130
effort needs to be carried out to understand their differences and their sensitivity to
the many parameters involved in each model, and the PILPS project is an important
step towards this goal. In addition, a critical need is there today to assemble more
observational datasets for model validation, either through field campaigns or through the
use of remotely sensed data. Use of satellite data for model development and validation
is an area in need of creative thinking which will be of increasing relevance as more
comprehensive observing systems are developed.
Finally, the modeling activities reviewed in the last portion of this paper clearly indicate that surface heterogeneities have significant effects, both direct and indirect, on the
surface water and energy budgets and on the exchanges of momentum, energy and water
vapor between land and atmosphere. Many attempts at understanding, quantifying and
including these effects in ESEMs and climate models are currently under way. However,
these attempts are undermined by the lack of adequate observational data, a feature quite
common in the study of surface processes. The description of surface heterogeneity effects
in climate models and the assessment of their climatic significance is an area of research
which is still in it's beginning stages and, as human activities keep modifying the characteristics of the surface on a wide range of spatial scales, it will likely remain of much
interest in the next years within the global change debate.
ACKNOWLEDGEMENTS
I would like to thank Anji Seth for making available some results from her dissertation
work.
REFERENCES
Abbott, M.B., J.C. Bathurst, J.A. Cunge, P.E. O'Connell, and J. Rasmussen, 1986:
An introduction to the European Hydrological System - System Hydrologique Europeen, " SHE" , 2: Structure of a physically-based, distributed modelling system.
Journal of Hydrology, 87, 61-77.
Andre, J.C., J.P. Gouturbe, A. Perrier, 1986: HAPEX-MOBILHY: A hydrologic atmospheric experiment for the study of water budget and evaporation flux at the
climatic scale. Bulletin of the American Meteorological Society, 67, 138-144.
Andre, J.c., J.P. Gouturbe, A. Perrier, R.H. Cuenca, L. Mahrt, J. Noilhan et al.,
1988: Evaporation over land surfaces: First results from the HAPEX-MOBILHY
special observing period. Annales Geophysicae, Series B, , 477-492.
Anthes, R. A., 1984: Enhancement of convective precipitation by mesoscale variations in vegetative covering in semiarid regions,Journal of Climatology and Applied
Meteorology, 23, 541 - 554.
Atkinson, B.w., 1981: Meso-scale atmospheric circulations. Academic Press, New
York,495.
Avissar, R., 1992: Conceptual aspects of a statistical-dynamical approach to represent
landscape subgrid-scale heterogeneities in atmospheric models, Journal of Geophysical Research, 97, 2729 - 2742.
effort needs to be carried out to understand their differences and their sensitivity to
the many parameters involved in each model, and the PILPS project is an important
step towards this goal. In addition, a critical need is there today to assemble more
observational datasets for model validation, either through field campaigns or through the
use of remotely sensed data. Use of satellite data for model development and validation
is an area in need of creative thinking which will be of increasing relevance as more
comprehensive observing systems are developed.
Finally, the modeling activities reviewed in the last portion of this paper clearly indicate that surface heterogeneities have significant effects, both direct and indirect, on the
surface water and energy budgets and on the exchanges of momentum, energy and water
vapor between land and atmosphere. Many attempts at understanding, quantifying and
including these effects in ESEMs and climate models are currently under way. However,
these attempts are undermined by the lack of adequate observational data, a feature quite
common in the study of surface processes. The description of surface heterogeneity effects
in climate models and the assessment of their climatic significance is an area of research
which is still in it's beginning stages and, as human activities keep modifying the characteristics of the surface on a wide range of spatial scales, it will likely remain of much
interest in the next years within the global change debate.
ACKNOWLEDGEMENTS
I would like to thank Anji Seth for making available some results from her dissertation
work.
REFERENCES
Abbott, M.B., J.C. Bathurst, J.A. Cunge, P.E. O'Connell, and J. Rasmussen, 1986:
An introduction to the European Hydrological System - System Hydrologique Europeen, " SHE" , 2: Structure of a physically-based, distributed modelling system.
Journal of Hydrology, 87, 61-77.
Andre, J.C., J.P. Gouturbe, A. Perrier, 1986: HAPEX-MOBILHY: A hydrologic atmospheric experiment for the study of water budget and evaporation flux at the
climatic scale. Bulletin of the American Meteorological Society, 67, 138-144.
Andre, J.c., J.P. Gouturbe, A. Perrier, R.H. Cuenca, L. Mahrt, J. Noilhan et al.,
1988: Evaporation over land surfaces: First results from the HAPEX-MOBILHY
special observing period. Annales Geophysicae, Series B, , 477-492.
Anthes, R. A., 1984: Enhancement of convective precipitation by mesoscale variations in vegetative covering in semiarid regions,Journal of Climatology and Applied
Meteorology, 23, 541 - 554.
Atkinson, B.w., 1981: Meso-scale atmospheric circulations. Academic Press, New
York,495.
Avissar, R., 1992: Conceptual aspects of a statistical-dynamical approach to represent
landscape subgrid-scale heterogeneities in atmospheric models, Journal of Geophysical Research, 97, 2729 - 2742.