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An Evaluation of the Surface Radiation Budget Over North America for a Suite of Regional Climate Models Student: Marko Markovic Director: Colin Jones Université.

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Presentation on theme: "An Evaluation of the Surface Radiation Budget Over North America for a Suite of Regional Climate Models Student: Marko Markovic Director: Colin Jones Université."— Presentation transcript:

1 An Evaluation of the Surface Radiation Budget Over North America for a Suite of Regional Climate Models Student: Marko Markovic Director: Colin Jones Université du Québec à Montréal

2  Evaluate parameters of SRB (surface radiation budget) and cloud cover in RCMs against surface observations for North America.  The parameters which will be evaluated are: global solar (direct+diffuse), radiation, and downward longwave atmospheric radiation.  SW and LW are the main terms in surface energy balance that control evolution of surface temperature and moisture.  Three regional models used in this study are: 1.GEM-LAM - Limited version of GEM model, Canada (Coté et al.1998) 2. CRCM - The Canadian Regional Climate Model, (Caya and Laprise, 1999) 3. RCA3 - The Rossby Centre Regional Atmosphere model, Sweden (Jones et al.2004)  The observation data come from the NOAA SURFRAD network

3 Climatological mean annual cycle ( ). GEM-LAM and CRCM simulate ISR very well in winter while overestimate in summer with 20-30W/m2 biases. RCA3 is fairly accurate in summer but shows the biggest biases in winter and spring. DLR is underestimated by GEM-LAM and CRCM in winter while both models show good results for other seasons. This underestimate has already been seen by several studies in the past and is related to the parametrisation of water vapor spectra in winter conditions. CRCM gives a systematic underestimate of 20W/m2 through the entire annual cycle a possible cloud emissivity problem. PDF comparison Probability density functions of time series, period UTC, season DJF Clear Sky < 10 % of cloud cover Overcasted Sky > 90 % of cloud cover Shortwave: All-sky biases are mostly influenced by biases produced in overcast conditions. Longwave: Principal errors in all- sky conditions, for GEM-LAM and RCA3 come from clear-sky while for CRCM from cloudy-sky biases. All-sky Cloud Free Cloudy Comparison of Probability Density Function of Cloud Fraction Models overestimate clear-sky (0 - 10%), and underestimate occurrences of cloudy-sky (90-100%)

4 Differences between the models and ERA40, DJF 4-year mean, over entire N. America SW: GEM-LAM et MRCC good representation, RCA3 overestimates LW: underestimate by all models CC: underestimate by all models - Underestimate of LW downward atmospheric radiation in winter, by all models - Cancellations of errors in cloud coverage and in SW clear sky radiation in RCA3 model - Error in diurnal cycle of clouds in all models -Systematic underestimate of LW radiation in CRCM -DJF LW radiation biases are due to clear-sky radiation in GEM-LAM and RCA3, and cloudy-sky radiation fluxes in CRCM. -Comparison over entire N. America showed similar biases in respective models as in 6 SURFRAD station comparisons. Summary


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