swiss alpine snow variability: its links to large scale flow patterns
DESCRIPTION
Swiss Alpine snow variability: Its links to large scale flow patterns. ICAM-MAP meeting, Brig (CH) Fri 23 th May 2003 Simon C. Scherrer C. Appenzeller Federal Office of Meteorology and Climatology (MeteoSwiss), Switzerland [email protected]. Swiss snow variability. Klosters 1999 (GR). - PowerPoint PPT PresentationTRANSCRIPT
Swiss Alpine snow variability:Its links to large scale flow patterns
ICAM-MAP meeting, Brig (CH)
Fri 23th May 2003
Simon C. Scherrer C. Appenzeller
Federal Office of Meteorology and Climatology
(MeteoSwiss), Switzerland
Swiss new snow - NAO: direct influence
Argument:There is a NAO – Alpine snow relation, dependent on height and has an impact on trends
Question:Is there a pronounced NAO influence on Swiss new snow variability and trends?
1931-1999
New Swiss new snow data set
A new roughly homogenous snow data set (1931(57)-1999)
89 stakes
France
Germany
Austria
ItalyA
LP S
46°N
48°N
6°E 11°E
Swiss DJF new snow sums: EOF 2
15% (sign.)r = 1
r = 0.30
r = -1
r = -0.30
No trend
Swiss DJF new snow sums: EOF 3
8% (sign.)r = 1
r = 0.30
r = -1
r = -0.30
small trend
EOF 3 shows a distinct height dependence
New snow EOF‘s: height dependence
Alt
itu
de
[m
a.s
.l.]
2500
0
1500
r~-0.6
Correlation coefficient
1000
500
2000
DJF EOF– NAOI relation
r (PC1, NAOI) = -0.24 r (PC2, NAOI) = -0.29 r (PC3, NAOI) = -0.57**
Trend PC 3
not significant (p=0.22)
Correlation maps: SLP – (new snow PC3)
SLPPattern 3:
„NAO like“
SVD 3:SCF: 5%r = 0.70
SVD 1: European and Hemispheric view
SVD 1HN - SLP
Swiss Alpine region
4
- 4mbar
1
- 1
SVD 1 resembles NAO/AO like pattern on hemispheric scale
NAO/AO – blocking relation?
Hemispheric scale:
„European“ scale:
seems to be determined by central European high-pressure regime or low-pressure
Influence of “blocking”
based on standard TM Blocking Index modified central latitude
NAO-
NAO+
Atlantic ocean
Sw
iss
Alp
s
Atlantic ocean
Sw
iss
Alp
s
60°N 50°NNAO+
NAO-
DJF
“bl
ocki
ng”
freq
uenc
y
DJF
“bl
ocki
ng”
freq
uenc
y
Conclusions
Three distinct DJF new snow patterns are identified (expl. var. 81%)
There is no simple 1:1 relation between DJF new snow and the NAOI
The direct influence of the NAO on DJF new snow sums: is expressed as low-station high-station pattern (expl. variance ~8%) shows a distinct trend since the 1960‘s
The primary DJF new snow variability: is locally driven by central European high-low pressure (blocking?) is NAO/AO like on a hemispheric scale
The “Blocking” – NAO relation is ambiguous: Atlantic “blocking” is negatively correlated with the NAOI Middle-European “blocking” is positively correlated with the NAOI
Intermediate conclusions
Three “significant” DJF new snow patterns are identified, which explain 81% of total variability
There is no simple 1:1 relation between Swiss Alpine new snow sums and the NAOI
The direct influence of the NAO on new snow sums: is expressed as a low – high station pattern (8% var.) shows a distinct trend since the 1960‘s
