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function TANETZData.temprh2td(t : extended; rh : extended) : extended;
//    baker, schlatter  17-may-1982     original version.

//   this function returns the dew point (celsius) given the temperature
//   (celsius) and relative humidity (%). the formula is used in the
//   processing of u.s. rawinsonde data and is referenced in parry, h.
//   dean, 1969: "the semiautomatic computation of rawinsondes,"
//   technical memorandum wbtm edl 10, u.s. department of commerce,
//   environmental science services administration, weather bureau,
//   office of systems development, equipment development laboratory,
//   silver spring, md (october), page 9 and page ii-4, line 460.

var
  x : extended;
  dpd : extended;
begin
  x := 1.0 - 0.01 * rh;

//   compute dew point depression.

  dpd := (14.55 + 0.114 * t) * x + power(((2.5 + 0.007 * t) * x), 3) + (15.9 + 0.117 * t) * power(x, 14);
  Result := t - dpd;
end;