Modeling surface processes in climate system models
Filippo Giorgi
National Center for Atmospheric Research
P.O. Box 3000
Boulder, CO, 80307
U.S.A
1. Introduction
In the last decades it has become increasingly evident that, in order to understand the
behavior of the climate system and its response to human activities, a multi-disciplinary
effort is needed to model the interactions between the atmosphere, the hydrosphere, the
biosphere, the eryosphere, and the chemosphere (Trenberth 1992). Interactions between
these components of the climate system have been studied for many years. Only recently,
however, mathematical models (hereafter referred to as Climate System Models, or CSMs)
are being sought to describe the system as a whole, so that possible feedback mechanisms
can be identified and quantified.
Central to climate system modeling are the exchange processes which occur at the
Earth's surface. These exchanges play critical roles in the interactions between the atmosphere, the biosphere and the hydrosphere, and in determining sources and distribution of
important chemical constituents. Traditionally, exchange processes at the Earth's surface
have been modeled in schemes (hereafter referred to as Earth Surface Exchange Models,
or ESEMs) designed to describe the land surface momentum, water and energy budgets
and the surface-atmosphere exchanges of momentum, energy and moisture. This paper
presents an introductory overview of land surface processes and how these are modeled in
ESEMs. In section 2 some basic physical and mathematical concepts concerning surface
process modeling are defined and ESEMs are placed within the context of coupled climate system modeling. A review of available approaches to surface modeling is given in
section 3, while section 4 is devoted to one of the outstanding issues in modeling surface
processes, i.e. the description of surface heterogeneity effects in ESEMs.
A few preliminary considerations on the character of this paper are useful. First,
the main focus here is on land surface models, the extension to exchanges over water
and ice surfaces being rather immediate. Also, although ESEMs are here viewed as
part of CSMs, the discussion is mostly concerned with surface-atmosphere interactions,
due to the author's background as an atmospheric modeler. Some considerations on
ESEM coupling with other climate system components (biosphere and hydrology) are
NATO ASI Series, Vol. I 48
The Mathematics of Models for Climatology
and Environment
Edited by Jesus IIdefonso Diaz
© Springer-Verlag Berlin Heidelberg 1997
Filippo Giorgi
National Center for Atmospheric Research
P.O. Box 3000
Boulder, CO, 80307
U.S.A
1. Introduction
In the last decades it has become increasingly evident that, in order to understand the
behavior of the climate system and its response to human activities, a multi-disciplinary
effort is needed to model the interactions between the atmosphere, the hydrosphere, the
biosphere, the eryosphere, and the chemosphere (Trenberth 1992). Interactions between
these components of the climate system have been studied for many years. Only recently,
however, mathematical models (hereafter referred to as Climate System Models, or CSMs)
are being sought to describe the system as a whole, so that possible feedback mechanisms
can be identified and quantified.
Central to climate system modeling are the exchange processes which occur at the
Earth's surface. These exchanges play critical roles in the interactions between the atmosphere, the biosphere and the hydrosphere, and in determining sources and distribution of
important chemical constituents. Traditionally, exchange processes at the Earth's surface
have been modeled in schemes (hereafter referred to as Earth Surface Exchange Models,
or ESEMs) designed to describe the land surface momentum, water and energy budgets
and the surface-atmosphere exchanges of momentum, energy and moisture. This paper
presents an introductory overview of land surface processes and how these are modeled in
ESEMs. In section 2 some basic physical and mathematical concepts concerning surface
process modeling are defined and ESEMs are placed within the context of coupled climate system modeling. A review of available approaches to surface modeling is given in
section 3, while section 4 is devoted to one of the outstanding issues in modeling surface
processes, i.e. the description of surface heterogeneity effects in ESEMs.
A few preliminary considerations on the character of this paper are useful. First,
the main focus here is on land surface models, the extension to exchanges over water
and ice surfaces being rather immediate. Also, although ESEMs are here viewed as
part of CSMs, the discussion is mostly concerned with surface-atmosphere interactions,
due to the author's background as an atmospheric modeler. Some considerations on
ESEM coupling with other climate system components (biosphere and hydrology) are
NATO ASI Series, Vol. I 48
The Mathematics of Models for Climatology
and Environment
Edited by Jesus IIdefonso Diaz
© Springer-Verlag Berlin Heidelberg 1997