SEARCH · Engineering Papers

Results for “ocean-atmosphere”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Nimbus 7 SMMR Derived Seasonal Variations in the Water Vapor, Liquid Water and Surface Winds over the Global Oceans

Monthly mean distributions of water vapor and liquid water contained in a vertical column of the atmosphere and the surface wind speed were derived from Nimbus Scanning Multichannel Microwave Radiometer (SMMR) observations over the global oceans for the period November 1978 to November 1979. The remote sensing techniques used to estimate these parameters from SMMR are presented to reveal the limitations, accuracies, and applicability of the satellite-derived information for climate studies. On a time scale of the order of a month, the distribution of atmospheric water vapor over the oceans is controlled by the sea surface temperature and the large scale atmospheric circulation. The monthly mean distribution of liquid water content in the atmosphere over the oceans closely reflects the precipitation patterns associated with the convectively and baroclinically active regions. Together with the remotely sensed surface wind speed that is causing the sea surface stress, the data collected reveal the manner in which the ocean-atmosphere system is operating. Prominent differences in the water vapor patterns from one year to the next, or from month to month, are associated with anomalies in the wind and geopotential height fields. In association with such circulation anomalies the precipitation patterns deduced from the meteorological network over adjacent continents also reveal anomalous distributions.

Prabhakara, C.↗

NASA NTRS1984

Changes in the High-latitude Ocean as Possible Causes of Atmospheric CO2 Variations

Measurements on air enclosed in old polar ice have indicated that the atmospheric CO2 concentration was ca. 50 to 70 ppm lower in late glacial times than during the Holocene. Similar measurements performed on samples from a Greenland ice core, dating ca. 30,000 to 40,000 B.P., and have yielded evidence of several CO2 oscillations with an amplitude of ca. 50 ppm. Each change lasted on the order of a few centuries. A mechanism by which circulation changes in the high-latitude ocean could lead to rapid variations in atmospheric CO2 is proposed. In the Antarctic Ocean a slowing down of the vertical mixing would imply a smaller upward flux of sigma CO2 and nutrients. Assuming constant productivity, sigma CO2 and nutrients would be more completely used which would imply lower CO2 in these high-latitude surface waters. In areas with a warm surface, a slowing down of the circulation would not have a direct impact on CO2 because productivity would automatically decrease by the same factor as the upwelling rate of nutrients. Studies with a simple box model of the ocean-atmosphere system suggest that a suddent decrease by a factor of 2 of the water exchange between the surface and deep sea in high latitudes could lead to a CO2 decrease of ca. 40 to 50 ppm with a time constant of ca. 200 years. Deep-sea sediment studies indicate rapid changes in the high-latitude surface conditions of the North Atlantic and the Antarctic Oceans at the end of the last glaciation. Studies of carbon isotope ratios should help ascertain whether this proposed mechanism was indeed responsible for the CO2 variation.

Siegenthaler, U.↗

NASA NTRS1984

Satellite derived atmosphere water vapor as a tracer of large scale interactions between the atmosphere and ocean

Two water-vapor distributions and the accompanying circulation patterns which occurred over the North and South Atlantic Ocean during February 1979 are described. It is shown that scanning multichannel microwave radiometer observations from the Nimbus-7 satellite are used to remotely sense the vertically integrated atmospheric water vapor and liquid water, and the surface wind speed over the ocean and that they provide information on the ocean-atmosphere interaction. To provide evidence of the events revealed in the satellite observations, FGGE data are used.

Short, D. A.↗

NASA NTRS1986

The 40-50 day oscillation and the El Nino/Southern Oscillation - A new perspective

The tropical ocean-atmosphere exhibits two prominent modes of low-frequency oscillations, i.e., the '40-50' day oscillation and the El Nino/Southern Oscillation (ENSO). The two phenomena are viewed in the same perspective from 10 years of satellite-derived out-going-longwave-radiation data. Results reveal some interesting features that may lead to new insights into the understanding of the two phenomena.

Lau, K. M.↗

NASA NTRS1986

Experimental forecasts of El Nino

A deterministic numerical model of the coupled evolution of the tropical ocean and atmosphere was used to forecast all El Nino/Southern Oscillation (ENSO) events from 1970 to 1986. More particularly, the model, originally developed for studying large-scale ocean-atmosphere interactions in the tropics, successfully predicted the characteristics of the spatial and temporal structure of ENSO observed in the study interval. The model indicated that rainfall moving eastward over the Pacific slackens the surface winds that would otherwise cool the eastern Pacific by drawing up cooler subsurface waters. The oceanic thermocline increases, a poleward flow of westerly flowing warn waters deplets the equatorial warm water reservoir, and sea surface temperatures decline. These ENSO conditions are statistically tractable with the model several months in advance, provided upper ocean layer thermal data are available.

Cane, M. A.↗

NASA NTRS1986

Evaluation of geophysical parameters measured by the Nimbus-7 microwave radiometer for the TOGA Heat Exchange Project

The data distributed by the National Space Science Data Center on the Geophysical parameters of precipitable water, sea surface temperature, and surface-level wind speed, measured by the Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7, are evaluated with in situ measurements between Jan. 1980 and Oct. 1983 over the tropical oceans. In tracking annual cycles and the 1982-83 E1 Nino/Southern Oscillation episode, the radiometer measurements are coherent with sea surface temperatures and surface-level wind speeds measured at equatorial buoys and with precipitable water derived from radiosonde soundings at tropical island stations. However, there are differences between SMMR and in situ measurements. Corrections based on radiosonde and ship data were derived supplementing correction formulae suggested in the databook. This study is the initial evaluation of the data for quantitative description of the 1982-83 E1 Nino/Southern Oscillation episode. It paves the way for determination of the ocean-atmosphere moisture and latent heat exchanges, a priority of the Tropical Ocean and Global Atmosphere (TOGA) Heat Exchange Program.

Liu, W. Timothy↗

NASA NTRS1988

Moisture and latent heat flux variabilities in the tropical Pacific derived from satellite data

This paper describes a method of determining latent heat flux and the ocean-atmosphere moisture from sea surface temperature, precipitable water, and surface wind speed data derived from 1980-1983 observations of SMMR aboard Nimbus 7 above tropical Pacific. The observation period included a very intense El Nino-Southern Oscillation (ENSO) episode. It was found that, during the early phase of the 1982-1983 ENSO, a surface convergence center moved east leading the anomalous equatorial westerlies. At this center, the low wind and high humidity caused negative (low) latent heat flux anomalies, despite anomalously high sea surface temperatures. Latent heat flux was found to play an important role in the seasonal cooling of the upper ocean, except in areas covered by major surface convergence zones and in areas of ocean upwelling.

Liu, W. Timothy↗

NASA NTRS1988

On the dynamics of intraseasonal oscillations and ENSO

This paper investigates some basic properties of low-frequency phenomena in the tropical atmosphere and the coupled ocean-atmosphere system, with an aim of seeking a unified dynamical framework for studies of the mechanisms of intraseasonal oscillations and the El Nino Southern Oscillation (ENSO). The role of specific processes leading to intraseasonal oscillations and to ENSO, both separately and collectively, are considered, using a simple shallow-water system. The results demonstrated the effect of including a time-dependent moist atmosphere in studies of the coupled atmosphere-ocean system. It is suggested that the interaction of several atmospheric processes and oceanic processes through evaporation-SST feedback and wind stress at the atmosphere-ocean interface may be important for the onset and evolution of an ENSO event.

Lau, K.-M.↗

NASA NTRS1988

Abrupt climate change and extinction events

There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

Crowley, Thomas J.↗

NASA NTRS1988

Principal components of the North American summer temperature field and the antecedent oceanic and atmospheric conditions

The North American summer temperature field is evaluated in terms of the preceding patterns of the ocean and atmosphere. It is found that the planetary scale circulation associated with the thermal field over the western tropical Pacific and the ocean-atmosphere interaction over the central North Pacific-Aleutian region are important in determining the summer surface temperature pattern over North America. Also, evidence is presented for the possible impact of the El Nino-Southern Oscillation on the summer circulation pattern. It is suggested that by using the principal components, the predictability of regional circulation can be evaluated as a linear combination of independent sources of variability.

Park, Chung-Kyu↗

NASA NTRS1990

Comparative climatology of four marine stratocumulus regimes

The climatology of marine stratocumulus (MSc) cloud regimes off the west coasts of California, Peru, Morocco, and Angola are examined. Long-term, annual averages are presented for several quantities of interest in the four MSc regimes. The climatologies were constructed using the Comprehensive Ocean-Atmosphere Data Set (COADS). A 40 year time series of observations was extracted for 32 x 32 deg analysis domains. The data were taken from the monthly-averaged, 2 deg product. The resolution of the analysis is therefore limited to scales of greater than 200 km with submonthly variability not resolved. The averages of total cloud cover, sea surface temperature, and surface pressure are presented.

Hanson, Howard P.↗

NASA NTRS1990

The effects of cloud radiative forcing on an ocean-covered planet

Cumulus anvil clouds, whose importance has been emphasized by observationalists in recent years, exert a very powerful influence on deep tropical convection by tending to radiatively destabilize the troposphere. In addition, they radiatively warm the column in which they reside. Their strong influence on the simulated climate argues for a much more refined parameterization in the General Circulation Model (GCM). For Seaworld, the atmospheric cloud radiative forcing (ACRF) has a powerful influence on such basic climate parameters as the strength of the Hadley circulation, the existence of a single narrow InterTropical Convergence Zone (ITCZ), and the precipitable water content of the atmosphere. It seems likely, however, that in the real world the surface CRF feeds back negatively to suppress moist convection and the associated cloudiness, and so tends to counteract the effects of the ACRF. Many current climate models have fixed sea surface temperatures but variable land-surface temperatures. The tropical circulations of such models may experience a position feedback due to ACRF over the oceans, and a negative or weak feedback due to surface CRF over the land. The overall effects of the CRF on the climate system can only be firmly established through much further analysis, which can benefit greatly from the use of a coupled ocean-atmospheric model.

Randall, David A.↗

NASA NTRS1991

The role of global cloud climatologies in validating numerical models

Reliable estimates of the components of the surface radiation budget are important in studies of ocean-atmosphere interaction, land-atmosphere interaction, ocean circulation and in the validation of radiation schemes used in climate models. The methods currently under consideration must necessarily make certain assumptions regarding both the presence of clouds and their vertical extent. Because of the uncertainties in assumed cloudiness, all these methods involve perhaps unacceptable uncertainties. Here, a theoretical framework that avoids the explicit computation of cloud fraction and the location of cloud base in estimating the surface longwave radiation is presented. Estimates of the global surface downward fluxes and the oceanic surface net upward fluxes were made for four months (April, July, October and January) in 1985 to 1986. These estimates are based on a relationship between cloud radiative forcing at the top of the atmosphere and the surface obtained from a general circulation model. The radiation code is the version used in the UCLA/GLA general circulation model (GCM). The longwave cloud radiative forcing at the top of the atmosphere as obtained from Earth Radiation Budget Experiment (ERBE) measurements is used to compute the forcing at the surface by means of the GCM-derived relationship. This, along with clear-sky fluxes from the computations, yield maps of the downward longwave fluxes and net upward longwave fluxes at the surface. The calculated results are discussed and analyzed. The results are consistent with current meteorological knowledge and explainable on the basis of previous theoretical and observational works; therefore, it can be concluded that this method is applicable as one of the ways to obtain the surface longwave radiation fields from currently available satellite data.

HARSHVARDHAN↗

NASA NTRS1990

Oceanic heat content variability in the Tropical Pacific during the 1982-1983 El Nino

A linear, multimode model forced by observed winds is used to investigate anomolous heat transport and storage during the 1982-1983 El Nino. The study compliments the work of Wyrtki (1985) and of Zebiak and Cane (1987) and contains the ocean dynamics invoked by both these studies to explain heat content anomalies. Model hindcasts are compared with observational evidence derived from the island sea level network. The meridional distribution of heat storage and the components of heat transport are considered. It is found that the mechanisms contributing to heat transport out of bands of latitude symmetric about the equator are isolated and related to the wind anomalies and wave dynamics usually associated with ENSO events. It is noted that although the spatial and temporal distribution of oceanic heat anomalies necessary to initiate an ENSO event can be determined only by studying coupled ocean-atmosphere models, an examination of the oceanic component alone is useful in determining constraints imposed by ocean dynamics.

Springer, Scott R.↗

NASA NTRS1991

Nonlinear dynamics and predictability in the atmospheric sciences

Systematic applications of nonlinear dynamics to studies of the atmosphere and climate are reviewed for the period 1987-1990. Problems discussed include paleoclimatic applications, low-frequency atmospheric variability, and interannual variability of the ocean-atmosphere system. Emphasis is placed on applications of the successive bifurcation approach and the ergodic theory of dynamical systems to understanding and prediction of intraseasonal, interannual, and Quaternary climate changes.

Ghil, M.↗

NASA NTRS1992

A global monthly sea surface temperature climatology

The paper presents a new global 2 deg x 2 deg monthly sea surface temperature (SST) climatology, referred here to as the Shea-Trenberth-Reynolds (STR) climatology, which was derived by modifying a 1950-1979-based SST climatology from the Climate Analysis Center (CAC), by using data from the Comprehensive Ocean-Atmosphere Data Set to improve the SST estimates in the regions of the Kuroshio and the Gulf Stream. A comparison of the STR climatology with the Alexander and Mobley SST climatology showed that the STR climatology is warmer in the Northern Hemisphere, and colder poleward of 45 deg S.

Shea, Dennis J.↗

NASA NTRS1992

The influence of the Alaskan Gyre on the coastal circulation in the Gulf of Alaska

The circulation of the northeast Pacific Ocean and the Gulf of Alaska is simulated by means of a reduced-gravity wind-driven model to study seasonal and interannual flow variability. The circulation in the NE Pacific is discussed emphasizing its ramifications for the physical domain, equations, and boundary conditions of the numerical model. The pseudostress fields used to drive the model are based on 20 years of data from the Comprehensive Ocean-Atmosphere Data Set and are analyzed with empirical orthogonal function analysis. The monthly stresses from 1986-89 are used to drive the model, and regional oceanographic features are reproduced including the Alaskan Gyre, Coastal Current, the Sitka eddy, and a severe cyclonic eddy. Comparisons with experimental data show that the high-resolution baroclinic model is valid and demonstrates the applicability of reduced-gravity models.

Heim, Paul K., II↗

NASA NTRS1992

An analysis of the relationship between cloud anomalies and sea surface temperature anomalies in a global circulation model

The relationship between the sea surface temperature anomalies (SSTAs) and the anomalies of the monthly mean cloud cover (including the high-level, low-level, and total cloud cover), the outgoing longwave radiation, and the reflected solar radiation was analyzed using a least absolute deviations regression at each grid point over the open ocean for a 6-yr period. The results indicate that cloud change in association with a local 1-C increase in SSTAs cannot be used to predict clouds in a potential future world where all the oceans are 1-C warmer than at present, because much of the observed cloud changes are due to circulation changes, which in turn are related not only to changes in SSTAs but to changes in SSTA gradients. However, because SSTAs are associated with changes in the local ocean-atmosphere moisture and heat fluxes as well as significant changes in circulation (such as ENSO), SSTAs can serve as a surrogate for many aspects of global climate change.

Peterson, Thomas C.↗