Publications

Spackman, J. R., E. M. Weinstock, J. G. Anderson, D. F. Hurst, H.-J. Jost, and S. M. Schauffler (2007), Aircraft observations of rapid meridional transport from the tropical tropopause layer into the lowermost stratosphere: Implications for midlatitude ozoneJ. Geophys. Res.112, D12308, doi:10.1029/2006JD007618.

Meridional transport from the tropics redistributes ozone and water vapor at middle and high latitudes. In situ measurements of water vapor, CH4, and N2O, acquired aboard the NASA ER-2 aircraft during January-March 2000 in a campaign to survey the Arctic vortex, are used to examine transport into the lowermost stratosphere in the context of middle- and high-latitude ozone declines observed over...

James G. Anderson, David M. Wilmouth, Jessica B. Smith, and David 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...

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...

Wilmouth, D.M., T.F. Hanisco, R.M. Stimpfle, and J.G. Anderson, Chlorine-Catalyzed Ozone Destruction: Cl Atom Production from ClOOCl Photolysis, J. Phys. CHem. A, 113, 14099-14108, doi:10.1021/JP9053204, 2009.

Recent laboratory measurements of the absorption cross sections of the ClO dimer, ClOOCl, have called into question the validity of the mechanism that describes the catalytic removal of ozone by chlorine. Here we describe direct measurements of the rate-determining step of that mechanism, the production of Cl atoms from the photolysis of ClOOCl, under laboratory conditions similar to those in the...

Sayres, D.S., E.J. Moyer, T.F. Hanisco, J.M. Clair, F.N. Keutsch, A. O’Brien, N.T. Allen, L.Lapson, J.N. Demusz, M. Rivero, T. Martin, M. Greenberg, C. Tuozzolo, G.S. Engel, J.H. Kroll, J.B. Paul, and J.G. Anderson, A New Cavity Based Absorption Instrument for Detection of Water Isotopologues in the Upper Troposphere and Lower Stratosphere, Review of Scientific Instruments, 80, 2009.

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...

Pages