Characteristics of target areas selected by the ensemble transform Kalman filter for medium-range forecasts of high-impact winter weather

Sharanya J. Majumdar, Kathryn J. Sellwood, Daniel Hodyss, Z. Tóth, Yucheng Song

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The characteristics of "target" locations of tropospheric wind and temperature identified by a modified version of the ensemble transform Kalman filter (ETKF), in order to reduce 0-7-day forecast errors over North America, are explored from the perspective of a field program planner. Twenty cases of potential high-impact weather over the continent were investigated, using a 145-member ensemble comprising perturbations from NCEP, ECMWF, and the Canadian Meteorological Centre (CMC). Multiple targets were found to exist in the midlatitude storm track. In half of the cases, distinctive targets could be traced upstream near Japan at lead times of 4-7 days. In these cases, the flow was predominantly zonal and a coherent Rossby wave packet was present over the northern Pacific Ocean. The targets at the longest lead times were often located within propagating areas of baroclinic energy conversion far up-stream. As the lead time was reduced, these targets were found to diminish in importance, with downstream targets corresponding to a separate synoptic system gaining in prominence. This shift in optimal targets is sometimes consistent with the radiation of ageostrophic geopotential fluxes and transfer of eddy kinetic energy downstream, associated with downstream baroclinic development. Concurrently, multiple targets arise due to spurious long-distance correlations in the ETKF. The targets were least coherent in blocked flows, in which the ETKF is known to be least reliable. The effectiveness of targeting in the medium range requires evaluation, using data such as those collected during the winter phase of The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Field Campaign (T-PARC) in 2009.

Original languageEnglish
Pages (from-to)2803-2824
Number of pages22
JournalMonthly Weather Review
Volume138
Issue number7
DOIs
Publication statusPublished - Jul 2010

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Kalman filter
transform
weather
winter
storm track
Rossby wave
geopotential
kinetic energy
targeting
eddy
perturbation
ocean
forecast
experiment
temperature

ASJC Scopus subject areas

  • Atmospheric Science

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Characteristics of target areas selected by the ensemble transform Kalman filter for medium-range forecasts of high-impact winter weather. / Majumdar, Sharanya J.; Sellwood, Kathryn J.; Hodyss, Daniel; Tóth, Z.; Song, Yucheng.

In: Monthly Weather Review, Vol. 138, No. 7, 07.2010, p. 2803-2824.

Research output: Contribution to journalArticle

Majumdar, Sharanya J. ; Sellwood, Kathryn J. ; Hodyss, Daniel ; Tóth, Z. ; Song, Yucheng. / Characteristics of target areas selected by the ensemble transform Kalman filter for medium-range forecasts of high-impact winter weather. In: Monthly Weather Review. 2010 ; Vol. 138, No. 7. pp. 2803-2824.
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