ENVE5103 Lecture 4b Meteorological Data for Refined Models

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ENVE5103 Lecture 4b Meteorological Data for
Refined Models

• Specific Meteorology as the key to refined
  modelling
• Surface and upper air data
• Meteorological data pre-processor programs

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• Recall the tiered approach to modelling for
  regulatory compliance
• Tier 1 screening level analysis - all potential
  worst case meteorological conditions.
• Tier 2 refined modelling with regional
  meteorological data.
• Tier 3 refined modelling with local
  meteorological data. This data typically must be
  pre-processed by the modeller or a Canadian
  meteorological data provider such as Environment
  Canada.

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Meteorological conditions considered in SCREEN

• Wind speed and stability class combinations used
  by SCREEN

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Atmosphere near the Earths Surface

• Free atmosphere (no velocity gradients)
• Planetary Boundary layer (PBL)
• Ekman layer up to 300-500 m
• Wind speed increases rapidly with height, slowing
  as the free atmosphere is approached
• wind direction turns clockwise with height
  (Northern Hemisphere)
• Surface layer up to 30-50 m
• Vertical turbulent heat and momentum fluxes are
  assumed constant with height

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Meteorological Measurements

• Surface Data
• Wind direction (wind vane at surface, pilot
  balloons and tetroons aloft)
• Wind speed (cup anemometer or hot-wire
  anemometer)
• Wind turbulence (bivane, u-v-w anemometer)
• Solar radiation actinometer
• Upper air data
• Temperature profile (wiresonde, dropsonde,
  radiosonde)
• Mixing height

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Hourly Surface Data

• Hourly surface data is supported in several
  formats including
• 1. CD-144 NCDC Surface Data Table 6.1 lists
  the data contained in the CD-144 file format.
• 2. MET-144 SCRAM Surface Data The SCRAM
  surface data format is a reduced version of the
  CD-144 data with fewer weather variables.
• 3. SAMSON Surface Data The SAMSON data contains
  all of the required meteorological variables for
  concentration, dry and wet particle deposition,
  and wet vapor deposition.

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http//www.ene.gov.on.ca/envision/air/regulations/
metdata/met.htm
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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Station number 61060

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• yymmddhh

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Ceiling height (hundreds of feet)

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Wind direction (tens of degrees)

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Wind speed (knots, i.e. nautical miles per hour)
• 1 knot 1.852 km/h
• 0.514 m/s

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Dry bulb temperature, (F)

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Total cloud cover (tens of percent)

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• Beginning of hourly surface data file for Ottawa
  (SCRAM met data)
• Opaque cloud cover (tens of percent)

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Mixing Height and Upper Air Data

• Upper air data, also known as mixing height data,
  are required for refined modelling with the
  ISC-PRIME models. It is recommended that only
  years with complete mixing height data be used.
  In some instances, mixing height data may need to
  be obtained from more than one station to
  complete multiple years of data.

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U.S. mean mixing heights, winter, (hundreds of
meters)
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MET DATA PREPROCESSORS

• AERMET and PCRAMMET are meteorological data
  preprocessor appropriate to the modelling in
  AERMOD and ISC respectively.
• They take as input, the computer files that
  record hourly surface and upper air data and
  determine/compute parameters that describe the
  atmosphere in the respective model formulation

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Meteorological Data ProcessingPCRAMMET

• Calculate hourly values for atmospheric stability
  from meteorological surface observations
• Interpolate twice daily mixing heights to hourly
  values
• Optionally, calculate the parameters for dry and
  wet deposition processes
• Output data in a format required by regulatory
  dispersion models

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Beginning of Ottawa upper air data
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AERMOD DATASETS PROCESSED WITH AERMET Urban
surface profile for eastern Region (Ottawa,
Peterborough, Belleville)
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AERMET Surface File output Coordinates
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AERMET Surface File output Upper air and
surface data station identification
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AERMET Surface File output Year, month, day
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AERMET Surface File output Julian day
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AERMET Surface File output Hour
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AERMET Surface File output H, sensible heat flux
(W/m2), a parameter in AERMOD
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AERMET Surface File output Additional parameters
required by AERMOD
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AERMET Surface file records