Note

Click here to download the full example code

# Dewpoint and Mixing Ratio¶

Use functions from `metpy.calc`

as well as pint’s unit support to perform calculations.

The code below converts the mixing ratio value into a value for vapor pressure assuming both 1000mb and 850mb ambient air pressure values. It also demonstrates converting the resulting dewpoint temperature to degrees Fahrenheit.

```
import metpy.calc as mpcalc
from metpy.units import units
```

Create a test value of mixing ratio in grams per kilogram

```
mixing = 10 * units('g/kg')
print(mixing)
```

Out:

```
10.0 gram / kilogram
```

Now throw that value with units into the function to calculate the corresponding vapor pressure, given a surface pressure of 1000 mb

```
e = mpcalc.vapor_pressure(1000. * units.mbar, mixing)
print(e)
```

Out:

```
15823.283396314564 gram * millibar / kilogram
```

Take the odd units and force them to millibars

```
print(e.to(units.mbar))
```

Out:

```
15.823283396314565 millibar
```

Take the raw vapor pressure and throw into the dewpoint function

```
td = mpcalc.dewpoint(e)
print(td)
```

Out:

```
13.854135353732214 degC
```

Which can of course be converted to Fahrenheit

```
print(td.to('degF'))
```

Out:

```
56.937444036717935 degF
```

Now do the same thing for 850 mb, approximately the pressure of Denver

```
e = mpcalc.vapor_pressure(850. * units.mbar, mixing)
print(e.to(units.mbar))
```

Out:

```
13.449790886867381 millibar
```

And print the corresponding dewpoint

```
td = mpcalc.dewpoint(e)
print(td, td.to('degF'))
```

Out:

```
11.376545231347285 degC 52.47778181642507 degF
```

**Total running time of the script:** ( 0 minutes 0.004 seconds)