137.229.92.251 at 20:57, 28 November 2011

2011-11-28T20:57:08Z

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Use this shorty program to compute relative humidity from dry bulb air temperature and dew point. Potential workflow and reason for usage would be something like this:
Have hourly air temperature & relative humidity data... would like to compute mean daily or mean monthly values for RH but you can't apply a simple average to RH. So...
1) Use the dew point calculator program to compute dew point from hourly time series of AT & RH
2) Use the calculate mean daily or mean monthly subroutine to find mean air temperature and dew point
3) Use this subroutine to calculate RH from air temperature and dew point.
<pre>

Sub RH_Calcs()

'' This subroutine runs through a worksheet and calculates relative humidity from dew point and air temperature
'' as per the Dingman book appendix.

Dim inputrow As Long
Dim outputrow As Long
Dim inputdatecol As Integer
Dim inputtempcol As Integer
Dim inputdpcol As Integer
Dim outputrhcol As Integer
Dim inputWS As Integer
Dim outputWS As Integer
Dim es As Double
Dim temperature As Double
Dim Wa As Double
Dim e As Double
Dim dewpoint As Double

inputdatecol = 1
inputWS = 1
inputrow = 15
outputWS = inputWS
outputrow = inputrow

inputdpcol = 14
inputtempcol = 15
outputrhcol = 16

Do While Worksheets(inputWS).Cells(inputrow, inputdatecol).Value <> ""
'' #1 Read in the values
If Abs(Worksheets(inputWS).Cells(inputrow, inputtempcol).Value) <> 6999 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputtempcol).Value) <> 7777 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputtempcol).Value) <> 9999 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputtempcol).Value) <> 9999.9 And _
Worksheets(inputWS).Cells(inputrow, inputtempcol).Value <> "" Then
temperature = Worksheets(inputWS).Cells(inputrow, inputtempcol).Value
Else:
temperature = 6999
End If
If Abs(Worksheets(inputWS).Cells(inputrow, inputdpcol).Value) <> 6999 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputdpcol).Value) <> 7777 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputdpcol).Value) <> 9999 And _
Abs(Worksheets(inputWS).Cells(inputrow, inputdpcol).Value) <> 9999.9 And _
Worksheets(inputWS).Cells(inputrow, inputdpcol).Value <> "" Then
dewpoint = Worksheets(inputWS).Cells(inputrow, inputdpcol).Value
Else:
dewpoint = 6999
End If
If temperature <> 6999 And dewpoint <> 6999 Then
es = 0.611 * Exp((17.3 * temperature) / (temperature + 237.3))
e = 0.611 * Exp((17.3 * dewpoint) / (dewpoint + 237.3))
Wa = e / es * 100
Else:
Wa = 6999
End If
If Wa <> 6999 Then
Worksheets(outputWS).Cells(outputrow, outputrhcol).Value = Wa
End If
outputrow = outputrow + 1
inputrow = inputrow + 1
Loop
Range("A12").Select
End Sub

</pre>

Relative Humidity Calculator Routine - Revision history

137.229.92.251 at 20:57, 28 November 2011