Changes in poleward atmospheric energy transport over a wide range of climates: Energetic and diffusive perspectives and a priori theories

The midlatitude poleward atmospheric energy transport increases in radiatively forced simulations of warmed climates across a range of models from comprehensive coupled general circulation models (GCMs) to idealized aquaplanet moist GCMs to diffusive moist energy balance models. These increases have been rationalized from two perspectives. The energetic (or radiative) perspective takes the atmospheric energy budget and decomposes energy flux changes (radiative forcing, feedbacks, or surface fluxes) to determine the energy transport changes required by the budget. The diffusive perspective takes the net effect of atmospheric macroturbulence to be a diffusive energy transport down-gradient, so a change in transport can arise from changes in mean energy gradients or turbulent diffusivity. Here, we compare these perspectives in idealized moist, gray-radiation GCM simulations over a wide range of climate states. The energetic perspective has a dominant role for radiative forcing in this GCM, with cancellation between the components of the temperature feedback that can account for the GCM's non-monotonic energy transport changes. Comprehensive CMIP5 GCM simulations have similarities in the northern hemisphere to the idealized GCM, though a comprehensive GCM over several CO2 doublings has a distinctly different feedback structure evolution. The diffusive perspective requires a non-constant diffusivity to account for the idealized GCM-simulated changes, with important roles for the eddy velocity, dry static stability, and horizontal energy gradients. Beyond diagnostic analysis, GCM-independent a priori theories for components of the temperature feedback are presented that account for changes without knowledge of a perturbed climate state, suggesting that this is the more parsimonious perspective.

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Mechanisms of delayed monsoon onset with warming

10.5194/egusphere-egu2020-12518 ◽

2020 ◽

Author(s):

Simona Bordoni ◽

Katrina Hui

Keyword(s):

General Circulation ◽

Monsoon Season ◽

Lower Boundary ◽

Warm Season ◽

General Circulation Models ◽

Monsoon Onset ◽

Surface Fluxes ◽

Latent Energy ◽

Atmospheric Energy ◽

Wide Range

Comprehensive general circulation models (GCMs) in the CMIP3/CMIP5 archive project a delay in the timing of monsoon onset, as the climate warms in response to greenhouse gas (GHG) concentration increases. It has been argued that surface latent heat flux, and its differing response to GHG perturbations over land and over ocean, plays an important role in the redistribution of rainfall from early to late in the warm season in monsoon regions. However, similar phase delays in tropical precipitation have been shown to occur even in warming aquaplanet simulations forced by sea surface temperature perturbations. An alternative explanation invokes energetic arguments, in which elevated latent energy demand in the hemisphere warming up seasonally, as dictated by the Clausius&#8211;Clapeyron relation, drives a shift of tropical rainfall towards the opposite hemisphere, manifesting itself as a seasonal delay in the onset of the rainy season.&#160;&#160;In this study, we explore mechanisms of delayed monsoon onset with warming in aquaplanet simulations with an idealized GCM spanning a wide range of climates. In earlier work, we have in fact shown how monsoons with rapid circulation and precipitation changes at the beginning of the warm season can be simulated even without any land-sea contrast, provided that the lower boundary has sufficiently low thermal inertia. As the climate is warmed, we find that the onset of the monsoon is progressively delayed to later pentads in the summer season, in agreement with results from the comprehensive GCMs. However, the end of the monsoon season varies less strongly with climate, resulting in a progressive shortening of the overall monsoon season as the climate is warmed. The atmospheric energy balance is examined to separate possible influences of changes in surface fluxes, atmospheric energy storage and gross moist stability on the circulation's seasonality. Radiative-convective equilibrium experiments with the same GCM are also examined, to explore if and to what extent the delayed monsoon onset can indeed result from increases in the effective heat capacity of the atmospheric column with warming, through changes in its latent energy component.&#160;

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The faint young Sun problem revisited with a 3-D climate–carbon model – Part 1

Climate of the Past ◽

10.5194/cp-10-697-2014 ◽

2014 ◽

Vol 10 (2) ◽

pp. 697-713 ◽

Cited By ~ 5

Author(s):

G. Le Hir ◽

Y. Teitler ◽

F. Fluteau ◽

Y. Donnadieu ◽

P. Philippot

Keyword(s):

Radiative Forcing ◽

General Circulation ◽

Freezing Point ◽

Climatic Factors ◽

General Circulation Models ◽

Companion Paper ◽

One Dimensional ◽

Carbon Dioxide Concentrations ◽

Wide Range ◽

High Concentrations

Abstract. During the Archaean, the Sun's luminosity was 18 to 25% lower than the present day. One-dimensional radiative convective models (RCM) generally infer that high concentrations of greenhouse gases (CO2, CH4) are required to prevent the early Earth's surface temperature from dropping below the freezing point of liquid water and satisfying the faint young Sun paradox (FYSP, an Earth temperature at least as warm as today). Using a one-dimensional (1-D) model, it was proposed in 2010 that the association of a reduced albedo and less reflective clouds may have been responsible for the maintenance of a warm climate during the Archaean without requiring high concentrations of atmospheric CO2 (pCO2). More recently, 3-D climate simulations have been performed using atmospheric general circulation models (AGCM) and Earth system models of intermediate complexity (EMIC). These studies were able to solve the FYSP through a large range of carbon dioxide concentrations, from 0.6 bar with an EMIC to several millibars with AGCMs. To better understand this wide range in pCO2, we investigated the early Earth climate using an atmospheric GCM coupled to a slab ocean. Our simulations include the ice-albedo feedback and specific Archaean climatic factors such as a faster Earth rotation rate, high atmospheric concentrations of CO2 and/or CH4, a reduced continental surface, a saltier ocean, and different cloudiness. We estimated full glaciation thresholds for the early Archaean and quantified positive radiative forcing required to solve the FYSP. We also demonstrated why RCM and EMIC tend to overestimate greenhouse gas concentrations required to avoid full glaciations or solve the FYSP. Carbon cycle–climate interplays and conditions for sustaining pCO2 will be discussed in a companion paper.

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How Asian aerosols impact regional surface temperatures across the globe

10.5194/acp-2020-1029 ◽

2020 ◽

Author(s):

Joonas Merikanto ◽

Kalle Nordling ◽

Petri Räisänen ◽

Jouni Räisänen ◽

Declan O'Donnell ◽

...

Keyword(s):

Surface Temperature ◽

Temperature Effects ◽

Energy Transport ◽

Temperature Response ◽

The Arctic ◽

Anthropogenic Aerosols ◽

Atmospheric Energy ◽

Atmospheric Energy Transport ◽

Temperature Responses ◽

Global Surface

Abstract. South and East Asian anthropogenic aerosols mostly reside in an air mass extending from the Indian Ocean to the North Pacific. Yet the surface temperature effects of Asian aerosols spread across the whole globe. Here, we remove Asian anthropogenic aerosols from two independent climate models (ECHAM6.1 and NorESM1) using the same representation of aerosols via MACv2-SP (a simple plume implementation of the 2nd version of the Max Planck Institute Aerosol Climatology). We then robustly decompose the global distribution of surface temperature responses into contributions from atmospheric energy flux changes. We find that the horizontal atmospheric energy transport strongly moderates the surface temperature response over the regions where Asian aerosols reside. Atmospheric energy transport and changes in clear-sky longwave radiation redistribute the temperature effects efficiently across the Northern hemisphere, and to a lesser extent also over the Southern hemisphere. The model-mean global surface temperature response to Asian anthropogenic aerosol removal is 0.26 ± 0.04 °C (0.22 ± 0.03 for ECHAM6.1 and 0.30 ± 0.03 °C for NorESM1) of warming. Model-to-model differences in global surface temperature response mainly arise from differences in longwave cloud (0.01 ± 0.01 for ECHAM6.1 and 0.05 ± 0.01 °C for NorESM1) and shortwave cloud (0.03 ± 0.03 for ECHAM6.1 and 0.07 ± 0.02 °C for NorESM1) responses. The differences in cloud responses between the models also dominate the differences in regional temperature responses. In both models, the Northern hemispheric surface warming amplifies towards the Arctic, where the total temperature response is highly seasonal and weakest during the Arctic summer. We estimate that under a strong Asian aerosol mitigation policy tied with strong climate mitigation (Shared Socioeconomic Pathway 1-1.9) the Asian aerosol reductions can add around 8 years' worth of current day global warming during the next few decades.

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Energy of Midlatitude Transient Eddies in Idealized Simulations of Changed Climates

Journal of Climate ◽

10.1175/2008jcli2099.1 ◽

2008 ◽

Vol 21 (22) ◽

pp. 5797-5806 ◽

Cited By ~ 72

Author(s):

Paul A. O’Gorman ◽

Tapio Schneider

Keyword(s):

Kinetic Energy ◽

Potential Energy ◽

Radiative Forcing ◽

General Circulation ◽

Thermal Structure ◽

Circulation Model ◽

Static Stability ◽

Eddy Kinetic Energy ◽

Available Potential Energy ◽

Wide Range

Abstract As the climate changes, changes in static stability, meridional temperature gradients, and availability of moisture for latent heat release may exert competing effects on the energy of midlatitude transient eddies. This paper examines how the eddy kinetic energy in midlatitude baroclinic zones responds to changes in radiative forcing in simulations with an idealized moist general circulation model. In a series of simulations in which the optical thickness of the longwave absorber is varied over a wide range, the eddy kinetic energy has a maximum for a climate with mean temperature similar to that of present-day earth, with significantly smaller values both for warmer and for colder climates. In a series of simulations in which the meridional insolation gradient is varied, the eddy kinetic energy increases monotonically with insolation gradient. In both series of simulations, the eddy kinetic energy scales approximately linearly with the dry mean available potential energy averaged over the baroclinic zones. Changes in eddy kinetic energy can therefore be related to the changes in the atmospheric thermal structure that affect the mean available potential energy.

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Using Atmospheric Energy Transport to Quantitatively Constrain South Pacific Convergence Zone Shifts during ENSO

Journal of Climate ◽

10.1175/jcli-d-18-0151.1 ◽

2019 ◽

Vol 32 (6) ◽

pp. 1839-1855 ◽

Cited By ~ 4

Author(s):

Benjamin R. Lintner ◽

William R. Boos

Keyword(s):

Energy Source ◽

Energy Transport ◽

El Nino ◽

South Pacific ◽

Radiative Flux ◽

South Pacific Convergence Zone ◽

Convergence Zone ◽

Atmospheric Energy ◽

Enso Events ◽

Atmospheric Energy Transport

AbstractThe South Pacific convergence zone (SPCZ) exhibits well-known spatial displacements in response to anomalous sea surface temperatures (SSTs) associated with the El Niño–Southern Oscillation (ENSO). Although dynamic and thermodynamic changes during ENSO events are consistent with observed SPCZ shifts, explanations for these displacements have been largely qualitative. This study applies a theoretical framework based on generalizing arguments about the relationship between the zonal-mean intertropical convergence zone (ITCZ) and atmospheric energy transport (AET) to 2D, permitting quantification of SPCZ displacements during ENSO. Using either resolved atmospheric energy fluxes or estimates of column-integrated moist energy sources, this framework predicts well the observed SPCZ shifts during ENSO, at least when anomalous ENSO-region SSTs are relatively small. In large-amplitude ENSO events, such as the 1997/98 El Niño, the framework breaks down because of the large change in SPCZ precipitation intensity. The AET framework permits decomposition of the ENSO forcing into various components, such as column radiative heating versus surface turbulent fluxes, and local versus remote contributions. Column energy source anomalies in the equatorial central and eastern Pacific dominate the SPCZ shift. Furthermore, although the radiative flux anomaly is larger than the surface turbulent flux anomaly in the SPCZ region, the radiative flux anomaly, which can be viewed as a feedback on the ENSO forcing, accounts for slightly less than half of SPCZ precipitation anomalies during ENSO. This study also introduces an idealized analytical model used to illustrate AET anomalies during ENSO and to obtain a scaling for the SPCZ response to an anomalous equatorial energy source.

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Atmospheric Energy Transport Over North America For Three Winter Months

Monthly Weather Review ◽

10.1175/1520-0493(1972)100<0491:aetona>2.3.co;2 ◽

1972 ◽

Vol 100 (6) ◽

pp. 491-502

Author(s):

ELFORD G. ASTLING ◽

LYLE H. HORN

Keyword(s):

North America ◽

Energy Transport ◽

Atmospheric Energy ◽

Atmospheric Energy Transport

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Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport

10.5194/egusphere-egu2020-21344 ◽

2020 ◽

Author(s):

Johanne H. Rydsaa ◽

Rune G. Graversen ◽

Patrick Stoll

Keyword(s):

Energy Transport ◽

Winter Season ◽

Arctic Climate ◽

The Arctic ◽

Synoptic Scale ◽

Near Surface ◽

Latent Energy ◽

Atmospheric Energy ◽

Planetary Scale ◽

Atmospheric Energy Transport

Atmospheric energy transport into the Arctic (>70&#176; N) has been shown to greatly alter the Arctic temperatures and the development of the Arctic weather and climate. Recent research suggests that latent energy transport into the Arctic by large, planetary-scale atmospheric systems cause a stronger and more long-lasting impact on near surface temperatures, than energy transported by smaller, synoptic scale systems. This implies that Rossby waves impact Arctic climate more than synoptic cyclones. Therefore, shifts in circulation patterns driving atmospheric energy transport into the Arctic on different scales have a potential to change Arctic climate.Here, we show that the annual mean impact of latent energy transport on Arctic temperatures is dominated by the winter season transport. Furthermore, by examining the ERA5 dataset for the years 1979-2018, we find that over the past four decades, there has been a shift in the mean winter season latent energy transport, from smaller, synoptic scale systems (-0.03 PW/decade), towards larger, planetary scale systems (+0.05 PW/decade) which as mentioned, have a larger climatic impact. As a consequence, this shift is estimated to have increased the Arctic temperatures. We find that the trends are driven by an increase in the extreme transport events (here we examine the upper 97.5th percentile). The upper extremes have increased more than the average on the planetary scale, and decreased more on the synoptic scale. The decrease in extreme synoptic scale transport at 70&#176; N has been confirmed in other analyses of high vorticity weather systems. By examining the extreme transport events on seasonal scales, we reveal differences in the temporal distribution of planetary vs. synoptic scale extreme events, and identify areas of the Arctic that receive the strongest impact with respect to increases in near-surface temperatures.

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Relative Contributions of Atmospheric Energy Transport and Sea Ice Loss to the Recent Warm Arctic Winter

Journal of Climate ◽

10.1175/jcli-d-17-0157.1 ◽

2017 ◽

Vol 30 (18) ◽

pp. 7441-7450 ◽

Cited By ~ 11

Author(s):

Hye-Mi Kim ◽

Baek-Min Kim

Keyword(s):

Sea Ice ◽

Energy Transport ◽

Open Water ◽

The Arctic ◽

Arctic Warming ◽

Atmospheric Energy ◽

Downward Longwave Radiation ◽

Ice Retreat ◽

Atmospheric Energy Transport ◽

Heat And Moisture

Abstract The relative contributions of atmospheric energy transport (via heat and moisture advection) and sea ice decline to recent Arctic warming were investigated using high-resolution reanalysis data up to 2017. During the Arctic winter, a variation of downward longwave radiation (DLR) is fundamental in modulating Arctic surface temperature. In the warm Arctic winter, DLR and precipitable water (PW) are increasing over the entire Arctic; however, the major drivers for such increases differ regionally. In areas such as the northern Greenland Sea, increasing DLR and PW are caused mainly by convergence of atmospheric energy transport from lower latitudes. In regions of maximum sea ice retreat (e.g., northern Barents–Kara Seas), continued sea ice melting from previous seasons drive the DLR and PW increases, consistent with the positive ice–insulation feedback. Distinct local feedbacks between open water and ice-retreat regions were further compared. In open water regions, a reduced ocean–atmosphere temperature gradient caused by atmospheric warming suppresses surface turbulent heat flux (THF) release from the ocean to the atmosphere; thus, surface warming cannot accelerate. Conversely, in ice-retreat regions, sea ice reduction allows the relatively warm ocean to interact with the colder atmosphere via surface THF release. This increases temperature and humidity in the lower troposphere consistent with the positive ice–insulation feedback. The implication of this study is that Arctic warming will slow as the open water fraction increases. Therefore, given sustained greenhouse warming, the roles of atmospheric heat and moisture transport from lower latitudes are likely to become increasingly critical in the future Arctic climate.

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Tropical Pacific–Driven Decadel Energy Transport Variability

Journal of Climate ◽

10.1175/jcli3389.1 ◽

2005 ◽

Vol 18 (12) ◽

pp. 2037-2051 ◽

Cited By ~ 23

Author(s):

Wilco Hazeleger ◽

Camiel Severijns ◽

Richard Seager ◽

Franco Molteni

Keyword(s):

Heat Transport ◽

Energy Transport ◽

Decadal Variability ◽

Tropical Pacific ◽

Ocean Heat Transport ◽

Atmospheric Energy ◽

The Mean ◽

Atmospheric Energy Transport ◽

Hadley Cells ◽

The Tropical Pacific

Abstract The atmospheric energy transport variability associated with decadal sea surface temperature variability in the tropical Pacific is studied using an atmospheric primitive equation model coupled to a slab mixed layer. The decadal variability is prescribed as an anomalous surface heat flux that represents the reduced ocean heat transport in the tropical Pacific when it is anomalously warm. The atmospheric energy transport increases and compensates for the reduced ocean heat transport. Increased transport by the mean meridional overturning (i.e., the strengthening of the Hadley cells) causes increased poleward energy transport. The subtropical jets increase in strength and shift equatorward, and in the midlatitudes the transients are affected. NCEP–NCAR reanalysis data show that the warming of the tropical Pacific in the 1980s compared to the early 1970s seems to have caused very similar changes in atmospheric energy transport indicating that these atmospheric transport variations were driven from the tropical Pacific. To study the implication of these changes for the coupled climate system an ocean model is driven with winds obtained from the atmosphere model. The poleward ocean heat transport increased when simulated wind anomalies associated with decadal tropical Pacific variability were used, showing a negative feedback between decadal variations in the mean meridional circulation in the atmosphere and in the Pacific Ocean. The Hadley cells and subtropical cells act to stabilize each other on the decadal time scale.

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