GRW/VCEIL/M1 - Receiver failure

The AMF VCEIL had lower-than-normal laser transmitter power, ~84%, so the instrument was 
replaced with a spare on 4/22. The spare VCEIL had just been repaired but began to display 
receiver failure warnings.

Diagnostic information was sent to Vaisala and we discussed either replacing the receiver 
with the one from the original VCEIL (with the degraded transmitter) or replacing the 
transmitter in the original VCEIL with the one from the spare. Vaisala recommended the 
latter because the original VCEIL is a much newer unit.

On 5/16, the site operator replaced the transmitter in the original VCEIL with the one 
from the spare, realigned the optics, recalibrated the laser, and put the instrument back 
into service, successfully correcting the problem.

The data during this period were intermittently incorrect, containing warning flags and 
alarms and unreasonable cloud base heights.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Third cloud base height(third_cbh)
• Altitude of highest signal(alt_highest_signal)
• Second lowest cloud base height(second_cbh)
• Vertical visibility(vertical_visibility)

GRW/MWRP/M1 - Reprocessed: Updated calibration coefficients

On 5/15 the K-band calibrations were updated with coefficients derived from tip curves.  
The 20090501-20090515 data were reprocessed to apply the updated calibration coefficients.

• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• Retrieved water vapor density(waterVaporDensity)
• Retrieved liquid water path(liquidWaterPath)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Derived relative humidity(relativeHumidity)
• Interpolated water vapor mixing ratio(waterVaporMixingRatio)