Subsurface Ocean Temperature Research Articles

Far-reaching effects of the Hawaiian Islands on the Pacific Ocean-atmosphere system.

Using satellite data, we detected a wind wake trailing westward behind the Hawaiian Islands for 3000 kilometers, a length many times greater than observed anywhere else on Earth. This wind wake drives an eastward ocean current that draws warm water from the Asian coast 8000 kilometers away, leaving marked changes in surface and subsurface ocean temperature. Standing in the path of the steady trade winds, Hawaii triggers an air-sea interaction that provides the feedback to sustain the influence of these small islands over a long stretch of the Pacific Ocean.

SCIENCE AFFIRMS GLOBAL WARMING

APANEL OF LEADING U.S. SCIentists reported to President George W. Bush last week that global warming is really happening and that it could have serious adverse societal and ecological impacts by the end of this century. This conclusion could affect the President's policies in regard to energy and consideration of the Kyoto protocol. It may also affect the Administration's alternative plan of voluntary emissions targets that Bush is expected to present at a meeting of European Union leaders on June 14-15. In its report, the 11-member National Research Council (NRC) panel concludes that greenhouse gases are accumulating in the Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Global mean surface air temperatures warmed between 0.7 and 1.5 °F during the 20th century, the report says. And if present trends continue, global average temperatures will rise a further 2.5 to 10.4 °F ...

Relationship between East Asian winter monsoon, warm pool situation and ENSO cycle

Based on the observational data analyses and numerical simulations with the air-sea coupled model (CGCM), a new perspective on the occurrence mechanism of ENSO is advanced in this paper. The continuous strong (weak) East Asian winter monsoon will lead to continuous westerly (easterly) wind anomalies over the equatorial western Pacific region. The anomalous equatorial westerly (easterly) winds can cause eastward propagation of the subsurface ocean temperature anomalies (SOTA) in the warm pool region, the positive (negative) SOTA have been in the warm pool region for quite a long time. The eastward propagating of positive (negative) SOTA along the thermocline will lead to positive (negative) SSTA in the equatorial eastern Pacific and the occurrence of El Nino (La Nina) event. After the occurrence of ENSO, the winter monsoon in East Asia will be weak (strong) due to the influence of El Nino (La Nina).

Physical Mechanisms Responsible for the Transition from a Warm to a Cold State of the El Niño–Southern Oscillation

Abstract Based on the switch of a significant sea surface temperature anomaly (SSTA) over the central equatorial Pacific (the Nino-3.4 region) from ≥0.5°C to ⩽−0.5°C, three types of transitions from the warm (El Nino) to the cold (La Nina) phase of the El Nino–Southern Oscillation can be identified. They are the spring occurrence (SP) type, in which the SSTA first falls below −0.5°C in April or May after the termination of an El Nino event; the summer occurrence (SU) type, in which the SSTA does not reach this threshold until July or later; and the nonoccurrence (NON) type, in which the SSTA never reaches the threshold. Of the 12 El Nino episodes that occurred during the period of 1951–97, the number in each type is 3, 4, and 5, respectively. No significant difference in the SSTA composites can be found among the three types prior to the termination of the El Nino; however, the subsurface ocean temperatures have very different structures and temporal evolutions. Over the eastern equatorial Pacific, the th...

Interannual and Decadal Temperature Variability in the Southwest Pacific Ocean between 1955 and 1988

Abstract The spatial and temporal variability of the southwest Pacific Ocean is examined with the aim of describing the physical processes operating on interannual and decadal timescales. The study takes advantage of a new temperature atlas of the upper 450 m of the southwest Pacific Ocean, obtained from 40 000 bathythermograph profiles between 1955 and 1988. Rotated principal components analysis was used to filter the important spatial and temporal scales of temperature variability in the data. Three different analyses are presented. They include two intraocean analyses and a joint analysis of subsurface ocean temperature, sea level pressure, and surface winds. The dominant El Nino mode describes the large vertical excursions of the thermocline in the western tropical Pacific in response to atmospheric forcing at a 3–6-month lag. More importantly, most of the retained modes, outside of the equatorial region, have time variations that correlate with El Nino. One ocean mode, with a spatial pattern represen...

An evaluation of expendable bathythermograph and Tropical Atmosphere‐Ocean Array data for monitoring tropical ocean variability

Two important sources of information for monitoring and predicting the El Niño‐Southern Oscillation are the Tropical Atmosphere Ocean (TAO) buoy array and the volunteer observing ship expendable bathythermograph (VOS XBT) network. The subsurface ocean temperature measurements of these two networks are evaluated in the context of analysis and monitoring of medium‐ to low‐frequency variability in the tropical Pacific Ocean. It is shown that both systems capture the principal features that characterize variability in the equatorial central and eastern Pacific Ocean but only TAO can capture the higher temporal fluctuations in detail. In the western Pacific, the VOS XBT network is able to capture the slowly moving, westward propagating Rossby waves and their reflection and interaction with the western boundary. TAO is limited in this respect because of its equatorial focus. The accuracy of temperature maps is estimated using the rms analysis error variance. The accuracy of the VOS XBT network fluctuates in space and time but is relatively steady averaged over the tropical region, while that of TAO has gradually improved as the basin wide array has been implemented. Case studies using VOS XBT data only, TAO data only, and the combined full data set indicate the networks are complementary and supportive, evaluated basin wide and over the tropical region. The high temporal resolution and regularity of the equatorially focused TAO network are complemented by the broad‐scale, irregular tropical VOS XBT sampling in the equatorial region and by VOS coverage outside the domain of TAO. A proxy for net information content is derived from the estimated rms error variance of the analysis. For the equatorial region, TAO now provides in excess of 70% of the information, its dominance beginning in 1992. For the tropical region (20°S–20°N) the net information content of the respective systems is of comparable magnitude, each equivalent to in excess of 100 independent samples per 10‐day period in 1994, reinforcing the notion that both systems are valuable sources of subsurface ocean information for monitoring medium‐ to low‐frequency tropical variability.

An Improved System for Tropical Ocean Subsurface Temperature Analyses

This study demonstrates techniques that lead to improved use of ocean thermal information and more useful and informative products for monitoring variability in the tropical oceans. The method is based on statistical interpolation and is illustrated using analyses for the 20°C isotherm depth over the Pacific and Indian Oceans. A new monthly climatology is derived by exploiting the statistical interpolation method to provide an improved weighted estimate. The new climatology is shown to better represent key aspects of the tropical ocean thermal structure. A statistical forecast based on the previous analysis and climatology significantly improves the analysis product, both in a qualitative sense and as judged by quantitative measures of the skill of the forecast and of the estimated error of the analysis. Both the new climatology and the statistical forecasting scheme are interpreted as strategies for delivering enhanced information to the analysis system. A series of 10-day analyses are presented. It is shown that these analyses retain all the information contained in longer period analyses, at least when used with statistical forecasts, and that in addition they resolve higher-frequency events in the equatorial waveguide. The 10-day analyses have around the same absolute estimated error as the longer period analyses but substantially higher accuracy due to the larger variance of the 10-day field. Some implications of these results are discussed.

Sea ice and oceanic processes on the Ross Sea continental shelf

We have investigated the spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf, in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979–1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86% during winter with little month‐to‐month or interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn. Newly identified Pennell and Ross Passage polynyas near the continental shelf break appear to be maintained in part by divergence above a submarine bank and by upwelling of warmer water near the slope front. Warmer subsurface water enters the shelf region year‐round and will retard ice growth and enhance heat flux to the atmosphere when entrained in the strong winter vertical circulation. Temperatures at 125‐m depth on a mooring near the Ross Ice Shelf during July 1984 averaged 0.15°C above freezing, sufficient to support a vertical heat flux above 100 W/m2. Monthly average subsurface ocean temperatures along the Ross Ice Shelf lag the air temperature cycle and begin to rise several weeks before spring ice breakout. The coarse SMMR resolution and dynamic ice shelf coastlines can compromise the use of microwave sea ice data near continental boundaries.

Atmospheric Boundary Layer and Oceanic Mixed Layer Observations in Hurricane Josephine Obtained from Air-Deployed Drifting Buoys and Research Aircraft

Abstract Three drifting buoys were successfully air-dropped ahead of Hurricane Josephine. This deployment resulted in detailed simultaneous measurements of surface wind speed, surface pressure and subsurface ocean temperature during and subsequent to storm passage. This represents the first time that such a self-consistent data set of surface conditions within a tropical cyclone has been collected. Subsequent NOAA research overflights of the buoys, as part of a hurricane planetary boundary-layer experiment, showed that aircraft wind speeds, extrapolated to the 20 m level, agreed to within ±2 m s−1, pressures agreed to within ±1 mb, and sea-surface temperatures agreed to within ±0.8°C of the buoy values. Ratios of buoy peak 1 min wind (sustained wind) to one-half h mean wind > 1.3 were found to coincide with eyewall and principal rainband features. Buoy trajectories and subsurface temperature measurements revealed the existence of a series of mesoscale eddies in the subtropical front. Buoy data revealed st...

Remote Raman Measurement Techniques

The use of laser Raman measurement techniques in remote sensing applications is surveyed. A feasibility index is defined as a means to characterize the practicality of a given remote Raman measurement application. Specific applications of Raman scattering to the measurement of atmospheric water vapor profiles, methane plumes from liquid natural gas spills, and subsurface ocean temperature profiles are described. This paper will survey the use of laser Raman measurement techniques in remote sensing applications using as examples specific systems that the Computer Genetics Corporation (CGC) group has developed and engineered.