Preprints
https://doi.org/10.5194/amt-2021-352
https://doi.org/10.5194/amt-2021-352
 
07 Mar 2022
07 Mar 2022
Status: this preprint is currently under review for the journal AMT.

Extending water vapor measurement capability of photon limited differential absorption lidars through simultaneous denoising and inversion

Willem Jacobus Marais1 and Matthew Hayman2 Willem Jacobus Marais and Matthew Hayman
  • 1Space Science Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
  • 2National Center for Atmospheric Research, Boulder, Colorado, USA

Abstract. The MicroPulse DIAL (MPD) was developed at Montana State University (MSU) and the National Center for Atmospheric Research (NCAR) to perform range resolved water vapor (WV) measurements using low power lasers and photon counting detectors. The MPD has proven to produce accurate WV measurements up to 6 km altitude. However, the MPD's ability to produce accurate higher altitude WV measurements is impeded by the current standard Differential Absorption Lidar (DIAL) retrieval methods. These methods are built upon a fundamental methodology which algebraically solves for the WV using the MPD forward models and noisy observations, which exacerbate any random noise in the lidar observations.

The work in this paper introduces the adapted Poisson Total Variation (PTV) specifically for the MPD instrument. PTV was originally developed for a ground based high spectral resolution lidar, and this paper reports on the adaptations that were required in order to apply PTV on MPD WV observations. The adapted PTV method, coined PTV-MPD, extends the maximum altitude of the MPD from 6 km to 8 km and substantially increases the accuracy of the WV retrievals starting above 2 km. PTV-MPD achieves the improvement by simultaneously denoising the MPD noisy observations and inferring the WV by separating the random noise from the non-random WV.

An analysis with 130 radiosonde (RS) comparisons shows that the relative root mean square difference (RRMSE) of WV measurements between RS and PTV-MPD exceeds 100 % between 6 and 8 km, whereas the RRMSE between RS and the standard method exceeds 100 % near 3 km. In addition, we show that by employing PTV-MPD, the MPD is able to extend its useful range of WV estimates beyond that of the ARM Southern Great Planes Raman lidar (RRMSE exceeding 100 % between 3 and 4 km); the Raman lidar has a power-aperture-product 500 times greater than that of the MPD.

Willem Jacobus Marais and Matthew Hayman

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-352', Anonymous Referee #2, 01 Apr 2022
  • RC2: 'Comment on amt-2021-352', Anonymous Referee #3, 19 May 2022

Willem Jacobus Marais and Matthew Hayman

Willem Jacobus Marais and Matthew Hayman

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Short summary
For atmospheric science and weather prediction, it is important to make water vapor measurements in real-time. A low-cost lidar instrument has been developed by Montana State University and the National Center for Atmospheric Research. We developed an advanced signal processing method to extend the scientific capability of the lidar instrument. With the new method we show that the maximum altitude at which the MPD can make water vapor measurements can be extended up to 8 km.