitation index may be obtained here. Additional analyses and digital values of the cold tongue SST anomaly time series are available elsewhere on this page.
Annual Mean Sea Surface Temperature and Surface Wind,and Annual Total Precipitation
Annual mean sea surface temperatures (SSTs) indicated by blue to red shading for SSTs between 26 and 29.5° C, respectively; surface vector winds plotted for wind speeds greater than 3 m s-1; and annual precipitation totals indicated by orange to yellow shading for totals in excess of 3 m. The western equatorial Pacific is characterized by a broad region of warm SST, convergence of the surface winds, and persistent precipitation centered at between 5 and 10° latitude in each hemisphere.
Interdecadal Changes in Sea Surface Temperature
Annual mean SST (C) for 1977 to 1992 minus the annual mean SST for 1950 to 1976.
March-April Average Planetary Albedo
Four year average (1974-1978) of planetary albedo from visible satellite imagery. Shading for albedo > 0.2, with darker shading for 0.05 increments in albedo. Both convective and stratiform cloud are associated with higher albedo values. The equatorial double ITCZ and the stratiform cloud region off of the Chilean coast are evident in this analysis.Annual Mean Precipitation (m) from Legates/MSU, GPI, & Legates/MSU minus GPI (0.6m)
Historical Record of Eastern Equatorial Pacific SST Anomalies (C)
The time series has been smoothed and filled with a 5-point running mean for plotting. Click here to view and/or obtain the digital values of the time series.
Historical Record of Darwin Sea-Level Pressure Anomalies (mb)
The time series has been smoothed and filled with a 5-point running mean for plotting. Click here to view and/or obtain the digital values of the time series. Data courtesy of Michael Halpert (mhalpert@sun16.wwb.noaa.gov) of the NOAA Climate Prediction Center.
Historical Record of Tahiti Sea-Level Pressure Anomalies (mb)
The time series has been smoothed and filled with a 5-point running mean for plotting. Click here to view and/or obtain the digital values of the time series. Data courtesy of Michael Halpert (mhalpert@sun16.wwb.noaa.gov) of the NOAA Climate Prediction Center.
Historical Record of the "Southern Oscillation Index"
The time series has been smoothed and filled with a 5-point running mean for plotting. Click here to view and/or obtain the digital values of the time series. Data courtesy of Michael Halpert (mhalpert@sun16.wwb.noaa.gov) of the NOAA Climate Prediction Center.
Seasonal Dependence of ENSO Precipitation and Upper-atmosphere Geopotential Height Anomalies
Regression of microwave sounding unit (MSU) ocean precipitation (shading) and tropospheric mean temperature (channel 2) (contours) on simultaneous normalized values of eastern equatorial Pacific SST (6N-6S, 180-90W) during the climatological warm (January through May) (upper panel) and cold (July through November) (lower panel) months. Red (blue) shading for precipitation regressions >15 (< -15) mm month-1 / unit normalized SST index. Contour interval of 0.1 C / unit normalized SST index, with gold (green) contours for positive and zero (negative) regression values. Analysis period is 1979 to 1991.
Intraseasonal Variability of Convection and Upper-atmosphere Geopotential Height
Composites of outgoing longwave radiation (OLR) (shading) and 200 hPa streamfunction (contours) during weak (upper panel) and intense (lower panel) convective intraseasonal periods during June-July-August of 1979. Olive (tan) shading indicates OLR values in the range 220-200 W m-2 (< 200 W m-2), and the streamfunction contour interval is 5 x 10**6 m-2 s-1. After Magana and Yanai (1991, J. Climate, 4, 180-201). Courtesy of Victor Magana (victor@belenos.atmosfcu.unam.mx) of the Universidad Nacional Autonoma de Mexico.
Relationship Between Wet Season Precipitation in Northeast Brazil and SST
Correlation between average February through May precipitation in northeast Brazil and SST. Red (blue) shading indicate above (below) normal SST correlations. SST data from the COADS. Analysis period is 1946 to 1985. Similar patterns and strengths of correlations is obtained for analyses for 1854 to 1899 and 1900 to 1945 (not shown). (See also Ward and Folland (1991, Int. J. Climatology, 11, 711-743).)
