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1 Modelled Meteorology - Applicability to Well-test Flaring Assessments Environment and Energy Division Alex Schutte Science & Community Environmental Knowledge Fund Forum and Workshop May 29 th, 2003

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

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3 Overview Modelled vs Measured Meteorological Data Best data for estimating impacts are measured data Would need significant amounts to cover every valley Modelled 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).

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The best is on-site observation of wind and temperature for a five year period Typically - one year observations at another location topography often very different and off- site weather (wind) not the same as that on the site Meteorology

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

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

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7 Approach Stage 3 - A few case studys using observed measurements vs the above results were assessed

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

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9 Upper Air Stations Western Canada is limited - Prince George - Fort Nelson

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10 SurfaceStations Environment Canada No wind data Forestry Historically no data collection in winter WLAP/Industry few long term records in areas of flaring activities

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11 Stage 1 Table RiverTumbler - Denison MM5 Observations

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12 Stage 1 - Conclusions MM5 data at a 20km resolution does not sufficiently resolve the wind field Finer resolution data may be able to resolve the winds however would require applying the model to a smaller area (More resources)

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13 Stage 2 Applied CALMET to a 1km Resolution Supplemented with actual meteorology except for the station of Interest Results were compared

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14 Stage 2 CALMET Extracted (Grid 21, 43) Wind Rose versus Rotated Top Actual Rotated (33 degrees) Bottom - Tumbler 1993-1994- CALMET Extraction for Grid Point (21,43)

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15 Stage 2 CALMET Extracted Grid Point (20,38) Wind Rose versus Rotated Tumbler Top Actual Rotated (55 degrees) Bottom - Tumbler 1993-1994- CALMET

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16 Illustration of 3-D Wind field

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

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18 Stage 3 Case Studies Current 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

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19 Stage 3 Model Results For 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.

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20 Model Illustration Data (Raw) Dir Ws 107.7000 0.5330 86.3000 0.7140 78.0000 1.7170 243.2300 0.4170 73.0000 0.0680 194.1100 1.4140 176.2000 5.4580 345.2000 0.5730 218.7700 1.9120 205.4600 1.4190 226.3000 1.8590 270.8000 2.6700 Calms to (1m/s) in ISC3, Dir- Wind Towards

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Straight-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. Current Shortcomings

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33 New Approach - Using CALMET/CALPUFF Among 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.

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34 Future Possibilities Evolve to the point where CALPUFF/CALMET is viable for all locations in addition to the study area Future 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 data Research better ways to site ambient monitors that do not rely on worst-case ambient predictions (e.g. wind prob. & direction, etc)

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