The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Olivier Pauluis - One of the best experts on this subject based on the ideXlab platform.
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Momentum Balance and Eliassen–Palm Flux on Moist Isentropic Surfaces
Journal of the Atmospheric Sciences, 2016Co-Authors: Ray Yamada, Olivier PauluisAbstract:AbstractPrevious formulations for the zonally averaged momentum budget and Eliassen–Palm (EP) flux diagnostics do not adequately account for moist dynamics, since air parcels are not differentiated by their moisture content when averages are taken. The difficulty in formulating the momentum budget in moist coordinates lies in the fact that they are generally not invertible with height. Here, a conditional-averaging approach is used to derive a weak formulation of the momentum budget and EP flux in terms of a general vertical coordinate that is not assumed to be invertible. The generalized equation reduces to the typical mass-weighted zonal-mean momentum equation for invertible vertical coordinates.The weak formulation is applied here to study the momentum budget on moist Isentropes. Recent studies have shown that the meridional mass transport in the midlatitudes is twice as strong on moist Isentropes as on dry Isentropes. It is shown here that this implies a similar increase in the EP flux between the dry...
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Winter intensification of the moist branch of the circulation in simulations of 21st century climate
Geophysical Research Letters, 2010Co-Authors: Frédéric Laliberté, Olivier PauluisAbstract:[1] In this paper, changes in isentropic circulations associated with global warming in the AlB model outputs for the 20th and 21st centuries are analyzed. The changes in the circulations on dry and moist Isentropes are quantified through the use of three bulk measures of the circulations: mass transport, entropy transport and effective stratification. The circulation on dry Isentropes is expected to weaken due to a reduction of the meridional heat transport and to an increase in stratification. In contrast, the moist branch of the circulation, measured in terms of the difference between the circulations on moist and dry Isentropes, strengthens during the winter months. This intensification is characterized not only by an increase in the eddy latent heat transport but also by an increase in the mass transport. This indicate a larger poleward mass flow of warm moist subtropical air into the stormtracks leading to enhanced moist ascent within baroclinic eddies.
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the global atmospheric circulation in moist isentropic coordinates
Journal of Climate, 2010Co-Authors: Olivier Pauluis, Arnaud Czaja, Robert KortyAbstract:Abstract Differential heating of the earth’s atmosphere drives a global circulation that transports energy from the tropical regions to higher latitudes. Because of the turbulent nature of the flow, any description of a “mean circulation” or “mean parcel trajectories” is tied to the specific averaging method and coordinate system. In this paper, the NCEP–NCAR reanalysis data spanning 1970–2004 are used to compare the mean circulation obtained by averaging the flow on surfaces of constant liquid water potential temperature, or dry Isentropes, and on surfaces of constant equivalent potential temperature, or moist Isentropes. While the two circulations are qualitatively similar, they differ in intensity. In the tropics, the total mass transport on dry Isentropes is larger than the circulation on moist Isentropes. In contrast, in midlatitudes, the total mass transport on moist Isentropes is between 1.5 and 3 times larger than the mass transport on dry Isentropes. It is shown here that the differences between ...
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the global atmospheric circulation on moist Isentropes
Science, 2008Co-Authors: Olivier Pauluis, Arnaud Czaja, Robert KortyAbstract:The global atmospheric circulation transports energy from the equatorial regions to higher latitudes through a poleward flow of high-energy and -entropy parcels and an equatorward flow of air with lower energy and entropy content. Because of its turbulent nature, this circulation can only be described in some averaged sense. Here, we show that the total mass transport by the circulation is twice as large when averaged on moist Isentropes than when averaged on dry Isentropes. The additional mass transport on moist Isentropes corresponds to a poleward flow of warm moist air near Earth's surface that rises into the upper troposphere within mid-latitudes and accounts for up to half of the air in the upper troposphere in polar regions.
Toshiki Iwasaki - One of the best experts on this subject based on the ideXlab platform.
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a set of zonal mean equations in a pressure Isentrope hybrid vertical coordinate
Journal of the Atmospheric Sciences, 1998Co-Authors: Toshiki IwasakiAbstract:Abstract A set of mass-weighted zonal mean equations in a pressure–Isentrope hybrid vertical coordinate is derived. This formulation is able to present the nonacceleration theorem in ageostrophic and finite-amplitude sense.
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A Set of Zonal Mean Equations in a Pressure–Isentrope Hybrid Vertical Coordinate
Journal of the Atmospheric Sciences, 1998Co-Authors: Toshiki IwasakiAbstract:Abstract A set of mass-weighted zonal mean equations in a pressure–Isentrope hybrid vertical coordinate is derived. This formulation is able to present the nonacceleration theorem in ageostrophic and finite-amplitude sense.
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general circulation diagnosis in the pressure Isentrope hybrid vertical coordinate
Journal of the Meteorological Society of Japan, 1992Co-Authors: Toshiki IwasakiAbstract:The mean-meridional circulation and wave-mean flow interactions in the pressure-Isentrope hybrid coordinate (p ) are investigated through an analysis of an annual run of a general circulation model (NCAR CCM1). Special attention is paid to seasonal variations of the circulation and their comparisons between the northern and southern hemispheres
Bruce L. Gary - One of the best experts on this subject based on the ideXlab platform.
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Mesoscale temperature fluctuations in the Southern Hemisphere stratosphere
Atmospheric Chemistry and Physics Discussions, 2008Co-Authors: Bruce L. GaryAbstract:Isentrope surfaces in the Southern Hemisphere stratosphere reveal that air parcels undergo mesoscale temperature fluctuations that depend on latitude and season. The largest temperature fluctuations occur at high latitude winter, whereas the smallest fluctuations occur at high latitude summer. This is the same pattern found for the Northern Hemisphere stratosphere. However, the amplitude of the seasonal dependence in the Southern Hemisphere is only 37% of the Northern Hemisphere's seasonal amplitude.
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Mesoscale temperature fluctuations in the stratosphere
Atmospheric Chemistry and Physics, 2006Co-Authors: Bruce L. GaryAbstract:An airborne instrument that measures altitude temperature profiles is ideally suited for the task of characterizing statistical properties of the vertical displacement of Isentrope surfaces. Prior measurements of temperature fluctuations during level flight could not be used to infer Isentrope altitude variations because lapse rate information was missing. The Microwave Temperature Profiler instrument, which includes lapse rate measurements at flight level as a part of temperature profiles, has been used on hundreds of flights to produce altitude versus ground track cross-sections of potential temperature. These cross-sections show Isentrope altitude variations with a horizontal resolution of ~3 km for a >6 km altitude region. An airborne Isentrope-altitude cross-section (IAC) can be compared with a counterpart IAC generated from synoptic scale data, based on radiosondes and satellite instruments, in order to assess differences between the altitudes of Isentrope surfaces sampled at mesoscale versus synoptic scale. It has been found that the synoptic scale Isentropes fail to capture a significant component of vertical displacement of Isentrope surfaces, especially in the vicinity of jet streams. Under the assumptions that air parcels flow along Isentrope surfaces, and change temperature adiabatically while undergoing altitude displacements, it is possible to compute mesoscale temperature fluctuations that are not present in synoptic scale back trajectory parcel temperature histories. It has been found that the magnitude of the mesoscale component of temperature fluctuations varies with altitude, season, latitude and underlying topography. A model for these dependences is presented, which shows, for example, that mesoscale temperature fluctuations increase with altitude in a systematic way, are greatest over mountainous terrain, and are greater at polar latitudes during winter.
Robert Korty - One of the best experts on this subject based on the ideXlab platform.
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the global atmospheric circulation in moist isentropic coordinates
Journal of Climate, 2010Co-Authors: Olivier Pauluis, Arnaud Czaja, Robert KortyAbstract:Abstract Differential heating of the earth’s atmosphere drives a global circulation that transports energy from the tropical regions to higher latitudes. Because of the turbulent nature of the flow, any description of a “mean circulation” or “mean parcel trajectories” is tied to the specific averaging method and coordinate system. In this paper, the NCEP–NCAR reanalysis data spanning 1970–2004 are used to compare the mean circulation obtained by averaging the flow on surfaces of constant liquid water potential temperature, or dry Isentropes, and on surfaces of constant equivalent potential temperature, or moist Isentropes. While the two circulations are qualitatively similar, they differ in intensity. In the tropics, the total mass transport on dry Isentropes is larger than the circulation on moist Isentropes. In contrast, in midlatitudes, the total mass transport on moist Isentropes is between 1.5 and 3 times larger than the mass transport on dry Isentropes. It is shown here that the differences between ...
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the global atmospheric circulation on moist Isentropes
Science, 2008Co-Authors: Olivier Pauluis, Arnaud Czaja, Robert KortyAbstract:The global atmospheric circulation transports energy from the equatorial regions to higher latitudes through a poleward flow of high-energy and -entropy parcels and an equatorward flow of air with lower energy and entropy content. Because of its turbulent nature, this circulation can only be described in some averaged sense. Here, we show that the total mass transport by the circulation is twice as large when averaged on moist Isentropes than when averaged on dry Isentropes. The additional mass transport on moist Isentropes corresponds to a poleward flow of warm moist air near Earth's surface that rises into the upper troposphere within mid-latitudes and accounts for up to half of the air in the upper troposphere in polar regions.
Gang Chen - One of the best experts on this subject based on the ideXlab platform.
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The Mean Meridional Circulation of the Atmosphere Using the Mass above Isentropes as the Vertical Coordinate
Journal of the Atmospheric Sciences, 2013Co-Authors: Gang ChenAbstract:AbstractThe mean meridional circulation of the atmosphere is presented using the mass (more specifically, the pressure corresponding to the mass) above the Isentrope of interest as the vertical coordinate. In this vertical coordinate, the mass-weighted mean circulation is exactly balanced by entropy sources and sinks with no eddy flux contribution as in the isentropic coordinate, and the coordinate can be readily generalized to the mass above moist Isentropes or other quasi-conservative tracers by construction. The corresponding Eliassen–Palm (EP) flux divergence for the zonal-mean angular momentum is formulated in a hybrid isobaric–isentropic form, extending the conventional transformed Eulerian-mean (TEM) formulation to finite-amplitude nongeostrophic eddies on the sphere. In the small-amplitude limit, the hybrid isobaric–isentropic formulation reduces to the TEM formulation.Applying to the NCEP–U.S. Department of Energy (DOE) Reanalysis 2, the new formulation resolves the deficiency of the conventional...
