scholarly journals Does feedback temperature dependence influence the slow mode of the climate response?

2021 ◽  
Author(s):  
Tim Rohrschneider ◽  
Jonah Bloch-Johnson ◽  
Maria Rugenstein
Keyword(s):  
Climate Change ◽  
Heat Capacity ◽  
Temperature Dependence ◽  
Temperature Response ◽  
Time Dependent ◽  
Slow Mode ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Multiple Timescale

Abstract. Atmosphere-Ocean General Circulation models (AOGCMs) are a necessary tool to understand climate dynamics on centennial timescales for which observations are scarce. We explore to which degree the temperature dependence of the climate radiative feedback influences the slow mode of the surface temperature response. We question whether long-term climate change is described by a single e-folding mode with a constant timescale which is commonly assumed to be independent of temperature or forcing and the evolution of time. To do so, we analyze AOGCM simulations which have an integration time of 1000 years and are forced by atmospheric CO2 concentrations ranging from 2 times (2X) to 8 times (8X) the preindustrial level. Our findings suggest that feedback temperature dependence strongly influences the equilibrium temperature response and adjustment timescale of the slow mode. The magnitude and timescale of the slow mode is approximately reproduced by a zero-dimensional energy balance model that has a constant effective heat capacity and incorporates a background feedback parameter and a coefficient for feedback temperature dependence. However, the effective heat capacity of the slow mode increases over time, which makes the adjustment timescale also time-dependent. The time-varying adjustment timescale can be approximated by a multiple timescale structure of the slow temperature response, or vice versa, a multiple timescale structure of the slow temperature response is described by a time-dependent timescale. The state-dependence and time-dependence of the adjustment timescale of long-term climate change puts into question common eigenmode decomposition with a fast and a slow timescale in the sense that the slow mode is not well described by a single linear e-folding mode with a constant timescale. We find that such an eigenmode decomposition is valid at a certain forcing level only, and an additional mode or a multiple mode and timescale structure of the slow adjustment is necessary to reproduce the details of AOGCM simulated long-term climate change.

scholarly journals Projected Changes in the Seasonal Cycle of Surface Temperature

2012 ◽  
Vol 25 (18) ◽  
pp. 6359-6374 ◽  
Author(s):  
John G. Dwyer ◽  
Michela Biasutti ◽  
Adam H. Sobel
Keyword(s):  
Heat Capacity ◽  
Sea Ice ◽  
Surface Temperature ◽  
Seasonal Cycle ◽  
Phase Delay ◽  
First Century ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Twenty First Century ◽  
Global Mean

Abstract When forced with increasing greenhouse gases, global climate models project a delay in the phase and a reduction in the amplitude of the seasonal cycle of surface temperature, expressed as later minimum and maximum annual temperatures and greater warming in winter than in summer. Most of the global mean changes come from the high latitudes, especially over the ocean. All 24 Coupled Model Intercomparison Project phase 3 models agree on these changes and, over the twenty-first century, average a phase delay of 5 days and an amplitude decrease of 5% for the global mean ocean surface temperature. Evidence is provided that the changes are mainly driven by sea ice loss: as sea ice melts during the twenty-first century, the previously unexposed open ocean increases the effective heat capacity of the surface layer, slowing and damping the temperature response. From the tropics to the midlatitudes, changes in phase and amplitude are smaller and less spatially uniform than near the poles but are still prevalent in the models. These regions experience a small phase delay but an amplitude increase of the surface temperature cycle, a combination that is inconsistent with changes to the effective heat capacity of the system. The authors propose that changes in this region are controlled by changes in surface heat fluxes.

Effect of Brownian Motion and External Magnetic Field on the Effective Heat Capacity of Ferrofluids

2011 ◽  
Author(s):  
Narges Susan Mousavi Kh. ◽  
Sunil Kumar ◽  
Arvind Narayanaswamy
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Brownian Motion ◽  
Energy Equation ◽  
Volume Fraction ◽  
Physical Parameters ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Negligible Contribution

An Eulerian formalism is used to derive the energy equation for a system of magnetic nanoparticles in a fluid (ferrofluid) in the presence of uniform magnetic field. The energy equation proposed here contains an effective heat capacity, which has contributions from: (1) Brownian motion of nanoparticles, (2) magnetic field, (3) temperature, and (4) volume fraction of particles. The modified term quantitatively shows the negligible contribution of the first three factors but the significant effect of concentration of particles in change in heat capacity of ferrofluid. In order to have a better understanding of the problem, the equation is converted to a non dimensional form from which the role of each of physical parameters can be inferred.

scholarly journals On the Role of Radiative Processes in Stratosphere–Troposphere Coupling

2009 ◽  
Vol 22 (15) ◽  
pp. 4154-4161 ◽  
Author(s):  
Kevin M. Grise ◽  
David W. J. Thompson ◽  
Piers M. Forster
Keyword(s):  
Climate Change ◽  
Temperature Response ◽  
Longwave Radiation ◽  
Tropospheric Temperature ◽  
Radiative Processes ◽  
Ozone Trends ◽  
Radiation Induced ◽  
Polar Stratosphere

Abstract Climate change in the Southern Hemisphere (SH) polar stratosphere is associated with substantial changes in the atmospheric circulation that extend to the earth’s surface. The mechanisms that drive the changes in the SH troposphere are not fully understood, but most previous hypotheses have focused on the role of atmospheric dynamics rather than that of radiation. This study quantifies the radiative response of temperatures in the SH polar troposphere to the forcing from long-term temperature and ozone trends in the SH polar stratosphere. A novel methodology is employed that explicitly neglects changes in tropospheric dynamics and hence isolates the component of the tropospheric temperature response that is radiatively driven by the overlying stratospheric trends. The results reveal that both the amplitude and seasonality of the observed cooling of the middle and upper SH polar troposphere over the past few decades are consistent with a reduction in downwelling longwave radiation induced by cooling in the SH polar stratosphere. The results are compared with analogous calculations for trends in the Northern Hemisphere (NH) polar stratosphere. Both the observations and radiative calculations imply that the comparatively weak trends in the NH polar stratosphere have not played a central role in driving NH tropospheric climate change. Overall, the results suggest that radiative processes play a key role in coupling the large trends in SH polar stratospheric temperatures to tropospheric levels. The tropospheric radiative temperature response documented here could be important for triggering the changes in internal tropospheric dynamics associated with stratosphere–troposphere coupling.

scholarly journals Temperature of a Temperate Glacier

1972 ◽  
Vol 11 (61) ◽  
pp. 15-29 ◽  
Author(s):  
W. D. Harrison
Keyword(s):  
Heat Capacity ◽  
Pure Water ◽  
Equilibrium Temperature ◽  
Water Soluble ◽  
Ice Thickness ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Glacier Ice ◽  
Dominant Process ◽  
Definition Of

AbstractThe closure of water-filled glacier bore holes is considered and it is concluded that freezing due to conduction to the surrounding ice is usually the dominant process. On this basis englacial temperatures are obtained from a bore hole near the equilibrium line of Blue Glacier, U.S.A., where the ice thickness is about 125 m. Temperatures range from −0.03° C near the surface to −0.13° C at a depth of 105 m, with an estimated uncertainty of 0.02 or 0.03 deg. On the average the temperature is about 0.05 deg colder than the equilibrium temperature of ice and pure water. It is shown that at this temperature small amounts of water-soluble impurities play an important role in the thermal behavior of the ice. This leads to a new definition of temperate ice in terms of its effective heat capacity. The effective heat capacity of the Blue Glacier ice is apparently much larger than that of pure ice at the same temperature.

scholarly journals Seasonality in Arctic Warming Driven By Sea Ice Effective Heat Capacity

2021 ◽  
pp. 1-44
Keyword(s):  
Heat Capacity ◽  
Sea Ice ◽  
Seasonal Pattern ◽  
Surface Heat ◽  
Lapse Rate ◽  
Effective Surface ◽  
Effective Heat Capacity ◽  
Arctic Warming ◽  
Rate Feedback ◽  
Effective Heat

Abstract Arctic surface warming under greenhouse gas forcing peaks in winter and reaches its minimum during summer in both observations and model projections. Many mechanisms have been proposed to explain this seasonal asymmetry, but disentangling these processes remains a challenge in the interpretation of general circulation model (GCM) experiments. To isolate these mechanisms, we use an idealized single-column sea ice model (SCM) which captures the seasonal pattern of Arctic warming. SCM experiments demonstrate that as sea ice melts and exposes open ocean, the accompanying increase in effective surface heat capacity can alone produce the observed pattern of peak warming in early winter (shifting to late winter under increased forcing) by slowing the seasonal heating rate, thus delaying the phase and reducing the amplitude of the seasonal cycle of surface temperature. To investigate warming seasonality in more complex models, we perform GCM experiments that individually isolate sea-ice albedo and thermodynamic effects under CO2 forcing. These also show a key role for the effective heat capacity of sea ice in promoting seasonal asymmetry through suppressing summer warming, in addition to precluding summer climatological inversions and a positive summer lapse-rate feedback. Peak winter warming in GCM experiments is further supported by a positive winter lapse-rate feedback, due to cold initial surface temperatures and strong surface-trapped warming that are enabled by the albedo effects of sea ice alone. While many factors contribute to the seasonal pattern of Arctic warming, these results highlight changes in effective surface heat capacity as a central mechanism supporting this seasonality.

Thermal Modeling Solid-Liquid Phase Change Materials (PCMs)

2013 ◽  
Vol 746 ◽  
pp. 161-166
Author(s):  
Tao Hu ◽  
Yan Li ◽  
Duo Su ◽  
Hai Xia Lv
Keyword(s):  
Heat Capacity ◽  
Phase Change ◽  
Temperature Control ◽  
Phase Change Materials ◽  
Thermal Modeling ◽  
Effective Heat Capacity ◽  
Apparent Heat Capacity ◽  
Effective Heat ◽  
Solid Liquid ◽  
Capacity Method

Three thermal modeling methods for phase change materials (PCMs): enthalpy-based method, effective heat capacity method and apparent heat capacity method, are presented in details. Their characteristics and application limitations are compared and discussed. We found that enthalpy-based method and effective heat capacity method are both approximation treatments, and can be well used in steady state problems, while apparent heat capacity method tracks the moving phase change boundary in PCMs, and it is the most accurate and applicable method of the three for dealing with transient processes. This work might provide useful information for the study of using PCMs in temperature control field, especially in aircraft environmental temperature control and thermal management.

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