Modelled Meteorology - Applicability to Well-test Flaring AssessmentsEnvironment and Energy Division

Alex SchutteScience & Community Environmental Knowledge FundForum and WorkshopMay 29th, 2003

Assessing Potential Impacts from FlaresObjective: To ensure adequate protection of the environment prior to emitting pollutants into the atmosphereIn mountainous terrain - Wind Speed and Wind Direction are the main factors affecting potential impacts.

OverviewModelled vs Measured Meteorological DataBest data for estimating impacts are measured data Would need significant amounts to cover every valleyModelled data can provide a potential worst case indication prior to the event Current WLAP Accepted Dispersion Models require meteorological data from one location and assume a uniform wind field (pollutants disperse in a straight line).

MeteorologyThe best is on-site observation of wind and temperature for a five year periodTypically - one year observations at another locationtopography often very different and off-site weather (wind) not the same as that on the site

LEVELTON ENGINEERING LTD.

ObjectiveResearch compared meteorological model outputs with independent site measurements to assess the accuracy of substituting modelled meteorological data for in situ observations

ApproachStage 1 - The Mesoscale Model Version 5 (MM5) Prognostic meteorological model was compared for use in current modelsStage 2 - The output from MM5 was then coupled with a Diagnostic meteorological model (CALMET) and the resultant meteorological fields similarly assessed.

ApproachStage 3 - A few case studys using observed measurements vs the above results were assessed

ClimateLong term Wind Speed and Direction Data available at 4 stations in Northern BC- PG, FSJ, Beatton River, Fort Nelson

Upper AirStationsWestern Canada is limited- Prince George- Fort Nelson

Surface StationsEnvironment Canada No wind dataForestry Historically no data collection in winterWLAP/Industry few long term records in areas of flaring activities

Stage 1Table RiverTumbler - DenisonMM5Observations

Stage 1 - ConclusionsMM5 data at a 20km resolution does not sufficiently resolve the wind fieldFiner resolution data may be able to resolve the winds however would require applying the model to a smaller area (More resources)

Stage 2Applied CALMET to a 1km ResolutionSupplemented with actual meteorology except for the station of InterestResults were compared

Stage 2CALMET Extracted (Grid 21, 43) Wind Rose versus Rotated

Top Actual Rotated (33 degrees) Bottom - Tumbler 1993-1994- CALMET Extraction for Grid Point (21,43)

Stage 2CALMET Extracted Grid Point (20,38) Wind Rose versus Rotated Tumbler

Top Actual Rotated (55 degrees) Bottom - Tumbler 1993-1994- CALMET

Illustration of 3-D Wind field

Stage 2 - Summary CALMET wind fields are more realistic than the current assumed uniform wind fieldsA 1km resolution was sufficient to provide a reasonable representationPrognostic (MM5) or UBC (MC2) data should be used as input to the modelAvoids the straight impact limitation in ISC3

Stage 3 Case StudiesCurrent Regulatory Requirements: No in situ meteorological data use surrogate station. Both ISC and RTDM must be run and combined into one set of model outputs.Protocols focus on worst-case concentrations

Stage 3 Model ResultsFor each case, WLAP methods were applied and then the CALMET/CALPUFF methods were applied.Results produced similar maximum worst case concentrations neither model indicated a propensity to be higher or lower.The spatial distribution of concentrations were different.

Model Illustration Data (Raw) Dir Ws 107.7000 0.5330 86.3000 0.7140 78.0000 1.7170243.2300 0.4170 73.0000 0.0680 194.1100 1.4140176.2000 5.4580345.2000 0.5730218.7700 1.9120205.4600 1.4190226.3000 1.8590270.8000 2.6700Calms to (1m/s) in ISC3, Dir- Wind Towards

LEVELTON ENGINEERING LTD.

Current ShortcomingsStraight-line Gaussian models assume instantaneous dispersion for the hour with a uniform wind field.When used to predict concentrations, if meteorology is not local, results can be meaningless.Even if local meteorology is used, results may not be valid - too much reg. focus on max.Model predictions may indicate unlikely high concentrations in unlikely locations affects how others may conduct monitoring.

LEVELTON ENGINEERING LTD.

New Approach - Using CALMET/CALPUFFAmong other conclusions in the report:It is a viable approach that can act as a substitute for collecting long-term meteorological data in the region.Using a modelled refined data set eliminates the subjectivity of applying/rotating other data sets. Large modelling domains can be created one time for many flaring locations. Limited by the availability of prognostic data to a fine enough resolution.

Future PossibilitiesEvolve to the point where CALPUFF/CALMET is viable for all locations in addition to the study areaFuture Research (perhaps joint with UBC) to evaluate refined data sets (eg. 1km), and perhaps even use as real meteorology?Evaluate how the more meaningful results compare with ambient sampling, based on actual dataResearch better ways to site ambient monitors that do not rely on worst-case ambient predictions (e.g. wind prob. & direction, etc)

This is from analysis of flaring impacts. You know all about this.Use of balloon for upper air data. You can indicate that this has been used for analysis of flaring impacts, but also has other applications. We have also installed and operated for prolonged periods a Sonic Detection and Ranging System for meterological data to 300m altitude. The system was installed in a mountainous area in Norther BC and used to assess air quality impacts.