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Summary: Asymmetry of Daily Temperature Records
YOSEF ASHKENAZY
Solar Energy and Environmental Physics, BIDR, Ben-Gurion University, Midreshet Ben-Gurion, Israel
YIZHAK FELIKS
Department of Mathematics, Israel Institute for Biological Research, Ness-Ziona, Israel
HEZI GILDOR
Environmental Sciences, Weizmann Institute, Rehovot, Israel
ELI TZIPERMAN
Department of Earth and Planetary Sciences, and Division of Engineering and Applied Sciences, Harvard University,
Cambridge, Massachusetts
(Manuscript received 30 October 2007, in final form 23 March 2008)
ABSTRACT
The authors study the NCEPNCAR reanalysis temperature records and find that surface daily mean
temperature cools rapidly and warms gradually at the midlatitudes (around 40°N and 40°S). This "asym-
metry" is partially related to the midlatitude cyclone activity, in which cold fronts are significantly faster and
steeper than warm fronts, and to intrusions of cold air. The gradual warming may be attributed also to the
radiative relaxation to average atmospheric conditions after the passage of cold fronts or other intrusions
of cold air. At the high latitudes there is an opposite asymmetry with rapid warming and gradual cooling;
this asymmetry may be attributed to the radiative relaxation to average cold atmospheric conditions after
the passage of warm fronts or intrusions of warm air.
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