Simultaneous analog and photon counting detection for Raman lidar.

Area of Science:

• Atmospheric science
• Remote sensing
• Lidar technology

Background:

• The Atmospheric Radiation Measurement (ARM) program's Raman lidar underwent a significant upgrade in 2004.
• The upgrade introduced a new data system capable of simultaneous measurements of analog output voltage and photon counts.

Purpose of the Study:

• To improve the dynamic range and accuracy of water vapor mixing ratio measurements.
• To refine the algorithm for merging dual signals from the upgraded lidar system.

Main Methods:

• Development and implementation of an improved algorithm for merging lidar signals.
• Comparison of lidar-derived water vapor mixing ratio profiles with radiosonde measurements over a six-month period.

Main Results:

• The modified algorithm significantly reduced the mean bias in daytime water vapor mixing ratio from 3% to within 1%.
• This improvement was achieved by utilizing only nighttime average glue coefficients throughout the diurnal cycle, disregarding temporal variations.

Conclusions:

• The enhanced lidar data processing algorithm substantially improves the accuracy of water vapor measurements.
• The revised method ensures reliable water vapor mixing ratio data for atmospheric research and climate modeling.