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Nonlinearity and Climate Group

Single-column surface-atmosphere climate modelling

The interconnections between the land including water surfaces and the Earth’s climate system involve numerous non-linear processes. Tridimensional weather and climate models use quantitative methods to simulate the interactions of the important drivers, including atmosphere, oceans and lakes, land surface, biosphere and ice. They require a huge amount of computing resources, however. The use of a single-column model (SCM) provides an alternative, practical and economical framework for assessing nonlinearities of the surface types to current and perturbed climatic conditions. A coupled atmosphere-surface SCM, nicknamed FIZC, has been developed to investigate numerically the nonlinear interactions occurring in the lower atmosphere. It includes the contributions to the evolution of large-scale circulation dynamics in combination with diabatic contributions as parameterized in tridimensional weather and climate models, thus allowing for a realistic time evolution of the prognostic atmospheric temperature, moisture and winds. Recently, FIZC has been used to explore some of the non-linear interactions in the vertical dimension between the lower atmosphere and the deep-Lake Geneva in Switzerland.

coupling process taking place at the air-water interface

Schematic diagram showing the coupling process taking place at the air-water interface in the lowest atmospheric model layer and the upper lake model layer; R↓s,↑sfc represent the incoming and reflected solar radiation fluxes, R↓L,↑sfc the atmospheric and the surface longwave radiation fluxes, QH and QE, the sensible and latent heat fluxes, QN,sfc the surface energy budget, [u, v]anem  the anemometer wind speed components, tsfc the surface wind stress, Tsfc the surface water temperature, αw the water surface albedo, CD, the drag coefficient, and k-ε represents the lake model used in this study (Goyette and Perroud, 2012).

REFERENCES

Goyette, S., 2016 : Numerical investigation with a coupled single-column lake-atmosphere model. Using the Alpert-Stein Factor Separation Methodology to assess the sensitivity of surface interactions. Climate Dynamics, 48, 2359. DOI 10.1007/s00382-016-3209-1

Perroud, M., and S. Goyette, 2012 : Interfacing a one-dimensional lake model with a single-column atmospheric model II. Thermal response of the deep Swiss Lake Geneva under a 2 x CO2 global climate change. Water Resour. Res. 48, W06522, doi:10.1029/2011WR011222.

Goyette, S. and M. Perroud, 2012 : Interfacing a one-dimensional lake model with a single-column atmospheric model: Application to the deep Lake Geneva, Switzerland. Water Resour. Res., 48, W04507, doi:10.1029/2011WR011223.