Sensitivities in global scale modeling of isoprene

[摘要] A sensitivity study of the treatment of isoprene and related parameters in 3Datmospheric models was conducted using the global model of tropospheric chemistryMATCH-MPIC. A total of twelve sensitivity scenarios which can be grouped into four thematic categories wereperformed. These four categories consist of simulations with different chemicalmechanisms, different assumptions concerning the deposition characteristics ofintermediate products, assumptions concerning the nitrates from the oxidationof isoprene and variations of the source strengths. The largest differences in ozone compared to the referencesimulation occured when a different isoprene oxidation scheme was used (up to30-60% or about 10 nmol/mol). The largest differences in the abundance of peroxyacetylnitrate (PAN) were found when the isoprene emission strength wasreduced by 50% and in tests with increased or decreased efficiency of the deposition of intermediates. The deposition assumptions were also found tohave a significant effect on the upper tropospheric HO_x production.Different implicit assumptions about the loss of intermediate products were identified as a major reason for the deviations among the testedisoprene oxidation schemes. The total tropospheric burden of O₃calculated in the sensitivity runs is increased compared to the background methane chemistry by26±9Tg( O₃) from 273 to an average from the sensitivity runs of299 Tg(O₃).% revised Thus, there is a spread of ± 35% of the overall effect of isoprene in the model among the testedscenarios. This range of uncertainty and the much larger local deviations found in thetest runs suggest that the treatment of isoprene in global models can only beseen as a first order estimate at present, and points towards specific processes in need of focused future work.

[学科分类] 大气科学