What can <sup>14</sup>CO measurements tell us about OH?

Abstract

Abstract. The possible use of 14 CO measurements to constrain hydroxyl radical (OH) concentrations in the atmosphere is investigated. 14 CO is mainly produced in the upper atmosphere from cosmic radiation. Measurements of 14 CO at the surface show lower concentrations compared to the upper atmospheric source region, which is the result of oxidation by OH. In this paper, the sensitivity of 14 CO mixing ratio surface measurements to the 3-D OH distribution is assessed with the TM5 model. Simulated 14 CO mixing ratios agree within a few molecules 14 CO cm −3 (STP) with existing measurements at five locations worldwide. The simulated cosmogenic 14 CO distribution appears mainly sensitive to the assumed upper atmospheric 14 C source function, and to a lesser extend to model resolution. As a next step, the sensitivity of 14 CO measurements to OH is calculated with the adjoint TM5 model. The results indicate that 14 CO measurements taken in the tropics are sensitive to OH in a spatially confined region that varies strongly over time due to meteorological variability. Given measurements with an accuracy of 0.5 molecules 14 CO cm −3 STP, a good characterization of the cosmogenic 14 CO fraction, and assuming perfect transport modeling, a single 14 CO measurement may constrain OH to 0.2-0.3×10 6 molecules OH cm −3 on time scales of 6 months and spatial scales of 70×70 degrees (latitude×longitude) between the surface and 500 hPa. The sensitivity of 14 CO measurements to high latitude OH is about a factor of five higher. This is in contrast with methyl chloroform (MCF) measurements, which show the highest sensitivity to tropical OH, Correspondence to: M. C. Krol (m.c.krol@uu.nl) mainly due to the temperature dependent rate constant of the MCF-OH reaction. A logical next step will be the analysis of existing 14 CO measurements in an inverse modeling framework. This paper presents the required mathematical framework for such an analysis.

Inverse modeling of European CH<sub>4</sub> emissions: sensitivity to the observational network

“…3d, e, and f) for single station back-plume simulations. The latter represent annual mean sensitivities of atmospheric measurements to CH 4 emissions (similarly as described in Krol et al, 2008, with units in ppb/(kg/s)). We observe that the inversions retain the a priori emission value over those European areas where the annual mean sensitivities are small.…”

Inverse modelling of CH<sub>4</sub> emissions for 2010–2011 using different satellite retrieval products from GOSAT and SCIAMACHY

“…(2) is minimized using the algorithm M1QN3 (Gilbert and Lemaréchal, 1989). The adjoint model (Meirink et al, 2008b;Krol et al, 2008) allows for an efficient computation of the gradient of J during the minimization process. TM5 is an offline transport model (Krol et al, 2005) driven by the ERA-Interim re-analysis meteorological data from ECMWF.…”

Nested atmospheric inversion for the terrestrial carbon sources and sinks in China

“…Monthly transport operator M of ten years (January 2000 to December 2009) for the 43 regions is calculated using the global two-way nested transport model TM5 , which has been evaluated extensively and consistently and performs well on vertical and horizontal transport in ongoing intercomparisons (Stephens et al, 2007), and it has been widely used in global atmospheric chemistry studies (e.g., Houweling et al, 1998;Dentener et al, 2003;Peters et al, 2002) and atmospheric inversion research (e.g., Meirink et al, 2008;Krol et al, 2008;Peters, et al, 2007). TM5 is an off-line model that is driven by meteorological fields from the ECMWF model.…”