scholarly journals A simple model of ozone-temperature coupling in the tropical lower stratosphere

2021 ◽  
Author(s):  
William J. Randel ◽  
Fei Wu ◽  
Alison Ming ◽  
Peter Hitchcock
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Large Scale ◽  
Lower Stratosphere ◽  
Strong Correlations ◽  
Continuity Equations ◽  
Wide Range ◽  
Radiative Feedbacks ◽  
Seasonal And Interannual Variations ◽  
Balloon Measurements

Abstract. Observations show strong correlations between large-scale ozone and temperature variations in the tropical lower stratosphere across a wide range of time scales. We quantify this behavior using monthly records of ozone and temperature data from SHADOZ tropical balloon measurements (1998–2016), along with global satellite data from Aura MLS and GPS radio occultation over 2004–2018. The observational data demonstrate strong in-phase ozone-temperature coherence spanning sub-seasonal, annual and interannual time scales, and the slope of the ozone-temperature relationship (O3/T) varies as a function of time scale and altitude. We compare the observations to idealized calculations based on the coupled zonal mean thermodynamic and ozone continuity equations, including ozone radiative feedbacks on temperature, where both temperature and ozone respond in a coupled manner to variations in the tropical upwelling Brewer-Dobson circulation. These calculations can approximately explain the observed (O3/T) amplitude and phase relationships, including sensitivity to time scale and altitude, and highlight distinct balances for ‘fast’ variations (periods < 150 days, controlled by transport across background vertical gradients) and ‘slow’ coupling (seasonal and interannual variations, controlled by radiative balances).

scholarly journals A simple model of ozone–temperature coupling in the tropical lower stratosphere

2021 ◽  
Vol 21 (24) ◽  
pp. 18531-18542
Author(s):  
William J. Randel ◽  
Fei Wu ◽  
Alison Ming ◽  
Peter Hitchcock
Keyword(s):  
Large Scale ◽  
Radio Occultation ◽  
Lower Stratosphere ◽  
Strong Correlations ◽  
Continuity Equations ◽  
Wide Range ◽  
Radiative Feedbacks ◽  
Seasonal And Interannual Variations ◽  
Balloon Measurements ◽  
Phase Relationships

Abstract. Observations show strong correlations between large-scale ozone and temperature variations in the tropical lower stratosphere across a wide range of timescales. We quantify this behavior using monthly records of ozone and temperature data from Southern Hemisphere Additional Ozonesonde (SHADOZ) tropical balloon measurements (1998–2016), along with global satellite data from Aura microwave limb sounder and GPS radio occultation over 2004–2018. The observational data demonstrate strong in-phase ozone–temperature coherence spanning sub-seasonal, annual and interannual timescales, and the slope of the temperature–ozone relationship (T / O3) varies as a function of timescale and altitude. We compare the observations to idealized calculations based on the coupled zonal mean thermodynamic and ozone continuity equations, including ozone radiative feedbacks on temperature, where both temperature and ozone respond in a coupled manner to variations in the tropical upwelling Brewer–Dobson circulation. These calculations can approximately explain the observed (T / O3) amplitude and phase relationships, including sensitivity to timescale and altitude, and highlight distinct balances for “fast” variations (periods < 150 d, controlled by transport across background vertical gradients) and “slow” coupling (seasonal and interannual variations, controlled by radiative balances).

scholarly journals Convective forcing of the North American Monsoon Anticyclone at intraseasonal and interannual time scales

2021 ◽  
Author(s):  
Kai-Wei Chang ◽  
Kenneth P. Bowman ◽  
Leong Wai Siu ◽  
Anita D. Rapp
Keyword(s):  
Time Scales ◽  
North American ◽  
Time Scale ◽  
General Circulation ◽  
Large Scale ◽  
Vertical Structure ◽  
Lower Stratosphere ◽  
North American Monsoon ◽  
The North ◽  
Circulation Anomalies

AbstractIn the upper troposphere and lower stratosphere (UTLS), large-scale anticyclones associated with monsoons play major roles in tropospheric and stratospheric transport and mixing. To understand the forcing of the North American Monsoon Anticyclone (NAMA), this study examines the connection between precipitation over the tropics and subtropics of the North American longitude sector and the variability of the troposphere and lower stratosphere. Using ERA5 reanalysis and outgoing longwave radiation (OLR) data from 1979 to 2019, we assess the relationship at the intraseasonal time scale using pentad-mean time series. We show that OLR anomalies are correlated with circulation anomalies northwest and northeast of the region of precipitation. Decreased OLR (increased precipitation) corresponds to increased geopotential heights and anticyclonic circulation anomalies in the 300 – 100 hPa layer and an opposite response in the lower tropospheric 850 – 600 hPa layer. The results are consistent with the established theory of the Rossby wave response to latent heating. The increase in height, which is strongest near 150 hPa, indicates that increased precipitation is associated with a strengthened NAMA. UTLS temperatures also have significant correlations with OLR, with cold (warm) anomalies occurring above (below) the core of the anticyclonic anomaly consistent with large-scale balance. The vertical structure of geopotential and temperature anomalies is compared to simulations using an idealized general circulation model, which shows that such a vertical structure is a consistent response to diabatic heating. Correlations at the interannual time scale resemble those at the intraseasonal time scale, demonstrating that precipitation is related to the NAMA at both time scales.

scholarly journals Stochastic modelling of star-formation histories II: star-formation variability from molecular clouds and gas inflow

2020 ◽  
Vol 497 (1) ◽  
pp. 698-725 ◽  
Author(s):  
Sandro Tacchella ◽  
John C Forbes ◽  
Neven Caplar
Keyword(s):  
Life Cycle ◽  
Star Formation ◽  
Time Scales ◽  
Time Scale ◽  
Molecular Clouds ◽  
Star Formation History ◽  
Small Scale ◽  
Inflow Rate ◽  
Wide Range ◽  
The Galaxy

ABSTRACT A key uncertainty in galaxy evolution is the physics regulating star formation, ranging from small-scale processes related to the life-cycle of molecular clouds within galaxies to large-scale processes such as gas accretion on to galaxies. We study the imprint of such processes on the time-variability of star formation with an analytical approach tracking the gas mass of galaxies (‘regulator model’). Specifically, we quantify the strength of the fluctuation in the star-formation rate (SFR) on different time-scales, i.e. the power spectral density (PSD) of the star-formation history, and connect it to gas inflow and the life-cycle of molecular clouds. We show that in the general case the PSD of the SFR has three breaks, corresponding to the correlation time of the inflow rate, the equilibrium time-scale of the gas reservoir of the galaxy, and the average lifetime of individual molecular clouds. On long and intermediate time-scales (relative to the dynamical time-scale of the galaxy), the PSD is typically set by the variability of the inflow rate and the interplay between outflows and gas depletion. On short time-scales, the PSD shows an additional component related to the life-cycle of molecular clouds, which can be described by a damped random walk with a power-law slope of β ≈ 2 at high frequencies with a break near the average cloud lifetime. We discuss star-formation ‘burstiness’ in a wide range of galaxy regimes, study the evolution of galaxies about the main sequence ridgeline, and explore the applicability of our method for understanding the star-formation process on cloud-scale from galaxy-integrated measurements.

scholarly journals An Analysis of Moisture Fluxes into the Gulf of California

2009 ◽  
Vol 22 (8) ◽  
pp. 2216-2239 ◽  
Author(s):  
Man-Li C. Wu ◽  
Siegfried D. Schubert ◽  
Max J. Suarez ◽  
Norden E. Huang
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Gulf Of California ◽  
Large Scale ◽  
Moisture Flux ◽  
Easterly Waves ◽  
Low Level ◽  
Moisture Fluxes ◽  
The Caribbean ◽  
The U.S

Abstract This study examines the nature of episodes of enhanced warm-season moisture flux into the Gulf of California. Both spatial structure and primary time scales of the fluxes are examined using the 40-yr ECMWF Re-Analysis data for the period 1980–2001. The analysis approach consists of a compositing technique that is keyed on the low-level moisture fluxes into the Gulf of California. The results show that the fluxes have a rich spectrum of temporal variability, with periods of enhanced transport over the gulf linked to African easterly waves on subweekly (3–8 day) time scales, the Madden–Julian oscillation (MJO) at intraseasonal time scales (20–90 day), and intermediate (10–15 day) time-scale disturbances that appear to originate primarily in the Caribbean Sea–western Atlantic Ocean. In the case of the MJO, enhanced low-level westerlies and large-scale rising motion provide an environment that favors large-scale cyclonic development near the west coast of Central America that, over the course of about 2 weeks, expands northward along the coast eventually reaching the mouth of the Gulf of California where it acts to enhance the southerly moisture flux in that region. On a larger scale, the development includes a northward shift in the eastern Pacific ITCZ, enhanced precipitation over much of Mexico and the southwestern United States, and enhanced southerly/southeasterly fluxes from the Gulf of Mexico into Mexico and the southwestern and central United States. In the case of the easterly waves, the systems that reach Mexico appear to redevelop/reorganize on the Pacific coast and then move rapidly to the northwest to contribute to the moisture flux into the Gulf of California. The most intense fluxes into the gulf on these time scales appear to be synchronized with a midlatitude short-wave trough over the U.S. West Coast and enhanced low-level southerly fluxes over the U.S. Great Plains. The intermediate (10–15 day) time-scale systems have zonal wavelengths roughly twice that of the easterly waves, and their initiation appears to be linked to an extratropical U.S. East Coast ridge and associated northeasterly winds that extend well into the Caribbean Sea during their development phase. The short (3–8 day) and, to a lesser extent, the intermediate (10–15 day) time-scale fluxes tend to be enhanced when the convectively active phase of the MJO is situated over the Americas.

scholarly journals Analysis and Reduction of Systematic Errors through a Seamless Approach to Modeling Weather and Climate

2010 ◽  
Vol 23 (22) ◽  
pp. 5933-5957 ◽  
Author(s):  
G. M. Martin ◽  
S. F. Milton ◽  
C. A. Senior ◽  
M. E. Brooks ◽  
S. Ineson ◽  
...  
Keyword(s):  
Time Scales ◽  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Spatial Scales ◽  
Full Range ◽  
Model Development ◽  
Model Performance ◽  
Systematic Errors ◽  
Wide Range

Abstract The reduction of systematic errors is a continuing challenge for model development. Feedbacks and compensating errors in climate models often make finding the source of a systematic error difficult. In this paper, it is shown how model development can benefit from the use of the same model across a range of temporal and spatial scales. Two particular systematic errors are examined: tropical circulation and precipitation distribution, and summer land surface temperature and moisture biases over Northern Hemisphere continental regions. Each of these errors affects the model performance on time scales ranging from a few days to several decades. In both cases, the characteristics of the long-time-scale errors are found to develop during the first few days of simulation, before any large-scale feedbacks have taken place. The ability to compare the model diagnostics from the first few days of a forecast, initialized from a realistic atmospheric state, directly with observations has allowed physical deficiencies in the physical parameterizations to be identified that, when corrected, lead to improvements across the full range of time scales. This study highlights the benefits of a seamless prediction system across a wide range of time scales.

scholarly journals Understanding the Time Scales of the Tropospheric Circulation Response to Abrupt CO2 Forcing in the Southern Hemisphere: Seasonality and the Role of the Stratosphere

2017 ◽  
Vol 30 (21) ◽  
pp. 8497-8515 ◽  
Author(s):  
Kevin M. Grise ◽  
Lorenzo M. Polvani
Keyword(s):  
Surface Temperature ◽  
Southern Hemisphere ◽  
Time Scales ◽  
Time Scale ◽  
Lower Stratosphere ◽  
Hadley Cell ◽  
Global Mean Surface Temperature ◽  
Tropospheric Circulation ◽  
Dry Zone ◽  
Global Mean

This study examines the time scales of the Southern Hemisphere (SH) tropospheric circulation response to increasing atmospheric CO2 concentrations in models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In response to an abrupt quadrupling of atmospheric CO2, the midlatitude jet stream and poleward edge of the Hadley circulation shift poleward on the time scale of the rising global-mean surface temperature during the summer and fall seasons but on a much more rapid time scale during the winter and spring seasons. The seasonally varying time scales of the SH circulation response are closely tied to the meridional temperature gradient in the upper troposphere–lower stratosphere and, in particular, to temperatures in the SH polar lower stratosphere. During summer and fall, SH polar lower-stratospheric temperatures cool on the time scale of warming global surface temperatures, as the lifting of the tropopause height with tropospheric warming is associated with cooling at lower-stratospheric levels. However, during winter and spring, SH polar lower-stratospheric temperatures cool primarily from fast time-scale radiative processes, contributing to the faster time-scale circulation response during these seasons. The poleward edge of the SH subtropical dry zone shifts poleward on the time scale of the rising global-mean surface temperature during all seasons in response to an abrupt quadrupling of atmospheric CO2. The dry zone edge initially follows the poleward shift in the Hadley cell edge but is then augmented by the action of eddy moisture fluxes in a warming climate. Consequently, with increasing atmospheric CO2 concentrations, key features of the tropospheric circulation response could emerge sooner than features more closely tied to rising global temperatures.

scholarly journals A Year-Long Large-Eddy Simulation of the Weather over Cabauw: An Overview

2015 ◽  
Vol 143 (3) ◽  
pp. 828-844 ◽  
Author(s):  
Jerôme Schalkwijk ◽  
Harmen J. J. Jonker ◽  
A. Pier Siebesma ◽  
Fred C. Bosveld
Keyword(s):  
Time Series ◽  
Large Eddy Simulation ◽  
Time Scales ◽  
Large Scale ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Scale Model ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy

Abstract Results are presented of two large-eddy simulation (LES) runs of the entire year 2012 centered at the Cabauw observational supersite in the Netherlands. The LES is coupled to a regional weather model that provides the large-scale information. The simulations provide three-dimensional continuous time series of LES-generated turbulence and clouds, which can be compared in detail to the extensive observational dataset of Cabauw. The LES dataset is available from the authors on request. This type of LES setup has a number of advantages. First, it can provide a more statistical approach to the study of turbulent atmospheric flow than the more common case studies, since a diverse but representative set of conditions is covered, including numerous transitions. This has advantages in the design and evaluation of parameterizations. Second, the setup can provide valuable information on the quality of the LES model when applied to such a wide range of conditions. Last, it also provides the possibility to emulate observation techniques. This might help detect limitations and potential problems of a variety of measurement techniques. The LES runs are validated through a comparison with observations from the observational supersite and with results from the “parent” large-scale model. The long time series that are generated, in combination with information on the spatial structure, provide a novel opportunity to study time scales ranging from seconds to seasons. This facilitates a study of the power spectrum of horizontal and vertical wind speed variance to identify the dominant variance-containing time scales.

scholarly journals Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs

2020 ◽  
Vol 216 (8) ◽  
Author(s):  
Adam P. Showman ◽  
Xianyu Tan ◽  
Vivien Parmentier
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Brown Dwarfs ◽  
Global Scale ◽  
Giant Planets ◽  
External Irradiation ◽  
Night Temperature ◽  
Hot Jupiters ◽  
Wide Range ◽  
Radiative Feedbacks

AbstractGroundbased and spacecraft telescopic observations, combined with an intensive modeling effort, have greatly enhanced our understanding of hot giant planets and brown dwarfs over the past ten years. Although these objects are all fluid, hydrogen worlds with stratified atmospheres overlying convective interiors, they exhibit an impressive diversity of atmospheric behavior. Hot Jupiters are strongly irradiated, and a wealth of observations constrain the day-night temperature differences, circulation, and cloudiness. The intense stellar irradiation, presumed tidal locking and modest rotation leads to a novel regime of strong day-night radiative forcing. Circulation models predict large day-night temperature differences, global-scale eddies, patchy clouds, and, in most cases, a fast eastward jet at the equator—equatorial superrotation. The warm Jupiters lie farther from their stars and are not generally tidally locked, so they may exhibit a wide range of rotation rates, obliquities, and orbital eccentricities, which, along with the weaker irradiation, leads to circulation patterns and observable signatures predicted to differ substantially from hot Jupiters. Brown dwarfs are typically isolated, rapidly rotating worlds; they radiate enormous energy fluxes into space and convect vigorously in their interiors. Their atmospheres exhibit patchiness in clouds and temperature on regional to global scales—the result of modulation by large-scale atmospheric circulation. Despite the lack of irradiation, such circulations can be driven by interaction of the interior convection with the overlying atmosphere, as well as self-organization of patchiness due to cloud-dynamical-radiative feedbacks. Finally, irradiated brown dwarfs help to bridge the gap between these classes of objects, experiencing intense external irradiation as well as vigorous interior convection. Collectively, these diverse objects span over six orders of magnitude in intrinsic heat flux and incident stellar flux, and two orders of magnitude in rotation rate—thereby placing strong constraints on how the circulation of giant planets (broadly defined) depend on these parameters. A hierarchy of modeling approaches have yielded major new insights into the dynamics governing these phenomena.

scholarly journals Functional protein dynamics on uncharted time scales detected by nanoparticle-assisted NMR spin relaxation

2019 ◽  
Vol 5 (8) ◽  
pp. eaax5560 ◽  
Author(s):  
Mouzhe Xie ◽  
Lei Yu ◽  
Lei Bruschweiler-Li ◽  
Xinyao Xiang ◽  
Alexandar L. Hansen ◽  
...  
Keyword(s):  
Time Scales ◽  
Spin Relaxation ◽  
Protein Interactions ◽  
Protein Function ◽  
Large Scale ◽  
Transverse Spin ◽  
Protein Protein Interactions ◽  
Functional Protein ◽  
Wide Range ◽  
Nmr Spin Relaxation

Protein function depends critically on intrinsic internal dynamics, which is manifested in distinct ways, such as loop motions that regulate protein recognition and catalysis. Under physiological conditions, dynamic processes occur on a wide range of time scales from subpicoseconds to seconds. Commonly used NMR spin relaxation in solution provides valuable information on very fast and slow motions but is insensitive to the intermediate nanosecond to microsecond range that exceeds the protein tumbling correlation time. Presently, very little is known about the nature and functional role of these motions. It is demonstrated here how transverse spin relaxation becomes exquisitely sensitive to these motions at atomic resolution when studying proteins in the presence of nanoparticles. Application of this novel cross-disciplinary approach reveals large-scale dynamics of loops involved in functionally critical protein-protein interactions and protein-calcium ion recognition that were previously unobservable.

scholarly journals Storm Event to Seasonal Evolution of Nearshore Bathymetry Derived from Shore-Based Video Imagery

2019 ◽  
Vol 11 (5) ◽  
pp. 519 ◽  
Author(s):  
Erwin Bergsma ◽  
Daniel Conley ◽  
Mark Davidson ◽  
Tim O'Hare ◽  
Rafael Almar
Keyword(s):  
Time Scales ◽  
Temporal Resolution ◽  
Time Scale ◽  
High Frequency ◽  
Morphological Evolution ◽  
Storm Event ◽  
Extreme Storm ◽  
Wide Range ◽  
Long Time ◽  
Wave Conditions

Coastal evolution occurs on a wide range of time-scales, from storms, seasonal and inter-annual time-scales to longer-term adaptation to changing environmental conditions. Measuring campaigns typically either measure morphological evolution on a short-time scale (days) with high frequency (hourly) or long-time scales (years) but intermittently (monthly). This leaves an important observational gap that limits morphological variability assessments. Traditional echo sounding measurements on this long time-scale and high-frequency sampling require a significant financial injection. Shore-based video systems with high spatiotemporal resolution can bridge this gap. For the first time, hourly Kalman filtered video-derived bathymetries covering 1.5 years of morphological evolution with an hourly resolution obtained at Porhtowan, UK are presented. Here, the long-term hourly dataset is used and aims to show its added value for, and provide an in-depth, morphological analyses with unprecedented temporal resolution. The time-frame includes calm and extreme (storm) wave conditions in a macro-tidal environment. The video-derived bathymetries allow hourly beach state classification while before this was not possible due to the dependence on foam patterns of wave breaking (e.g., saturation during storms). The study period covers extreme storm erosion during the most energetic winter season in 60 years (2013–2014). Recovery of the beach takes place on several time-scales: (1) an immediate initial recovery after the storm season (first 2 months), (2) limited recovery during low energetic summer conditions and (3) accelerated recovery as the wave conditions picked up in the subsequent fall—under wave conditions that are typically erosive. The video-derived bathymetries are shown to be effective in determining bar-positions, outer-bar three-dimensionality and volume analyses with an unprecedented hourly temporal resolution.

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