 |
| Titel |
CESM/CAM5 improvement and application: comparison and evaluation of updated CB05_GE and MOZART-4 gas-phase mechanisms and associated impacts on global air quality and climate |
| VerfasserIn |
J. He, Y. Zhang, S. Tilmes, L. Emmons, J.-F. Lamarque, T. Glotfelty, A. Hodzic, F. Vitt |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1991-959X
|
| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 12 ; Nr. 8, no. 12 (2015-12-16), S.3999-4025 |
| Datensatznummer |
250116708
|
| Publikation (Nr.) |
 copernicus.org/gmd-8-3999-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Atmospheric chemistry plays a key role in determining the amounts and
distributions of oxidants and gaseous precursors that control the formation
of secondary gaseous and aerosol pollutants; all of those species can
interact with the climate system. To understand the impacts of different
gas-phase mechanisms on global air quality and climate predictions, in this
work, a comprehensive comparative evaluation is performed using the Community
Atmosphere Model (CAM) Version 5 with comprehensive tropospheric and
stratospheric chemistry (CAM5-chem) within the Community Earth System Model
(CESM) with the two most commonly used gas-phase chemical mechanisms: the
2005 Carbon Bond mechanism with Global Extension (CB05_GE) and the Model of
OZone and Related chemical Tracers version 4 (MOZART-4) mechanism with
additional updates (MOZART-4x). MOZART-4x and CB05_GE use different
approaches to represent volatile organic compounds (VOCs) and different
surrogates for secondary organic aerosol (SOA) precursors. MOZART-4x includes
a more detailed representation of isoprene chemistry compared to CB05_GE.
CB05_GE includes additional oxidation of SO2 by O3 over the
surface of dust particles, which is not included in MOZART-4x. The results
show that the two CAM5-chem simulations with CB05_GE and MOZART-4x predict
similar chemical profiles for major gases (e.g., O3, CO, and NOx)
compared to the aircraft measurements, with generally better agreement for
NOy profiles by CB05_GE than MOZART-4x. The concentrations of SOA at
four sites in the continental US (CONUS) and organic carbon (OC) over the
IMPROVE sites are well predicted by MOZART-4x (with normalized mean biases
(NMBs) of −1.9 and 2.1 %, respectively) but moderately underpredicted
by CB05_GE (with NMBs of −23.1 and −20.7 %, respectively). This is
mainly due to the higher biogenic emissions and OH levels simulated with
MOZART-4x than with CB05_GE. The concentrations of OC over Europe are
largely underpredicted by both MOZART-4x and CB05_GE, with NMBs of −73.0
and −75.1 %, respectively, indicating the uncertainties in the
emissions of precursors and primary OC and relevant model treatments such as
the oxidations of VOCs and SOA formation. Uncertainties in the emissions and
convection scheme can contribute to the large bias in the model predictions
(e.g., SO2, CO, black carbon, and aerosol optical depth). The two
simulations also have similar cloud/radiative predictions, with a slightly
better performance of domain average cloud condensation nuclei (CCN) at
supersaturation of 0.5 % by CB05_GE, but slightly better agreement with
observed CCN (at supersaturation of 0.2 %) profile over Beijing by
MOZART-4x. The two gas-phase mechanisms result in a global average difference
of 0.5 W m−2 in simulated shortwave cloud radiative forcing, with
significant differences (e.g., up to 13.6 W m−2) over subtropical
regions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|