scholarly journals A Dynamical Perspective on Atmospheric Temperature Variability and Its Response to Climate Change

2019 ◽  
Vol 32 (6) ◽  
pp. 1707-1724 ◽  
Author(s):  
Talia Tamarin-Brodsky ◽  
Kevin Hodges ◽  
Brian J. Hoskins ◽  
Theodore G. Shepherd
Keyword(s):  
Temperature Distribution ◽  
Spatial Structure ◽  
Surface Temperature ◽  
Southern Hemisphere ◽  
Atmospheric Temperature ◽  
Storm Tracks ◽  
Near Surface ◽  
Temperature Anomalies ◽  
Poleward Shift ◽  
Meridional Advection

Abstract The atmospheric temperature distribution is typically described by its mean and variance, while higher-order moments, such as skewness, have received less attention. Skewness is a measure of the asymmetry between the positive and negative tails of the distribution, which has implications for extremes. It was recently shown that near-surface temperature in the Southern Hemisphere is positively skewed on the poleward side of the storm tracks and negatively skewed on the equatorward side. Here we take a dynamical approach to further study what controls the spatial structure of the near-surface temperature distribution in this region. We employ a tracking algorithm to study the formation, intensity, and movement of warm and cold temperature anomalies. We show that warm anomalies are generated on the equatorward side of the storm tracks and propagate poleward, while cold anomalies are generated on the poleward side and propagate equatorward. We further show that while the perturbation growth is mainly achieved through linear meridional advection, it is the nonlinear meridional advection that is responsible for the meridional movement of the temperature anomalies and therefore to the differential skewness. The projected poleward shift and increase of the temperature variance maximum in the Southern Hemisphere under global warming is shown to be composed of a poleward shift and increase in the maximum intensity of both warm and cold anomalies, and a decrease in their meridional displacements. An analytic expression is derived for the nonlinear meridional temperature tendency, which captures the spatial structure of the skewness and its projected changes.

scholarly journals A Pilot Climate Sensitivity Study Using the CEN Coupled Adjoint Model (CESAM)

2018 ◽  
Vol 31 (5) ◽  
pp. 2031-2056 ◽  
Author(s):  
D. Stammer ◽  
A. Köhl ◽  
A. Vlasenko ◽  
I. Matei ◽  
F. Lunkeit ◽  
...  
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Climate Sensitivity ◽  
North Atlantic ◽  
Sensitivity Study ◽  
Northern Europe ◽  
Surface Salinity ◽  
Near Surface ◽  
Temperature Anomalies ◽  
Northern European

A pilot coupled climate sensitivity study is presented based on the newly developed adjoint coupled climate model, Centrum für Erdsystemforschung und Nachhaltigkeit (CEN) Earth System Assimilation Model (CESAM). To this end the components of the coupled forward model are summarized, and the generation of the adjoint code out of the model forward code through the application of the Transformation of Algorithms in FORTRAN (TAF) adjoint compiler is discussed. It is shown that simulations of the intermediate-complexity CESAM are comparable in quality to CMIP-type coupled climate models, justifying the usage of the model to compute adjoint sensitivities of the northern Europe near-surface temperature to anomalies in surface temperature, sea surface salinity, and sea ice over the North Atlantic and the Arctic on time scales of up to one month. Results confirm that on a time scale of up to a few days surface temperatures over northern Europe are influenced by Atlantic temperature anomalies just upstream of the target location. With increasingly longer time lapse, however, it is the influence of SSTs over the central and western North Atlantic on the overlying atmosphere and the associated changes in storm-track pattern that dominate the evolution of the surface European temperature. Influences of surface salinity and sea ice on the northern European temperature appear to have similar sensitivity mechanisms, invoked indirectly through their influence on near-surface temperature anomalies. The adjoint study thus confirms that the SST’s impact on the atmospheric dynamics, notably storm tracks, is the primary cause for the influence of northern European temperature changes.

Simulation of Present-Day and Twenty-First-Century Energy Budgets of the Southern Oceans

2010 ◽  
Vol 23 (2) ◽  
pp. 440-454 ◽  
Author(s):  
Kevin E. Trenberth ◽  
John T. Fasullo
Keyword(s):  
Southern Hemisphere ◽  
Cloud Cover ◽  
Climate Models ◽  
Global Climate ◽  
Strong Relationship ◽  
Global Climate Models ◽  
Storm Tracks ◽  
Energy Budgets ◽  
Poleward Shift ◽  
Projected Changes

Abstract The energy budget of the modern-day Southern Hemisphere is poorly simulated in both state-of-the-art reanalyses and coupled global climate models. The ocean-dominated Southern Hemisphere has low surface reflectivity and therefore its albedo is particularly sensitive to cloud cover. In modern-day climates, mainly because of systematic deficiencies in cloud and albedo at mid- and high latitudes, too much solar radiation enters the ocean. Along with too little radiation absorbed at lower latitudes because of clouds that are too bright, unrealistically weak poleward transports of energy by both the ocean and atmosphere are generally simulated in the Southern Hemisphere. This implies too little baroclinic eddy development and deficient activity in storm tracks. However, projections into the future by coupled climate models indicate that the Southern Ocean features a robust and unique increase in albedo, related to clouds, in association with an intensification and poleward shift in storm tracks that is not observed at any other latitude. Such an increase in cloud may be untenable in nature, as it is likely precluded by the present-day ubiquitous cloud cover that models fail to capture. There is also a remarkably strong relationship between the projected changes in clouds and the simulated current-day cloud errors. The model equilibrium climate sensitivity is also significantly negatively correlated with the Southern Hemisphere energy errors, and only the more sensitive models are in the range of observations. As a result, questions loom large about how the Southern Hemisphere will actually change as global warming progresses, and a better simulation of the modern-day climate is an essential first step.

scholarly journals Radiative and Dynamical Forcing of the Surface and Atmospheric Temperature Anomalies Associated with the Northern Annular Mode

2013 ◽  
Vol 26 (14) ◽  
pp. 5124-5138 ◽  
Author(s):  
Yi Deng ◽  
Tae-Won Park ◽  
Ming Cai
Keyword(s):  
Water Vapor ◽  
North America ◽  
Surface Temperature ◽  
Surface Albedo ◽  
Temperature Response ◽  
Atmospheric Temperature ◽  
Atmospheric Dynamics ◽  
Surface Dynamics ◽  
Northern Annular Mode ◽  
Temperature Anomalies

Abstract On the basis of the total energy balance within an atmosphere–surface column, an attribution analysis is conducted for the Northern Hemisphere (NH) atmospheric and surface temperature response to the northern annular mode (NAM) in boreal winter. The local temperature anomaly in the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) is decomposed into partial temperature anomalies because of changes in atmospheric dynamics, water vapor, clouds, ozone, surface albedo, and surface dynamics with the coupled atmosphere–surface climate feedback–response analysis method (CFRAM). Large-scale ascent/descent as part of the NAM-related mean meridional circulation anomaly adiabatically drives the main portion of the observed zonally averaged atmospheric temperature response, particularly the tropospheric cooling/warming over northern extratropics. Contributions from diabatic processes are generally small but could be locally important, especially at lower latitudes where radiatively active substances such as clouds and water vapor are more abundant. For example, in the tropical upper troposphere and stratosphere, both cloud and ozone forcings are critical in leading to the observed NAM-related temperature anomalies. Radiative forcing due to changes in water vapor acts as the main driver of the surface warming of southern North America during a positive phase of NAM, with atmospheric dynamics providing additional warming. In the negative phase of NAM, surface albedo change drives the surface cooling of southern North America, with atmospheric dynamics providing additional cooling. Over the subpolar North Atlantic and northern Eurasia, atmospheric dynamical processes again become the largest contributor to the NAM-related surface temperature anomalies, although changes in water vapor and clouds also contribute positively to the observed surface temperature anomalies while change in surface dynamics contributes negatively to the observed temperature anomalies.

scholarly journals Storm Tracks and Climate Change

2006 ◽  
Vol 19 (15) ◽  
pp. 3518-3543 ◽  
Author(s):  
Lennart Bengtsson ◽  
Kevin I. Hodges ◽  
Erich Roeckner
Keyword(s):  
Climate Change ◽  
Southern Hemisphere ◽  
Climate Model ◽  
Storm Track ◽  
Future Climate ◽  
Eastern Pacific ◽  
Storm Tracks ◽  
Intergovernmental Panel ◽  
Atlantic Sector ◽  
Poleward Shift

Abstract Extratropical and tropical transient storm tracks are investigated from the perspective of feature tracking in the ECHAM5 coupled climate model for the current and a future climate scenario. The atmosphere-only part of the model, forced by observed boundary conditions, produces results that agree well with analyses from the 40-yr ECMWF Re-Analysis (ERA-40), including the distribution of storms as a function of maximum intensity. This provides the authors with confidence in the use of the model for the climate change experiments. The statistical distribution of storm intensities is virtually preserved under climate change using the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario until the end of this century. There are no indications in this study of more intense storms in the future climate, either in the Tropics or extratropics, but rather a minor reduction in the number of weaker storms. However, significant changes occur on a regional basis in the location and intensity of storm tracks. There is a clear poleward shift in the Southern Hemisphere with consequences of reduced precipitation for several areas, including southern Australia. Changes in the Northern Hemisphere are less distinct, but there are also indications of a poleward shift, a weakening of the Mediterranean storm track, and a strengthening of the storm track north of the British Isles. The tropical storm tracks undergo considerable changes including a weakening in the Atlantic sector and a strengthening and equatorward shift in the eastern Pacific. It is suggested that some of the changes, in particular the tropical ones, are due to an SST warming maximum in the eastern Pacific. The shift in the extratropical storm tracks is shown to be associated with changes in the zonal SST gradient in particular for the Southern Hemisphere.

The Lifecycle and Physical Drivers of Heatwaves in a Hierarchy of Model Simulations  

2021 ◽  
Author(s):  
Bernat Jiménez-Esteve ◽  
Daniela I.V. Domeisen
Keyword(s):  
Surface Temperature ◽  
Extreme Temperature ◽  
Model Complexity ◽  
Extreme Weather Events ◽  
Horizontal Wind ◽  
Physical Processes ◽  
Near Surface ◽  
Temperature Anomalies ◽  
Model Configuration ◽  
Diabatic Processes

<p>Heatwaves are extreme weather events characterized by extreme near-surface temperature anomalies that persist for several days, which lead to catastrophic impacts on natural ecosystems, agriculture, human health, and economies. Different physical processes can contribute to the increase in temperature associated with heatwaves. Previous studies have shown that adiabatic compression due to subsidence and local land-atmosphere coupling are important drivers of summer heatwaves. However, less is known about the respective roles of these processes for heat extremes occurring in different seasons and latitudes.</p><p>By analyzing the different terms of the temperature tendency equation, we quantify the relative importance of horizontal wind advection, adiabatic, and diabatic processes (including radiation and surface fluxes) during the lifecycle of realistic and idealized heatwaves. We identify heatwaves both in reanalysis and in simulations using the ICOsahedral Nonhydrostatic (ICON) climate model. These simulations range from a simple zonally symmetric temperature relaxation and dry dynamics to a simulation using full physics, with coupled land and sea surface temperature forcing. This step-wise inclusion of physical processes and increasing model complexity allows us to identify the key drivers of extreme warm events and the characteristics of these across the different model complexities. In the simplest model configuration, i.e. only dry dynamics and no surface coupling, extreme temperature events are generally shorter but produce more intense temperature anomalies in the midlatitudes, where the horizontal temperature gradient is strongest. These idealized heatwaves are almost entirely driven by a very strong advection of warm air from more equatorward locations and are linked to local amplification of Rossby wave packets and atmospheric blocking. In contrast, in the complex model configuration as well as in reanalysis, summer heatwaves over land areas are mainly driven by adiabatic and diabatic processes, while advection is of secondary importance. On the other hand, extreme warm periods during winter are mainly driven by advection both in the model and reanalysis. Identifying the most relevant processes driving heatwaves can potentially benefit the prediction and representation of extreme events in operational weather and climate forecasts.</p>

scholarly journals The Relationship between the Southern Hemisphere Annular Mode and Antarctic Peninsula Summer Temperatures: Analysis of a High-Resolution Model Climatology

2008 ◽  
Vol 21 (8) ◽  
pp. 1649-1668 ◽  
Author(s):  
Nicole P. M. van Lipzig ◽  
Gareth J. Marshall ◽  
Andrew Orr ◽  
John C. King
Keyword(s):  
High Resolution ◽  
Surface Temperature ◽  
Southern Hemisphere ◽  
Antarctic Peninsula ◽  
Windward Side ◽  
Ice Shelf ◽  
Near Surface ◽  
Annular Mode ◽  
Surface Mass ◽  
Southern Hemisphere Annular Mode

Abstract The large regional summer warming on the east coast of the northern Antarctic Peninsula (AP), which has taken place since the mid-1960s, has previously been proposed to be caused by a trend in the Southern Hemisphere Annular Mode (SAM). The authors utilize a high-resolution regional atmospheric model climatology (14-km grid spacing) to study the mechanisms that determine the response of the near-surface temperature to an increase in the SAM (ΔT/ΔSAM). Month-to-month variations in near-surface temperature and surface pressure are well represented by the model. It is found that north of ∼68°S, ΔT/ΔSAM is much larger on the eastern (lee) side than on the western (windward) side of the barrier. This is because of the enhanced westerly flow of relatively warm air over the barrier, which warms (and dries) further as it descends down the lee slope. The downward motion on the eastern side of the barrier causes a decrease in surface-mass balance and cloud cover. South of ∼68°S, vertical deflection across the barrier is greatly reduced and the contrast in ΔT/ΔSAM between the east and west sides of the barrier vanishes. In the northeastern part of the AP, the modeled ΔT/ΔSAM distribution is similar to the distribution derived from satellite infrared radiometer data. The region of strongest modeled temperature sensitivity to the SAM is where ice shelf collapse has recently taken place and does not extend farther south over the Larsen-C Ice Shelf.

scholarly journals Impact of Soil Moisture–Atmosphere Interactions on Surface Temperature Distribution

2014 ◽  
Vol 27 (21) ◽  
pp. 7976-7993 ◽  
Author(s):  
Alexis Berg ◽  
Benjamin R. Lintner ◽  
Kirsten L. Findell ◽  
Sergey Malyshev ◽  
Paul C. Loikith ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Extreme Temperature ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Near Surface ◽  
Soil Moisture Dynamics ◽  
Available Energy ◽  
Mean And Variance ◽  
Moisture Dynamics

Abstract Understanding how different physical processes can shape the probability distribution function (PDF) of surface temperature, in particular the tails of the distribution, is essential for the attribution and projection of future extreme temperature events. In this study, the contribution of soil moisture–atmosphere interactions to surface temperature PDFs is investigated. Soil moisture represents a key variable in the coupling of the land and atmosphere, since it controls the partitioning of available energy between sensible and latent heat flux at the surface. Consequently, soil moisture variability driven by the atmosphere may feed back onto the near-surface climate—in particular, temperature. In this study, two simulations of the current-generation Geophysical Fluid Dynamics Laboratory (GFDL) Earth System Model, with and without interactive soil moisture, are analyzed in order to assess how soil moisture dynamics impact the simulated climate. Comparison of these simulations shows that soil moisture dynamics enhance both temperature mean and variance over regional “hotspots” of land–atmosphere coupling. Moreover, higher-order distribution moments, such as skewness and kurtosis, are also significantly impacted, suggesting an asymmetric impact on the positive and negative extremes of the temperature PDF. Such changes are interpreted in the context of altered distributions of the surface turbulent and radiative fluxes. That the moments of the temperature distribution may respond differentially to soil moisture dynamics underscores the importance of analyzing moments beyond the mean and variance to characterize fully the interplay of soil moisture and near-surface temperature. In addition, it is shown that soil moisture dynamics impacts daily temperature variability at different time scales over different regions in the model.

Considerations in Predicting Burnout of Cylinders in Flow Boiling

1992 ◽  
Vol 114 (1) ◽  
pp. 185-193 ◽  
Author(s):  
P. Sadasivan ◽  
J. H. Lienhard
Keyword(s):  
Heat Flux ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Flow Boiling ◽  
Heater Surface ◽  
Near Surface ◽  
Surface Temperature Distribution ◽  
Peak Heat Flux ◽  
Far Wake ◽  
Gravity Surface

Previous investigations of the critical heat flux in flow boiling have resulted in widely different hydrodynamic mechanisms for the occurrence of burnout. Results of the present study indicate that existing models are not completely realistic representations of the process. The present study sorts out the influences of the far-wake bubble breakoff and vapor sheet characteristics, gravity, surface wettability, and heater surface temperature distribution on the peak heat flux in flow boiling on cylindrical heaters. The results indicate that burnout is dictated by near-surface effects. The controlling factor appears to be the vapor escape pattern close to the heater surface. It is also shown that a deficiency of liquid at the downstream end of the heater surface is not the cause of burnout.

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