SGP/SMOS/E4 - Sensor failure

RH values drop to zero during most of the period between 01/17 and 01/19.  Sensor was 
replaced.

Use nearest neighbor sites to estimate RH%.

• Time of minimum vapor pressure(time_min_vap_pres)
• Maximum Vapor Pressure(max_vap_pres)
• Minimum Relative Humidity(min_rh)
• Time of maximum vapor pressure(time_max_vap_pres)
• Daily maximum relative humidity(max_rh)
• Daily minimum vapor pressure(min_vap_pres)
• Time of maximum relative humidity(time_max_rh)
• Time of Relative Humidity(time_min_rh)

• Standard Deviation of Relative Humidity(sd_rh)
• Relative Humidity (hybrid-b grid)(rh)
• Vapor Pressure (kiloPascals)(vap_pres)
• Standard deviation of vapor pressure(sd_vap_pres)

• Relative Humidity (hybrid-b grid)(rh)
• Vapor Pressure (kiloPascals)(vap_pres)