function AT(airtemp)
  {
  var A = 8.1332;
  var B = 1762.39;
  var C = 235.66;
  var u1 = airtemp.corf[0].checked;
  var u2 = airtemp.corf[1].checked;
  var u3 = airtemp.corf[2].checked;
  var rh = parseInt(airtemp.relativeh.value);
  if (u1 == true)
    {
    var td = parseInt((airtemp.dewpoint.value-32)/1.8);
    }
  else
    {
    if (u3 == true)
      {
      var td = parseInt(airtemp.dewpoint.value-273.14);
      }
    else
      {
      var td = parseInt(airtemp.dewpoint.value);
      }
    }
  var pd1 = A - B/(td + 235.66);
  var pd = Math.pow(10, pd1);
  var ta2 = pd*100/rh;
  var ta1 = Math.log(ta2);
  var ta0 = ta1 / Math.LN10;
  var ta = (-B/(ta0 - A)) - C;
  if (u1 == true)
    {
    res = ta *1.8+32;
    }
  else
    {
    if (u3 == true)
      {
      res = ta + 273.14;
      }
    else
      {
      res = ta;
      }
    }
  airtemp.atres.value = (Math.round(res*10))/10;
  }

function clearat(form)
  {
  form.relativeh.value = "";
  form.dewpoint.value = "";
  form.atres.value = "";
  }