NSA/MET/C1 - 20m T/RH sensor failure

The 20 meter temperature, dew point, and humidity data were spiking and reporting high/low 
in relation to other sensors on the tower.  Sensor was replaced.

Use data from other 3 tower levels.

• temp_std
• rh_mean
• temp_mean
• dew_point_std
• vapor_pressure_mean
• vapor_pressure_std
• dew_point_mean
• rh_std