Arjen Markus (4 may 2006) It occurred to me that we do not yet have a decent module in Tcllib yet that collects the various physical empirical formulae. So, right now, if I want to compute the water content of air, I have to hunt the Internet for the right formula. Similarly, the density of water as a function of temperature and salinity.
I am probably not the only one with that little problem, so I propose to collect such formulae here (with a reference) so that later we can simply wrap them up in a package/module for Tcllib.
# Auxiliary procedure
proc check {descr var range} {
foreach {min max} $range break
if { $var < $min || $var > $max } {
return -code error "Range error: $descr should be between $min and $max"
}
}A formula for the humidity content of air:
check "dew-point temperature" $td {-20 100}
set vapordens [expr {5.018+0.32321*$td+8.1847e-3*$td*$td+3.1243e-4*$td*$td*$td}]Symbols:
Reference: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html#c3
IDG May 04 2006: All empirical formulae need to have their range of validity stated. Note what happens to the above as td -> infinity :-)
AM Ah! Good thinking! I have added the valid range.
[ Category Physics ]