This class is used to calculate a variety of quantities related to the earth's atmosphere, such as refractivity, saturated pressure, and pathlength (refractivity integrated through the atmosphere). More...

#include <carma/services/Atmosphere.h>

Public Types
enum	dewPointMethodEnum { CLAUSIUS_CLAPEYRON, MAGNUS_TETENS, HOFFMAN_WELCH }

typedef enum carma::services::Atmosphere::dewPointMethodEnum	dewPointMethodType

Public Member Functions
	Atmosphere ()
	no-arg constructor More...

double	computeDewPoint (double airTemp, double relHumid, dewPointMethodType method=CLAUSIUS_CLAPEYRON) const
	The dewpoint temperature defines the temperature to which a parcel of air would need to be cooled at constant pressure and constant moisture content in order for the vapor pressure and saturation vapor pressure of the parcel to be equal. More...

double	computeHorizonPathlength (double airTemp, double atmPressure, double relHumid, double frequency) const
	Calculate the maximum possible pathlength, toward the horizon. More...

double	computeHumidity (double airTemp, double dewTemp, dewPointMethodType method=CLAUSIUS_CLAPEYRON) const
	The relative humidity is computed from the ambient and dew point temperatures. More...

double	computePathlength (double airTemp, double atmPressure, double relHumid, double elevation, double frequency, double altitude=0.0) const

double	computeRefractionCorrection (double airTemp, double atmPressure, double relHumid, double elevation, double frequency, double altitude) const
	Compute the refraction pointing correction, given the in vacuo elevation and weather parameters. More...

double	computeSaturatedPressure (double airTemp) const
	The surface saturated water vapor pressure is used in the calculation of the refractivity. More...

double	computeZenithRefractivity (double airTemp, double atmPressure, double relHumid, double frequency) const
	The refractivity, N_O, at zenith. More...

bool	isConsistentDewPoint (services::Temperature dewPoint, services::Temperature airTemp, double relHumid, dewPointMethodType method=CLAUSIUS_CLAPEYRON, double consistencyPercent=10.0)
	Check that a given dewPoint value is consistent with its paired ambient air temperature and relative humidity. More...

carma::services::Temperature	lastSafeAirTemperature (double airTemp)
	This method checks if the input air temperature is safe and if so saves and returns the value. More...

carma::services::Temperature	lastSafeAirTemperature (carma::services::Temperature airTemp)
	This method checks if the input air temperature is safe and if so saves and returns the value. More...

carma::services::Temperature	lastSafeAirTemperature () const

carma::services::Pressure	lastSafeAtmPressure (double atmPressure)
	This method checks if the input atmospheric pressure is safe and if so saves and returns the value. More...

carma::services::Pressure	lastSafeAtmPressure (carma::services::Pressure atmPressure)
	This method checks if the input atmospheric pressure is safe and if so saves and returns the value. More...

carma::services::Pressure	lastSafeAtmPressure () const

carma::services::Temperature	lastSafeDewPoint (double dewPoint)
	This method checks if the input dew point is safe and if so saves and returns the value. More...

carma::services::Temperature	lastSafeDewPoint (carma::services::Temperature dewPoint)
	This method checks if the input dew point is safe and if so saves and returns the value. More...

carma::services::Temperature	lastSafeDewPoint () const

double	lastSafeRelativeHumidity (double relHumid)
	This method checks if the input relative humidity is safe and if so saves and returns the value. More...

double	lastSafeRelativeHumidity () const

double	ulichRefractionCorrection (double airTemp, double atmPressure, double relHumid, double elevation, double frequency) const
	This is to test against the Ulich (1981) radio refraction formulation NOTE: RADIO ONLY. More...

double	waterColumn (double airTemp, double relHumid) const
	The water column is derived from the water vapor density and an assumed scaleheight for the wet atmosphere (assumed to be about 2.1km) More...

double	waterPartialPressure (double airTemp, double relHumid) const
	Compute the partial pressure of water given the ambient air temperature and relative humidity. More...

double	waterVaporDensity (double airTemp, double relHumid) const
	The water vapor density is derived from the relative humidity and saturated pressure, and is the amount of water in the atmosphere. More...

virtual	~Atmosphere ()
	destructor More...

Static Public Member Functions
static bool	isSafeAirTemperature (double airTemp)

static bool	isSafeAirTemperature (carma::services::Temperature airTemp)

static bool	isSafeAtmPressure (double atmPressure)

static bool	isSafeAtmPressure (carma::services::Pressure atmPressure)

static bool	isSafeDewPoint (double dewPoint)

static bool	isSafeDewPoint (carma::services::Temperature dewPoint)

static bool	isSafeElevation (double elevation)

static bool	isSafeElevation (carma::services::Angle elevation)

static bool	isSafeRelativeHumidity (double relHumid)

static bool	isSafeWindSpeed (carma::services::Velocity windSpeed)

static bool	isSafeWindSpeed (double windSpeed)

static double	safeAirTemperature (double airTemp)
	This method is meant to check that a given air temperature is within reasonable bounds for the CARMA site. More...

static carma::services::Temperature	safeAirTemperature (carma::services::Temperature airTemp)
	This method is meant to check that a given air temperature is within reasonable bounds for the CARMA site. More...

static double	safeAtmPressure (double atmPressure)
	This method is meant to check that a given atmospheric pressure is within reasonable bounds for the CARMA site. More...

static carma::services::Pressure	safeAtmPressure (carma::services::Pressure atmPressure)
	This method is meant to check that a given atmospheric pressure is within reasonable bounds for the CARMA site. More...

static double	safeDewPoint (double dewPoint)
	This method is meant to check that a given dew point temperature is within reasonable bounds for the CARMA site. More...

static carma::services::Temperature	safeDewPoint (carma::services::Temperature dewPoint)
	This method is meant to check that a given dew point temperature is within reasonable bounds for the CARMA site. More...

static double	safeElevation (double elevation)

static carma::services::Angle	safeElevation (carma::services::Angle elevation)

static double	safeRelativeHumidity (double relHumid)
	This method is meant to check that a given relative humidity is within reasonable bounds for the CARMA site. More...

static carma::services::Velocity	safeWindSpeed (carma::services::Velocity windSpeed)
	This method is meant to check that a given wind speed is within reasonable bounds for the CARMA site. More...

static double	safeWindSpeed (double windSpeed)
	This method is meant to check that a given wind speed is within reasonable bounds for the CARMA site. More...

Static Public Attributes
static const double	DEFAULT_AIR_TEMP = 300.0
	Default air temperature, in Kelvin For when weather station measurement unavailable. More...

static const double	DEFAULT_ATM_PRESSURE = 780.0
	Default atmospheric pressure, in millibars For when weather station measurement unavailable. More...

static const double	DEFAULT_DEW_POINT = 278.388
	Default dew point, in Kelvin For when weather station measurement unavailable. More...

static const double	DEFAULT_RH = 25.0
	Default relative humidity, in percent For when weather station measurement unavailable. More...

static const double	DEFAULT_WIND_SPEED = 0.0
	Default wind speed, in mph. More...

static const double	MAX_AIR_TEMP = 316.5
	Maximum believable air temperature, in Kelvin If weather station gives value above this, there is probably something wrong, so fall back to default. More...

static const double	MAX_ATM_PRESSURE = 1115.0
	Maximum believable atmospheric pressure, in millibars If weather station gives value above this, there is probably something wrong, so fall back to default. More...

static const double	MAX_DEW_POINT
	Maximum believable dew point, in Kelvin If weather station gives value above this, there is probably something wrong, so fall back to default. More...

static const double	MAX_RH = 100.0
	Maximum believable relative humidity, in percent If weather station gives value above this, there is probably something wrong, so fall back to default. More...

static const double	MAX_WIND_SPEED = 200.0
	Maximum reasonable wind speed, in mph If weather station gives value above this, there is probably something wrong, so fall back to default. More...

static const double	MIN_AIR_TEMP = 242.0
	Minimum believable air temperature, in Kelvin If weather station gives value below this, there is probably something wrong, so fall back to default. More...

static const double	MIN_ATM_PRESSURE = 680
	Minimum believable atmospheric pressure, in millibars. More...

static const double	MIN_DEW_POINT = 221.9
	Minimum believable dew point, in Kelvin If weather station gives value below this, there is probably something wrong, so fall back to default. More...

static const double	MIN_ELEVATION = 0.0174533
	The minimum elevation at which pathlength will be directly calculated, in radians. More...

static const double	MIN_RH = 5.0
	Minimum believable relative humidity, in percent If weather station gives value below this, there is probably something wrong, so fall back to default. More...

static const double	MIN_WIND_SPEED = 0.0
	Minimum wind speed, in mph If weather station gives value below this, there is probably something wrong, so fall back to default. More...

static const double	STANDARD_ATM_PRESSURE = 1013.25
	US standard 1 atm of pressure. More...

Detailed Description

This class is used to calculate a variety of quantities related to the earth's atmosphere, such as refractivity, saturated pressure, and pathlength (refractivity integrated through the atmosphere).

Many of these depend upon the weather conditions such as air temperature, pressure, humidity. The class also contains reasonable default, minimum, and maximum values for these weather parameters. The current user of this class is the Delay Engine, however it is expected that Auxiliary Services will use this class to calculate antenna refraction pointing corrections. The Weather Station might also use this class.

Todo:

Verify the min, max, default values for atmospheric quantities are sensible.
Possibly modify computeHorizonPathlength() to take into account all 3 scale heights.

Definition at line 46 of file Atmosphere.h.

Constructor & Destructor Documentation

carma::services::Atmosphere::Atmosphere ( )

no-arg constructor

virtual carma::services::Atmosphere::~Atmosphere ( )

virtual

destructor

Member Function Documentation

double carma::services::Atmosphere::computeDewPoint	(	double	airTemp,
		double	relHumid,
		dewPointMethodType	method = `CLAUSIUS_CLAPEYRON`
	)		const

The dewpoint temperature defines the temperature to which a parcel of air would need to be cooled at constant pressure and constant moisture content in order for the vapor pressure and saturation vapor pressure of the parcel to be equal.

In other words, it's the temperature at which a parcel of air would be saturated (i.e., 100% relative humidity)

The dewpoint temperature is computed from relative humidity and air temperature. There are a few alternate methods available.

Modified Clausius-Clapeyron equation
Magnus-Tetens formula
Latent Heat of Vaporization

See Also: Further discussion of the C-C equation; <a href=http://www.paroscientific.com/dewpoint.htm Further discussion of the Magnus-Tetens formula

Parameters

airTemp	the ambient air temperature in Kelvin
relHumid	the relative humidity, in percent (0..100)
method	compute method

Returns: the dewpoint temperature, in Kelvin

double carma::services::Atmosphere::computeHorizonPathlength	(	double	airTemp,
		double	atmPressure,
		double	relHumid,
		double	frequency
	)		const

Calculate the maximum possible pathlength, toward the horizon.

This is defined in terms of the zenith refractivity and Earth constants in TMS equation 13.40. Its value depends on weather conditions. This method will NOT check that the air temperature, atmospheric pressure, and RH are "safe"; use safeAirTemperature(), safeAtmPressure(), and safeRelativeHumidity() to do that.

Parameters

atmPressure	The atmospheric pressure in millibars
airTemp	The ambient air temperature in Kelvin
relHumid	The relative humidity in percent
frequency	The observing frequency, Hz

Returns: The horizon pathlength, in meters

See Also: computeZenithRefractivity(double airTemp, double atmPressure, double relHumid)

double carma::services::Atmosphere::computeHumidity	(	double	airTemp,
		double	dewTemp,
		dewPointMethodType	method = `CLAUSIUS_CLAPEYRON`
	)		const

The relative humidity is computed from the ambient and dew point temperatures.

There are a few alternate methods available.

Parameters

airTemp	the ambient air temperature in Kelvin
dewTemp	dew point temperature, in Kelvin
method	compute method (see above)

Returns: relHumid the relative humidity, in percent (0..100)

See Also: computeDewPoint(double airTemp, double relHumid, dewPointmethodType method) for explanation of compute method

double carma::services::Atmosphere::computePathlength	(	double	airTemp,
		double	atmPressure,
		double	relHumid,
		double	elevation,
		double	frequency,
		double	altitude = `0.0`
	)		const

This method calculates the refractivity integrated through the atmosphere, that is, the pathlength. See equation 18 of the interferometry design document. This expression for pathlength diverges as elevation approaches zero degrees. Therefore, if the source elevation is below some minimum, the maximum (horizon) pathlength as defined by TMS equation 13.40 is returned.

The pathlength depends on weather conditions. This method will NOT check that the air temperature, atmospheric pressure, and RH are "safe"; use safeAirTemperature(), safeAtmPressure(), and safeRelativeHumidity() to do that.

Note the refraction correction to the elevation is not applied internally by this method. If you want the pathlength for the refraction-corrected elevation, you must first add the the elevation the return value computeRefractionCorrection().

Parameters

atmPressure	The atmospheric pressure in millibars
airTemp	The ambient air temperature in Kelvin
relHumid	The relative humidity in percent
elevation	The source elevation in radians
frequency	The observing frequency, Hz
the	altitude (station height) of the antenna above the array reference plane, meters.

Returns: the pathlength, in meters

See Also: computeZenithRefractivity(double airTemp, double atmPressure, double relHumid); computeHorizonPathlength(); computeRefractionCorrection(); safeAirTemperature(double airTemp); safeAtmPressure(double airTemp); safeRelativeHumidity(double relHumid)

double carma::services::Atmosphere::computeRefractionCorrection	(	double	airTemp,
		double	atmPressure,
		double	relHumid,
		double	elevation,
		double	frequency,
		double	altitude
	)		const

Compute the refraction pointing correction, given the in vacuo elevation and weather parameters.

The return value should be added to the in vacuo elevation. The frequency parameter indicates whether the optical or radio correction is returned. If frequency is greater than 3 THz, the optical correction is returned, otherwise the radio correction is returned. The refraction correction is done using the mapping function of Yan (1996) as written by Mangum ALMA Memo 366.

Parameters

airTemp	The ambient air temperature in Kelvin
atmPressure	The atmospheric pressure in millibars
relHumid	The relative humidity in percent
elevation	The in vacuo (uncorrected) elevation in radians
frequency	The observing frequency, Hz
the	altitude (station height) of the antenna above

Returns: the refraction pointing correction in radians to add to the uncorrected elevation.

double carma::services::Atmosphere::computeSaturatedPressure ( double airTemp ) const

The surface saturated water vapor pressure is used in the calculation of the refractivity.

This method will NOT check that the air temperature is "safe", use safeAirTemperature() to do that.

Parameters

airTemp The ambient air temperature in Kelvin

Returns: the surface saturated water vapor pressure in millibars (equation 13 in interferometry design document)

See Also: safeAirTemperature(double airTemp)

double carma::services::Atmosphere::computeZenithRefractivity	(	double	airTemp,
		double	atmPressure,
		double	relHumid,
		double	frequency
	)		const

The refractivity, N_O, at zenith.

See equation 14 of the interferometry design document. Its value depends on weather conditions. This method will NOT check that the air temperature, atmospheric pressure, and RH are "safe"; use safeAirTemperature(), safeAtmPressure(), and safeRelativeHumidity() to do that.

Parameters

airTemp	The ambient air temperature in Kelvin
atmPressure	The atmospheric pressure in millibars
relHumid	The relative humidity in percent
frequency	The observing frequency, Hz

Returns: zenith refractivity.

See Also: safeAirTemperature(double airTemp); safeAtmPressure(double airTemp); safeRelativeHumidity(double relHumid)

bool carma::services::Atmosphere::isConsistentDewPoint	(	services::Temperature	dewPoint,
		services::Temperature	airTemp,
		double	relHumid,
		dewPointMethodType	method = `CLAUSIUS_CLAPEYRON`,
		double	consistencyPercent = `10.0`
	)

Check that a given dewPoint value is consistent with its paired ambient air temperature and relative humidity.

Parameters

dewPoint	The dew point temperature to check
airTemp	The ambient air temperature to use in the calculation
relHumid	The relative humidity in percent
method	compute method
consistencyPercent	The sloppiness of the consistency check.

Returns: true if the dewPoint entered is consistent with the air temp and relative humidity. Consistency means input dewPoint is within +/-consistencyPercent (inclusive range) of that returned by computeDewPoint(airTemp,relHumid)

See Also: computeDewPoint(double airTemp, double relHumid, dewPointmethodType method) for explanation of compute method

static bool carma::services::Atmosphere::isSafeAirTemperature ( double airTemp )

static

Returns: True if the air temperaure is within reasonable bounds.

Parameters

airTemp The ambient air temperature to check, in Kelvin

See Also: safeAirTemperature(double airTemp)

static bool carma::services::Atmosphere::isSafeAirTemperature ( carma::services::Temperature airTemp )

static

Returns: True if the air temperaure is within reasonable bounds.

Parameters

airTemp The ambient air temperature to check

See Also: safeAirTemperature(services::Temperature airTemp)

static bool carma::services::Atmosphere::isSafeAtmPressure ( double atmPressure )

static

Returns: True if the atmospheric pressure is within reasonable bounds.

Parameters

atmPressure The atmospheric pressure to check, in millibars

See Also: safeAirTemperature(double airTemp)

static bool carma::services::Atmosphere::isSafeAtmPressure ( carma::services::Pressure atmPressure )

static

Returns: True if the atmospheric pressure is within reasonable bounds.

Parameters

atmPressure The atmospheric pressure to check

See Also: safeAtmPressure(double atmPressure)

static bool carma::services::Atmosphere::isSafeDewPoint ( double dewPoint )

static

Returns: true if dewpoint temperature is within reasonable bounds for the CARMA site.

Parameters

dewPoint The dewpoint Temperature

See Also: safeDewPoint(double dewPoint)

static bool carma::services::Atmosphere::isSafeDewPoint ( carma::services::Temperature dewPoint )

static

Returns: true if dewpoint temperature is within reasonable bounds for the CARMA site.

Parameters

dewPoint The dewpoint Temperature

See Also: safeDewPoint(services::Temperature dewPoint)

static bool carma::services::Atmosphere::isSafeElevation ( double elevation )

static

Returns: true if elevation is safe

Parameters

elevation,in radians

See Also: safeElevation(double elevation)

static bool carma::services::Atmosphere::isSafeElevation ( carma::services::Angle elevation )

static

Returns: true if elevation is safe

Parameters

elevation,as Angle

See Also: safeElevation(services::Angle elevation)

static bool carma::services::Atmosphere::isSafeRelativeHumidity ( double relHumid )

static

Returns: true if the relative humidity is within reasonable bounds for the CARMA site.

See Also: safeRelativeHumidity(double relHumid)

carma::services::Temperature carma::services::Atmosphere::lastSafeAirTemperature ( double airTemp )

This method checks if the input air temperature is safe and if so saves and returns the value.

If the input temperature isn't safe, the last safe temperature value is returned. If there is no previous value, DEFAULT_AIR_TEMP is returned. This technique provides alternative air temperature values which more accurately reflect current weather conditions.

Parameters

airTemp Air temperature in Kelvin.

carma::services::Temperature carma::services::Atmosphere::lastSafeAirTemperature ( carma::services::Temperature airTemp )

This method checks if the input air temperature is safe and if so saves and returns the value.

If the input temperature isn't safe, the last safe temperature value is returned. If there is no previous value, DEFAULT_AIR_TEMP is returned. This technique provides alternative air temperature values which more accurately reflect current weather conditions.

Parameters

airTemp Air temperature

carma::services::Temperature carma::services::Atmosphere::lastSafeAirTemperature ( ) const

Returns: the most recently stored safe air temperature

carma::services::Pressure carma::services::Atmosphere::lastSafeAtmPressure ( double atmPressure )

This method checks if the input atmospheric pressure is safe and if so saves and returns the value.

If the input pressure isn't safe, the last safe pressure value is returned. If there is no previous value, DEFAULT_ATM_PRESSURE is returned. This technique provides alternative atmospheric pressure values which more accurately reflect current weather conditions.

Parameters

atmPressure Atmospheric pressure in mbar.

carma::services::Pressure carma::services::Atmosphere::lastSafeAtmPressure ( carma::services::Pressure atmPressure )

This method checks if the input atmospheric pressure is safe and if so saves and returns the value.

If the input pressure isn't safe, the last safe pressure value is returned. If there is no previous value, DEFAULT_ATM_PRESSURE is returned. This technique provides alternative atmospheric pressure values which more accurately reflect current weather conditions.

Parameters

atmPressure Atmospheric pressure

carma::services::Pressure carma::services::Atmosphere::lastSafeAtmPressure ( ) const

Returns: the most recently stored safe atmospheric pressure

carma::services::Temperature carma::services::Atmosphere::lastSafeDewPoint ( double dewPoint )

This method checks if the input dew point is safe and if so saves and returns the value.

If the input dew point isn't safe, the last safe dew point value is returned. If there is no previous value, DEFAULT_DEW_POINT is returned. This technique provides alternative dew point values which more accurately reflect current weather conditions.

Parameters

dewPoint Dew point in Kelvin.

carma::services::Temperature carma::services::Atmosphere::lastSafeDewPoint ( carma::services::Temperature dewPoint )

This method checks if the input dew point is safe and if so saves and returns the value.

If the input dew point isn't safe, the last safe dew point value is returned. If there is no previous value, DEFAULT_DEW_POINT is returned. This technique provides alternative dew point values which more accurately reflect current weather conditions.

Parameters

dewPoint Dew point Temperature

carma::services::Temperature carma::services::Atmosphere::lastSafeDewPoint ( ) const

Returns: the most recently stored safe dew point.

double carma::services::Atmosphere::lastSafeRelativeHumidity ( double relHumid )

This method checks if the input relative humidity is safe and if so saves and returns the value.

If the input humidity isn't safe, the last safe humidity value is returned. If there is no previous value, DEFAULT_RH is returned. This technique provides alternative humidity values which more accurately reflect current weather conditions.

Parameters

relHumid Relative humidity in percent.

double carma::services::Atmosphere::lastSafeRelativeHumidity ( ) const

Returns: the most recently stored safe relative humidity

static double carma::services::Atmosphere::safeAirTemperature ( double airTemp )

static

This method is meant to check that a given air temperature is within reasonable bounds for the CARMA site.

It will return a sensible default air temperature if the input temperature is outside those bounds. Both methods store the last safe air temperature if it is safe.

Parameters

airTemp The ambient air temperature to check, in Kelvin

Returns: airTemp if (MIN_AIR_TEMP <= airTemp <= MAX_AIR_TEMP), otherwise return DEFAULT_AIR_TEMP

static carma::services::Temperature carma::services::Atmosphere::safeAirTemperature ( carma::services::Temperature airTemp )

static

This method is meant to check that a given air temperature is within reasonable bounds for the CARMA site.

It will return a sensible default air temperature inside a Tempurature object if the input temperature is outside those bounds.

Parameters

airTemp The ambient air temperature to check (any units)

Returns: airTemp if its value is within the reasonable bounds otherwise return DEFAULT_AIR_TEMP in a Temperature object.

See Also: safeAirTemperature(double airTemp)

static double carma::services::Atmosphere::safeAtmPressure ( double atmPressure )

static

This method is meant to check that a given atmospheric pressure is within reasonable bounds for the CARMA site.

It will return a sensible default atmospheric pressure if the input pressure is outside those bounds.

Parameters

atmPressure The atmospheric pressure to check, in millibars

Returns: atmPressure if (MIN_ATM_PRESSURE <= atmPressure <= MAX_ATM_PRESSURE), otherwise return DEFAULT_ATM_PRESSURE

static carma::services::Pressure carma::services::Atmosphere::safeAtmPressure ( carma::services::Pressure atmPressure )

static

This method is meant to check that a given atmospheric pressure is within reasonable bounds for the CARMA site.

It will return a sensible default atmospheric pressure inside a Pressure object if the input pressure is outside those bounds.

Parameters

atmPressure The atmospheric pressure to check, in a Pressure object.

Returns: atmPressure if its value is within the reasonable bounds otherwise return DEFAULT_ATM_PRESSURE in a Pressure object.

See Also: safeAtmPressure(double atmPressure)

static double carma::services::Atmosphere::safeDewPoint ( double dewPoint )

static

This method is meant to check that a given dew point temperature is within reasonable bounds for the CARMA site.

It will return a sensible default dew point if the input dew point is outside those bounds.

Parameters

dewPoint The dew point temperature to check, in Kelvin

Returns: dewPoint if (MIN_DEW_POINT <= dewPoint <= MAX_DEW_POINT), otherwise return DEFAULT_DEW_POINT

(NB: Actually MAX_DEW could be a variable set equal to Tambient, since Dewpoint rarely exceeds Tambient)

static carma::services::Temperature carma::services::Atmosphere::safeDewPoint ( carma::services::Temperature dewPoint )

static

This method is meant to check that a given dew point temperature is within reasonable bounds for the CARMA site.

It will return a sensible dew point temperature inside a Tempurature object if the input temperature is outside those bounds.

Parameters

dewPoint The dew point temperature to check, in a Temperature object

Returns: dewPoint if its value is within the reasonable bounds otherwise return DEFAULT_DEW_POINT in a Temperature object.

static double carma::services::Atmosphere::safeElevation ( double elevation )

static

Parameters

elevation The elevation to check, in radians

Returns: elevation if (elevation >= MIN_ELEVATION ) otherwise return MIN_ELEVATION

static carma::services::Angle carma::services::Atmosphere::safeElevation ( carma::services::Angle elevation )

static

Parameters

elevation The elevation ANgle to check, in radians

Returns: An Angle representiing the elevation if (elevation >= MIN_ELEVATION ) otherwise return an Angle representing MIN_ELEVATION

static double carma::services::Atmosphere::safeRelativeHumidity ( double relHumid )

static

This method is meant to check that a given relative humidity is within reasonable bounds for the CARMA site.

It will return a sensible default relative humidity if the input relative humidity is outside those bounds.

Parameters

relHumid The relative humidity to check, in percent.

Returns: relHumid if (MIN_RH <= relHumid <= MAX_RH), otherwise return DEFAULT_RH

static carma::services::Velocity carma::services::Atmosphere::safeWindSpeed ( carma::services::Velocity windSpeed )

static

This method is meant to check that a given wind speed is within reasonable bounds for the CARMA site.

It will return a sensible default wind speed if the input speed is outside those bounds.

Parameters

windSpeed The wind speed to check, represented by a Velocity

Returns: windSpeed if (MIN_WIND_SPEED <= windSpeed.mph() <= MAX_WIND_SPEED), otherwise return DEFAULT_WIND_SPEED in a Velocity object

static double carma::services::Atmosphere::safeWindSpeed ( double windSpeed )

static

This method is meant to check that a given wind speed is within reasonable bounds for the CARMA site.

It will return a sensible default wind speed if the input speed is outside those bounds.

Parameters

windSpeed The wind speed to check, in mph

Returns: windSpeed if (MIN_WIND_SPEED <= windSpeed <= MAX_WIND_SPEED), otherwise return DEFAULT_WIND_SPEED

double carma::services::Atmosphere::ulichRefractionCorrection	(	double	airTemp,
		double	atmPressure,
		double	relHumid,
		double	elevation,
		double	frequency
	)		const

This is to test against the Ulich (1981) radio refraction formulation NOTE: RADIO ONLY.

Parameters

atmPressure	The atmospheric pressure in millibars
airTemp	The ambient air temperature in Kelvin
relHumid	The relative humidity in percent
frequency	The observing frequency, Hz
elevation	The in vacuo (uncorrected) elevation in radians

double carma::services::Atmosphere::waterColumn	(	double	airTemp,
		double	relHumid
	)		const

The water column is derived from the water vapor density and an assumed scaleheight for the wet atmosphere (assumed to be about 2.1km)

Parameters

airTemp	the ambient air temperature in Kelvin
relHumid	the relative humidity, in percent (0..100)

Returns: water column in mm

double carma::services::Atmosphere::waterPartialPressure	(	double	airTemp,
		double	relHumid
	)		const

Compute the partial pressure of water given the ambient air temperature and relative humidity.

The partial pressure is the saturated pressure times the relative humidity.

Parameters

airTemp	the ambient air temperature in Kelvin
relHumid	the relative humidity, in percent (0..100)

Returns: partial pressure of water in millibars

See Also: #computeSaturatedPressure(double airTemp, double relHumid)

double carma::services::Atmosphere::waterVaporDensity	(	double	airTemp,
		double	relHumid
	)		const

The water vapor density is derived from the relative humidity and saturated pressure, and is the amount of water in the atmosphere.

We choose the return units to be g/m^3 rather than g/cm^3 because typical values in g/m^3 will be of order unity.

Parameters

airTemp	the ambient air temperature in Kelvin
relHumid	the relative humidity, in percent (0..100)

Returns: water vapor density in g/m^3

Member Data Documentation

const double carma::services::Atmosphere::DEFAULT_AIR_TEMP = 300.0

static

Default air temperature, in Kelvin For when weather station measurement unavailable.

Definition at line 85 of file Atmosphere.h.

const double carma::services::Atmosphere::DEFAULT_ATM_PRESSURE = 780.0

static

Default atmospheric pressure, in millibars For when weather station measurement unavailable.

The default is based on measurements at Cedar Flat.V

Definition at line 59 of file Atmosphere.h.

const double carma::services::Atmosphere::DEFAULT_DEW_POINT = 278.388

static

Default dew point, in Kelvin For when weather station measurement unavailable.

Definition at line 135 of file Atmosphere.h.

const double carma::services::Atmosphere::DEFAULT_RH = 25.0

static

Default relative humidity, in percent For when weather station measurement unavailable.

Definition at line 108 of file Atmosphere.h.

const double carma::services::Atmosphere::DEFAULT_WIND_SPEED = 0.0

static

Default wind speed, in mph.

Definition at line 169 of file Atmosphere.h.

const double carma::services::Atmosphere::MAX_AIR_TEMP = 316.5

static

Maximum believable air temperature, in Kelvin If weather station gives value above this, there is probably something wrong, so fall back to default.

Definition at line 101 of file Atmosphere.h.

const double carma::services::Atmosphere::MAX_ATM_PRESSURE = 1115.0

static

Maximum believable atmospheric pressure, in millibars If weather station gives value above this, there is probably something wrong, so fall back to default.

Definition at line 78 of file Atmosphere.h.

const double carma::services::Atmosphere::MAX_DEW_POINT

static

Maximum believable dew point, in Kelvin If weather station gives value above this, there is probably something wrong, so fall back to default.

Ideally, this should be non-const and set to the current Ambient temperature, since Tdp is "never" greater than Tambient. Maybe I need a private maxdewpoint() method.

Definition at line 156 of file Atmosphere.h.

const double carma::services::Atmosphere::MAX_RH = 100.0

static

Maximum believable relative humidity, in percent If weather station gives value above this, there is probably something wrong, so fall back to default.

Definition at line 123 of file Atmosphere.h.

const double carma::services::Atmosphere::MAX_WIND_SPEED = 200.0

static

Maximum reasonable wind speed, in mph If weather station gives value above this, there is probably something wrong, so fall back to default.

Definition at line 183 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_AIR_TEMP = 242.0

static

Minimum believable air temperature, in Kelvin If weather station gives value below this, there is probably something wrong, so fall back to default.

Definition at line 93 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_ATM_PRESSURE = 680

static

Minimum believable atmospheric pressure, in millibars.

If weather station gives value below this, there is probably something wrong, so fall back to default.

Definition at line 71 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_DEW_POINT = 221.9

static

Minimum believable dew point, in Kelvin If weather station gives value below this, there is probably something wrong, so fall back to default.

Definition at line 143 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_ELEVATION = 0.0174533

static

The minimum elevation at which pathlength will be directly calculated, in radians.

Below this elevation, computeHorizonPathLength() is used. Currently set to 1 degree.

Definition at line 164 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_RH = 5.0

static

Minimum believable relative humidity, in percent If weather station gives value below this, there is probably something wrong, so fall back to default.

Definition at line 116 of file Atmosphere.h.

const double carma::services::Atmosphere::MIN_WIND_SPEED = 0.0

static

Minimum wind speed, in mph If weather station gives value below this, there is probably something wrong, so fall back to default.

Definition at line 176 of file Atmosphere.h.

const double carma::services::Atmosphere::STANDARD_ATM_PRESSURE = 1013.25

static

US standard 1 atm of pressure.

Definition at line 64 of file Atmosphere.h.

The documentation for this class was generated from the following file:

carma/services/Atmosphere.h

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