NOCN03 CWAO 061415 GENOT TLTP. NO. 002 IMPROVEMENT TO THE GLOBAL DATA ASSIMILATION SYSTEM AND TO THE REGIONAL DATA ASSIMILATION AND FORECAST SYSTEM OF THE CANADIAN METEOROLOGICAL CENTRE STARTING ON MARCH 11 AT 06UTC, THE CANADIAN METEOROLOGICAL CENTRE WILL IMPLEMENT CHANGES TO THE GLOBAL AND REGIONAL DATA ASSIMILATION SYSTEMS FOR INCORPORATING NEW DATA. FURTHERMORE, THE GEM MODEL OF REGIONAL DATA ASSIMILATION AND FORECAST SYSTEM WILL BE IMPROVED BY USING A NEW RADIATIVE TRANSFER SCHEME AND BY EXTENDING ITS UNIFORM-RESOLUTION CORE GRID TO BETTER COVER THE ARCTIC REGIONS. 1.1 OVERVIEW OF CHANGES INVOLVING BOTH GLOBAL AND REGIONAL DATA ASSIMILATION SYSTEMS A. GPS RADIO OCCULTATION (GPSRO) DATA A.1 DESCRIPTION OF MODIFICATIONS GPSRO DATA OBTAINED FROM THE SIX COSMIC SATELLITES WILL BE ASSIMILATED BY THE GLOBAL AND REGIONAL ASSIMILATION SYSTEMS. THESE ARE REFRACTIVITY PROFILES OBTAINED FROM PROCESSING GPS MEASUREMENTS FROM RECEIVERS ONBOARD THE SIX SATELLITES. REFRACTIVITY CAN BE DIRECTLY LINKED TO TEMPERATURE AND MOISTURE. ABOUT 600 REFRACTIVITY PROFILES ARE OBTAINED PER 6 HOUR PERIOD. THE DATA ARE USED FROM ABOUT 1 KM ABOVE GROUND, UP TO 30 KM. PROFILES ARE ALSO AVAILABLE FROM OTHER SATELLITES (GRACE, CHAMP AND METOP) BUT THESE WILL BE ADDED SHORTLY. THE CHANGES WILL BE PORTED ON THE GLOBAL 4D-VAR VARIATIONAL ASSIMILATION SYSTEM AND THE REGIONAL 3D-VAR ASSIMILATION SYSTEM. THEY WILL BE INCORPORATED INTO THE ENSEMBLE KALMAN FILTER FOR THE ENSEMBLE PREDICTION SYSTEM AT A LATER DATE. THE GEM MODEL ITSELF USED IN THE GLOBAL SYSTEM REMAINS UNCHANGED. A.2 IMPACTS THIS CHANGE REPRESENTS A SIGNIFICANT INCREASE IN THE AMOUNT OF TEMPERATURE PROFILE DATA. ITS IMPACT IS MULTIPLE. GPSRO DATA ARE KNOWN TO HAVE VERY LITTLE BIASES AND TO EXCEL AT DETECTING THE LOCATION OF THE TROPOPAUSE. DURING THE TESTS WE HAVE NOTED IMPROVEMENTS PARTICULARLY ABOVE 300 HPA, BOTH IN TERMS OF THE FIRST GUESS FIT AND ANALYSES FIT TO RADIOSONDE DATA. THIS IS PARTICULARLY TRUE IN THE SOUTHERN HEMISPHERE BUT WAS NOTED IN ALL AREAS. ANOTHER SIGNIFICANT IMPACT OF THESE SUPPLEMENTAL OBSERVATIONS IS IN THE REDUCTION OF BIASES IN THE STRATOSPHERE, WHICH HAS AN IMPACT ON THE ASSIMILATION OF SATELLITE RADIANCE DATA SUCH AS AMSU AND AIRS. WE HAVE NOTED A READJUSTMENT OF THE BIAS CORRECTION NEEDED FOR THESE RADIANCE DATA. 1.2 OVERVIEW OF CHANGES INVOLVING ONLY THE GEM MODEL OF THE REGIONAL DATA ASSIMILATION AND FORECAST SYSTEMS A. NEW RADIATIVE TRANSFER SCHEME A.1 DESCRIPTION OF MODIFICATIONS THE PREVIOUS INFRARED AND SOLAR RADIATIVE TRANSFER PARAMETRIZATION HAS BEEN REPLACED BY AN ACCURATE AND MORE DETAILED NEW SCHEME THAT MAKES USE OF A CORRELATED K-DISTRIBUTION (CKD) METHOD DESCRIBED IN LI AND BARKER (2005). A.2 IMPACTS THE MAIN IMPACT OF THE NEW RADIATION SCHEME FOR SHORT TERM FORECASTS IS THE REDUCTION OF A KNOWN OVERALL COLD BIAS AT THE SURFACE. THE IMPLIED GENERAL WARMING WILL PRODUCE A DECREASE OF THE FREQUENCY OF STRONG COLD ERRORS. THIS EFFECT WILL BE GREATER THAN THE INCREASE IN FREQUENCY OF STRONG WARM ERRORS. IN WINTER, WARMING IS EXPECTED BOTH AT NIGHT AND DURING THE DAY. IN SUMMER, WARMING IS EXPECTED AT NIGHTTIME. B. POLAR EXTENSION OF THE UNIFORM-RESOLUTION CORE GRID B.1 DESCRIPTION OF MODIFICATIONS THE UNIFORM-RESOLUTION PORTION (CORE GRID) OF THE VARIABLE-RESOLUTION GRID HAS BEEN EXPANDED OVER THE ARCTIC REGIONS SO THAT IT NOW INCLUDES THE NORTH POLE AS WELL AS MOST OF THE ARCTIC OCEAN. THE HORIZONTAL RESOLUTION OF THE CORE GRID HAS NOT BEEN CHANGED AND STILL USES A 15-KM GRID SPACING. B.2 IMPACTS FINER DETAILS WILL BE SUPPORTED BY THE INCREASE OF RESOLUTION IN THE REGIONS OVER THE POLAR EXTENSION OF THE CORE GRID. THEREFORE, WEATHER SYSTEMS IMPACTING THE ARCTIC REGIONS AND ADJACENT REGIONS WILL BE BETTER ANALYSED AND FORECAST. BECAUSE OF THE GRID CHANGES, IT HAS BEEN NECESSARY TO REGENERATE THE GEOPHYSICAL FIELDS, SUCH AS THE LAND-SEA MASK, TOPOGRAPHY, SURFACE ROUGHNESS, VEGETATION TYPES AND OTHERS. THAT HAS BEEN PERFORMED USING AN UPGRADED GEOPHYSICAL DATABASE. SURFACE OR NEAR-SURFACE FIELDS OVER THE WHOLE GRID SHOULD BE IMPACTED POSITIVELY BY THESE NEW GEOPHYSICAL FIELDS. LOCAL EFFECTS CAN BE IMPORTANT WHERE A SIGNIFICANT CHANGE IN TOPOGRAPHY OR VEGETATION TYPE OCCURED. IN ADDITION, IT SHOULD BE NOTED THAT THE NEW AND THE OLD GRID POINTS ARE NOT COLLOCATED. AS A CONSEQUENCE, USERS WHO EXTRACT DATA FROM DIRECT MODEL OUTPUT MAY HAVE TO REVISE THEIR PROCEDURE, SUCH AS THE SELECTION OF A REPRESENTATIVE GRID POINT FOR A GIVEN LATITUDE/LONGITUDE LOCATION. 2. PERFORMANCE EVALUATION THE ADDITION OF THE NEW DATA IN THE ASSIMILATION SYSTEMS WAS TESTED EXTENSIVELY. MANY CYCLES EACH COVERING AT LEAST TWO SUMMER MONTHS (2006) AND TWO WINTER MONTHS (2006-2007) WERE DONE. FORTY REGIONAL TEST FORECASTS WERE MADE FOR EACH PERIOD. THE EVALUATION OF THE REGIONAL ASSIMILATION AND FORECAST SYSTEMS HAS BEEN PERFORMED WITH THE NEW GPSRO DATA ALONE AND ALSO IN COMBINATION WITH THE NEW GRID AND THE NEW RADIATIVE TRANSFER SCHEME. THE NEW SYSTEMS WERE ALSO TESTED IN PARALLEL RUNS SINCE THE BEGINNING OF NOVEMBER 2008. THE OUPUTS OF THE FORECAST SYSTEMS FOR THE TESTS WERE VERIFIED AGAINST OBSERVATIONS AND AGAINST ANALYSES. THE OUTPUTS OF THE PARALLEL RUNS WERE ALSO EVALUATED BY OPERATIONAL METEOROLOGISTS. 2.1 GLOBAL FORECAST MODEL EVALUATION OBJECTIVE VERIFICATION AGAINST RADIOSONDE DATA INDICATES A WEAK POSITIVE IMPACT IN THE NORTHERN HEMISPHERE AND A VERY POSITIVE ONE IN THE SOUTHERN HEMISPHERE, PARTICULARLY AT HIGHER LATITUDES. THE IMPACTS ARE ALSO MUCH LARGER ABOVE 300 HPA. VERIFICATION AGAINST ANALYSES SHOWS (ANOMALY CORRELATION) A GAIN IN PREDICTABILITY FROM 1 TO 6 HOURS BY DAY FIVE DEPENDING ON SEASON AND HEMISPHERE, WITH EVEN HIGHER GAINS IN THE STRATOSPHERE IN THE SOUTHERN HEMISPHERE. QPF VERIFICATION SHOWS THE CHANGE TO BE NEUTRAL OVER NORTH AMERICA. THESE CONCLUSIONS APPLY EQUALLY FOR SUMMER AND WINTER TEST CYCLES. OPERATIONAL FORECASTERS COMPARED OPERATIONAL AND PROPOSED MODEL DURING THE PARALLEL RUN FOR NORTH AMERICA. THE PARALLEL GLOBAL MODEL SHOWED ALSO A SMALL GAIN FOR MASS FIELDS ESPECIALLY FOR THE PACIFIC AND ATLANTIC SECTORS BUT NEUTRAL ELSEWHERE. THE SAME HOLDS FOR QPFS. 2.2 REGIONAL FORECAST MODEL EVALUATION EVEN IF THE NEW DATA IS INCORPORATED IN THE REGIONAL ASSIMILATION SYSTEM, THE EARLY CUT-OFF (T+2H05) OF THE RUN LEADS TO LESS NEW DATA BEING AVAILABLE. NONETHELESS OBJECTIVE VERIFICATION SHOWS A SLIGHT POSITIVE IMPACT ON MASS FIELDS AND A NEUTRAL IMPACT ON QPF. DURING THE PARALLEL RUN EVALUATION BY OPERATIONAL FORECASTERS CAME TO THE SAME CONCLUSION. GAINS IN THE MASS FIELDS ARE SMALL BUT ACROSS ALL THE EVALUATION REGIONS. THE NEGATIVE BIAS IN DIRECT SURFACE TEMPERATURE BIAS HAS BEEN DIMINISHED BUT A SMALL POSITIVE BIAS IS SEEN OVER THE ARCTIC DURING THE ARCTIC NIGHT. 3. IMPACTS ON SCRIBE THERE IS NO MAJOR IMPACT ON THE BIAS OF THE GLOBAL MODEL FIELDS. THERE IS HOWEVER AN IMPACT ON THE REGIONAL MODEL FIELDS DUE TO THE IMPROVED RADIATION SCHEME AND THE NEWER GEOPHYSICAL FIELDS. THEREFORE THE UMOS SYSTEM FOR THE REGIONAL SYSTEM HAS BEEN RETRAINED. AS A CONSEQUENCE THE IMPACT OF THE ABOVE CHANGES ON SCRIBE WILL BE SMALL. 4. TIME OF AVAILABILITY OF PRODUCTS PRODUCTS FROM THE REGIONAL MODEL MAY BE PRODUCED ABOUT 5 MINUTES LATER THAN THEIR PRESENT TIME OF PRODUCTION. FOR MORE DETAILS PLEASE REFER TO THE TECHNICAL NOTE ON THIS TOPIC THAT WILL SOON BE MADE AVAILABLE AT: HTTP://WWW.SMC.EC.GC.CA/CMC/OP_SYSTEMS/RECENT_E.HTML FOR SPECIFIC QUESTIONS CONCERNING THIS IMPLEMENTATION, YOU CAN WRITE TO: PRODUCTION-INFO(AT)CMC.EC.GC.CA GRIMES ADMA - MSC / SMA - SMC TORONTO