Showing papers by "David J. Erickson published in 2013"

Implementation of the chemistry module MECCA (v2.5) in the modal aerosol version of the Community Atmosphere Model component (v3.6.33) of the Community Earth System Model

Abstract: . A coupled atmospheric chemistry and climate system model was developed using the modal aerosol version of the National Center for Atmospheric Research Community Atmosphere Model (modal-CAM; v3.6.33) and the Max Planck Institute for Chemistry's Module Efficiently Calculating the Chemistry of the Atmosphere (MECCA; v2.5) to provide enhanced resolution of multiphase processes, particularly those involving inorganic halogens, and associated impacts on atmospheric composition and climate. Three Rosenbrock solvers (Ros-2, Ros-3, RODAS-3) were tested in conjunction with the basic load-balancing options available to modal-CAM (1) to establish an optimal configuration of the implicitly-solved multiphase chemistry module that maximizes both computational speed and repeatability of Ros-2 and RODAS-3 results versus Ros-3, and (2) to identify potential implementation strategies for future versions of this and similar coupled systems. RODAS-3 was faster than Ros-2 and Ros-3 with good reproduction of Ros-3 results, while Ros-2 was both slower and substantially less reproducible relative to Ros-3 results. Modal-CAM with MECCA chemistry was a factor of 15 slower than modal-CAM using standard chemistry. MECCA chemistry integration times demonstrated a systematic frequency distribution for all three solvers, and revealed that the change in run-time performance was due to a change in the frequency distribution of chemical integration times; the peak frequency was similar for all solvers. This suggests that efficient chemistry-focused load-balancing schemes can be developed that rely on the parameters of this frequency distribution.

A Global, High Resolution, Satellite‐Based Model of Air‐Sea Isoprene Flux

Abstract: A procedure is described where satellite data from different sensors are merged to compute global air-sea isoprene flux estimates. Observational relationships based on cruise data are used to constrain a global satellite based model of ocean to atmosphere isoprene flux. The strong relationship between surface ocean isoprene concentration and chlorophyll concentration is used to estimate the surface ocean concentration of isoprene on a monthly basis at 2° x 2.5° resolution. Monthly mean NASA SeaWiFS chlorophyll estimates are used to drive the isoprene concentration distributions. The global computed range of isoprene in the surface ocean is 1 - 100 pmol l -1 . 4-D assimilated surface meteorological variables from the Data Assimilation Office (DAO) at NASA/GSFC are used to compute the global isoprene transfer velocity field. The range in ocean to atmosphere flux is 0.1-200 ug C m -2 d -1 . The global integrated flux of isoprene from the ocean to the atmosphere is 0.085 Tg C yr -1 with an error estimate of at least 100%. This estimate is a factor of 3 - 10 lower than previous estimates, most likely due to an under representation of the oceanic gyre regions in previous global extrapolations. This procedure will be used in the future when co-located in time and space SeaWiFs data and DAO assimilated meteorological fields are available. Since the atmospheric residence time of isoprene is on the order of hours, the ocean source of isoprene is likely to be critical in determining marine boundary layer O 3 , OH and general oxidizing capacity in remote marine regions.