Ground-based water vapor raman lidar measurements up to the upper troposphere and lower stratosphere for long-term monitoring

Abstract

Abstract. Recognizing the importance of water vapor in the upper troposphere and lower stratosphere (UTLS) and the scarcity of high-quality, long-term measurements, JPL began the development of a powerful Raman lidar in 2005 to try to meet these needs. This development was endorsed by the Network for the Detection of Atmospheric Composition Change (NDACC) and the validation program for the EOSAura satellite. In this paper we review the stages in the instrumental development, data acquisition and analysis, profile retrieval and calibration procedures of the lidar, as well as selected results from three validation campaigns: MOHAVE (Measurements of Humidity in the Atmosphere and Validation Experiments), MOHAVE-II, and MOHAVE 2009. In particular, one critical result from this latest campaign is the very good agreement (well below the reported uncertainties) observed between the lidar and the Cryogenic FrostPoint Hygrometer in the entire lidar range 3-20 km, with a mean bias not exceeding 2 % (lidar dry) in the lower troposphere, and 3 % (lidar moist) in the UTLS. Ultimately the lidar has demonstrated capability to measure water vapor profiles from ∼1 km above the ground to the lower stratosphere with a precision of 10 % or better near 13 km and below, and an estimated accuracy of 5 %. Since 2005, nearly 1000 profiles have been routinely measured, and since 2009, the profiles have typically reached 14 km for one-hour integration times and 1.5 km vertical resolution, and can reach 21 km for 6-h integration times using degraded vertical resolutions.These performance figures show that, with our present target of routinely running our lidar two hours per night, 4 nights per week, we can achieve measurements with a precision in the UTLS equivalent to that achieved if launching one CFH per month.

Hygroscopic growth study in the framework of EARLINET during the SLOPE I campaign: synergy of remote sensing and in-situ instrumentation

“…C is obtained as the average value of the ratio between the uncalibrated RL ( ) profile and the ( ) profile from over the height-range from 1.5 to 3.5 km a.s.l. (Guerrero-Rascado et al, 2008b;Leblanc et al, 2012;Navas-Guzmán et al 20 2014;Foth et al, 2015). C remains constant over periods when the lidar setup is not modified and the system presents good alignment, allowing us to retrieve ( ) profiles from the RL even when RS measurements are not available.…”

Water vapor observations up to the lower stratosphere through the Raman lidar during the Maïdo Lidar Calibration Campaign

“…Raman-scattering-based lidar for atmospheric water vapor measurements has been amply described in the literature (Mel, 1972;Sherlock et al, 1999b;Leblanc et al, 2012). However, to discuss the adopted technical solutions in the system configuration of RMR-H 2 O, it is useful to report the equation relating the water vapor mixing ratio (WVMR, w in the equation) to the recorded Raman signals:…”

“…To optimize the Raman lidar technique to water vapor measurements, it is necessary to quantify the systematic biases affecting the technique. In particular, several studies (Sherlock et al, 1999;Ferrare et al, 2004;Whiteman et al, 2006;Leblanc et al, 2012) have highlighted that many lidar systems experienced an excess amount of water vapor (wet bias) in the mid-upper troposphere lidar profile, significantly impacting their measurements. The recent work of Whiteman et al (2012) identified three general causes for this effect: (1) instrumental effects, (2) data processing, (3) atmospheric constituents.…”

“…In particular the most common method is using co-located radiosonde profiles because of their wide availability, better accuracy in the results compared to other sounding techniques, and a relatively wide vertical range of valid measurements. However, though no changes are performed on the lidar system, the natural variability of tropospheric water vapor can lead to calibration changes of 15 % or larger from night to night (Leblanc et al, 2012). In fact the radiosonde, during its ascension, samples different regions of the atmosphere regarding the lidar.…”

“…In particular, preliminary results on the accuracy of Raman water vapor measurements in the UTLS have been obtained (Whiteman et al, 2011b(Whiteman et al, , 2012Leblanc et al, 2012), and different calibration methodologies have been developed Leblanc et al, 2011;Hoareau et al, 2009;Dionisi et al, 2010;Reichardt et al, 2012, Bock et al, 2013. The aim is to set up a lidar reference network for upper-air climate observations of water vapor such as GRUAN (GCOS Reference Upper-Air Network, Immler et al, 2010).…”