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International Polar Year 2007–2008 - WMO

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150<br />

IPY 20 07–20 08<br />

vations obtained at Concordia were also compared to<br />

the results of IASI data retrievals. It was found that the<br />

problem of correct estimation of the surface temperature<br />

was the main limiting factor in the quality of IASI<br />

retrievals. A good prior estimation of skin temperature<br />

can be obtained using the radiative transfer equation<br />

together with IASI observations in a window channel.<br />

Results are presented in Fig. 2.1-11. In this figure, the<br />

skin temperature retrieved from a IASI window channel<br />

(blue line) is closer to the radiosounding surface<br />

temperature (black line) than the model skin temperature<br />

(red line) in terms of magnitude and time evolution.<br />

Based on this estimation of the skin temperature,<br />

retrievals have been performed over the same 44<br />

cases during Austral spring 2008, with an improved<br />

analysis of the temperature profile above Concordia<br />

compared to a retrieval using the model surface temperature.<br />

In parallel, innovative approaches have improved<br />

the use of microwave observations from the<br />

AMSU (Advanced Microwave Sounding Units) instruments<br />

by better description of the surface emissivity,<br />

which is highly variable in space and time (Guedj et<br />

al., 2010). These studies have highlighted the potential<br />

of satellite observations to contribute to a monitoring<br />

of weather and climate over the polar areas, once particular<br />

attention has been paid to surface parameters.<br />

Fig. 2.1-11. Skin<br />

temperature (K) at<br />

Concordia in austral<br />

spring 2008 (44 daily<br />

cases at 0000 UTC<br />

from October to 29<br />

November 2008)<br />

from model (red line),<br />

radiosounding (black<br />

line) and IASI window<br />

channel (blue line).<br />

(Graph: courtesy Aurelie<br />

Bouchard and Florence Rabier)<br />

Structure and Evolution of the <strong>Polar</strong><br />

Stratosphere and Mesosphere and Links to<br />

the Troposphere during IPY (SPARC-IPY, no.<br />

217) was to document the dynamics, chemistry<br />

and microphysical processes within the polar<br />

vortices during IPY, with a focus on the stratospheretroposphere<br />

and stratosphere-mesosphere coupling.<br />

One of the key outcomes was a collection of analysis<br />

products from several operational centres and several<br />

research centres, which was archived at the SPARC<br />

Data Center. The analysis products covered the period<br />

of IPY (March 2007 to March 2009) and represented the<br />

best available self-consistent approximations to the<br />

state of the atmosphere during this period (McFarlane<br />

et al., 2009; Farahani et al., 2009; Klecociuk et al., 2009).<br />

A major goal of the SPARC-IPY program was to<br />

document as completely as possible the dynamics and<br />

chemistry of the polar middle atmosphere during the<br />

IPY period. It was anticipated that achieving a unique<br />

synthesis of data on the polar middle atmosphere<br />

would require analysis of available research and<br />

operational satellite data, as well as ground-based<br />

and aircraft data. This would clearly include data<br />

from new measurement systems, as well as from<br />

enhanced measurement programs with established<br />

systems. The intent of SPARC-IPY, in cooperation with

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