Abstract Micropulse differential absorption lidar (MPD) for water vapor, temperature, and aerosol profiling have been developed, demonstrated, and are addressing the needs of the atmospheric science community for low-cost ground-based networkable instruments capable of long-term monitoring of the lower troposphere. The MPD instruments use a diode-laser-based (DLB) architecture that can easily be adapted for a wide range of applications. In this study, a DLB direct detection Doppler lidar based on the current MPD architecture is modeled to better understand the efficacy of the instrument for vertical wind velocity measurements with the long-term goal of incorporating these measurements into the current network of MPD instruments. The direct detection Doppler lidar is based on a double-edge receiver that utilizes two Fabry-Perot interferometers and a vertical velocity retrieval that requires the ancillary measurement of the backscatter ratio, which is the ratio of the total backscatter coefficient to the molecular backscatter coefficient. The modeling in this paper accounts for the major sources of error. It indicates that the vertical velocity can be retrieved with an error of less than 0.56 m s −1 below 4 km with a 150-m range resolution and an averaging time of five minutes.
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Extending water vapor measurement capability of photon-limited differential absorption lidars through simultaneous denoising and inversion
Abstract. The micropulse differential absorption lidar (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 that algebraically solves for the WV using the MPD forward models and noisy observations, which exacerbates 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 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 Plains 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.
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- Award ID(s):
- 1930907
- PAR ID:
- 10382636
- Date Published:
- Journal Name:
- Atmospheric Measurement Techniques
- Volume:
- 15
- Issue:
- 17
- ISSN:
- 1867-8548
- Page Range / eLocation ID:
- 5159 to 5180
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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This work presents the first demonstration of atmospheric temperature measurement using the differential absorption lidar (DIAL) technique. While DIAL is routinely used to measure atmospheric gases such as ozone and water vapor, almost no success has been found in using DIAL to measure atmospheric temperature. Attempts to measure temperature using a well-mixed gas like oxygen (
O 2) have largely failed based on a need for quantitative ancillary measurements of water vapor and atmospheric aerosols. Here, a lidar is described and demonstrated that simultaneously measuresO 2absorption, water vapor number density, and aerosol backscatter ratio. This combination of measurements allows for the first measurements of atmospheric temperature with useful accuracy. DIAL temperature measurements are presented to an altitude of 4km with 225m and 30min resolution with accuracy better than 3K . DIAL temperature data is compared to a co-located Raman lidar system and radiosondes to evaluate the system’s performance. Finally, an analysis of current performance characteristics is presented, which highlights pathways for future improvement of this proof-of-concept instrument. -
Traditionally, quantitative lidar techniques like differential absorption lidar (DIAL) and high-spectral-resolution lidar (HSRL) utilize high-power-aperture product designs, which partially compensates for the need to take discrete deriva-tives of noisy data in post-processing (for number density for DIAL and extinction for HSRL) and provides for high-performance measurements, i.e., higher resolu-tion, accuracy, or precision. Conversely, low-power-aperture product lidar designs are easier to make eye-safe, reliable, and cost-effective, which are important attributes for network development and field deployment. The atmospheric science community has expressed the need for high-quality, quantitative, robust, network deployable, and cost-effective sensors for a variety of applications such as improved numerical weather forecasting – in essence requiring the best of both worlds without the accompanying drawbacks. In response to this need, the National Center for Atmospheric Research and Montana State University have been developing the MicroPulse DIAL (MPD) architecture for thermodynamic profiling in the lower atmosphere. The MPD architecture takes advantage of the benefits of low-power, low-cost laser diodes, and fiber optics to achieve quantitative profiling leverag-ing narrowband filtering and efficient elastic scattering. A field-deployable MPD instrument capable of humidity, quantitative aerosol, and temperature profiling has recently been developed. This presentation will describe the current status of this thermodynamic profiler and the initial results from a recent field deployment. Emphasis will be given to the analysis of the temperature data including compar-isons to co-located radiosondes to describe current performance.more » « less
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Abstract The climatology of earth's Na density over Fort Collins, CO (41°N, 105°W) based on nocturnal Na lidar observations between 1990 and 1999 was reported by She et al. (2000,
https://doi.org/10.1029/2000gl003825 ). Based on a continued 28‐year data set between 1990 and 2017 with the latter part observed over Logan, UT (42N, 112W), we update the seasonal variations between 80 and 110 km. This data set is also used to deduce long‐term responses of Na density (profile) between 75 and 110 km, showing a positive linear trend between 75 and 93 km (with maximum ∼2.87 × 108 m−3/decade at 87 km); it turns negative before approaching zero at 110 km (with minimum ∼−2.96 × 107 m−3/decade at 100 km). The associated solar response is also positive for the altitude range in question (with maximum ∼5.20 × 106 m−3/SFU at 91 km). We also derived the 28‐year mean Na layer column abundance, centroid altitude, and root mean square width to be 3.92 ± 2.14 1013 m−2, 91.3 ± 1.0 km, and 4.62 ± 0.56 km, respectively, and deduced long‐term trend and solar cycle responses of column abundance and centroid altitude, respectively to be 7.81 ± 1.63%/decade and 16.9 ± 2.8%/100SFU, and −355 ± 35 m/decade and −1.94 ± 0.69 m/SFU. We explained conceptually how positive long‐term responses in Na density led to positive responses in column abundance and negative responses in centroid altitude. -
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Abstract The National Center for Atmospheric Research (NCAR) and Montana State University jointly developed water vapor micropulse differential absorption lidars (MPDs) that are a significant advance in eye-safe, unattended, lidar-based water vapor remote sensing. MPD is designed to provide continuous vertical water vapor profiles with high vertical (150 m) and temporal resolution (5 min) in the lower troposphere. This study aims to investigate MPD observation impacts and the scientific significance of MPDs for convective weather analyses and predictions using observation system simulation experiments (OSSEs). In this study, the Data Assimilation Research Testbed (DART) and the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) Model are used to conduct OSSEs for a case study of a mesoscale convective system (MCS) observed during the Plains Elevated Convection At Night (PECAN) experiment. A poor-performing control simulation that was drawn from a 40-member ensemble at 3-km resolution is markedly improved by assimilation of simulated observations drawn from a more skillful simulation that served as the nature run at 1-km resolution. In particular, assimilating surface observations corrected surface warm front structure errors, while MPD observations remedied errors in low- to midlevel moisture ahead of the MCS. Collectively, these analyses changes led to markedly improved short-term predictions of convection initiation, evolution, and precipitation of the MCS in the simulations on 15 July 2015. For this case study, the OSSE results indicate that a more dense MPD network results in better prediction performance for convective precipitation while degrading light precipitation prediction performance due to an imbalance of the analysis at large scales.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/amt-15-5159-2022
