MACv2-SP: a parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6
A simple plume implementation of the second version (v2) of the Max Planck Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a prescription of anthropogenic aerosol optical properties and an associated Twomey effect. It was created to provide a harmonized description of post-1...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-02-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/10/433/2017/gmd-10-433-2017.pdf |
| Summary: | A simple plume implementation of the second version (v2) of the Max Planck
Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a
prescription of anthropogenic aerosol optical properties and an associated
Twomey effect. It was created to provide a harmonized description of
post-1850 anthropogenic aerosol radiative forcing for climate modeling
studies. MACv2-SP has been designed to be easy to implement, change and use,
and thereby enable studies exploring the climatic effects of different
patterns of aerosol radiative forcing, including a Twomey effect. MACv2-SP is
formulated in terms of nine spatial plumes associated with different major
anthropogenic source regions. The shape of the plumes is fit to the Max
Planck Institute Aerosol Climatology, version 2, whose present-day (2005)
distribution is anchored by surface-based observations. Two types of plumes
are considered: one predominantly associated with biomass burning, the other
with industrial emissions. These differ in the prescription of their annual
cycle and in their optical properties, thereby implicitly accounting for
different contributions of absorbing aerosol to the different plumes. A
Twomey effect for each plume is prescribed as a change in the host model's
background cloud-droplet population density using relationships derived from
satellite data. Year-to-year variations in the amplitude of the plumes over
the historical period (1850–2016) are derived by scaling the plumes with
associated national emission sources of SO<sub>2</sub> and NH<sub>3</sub>. Experiments using
MACv2-SP are performed with the Max Planck Institute Earth System Model. The
globally and annually averaged instantaneous and effective aerosol radiative
forcings are estimated to be −0.6 and −0.5 W m<sup>−2</sup>, respectively.
Forcing from aerosol–cloud interactions (the Twomey effect) offsets the
reduction of clear-sky forcing by clouds, so that the net effect of clouds on
the aerosol forcing is small; hence, the clear-sky forcing, which is more
readily measurable, provides a good estimate of the total aerosol forcing. |
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| ISSN: | 1991-959X 1991-9603 |