Class: SimpleMetarParser::Temperature

Inherits:
Base
  • Object
show all
Defined in:
lib/simple_metar_parser/metar/temperature.rb

Instance Attribute Summary collapse

Attributes inherited from Base

#parent

Instance Method Summary collapse

Methods inherited from Base

#initialize

Constructor Details

This class inherits a constructor from SimpleMetarParser::Base

Instance Attribute Details

#dew ⇒ Object (readonly)

Dew temperature



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 16

def dew
  @dew
end

#humidity ⇒ Object (readonly)

Relative humidity



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 19

def humidity
  @humidity
end

#temperature ⇒ Object (readonly) Also known as: degrees

Temperature in C



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 12

def temperature
  @temperature
end

#wind_chill ⇒ Object (readonly)

Wind chill index



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 22

def wind_chill
  @wind_chill
end

#wind_chill_us ⇒ Object (readonly)

US Wind chill index



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 25

def wind_chill_us
  @wind_chill_us
end

Instance Method Details

#calculate_humidity ⇒ Object 



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 62

def calculate_humidity
  # Calculate relative humidity
  return if self.temperature.nil? or self.dew.nil?

  # http://github.com/brandonh/ruby-metar/blob/master/lib/metar.rb
  # http://www.faqs.org/faqs/meteorology/temp-dewpoint/

  es0 = 6.11 # hPa
  t0 = 273.15 # kelvin
  td = self.dew + t0 # kelvin
  t = self.temperature + t0 # kelvin
  lv = 2500000 # joules/kg
  rv = 461.5 # joules*kelvin/kg
  e = es0 * Math::exp(lv/rv * (1.0/t0 - 1.0/td))
  es = es0 * Math::exp(lv/rv * (1.0/t0 - 1.0/t))
  rh = 100 * e/es

  @humidity = rh.round
end

#calculate_wind_chill ⇒ Object 



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 82

def calculate_wind_chill
  return if self.temperature.nil? or self.parent.wind.wind_speed.nil?
  return if self.temperature > 10 or self.parent.wind.wind_speed_kmh < 4.8

  # http://en.wikipedia.org/wiki/Wind_chill
  v = self.parent.wind.wind_speed
  ta = self.temperature

  @wind_chill_us = 13.12 +
    0.6215 * ta -
    11.37 * v +
    0.3965 * ta * v

  @wind_chill = (10.0 * Math.sqrt(v) - v + 10.5)*(33.0 - ta)
end

#decode_split(s) ⇒ Object 



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 27

def decode_split(s)
  # Temperature in Celsius degrees
  if s =~ /^(M?)(\d{2})\/(M?)(\d{2})$/
    if $1 == "M"
      @temperature = -1.0 * $2.to_f
    else
      @temperature = $2.to_f
    end

    if $3 == "M"
      @dew = -1.0 * $4.to_f
    else
      @dew = $4.to_f
    end

    return
  end

  # shorter version
  if s =~ /^(M?)(\d{2})\/$/
    if $1 == "M"
      @temperature = -1.0 * $2.to_f
    else
      @temperature = $2.to_f
    end

    return
  end
end

#post_process ⇒ Object 



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 57

def post_process
  calculate_humidity
  calculate_wind_chill
end

#reset ⇒ Object 



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# File 'lib/simple_metar_parser/metar/temperature.rb', line 6

def reset
  @temperature = nil
  @dew = nil
end