Relative Humidity from Dew Point/Air temperature

[ohall7]

Hi friends,

 

I have a problem from my Geography course that my notes do not tell me how to solve so hopefully you guys will be able to help me out!

 

Anyway, the problem is "The dew point temperature is 55°F and the air temperature is 75°F. Q1: What is the relative humidity? Q2: What is the relative humidity if the temperature were to drop to 50°F overnight?"

 

Not looking for answers, but would like assistance in learning how to solve this problem.

 

Thanks!

[swansont]

http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-86-2-225

[John Cuthber]

You can see why people use tables

http://www.engineeringtoolbox.com/humidity-measurement-d_561.html