Denning A. S.

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A. S.

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  • Article
    Moist synoptic transport of CO2 along the mid-latitude storm track
    (American Geophysical Union, 2011-05-12) Parazoo, N. C. ; Denning, A. S. ; Berry, J. A. ; Wolf, Aaron S. ; Randall, D. A. ; Kawa, S. Randolph ; Pauluis, O. ; Doney, Scott C.
    Atmospheric mixing ratios of CO2 are strongly seasonal in the Arctic due to mid-latitude transport. Here we analyze the seasonal influence of moist synoptic storms by diagnosing CO2 transport from a global model on moist isentropes (to represent parcel trajectories through stormtracks) and parsing transport into eddy and mean components. During winter when northern plants respire, warm moist air, high in CO2, is swept poleward into the polar vortex, while cold dry air, low in CO2, that had been transported into the polar vortex earlier in the year is swept equatorward. Eddies reduce seasonality in mid-latitudes by ∼50% of NEE (∼100% of fossil fuel) while amplifying seasonality at high latitudes. Transport along stormtracks is correlated with rising, moist, cloudy air, which systematically hides this CO2 transport from satellites. We recommend that (1) regional inversions carefully account for meridional transport and (2) inversion models represent moist and frontal processes with high fidelity.
  • Article
    Precision requirements for space-based XCO2 data
    (American Geophysical Union, 2007-05-26) Miller, C. E. ; Crisp, D. ; DeCola, P. L. ; Olsen, S. C. ; Randerson, James T. ; Michalak, Anna M. ; Alkhaled, A. ; Rayner, Peter ; Jacob, Daniel J. ; Suntharalingam, Parvadha ; Jones, D. B. A. ; Denning, A. S. ; Nicholls, M. E. ; Doney, Scott C. ; Pawson, S. ; Boesch, H. ; Connor, B. J. ; Fung, Inez Y. ; O'Brien, D. ; Salawitch, R. J. ; Sander, S. P. ; Sen, B. ; Tans, Pieter P. ; Toon, G. C. ; Wennberg, Paul O. ; Wofsy, Steven C. ; Yung, Y. L. ; Law, R. M.
    Precision requirements are determined for space-based column-averaged CO2 dry air mole fraction (XCO2) data. These requirements result from an assessment of spatial and temporal gradients in XCO2, the relationship between XCO2 precision and surface CO2 flux uncertainties inferred from inversions of the XCO2 data, and the effects of XCO2 biases on the fidelity of CO2 flux inversions. Observational system simulation experiments and synthesis inversion modeling demonstrate that the Orbiting Carbon Observatory mission design and sampling strategy provide the means to achieve these XCO2 data precision requirements.