Publications

Yi-wen Huang, Timothy J. Dransfield, and James G. Anderson. Experimental Evidence for the Pressure Dependence of the Reaction Rate Constant between Acetic Acid and Hydroxyl Radicals. The Journal of Physical Chemistry A 2010 114 (43), 11538-11544

The reaction rate constant of acetic acid with the hydroxyl radical is measured at 93 Torr with our high-pressure flow system (HPFS) and found to display a negative temperature dependence that can be described by the Arrhenius expression, k(T) = (2.44 ± 0.22) × 10(-14) exp ((1027 ± 24)/T)) cm(3) molecule(-1) s(-1). Compared with our previously reported 7 Torr data, we find a noticeable pressure...

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...

Sayres, D.S., L. Pfister, T.F. Hanisco, E.J. Moyer, J.B. Smith, J.M. St. Clair, A.S. OBrien, M.F. Witinski, M. Legg, J. G. Anderson, Influence of Convection on the Water Isotopic Composition of the Tropical Tropopause Layer and Tropical Stratosphere, J. Geophys. Res. 115, D00J20, doi:10.1029/2009JD013100, 2010. 

We present the first in situ measurements of HDO across the tropical tropopause, obtained by the integrated cavity output spectroscopy (ICOS) and Hoxotope water isotope instruments during the Costa Rica Aura Validation Experiment (CR-AVE) and Tropical Composition, Cloud and Climate Coupling (TC4) aircraft campaigns out of Costa Rica in winter and summer, respectively. We use these data to explore...

Huang, Y., S. Leroy, P.J. Gero, J. Dykema, and J.G. Anderson (2010), Separation of Longwave Climate Feedbacks from Spectral Observations, J. Geophys. Res., 115, D07104, doi:10.1029/2009JD012766, 2010.

We conduct a theoretical investigation into whether changes in the outgoing longwave radiation (OLR) spectrum can be used to constrain longwave greenhouse-gas forcing and climate feedbacks, with a focus on isolating and quantifying their contributions to the total OLR change in all-sky conditions. First, we numerically compute the spectral signals of CO2 forcing and feedbacks of temperature,...

Leroy, S.S., and J.G. Anderson, Optical Detection of Regional Trends Using Global Data, J. Climate, 23, Issue 16 (August 2010), pp. 4438-4446, doi: http://dx.doi.org/10.1175/2010JCLI3550.1.

A complete accounting of model uncertainty in the optimal detection of climate signals requires normalization of the signals produced by climate models; however, there is not yet a well-defined rule for the normalization. This study seeks to discover such a rule. The authors find that, to arrive at the equations of optimal detection from a general application of Bayesian statistics to the problem...

Huang, Yi, Stephen S. Leroy, James G. Anderson , 2010: Determining Longwave Forcing and Feedback Using Infrared Spectra and GNSS Radio Occulation, J. Climate, 23, 6027–6035. doi: http://dx.doi.org/10.1175/2010JCLI3588.1 

The authors investigate whether combining a data type derived from radio occultation (RO) with the infrared spectral data in an optimal detection method improves the quantification of longwave radiative forcing and feedback. Signals derived from a doubled-CO2 experiment in a theoretical study are used. When the uncertainties in both data types are conservatively estimated, jointly detecting the...

Weinstock, E. M., et al. (2009), Validation of the Harvard Lyman-α in situ water vapor instrument: Implications for the mechanisms that control stratospheric water vaporJ. Geophys. Res.114, D23301, doi:10.1029/2009JD012427.

Building on previously published details of the laboratory calibrations of the Harvard Lyman-α photofragment fluorescence hygrometer (HWV) on the NASA ER-2 and WB-57 aircraft, we describe here the validation process for HWV, which includes laboratory calibrations and intercomparisons with other Harvard water vapor instruments at water vapor mixing ratios from 0 to 10 ppmv, followed by in-...

Mark F. Witinski, Joshua B. Paul, and James G. Anderson, "Pump-enhanced difference-frequency generation at 3.3 μm," Appl. Opt. 48, 2600-2606 (2009) 

The demonstration of continuous wave intracavity difference-frequency generation in the mid-infrared (mid-IR) is presented. A cavity for pump laser enhancement is constructed around a periodically poled lithium niobate crystal, and the cavity length is locked to the frequency of the pump laser using the Pound-Drever-Hall technique, producing a gain of 12 in the resultant idler power compared to...




Sayres, D. S., and Coauthors, 2009A new cavity based absorption instrument for detection of water isotopologues in the upper troposphere and lower stratosphereRev. Sci. Instrum.80044102, doi:10.1063/1.3117349.

We describe here the Harvard integrated cavity output spectroscopy (ICOS) isotope instrument, a mid-IR infrared spectrometer using ICOS to make in situ measurements of the primary isotopologues of water vapor (H2O, HDO, and H218O) in the upper troposphere and lower stratosphere (UTLS). The long path length provided by ICOS provides the sensitivity and accuracy necessary to measure...

Sprengnether MM, Demerjian KL, Dransfield TJ, Clarke JS, Anderson JG, Donahue NM.J Phys Chem A. 2009 Apr 30;113(17):5030-8.

We report absolute rate-constant measurements for the reactions of nine C(6)-C(9) alkanes with OH in 8-10 torr of nitrogen from 230 to 379 K in the Harvard University High-Pressure Flow System. Hydroxyl concentrations were measured using laser-induced fluorescence, and alkane concentrations were measured using Fourier transform infrared Spectroscopy. Ethane's reactivity was simultaneously...

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