 |
| Titel |
Integration of prognostic aerosol–cloud interactions in a chemistry transport model coupled offline to a regional climate model |
| VerfasserIn |
M. A. Thomas, M. Kahnert, C. Andersson, H. Kokkola, U. Hansson, C. Jones, J. Langner, A. Devasthale |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1991-959X
|
| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 6 ; Nr. 8, no. 6 (2015-06-30), S.1885-1898 |
| Datensatznummer |
250116416
|
| Publikation (Nr.) |
 copernicus.org/gmd-8-1885-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
To reduce uncertainties and hence to obtain a better estimate of aerosol
(direct and indirect) radiative forcing, next generation climate models aim
for a tighter coupling between chemistry transport models and regional
climate models and a better representation of aerosol–cloud interactions. In
this study, this coupling is done by first forcing the Rossby Center regional
climate model (RCA4) with ERA-Interim lateral boundaries and sea surface
temperature (SST) using the standard cloud droplet number concentration
(CDNC) formulation (hereafter, referred to as the "stand-alone RCA4
version" or "CTRL" simulation). In the stand-alone RCA4 version, CDNCs are
constants distinguishing only between land and ocean surface. The meteorology
from this simulation is then used to drive the chemistry transport model,
Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled
online with the aerosol dynamics model, Sectional Aerosol module for Large
Scale Applications (SALSA). CDNC fields obtained from MATCH–SALSA are then
fed back into a new RCA4 simulation. In this new simulation (referred to as
"MOD" simulation), all parameters remain the same as in the first run
except for the CDNCs provided by MATCH–SALSA. Simulations are carried out
with this model setup for the period 2005–2012 over Europe, and the
differences in cloud microphysical properties and radiative fluxes as a
result of local CDNC changes and possible model responses are analysed.
Our study shows substantial improvements in cloud microphysical properties
with the input of the MATCH–SALSA derived 3-D CDNCs compared to the
stand-alone RCA4 version. This model setup improves the spatial, seasonal and
vertical distribution of CDNCs with a higher concentration observed over
central Europe during boreal summer (JJA) and over eastern Europe and Russia
during winter (DJF). Realistic cloud droplet radii (CD radii) values have
been simulated with the maxima reaching 13 μm, whereas in the
stand-alone version the values reached only 5 μm. A substantial
improvement in the distribution of the cloud liquid-water paths (CLWP) was
observed when compared to the satellite retrievals from the Moderate
Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months.
The median and standard deviation values from the "MOD" simulation are
closer to observations than those obtained using the stand-alone RCA4
version. These changes resulted in a significant decrease in the total annual
mean net fluxes at the top of the atmosphere (TOA) by −5 W m−2 over
the domain selected in the study. The TOA net fluxes from the "MOD"
simulation show a better agreement with the retrievals from the Clouds and
the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect
effects are estimated in the "MOD" simulation in comparison to the
pre-industrial aerosol emissions (1900). Our simulations estimated the domain
averaged annual mean total radiative forcing of −0.64 W m−2 with a
larger contribution from the first indirect aerosol effect
(−0.57 W m−2) than from the second indirect aerosol effect
(−0.14 W m−2). |
| |
|
| Teil von |
|
|
|
|
|
|
|
|