Re: NAO-Index

From: Adam Phillips <asphilli_at_nyahnyahspammersnyahnyah>
Date: Fri Jun 28 2013 - 16:07:24 MDT

Hi Lena,
See this page from the Climate Data Guide here:
https://climatedataguide.ucar.edu/guidance/hurrell-north-atlantic-oscillation-nao-index-station-based

Specifically, refer to the Technical Notes section of the page, under
"Winter (Dec-Mar) Station-Based NAO Index", you'll see the following
paragraph:

"The SLP anomalies at each station were normalized by division of each
seasonal mean pressure by the long-term mean (1864-1983) standard
deviation. Normalization is used to avoid the series being dominated by
the greater variability of the northern station."

Thus, you could use dim_standardize_n_Wrap to standardize each station,
then subtract the northern station from the southern station. It is your
choice as to what the standardization period should be. The above
referenced site chooses 1864-1983, but you could alternatively use the
entire record.

Hope that helps..
Adam

On 06/28/2013 02:16 PM, Lena Frey wrote:
> Hi,
> I have made sensitivity studies with ECHAM5. Now I would like to
> calculate the NAO-Index. First I have calculated the sea level
> pressure at two stations.
> ; surface pressure
> aps = in->aps_ave(:,:,:)
> tm1 = in->tm1_ave(:,:,:,:)
> press = in->press_ave(:,:,:,:)
> phis = geofile->GEOSP(:,:)
>
> ;**********************************************************************
> ; claculate sea level pressure at two points
> ;**********************************************************************
> ; sea level pressure at Akureyri
>
> slp1 = pslec(tm1(:,30,:,:),phis,aps,press(:,30,:,:))
> copy_VarMeta(aps,slp1)
> slp1@long_name = "Sea Level Pressure"
> printVarSummary(slp1)
> slp1 = lonFlip(slp1)
> printVarSummary(slp1)
> slp1_ave = slp1(:,{65.7},{-18.1})
> slp1_seas = month_to_season(slp1_ave,season)
> nyrs = dimsizes(slp1_seas&time)
> printVarSummary(slp1_seas)
> ; sea level pressure at Ponta Delgada
>
> slp2 = pslec(tm1(:,30,:,:),phis,aps,press(:,30,:,:))
> copy_VarMeta(aps,slp2)
> slp2@long_name = "Sea Level Pressure"
> printVarSummary(slp2)
> slp2 = lonFlip(slp2)
> printVarSummary(slp2)
> slp2_ave = slp2(:,{65.7},{-18.1})
> slp2_seas = month_to_season(slp2_ave,season)
> nyrs = dimsizes(slp2_seas&time)
> printVarSummary(slp2_seas)
> How can I calculate the NAO-Index with ncl?
> Thanks.
> Lena
>
>
>
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-- 
______________________________________________________________
Adam Phillips                                asphilli@ucar.edu
NCAR/Climate and Global Dynamics Division       (303) 497-1726
P.O. Box 3000				
Boulder, CO 80307-3000    http://www.cgd.ucar.edu/cas/asphilli

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Received on Fri Jun 28 16:07:32 2013

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