TWP/SMET/C3 - Lower wind direction sensor failure

The lower wind direction sensor failed on 4/14 and disagrees significantly with the upper 
wind direction sensor.  The lower wind sensor reports a constant value around 0-15 
degrees since it failed.  Testing showed that excitation channel two on the logger was the 
problem.  Logger was replaced by spare.

Use upper wind direction data.

• Lower sensor, wind direction vector average(lo_dir_vec_avg)
• Lower sensor, wind direction standard deviation(lo_dir_sd)