We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK


93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Excitation of the primary tropospheric chemical...
View graph of relations

« Back

Excitation of the primary tropospheric chemical mode in a global three-dimensional model

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>27/10/2000
<mark>Journal</mark>Journal of Geophysical Research: Atmospheres
Number of pages14
<mark>Original language</mark>English


Coupling of local chemical processes over the globe by atmospheric transport leads to the existence of chemical modes that are a fundamental characterization of global atmospheric chemistry and provide a true description of the atmospheric response to small changes in trace-gas emissions. Such coupled chemistry-transport modes in global tropospheric chemistry are an inherent feature of three-dimensional chemical transport models (CTMs). In CTMs these modes cannot be solved for explicitly, as they have been for the case of low-order, fully linearized systems, but they are investigated here through a series of perturbation experiments. When using meteorological fields that recycle every year, the long-lived modes are readily seen as seasonal decay patterns that e-fold each year. An important application of chemical modes is the study of how emissions of CO and NO excite perturbations to the CH4-like mode, the longest-lived (primary) mode found in tropospheric chemistry (i,e., with fixed stratospheric composition). Perturbation experiments are conducted with the University of California, Irvine, three-dimensional tropospheric CTM to identify this primary tropospheric mode and to determine its five-dimensional structure. The previous demonstrations of a long-lived chemical mode with 1.5 times the lifetime of CH4 are corroborated. The ability of emissions of CO and NO to excite this mode is then demonstrated, and a quantitative evaluation of the indirect effect of CO emissions on the greenhouse gases CH4 and tropospheric O-3 is made, showing that 100 kg of CO is equivalent to 5-6 kg of CH4 emissions.