Temporal characteristics of heat waves and cold spells and their links to overly persistent atmospheric circulation in EURO-CORDEX RCMs

0491677 - ÚFA 2019 DE eng A - Abstract
Plavcová, Eva - Kyselý, Jan
Temporal characteristics of heat waves and cold spells and their links to overly persistent atmospheric circulation in EURO-CORDEX RCMs.
Geophysical Research Abstracts. Vol. 20. Göttingen: European Geosciences Union, 2018. EGU2018-4367-1. E-ISSN 1607-7962.
[EGU General Assembly 2018. 08.04.2018-13.04.2018, Vienna]
Institutional support: RVO:68378289
Keywords : heat waves * cold spells * regional climate model (RCM) * reanalyses * atmospheric circulation
OECD category: Climatic research
https://meetingorganizer.copernicus.org/EGU2018/EGU2018-6641.pdf

We study links between atmospheric circulation and summer heat waves/winter cold spells in an ensemble
of EURO-CORDEX RCMs in Central Europe. Evaluation of 23 model simulations allowed us to analyse the
influence of the RCM formulation as well as of the driving data (the ERA-INTERIM re-analysis and 4 different
GCMs), and the role of the spatial resolution (0.11deg and 0.44deg). Model results were compared against
observations over the reference period of 1980–2005. Atmospheric circulation was represented by circulation
indices derived from daily gridded mean sea level pressure data, and by circulation types/supertypes derived from
the indices. We examine observed and simulated temporal characteristics of hot and cold days
and heat waves and cold spells, focusing on their links to the persistence of atmospheric circulation, especially those circulation types significantly conducive
to heat waves and cold spells.
Although the RCMs reproduce the frequency of heat waves and cold spells relatively well, they have a tendency
to produce longer than observed heat waves and cold spells, leading to extremely long
heat waves or cold spells. The RCMs have a tendency to produce more days in cold spells per season than observed. All models simulate a winter season with a larger number of cold days/days in cold spells than in any season observed.
The RCMs reproduce in general the observed circulation significantly conducive to heat waves and cold spells.
Zonal flow reduces the probability of temperature extremes in both seasons, and more easterly flow days in a
season are linked to a higher number of cold spell days. Prolonged temperature extremes (both heat waves and
cold spells) are primarily linked to easterly/southeasterly circulation. For almost all simulations and
all circulation supertypes, there is a significant overestimation of the mean length of sequences of supertypes
in summer. Model simulations also strongly overestimate the mean length of westerly flow in winter.
Permanent Link: http://hdl.handle.net/11104/0285324