Instruments
TMF Water Vapor Raman lidar (a.k.a. TMWAL)
General
This Raman lidar, dedicated to the measurement of upper tropospheric water vapor, was first built in 2003. It was redesigned in 2005, 2007 and 2009 in order to optimize its detection capability in the Upper Troposphere/Lower Stratosphere (~3-5 ppmv). Routine data acquisition started in 2005 and the instrument has since measured over 1000 tropospheric water vapor profiles. The measurments were last validated during the NDACC field-campaign MOHAVE-2009.
The system uses the vibrational Raman scattering of the nitrogen and water vapor molecules and includes 9 receiving channels (3 Rayleigh channels at 355 nm dedicated to temperature and aerosol measurements, 3 "nitrogen" channels at 387 nm, and 3 "water vapor" channels at 407 nm). After a few signal corrections, the ratio of the lidar signals at 407 nm and 387 nm is proportional to water vapor mixing ratio. The measurements are calibrated using a calibration lamp and routine RS92/RS41 radiosonde measurements. The combination of the various channels allows water vapor retrieval from 3 km to 15 km year-round (up to 20 km in summer and fall).
Instrument/dataset characteristics:
- Instrument vertical resolution: 75-m
- Vertical range: water vapor=[3,15] km
- Instrument temporal resolution: Typically from 5-min to 2-hours
- Typical measurement frequency: 3-5 times per week, nighttime only
- Occasional "all-night" measurements for case studies and campaigns
- Typical total number of measurements per year: 200.
References
Leblanc, T., McDermid, I. S., and Walsh, T. D.: Ground-based water vapor raman lidar measurements up to the upper troposphere and lower stratosphere for long-term monitoring, Atmos. Meas. Tech., 5, 17-36, 2012; https://doi.org/10.5194/amt-5-17-2012
Leblanc, T., et al.: Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE)-2009: overview of campaign operations and results, Atmos. Meas. Tech., 4, 2579-2605, 2011; https://doi.org/10.5194/amt-4-2579-2011
Leblanc, T., and I. S. McDermid, On the accuracy of Raman lidar water vapor calibration and its applicability to long-term measurements, Appl. Optics, 47(30), 5592-5603, 2008; https://doi.org/10.1364/AO.47.005592