Estimating Changes in Temperature Distributions in a Large Ensemble of Climate Simulations Using Quantile Regression

Understanding future changes in extreme temperature events in a transient climate is inherently challenging. A single model simulation is generally insufficient to characterize the statistical properties of the evolving climate, but ensembles of repeated simulations with different initial conditions greatly expand the amount of data available. We present here a new approach for using ensembles to characterize changes in temperature distributions based on quantile regression that more flexibly characterizes seasonal changes. Specifically, our approach uses a continuous representation of seasonality rather than breaking the dataset into seasonal blocks; that is, we assume that temperature distributions evolve smoothly both day to day over an annual cycle and year to year over longer secular trends. To demonstrate our method’s utility, we analyze an ensemble of 50 simulations of the Community Earth System Model (CESM) under a scenario of increasing radiative forcing to 2100, focusing on North America. As previous studies have found, we see that daily temperature bulk variability generally decreases in wintertime in the continental mid- and high latitudes (>40°). A more subtle result that our approach uncovers is that differences in two low quantiles of wintertime temperatures do not shrink as much as the rest of the temperature distribution, producing a more negative skew in the overall distribution. Although the examples above concern temperature only, the technique is sufficiently general that it can be used to generate precise estimates of distributional changes in a broad range of climate variables by exploiting the power of ensembles.

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Interannual Variations of Summer Monsoons: Sensitivity to Cloud Radiative Forcing

Journal of Climate ◽

10.1175/1520-0442-11.8.1883 ◽

1998 ◽

Vol 11 (8) ◽

pp. 1883-1905 ◽

Cited By ~ 8

Author(s):

O. P. Sharma ◽

H. Le Treut ◽

G. Sèze ◽

L. Fairhead ◽

R. Sadourny

Keyword(s):

Optical Properties ◽

Radiative Forcing ◽

General Circulation ◽

Initial Conditions ◽

Model Simulation ◽

Circulation Model ◽

Interannual Variations ◽

Radiative Effects ◽

High Concentration ◽

Sea Temperature

Abstract The sensitivity of the interannual variations of the summer monsoons to imposed cloudiness has been studied with a general circulation model using the initial conditions prepared from the European Centre for Medium-Range Forecasts analyses of 1 May 1987 and 1988. The cloud optical properties in this global model are calculated from prognostically computed cloud liquid water. The model successfully simulates the contrasting behavior of these two successive monsoons. However, when the optical properties of the observed clouds are specified in the model runs, the simulations show some degradation over India and its vicinity. The main cause of this degradation is the reduced land–sea temperature contrast resulting from the radiative effects of the observed clouds imposed in such simulations. It is argued that the high concentration of condensed water content of clouds over the Indian land areas will serve to limit heating of the land, thereby reducing the thermal contrast that gives rise to a weak Somali jet. A countermonsoon circulation is, therefore, simulated in the vector difference field of 850-hPa winds from the model runs with externally specified clouds. This countermonsoon circulation is associated with an equatorial heat source that is the response of the model to the radiative effects of the imposed clouds. Indeed, there are at least two clear points that can be made: 1) the cloud–SST patterns, together, affect the interannual variability; and 2) with both clouds and SST imposed, the model simulation is less sensitive to initial conditions. Additionally, the study emphasizes the importance of dynamically consistent clouds developing in response to the dynamical, thermal, and moist state of the atmosphere during model integrations.

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DEVELOPMENT OF A EUROPEAN MULTIMODEL ENSEMBLE SYSTEM FOR SEASONAL-TO-INTERANNUAL PREDICTION (DEMETER)

Bulletin of the American Meteorological Society ◽

10.1175/bams-85-6-853 ◽

2004 ◽

Vol 85 (6) ◽

pp. 853-872 ◽

Cited By ~ 680

Author(s):

T. N. Palmer ◽

A. Alessandri ◽

U. Andersen ◽

P. Cantelaube ◽

M. Davey ◽

...

Keyword(s):

Initial Conditions ◽

Economic Value ◽

Ensemble Prediction ◽

Model Ensemble ◽

Single Model ◽

Multimodel Ensemble ◽

Coupled Models ◽

Ensemble Forecasts ◽

Ensemble Prediction System ◽

Climate Simulations

A multi-model ensemble-based system for seasonal-to-interannual prediction has been developed in a joint European project known as DEMETER (Development of a European Multimodel Ensemble Prediction System for Seasonal to Interannual Prediction). The DEMETER system comprises seven global atmosphere–ocean coupled models, each running from an ensemble of initial conditions. Comprehensive hindcast evaluation demonstrates the enhanced reliability and skill of the multimodel ensemble over a more conventional single-model ensemble approach. In addition, innovative examples of the application of seasonal ensemble forecasts in malaria and crop yield prediction are discussed. The strategy followed in DEMETER deals with important problems such as communication across disciplines, downscaling of climate simulations, and use of probabilistic forecast information in the applications sector, illustrating the economic value of seasonal-to-interannual prediction for society as a whole.

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Ultra-high resolution global warming simulations conducted with CESM

10.5194/egusphere-egu2020-1725 ◽

2020 ◽

Author(s):

Axel Timmermann ◽

Sun-Seon Lee ◽

Jung-Eun Chu

Keyword(s):

Radiative Forcing ◽

Southern Oscillation ◽

Horizontal Resolution ◽

Meridional Overturning Circulation ◽

Extreme Weather Events ◽

Future Climate Change ◽

Weather Events ◽

Climate Simulations ◽

Community Earth System Model ◽

Meridional Overturning

<div><span class="">To further improve our understanding of scale-interactions and key mechanisms leading to climate variability and extreme weather events, we conducted a series climate simulations using the ultrahigh-resolution Community Earth System Model (HR-CESM). The HR-CESM configuration uses a horizontal resolution of approximately 25 km for the atmospheric component and 10 km for the ocean. The simulations were carried out under present-day radiative forcing and for a variety of future greenhouse gas scenarios. This presentation highlights some key features of these simulations: the overall performance and important model biases, the representation of the Atlantic Meridional Overturning Circulation, tropical cyclone statistics, properties of sea-ice, the El Ni&#241;o-Southern Oscillation, as well as their responses to future climate change.&#160;</span><span class="">We will also present plans on how the data will be shared with the larger scientific community for further analysis and collaborative projects.&#160;</span></div>

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Kinematic characteristics of longitudinal double folding wings

The Aeronautical Journal ◽

10.1017/aer.2021.52 ◽

2021 ◽

pp. 1-25

Author(s):

L. Tiegang ◽

C. Guoguang ◽

L. Shuai

Keyword(s):

Angular Velocity ◽

Structural Model ◽

Initial Conditions ◽

Aerodynamic Force ◽

Model Simulation ◽

Lagrange Equation ◽

Grid Method ◽

Weapon Systems ◽

Folding Wing ◽

Double Folding

ABSTRACT A folding wing is a tactical missile launching device that needs to be miniaturised to facilitate storage, transportation, and launching; save missile and transportation space; and improve the combat capability of weapon systems. This study investigates the aeroelastic characteristics of the secondary longitudinal folding wing during the unfolding process. First, the Lagrange equation is used to establish the structural dynamics model of the folding wing, the kinematics characteristics during the deformation process are analysed, and the unfolding movement of the folding wing is obtained using the dynamic equations in the process. Then, the generalised unsteady aerodynamic force is calculated using the dipole grid method, and the multi-body dynamics equation of the folding wing is obtained. The initial angular velocity required for the deployment of the folding wing is analysed through structural model simulation, and the influence of the initial angular velocity on the opening process is studied. Finally, aeroelastic flutter analysis is performed on the folding wing, and the physical model of the folding wing verified experimentally. Results show that the type of aeroelastic response is sensitive to the initial conditions and the way the folding wing opens.

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Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-15-0126.1 ◽

2016 ◽

Vol 73 (4) ◽

pp. 1507-1527 ◽

Cited By ~ 18

Author(s):

Jason M. Keeler ◽

Brian F. Jewett ◽

Robert M. Rauber ◽

Greg M. McFarquhar ◽

Roy M. Rasmussen ◽

...

Keyword(s):

Vertical Velocity ◽

Radiative Forcing ◽

Initial Conditions ◽

Vertical Wind Shear ◽

Weather Research And Forecasting ◽

Velocity Spectrum ◽

Latent Heating ◽

Heating Rates ◽

Winter Storms ◽

Radiation Parameterizations

Abstract This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.

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Pseudorandom Number Generators Based on Chaotic Dynamical Systems

Open Systems & Information Dynamics ◽

10.1023/a:1011950531970 ◽

2001 ◽

Vol 08 (02) ◽

pp. 137-146 ◽

Cited By ~ 16

Author(s):

Janusz Szczepański ◽

Zbigniew Kotulski

Keyword(s):

Dynamical Systems ◽

Communication Systems ◽

Initial Conditions ◽

Pseudorandom Number ◽

New Approach ◽

Chaotic Dynamical Systems ◽

Pseudorandom Number Generators ◽

Transmission Of Information ◽

Extreme Sensitivity ◽

Contemporary Technology

Pseudorandom number generators are used in many areas of contemporary technology such as modern communication systems and engineering applications. In recent years a new approach to secure transmission of information based on the application of the theory of chaotic dynamical systems has been developed. In this paper we present a method of generating pseudorandom numbers applying discrete chaotic dynamical systems. The idea of construction of chaotic pseudorandom number generators (CPRNG) intrinsically exploits the property of extreme sensitivity of trajectories to small changes of initial conditions, since the generated bits are associated with trajectories in an appropriate way. To ensure good statistical properties of the CPRBG (which determine its quality) we assume that the dynamical systems used are also ergodic or preferably mixing. Finally, since chaotic systems often appear in realistic physical situations, we suggest a physical model of CPRNG.

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Role of sea surface temperature responses in simulation of the climatic effect of mineral dust aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-6049-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 6049-6062 ◽

Cited By ~ 30

Author(s):

X. Yue ◽

H. Liao ◽

H. J. Wang ◽

S. L. Li ◽

J. P. Tang

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

Radiative Forcing ◽

Mineral Dust ◽

Dust Aerosol ◽

Sea Surface ◽

Climatic Effect ◽

Radiative Effects ◽

Climate Simulations

Abstract. Mineral dust aerosol can be transported over the nearby oceans and influence the energy balance at the sea surface. The role of dust-induced sea surface temperature (SST) responses in simulations of the climatic effect of dust is examined by using a general circulation model with online simulation of mineral dust and a coupled mixed-layer ocean model. Both the longwave and shortwave radiative effects of mineral dust aerosol are considered in climate simulations. The SST responses are found to be very influential on simulated dust-induced climate change, especially when climate simulations consider the two-way dust-climate coupling to account for the feedbacks. With prescribed SSTs and dust concentrations, we obtain an increase of 0.02 K in the global and annual mean surface air temperature (SAT) in response to dust radiative effects. In contrast, when SSTs are allowed to respond to radiative forcing of dust in the presence of the dust cycle-climate interactions, we obtain a global and annual mean cooling of 0.09 K in SAT by dust. The extra cooling simulated with the SST responses can be attributed to the following two factors: (1) The negative net (shortwave plus longwave) radiative forcing of dust at the surface reduces SST, which decreases latent heat fluxes and upward transport of water vapor, resulting in less warming in the atmosphere; (2) The positive feedback between SST responses and dust cycle. The dust-induced reductions in SST lead to reductions in precipitation (or wet deposition of dust) and hence increase the global burden of small dust particles. These small particles have strong scattering effects, which enhance the dust cooling at the surface and further reduce SSTs.

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A Monte Carlo Method of Solving Heat Conduction Problems

Journal of Heat Transfer ◽

10.1115/1.3244222 ◽

1980 ◽

Vol 102 (1) ◽

pp. 121-125 ◽

Cited By ~ 14

Author(s):

S. K. Fraley ◽

T. J. Hoffman ◽

P. N. Stevens

Keyword(s):

Monte Carlo ◽

Heat Conduction ◽

Monte Carlo Method ◽

Transport Equation ◽

Heat Conduction Equation ◽

Analytical Techniques ◽

Conduction Equation ◽

Geometric Complexity ◽

New Approach ◽

Temperature Distributions

A new approach in the use of Monte Carlo to solve heat conduction problems is developed using a transport equation approximation to the heat conduction equation. A variety of problems is analyzed with this method and their solutions are compared to those obtained with analytical techniques. This Monte Carlo approach appears to be limited to the calculation of temperatures at specific points rather than temperature distributions. The method is applicable to the solution of multimedia problems with no inherent limitations as to the geometric complexity of the problem.

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A new approach for retrieving the UV–vis optical properties of ambient aerosols

Atmospheric Measurement Techniques ◽

10.5194/amt-9-3477-2016 ◽

2016 ◽

Vol 9 (8) ◽

pp. 3477-3490 ◽

Cited By ~ 17

Author(s):

Nir Bluvshtein ◽

J. Michel Flores ◽

Lior Segev ◽

Yinon Rudich

Keyword(s):

Optical Properties ◽

Atmospheric Aerosols ◽

Radiative Forcing ◽

Complex Refractive Index ◽

Single Scattering ◽

Aerosol Size Distribution ◽

Distribution Data ◽

Ambient Aerosols ◽

New Approach ◽

Effective Radiative Forcing

Abstract. Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol–radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

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