Water vapor's contribution to Earth's radiative forcing is most sensitive to changes in its lower stratosphere concentration. One recognized pathway for rapid increases in stratospheric water vapor is tropopause-overshooting convection. Since this pathway has been rarely sampled, the NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field project focused on obtaining in situ...
David Sayres's Publications
Homeyer, C. R., J. B. Smith, K. M. Bedka, K. P. Bowman, D. M. Wilmouth, R. Ueyama, J. M. Dean-Day, J. M. St. Clair, R. Hannun, J. Hare, A. Pandey, D. S. Sayres, T. F. Hanisco, A. E. Gordon, and E. N. Tinney, Extreme altitudes of stratospheric hydration by midlatitude convection observed during the DCOTSS field campaign. Geophys. Res. Lett., 50, e2023GL104914, 2023, doi: 10.1029/2023GL104914.
Wilmouth, D. M., and D. S. Sayres, Determination of Rayleigh scattering cross sections and indices of refraction for Ar, CO2, SF6, and CH4 using BBCES in the ultraviolet. J. Quant. Spectrosc. Radiat. Transfer, 255, 107224, 2020, doi:10.1016/j.jqsrt.2020.107224.
Accurate Rayleigh scattering cross sections are important for understanding the propagation of electromagnetic radiation in planetary atmospheres and for calibrating mirror reflectivity in high finesse optical cavities. In this study, we used Broadband Cavity Enhanced Spectroscopy (BBCES) to measure Rayleigh scattering cross sections for argon, carbon dioxide, sulfur hexafluoride, and...
Wilmouth, D. M., and D. S. Sayres (2019), Rayleigh scattering cross sections of argon, carbon dioxide, sulfur hexafluoride, and methane in the UV-A region using Broadband Cavity Enhanced Spectroscopy, Journal of Quantitative Spectroscopy and Radiative Transfer 234, 32-39, doi:10.1016/j.jqsrt.2019.05.031.
Accurate Rayleigh scattering cross sections are important for understanding the propagation of electromagnetic radiation in planetary atmospheres and for calibrating mirror reflectivity in high finesse optical cavities. In this study, we used Broadband Cavity Enhanced Spectroscopy (BBCES) to measure Rayleigh scattering cross sections for argon, carbon dioxide, sulfur hexafluoride, and methane...
Wilkerson, J., R. Dobosy, D. S. Sayres, C. Healy, E. Dumas, B. Baker, and J. G. Anderson (2019), Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method, Atmos. Chem. Phys., 19 (7), 4257-4268, doi:10.5194/acp-19-4257-2019.
The microbial by-product nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance, has conventionally been assumed to have minimal emissions in permafrost regions. This assumption has been questioned by recent in situ studies which have demonstrated that some geologic features in permafrost may, in fact, have elevated emissions comparable to those of tropical soils. However,...
Anderson, J. G., D. K. Weisenstein, K. P. Bowman, C. R. Homeyer, J. B. Smith, D. M. Wilmouth, D. S. Sayres, J. E. Klobas, S. S. Leroy, J. A. Dykema, and S. C. Wofsy (2017), Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis, Proceedings of the National Academy of Sciences 114: E4905-E4913; doi: 10.1073/pnas.1619318114.
We present observations defining (i) the frequency and depth of convective penetration of water into the stratosphere over the United States in summer using the Next-Generation Radar system; (ii) the altitude-dependent distribution of inorganic chlorine established in the same coordinate system as the radar observations; (iii) the high resolution temperature structure in the stratosphere over the...
Sayres, D. S., R. Dobosy, C. Healy, E. Dumas, J. Kochendorfer, J. Munster, J. Wilkerson, B. Baker, and J. G. Anderson (2017), Arctic regional methane fluxes by ecotope as derived using eddy covariance from a low-flying aircraft, Atmos. Chem. Phys. 17(13): 8619-8633; doi: 10.5194/acp-17-8619-2017.
The Arctic terrestrial and sub-sea permafrost region contains approximately 30 % of the global carbon stock, and therefore understanding Arctic methane emissions and how they might change with a changing climate is important for quantifying the global methane budget and understanding its growth in the atmosphere. Here we present measurements from a new in situ flux observation system designed for...
Dobosy, R., D. Sayres, C. Healy, E. Dumas, M. Heuer, J. Kochendorfer, B. Baker, and J. Anderson (2017), Estimating random uncertainty in airborne flux measurements over Alaskan tundra: Update on the Flux Fragment Method, J. Atmos. Oceanic Technol., in press; doi: 10.1175/JTECH-D-16-0187.1.
Airborne turbulence measurement gives a spatial distribution of air-surface fluxes that networks of fixed surface sites typically can not capture. Much work has improved the accuracy of such measurements and the estimation of the uncertainty peculiar to streams of turbulence data measured from the air. A particularly significant challenge and opportunity is to distinguish fluxes from different...
Anderson, J. G., D. M. Wilmouth, J. B. Smith, and D. S. Sayres, UV Dosage Levels in Summer: Increased Risk of Ozone Loss from Convectively Injected Water Vapor, Science 337, 835 (2012).
The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic...
Dobosy, R., E. J. Dumas, D. L. Senn, B. Baker, D. S. Sayres, M. F. Witinski, C. Healy, J. Munster, and J. G. Anderson (2012), Calibration and Quality Assurance of an Airborne Turbulence Probe in an Aeronautical Wind Tunnel, J. Atmos. Oceanic Technol. 30: 182-196; doi:10.1175/JTECH-D-11-00206.1.
The Best Aircraft Turbulence (BAT) probe is used by multiple research groups worldwide. To promote an accurate interpretation of the data obtained from the probe’s unusual nine-port design, a detailed understanding of the BAT probe’s function along with a characterization and minimization of its systematic anomalies is necessary. This paper describes recent tests to enhance understanding of...
M.F. Witinski, D.S. Sayres, and J.G. Anderson, High Precision Methane Isotopologue Ratio Measurement at Ambient Mixing Ratios Using Integrated Cavity Output Spectroscopy, App. Phys. B: Lasers and Optics, doi: 10.1077/s00340-010-3957-2, March 2010.
The demonstration of an ultra-sensitive infrared spectro- scopic technique for analysis of carbon isotopologues of methane is presented. Using off-axis integrated cavity output spectroscopy (ICOS) near 1294 cm−1, we have achieved a δ13C measurement precision of 1.5‰ in 1 s and 0.21‰ in 200 s while sampling dry air with a 12CH4 mixing ratio of 1.846 ppmv. This method will allow for high time...