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- Author or Editor: W. C. Patzert x
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Abstract
Long-range P-3 aircraft have been used to occupy two 4000 km long sections from 20°N to 17°S along 150 and 158°W in the central equatorial Pacific. The temperature field along these sections was measured at approximately weekly intervals for three months (November 1977–January 1978). The principal meridional scales of variability derived from this data set suggest highly coherent fluctuations in the upper ocean thermal structure within ±10° of the equator. The region of coherent variability extends across the equator, across boundaries of major current systems and through the ITCZ. The time scale of these fluctuations is of order 2–3 months. Variability in the zonal direction is also coherent, although of smaller amplitude, with space scales of at least 2000 km and time scales of several months. These latter modes of variability are suggestive of propagating disturbances, although that hypothesis could not be proved with the current data set. The observed oceanic variability at 150°W was not closely related with changes in the local wind stress or curl of the wind stress field in the central tropical Pacific, suggesting that a large part of the observed oceanic fluctuations may not have been “locally” forced.
The relation between transports in the North Equatorial Countercurrent derived from the AXBT data and T/S relations agreed well with similar transport estimates obtained from hydrographic observations and current meter arrays. This suggests that the scales of variability we have observed in the temperature field may also apply, in part, to the zonal velocity and transport fields.
Abstract
Long-range P-3 aircraft have been used to occupy two 4000 km long sections from 20°N to 17°S along 150 and 158°W in the central equatorial Pacific. The temperature field along these sections was measured at approximately weekly intervals for three months (November 1977–January 1978). The principal meridional scales of variability derived from this data set suggest highly coherent fluctuations in the upper ocean thermal structure within ±10° of the equator. The region of coherent variability extends across the equator, across boundaries of major current systems and through the ITCZ. The time scale of these fluctuations is of order 2–3 months. Variability in the zonal direction is also coherent, although of smaller amplitude, with space scales of at least 2000 km and time scales of several months. These latter modes of variability are suggestive of propagating disturbances, although that hypothesis could not be proved with the current data set. The observed oceanic variability at 150°W was not closely related with changes in the local wind stress or curl of the wind stress field in the central tropical Pacific, suggesting that a large part of the observed oceanic fluctuations may not have been “locally” forced.
The relation between transports in the North Equatorial Countercurrent derived from the AXBT data and T/S relations agreed well with similar transport estimates obtained from hydrographic observations and current meter arrays. This suggests that the scales of variability we have observed in the temperature field may also apply, in part, to the zonal velocity and transport fields.
Abstract
Two west-to-cast temperature sections (∼2500 km in length) have been constructed from closely spaced (∼37 km) XBT measurements in the central South Pacific collected during Legs J and K of the Pacific GEOSECS Expedition. For these portions of track passing through the islands of the Tuamotu Archipelago, the main thermocline exhibited 50 m station-to-station variability on a scale too short to be resolved. In the open ocean away from these islands, the variability was smaller, 10–20 m, with only one 200 km scale eddy spatially resolved.
Abstract
Two west-to-cast temperature sections (∼2500 km in length) have been constructed from closely spaced (∼37 km) XBT measurements in the central South Pacific collected during Legs J and K of the Pacific GEOSECS Expedition. For these portions of track passing through the islands of the Tuamotu Archipelago, the main thermocline exhibited 50 m station-to-station variability on a scale too short to be resolved. In the open ocean away from these islands, the variability was smaller, 10–20 m, with only one 200 km scale eddy spatially resolved.
Two different satellite estimates of sea-surface temperature (SST) have been compared with observed temperature sections in the central tropical Pacific Ocean. The satellite products were found to be biased with respect to the observations by approximately 1–4°C. The bias field had a strong latitudinal and longitudinal structure. The spatial structure of this field and the large magnitude of errors in estimates of SST, if a normal situation, preclude the use of the satellite products by themselves in climatological studies of the area. However, if some means can be found to remove the bias from the satellite products then they will be marginally useful in the study of interannual variations of SST in the tropical Pacific.
The errors associated with the estimates of satellite SST are strongly linked to cloud cover and the amount of water vapor in the atmosphere, indicating present methods of correcting for these types of contamination are inadequate. The errors also depend on the number of observations that have gone into the satellite estimate of SST.
Two different satellite estimates of sea-surface temperature (SST) have been compared with observed temperature sections in the central tropical Pacific Ocean. The satellite products were found to be biased with respect to the observations by approximately 1–4°C. The bias field had a strong latitudinal and longitudinal structure. The spatial structure of this field and the large magnitude of errors in estimates of SST, if a normal situation, preclude the use of the satellite products by themselves in climatological studies of the area. However, if some means can be found to remove the bias from the satellite products then they will be marginally useful in the study of interannual variations of SST in the tropical Pacific.
The errors associated with the estimates of satellite SST are strongly linked to cloud cover and the amount of water vapor in the atmosphere, indicating present methods of correcting for these types of contamination are inadequate. The errors also depend on the number of observations that have gone into the satellite estimate of SST.
