scholarly journals Analysis of Atmospheric Energy Transport in ERA-40 and Implications for Simple Models of the Mean Tropical Circulation

2008 ◽  
Vol 21 (20) ◽  
pp. 5229-5241 ◽  
Author(s):  
Matthew E. Peters ◽  
Zhiming Kuang ◽  
Christopher C. Walker
Keyword(s):  
Total Energy ◽  
Vertical Velocity ◽  
Vertical Profile ◽  
Large Scale ◽  
Energy Transport ◽  
Tropical Circulation ◽  
The Mean ◽  
Atmospheric Energy Transport ◽  
Convergence Zones ◽  
Mean Circulation

Abstract An analysis of atmospheric energy transport in 22 years (1980–2001) of the 40-yr ECMWF Re-Analysis (ERA-40) is presented. In the analyzed budgets, there is a large cancellation between divergences of dry static and latent energy such that the total energy divergence is positive over all tropical oceanic regions except for the east Pacific cold tongue, consistent with previous studies. The west Pacific and Indian Oceans are characterized by a balance between diabatic sources and mean advective energy export, with a small eddy contribution. However, in the central and eastern Pacific convergence zone, total energy convergence by the mean circulation is balanced by submonthly eddies, with a small diabatic source. Decomposing the mean advective tendency into terms due to horizontal and vertical advection shows that the spatial variation in the mean advection is due largely to variations in vertical advection; these variations are further attributed to variations in the vertical profile of the vertical velocity. The eddy energy export, due almost exclusively to eddy moisture export, does not exhibit any significant seasonal variation. The relationship between the eddies and the mean circulation is examined. Large-scale moisture diffusion is correlated with eddy moisture export on (500 km)2 spatial scales, implying that eddy activity preferentially dries narrow convergence zones over wide ones. Eddy moisture export is further linked to the depth of mean convection in large-scale convergence zones with larger eddy export associated with shallower circulations. This suggests a mechanism that could contribute to the observed variation in mean divergence profiles across the northern tropical Pacific whereby sea surface temperature gradients set the width of convergence zones and eddy activity modulates the tropospheric relative humidity and divergence profile. The importance of variations in the vertical profile of the vertical velocity and eddies in closing the energy budget implies that simple models of the mean tropical circulation should include these effects.

scholarly journals Simulated Relationships between Regional Temperatures and Large-Scale Circulation: 125 kyr BP (Eemian) and the Preindustrial Period

2005 ◽  
Vol 18 (19) ◽  
pp. 4032-4045 ◽  
Author(s):  
Nikolaus Groll ◽  
Martin Widmann ◽  
Julie M. Jones ◽  
Frank Kaspar ◽  
Stephan J. Lorenz
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Temperature Sensitive ◽  
Proxy Data ◽  
Large Scale Circulation ◽  
The North ◽  
Temperature Signal ◽  
Northern Winter ◽  
The Mean ◽  
Mean Circulation

Abstract To investigate relationships between large-scale circulation and regional-scale temperatures during the last (Eemian) interglacial, a simulation with a general circulation model (GCM) under orbital forcing conditions of 125 kyr BP is compared with a simulation forced with the Late Holocene preindustrial conditions. Consistent with previous GCM simulations for the Eemian, higher northern summer 2-m temperatures are found, which are directly related to the different insolation. Differences in the mean circulation are evident such as, for instance, stronger northern winter westerlies toward Europe, which are associated with warmer temperatures in central and northeastern Europe in the Eemian simulation, while the circulation variability, analyzed by means of a principal component analysis of the sea level pressure (SLP) field, is very similar in both periods. As a consequence of the differences in the mean circulation the simulated Arctic Oscillation (AO) temperature signal in the northern winter, on interannual-to-multidecadal time scales, is weaker during the Eemian than today over large parts of the Northern Hemisphere. Correlations between the AO index and the central European temperature (CET) decrease by about 0.2. The winter and spring SLP anomalies over the North Atlantic/European domain that are most strongly linearly linked to the CET cover a smaller area and are shifted westward over the North Atlantic during the Eemian. However, the strength of the connection between CET and these SLP anomalies is similar in both simulations. The simulated differences in the AO temperature signal and in the SLP anomaly, which is linearly linked to the CET, suggest that during the Eemian the link between the large-scale circulation and temperature-sensitive proxy data from Europe may differ from present-day conditions and that this difference should be taken into account when inferring large-scale climate from temperature-sensitive proxy data.

scholarly journals An MSE budget view on seasonal and CO2-induced ITCZ shifts in the TRAC-MIP model ensemble

2020 ◽  
Author(s):  
Elzina Bala ◽  
Aiko Voigt ◽  
Peter Knippertz
Keyword(s):  
Vertical Velocity ◽  
Vertical Structure ◽  
Energy Transport ◽  
Atmospheric Model ◽  
Grand Challenge ◽  
Model Ensemble ◽  
Tropical Circulation ◽  
Tropical Rainfall ◽  
Mip Model ◽  
The Impact

<p>One of the grand challenges of climate is predicting and modeling tropical rainfall. Here, we address a specific problem of this grand challenge, namely how does the vertical structure of the atmosphere affect the tropical circulation and the position of the ITCZ during the seasonal cycle and in response to increased CO<sub>2</sub>. The tropical circulation can be described by the column-integrated budget of moist static energy (MSE). We use this framework in the TRAC-MIP model ensemble to investigate the role of the vertical structure of the tropical atmosphere in setting the anti-correlation between the ITCZ location and the atmospheric energy transport.</p><p>TRACMIP "The Tropical Rain belts with an Annual cycle and Continent - Model Intercomparison Project" is a set of idealized simulations that are designed to study the tropical rain belt response to past and future forcings. TRACMIP includes 13 comprehensive CMIP5-class atmosphere models and one simplified atmospheric model. Importantly, TRACMIP includes a slab ocean with prescribed ocean heat transport. This leads to a closed surface energy balance and forces the annual-mean ITCZ to be north of the equator, consistent with today’s climate.</p><p>We use the MSE budget framework to diagnose the seasonal evolution of vertical velocity from the energetic terms in the MSE budget equation. We obtain a diagnostic expression for the vertical velocity. By means of the MSE budget framework we estimate the efficiency of exporting energy from the atmospheric column, which is defined as the gross moist stability (GMS). The GMS characterizes the stability of the tropical troposphere related to moist convective processes in the tropospheric column. We use the MSE and GMS analysis to disentangle the impact of deep and shallow circulations on energy transport, vertical velocity and hence precipitation in an objective manner.</p><p>Through this work we aim to elucidate to what extent model uncertainty in simulations of future ITCZ changes are caused by model differences in the vertical structure of the atmosphere. We also hope to use the results to advance our understanding of the tropical climate and to assess the plausibility of simulated changes in tropical rainfall.</p>

Evaluating the “Rich-Get-Richer” Mechanism in Tropical Precipitation Change under Global Warming

2009 ◽  
Vol 22 (8) ◽  
pp. 1982-2005 ◽  
Author(s):  
Chia Chou ◽  
J. David Neelin ◽  
Chao-An Chen ◽  
Jien-Yi Tu
Keyword(s):  
Global Warming ◽  
Vertical Velocity ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate Models ◽  
Dynamic Feedback ◽  
Precipitation Anomalies ◽  
The Rich ◽  
Convergence Zones ◽  
Gross Moist Stability

Abstract Examining tropical regional precipitation anomalies under global warming in 10 coupled global climate models, several mechanisms are consistently found. The tendency of rainfall to increase in convergence zones with large climatological precipitation and to decrease in subsidence regions—the rich-get-richer mechanism—has previously been examined in different approximations by Chou and Neelin, and Held and Soden. The effect of increased moisture transported by the mean circulation (the “direct moisture effect” or “thermodynamic component” in respective terminology) is relatively robust, while dynamic feedback is poorly understood and differs among models. The argument outlined states that the thermodynamic component should be a good approximation for large-scale averages; this is confirmed for averages across convection zones and descent regions, respectively. Within the convergence zones, however, dynamic feedback can substantially increase or decrease precipitation anomalies. Regions of negative precipitation anomalies within the convergence zones are associated with local weakening of ascent, and some of these exhibit horizontal dry advection associated with the “upped-ante” mechanism. Regions of increased ascent have strong positive precipitation anomalies enhanced by moisture convergence. This dynamic feedback is consistent with reduced gross moist stability due to increased moisture not being entirely compensated by effects of tropospheric warming and a vertical extent of convection. Regions of reduced ascent with positive precipitation anomalies are on average associated with changes in the vertical structure of vertical velocity, which extends to higher levels. This yields an increase in the gross moist stability that opposes ascent. The reductions in ascent associated with gross moist stability and upped-ante effects, respectively, combine to yield reduced ascent averaged across the convergence zones. Over climatological subsidence regions, positive precipitation anomalies can be associated with a convergence zone shift induced locally by anomalous heat flux from the ocean. Negative precipitation anomalies have a contribution from the thermodynamic component but can be enhanced or reduced by changes in the vertical velocity. Regions of enhanced subsidence are associated with an increased outgoing longwave radiation or horizontal cold convection. Reductions of subsidence are associated with changes of the vertical profile of vertical velocity, increasing gross moist stability.

scholarly journals Tropical Pacific–Driven Decadel Energy Transport Variability

2005 ◽  
Vol 18 (12) ◽  
pp. 2037-2051 ◽  
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.

scholarly journals A Diagnostic Model for The Large-Scale Tropical Circulation Based on Moist Static Energy Balance

2021 ◽  
Author(s):  
Chen-Shuo Fan ◽  
Dietmar Dommenget
Keyword(s):  
Seasonal Cycle ◽  
Large Scale ◽  
Vertical Motion ◽  
Diagnostic Model ◽  
Baroclinic Mode ◽  
Moist Static Energy ◽  
Tropical Circulation ◽  
The Mean ◽  
Static Energy ◽  
Mean State

Abstract In this study we present a diagnostic model for the large-scale tropical circulation (vertical motion) based on the moist static energy equation for first baroclinic mode anomalies (MSEB model). The aim of this model is to provide a basis for conceptual understanding of the drivers of the large-scale tropical circulation changes or variations as they are observed or simulated in Coupled Model Inter-comparison Project Phase (CMIP) models. The MSEB model is based on previous studies relating vertical motion in the tropics to the driving forces of the tropospheric column heating rate, advection of moisture and heat, and the moist stability of the air columns scaled by the first baroclinic mode. We apply and evaluate the skill of this model on the basis of observations (reanalysis) and CMIP model simulations of the large-scale tropical vertical motion. The model is capable of diagnosing the large-scale pattern of vertical motion of the mean state, annual cycle, interannual variability, model-to-model variations and in warmer climates of climate change scenarios with correlations of 0.6-0.8 and nearly unbiased amplitudes for the whole tropics (30°S-30°N). The skills are generally better over oceans at large scales and worse over land regions. The model also tends to have an upward motion bias at higher latitudes, but still has good correlations in variations even at the higher latitudes. It is further illustrated how the MSEB model can be used to diagnose the sensitivity of the tropical vertical motion to the forcing terms of the models for the mean state, seasonal cycle and interannual variability such as El Nino. The model clearly illustrates how the seasonal cycle in the circulation is driven by the incoming solar radiation and how the El Nino shift in the Walker circulation results mainly from the sea-surface temperature changes. Overall, the model provides a very good diagnostic tool to understand tropical circulation change on larger and longer (>month) time scales.

The Relation Between Large-Scale Vertical Motion and Weather in Summer

1958 ◽  
Vol 39 (10) ◽  
pp. 521-531 ◽  
Author(s):  
R. C. Curtis ◽  
H. A. Panofsky
Keyword(s):  
United States ◽  
Vertical Velocity ◽  
Large Scale ◽  
Vertical Motion ◽  
Convective Precipitation ◽  
Eastern United States ◽  
Fair Weather ◽  
Momentum Exchange ◽  
The Mean ◽  
Single Predictor

Large-scale vertical velocities are shown to be closely related to the probabilities of convective precipitation and fair weather in the eastern United States during July 1955. In the daytime the mean relative humidity of the 900 to 700 mb layer is better related to the probability of convective precipitation than the vertical velocity. At night, however, vertical velocity is the best single predictor of convective precipitation, with a modified Showalter Index being a very useful additional criterion. The large-scale vertical velocities that occur in normal summer synoptic situations appear to be produced by a diurnal variation in the momentum exchange between the ground and the air.

scholarly journals Validation of the Oxford WebQ Online 24-Hour Dietary Questionnaire Using Biomarkers

2019 ◽  
Vol 188 (10) ◽  
pp. 1858-1867 ◽  
Author(s):  
Darren C Greenwood ◽  
Laura J Hardie ◽  
Gary S Frost ◽  
Nisreen A Alwan ◽  
Kathryn E Bradbury ◽  
...  
Keyword(s):  
Measurement Error ◽  
Total Energy ◽  
Large Scale ◽  
Repeated Administration ◽  
Mean Value ◽  
Total Sugar ◽  
Dietary Recall ◽  
Average Value ◽  
The Mean ◽  
The Uk

Abstract The Oxford WebQ is an online 24-hour dietary questionnaire that is appropriate for repeated administration in large-scale prospective studies, including the UK Biobank study and the Million Women Study. We compared the performance of the Oxford WebQ and a traditional interviewer-administered multiple-pass 24-hour dietary recall against biomarkers for protein, potassium, and total sugar intake and total energy expenditure estimated by accelerometry. We recruited 160 participants in London, United Kingdom, between 2014 and 2016 and measured their biomarker levels at 3 nonconsecutive time points. The measurement error model simultaneously compared all 3 methods. Attenuation factors for protein, potassium, total sugar, and total energy intakes estimated as the mean of 2 applications of the Oxford WebQ were 0.37, 0.42, 0.45, and 0.31, respectively, with performance improving incrementally for the mean of more measures. Correlation between the mean value from 2 Oxford WebQs and estimated true intakes, reflecting attenuation when intake is categorized or ranked, was 0.47, 0.39, 0.40, and 0.38, respectively, also improving with repeated administration. These correlations were similar to those of the more administratively burdensome interviewer-based recall. Using objective biomarkers as the standard, the Oxford WebQ performs well across key nutrients in comparison with more administratively burdensome interviewer-based 24-hour recalls. Attenuation improves when the average value is taken over repeated administrations, reducing measurement error bias in assessment of diet-disease associations.

Understanding changes in tropical circulations in a future warmer climate using a cloud-resolving model and a conceptual model

2021 ◽  
Author(s):  
Sramana Neogi ◽  
Martin Singh
Keyword(s):  
Surface Temperature ◽  
Vertical Velocity ◽  
Large Scale ◽  
Entrainment Rate ◽  
Moist Convection ◽  
Tropical Circulation ◽  
Thermodynamic Structure ◽  
Reference Profile ◽  
Cloud Resolving Model ◽  
Vertical Velocity Profile

<p>The interaction between large-scale tropical circulations and moist convection has been the focus of a number of studies. However, projections of how the large-scale tropical circulation may change under global warming remain uncertain because our understanding of this interaction is still limited.</p><p>Here, we use a cloud-resolving model (CRM) coupled with a supra-domain scale (SDS) parameterisation of the large-scale circulation to investigate how tropical circulations driven by sea-surface temperature (SST) gradients change in a future warmer climate. Two popular SDS parameterisation schemes are compared; the weak temperature gradient approximation and the damped-gravity-wave approximation. In both cases, the large-scale vertical velocity is related to the deviation of the simulated density profile from a reference profile taken from the same model run to radiative-convective equilibrium.</p><p>We examine how the large-scale vertical velocity profile varies with surface temperature for fixed background profile (relative SST) as well as how it varies with the surface temperature of the reference profile (background SST). The domain mean vertical velocity appears to be very top-heavy with the maximum vertical velocity becoming stronger at warmer surface temperatures. The results are understood using a simple model for the thermodynamic structure of a convecting atmosphere based on an entraining plume. The model uses a fixed entrainment rate and the relative humidity from the cloud-resolving model to predict a temperature profile. The vertical velocities calculated from these predicted temperature profiles is similar to the vertical velocity structures and their behaviour in a warmer climate that we see in the CRM simulations. The results provide insight into large scale vertical velocity structures simulated by SDS parameterisation schemes, providing a stepping stone to understanding the factors driving changes to the large-scale tropical circulation in a future warmer climate.</p>

scholarly journals On generation of a stochastic GW background by the scattering on relic wormholes

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
A. A. Kirillov ◽  
E. P. Savelova ◽  
O. M. Lecian
Keyword(s):  
Total Energy ◽  
Transport Equation ◽  
Gravitational Waves ◽  
Frequency Spectrum ◽  
Energy Transport ◽  
Mean Amplitude ◽  
Direct Wave ◽  
The Earth ◽  
Normal Matter ◽  
The Mean

AbstractWe study collective features of the scattering of gravitational waves on relic wormholes and normal matter objects. We derive and solve the GW energy transport equation and show that the scattered signal lies in the same frequency spectrum bands as the basic signal. The scattering forms long living tails which always accompany the basic signal and have a universal form. The scattering on normal matter objects forms tails which have always the retarded character, while wormholes lead to advanced tails as well. In addition, wormholes may produce considerably stronger effect when the total energy in tails detected on the Earth exceeds that in the incident direct wave. In both cases the retarding tails have a long living character when the mean amplitude behaves with time as $$h\sim 1/\sqrt{t+R/c}$$ h ∼ 1 / t + R / c . For a single GW event the echo tails give only a tiny contribution to the mean amplitude. However such tails accumulate with events and form a stochastic GW background which may be observed by the contribution to the noise.

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