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#wetbulb.cgi by Tim Brice NWS El Paso
#calculate absolute temp for air temperature

if ($wetbulb{airtemp} =~ /-?(\d+)\.?(\d+)|-?(\d+)/) {
  if ($wetbulb{corf2} eq Fahrenheit) {

$celsius2 = 5/9*($wetbulb{airtemp} - 32);
   $abairtemp = $celsius2 + 273.15;

} else {

$abairtemp = $wetbulb{airtemp} + 273.15;

}

}  else {
  print "An illegal character was entered.\n";
  die
}

#calculate absolute temp for wet-bulb temperature

if ($wetbulb{wettemp} =~ /-?(\d+)\.?(\d+)|-?(\d+)/)  {
  if ($wetbulb{corf1} eq Fahrenheit)  {

$celsius1 = 5/9*($wetbulb{wettemp} - 32);
     $abwettemp = $celsius1 + 273.15;

}  else  {

$abwettemp = $wetbulb{wettemp} + 273.15;

}
} else  {

print "An illegal character was entered\n";
die
}

#prepare pressure entry

if ($wetbulb{press} =~ /(\d+)\.?(\d+)/)  {
  if ($wetbulb{mborin} eq millibars)  {

$press = $wetbulb{press};

} else {

$press = $wetbulb{press} * 33.8639;

}
} else {

print "An illegal character was entered\n";
   die
 }

#start the math

$Xwd = 21.40 - 5351/$abairtemp;
$Xww = 21.40 - 5351/$abwettemp;

$ewd = exp($Xwd);
$eww = exp($Xww);

#calculate the vapor pressure and saturation vapor pressure

$e = $eww - $press*($abairtemp - $abwettemp)/1555;
$es = $ewd;

#calculate the dewpoint and relative humidity

$dewpoint = 5351/(21.40 - log ($e)) - 273.15;

$rh = 100*($e/$es);

#Let's make some pretty output

$~ = WB7;
write;

format WB7 =
With an air temperature of @###.# degrees @<<<<<<<<<< a wet-bulb temperature
 $wetbulb{airtemp} $wetbulb{corf2}
of @###.# degrees @<<<<<<<<<< and a station pressure of @###.##
 $wetbulb{wettemp} $wetbulb{corf1} $wetbulb{press}
@<<<<<<<<<<<<<<<<:
$wetbulb{mborin}
.

$~ = WETBULB1;
write;
format WETBULB1 =

You have a relative humidity of @##.# percent and a dewpoint of
 $rh
.
if ($wetbulb{corf2} eq Fahrenheit) {
 $dewpoint1 = (9/5*$dewpoint) + 32;
 $~ = WETBULB2;
 write;
format WETBULB2 =

@###.# degrees Fahrenheit.
 $dewpoint1
.
} else {
 $~ = WETBULB3;
 write;
format WETBULB3 =

@###.# degrees Celsius.
 $dewpoint
.
}

if ($wetbulb{wettemp} > $wetbulb{airtemp}) {
 print "The wet-bulb temperature is greater than the air temperature,
 this only rarely occurs in the atmosphere. You may want to
 go back and double check your entries.";
}

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