Trends in wind and sea‐level pressure in the tropical pacific ocean for the period 1950–1979

Abstract

The COADS (Comprehensive Ocean-Atmosphere Data Set) sea-level pressure observations over the tropical Pacific Ocean during the period 195G-1979 are examined to check for dynamical consistency between the observed trends in wind-speed components and the trends in sea-level pressure pattern. There appears to be some evidence that the South east Pacific High and the equatorial trough in the central Pacific were gaining strength. As a result, trade winds appear to have been gaining strength along the northern flank of the South east Pacific High and in the eastern/central equatorial Pacific. However, there were considerable variations in those trends from decade to decade. The patterns of those decadal changes in sea-level pressure appear to be dynamically consistent with those of wind tendency. An example of a quantitative consistency check for a region located at 160"W-150°W and IO"S-20"S demonstrates that the observed strengthening trend in zonal wind component in the region appears to be dynamically consistent with the observed air-pressure field measured by both ships and the nearby island stations. It also demonstrates clearly that the overall magnitudes of change in the two independently measured fields (ship-observed winds and sea-level pressure) over the 30-year period are quantitatively of the right order. These observations at least suggest that the qualitative nature of the observed trends in the trade winds in the Pacific since 1950 is real.

Comparison of coastal wind and pressure trends over the tropical atlantic: 1946–1987

“…The COADS pressure and wind observations have been found to be internally consistent in several other studies (e.g. Bunker, 1980;Woodruff et a/., 1987;Flohn and Kapala, 1989;Bigg, 1992;and Inoue and Bigg, 1993). Previous studies that examined a limited number of land pressure records (e.g.…”

“…The shiprecorded data derives from the trimmed Comprehensive Ocean Atmosphere Data Set (COADS; Woodruff et ul., 1987), whiie the land-based station data comes from the Surface Station Climatology Data Set produced by the National Center for Atmospheric Research. Note that Inoue and Bigg (1993) showed that pressure trends present in both the raw COADS and trimmed data set are essentially identical.…”

“…However, while a general qualitative agreement between pressure and wind trends is found the noise in the ship-recorded data does not allow a quantitative geostrophic analysis to be performed. Inoue and Bigg (1993), in examining the tropical Pacific, had a much less noisy pressure field with which to carry out such a geostrophic analysis. When such an analysis is done here the pressure trends are so large, with such large variance, that geostrophic wind trends can be up to an order of magnitude larger than the COADS suggests.…”

Methods to homogenize wind speeds from ships and buoys

“…Other sources of observational error include: differences from nominal observing time; the anemometer type, calibration, and location; errors in calculation of true wind from the relative wind (Kent et al, 1993;Gulev, 1999;Smith et al, 1999); rounding artefacts; and for Beaufort winds, the stage of development of the waves. Researchers have studied the relationship between Voluntary Observing Ship (VOS) winds and pressures and have concluded that in some cases the pressure and wind trends are consistent (Inoue and Bigg, 1995) and in some cases inconsistent (Posmentier et al, 1989;Ward and Hoskins, 1996). It is important, therefore, to correct marine wind data to account for inhomogeneities for which we have correction techniques, such as for measurement height and atmospheric stability (Dobson, 1981;Smith, 1988;Walmsley, 1988) and for the Beaufort equivalent scale used to convert from observations of sea state to a wind speed (Lindau, 1995a).…”

Wind Field Variations in the Tropical Pacific Ocean from Satellite Scatterometer Data

“…(2003) analyzed the wind data of northwestem Pacific and found that the wind field is related to Sonthem Oscillation Index (SOI), but has a half-year lag with respect to the SOL Besides the relationship between tropical Pacific wind fields and ENSO, the long-term variation of wind field has also been investigated. Inoue and Bigg (Inoue M, et al, 1995) analyzed COADS (Comprehensive OceanAtmosphere Data Set) sea-level pressure and wind observations and pointed out the trade winds gained strength over the eastedcentral equatorial Pacific during the period 195&1979. Clarke andLehedev(C1arkeA.…”