A Robust Constraint on the Temperature and Height of the Extratropical Tropopause

Abstract In a recent study, the authors hypothesize that the Clausius–Clapeyron relation provides a strong constraint on the temperature of the extratropical tropopause and hence the depth of mixing by extratropical eddies. The hypothesis is a generalization of the fixed-anvil temperature hypothesis to the global atmospheric circulation. It posits that the depth of robust mixing by extratropical eddies is limited by radiative cooling by water vapor—and hence saturation vapor pressures—in areas of sinking motion. The hypothesis implies that 1) radiative cooling by water vapor constrains the vertical structure and amplitude of extratropical dynamics and 2) the extratropical tropopause should remain at roughly the same temperature and lift under global warming. Here the authors test the hypothesis in numerical simulations run on an aquaplanet general circulation model (GCM) and a coupled atmosphere–ocean GCM (AOGCM). The extratropical cloud-top height, wave driving, and lapse-rate tropopause all shift upward but remain at roughly the same temperature when the aquaplanet GCM is forced by uniform surface warming of +4 K and when the AOGCM is forced by RCP8.5 scenario emissions. “Locking” simulations run on the aquaplanet GCM further reveal that 1) holding the water vapor concentrations input into the radiation code fixed while increasing surface temperatures strongly constrains the rise in the extratropical tropopause, whereas 2) increasing the water vapor concentrations input into the radiation code while holding surface temperatures fixed leads to robust rises in the extratropical tropopause. Together, the results suggest that roughly invariant extratropical tropopause temperatures constitutes an additional “robust response” of the climate system to global warming.

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Observed and Simulated Upper-Tropospheric Water Vapor Feedback

Journal of Climate ◽

10.1175/2007jcli2142.1 ◽

2008 ◽

Vol 21 (13) ◽

pp. 3282-3289 ◽

Cited By ~ 29

Author(s):

A. Gettelman ◽

Q. Fu

Keyword(s):

Water Vapor ◽

General Circulation ◽

Circulation Model ◽

Specific Humidity ◽

Upper Troposphere ◽

Double Peak Structure ◽

Peak Structure ◽

Surface Temperatures ◽

Community Atmosphere Model ◽

Water Vapor Feedback

Abstract Satellite measurements from the Atmospheric Infrared Sounder (AIRS) in the upper troposphere over 4.5 yr are used to assess the covariation of upper-tropospheric humidity and temperature with surface temperatures, which can be used to constrain the upper-tropospheric moistening due to the water vapor feedback. Results are compared to simulations from a general circulation model, the NCAR Community Atmosphere Model (CAM), to see if the model can reproduce the variations. Results indicate that the upper troposphere maintains nearly constant relative humidity for observed perturbations to ocean surface temperatures over the observed period, with increases in temperature ∼1.5 times the changes at the surface, and corresponding increases in water vapor (specific humidity) of 10%–25% °C−1. Increases in water vapor are largest at pressures below 400 hPa, but they have a double peak structure. Simulations reproduce these changes quantitatively and qualitatively. Agreement is best when the model is sorted for satellite sampling thresholds. This indicates that the model reproduces the moistening associated with the observed upper-tropospheric water vapor feedback. The results are not qualitatively sensitive to model resolution or model physics.

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A Gray-Radiation Aquaplanet Moist GCM. Part I: Static Stability and Eddy Scale

Journal of the Atmospheric Sciences ◽

10.1175/jas3753.1 ◽

2006 ◽

Vol 63 (10) ◽

pp. 2548-2566 ◽

Cited By ~ 225

Author(s):

Dargan M. W. Frierson ◽

Isaac M. Held ◽

Pablo Zurita-Gotor

Keyword(s):

Water Vapor ◽

General Circulation ◽

Large Scale ◽

Circulation Model ◽

Companion Paper ◽

Static Stability ◽

Lapse Rate ◽

Surface Boundary ◽

Moist Convection ◽

Control Value

Abstract In this paper, a simplified moist general circulation model is developed and used to study changes in the atmospheric general circulation as the water vapor content of the atmosphere is altered. The key elements of the model physics are gray radiative transfer, in which water vapor and other constituents have no effect on radiative fluxes, a simple diffusive boundary layer with prognostic depth, and a mixed layer aquaplanet surface boundary condition. This GCM can be integrated stably without a convection parameterization, with large-scale condensation only, and this study focuses on this simplest version of the model. These simplifications provide a useful framework in which to focus on the interplay between latent heat release and large-scale dynamics. In this paper, the authors study the role of moisture in determining the tropospheric static stability and midlatitude eddy scale. In a companion paper, the effects of moisture on energy transports by baroclinic eddies are discussed. The authors vary a parameter in the Clausius–Clapeyron relation to control the amount of water in the atmosphere, and consider circulations ranging from the dry limit to 10 times a control value. The typical length scale of midlatitude eddies is found to be remarkably insensitive to the amount of moisture in the atmosphere in this model. The Rhines scale evaluated at the latitude of the maximum eddy kinetic energy fits the model results for the eddy scale well. Moist convection is important in determining the extratropical lapse rate, and the dry stability is significantly increased with increased moisture content.

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Evolution and Trend of the Outgoing Longwave Radiation Spectrum

Journal of Climate ◽

10.1175/2009jcli2874.1 ◽

2009 ◽

Vol 22 (17) ◽

pp. 4637-4651 ◽

Cited By ~ 19

Author(s):

Yi Huang ◽

V. Ramaswamy

Keyword(s):

Water Vapor ◽

Outgoing Longwave Radiation ◽

General Circulation ◽

Circulation Model ◽

Longwave Radiation ◽

Natural Variability ◽

Lapse Rate ◽

Vapor Concentration ◽

Geophysical Fluid Dynamics Laboratory ◽

The Difference

Abstract The variability and change occurring in the outgoing longwave radiation (OLR) spectrum are investigated by using simulations performed with a Geophysical Fluid Dynamics Laboratory coupled atmosphere–ocean–land general circulation model. First, the variability in unforced climate (natural variability) is simulated. Then, the change of OLR spectrum due to forced changes in climate is analyzed for a continuous 25-yr time series and for the difference between two time periods (1860s and 2000s). Spectrally resolved radiances have more pronounced and complex changes than broadband fluxes. In some spectral regions, the radiance change is dominated by just one controlling factor (e.g., the window region and CO2 band center radiances are controlled by surface and stratospheric temperatures, respectively) and well exceeds the natural variability. In some other spectral bands, the radiance change is influenced by multiple and often competing factors (e.g., the water vapor band radiance is influenced by both water vapor concentration and temperature) and, although still detectable against natural variability at certain frequencies, demands stringent requirements (drift less than 0.1 K decade−1 at spectral resolution no less than 1 cm−1) of observational platforms. The difference between clear-sky and all-sky radiances in the forced climate problem offers a measure of the change in the cloud radiative effect, but with a substantive dependence on the temperature lapse rate change. These results demonstrate that accurate and continuous observations of the OLR spectrum provide an advantageous means for monitoring the changes in the climate system and a stringent means for validating climate models.

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An Assessment of the Primary Sources of Spread of Global Warming Estimates from Coupled Atmosphere–Ocean Models

Journal of Climate ◽

10.1175/2008jcli2239.1 ◽

2008 ◽

Vol 21 (19) ◽

pp. 5135-5144 ◽

Cited By ~ 275

Author(s):

Jean-Louis Dufresne ◽

Sandrine Bony

Keyword(s):

Global Warming ◽

Water Vapor ◽

General Circulation ◽

Lapse Rate ◽

Climate Feedback ◽

Ocean Heat Uptake ◽

Feedback Analysis ◽

Cloud Feedbacks ◽

Rate Feedback ◽

Heat Uptake

Abstract Climate feedback analysis constitutes a useful framework for comparing the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transient conditions) and their comparison with the contribution of other processes (e.g., the ocean heat uptake) have not been quantified explicitly. Here these contributions from the classical feedback analysis framework are defined and quantified for an ensemble of 12 third phase of the Coupled Model Intercomparison Project (CMIP3)/Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled atmosphere–ocean GCMs. In transient simulations, the multimodel mean contributions to global warming associated with the combined water vapor–lapse-rate feedback, cloud feedback, and ocean heat uptake are comparable. However, intermodel differences in cloud feedbacks constitute by far the most primary source of spread of both equilibrium and transient climate responses simulated by GCMs. The spread associated with intermodel differences in cloud feedbacks appears to be roughly 3 times larger than that associated either with the combined water vapor–lapse-rate feedback, the ocean heat uptake, or the radiative forcing.

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Separation of Contributions from Radiative Feedbacks to Polar Amplification on an Aquaplanet

Journal of Climate ◽

10.1175/jcli-d-11-00246.1 ◽

2012 ◽

Vol 25 (8) ◽

pp. 3010-3024 ◽

Cited By ~ 28

Author(s):

Peter L. Langen ◽

Rune Grand Graversen ◽

Thorsten Mauritsen

Keyword(s):

Water Vapor ◽

Climate Sensitivity ◽

General Circulation ◽

Surface Albedo ◽

Circulation Model ◽

Lapse Rate ◽

Low Latitude ◽

Polar Amplification ◽

Water Vapor Feedback ◽

The Difference

Abstract When climate is forced by a doubling of CO2, a number of feedback processes are induced, such as changes of water vapor, clouds, and surface albedo. Here the CO2 forcing and concomitant feedbacks are studied individually using a general circulation model coupled to an aquaplanet mixed layer ocean. A technique for fixing the radiative effects of moisture and clouds by reusing these variables from 1 × CO2 and 2 × CO2 equilibrium climates in the model’s radiation code allows for a detailed decomposition of forcings, feedbacks, and responses. The cloud feedback in this model is found to have a weak global average effect and surface albedo feedbacks have been eliminated. As in previous studies, the water vapor feedback is found to approximately double climate sensitivity, but while its radiative effect is strongly amplified at low latitudes, the resulting response displays about the same degree of polar amplification as the full all-feedbacks experiment. In fact, atmospheric energy transports are found to change in a way that yields the same meridional pattern of response as when the water vapor feedback is turned off. The authors conclude that while the water vapor feedback does not in itself lead to polar amplification by increasing the ratio of high- to low-latitude warming, it does double climate sensitivity both at low and high latitudes. A polar amplification induced by other feedbacks in the system, such as the Planck and lapse rate feedbacks here, is thus strengthened in the sense of increasing the difference in high- and low-latitude warming.

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Estimating the Continental Response to Global Warming Using Pattern-Scaled Sea Surface Temperatures and Sea Ice

Journal of Climate ◽

10.1175/jcli-d-16-0032.1 ◽

2016 ◽

Vol 29 (24) ◽

pp. 9125-9139 ◽

Cited By ~ 1

Author(s):

Adeline Bichet ◽

Paul J. Kushner ◽

Lawrence Mudryk

Keyword(s):

Global Warming ◽

Sea Ice ◽

General Circulation ◽

Circulation Model ◽

Tropical Indian Ocean ◽

Sea Surface ◽

Climate Projections ◽

Western Boundary ◽

Sea Ice Concentration ◽

Continental Climate

Abstract Better constraining the continental climate response to anthropogenic forcing is essential to improve climate projections. In this study, pattern scaling is used to extract, from observations, the patterned response of sea surface temperature (SST) and sea ice concentration (SICE) to anthropogenically dominated long-term global warming. The SST response pattern includes a warming of the tropical Indian Ocean, the high northern latitudes, and the western boundary currents. The SICE pattern shows seasonal variations of the main locations of sea ice loss. These SST–SICE response patterns are used to drive an ensemble of an atmospheric general circulation model, the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 5 (CAM5), over the period 1980–2010 along with a standard AMIP ensemble using observed SST—SICE. The simulations enable attribution of a variety of observed trends of continental climate to global warming. On the one hand, the warming trends observed in all seasons across the entire Northern Hemisphere extratropics result from global warming, as does the snow loss observed over the northern midlatitudes and northwestern Eurasia. On the other hand, 1980–2010 precipitation trends observed in winter over North America and in summer over Africa result from the recent decreasing phase of the Pacific decadal oscillation and the recent increasing phase of the Atlantic multidecadal oscillation, respectively, which are not part of the global warming signal. The method holds promise for near-term decadal climate prediction but as currently framed cannot distinguish regional signals associated with oceanic internal variability from aerosol forcing and other sources of short-term forcing.

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Summertime precipitation in Hokkaido and Kyushu, Japan in response to global warming

10.21203/rs.3.rs-286237/v1 ◽

2021 ◽

Author(s):

Daichi Takabatake ◽

Masaru Inatsu

Keyword(s):

Global Warming ◽

Tropical Cyclones ◽

General Circulation ◽

Dynamical Downscaling ◽

Circulation Model ◽

Policy Decision ◽

Moisture Flux ◽

Specific Humidity ◽

Future Climate Change ◽

Moisture Flux Convergence

Abstract We analyzed a large ensemble dataset called the database for Policy Decision Making for Future climate change (d4PDF), which contains 60-km resolution atmospheric general circulation model output and 20-km resolution dynamical downscaling for the Japanese domain. The increase in moisture and precipitation, and their global warming response in June–July–August were described focusing on the differences between Hokkaido and Kyushu. The results suggested that the specific humidity increased almost following the Clausius Clapeyron relation, but the change in stationary circulation suppressed the precipitation increase, except for in western Kyushu. The + 4 K climate in Hokkaido would be as hot and humid as the present climate in Kyushu. The circulation change related to the southward shift of the jet stream and an eastward shift of the Bonin high weakened the moisture flux convergence via a stationary field over central Japan including eastern Kyushu. The transient eddy activity counteracted the increase in humidity, so that the moisture flux convergence and precipitation did not change much over Hokkaido. Because the contribution of tropical cyclones to the total precipitation was at most 10%, the decrease in the number of tropical cyclones did not explain the predicted change in precipitation.

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Development of a secondary organic aerosol formation mechanism: comparison with smog chamber experiments and atmospheric measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-8361-2007 ◽

2007 ◽

Vol 7 (3) ◽

pp. 8361-8393 ◽

Cited By ~ 2

Author(s):

L. E. Olcese ◽

J. E. Penner ◽

S. Sillman

Keyword(s):

New England ◽

Formation Mechanism ◽

General Circulation ◽

Circulation Model ◽

Average Error ◽

Smog Chamber ◽

Vapor Pressures ◽

Aerosol Formation ◽

Atmospheric Measurements ◽

Chamber Measurements

Abstract. A new mechanism to simulate the formation of secondary organic aerosols (SOA) from reactive primary hydrocarbons is presented, together with comparisons with experimental smog chamber results and ambient measurements found in the literature. The SOA formation mechanism is based on an approach using calculated vapor pressures and a selection of species that can partition to the aerosol phase from a gas phase photochemical mechanism. The mechanism has been validated against smog chamber measurements using α-pinene, xylene and toluene as SOA precursors, and has an average error of 17%. Qualitative comparisons with smog chamber measurements using isoprene were also performed. A comparison against SOA production in the TORCH 2003 experiment (atmospheric measurements) had an average error of only 12%. This contrasts with previous efforts, in which it was necessary to increase partition coefficients by a factor of 500 in order to match the observed values. Calculations for rural and urban-influenced regions in the eastern U.S. suggest that most of the SOA is biogenic in origin, mainly originated from isoprene. A 0-dimensional calculation based on the New England Air Quality Study also showed good agreement with measured SOA, with about 40% of the total SOA from anthropogenic precursors. This mechanism can be implemented in a general circulation model (GCM) to estimate global SOA formation under ambient NOx and HOx levels.

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Controls on the water vapor isotopic composition near the surface of tropical oceans and role of boundary layer mixing processes

10.5194/acp-2019-254 ◽

2019 ◽

Author(s):

Camille Risi ◽

Joseph Galewsky ◽

Gilles Reverdin ◽

Florent Brient

Keyword(s):

Water Vapor ◽

Isotopic Composition ◽

General Circulation ◽

Model Simulation ◽

Circulation Model ◽

Sea Surface ◽

Trade Wind ◽

Mixing Processes ◽

Tropical Oceans ◽

Air Mixing

Abstract. Understanding what controls the water vapor isotopic composition of the sub-cloud layer (SCL) over tropical oceans (δD0) is a first step towards understanding the water vapor isotopic composition everywhere in the troposphere. We propose an analytical model to predict δD0 as a function of sea surface conditions, humidity and temperature profiles, and the altitude from which the free tropospheric air originates (zorig). To do so, we extend previous studies by (1) prescribing the shape of δD0 vertical profiles, and (2) linking δD0 to zorig. The model relies on the hypotheses that δD0 profiles are steeper than mixing lines and no clouds are precipitating. We show that δD0 does not depend on the intensity of entrainment, dampening hope that δD0 measurements could help constrain this long-searched quantity. Based on an isotope-enabled general circulation model simulation, we show that δD0 variations are mainly controlled by mid-tropospheric depletion and rain evaporation in ascending regions, and by sea surface temperature and zorig in subsiding regions. When the air mixing into the SCL is lower in altitude, it is moister, and thus it depletes more efficiently the SCL. In turn, could δD0 measurements help estimate zorig and thus discriminate between different mixing processes? Estimates that are accurate enough to be useful would be difficult to achieve in practice, requiring measuring daily δD profiles, and measuring δD0 with an accuracy of 0.1 ‰ and 0.4 ‰ in trade-wind cumulus and strato-cumulus clouds respectively.

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