The relationship between northern hemisphere winter blocking and tropical modes of variability.

Gollan, Gereon and Greatbatch, Richard John (2017) The relationship between northern hemisphere winter blocking and tropical modes of variability. Open Access Journal of Climate, 30 (22). pp. 9321-9337. DOI 10.1175/JCLI-D-16-0742.1.

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In the present study, the influence of some major tropical modes of variability on northern hemisphere regional blocking frequency variability during boreal winter is investigated. Reanalysis data and an ensemble experiment with the ECMWF model using relaxation towards the ERA-Interim reanalysis data inside the tropics are used. The tropical modes under investigation are El Niño Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO) and the upper tropospheric equatorial zonal-mean zonal wind . An early (late) MJO phase refers to the part of the MJO cycle when enhanced (suppressed) precipitation occurs over the western Indian Ocean and suppressed (enhanced) precipitation occurs over the Maritime Continent and the western tropical Pacific. Over the North Pacific sector, it is found that enhanced (suppressed) high latitude blocking occurs in association with El Niño (La Niña) events, late (early) MJO phases and westerly (easterly) . Over central to southern Europe and the east Atlantic, it is found that late MJO phases, as well as a suppressed MJO are leading to enhanced blocking frequency. Furthermore, early (late) MJO phases are followed by blocking anomalies over the western North Atlantic region, similar to those associated with a positive (negative) North Atlantic Oscillation. Over northern Europe, the easterly (westerly) phase of is associated with enhanced (suppressed) blocking. These results are largely confirmed by both the reanalysis and the model experiment.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Kiel University
Refereed: Yes
Open Access Journal?: No
Publisher: AMS (American Meteorological Society)
Related URLs:
Projects: MiKlip2, MODINI, ATMOS-MODINI, Opendap
Date Deposited: 11 Oct 2017 08:13
Last Modified: 04 Aug 2020 09:19

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