**[March 4 2009 Attribution Conf. Call Summary:]{.underline}**

***Items for Next cc, and Research Opportunities***

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Participants:

M. Halpert (verification of DJF CPC fcst)

M. Hoerling K. Weickman

T. Xu T. Zhang

J. Eischeid K. Wolter

J Perlwitz

The CSI Team focused most of its discussion on the following issues:

1.  ***Explaining the 2008 US coolness***

2.  ***A major stratospheric warming event in January 2009***

3.  ***NDJ 2009: Impact of global and regional SST anomalies***

4.  ***Verifying the DJF CPC winter outlook.***

**[On the 2008 Coolness]{.underline}**

° Important to distinguish the "natural" from the "anthropogenic" states
of world oceans in a) realtime monitoring, b) attribution, c) prediction

° NOAA CSI is using 2008 as a "test-bed" case to estimate the intensity
of

"natural internal SSTs" and "GHG externaly forced SSTs"

° NOAA CSI is focusing also on 2008 US cool sfcT conditions (-0.16°C)

\-\-\-- what was the GHG boundary forced signal?

Estimate \~ +0.6°C

\-\-\-- what was the natural internal SST boundary forced signal?

Estimate \~ +0.4°C

\-\-\-- what was the natural internal atmospheric contribution?

Estimate \~ -1.2°C

° 2008 US coolness seems to have been "highly unusual" since the
expected

anomaly, given SST and GHG boundary forcings was \~ +1°C

\-\-\-- we estimate a \> 2 std atmospheric internal event (i.e.,
unrelated to

GHG or SST forcing) was the principal cause for the coolness.

\-\-\-- The residual US sfcT for 2008, computed after removing the

estimated boundary forced signals, resembled 1917 US sfcT....the

coldest US annual sfcT on record (since 1895).

**[On the Sudden Stratospheric Warming (SSW) Event over the
NH]{.underline}**

° One of the strongest events in the past 30 years.

° As expected, attributable to waves driven from the troposphere,

especially a strong PNA-like wave amplification in mid-January.

° The subsequent 45-day evolution of stratospheric and tropospheric

conditions mostly follows the composite picture of Baldwin and

Thompson.

° The SSW event appears to have contributed to subsequent extreme cold

event in western Europe, though little evidence for impacts on US.

**[On NDJ 2009 US conditions: The impact of SST
conditions]{.underline}**

° The "La Nina" event is seen to be particuarly strong upon removing the

estimated GHG signal in NDJ 2008 SST conditions.

° 150-member AMIP (obs global SSTs) confirm a dry US response along

the southern tier of states in NDJ 2009. The signal was almost entirely

due to tropical SST forcing, based on "TOGA" runs.

° Plans to re-run simulations for 2008, forced with the residual SST

anomalies computed after removing the estimated GHG signal.

**[On verification of DJF 2009 US CPC predictions]{.underline}**

° Positive skill for US sfcT and pcpn.

° SfcT skill was lower than the historical skill of CPC fcts, in part
owing

to unanticipated widespread cold conditions over the Great

Lakes/northern Ohio Valley. We wish to understand the role of snow

cover feedback in those cold conditions.

° Pcpn skill was comparable to sfcT skill, having captured the dry
signal

along the southern US.

° The need to better understand the boundary forcings, and the manner in

which the signals attributal to them could be used to improve
predictions,

was discussed.

° NOAA CSI will conduct new SST

simulations for DJF 2009 to assess the role of OBS DJF SSTs, with and

without GHG component. It intends to compare these with the NOAA

coupled model predictions for DJF 2009.