Environmental Engineering Reference
In-Depth Information
5.7 A Multiphase Chemistry Model to Study
Biophysicochemical Processes in Clouds
N. Chaumerliac, L. Deguillaume, and Y. Long
LaMP/CNRS, Université Blaise Pascal, Clermont-Ferrand
1. Introduction
Since several years, significant efforts have been made by the scientific community
to understand and characterize the tropospheric chemistry. The evaluation of
multiphase chemistry versus the overall tropospheric chemistry and its role in the
Earth's radiative budget is challenging because the physical nature and reactivity
of condensed phases are still poorly known.
Modelling studies attempted to understand the overall role of cloud chemistry
in global climate studies, but our knowledge on the details of cloud chemistry is
still incomplete. For this, process models make it possible to simulate various
reaction pathways for given chemical species within clouds, complex interactions
between microphysical, chemical, radiative, and dynamic processes, and the influence
of environmental parameters on multiphase chemistry.
The structure of the numerical models allows sensitivity analyses to be carried
out for example, on dubious parameters. An integrated approach using modelling
tools including laboratory data and field observations could help to improve our
understanding of these complex processes.
2. Model Description
The M2C2 model is composed of two modules which can be coupled together:
(1) a multiphase chemistry model initially developed by Leriche et al. (2000, 2001)
and updated in Leriche et al. (2003) and Deguillaume et al. (2004) and (2) a two-
moment warm microphysical scheme module predicting the number concentration
of cloud droplets and raindrops and the mixing ratio of cloud water and rainwater
categories. The microphysical module also considers the cloud droplets nucleation
process (Leriche et al., 2007). The dynamical framework of the model is an air
parcel with entrainment.
The chemistry included in the chemical module is explicit: the detailed chemistry
of H
x
O
y
, chlorine, carbonates, NO
y
, sulphur, the oxidation of organic volatile
compounds (VOCs) with one carbon atom (Leich et al., 2003), the chemistry of
transition metal ions for iron, manganese and copper (Deguillaume et al., 2004) is
