Transcript ATM525Summary - University at Albany

Stratosphere-Troposphere
Coupling and Links with
Eurasian Land Surface
Variability
Cohen et. al, 2007: Journal of Climate, 20, 5335-5343
Adam Turchioe 2 Dec 2013 ATM 525
Introduction
• Stratosphere-Troposphere annular-mode events are
always preceded by an anomalous lower-stratospheric
planetary wave activity flux, but lower-tropospheric
wave activity signatures of these events are more
difficult to find
• Difficulty is due to the variability of the troposphere
in relation to the variability to the stratosphere
• Goal to use these precursors to improve long-term
forecasts
Method
 Uses three metrics to diagnose relationship:
1. Wave Activity Flux:
2. October Eurasian snowcover extent
 Uses the Robinson/NSIDC dataset
3. January SLP
 NCEP/NCAR Reanalysis Data
Conclusion
• December WAF has a strong center of action over a
sector extending from eastern Europe to eastern Asia
• This corresponds to the climatologically greatest
variance in October snow extent
• The January SLP strongly resembles the Arctic
Oscillation (AO)
• The strong relationship (R=0.79, 0.77) between the
WAF/SLP and Oct Snow/SLP shows tropospheric
conditions can be used to predict stratospheric 
tropospheric interactions weeks to months in advance
2013
2013
 2013 has had a phenomenally fast start to snowfall
growth.
 Total Eurasian snow cover extent is well above the
30-year climatological norm
 Results with AO correlation have shown there is a
MUCH greater importance with snow growth east
of 70°E than west.
 Notice how the last 3 weeks of October Asian snow
cover anomaly tailed off dramatically, as seen in
the weekly 2013 snow anomaly maps:
Week 38
2013 vs 10-Year Avg
Sept 23
Week 39
2013 vs 10-Year Avg
Sept 30
Week 40
2013 vs 10-Year Avg
Oct 07
Week 41
2013 vs 10-Year Avg
Oct 14
Week 42
2013 vs 10-Year Avg
Oct 21
Week 43
2013 vs 10-Year Avg
Oct 28
Week 44
2013 vs 10-Year Avg
Nov 04
2013
 As a result, any early snowfall positive anomaly was
greatly offset by a very benign rate of increase of
snowfall
 Also, in order to finalize the remaining slope, used the
current 2-week snowfall projection and visually
identified the year that most closely matched the
expected snowfall pattern (which turned out to be
2002)
 Thus, the 2013 Snow Growth Parameter Index number
is 0.816
 Where does this rank vs other years?
2013
 Once again, this is still very new research and the firstever use of this index as a predictor
 However, with statistically significant correlation values,
this year’s winter appears to be headed towards a
positive AO state
 Will continue to monitor daily snowfall and verify that
2002 is a good analog year for the next two weeks
 Will continue working on getting this index to use the
daily snowfall data
 Thank you!
Adam Turchioe
University at Albany
1600 Washington Ave Albany, New York 12203
[email protected]
630.337.1999