oifii/ns-org/nsd/ar/sp/ratio/html_m - PowerPoint PPT Presentation

Stephane Poirier

Relation between AR-SP library code http://www.oifii.org/ns-org/nsd/ar/sp/ratio/html_m/ and Arnaud Mialon's chapter 2 figures (snowcover extent detection from SSM/I brightness temps.)

• AR-SP ratio library source code is a generalization from AR-AM ratio library
• AR-SP code is to be applied on both SMMR and SSM/I periods NSIDC's TBs.
• AR-AM code was designed and validated mostly to the SSM/I periods NSIDC's TBs.
• Currently uncertain if snow-free season is well localized in time when ratio library used with SMMR period TBs.

• Historically, only 2 seasons can be easily identified. A season where snow is present versus a season without any snow.
• Currently uncertain if summer start day (or winter end) and summer end day (or winter start) are well identified when ratio library used with SMMR period TBs.
• This presentation attempts to link the AR-SP ratio library source code lines implementing AR-AM ratio algorithms key concepts in order to validate and possibly improve the generalization.

• Following step 1, 2, 3 and 4 is step 5 where function calcul_moyecart() is called
• [moy_ete,ecart_ete,moy_hiver,ecart_hiver,seuil]=calcul_moyecart(zone,dataset,phase,pol,an,pathratio);
• The function calcul_moyecart() computes averages and standard deviations for both snowfree and snowcovered periods as well as a threshold

http://www.oifii.org/ns-org/nsd/ar/sp/ratio/html_m/calcul_moyecart.htmlhttp://www.oifii.org/ns-org/nsd/ar/sp/ratio/html_m/calcul_moyecart.html

• calcul_moyecart() can also be found at linkhttp://www.oifii.org/ns-org/nsd/ar/sp/ratio/html/calcul_moyecart.html(with line numbers and URLs for other matlab function names)
• For both SMMR and SSM/I periods, the threshold is set using the line seuil=moy_ete-2.*ecart_ete; (line numbers 158, 253, 300 and 379 )

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