| 1 | //#---------------------------------------------------------------------------
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| 2 | //# STAtmosphere.h: Model of atmospheric opacity
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| 3 | //#---------------------------------------------------------------------------
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| 4 | //# Copyright (C) 2004
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| 5 | //# ATNF
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| 6 | //#
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| 7 | //# The code is based on the Fortran code written by Bob Sault for MIRIAD.
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| 8 | //# Converted to C++ by Max Voronkov. This code uses a simple model of the
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| 9 | //# atmosphere and Liebe's model (1985) of the complex refractive index of
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| 10 | //# air.
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| 11 | //#
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| 12 | //# The model of the atmosphere is one with an exponential fall-off in
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| 13 | //# the water vapour content (scale height of 1540 m) and a temperature lapse
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| 14 | //# rate of 6.5 mK/m. Otherwise the atmosphere obeys the ideal gas equation
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| 15 | //# and hydrostatic equilibrium.
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| 16 | //#
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| 17 | //# This program is free software; you can redistribute it and/or modify it
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| 18 | //# under the terms of the GNU General Public License as published by the Free
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| 19 | //# Software Foundation; either version 2 of the License, or (at your option)
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| 20 | //# any later version.
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| 21 | //#
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| 22 | //# This program is distributed in the hope that it will be useful, but
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| 23 | //# WITHOUT ANY WARRANTY; without even the implied warranty of
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| 24 | //# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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| 25 | //# Public License for more details.
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| 26 | //#
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| 27 | //# You should have received a copy of the GNU General Public License along
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| 28 | //# with this program; if not, write to the Free Software Foundation, Inc.,
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| 29 | //# 675 Massachusetts Ave, Cambridge, MA 02139, USA.
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| 30 | //#
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| 31 | //# Correspondence concerning this software should be addressed as follows:
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| 32 | //# Internet email: Malte.Marquarding@csiro.au
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| 33 | //# Postal address: Malte Marquarding,
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| 34 | //# Australia Telescope National Facility,
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| 35 | //# P.O. Box 76,
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| 36 | //# Epping, NSW, 2121,
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| 37 | //# AUSTRALIA
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| 38 | //#
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| 39 | //# $Id: STAtmosphere.h 1346 2007-04-26 03:24:41Z mar637 $
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| 40 | //#---------------------------------------------------------------------------
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| 41 |
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| 42 | #ifndef STATMOSPHERE_H
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| 43 | #define STATMOSPHERE_H
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| 44 |
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| 45 | #include <vector>
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| 46 |
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| 47 | namespace asap {
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| 48 |
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| 49 | /**
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| 50 | * This class implements opacity/atmospheric brightness temperature model
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| 51 | * equivalent to the model available in MIRIAD. The actual math is a
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| 52 | * convertion of the Fortran code written by Bob Sault for MIRIAD.
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| 53 | * It implements a simple model of the atmosphere and Liebe's model (1985)
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| 54 | * of the complex refractive index of air.
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| 55 | *
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| 56 | * The model of the atmosphere is one with an exponential fall-off in
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| 57 | * the water vapour content (scale height of 1540 m) and a temperature lapse
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| 58 | * rate of 6.5 mK/m. Otherwise the atmosphere obeys the ideal gas equation
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| 59 | * and hydrostatic equilibrium.
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| 60 | *
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| 61 | * Note, the model includes atmospheric lines up to 800 GHz, but was not
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| 62 | * rigorously tested above 100 GHz and for instruments located at
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| 63 | * a significant elevation. For high-elevation sites it may be necessary to
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| 64 | * adjust scale height and lapse rate.
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| 65 | *
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| 66 | * @brief The ASAP atmosphere opacity model
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| 67 | * @author Max Voronkov
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| 68 | * @date $Date: 2010-03-17 14:55:17 +1000 (Thu, 26 Apr 2007) $
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| 69 | * @version
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| 70 | */
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| 71 | class STAtmosphere {
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| 72 | public:
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| 73 | /**
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| 74 | * Default Constructor (apart from optional parameters).
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| 75 | * The class set up this way will assume International Standard Atmosphere (ISA) conditions,
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| 76 | * except for humidity. The latter is assumed to be 50%, which seems more realistic for
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| 77 | * Australian telescopes than 0%.
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| 78 | * @param[in] wvScale water vapour scale height (m), default is 1540m to match MIRIAD's model
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| 79 | * @param[in] maxAlt maximum altitude of the model atmosphere (m), plane parallel layers are spread linearly up to
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| 80 | * this height, default is 10000m to match MIRIAD.
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| 81 | * @param[in] nLayers number of plane parallel layers in the model (essentially for a numberical integration),
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| 82 | * default is 50 to match MIRIAD.
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| 83 | **/
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| 84 | explicit STAtmosphere(double wvScale = 1540., double maxAlt = 10000.0, size_t nLayers = 50);
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| 85 |
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| 86 | /**
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| 87 | * Constructor with explicitly given parameters of the atmosphere
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| 88 | * @param[in] temperature air temperature at the observatory (K)
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| 89 | * @param[in] pressure air pressure at the observatory (Pascals)
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| 90 | * @param[in] humidity air humidity at the observatory (fraction)
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| 91 | * @param[in] lapseRate temperature lapse rate (K/m), default is 0.0065 K/m to match MIRIAD and ISA
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| 92 | * @param[in] wvScale water vapour scale height (m), default is 1540m to match MIRIAD's model
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| 93 | * @param[in] maxAlt maximum altitude of the model atmosphere (m), plane parallel layers are spread linearly up to
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| 94 | * this height, default is 10000m to match MIRIAD.
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| 95 | * @param[in] nLayers number of plane parallel layers in the model (essentially for a numberical integration),
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| 96 | * default is 50 to match MIRIAD.
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| 97 | **/
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| 98 | STAtmosphere(double temperature, double pressure, double humidity, double lapseRate = 0.0065,
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| 99 | double wvScale = 1540., double maxAlt = 10000.0, size_t nLayers = 50);
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| 100 |
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| 101 | /**
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| 102 | * Set the new weather station data, recompute the model
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| 103 | * @param[in] temperature air temperature at the observatory (K)
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| 104 | * @param[in] pressure air pressure at the observatory (Pascals)
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| 105 | * @param[in] humidity air humidity at the observatory (fraction)
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| 106 | **/
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| 107 | void setWeather(double temperature, double pressure, double humidity);
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| 108 |
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| 109 | protected:
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| 110 | /**
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| 111 | * Build the atmosphere model based on exponential fall-off, ideal gas and hydrostatic
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| 112 | * equilibrium. The model parameters are taken from the data members of this class.
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| 113 | **/
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| 114 | void recomputeAtmosphereModel();
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| 115 |
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| 116 | /**
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| 117 | * Obtain the number of model layers, do consistency check that everything is
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| 118 | * resized accordingly
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| 119 | * @retrun number of model layers
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| 120 | **/
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| 121 | size_t nLayers() const;
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| 122 |
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| 123 | /**
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| 124 | * Determine the saturation pressure of water vapour for the given temperature.
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| 125 | *
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| 126 | * Reference:
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| 127 | * Waters, Refraction effects in the neutral atmosphere. Methods of
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| 128 | * Experimental Physics, vol 12B, p 186-200 (1976).
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| 129 | *
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| 130 | * @param[in] temperature temperature in K
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| 131 | * @return vapour saturation pressure (Pascals)
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| 132 | **/
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| 133 | static double wvSaturationPressure(double temperature);
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| 134 |
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| 135 | private:
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| 136 |
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| 137 | // heights of all model layers
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| 138 | std::vector<double> itsHeights;
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| 139 |
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| 140 | // temperatures of all model layers
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| 141 | std::vector<double> itsTemperatures;
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| 142 |
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| 143 | // partial pressures of dry component for all model layers
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| 144 | std::vector<double> itsDryPressures;
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| 145 |
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| 146 | // partial pressure of water vapour for all model layers
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| 147 | std::vector<double> itsVapourPressures;
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| 148 |
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| 149 | /**
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| 150 | * Atmosphere parameters
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| 151 | **/
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| 152 |
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| 153 | // ground level temperature (K)
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| 154 | double itsGndTemperature;
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| 155 |
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| 156 | // ground level pressure (Pascals)
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| 157 | double itsGndPressure;
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| 158 |
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| 159 | // ground level humidity (fraction)
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| 160 | double itsGndHumidity;
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| 161 |
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| 162 | // lapse rate (K/m)
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| 163 | double itsLapseRate;
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| 164 |
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| 165 | // water vapour scale height (m)
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| 166 | double itsWVScale;
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| 167 |
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| 168 | // altitude of the highest layer of the model (m)
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| 169 | double itsMaxAlt;
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| 170 | };
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| 171 |
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| 172 | } // namespace asap
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| 173 |
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| 174 | #endif // #ifndef STATMOSPHERE_H
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| 175 |
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