James B. Burkholder

Bio: James B. Burkholder is an academic researcher from Earth System Research Laboratory. The author has contributed to research in topics: Absorption spectroscopy & Absorption (electromagnetic radiation). The author has an hindex of 36, co-authored 84 publications receiving 4185 citations. Previous affiliations of James B. Burkholder include Cooperative Institute for Research in Environmental Sciences.

Investigation of the loss processes for peroxyacetyl nitrate in the atmosphere: UV photolysis and reaction with OH

Abstract: The UV absorption cross sections of peroxyacetyl nitrate (PAN), CH 3 C(O)O 2 NO 2 , have been measured as a function of temperature (298, 273, and 250 K) between 195 and 345 nm using a diode array spectrometer. The absorption cross sections decrease monotonically with increasing wavelength. The cross sections also decrease as the temperature is lowered. Upper limits for the rate coefficients for the reaction of OH with PAN at atmospheric temperatures were determined to be <3×10 −14 cm 3 molecule −1 s −1 using the pulsed photolysis laser induced fluorescence technique. Photolysis becomes the most important atmospheric loss process for PAN above ∼7 km, and the OH reaction is found to be unimportant throughout the troposphere. These results are compared with previous measurements, and the significance of the revised values on the atmospheric loss rates of PAN is discussed.

Ultraviolet absorption cross sections of chlorine oxide (Cl2O2) between 210 and 410 nm

Abstract: The ultraviolet and infrared absorption cross sections of Cl{sub 2}O{sub 2} have been measured. The transient Cl{sub 2}O{sub 2} molecule was produced by using the gas-phase reaction ClO + ClO + M {yields} Cl{sub 2}O{sub 2} + M. Three independent ClO radical source reactions were used in this study: Cl + O{sub 3}, Cl + Cl{sub 2}O, and Cl + OClO. The Cl{sub 2}O{sub 2} UV absorption spectrum was recorded over the range 200-450 nm with a diode array spectrometer over the temperature range 205-250 K. The Cl{sub 2}O{sub 2} infrared absorption spectrum was recorded with a high-resolution Fourier transform spectrometer over the range 500-2,000 cm{sup {minus}1}. Both spectrometers were optically coupled to a fast flow multipass absorption cell. The UV absorption spectrum of Cl{sub 2}O{sub 2} is a structureless continuum with a peak at 245 nm. The measurable absorption extends out to 410 nm. The UV absorption cross section at the peak of the spectrum, 245 nm, was measured to be (6.5{sub {minus}0.5}{sup +0.8}) {times} 10{sup {minus}18} cm{sup 2}. Infrared absorption features centered at 560, 653, and 750 cm{sup {minus}1} have been assigned to the Cl{sub 2}O{sub 2} molecule. The present results are compared with other reported UV andmore » IR measurements and the sources of discrepancies are discussed. The role of Cl{sub 2}O{sub 2} in atmospheric chemistry and in particular the Antarctic ozone hole are discussed.« less

H+O3 Fourier‐transform infrared emission and laser absorption studies of OH (X 2Π) radical: An experimental dipole moment function and state‐to‐state Einstein A coefficients

Abstract: FTIR emission/absorption spectroscopy is used to measure the relative intensities of 88 pairs of rovibrational transitions of OH(X2Pi) distributed over 16 vibrational bands. The experimental technique used to obtain the Einstein A ratios is discussed. The dipole moment function which follows from the intensity ratios along with Einstein A coefficients calculated from mu(r) is presented.

Vibrational and electronic spectroscopy of sulfuric acid vapor

Abstract: We have measured and analyzed the infrared (IR), near-infrared (NIR) and vacuum ultraviolet (VUV) absorption spectra of vapor-phase sulfuric acid (H2SO4). Transitions associated with the fundamental vibrations and the first and second OH stretching overtones of this molecule have been identified. Our measured vibrational spectrum extends and complements those in the literature and agrees well with ab initio calculated spectra. We have calculated the fundamental and overtone OH stretching intensities with the use of a simple anharmonic oscillator local-mode model with ab initio calculated dipole-moment functions. Theory and experiment have been used to investigate the OH stretching vibrational overtones of H2SO4 and indicate that the OH stretching mode in H2SO4 is an important aspect of the spectroscopy of this atmospheric chromophore. We have attempted to measure the VUV spectrum of vapor-phase sulfuric acid and, in the absence of observed bands, give upper bounds to the photoabsorption cross section. We ...

The HITRAN 2008 molecular spectroscopic database

Abstract: This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.

Nitric oxide, superoxide, and peroxynitrite: the good, the bad, and ugly.

Abstract: Nitric oxide contrasts with most intercellular messengers because it diffuses rapidly and isotropically through most tissues with little reaction but cannot be transported through the vasculature due to rapid destruction by oxyhemoglobin. The rapid diffusion of nitric oxide between cells allows it to locally integrate the responses of blood vessels to turbulence, modulate synaptic plasticity in neurons, and control the oscillatory behavior of neuronal networks. Nitric oxide is not necessarily short lived and is intrinsically no more reactive than oxygen. The reactivity of nitric oxide per se has been greatly overestimated in vitro because no drain is provided to remove nitric oxide. Nitric oxide persists in solution for several minutes in micromolar concentrations before it reacts with oxygen to form much stronger oxidants like nitrogen dioxide. Nitric oxide is removed within seconds in vivo by diffusion over 100 microns through tissues to enter red blood cells and react with oxyhemoglobin. The direct toxicity of nitric oxide is modest but is greatly enhanced by reacting with superoxide to form peroxynitrite (ONOO-). Nitric oxide is the only biological molecule produced in high enough concentrations to out-compete superoxide dismutase for superoxide. Peroxynitrite reacts relatively slowly with most biological molecules, making peroxynitrite a selective oxidant. Peroxynitrite modifies tyrosine in proteins to create nitrotyrosines, leaving a footprint detectable in vivo. Nitration of structural proteins, including neurofilaments and actin, can disrupt filament assembly with major pathological consequences. Antibodies to nitrotyrosine have revealed nitration in human atherosclerosis, myocardial ischemia, septic and distressed lung, inflammatory bowel disease, and amyotrophic lateral sclerosis.

Bounding the role of black carbon in the climate system: A scientific assessment

Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

Anthropogenic and Natural Radiative Forcing

Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)