NOCN03 CWAO 181810 GENOT TLTP. NO. 004 MIDDLE ATMOSPHERIC EXTENSION (STRATOSPHERE AND MESOSPHERE) OF THE GLOBAL AND REGIONAL FORECAST SYSTEMS OF THE CANADIAN METEOROLOGICAL CENTRE ON JUNE 22 2009 THE CANADIAN METEOROLOGICAL CENTRE (CMC) WILL IMPLEMENT IMPORTANT CHANGES TO THE GLOBAL AND REGIONAL FORECAST SYSTEMS STARTING WITH THE 1200 UTC RUNS. THESE CHANGES, MAINLY RELATED TO THE RAISING OF THE MODEL LID FROM 10 HPA (32 KM) TO 0.1 HPA (64 KM) IN BOTH THE GLOBAL AND REGIONAL SYSTEMS, AND TO THE ADDITION OF NEW PHYSICAL PARAMETERIZATION SCHEMES IN THE GLOBAL SYSTEM, WILL LEAD TO IMPROVEMENTS IN THE FORECASTS, ESPECIALLY AT LEAD TIMES OF 3 TO 6 DAYS IN THE GLOBAL FORECAST SYSTEM. 1. OVERVIEW OF CHANGES 1.1 CHANGES INVOLVING BOTH THE GLOBAL AND REGIONAL MODELS A. MODEL LID ELEVATED TO 0.1 HPA (64 KM) THE SIGMA-LIKE VERTICAL COORDINATE, ALSO CALLED ETA COORDINATE AT CMC, HAS BEEN REPLACED BY A NEW HYBRID COORDINATE. AT THE SAME TIME THE NUMBER OF MODEL LEVELS HAS BEEN INCREASED FROM 58 TO 80 AND THE MODEL LID HAS BEEN RAISED FROM 10 HPA (32 KM) TO 0.1 HPA (64KM). RAISING THE MODEL LID LEADS TO A SIGNIFICANT IMPROVEMENT IN FORECASTS IN THE STRATOSPHERE AT ALL LEAD-TIMES. THE POSITIVE IMPACT IS ALSO SEEN INTO THE TROPOSPHERE, ESPECIALLY FOR THE GLOBAL FORECAST SYSTEM AT LEAD-TIMES OF 3 TO 6 DAYS. B. NON-OROGRAPHIC GRAVITY WAVE DRAG SCHEME A SCHEME REPRESENTING THE EFFECTS OF SUB-GRID SCALE GRAVITY WAVES FROM NON-OROGRAPHIC SOURCES HAS BEEN IMPLEMENTED IN THE NEW SYSTEM. IT HAS A POSITIVE IMPACT ON WINDS IN THE MIDDLE ATMOSPHERE. THIS SCHEME IS DESCRIBED IN HINES (1997). 1.2 CHANGES INVOLVING ONLY THE GLOBAL MODEL A. NEW RADIATIVE TRANSFER SCHEME A NEW INFRARED AND SOLAR RADIATIVE TRANSFER PARAMETERIZATION SCHEME, MORE COMPREHENSIVE AND ACCURATE THAN THE PREVIOUS ONE, IS BEING IMPLEMENTED. IT IS DESCRIBED IN LI AND BARKER (2005). THIS NEW RADIATION SCHEME WILL RESULT IN A GENERAL IMPROVEMENT IN TEMPERATURE FORECASTS IN THE TROPOSPHERE. THE SAME SCHEME HAS ALREADY BEEN IMPLEMENTED IN THE REGIONAL MODEL IN MARCH 2009 WITH SIMILAR RESULTS. 1.3 CHANGES TO BOTH GLOBAL AND REGIONAL DATA ASSIMILATION A. NEW DATA THE VERTICAL EXTENSION OF THE MODEL DOMAIN ALLOWS FOR THE ASSIMILATION OF DATA THAT COULD NOT BE INCLUDED PREVIOUSLY IN THE ANALYSIS. THAT IS THE CASE FOR SOME ATOVS AMSU-A CHANNELS AND SOME GPS RADIO OCCULTATION (GPSRO) DATA. A.1 ATOVS AMSU-A CHANNELS 11-14 THESE CHANNELS HAVE A PEAK IMPACT AT APPROXIMATELY 20, 10, 5 AND 3 HPA, BUT INFLUENCE THE ANALYSIS AT LEVELS AS LOW AS 250 HPA AND AS HIGH AS THE MODEL LID. AS IN THE CURRENT OPERATIONAL ASSIMILATION SYSTEMS, ATOVS AMSU-A DATA ARE USED FROM NOAA-15, NOAA-16, NOAA-18 AND AQUA SATELLITES. THE EXTRA CHANNELS REPRESENT AN INCREASE OF 75 PERCENT IN AMSU-A DATA AND ARE THE PRIMARY SOURCE OF INFORMATION IN THE STRATOSPHERE. A DIRECT IMPACT OF THE HIGHER MODEL LID IS TO IMPROVE THE ASSIMILATION OF CHANNELS 9-10 THAT WAS PREVIOUSLY IMPAIRED BY MODELLING ERROR NEAR THE MODEL LID. THE DYNAMICAL RADIANCE BIAS CORRECTION SCHEME NOW USES FOUR PREDICTORS FOR AMSU-A RATHER THAN TWO. ALSO, AMSU-A CHANNELS 11-14 ARE ASSIMILATED USING A STATIC BIAS CORRECTION PROCEDURE TO AVOID A DRIFT IN RADIANCE INNOVATION (OBSERVED MINUS FORECAST O-F)BIAS ENCOUNTERED DURING R AND D EXPERIMENTATION. A.2 GPSRO AS IN THE CURRENT OPERATIONAL SYSTEM, REFRACTIVITY PROFILES ARE ASSIMILATED FROM GPSRO DATA. THE ASSIMILATED PROFILES EXTEND FROM 1 KM ABOVE GROUND TO 40 KM COMPARED TO 1 KM TO 30 KM PREVIOUSLY. THIS REPRESENTS A 35 PERCENT INCREASE IN THE NUMBER OF GPSRO DATA INGESTED INTO THE NEW SYSTEM. B. NEW OBSERVATION AND BACKGROUND ERROR STATISTICS TO ALLOW COMPUTATION OF ANALYSIS INCREMENTS ON THE 80 MODEL LEVELS, NEW BACKGROUND-ERROR STATISTICS WERE COMPILED USING FORECASTS FROM THE NEW MODEL AND THE SO-CALLED NMC METHOD. THE ASSIMILATION SYSTEM INCLUDES A MODIFIED APPROACH THAT ALLOWS FOR VERTICAL RESTRICTION OF THE IMPACT FROM OBSERVATIONS. GENERALLY, OBSERVATION-ERROR STATISTICS ARE UNCHANGED EXCEPT FOR THE SPECIFICATION OF THE NEWLY ASSIMILATED AMSU-A CHANNELS 11-14 AND THE REDUCTION OF ERROR OF AMSU-A CHANNELS 9-10 THAT WAS PREVIOUSLY SET ARTIFICIALLY HIGH TO COMPENSATE FOR MODELLING ERROR NEAR THE MODEL LID. 2. PERFORMANCE EVALUATION THE NEW GLOBAL AND REGIONAL FORECAST SYSTEMS WERE TESTED EXTENSIVELY. MANY CYCLES EACH COVERING AT LEAST TWO SUMMER MONTHS AND TWO WINTER MONTHS WERE PERFORMED AND EVALUATED DURING THE DEVELOPMENT PHASE. THE NEW SYSTEMS WERE ALSO RUN IN PARALLEL WITH THE OPERATIONAL SYSTEMS SINCE MARCH (GLOBAL) AND APRIL (REGIONAL) 2009. THE OUPUTS OF THE PARALLEL SYSTEMS WERE ALSO VERIFIED AGAINST ANALYSES AND AGAINST OBSERVATIONS. THEY WERE ALSO EVALUATED ON A DAILY BASIS BY OPERATIONAL METEOROLOGISTS. 2.1 OBJECTIVE EVALUATION A. GLOBAL FORECAST SYSTEM OBJECTIVE VERIFICATIONS AGAINST RADIOSONDE DATA SHOWS A VERY SIGNIFICANT IMPROVEMENT IN THE STRATOSPHERE ABOVE 150 HPA, AT ALL FORECAST LEAD-TIMES, WITH CONSISTENT IMPROVEMENT NOTED THROUGHOUT THE TROPOSPHERE. THIS IS GENERALLY TRUE FOR ALL SEASONS TESTED, FOR ALL REGIONS AND VARIABLES. THE BIAS FOR TEMPERATURE (GEOPOTENTIAL) IS GENERALLY IMPROVED AT ALL FORECAST LEAD-TIMES EXCEPT IN THE TROPICS AT MID-TROPOSPHERIC LEVELS WHERE THE COLD (LOW) BIAS SLIGHTLY INCREASES. FURTHERMORE THE LARGE BIASES IN THE ZONAL COMPONENTS OF THE WIND IN THE LOWER STRATOSPHERE ARE GENERALLY GREATLY REDUCED. TROPICAL CYCLONE STATISTICS AS PREDICTED BY THE NEW GLOBAL MODEL WERE COMPARED TO THAT OF THE CURRENT OPERATIONAL MODEL FOR THE 2007 HURRICANE SEASON. A REDUCTION IN FREQUENCY OF FALSE ALARMS OF TROPICAL CYCLONES WAS OBSERVED FOR MEDIUM RANGE FORECASTS OVER THE ATLANTIC BASIN. VERIFICATIONS AGAINST ANALYSES SHOW IMPROVED ANOMALY CORRELATIONS FOR THE TEMPERATURE AND GEOPOTENTIAL, AND GENERALLY REDUCED WIND RMS ERRORS IN THE TROPOSPHERE AT ALL FORECAST RANGES. A WARMING OF SURFACE TEMPERATURES IN BOTH HEMISPHERES IS OBSERVED WHEN COMPARING THE NEW SYSTEM WITH THE ONE IT REPLACES. THIS WARMING INCREASES TOWARDS THE POLES AND IS MORE SIGNIFICANT IN WINTER THAN IN SUMMER. IT IS RELATED TO THE INTRODUCTION OF THE NEW RADIATION PACKAGE. A GENERAL REDUCTION OF THE CURRENT MODEL COLD BIAS IS OBTAINED OVER MOST OF NORTH AMERICA. HOWEVER, IN CERTAIN PARTS OF NORTHERN CANADA, A SLIGHT WARM BIAS MAY RESULT. QPF VERIFICATION SHOWS THE CHANGE TO BE NEUTRAL OVER NORTH AMERICA FOR BOTH SUMMER AND WINTER TEST PERIODS. B. REGIONAL FORECAST SYSTEM OBJECTIVE VERIFICATIONS AGAINST RADIOSONDE DATA INDICATE LARGE IMPROVEMENTS ABOVE 150 HPA IN THE STRATOSPHERE. THE IMPACTS WERE FOUND TO BE NEUTRAL OR SLIGHTLY POSITIVE IN THE TROPOSPHERE. SURFACE FIELDS WERE NOT SIGNIFICANTLY AFFECTED THIS TIME, AS THE NEW RADIATIVE SCHEME HAD ALREADY BEEN IMPLEMENTED IN THE REGIONAL MODEL IN MARCH 2009. 2.2 SUBJECTIVE EVALUATION A. GLOBAL FORECAST SYSTEM OPERATIONAL FORECASTERS SUBJECTIVELY COMPARED THE TWO SYSTEMS OVER NORTH AMERICA AND ADJACENT WATERS DURING A PARALLEL RUN. THE PROPOSED SYSTEM SHOWED A GENERAL IMPROVEMENT OVER THE EXISTING ONE DURING THE EVALUATION PERIOD, RECOGNIZABLY BETTER FOR THE GEOPOTENTIAL AT 500 HPA THAN FOR SEA LEVEL PRESSURE, WITH SOME GAINS NOTED TOO FOR THE QPF. THE IMPROVEMENT GREW WITH INCREASING FORECAST LEAD-TIME, REACHING A MAXIMUM AT DAYS 4 AND 5. ON A REGIONAL BASIS, THE IMPROVEMENT APPEARS TO BE THE GREATEST FOR CENTRAL NORTH AMERICA, THE PACIFIC COAST AND NORTH PACIFIC OCEAN AREAS, AND THE LEAST OVER THE ARCTIC. DIFFERENCES WERE NOTED DURING THE SUBJECTIVE EVALUATION FOR SEVERAL FIELDS IN RELATION TO THE RADIATIVE SCHEME AT 0000Z AND 1200Z VERIFICATION TIMES. FOR EXAMPLE, THE NEW SYSTEM DISPLAYS WARMER SURFACE TEMPERATURES OVER THE ENTIRE ARCTIC OCEAN AND ADJACENT LANDMASS NORTH OF THE ARCTIC CIRCLE AT 0000Z AND 1200Z, WHICH WERE JUDGED TO DIMINISH THE QUALITY OF THE FORECAST. ON THE OTHER HAND THE NEW SYSTEM FORECASTS WARMER SURFACE TEMPERATURES OVER MOST OF NORTH AMERICA AT 1200Z WHICH IMPROVES THE FORECAST, AND PARTIALLY CORRECTS A KNOWN NIGHTTIME COLD BIAS OBSERVED IN THE CURRENT SYSTEM. AN IMPROVEMENT HAS BEEN SEEN IN THE FORECAST AT 3 TO 5 DAYS LEAD-TIME IN THE TRAJECTORY OF LOWS AFFECTING ATLANTIC CANADA AND THE BERING SEA. THIS IMPROVEMENT COULD SHOW UP AS WELL OVER OTHER REGIONS FOR DIFFERENT SEASONS. ALTHOUGH THIS PARALLEL RUN DID NOT COINCIDE WITH THE PEAK OF THE HURRICANE SEASON, THE SUBJECTIVE EVALUATION SUGGESTS THAT THE NEW SYSTEM WILL NOT OVERFORECAST TROPICAL STORMS AS MUCH AS THE EXISTING GLOBAL SYSTEM. B. REGIONAL FORECAST SYSTEM DURING THE PARALLEL RUN EVALUATION, OPERATIONAL FORECASTERS NOTED SOME GAINS IN THE QUALITY OF THE MASS FIELDS ACROSS ALL THE REGIONS UNDER EVALUATION EXCEPT THE ARCTIC WHERE THE EFFECT WAS NEUTRAL. 3. IMPACTS ON OPERATIONAL PRODUCTS AND OTHER FORECAST SYSTEMS 3.1 GENERAL IMPACTS FOR ALL RELATED FORECAST SYSTEMS USING THE OUTPUT FIELDS OF EITHER THE REGIONAL OR THE GLOBAL MODEL, SUCH AS UMOS, SCRIBE, AND THE WAVE MODELS (WAM), IMPROVEMENTS ARE EXPECTED TO BE PROPORTIONAL TO THOSE SEEN IN EACH OF THE REGIONAL AND GLOBAL FORECAST SYSTEMS. THE UMOS SYSTEM APPLIED TO THE GLOBAL MODEL TEMPERATURE OUTPUT HAS BEEN RETRAINED. NO SUCH RETRAINING WAS NECESSARY FOR THE REGIONAL UMOS SYSTEM SINCE THIS WAS DONE ALREADY WHEN THE NEW RADIATIVE SCHEME WAS IMPLEMENTED IN THE REGIONAL MODEL. 3.2 IMPACT ON THE AIR QUALITY MODEL (CHRONOS) THE CHRONOS AIR QUALITY MODEL WAS RUN IN PARALLEL USING THE OUTPUT FIELDS FROM THE NEW REGIONAL MODEL AS THE DRIVING METEOROLOGICAL FIELDS. BECAUSE THESE FIELDS ARE THE RESULT OF AN INTERPOLATION FROM THE NEW HYBRID LEVELS TO THE OLDER ETA LEVELS, A SLIGHT DETERIORATION IN THE OBJECTIVE SCORES WAS NOTED WITH THE PARALLEL CHRONOS RUN BUT NO SIGNIFICANT DIVERGENCE OCCURED THROUGHOUT THE EVALUATION PERIOD. THIS IS A TEMPORARY SITUATION IN VIEW OF IMPROVEMENTS TO THE AIR QUALITY PREDICTION SYSTEM PLANNED FOR LATER THIS SUMMER. 3.3 IMPACT ON THE GLOBAL ENSEMBLE PREDICTION SYSTEM (EPS) DETAILS REGARDING THE IMPACT ON THE EPS AS A RESULT OF THESE CHANGES TO THE GLOBAL FORECAST SYSTEM ALONG WITH ADDITIONAL CHANGES MADE TO THE CMC EPS SYSTEMS ARE DESCRIBED IN A SEPARATE GENOT. 4. TIME OF AVAILABILITY OF PRODUCTS PRODUCTS FROM THE GLOBAL AND REGIONAL MODEL WILL BE PRODUCED ABOUT 10 MINUTES LATER THAN THEIR PRESENT TIME OF PRODUCTION. CMC IS CONTINUING ITS EFFORTS TO REDUCE THESE DELAYS. FOR SPECIFIC QUESTIONS CONCERNING THIS IMPLEMENTATION, YOU CAN WRITE TO: PRODUCTION-INFO(AT)CMC.EC.GC.CA GRIMES ADMA - MSC / SMA - SMC TORONTO