Seasonal Winter Forecasts of the Northern Stratosphere and Troposphere: Results from JMA Seasonal Hindcast Experiments

Seasonal Winter Forecasts of the Northern Stratosphere and Troposphere: Results from JMA Seasonal... AbstractThis study investigates winter forecasts of the Northern stratosphere and troposphere using seasonal hindcast experiments of the Japan Meteorological Agency. A main focus is placed on the seasonal forecasts of December-January-February (DJF)-mean Northern Annular Mode (NAM) when the forecasts are initialized in late fall. Results demonstrate that the hindcast data have significant skill for both ensemble mean and category forecasts of the NAM but only in the stratosphere. Probability forecasts for DJF Major Stratospheric Sudden Warmings (MSSWs) are also suggested to be significant (higher probabilities for actual MSSW years) near the 90 % confidence level. The forecast skill of the stratospheric NAM changes with the observed phase of the Quasi-Biennial Oscillation (QBO), although the QBO is not simulated but is only included in initial conditions. The skill is higher for the easterly phase characterized by hits of negative NAM states (weaker than normal polar vortex), whereas it is lower for the westerly phase reflecting misses of positive NAM states. It is finally shown that a verification score for category forecasts of the stratospheric and tropospheric NAM tends to co-vary as a whole. The tropospheric forecast skill is significant when the stratosphere has large NAM anomalies in the real world and they are well forecasted. In contrast, the tropospheric forecasts are sometimes poor when the stratospheric forecasts fail to capture observed NAM conditions. It is speculated that stratospheric and tropospheric forecasts could be improved together through the stratosphere-troposphere coupling for such cases, i.e., by successfully forecasting anomalous vortex states in the stratosphere. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Seasonal Winter Forecasts of the Northern Stratosphere and Troposphere: Results from JMA Seasonal Hindcast Experiments

Loading next page...
 
/lp/ams/seasonal-winter-forecasts-of-the-northern-stratosphere-and-troposphere-zHzROTFDQk
Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
D.O.I.
10.1175/JAS-D-17-0276.1
Publisher site
See Article on Publisher Site

Abstract

AbstractThis study investigates winter forecasts of the Northern stratosphere and troposphere using seasonal hindcast experiments of the Japan Meteorological Agency. A main focus is placed on the seasonal forecasts of December-January-February (DJF)-mean Northern Annular Mode (NAM) when the forecasts are initialized in late fall. Results demonstrate that the hindcast data have significant skill for both ensemble mean and category forecasts of the NAM but only in the stratosphere. Probability forecasts for DJF Major Stratospheric Sudden Warmings (MSSWs) are also suggested to be significant (higher probabilities for actual MSSW years) near the 90 % confidence level. The forecast skill of the stratospheric NAM changes with the observed phase of the Quasi-Biennial Oscillation (QBO), although the QBO is not simulated but is only included in initial conditions. The skill is higher for the easterly phase characterized by hits of negative NAM states (weaker than normal polar vortex), whereas it is lower for the westerly phase reflecting misses of positive NAM states. It is finally shown that a verification score for category forecasts of the stratospheric and tropospheric NAM tends to co-vary as a whole. The tropospheric forecast skill is significant when the stratosphere has large NAM anomalies in the real world and they are well forecasted. In contrast, the tropospheric forecasts are sometimes poor when the stratospheric forecasts fail to capture observed NAM conditions. It is speculated that stratospheric and tropospheric forecasts could be improved together through the stratosphere-troposphere coupling for such cases, i.e., by successfully forecasting anomalous vortex states in the stratosphere.

Journal

Journal of the Atmospheric SciencesAmerican Meteorological Society

Published: Jan 9, 2018

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off