Presentation on theme: "OBSERVED ROBUSTNESS OF INTERANNUAL VARIABILITY OF OCTOBER EURASIAN SNOWCOVER AND ITS CLIMATE LINKAGE CanSISE conference, Victoria Yara Mohajerani May 9,"— Presentation transcript:
OBSERVED ROBUSTNESS OF INTERANNUAL VARIABILITY OF OCTOBER EURASIAN SNOWCOVER AND ITS CLIMATE LINKAGE CanSISE conference, Victoria Yara Mohajerani May 9, 2014
Outline Background Eurasian October snow and wintertime climate Snow cover datasets Evaluation of snow cover datasets Climate linkage Conclusion
Snow-Climate Connection Vast and highly variable snow cover Positive October snow anomaly negative AO phase in the following winter Effect of October snow on AO Cohen et al 2007, Figure 6, page 5342
Inconsistencies in snow data Known inconsistencies in snowcover data NOAA shows false positive trend NOAA widely used in climate- connection studies Snow Cover Extent Anomaly Brown and Derksen (2013) Figure 2, page 4
Project Overview 1. Validation and evaluation of satellite and reanalysis datasets against ground measurements (for ground station locations) Need global coverage, but can only validate data with local observations 2. Application of revised datasets to the issue of relationships between October Eurasian snow cover and northern hemisphere winter circulation (sea level pressure and free atmospheric geopotential) from 1980 to 2011.
Snow Cover Fraction (SCF) datasets Measurement TypeNameMonthly SCF Definition Reanalysis (based on ERAint temperature and precipitation) BROWN % of days in a month with ≥ 2cm snow depth Reanalysis MERRA % of days in a month with SWE ≥4mm Passive Microwave Satellite Measurements PMW % of days in a month with SWE ≥7.5mm Visible Satellite Measurements NOAA % of days in month that a cell has more than 50% snow covered Ground Measurements of snow depth over Russia RU % of days in a month with >=2 cm snow depth.
Snow climate connection discussion MERRA has weaker correlation than NOAA BROWN has very weak correlation Time frame matters: MERRA and NOAA more similar in JF than DJF
Conclusions Internal inconsistencies in NOAA: false positive trend MERRA and BROWN have best agreement with in- situ data (respectively) Dataset bias (NOAA) possible in previous climate linkage studies Relationship still evident between October Eurasian snow and wintertime circulation The extent of this relationship should be taken with caution due to inconsistencies in snowcover data
Acknowledgements Professor Paul J. Kushner Dr. Chris Derksen Dr. Ross Brown Centre for Global Change Science, University of Toronto The Canadian Sea Ice and Snow Evolution (CanSISE) Department of Physics, University of Toronto