Subject: Re: Index of Refraction of Atmosphere

From: Michael Dworetsky <[email-masked]>
Date: 2 Mar 1998 08:18:44 -0600

Rodney Blackall wrote:
> 
> In article <[email-masked]>,
>  Michael Dworetsky <[email-masked]> wrote:
> > Stephenson Tucker wrote:
> > >
> > > I am looking for the index of refraction of the atmosphere based >>on temperature, pressure, relative humidity and wavelength.
> 
> > If you can find it, this is very useful:
> 
> > Tablitsi Refraktsii Pulkovskoii Observatorii 5th Edn (1985).  With a
> > nice preface in English.
> 
> > Boris Garfinkel, Astronomical Refraction in a Polytropic Atmosphere,
> > probably would give you what you want if you don't need extreme
> > accuracy.   Plenty on horizontal refraction.  Astronomical Journal, >72, p 235, 1967.
> 
> This information is critically important to the armed forces who need
> to know this for predicting the behaviour of radar beams. As a first
> step you could try asking the Defence Services division of the UK
> Meteorological Office. I know they have access to great expertise in
> this field but of course do not know how much they can reveal.
> 
> --

 Ron Stone published a recent article (PASP 108, 1051, 1996).  He
gives analytical formulas that (he claims) are good to a few mas even at
75 degrees zenith distance.  Thanks to Bill Owen for pointing this one
out.

This is for optical wavelengths.  The atmospheric propagation is not
similar at centimetric wavelengths typical of radar.  For the latter,
the military may have declassified some data in more than one country,
or there may be information in ordinary journals.  I haven't looked but
thanks for mentioning this.

> Rodney Blackall (retired meteorologist)
> London, ENGLAND

-- 
Mike Dworetsky, Department of Physics      
& Astronomy, University College London  
Gower Street, London WC1E 6BT  UK       
   email: [email-masked]

---

From: Maren Purves <[email-masked]>
Date: 2 Mar 1998 08:20:22 -0600

Rodney Blackall wrote:

> > > I am looking for the index of refraction of the atmosphere based=20
>>on temperature, pressure, relative humidity and wavelength.=9B1]       =

> > accuracy.   Plenty on horizontal refraction.  Astronomical Journal, >=
72, p 235, 1967.

> this field but of course do not know how much they can reveal.

There was a paper from JPL ... I can't find the reference at
the moment, but here's the code:

      SUBROUTINE SBEND (PRESS, TEMP, HUMID, ZNITH, R)
      DIMENSION A(2), B(2), C(2), E(12), P(2), T(2), Z(2)
      P (1) =3D 760.0
      T (1) =3D 273.0
      Z (1) =3D 91.870
      P(2) =3D PRESS *760./1013.
      T(2) =3D TEMP +273.0
      Z(2) =3D ZNITH
      A(1) =3D 0.40816
      A(2) =3D 112.30
      B(1) =3D 0.12820
      B(2) =3D 142.88
      C(1) =3D 0.80000
      C(2) =3D 99.344
      E(1) =3D 46.625
      E(2) =3D 45.375
      E(3) =3D 4.1572
      E(4) =3D 1.4468
      E(5) =3D 0.25391
      E(6) =3D 2.2716
      E(7) =3D -1.3465
      E(8) =3D -4.3877
      E(9) =3D 3.1484
      E(10) =3D 4.5201
      E(11) =3D -1.8982
      E(12) =3D 0.890000
      W0 =3D 7100.0
      W1 =3D 17.149
      W2 =3D 4684.1
      W3 =3D 38.450
      D3 =3D 1+DELTA (Z,C,Z(2))
      FP =3D (P(2)/P(1)) * (1-DELTA (P, A, Z(2))/D3)
      FT =3D (T(1)/T(2)) * (1-DELTA (T, B, Z(2))/D3)
      FW=3D 1+(W0* 0.01*HUMID* EXP ((W1*T(2)-W2) /(T(2)-W3))/ (T(2)*P(2))=
)
      U =3D (Z(2)-E(1))/E(2)
      X =3D E(11)
      DO 1 I=3D1,8
1     X=3D E(11-I) + U*X
      R=3D FT*FP*FW * (EXP(X/D3)-E(12))
      RETURN

I just found this post ...
I did a comparison between the refraction corrections from
several submm telescopes at some point. Let me know (preferably
by email) if you're interested in the fortran code.

Maren Purves,
now at UKIRT (where refraction doesn't depend on humidity)