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T. Jung
,
M. J. Miller
,
T. N. Palmer
,
P. Towers
,
N. Wedi
,
D. Achuthavarier
,
J. M. Adams
,
E. L. Altshuler
,
B. A. Cash
,
J. L. Kinter III
,
L. Marx
,
C. Stan
, and
K. I. Hodges

Abstract

The sensitivity to the horizontal resolution of the climate, anthropogenic climate change, and seasonal predictive skill of the ECMWF model has been studied as part of Project Athena—an international collaboration formed to test the hypothesis that substantial progress in simulating and predicting climate can be achieved if mesoscale and subsynoptic atmospheric phenomena are more realistically represented in climate models.

In this study the experiments carried out with the ECMWF model (atmosphere only) are described in detail. Here, the focus is on the tropics and the Northern Hemisphere extratropics during boreal winter. The resolutions considered in Project Athena for the ECMWF model are T159 (126 km), T511 (39 km), T1279 (16 km), and T2047 (10 km). It was found that increasing horizontal resolution improves the tropical precipitation, the tropical atmospheric circulation, the frequency of occurrence of Euro-Atlantic blocking, and the representation of extratropical cyclones in large parts of the Northern Hemisphere extratropics. All of these improvements come from the increase in resolution from T159 to T511 with relatively small changes for further resolution increases to T1279 and T2047, although it should be noted that results from this very highest resolution are from a previously untested model version. Problems in simulating the Madden–Julian oscillation remain unchanged for all resolutions tested. There is some evidence that increasing horizontal resolution to T1279 leads to moderate increases in seasonal forecast skill during boreal winter in the tropics and Northern Hemisphere extratropics. Sensitivity experiments are discussed, which helps to foster a better understanding of some of the resolution dependence found for the ECMWF model in Project Athena.

Full access
Antje Weisheimer
,
Laura H. Baker
,
Jochen Bröcker
,
Chaim I. Garfinkel
,
Steven C. Hardiman
,
Dan L.R. Hodson
,
Tim N. Palmer
,
Jon I. Robson
,
Adam A. Scaife
,
James A. Screen
,
Theodore G. Shepherd
,
Doug M. Smith
, and
Rowan T. Sutton
Open access
T. N. Palmer
,
A. Alessandri
,
U. Andersen
,
P. Cantelaube
,
M. Davey
,
P. Délécluse
,
M. Déqué
,
E. Díez
,
F. J. Doblas-Reyes
,
H. Feddersen
,
R. Graham
,
S. Gualdi
,
J.-F. Guérémy
,
R. Hagedorn
,
M. Hoshen
,
N. Keenlyside
,
M. Latif
,
A. Lazar
,
E. Maisonnave
,
V. Marletto
,
A. P. Morse
,
B. Orfila
,
P. Rogel
,
J.-M. Terres
, and
M. C. Thomson

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.

Full access
J. L. Kinter III
,
B. Cash
,
D. Achuthavarier
,
J. Adams
,
E. Altshuler
,
P. Dirmeyer
,
B. Doty
,
B. Huang
,
E. K. Jin
,
L. Marx
,
J. Manganello
,
C. Stan
,
T. Wakefield
,
T. Palmer
,
M. Hamrud
,
T. Jung
,
M. Miller
,
P. Towers
,
N. Wedi
,
M. Satoh
,
H. Tomita
,
C. Kodama
,
T. Nasuno
,
K. Oouchi
,
Y. Yamada
,
H. Taniguchi
,
P. Andrews
,
T. Baer
,
M. Ezell
,
C. Halloy
,
D. John
,
B. Loftis
,
R. Mohr
, and
K. Wong

The importance of using dedicated high-end computing resources to enable high spatial resolution in global climate models and advance knowledge of the climate system has been evaluated in an international collaboration called Project Athena. Inspired by the World Modeling Summit of 2008 and made possible by the availability of dedicated high-end computing resources provided by the National Science Foundation from October 2009 through March 2010, Project Athena demonstrated the sensitivity of climate simulations to spatial resolution and to the representation of subgrid-scale processes with horizontal resolutions up to 10 times higher than contemporary climate models. While many aspects of the mean climate were found to be reassuringly similar, beyond a suggested minimum resolution, the magnitudes and structure of regional effects can differ substantially. Project Athena served as a pilot project to demonstrate that an effective international collaboration can be formed to efficiently exploit dedicated supercomputing resources. The outcomes to date suggest that, in addition to substantial and dedicated computing resources, future climate modeling and prediction require a substantial research effort to efficiently explore the fidelity of climate models when explicitly resolving important atmospheric and oceanic processes.

Full access
N. R. P. Harris
,
L. J. Carpenter
,
J. D. Lee
,
G. Vaughan
,
M. T. Filus
,
R. L. Jones
,
B. OuYang
,
J. A. Pyle
,
A. D. Robinson
,
S. J. Andrews
,
A. C. Lewis
,
J. Minaeian
,
A. Vaughan
,
J. R. Dorsey
,
M. W. Gallagher
,
M. Le Breton
,
R. Newton
,
C. J. Percival
,
H. M. A. Ricketts
,
S. J.-B. Bauguitte
,
G. J. Nott
,
A. Wellpott
,
M. J. Ashfold
,
J. Flemming
,
R. Butler
,
P. I. Palmer
,
P. H. Kaye
,
C. Stopford
,
C. Chemel
,
H. Boesch
,
N. Humpage
,
A. Vick
,
A. R. MacKenzie
,
R. Hyde
,
P. Angelov
,
E. Meneguz
, and
A. J. Manning

Abstract

The main field activities of the Coordinated Airborne Studies in the Tropics (CAST) campaign took place in the west Pacific during January–February 2014. The field campaign was based in Guam (13.5°N, 144.8°E), using the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 atmospheric research aircraft, and was coordinated with the Airborne Tropical Tropopause Experiment (ATTREX) project with an unmanned Global Hawk and the Convective Transport of Active Species in the Tropics (CONTRAST) campaign with a Gulfstream V aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km. These measurements are providing new information about the processes influencing halogen and ozone levels in the tropical west Pacific, as well as the importance of trace-gas transport in convection for the upper troposphere and stratosphere. The FAAM aircraft made a total of 25 flights in the region between 1°S and 14°N and 130° and 155°E. It was used to sample at altitudes below 8 km, with much of the time spent in the marine boundary layer. It measured a range of chemical species and sampled extensively within the region of main inflow into the strong west Pacific convection. The CAST team also made ground-based measurements of a number of species (including daily ozonesondes) at the Atmospheric Radiation Measurement Program site on Manus Island, Papua New Guinea (2.1°S, 147.4°E). This article presents an overview of the CAST project, focusing on the design and operation of the west Pacific experiment. It additionally discusses some new developments in CAST, including flights of new instruments on board the Global Hawk in February–March 2015.

Open access