Russell J. DeYoung

Results from the NASA GSFC and LaRC Ozone Lidar Intercomparison: New Mobile Tools for Atmospheric Research

AbstractDuring a 2-week period in May 2014, the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center Tropospheric Ozone Differential Absorption Lidar (GSFC TROPOZ DIAL) was situated near the NASA Langley Research Center (LaRC) Mobile Ozone Lidar (LMOL) and made simultaneous measurements for a continuous 15-h observation period in which six separate ozonesondes were launched to provide reference ozone profiles. Although each of these campaign-ready lidars has very different transmitter and receiver components, they produced very similar ozone profiles, which were mostly within 10% of each other and the ozonesondes. The observed column averages as compared to the ozonesondes also agree well and are within 8% of each other. A robust uncertainty analysis was performed, and the results indicate that there is no statistically significant systematic bias between the TROPOZ and LMOL instruments. With the extended measurements and ozonesonde launches, this intercomparison has yielded an...

High-energy, efficient, 30-Hz ultraviolet laser sources for airborne ozone-lidar systems

Two compact, high-pulse-energy, injection-seeded, 30-Hz frequency-doubled Nd:YAG-laser-pumped Ti: sapphire lasers were developed and operated at infrared wavelengths of 867 and 900 nm. Beams with laser pulse energy >30 mJ at ultraviolet wavelengths of 289 and 300 nm were generated through a tripling of the frequencies of these Ti:sapphire lasers. This work is directed at the replacement of dye lasers for use in an airborne ozone differential absorption lidar system. The ultraviolet pulse energy at 289 and 300 nm had 27% and 31% absolute optical energy conversion efficiencies from input pulse energies at 867 and 900 nm, respectively.

Narrowband fiber-optic phase-shifted Fabry–Perot Bragg grating filters for atmospheric water vapor lidar measurements

A unique ultranarrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filter for atmospheric water vapor lidar measurements was designed, fabricated, and successfully tested. Customized optical fiber Bragg gratings were fabricated so that two transmission filter peaks occurred: one (89% transmission, 8 pm FWHM) near the 946-nm water vapor absorption line and the other peak (80% transmission, 4 pm FWHM) at a region of no absorption. Both transmission peaks were within a 2.66-nm stop band. Demonstration of tension tuning to the 946.0003-nm water vapor line was achieved, and the performance characterization of custom-made optical fiber Bragg grating filters are presented. These measurements are successfully compared to theoretical calculations using a piecewise-matrix form of the coupled-mode equations.

Comparison between super low ionization ratio and reach through avalanche photodiode structures

Avalanche photodiodes (APD) are solid state quantum detectors suitable for low level light detection in the visible and near infrared regions. These devices are commercially available from many manufacturers and are fabricated using several different solid state structures. In this paper a comparison between the well developed reach through structure (RTS) aPd and the relatively newer super low ionization ratio, k, (SLIK) APD structure will be discussed. The comparison is based on the experimental characterization of two APDs with these structures. The characterization setup and experiments will be described which include the calibration of the APDs, temperature response, bias voltage response, and noise measurements including noise-equivalent-power and detectivity D*. For this comparison the selected RTS APD is the EG&G C30955E, currently used by the lidar atmospheric sensing experiment (LASE) instrument. The selected SLIK ApD is the EG&G C30649E, which is proposed for LASE development. The characterization experiments where done in order to develop an advanced atmospheric water vapor differential absorption lidar detection system.

Drift-diffusion model for reach-through avalanche photodiodes

A 1-D drift-diffusion model is developed for reach-through avalanche photodiodes. Based on this model an equivalent circuit is suggested for these devices. The equivalent circuit is suitable for simulating the device in circuit simulation packages such as PSpice. The model is validated by simulating an actual reach-through silicon avalanche photodiode in the steady state and the transient conditions. Some of the simulation results are compared to the manufacturer data by estimating the device parameters. This model is also used to investigate the effect of the device microstructure on its performance. For a certain operating bias voltage and wavelength, it is found that the multiplication width has a critical value for defining the device stability. The absorption width defines the wavelength for peak responsivity, which suggests a structure enhancement for IR detection. Also the effect of varying the doping concentration is studied.

Application of satellite data for three-dimensional monitoring of PM2.5 formation and transport in San Joaquin Valley, California

High resolution (5x5 km2 horizontal resolution) retrievals of aerosol optical depth (AOD) from the MODerate Resolution Imaging Spectroradiometer (MODIS) instruments aboard NASAs Aqua and Terra satellite platforms have been examined. These data products have been compared to coincident, hourly measurements of ground-based PM-2.5 routinely obtained by the San Joaquin Valley Air Pollution Control District (SJV APCD) and California Air Resources Board (CARB) and to airborne light detection and ranging (lidar) aerosol scattering measurements obtained by NASA in July 2003 in San Joaquin Valley (SJV). Comparison of MODIS AOD to ground based PM-2.5 measurement shows significant improvement for the higher resolution MODIS AOD. Lidar aerosol scattering measurements correspond well to MODIS AOD during a variety of atmospheric conditions, and throughout the SJV. Future lidar measurements are proposed to establish a high resolution vertical link between satellite and ground-based measurements during the winter. With the data from these two episodes, we plan to characterize the horizontal, vertical, and temporal distribution of PM-2.5 in SJV and evaluate the need for future intensive ground-based measurement and modeling studies in SJV.

Compact solid-state dye polymer laser for ozone lidar applications

A solid-state dye laser for potential application as an ozone lidar transmitter is described. The solid-state dye laser material is made from a polymer host polymethyl methacrylate (PMMA) injected with a pyrromethene laser dye PM-597. The laser oscillator cavity is end-pumped by a Q-switched Nd:YAG laser at 532 nm. Broadband and narrowband laser oscillator cavities were constructed and tested. For the broadband oscillator, slope efficiency as high as 79% was achieved. A narrowband laser oscillator was constructed to generate radiation at 578 and 600 nm with 390-pm linewidth. This output was frequency doubled to 289 or 300 nm using a beta-barium borate (BBO) crystal. The oscillator cavity generated a maximum energy of 11 mJ at 578 nm when pumped by 100 mJ, 532 nm, at 10-Hz repetition rate. Maximum output energy of 380 μJ was achieved at a wavelength of 289 nm.

Using Lidar Elevation Data to Develop a Topobathymetric Digital Elevation Model for Sub-Grid Inundation Modeling at Langley Research Center

ABSTRACT Loftis, J.D.; Wang, H.V.; DeYoung, R.J., and Ball, W.B., 2016. Using lidar elevation data to develop a topobathymetric digital elevation model for sub-grid inundation modeling at Langley Research Center. In: Brock, J.C.; Gesch, D.B.; Parrish, C.E.; Rogers, J.N., and Wright, C.W. (eds.), Advances in Topobathymetric Mapping, Models, and Applications. Journal of Coastal Research, Special Issue, No. 76, pp. 134–148. Coconut Creek (Florida), ISSN 0749-0208. Technological progression in light detection and ranging permits the production of highly detailed digital elevation models, which are useful in sub-grid hydrodynamic modeling applications. Sub-grid modeling technology is capable of incorporating these high-resolution lidar-derived elevation measurements into the conventional hydrodynamic modeling framework to resolve detailed topographic features for inclusion in a hydrological transport model for runoff simulations. The horizontal resolution and vertical accuracy of the digital elevation model is augmented via inclusion of these lidar elevation values on a nested 5-m sub-grid within each coarse computational grid cell. This aids in resolving ditches and overland drainage infrastructure at Langley Research Center to calculate runoff induced by the heavy precipitation often accompanied with tropical storm systems, such as Hurricane Irene (2011) and Hurricane Isabel (2003). Temporal comparisons of model results with a NASA tide gauge during Hurricane Irene yielded a good R2 correlation of 0.97, and root mean squared error statistic of 0.079 m. A rigorous point-to-point comparison between model results and wrack line observations collected at several sites after Hurricane Irene revealed that when soil infiltration was not accounted for in the model, the mean difference between modeled and observed maximum water levels was approximately 10%. This difference was reduced to 2–5% when infiltration was considered in the model formulation, ultimately resulting in the sub-grid model more accurately predicting the horizontal maximum inundation extents within 1.0–8.5 m of flood sites surveyed. Finally, sea-level rise scenarios using Hurricane Isabel as a base case revealed future storm-induced inundation could extend 0.5–2.5 km inland corresponding to increases in mean sea level of 37.5–150 cm.

Regional Aerosol Transport Study Using a Compact Aircraft Lidar

A compact aircraft lidar using a Nd:YAG pulsed laser, fiber coupled telescope, and three-channel receiver was flown in the Norfolk-Virginia Beach and California Central Valley regions to show lidar can reveal complex regional aerosol distributions.

Compact high-pulse-energy ultraviolet laser source for ozone lidar measurements

An all solid-state Ti:sapphire laser differential absorption lidar transmitter was developed. This all-solid-state laser provides a compact, robust, and highly reliable laser transmitter for potential application in differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy-pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 and 900 nm, with M2 of 1.3, have been experimentally demonstrated and their properties compared with model results. The output pulse energy was 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively. At these energies, the beam quality was good enough so that we were able to achieve 30 mJ of ultraviolet laser output at 289 and 300 nm after frequency tripling with two lithium triborate nonlinear crystals.