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5.1.10 sd.opacity_model - Tool

Single dish specific opacity model
Description

This class implements opacity/atmospheric brightness temperature model equivalent to the model available in MIRIAD. The actual math is a convertion of the Fortran code written by Bob Sault for MIRIAD. It implements a simple model of the atmosphere and Liebe’s model (1985) of the complex refractive index of air.

The model of the atmosphere is one with an exponential fall-off in the water vapour content (scale height of 1540 m) and a temperature lapse rate of 6.5 mK/m. Otherwise the atmosphere obeys the ideal gas equation and hydrostatic equilibrium.

Note that the model includes atmospheric lines up to 800 GHz, but was not rigorously tested above 100 GHz and for instruments located at a significant elevation. For high-elevation sites it may be necessary to adjust scale height and lapse rate.

The constructor takes several arguments that specifies observatory and weather informations.

Arguments





Inputs

temperature

Air temperature at the observatory (K)

allowed:

float

Default:

288.0

pressure

Air pressure at the sea level if the observatory elevation is set to non-zero value (note, by default is set to 700m) or at the observatory ground level if the elevation is set to 0. The value is in Pascals or hPa.

allowed:

float

Default:

101325.0

humidity

Air humidity at the observatory (fractional)

allowed:

float

Default:

0.5

elevation

Observatory elevation about sea level (in meters)

allowed:

float

Default:

700.0





Example

     o=sd.opacity_model(temperature=300.0,elevation=1300.0)  
     tau=sd.get_opacities([1.0e11,1.1e11])  
     print tau  
     [0.2363221976673901, 0.3068089293871521]

Methods

get_opacities Get the opacity value(s) for the given frequency(ies)
set_observatory_elevationUpdate the model using the given observatory elevation
set_weather Update the model using the given environmental parameters

    sd.opacity_model.get_opacities - Function
    sd.opacity_model.set_observatory_elevation - Function
    sd.opacity_model.set_weather - Function


More information about CASA may be found at the CASA web page

Copyright 2016 Associated Universities Inc., Washington, D.C.

This code is available under the terms of the GNU General Public Lincense


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