Single-source urban evaporation-interception scheme (SUES-2): recent developments

Understanding urban energy and water balances is very important because of their impacts on urban climate, pollutant dispersion and urban water management. These balances and their different component are not however routinely measured and therefore theoretical approaches are required. SUES-2 is able to simulate the urban energy and water balances using only commonly measured meteorological variables and information about the land cover. The model is based on the single-source urban evaporation-interception scheme (SUES) (Grimmond and Oke 1991). SUES utilizes an evaporation-interception approach similar to that used in forests to model evaporation from urban surfaces. In the model the urban surface is divided into six types: paved, build, coniferous, deciduous, irrigated grass and non-irrigated grass. Evaporation is calculated from the Penman-Monteith equation. The model allows for a continuous treatment of surface resistance for the transition between wet and dry surfaces. The surface state for each time step is calculated from the running water balance of the canopy. The storage heat flux is calculated with the objective hysteresis model (OHM) (Grimmond et al. 1991, Grimmond and Oke 1999, 2002), which captures the magnitude and diurnal hysteresis of the storage heat flux.

Recent developments in the model include the incorporation of the NARP radiation scheme (Offerle et al. 2003: Loridan et al. 2010) so net all wave radiation is not required as an input; the use of LUMPS (Grimmond and Oke 2002) to do initial calculations of turbulent heat fluxes so that stability calculations are improved; the calculation of soil moisture content so that this is no long required as an input; movement of water between the canopy and soil storages; a simple anthropogenic heat flux model (Loridan et al. 2010); and a simple urban water use model. In addition to accounting more completely for energy and water exchange processes in urban areas, SUES-2 requires less observed variables as inputs to allow the model to run, although if these data are available it can also utilize them.

In this paper, SUES-2 is presented. The model is evaluated using observations collected in Vancouver, BC, Canada, between 22 February and 28 June 1987 and elsewhere. The model is evaluated based on latent heat flux, soil moisture and surface water state observations.

References

Grimmond C.S.B. and Oke T.R. (2002). Turbulent Heat Fluxes in Urban Areas: Observations and a Local-Scale Urban Meteorological Parameterization Scheme (LUMPS). J. Appl. Meteorol. 41, 792-810. Grimmond C.S.B and Oke T.R. (1999). Heat storage in urban areas: observations and evaluation of a simple model. J. Appl. Meteorol., 38, 922-940. Grimmond C.S.B. and Oke T. R. (1991). An Evaporation-Interception Model for Urban Areas. Water Resour. Res. 27, 1739-1755. Grimmond C.S.B., Cleugh H. A. and Oke T.R. (1991). An objective urban heat storage model and its comparison with other schemes. Atmos. Env. 25B, 311-174. Loridan T., Grimmond C.S.B., Offerle B.D., Young D.T., Smith T. and Järvi L. (2010). LUMPS- NARP an urban land surface scheme: evaluation and development of a new longwave parameterization. Submitted to J. Appl. Meteorol. Clim. Offerle B., Grimmond C.S.B. and Oke T.R. (2003). Parameterization of Net All-Wave Radiation for Urban Areas. J. Appl. Meteorol. 42, 1157-1173.