Search Results

You are looking at 41 - 42 of 42 items for

  • Author or Editor: David Karoly x
  • Refine by Access: All Content x
Clear All Modify Search
William Randel
,
Petra Udelhofen
,
Eric Fleming
,
Marvin Geller
,
Mel Gelman
,
Kevin Hamilton
,
David Karoly
,
Dave Ortland
,
Steve Pawson
,
Richard Swinbank
,
Fei Wu
,
Mark Baldwin
,
Marie-Lise Chanin
,
Philippe Keckhut
,
Karin Labitzke
,
Ellis Remsberg
,
Adrian Simmons
, and
Dong Wu

Abstract

An updated assessment of uncertainties in “observed” climatological winds and temperatures in the middle atmosphere (over altitudes ∼10–80 km) is provided by detailed intercomparisons of contemporary and historic datasets. These datasets include global meteorological analyses and assimilations, climatologies derived from research satellite measurements, historical reference atmosphere circulation statistics, rocketsonde wind and temperature data, and lidar temperature measurements. The comparisons focus on a few basic circulation statistics (temperatures and zonal winds), with special attention given to tropical variability. Notable differences are found between analyses for temperatures near the tropical tropopause and polar lower stratosphere, temperatures near the global stratopause, and zonal winds throughout the Tropics. Comparisons of historical reference atmosphere and rocketsonde temperatures with more recent global analyses show the influence of decadal-scale cooling of the stratosphere and mesosphere. Detailed comparisons of the tropical semiannual oscillation (SAO) and quasi- biennial oscillation (QBO) show large differences in amplitude between analyses; recent data assimilation schemes show the best agreement with equatorial radiosonde, rocket, and satellite data.

Full access

Decadal Prediction

Can It Be Skillful?

Gerald A. Meehl
,
Lisa Goddard
,
James Murphy
,
Ronald J. Stouffer
,
George Boer
,
Gokhan Danabasoglu
,
Keith Dixon
,
Marco A. Giorgetta
,
Arthur M. Greene
,
Ed Hawkins
,
Gabriele Hegerl
,
David Karoly
,
Noel Keenlyside
,
Masahide Kimoto
,
Ben Kirtman
,
Antonio Navarra
,
Roger Pulwarty
,
Doug Smith
,
Detlef Stammer
, and
Timothy Stockdale

A new field of study, “decadal prediction,” is emerging in climate science. Decadal prediction lies between seasonal/interannual forecasting and longer-term climate change projections, and focuses on time-evolving regional climate conditions over the next 10–30 yr. Numerous assessments of climate information user needs have identified this time scale as being important to infrastructure planners, water resource managers, and many others. It is central to the information portfolio required to adapt effectively to and through climatic changes. At least three factors influence time-evolving regional climate at the decadal time scale: 1) climate change commitment (further warming as the coupled climate system comes into adjustment with increases of greenhouse gases that have already occurred), 2) external forcing, particularly from future increases of greenhouse gases and recovery of the ozone hole, and 3) internally generated variability. Some decadal prediction skill has been demonstrated to arise from the first two of these factors, and there is evidence that initialized coupled climate models can capture mechanisms of internally generated decadal climate variations, thus increasing predictive skill globally and particularly regionally. Several methods have been proposed for initializing global coupled climate models for decadal predictions, all of which involve global time-evolving three-dimensional ocean data, including temperature and salinity. An experimental framework to address decadal predictability/prediction is described in this paper and has been incorporated into the coordinated Coupled Model Intercomparison Model, phase 5 (CMIP5) experiments, some of which will be assessed for the IPCC Fifth Assessment Report (AR5). These experiments will likely guide work in this emerging field over the next 5 yr.

Full access