How Do I calculate the Dew Point from the Temperature and Relative Humidity. The equation I need to use is: Td = T - ((100 - RH)/5.)

%% Import data from text file
% Script for importing data from the following text file:
%
%    filename: C:\Users\smctu\OneDrive\Documents\School\Remote Sensing\sonde_data.txt
%
% Auto-generated by MATLAB on 18-Mar-2021 01:23:08

%% Setup the Import Options and import the data
opts = delimitedTextImportOptions("NumVariables", 7);

% Specify range and delimiter
opts.DataLines = [4, Inf];
opts.Delimiter = " ";

% Specify column names and types
opts.VariableNames = ["FltTime", "Press", "Temp", "RelHum", "WSpeed", "WDirn", "GPM_AGL"];
opts.VariableTypes = ["double", "double", "double", "double", "double", "double", "double"];

% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";
opts.ConsecutiveDelimitersRule = "join";
opts.LeadingDelimitersRule = "ignore";

% Import the data
sondedata = readtable("C:\Users\smctu\OneDrive\Documents\School\Remote Sensing\sonde_data.txt", opts);

figure
subplot(2,1,1)
X=sondedata.Temp+273.15
Y=sondedata.GPM_AGL
Z=sondedata.RelHum
plot(X,Y,'r')
hold on;
plot(X,Z,'b-')
xlabel("Temperature(K)")
ylabel("Altitude(km)")
ylim([0,25000])
yticks(0:5000:30000)

clear opts

[John]

Hi, just a question. when running this program I get this error. Any suggestions pls.

Error using matlab.io.ImportOptions/readtable (line 499)

Unable to find or open 'C:\Users\smctu\OneDrive\Documents\School\Remote Sensing\sonde_data.txt'. Check the path and filename or file permissions.

[Walter Roberson]

@John

Do you in fact have a file named C:\Users\smctu\OneDrive\Documents\School\Remote Sensing\sonde_data.txt ?

The code asks to read that file specifically in the line

sondedata = readtable("C:\Users\smctu\OneDrive\Documents\School\Remote Sensing\sonde_data.txt", opts);

[John]

ok got it..... I just need to point this to my data file.

will this calculator work for temperatures down in the -100 C

thanks,

[Walter Roberson]

@John

The code does not do any meaningful caclulation. The most it does is convert celcius input to Kelvin value. The formula for that conversion is still valid at -100 C.

Answer 1

[KSSV]

If X, Z are your Temperature and Relative Humidity arrays, use:

Td = X-((100 - Z)/5.) ;