A Decomposition of Feedback Contributions to Polar Warming Amplification

2013 ◽  
Vol 26 (18) ◽  
pp. 7023-7043 ◽  
Author(s):  
Patrick C. Taylor ◽  
Ming Cai ◽  
Aixue Hu ◽  
Jerry Meehl ◽  
Warren Washington ◽  
...  
Keyword(s):  
Heat Transport ◽  
Southern Hemisphere ◽  
Global Climate ◽  
Temperature Response ◽  
Longwave Radiation ◽  
Climate Feedback ◽  
Response Analysis ◽  
Ocean Heat Transport ◽  
Climate System Model ◽  
Downward Longwave Radiation

Abstract Polar surface temperatures are expected to warm 2–3 times faster than the global-mean surface temperature: a phenomenon referred to as polar warming amplification. Therefore, understanding the individual process contributions to the polar warming is critical to understanding global climate sensitivity. The Coupled Feedback Response Analysis Method (CFRAM) is applied to decompose the annual- and zonal-mean vertical temperature response within a transient 1% yr−1 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4), into individual radiative and nonradiative climate feedback process contributions. The total transient annual-mean polar warming amplification (amplification factor) at the time of CO2 doubling is +2.12 (2.3) and +0.94 K (1.6) in the Northern and Southern Hemisphere, respectively. Surface albedo feedback is the largest contributor to the annual-mean polar warming amplification accounting for +1.82 and +1.04 K in the Northern and Southern Hemisphere, respectively. Net cloud feedback is found to be the second largest contributor to polar warming amplification (about +0.38 K in both hemispheres) and is driven by the enhanced downward longwave radiation to the surface resulting from increases in low polar water cloud. The external forcing and atmospheric dynamic transport also contribute positively to polar warming amplification: +0.29 and +0.32 K, respectively. Water vapor feedback contributes negatively to polar warming amplification because its induced surface warming is stronger in low latitudes. Ocean heat transport storage and surface turbulent flux feedbacks also contribute negatively to polar warming amplification. Ocean heat transport and storage terms play an important role in reducing the warming over the Southern Ocean and Northern Atlantic Ocean.

scholarly journals Seasonal Variations of Climate Feedbacks in the NCAR CCSM3

2011 ◽  
Vol 24 (13) ◽  
pp. 3433-3444 ◽  
Author(s):  
Patrick C. Taylor ◽  
Robert G. Ellingson ◽  
Ming Cai
Keyword(s):  
Surface Temperature ◽  
Surface Albedo ◽  
Global Climate ◽  
Temperature Response ◽  
Lapse Rate ◽  
Climate Feedback ◽  
Climate Simulation ◽  
Climate Feedbacks ◽  
Climate System Model ◽  
Global Mean

Abstract This study investigates the annual cycle of radiative contributions to global climate feedbacks. A partial radiative perturbation (PRP) technique is used to diagnose monthly radiative perturbations at the top of atmosphere (TOA) due to CO2 forcing; surface temperature response; and water vapor, cloud, lapse rate, and surface albedo feedbacks using NCAR Community Climate System Model, version 3 (CCSM3) output from a Special Report on Emissions Scenarios (SRES) A1B emissions-scenario-forced climate simulation. The seasonal global mean longwave TOA radiative feedback was found to be minimal. However, the global mean shortwave (SW) TOA cloud and surface albedo radiative perturbations exhibit large seasonality. The largest contributions to the negative SW cloud feedback occur during summer in each hemisphere, marking the largest differences with previous results. Results suggest that intermodel spread in climate sensitivity may occur, partially from cloud and surface albedo feedback seasonality differences. Further, links between the climate feedback and surface temperature response seasonality are investigated, showing a strong relationship between the seasonal climate feedback distribution and the seasonal surface temperature response.

Interactions between ocean heat transport and Arctic sea ice

2020 ◽  
Author(s):  
David Docquier ◽  
Ramon Fuentes-Franco ◽  
Klaus Wyser ◽  
Torben Koenigk
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Arctic Sea Ice ◽  
Ocean Heat Transport ◽  
Arctic Sea ◽  
Fast Pace ◽  
Area And Volume

<p>Arctic sea ice has been retreating at fast pace in the last decades, with potential impacts on the weather and climate at mid and high latitudes, as well as the biosphere and society. Sea-ice loss is driven by anthropogenic global warming, atmospheric circulation changes, climate feedbacks, and ocean heat transport. To date, no clear consensus regarding the detailed impact of ocean heat transport on Arctic sea ice exists. Previous observational and modeling studies show that the poleward Atlantic Ocean heat transport and Arctic sea-ice area and volume are generally anti-correlated, suggesting a decrease in sea-ice area and volume with larger ocean heat transport. In turn, the changing sea ice may also affect ocean heat transport, but this effect has been much less studied. Our study explores the two-way interactions between ocean heat transport and Arctic sea ice. We use the EC-Earth global climate model, coupling the atmosphere and ocean, and perform different sensitivity experiments to gain insights into these interactions. The mechanisms by which ocean heat transport and Arctic sea ice interact are analyzed, and compared to observations. This study provides a way to better constrain model projections of Arctic sea ice, based on the relationships between ocean heat transport and Arctic sea ice.</p>

scholarly journals Indoor Daylighting and Thermal Response of a Passive Solar Building to Selective Components of Solar Radiation

Buildings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Ochuko Kelvin Overen ◽  
Edson Leroy Meyer ◽  
Golden Makaka
Keyword(s):  
Relative Humidity ◽  
Solar Radiation ◽  
Air Temperature ◽  
Indoor Air ◽  
Temperature Response ◽  
Longwave Radiation ◽  
Thermal Conditions ◽  
Visible Radiation ◽  
Downward Longwave Radiation ◽  
Passive Solar

Solar radiation provides the most significant natural energy in buildings for space heating and daylighting. Due to atmospheric interference, solar radiation received at the Earth’s surface consists of direct beam and diffuse radiation, where diffuse can be further broken down into longwave and visible radiation. Although each of these components co-occurs, their influence on the indoor visual and thermal conditions of a building differ. This study aims to analyze the influence of the various components of solar radiation on the indoor thermal and daylighting of a passive solar building. Thus, a pyrheliometer, pyranometer, shaded-pyranometer, and pyrgeometer mounted on a SOLYS 2 (Kipp & Zonen, Delft, Netherlands) dual Axis sun tracker, were used to monitor direct, global horizontal, diffuse and downward longwave radiation, respectively. The seasonal indoor air temperature and relative humidity were measured using an HMP 60 temperature relative humidity probe. A Li-210R photometric sensor was used to monitor the indoor illuminance. The summer and winter indoor air temperature, as well as relative humidity, were found to be influenced by diffuse horizontal and global horizontal irradiance, respectively. In summer, the indoor air temperature response to diffuse horizontal irradiance was 0.7 °C/ħW/m2 and 1.1 °C/ħW/m2 to global horizontal irradiance in winter, where ħ is 99.9 W/m2. The indoor daylighting which was found to be above the minimum office visual task recommendation in most countries, but within the useful daylight illuminance range was dominated by direct normal irradiance. A response of 260 lux/ħW/m2 was observed. The findings of the study support the strategic locating of the windows in passive solar design. However, the results show that north-facing clerestory windows without shading device could lead to visual discomfort.

scholarly journals The Role of Ocean Heat Transport in the Global Climate Response to Projected Arctic Sea Ice Loss

2016 ◽  
Vol 29 (19) ◽  
pp. 6841-6859 ◽  
Author(s):  
Robert A. Tomas ◽  
Clara Deser ◽  
Lantao Sun
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
Climate System ◽  
Climate Response ◽  
Ocean Heat Transport ◽  
Dynamic Coupling ◽  
Arctic Sea ◽  
Arctic Sea Ice Loss

Abstract The purpose of this study is to elucidate the individual and combined roles of thermodynamic and dynamic ocean–atmosphere coupling in the equilibrium global climate response to projected Arctic sea ice loss using a suite of experiments conducted with Community Climate System Model, version 4, at 1° latitude–longitude spatial resolution. The results highlight the contrasting spatial structures and partially compensating effects of thermodynamic and dynamic coupling. In combination, thermodynamic and dynamic coupling produce a response pattern that is largely symmetric about the equator, whereas thermodynamic coupling alone yields an antisymmetric response. The latter is characterized by an interhemispheric sea surface temperature (SST) gradient, with maximum warming at high northern latitudes decreasing toward the equator, which displaces the intertropical convergence zone (ITCZ) and Hadley circulation northward. In contrast, the fully coupled response shows enhanced warming at high latitudes of both hemispheres and along the equator; the equatorial warming is driven by anomalous ocean heat transport convergence and is accompanied by a narrow equatorward intensification of the northern and southern branches of the ITCZ. In both cases, the tropical precipitation response to Arctic sea ice loss feeds back onto the atmospheric circulation at midlatitudes via Rossby wave dynamics, highlighting the global interconnectivity of the coupled climate system. This study demonstrates the importance of ocean dynamics in mediating the equilibrium global climate response to Arctic sea ice loss.

The Community Land Model and Its Climate Statistics as a Component of the Community Climate System Model

2006 ◽  
Vol 19 (11) ◽  
pp. 2302-2324 ◽  
Author(s):  
Robert E. Dickinson ◽  
Keith W. Oleson ◽  
Gordon Bonan ◽  
Forrest Hoffman ◽  
Peter Thornton ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Longwave Radiation ◽  
Climate System ◽  
System Model ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Community Land Model ◽  
Spring Runoff ◽  
Downward Longwave Radiation ◽  
Community Climate

Abstract Several multidecadal simulations have been carried out with the new version of the Community Climate System Model (CCSM). This paper reports an analysis of the land component of these simulations. Global annual averages over land appear to be within the uncertainty of observational datasets, but the seasonal cycle over land of temperature and precipitation appears to be too weak. These departures from observations appear to be primarily a consequence of deficiencies in the simulation of the atmospheric model rather than of the land processes. High latitudes of northern winter are biased sufficiently warm to have a significant impact on the simulated value of global land temperature. The precipitation is approximately doubled from what it should be at some locations, and the snowpack and spring runoff are also excessive. The winter precipitation over Tibet is larger than observed. About two-thirds of this precipitation is sublimated during the winter, but what remains still produces a snowpack that is very large compared to that observed with correspondingly excessive spring runoff. A large cold anomaly over the Sahara Desert and Sahel also appears to be a consequence of a large anomaly in downward longwave radiation; low column water vapor appears to be most responsible. The modeled precipitation over the Amazon basin is low compared to that observed, the soil becomes too dry, and the temperature is too warm during the dry season.

Why Tropical Sea Surface Temperature is Insensitive to Ocean Heat Transport Changes

2013 ◽  
Vol 26 (18) ◽  
pp. 6742-6749 ◽  
Author(s):  
Daniel D. B. Koll ◽  
Dorian S. Abbot
Keyword(s):  
Heat Transport ◽  
Climate Models ◽  
Global Climate ◽  
Hadley Circulation ◽  
Global Climate Models ◽  
Sea Surface ◽  
Ocean Heat Transport ◽  
Additional Degree ◽  
Tropical Sea ◽  
Do So

AbstractPrevious studies have shown that increases in poleward ocean heat transport (OHT) do not strongly affect tropical SST. The goal of this paper is to explain this observation. To do so, the authors force two atmospheric global climate models (GCMs) in aquaplanet configuration with a variety of prescribed OHTs. It is found that increased OHT weakens the Hadley circulation, which decreases equatorial cloud cover and shortwave reflection, as well as reduces surface winds and evaporation, which both limit changes in tropical SST. The authors also modify one of the GCMs by alternatively setting the radiative effect of clouds to zero and disabling wind-driven evaporation changes to show that the cloud feedback is more important than the wind–evaporation feedback for maintaining constant equatorial SST as OHT changes. This work highlights the fact that OHT can reduce the meridional SST gradient without affecting tropical SST and could therefore serve as an additional degree of freedom for explaining past warm climates.

scholarly journals Atmospheric Responses and Feedback to the Meridional Ocean Heat Transport in the North Pacific

2017 ◽  
Vol 30 (15) ◽  
pp. 5715-5728 ◽  
Author(s):  
Hiroaki Tatebe ◽  
Masao Kurogi ◽  
Hiroyasu Hasumi
Keyword(s):  
Heat Transport ◽  
North Pacific ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Storm Track ◽  
Ocean Heat Transport ◽  
The North ◽  
The Mean ◽  
The North Pacific

Atmospheric responses and feedback to meridional ocean heat transport (OHT) have been investigated using a global climate model that is interactively connected with a high-resolution regional ocean model embedded in the western North Pacific. Compared with a global climate model without the regional model, the net heat supply into the Kuroshio–Oyashio Extension (KOE) region is increased as a result of the increase of the mean northward ocean heat transport (OHT) by the western boundary currents and mesoscale eddies. Resultant sea surface temperature (SST) rise sharpens the meridional SST gradient and reinforces the cross-frontal difference of the surface heat flux and thereby enhances lower-tropospheric baroclinicity. These changes cause northward deflection and strengthening of the wintertime storm track over the North Pacific, which leads to the Pacific–North American (PNA)-like pattern anticyclonic response of the mean westerly jet. The increase of the eddy northward atmospheric heat flux (AHF) associated with the enhanced storm-track activity is compensated by the decrease of the mean northward AHF. The changes of the atmospheric circulations reduce the mean northward OHT in the eastern North Pacific that compensates the increase of the mean northward OHT in the KOE region. The atmospheric responses, which have once been excited by the SST fronts in the KOE region, stabilize the trans–North Pacific OHT. The modeling results herein suggest that basinwide Bjerknes-like compensation works in air–sea coupled processes for the formation of the climatic mean state in the North Pacific.

scholarly journals Terrestrial water loss at night: global relevance from observations and climate models

2020 ◽  
Vol 24 (2) ◽  
pp. 793-807
Author(s):  
Ryan S. Padrón ◽  
Lukas Gudmundsson ◽  
Dominik Michel ◽  
Sonia I. Seneviratne
Keyword(s):  
Water Loss ◽  
Climate Models ◽  
Water Cycle ◽  
Global Climate ◽  
Longwave Radiation ◽  
Global Climate Models ◽  
Downward Longwave Radiation ◽  
Nocturnal Transpiration ◽  
Terrestrial Water ◽  
Projected Changes

Abstract. Nocturnal water loss (NWL) from the surface into the atmosphere is often overlooked because of the absence of solar radiation to drive evapotranspiration and the measuring difficulties involved. However, growing evidence suggests that NWL – and particularly nocturnal transpiration – represents a considerable fraction of the daily values. Here we provide a global overview of the characteristics of NWL based on latent heat flux estimates from the FLUXNET2015 dataset, as well as from simulations of global climate models. Eddy-covariance measurements at 99 sites indicate that NWL represents 6.3 % of total evapotranspiration on average. There are six sites where NWL is higher than 15 %; these sites comprise mountain forests with considerable NWL during winter that is related to snowy and windy conditions. Higher temperature, vapor pressure deficit, wind speed, soil moisture, and downward longwave radiation are related to higher NWL, although this is not consistent across all of the sites. On the other hand, the global multi-model mean of terrestrial NWL is 7.9 % of the total evapotranspiration. The spread of the model ensemble, however, is greater than 15.8 % over half of the land grid cells. Finally, NWL is projected to increase everywhere with an average of 1.8 %, although with a substantial inter-model spread. Changes in NWL contribute substantially to projected changes in total evapotranspiration. Overall, this study highlights the relevance of water loss during the night and opens avenues to explore its influence on the water cycle and the climate system under present and future conditions.

scholarly journals Spatial Patterns of Modeled Climate Feedback and Contributions to Temperature Response and Polar Amplification

2011 ◽  
Vol 24 (14) ◽  
pp. 3575-3592 ◽  
Author(s):  
Julia A. Crook ◽  
Piers M. Forster ◽  
Nicola Stuber
Keyword(s):  
Heat Transport ◽  
Spatial Patterns ◽  
Temperature Response ◽  
Equilibrium Temperature ◽  
Lapse Rate ◽  
Climate Feedback ◽  
Local Climate ◽  
Polar Amplification ◽  
Forcing Mechanisms ◽  
High Level

Abstract Spatial patterns of local climate feedback and equilibrium partial temperature responses are produced from eight general circulation models with slab oceans forced by doubling carbon dioxide (CO2). The analysis is extended to other forcing mechanisms with the Met Office Hadley Centre slab ocean climate model version 3 (HadSM3). In agreement with previous studies, the greatest intermodel differences are in the tropical cloud feedbacks. However, the greatest intermodel spread in the equilibrium temperature response comes from the water vapor plus lapse rate feedback, not clouds, disagreeing with a previous study. Although the surface albedo feedback contributes most in the annual mean to the greater warming of high latitudes, compared to the tropics (polar amplification), its effect is significantly ameliorated by shortwave cloud feedback. In different seasons the relative importance of the contributions varies considerably, with longwave cloudy-sky feedback and horizontal heat transport plus ocean heat release playing a major role during winter and autumn when polar amplification is greatest. The greatest intermodel spread in annual mean polar amplification is due to variations in horizontal heat transport and shortwave cloud feedback. Spatial patterns of local climate feedback for HadSM3 forced with 2 × CO2, +2% solar, low-level scattering aerosol and high-level absorbing aerosol are more similar than those for different models forced with 2 × CO2. However, the equilibrium temperature response to high-level absorbing aerosol shows considerably enhanced polar amplification compared to the other forcing mechanisms, largely due to differences in horizontal heat transport and water vapor plus lapse rate feedback, with the forcing itself acting to reduce amplification. Such variations in high-latitude response between models and forcing mechanisms make it difficult to infer specific causes of recent Arctic temperature change.

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