 |
| Titel |
Sources and seasonality of atmospheric methanol based on tall tower measurements in the US Upper Midwest |
| VerfasserIn |
L. Hu, D. B. Millet, M. J. Mohr, K. C. Wells, T. J. Griffis, D. Helmig |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 21 ; Nr. 11, no. 21 (2011-11-10), S.11145-11156 |
| Datensatznummer |
250010179
|
| Publikation (Nr.) |
 copernicus.org/acp-11-11145-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| We present over one year (January 2010–February 2011) of continuous atmospheric
methanol measurements from the University of Minnesota tall tower Trace Gas
Observatory (KCMP tall tower; 244 m a.g.l.), and interpret the dataset in
terms of constraints on regional methanol sources and seasonality. The
seasonal cycle of methanol concentrations observed at the KCMP tall tower is
generally similar to that simulated by a global 3-D chemical transport model
(GEOS-Chem, driven with MEGANv2.0 biogenic emissions) except the seasonal
peak occurs ~1 month earlier in the observations, apparently
reflecting a model underestimate of emission rates for younger versus older
leaves. Based on a source tracer approach, which we evaluate using GEOS-Chem
and with multiple tracers, we estimate that anthropogenic emissions account
for approximately 40% of ambient methanol abundance during winter and
10% during summer. During daytime in summer, methanol concentrations
increase exponentially with temperature, reflecting the temperature
sensitivity of the biogenic source, and the observed temperature dependence
is statistically consistent with that in the model. Nevertheless, summertime
concentrations are underestimated by on average 35% in the model for this
region. The seasonal importance of methanol as a source of formaldehyde
(HCHO) and carbon monoxide (CO) is highest in spring through early summer,
when biogenic methanol emissions are high but isoprene emissions are still
relatively low. During that time observed methanol concentrations account
for on average 20% of the total CO and HCHO production rates as simulated
by GEOS-Chem, compared to 12% later in the summer and 12% on an annual
average basis. The biased seasonality in the model means that the
photochemical role for methanol early in the growing season is presently
underestimated. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|