Merge pull request #952 from AlbertoCuadra/develop

Add: include routine to compute specific humidity of air

utils/thermo/humidity_specific.m

@@ -0,0 +1,26 @@
+function value = humidity_specific(T, p, humidity_relative)
+    % Get the specific humidity of air [kg_w/kg_da] at a given temperature and pressure
+    %
+    % Args:
+    %     T (float): Temperature [K]
+    %     p (float): Pressure [bar]
+    %     humidity_relative (float): Relative humidity [%]
+    %
+    % Returns:
+    %     value (float): Specific humidity of air [kg_w/kg_da] at a given temperature and pressure
+
+    % Constants
+    A = [-5.8002206e3, 1.3914993e0, -4.8640239e-2, 4.1764768e-5, -1.4452093e-8, 6.5459673e0];
+
+    % Change pressure from [bar] to [Pa]
+    p = p * 1e5;
+
+    % Saturated vapor pressure [Pa]
+    p_ws = exp( A(1)./T + A(2) + A(3) * T + A(4) * T.^2 + A(5) * T.^3 + A(6) * log(T) ); % Temperature in [K]
+
+    % Vapor pressure [Pa]
+    p_w = humidity_relative * p_ws * 1e-2;
+
+    % Specific humidity [kg_w/kg_da]
+    value = 0.622 * p_w ./ (p - p_w);
+end