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Ann. Geophys., 26, 1287-1297, 2008
www.ann-geophys.net/26/1287/2008/
© European Geosciences Union 2008
On the observed changes in upper stratospheric and mesospheric temperatures from UARS HALOE
E. Remsberg
Science Directorate, NASA Langley Research Ctr., Hampton, VA, USA
Abstract. Temperature versus pressure or T(p) time series from the
Halogen Occultation Experiment (HALOE) of the Upper Atmosphere Research
Satellite (UARS) have been extended and re-analyzed for the period of
1991–2005 and for the upper stratosphere and mesosphere in 10-degree wide
latitude zones from 60 S to 60 N. Even though sampling from a solar
occultation experiment is somewhat limited, it is shown to be quite adequate
for developing both the seasonal and longer-term variations in T(p).
Multiple linear regression (MLR) techniques were used in the re-analyses for
the seasonal and the significant interannual, solar cycle (SC-like or
decadal-scale), and linear trend terms. Plots of the amplitudes and phases
for the interannual (QBO and subbiennial) terms are provided. A simple
SC-like term of 11-yr period was fitted to the time series residuals after
accounting for the seasonal and interannual terms. Highly significant
SC-like responses were found for both the upper mesosphere and the upper
stratosphere. The phases of these SC-like terms were checked for their
continuity with latitude and pressure-altitude; the larger amplitude
responses are directly in-phase with that of standard proxies for the solar
flux variations. The analyzed, max minus min, responses at low latitudes are
of order 0.5 to 1 K, while at middle latitudes they are as large as 3 K in
the upper mesosphere. Highly significant, linear cooling trends were found
at middle latitudes of the middle to upper mesosphere (−1.5 to −2.0 K/decade),
at tropical latitudes of the lower mesosphere (about −0.5 K/decade), and at 2 hPa
(of order −1 K/decade). Both the diagnosed solar
cycle responses and trends from HALOE for the mid to upper mesosphere at
middle latitudes are larger than simulated with most models, perhaps an
indication of decadal-scale dynamical forcings that are not being simulated
so well.
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