Dynamical Downscaling (PRECIS)

Method Description

A regional climate model (RCM) is a high resolution climate model that covers a limited area of the globe, typically 5,000 km x 5,000 km, with a typical horizontal resolution of 50 km. RCMs are based on physical laws represented by mathematical equations that are solved using a three-dimensional grid. Hence RCMs are comprehensive physical models, usually including the atmosphere and land surface components of the climate system, and containing representations of the important processes within the climate system (e.g., cloud, radiation, rainfall, soil hydrology). Many of these physical processes take place on much smaller spatial scales than the model grid and cannot be modelled and resolved explicitly. Their effects are taken into account using parametrizations, by which the process is represented by relationships between the area or time averaged effect of such sub-grid scale processes and the large scale flow.

The PRECIS climate model (stands for "Providing REgional Climates for Impacts Studies") is an atmospheric and land surface model of limited area and high resolution which is locatable over any part of the globe. Dynamical flow, the atmospheric sulphur cycle, clouds and precipitation, radiative processes, the land surface and the deep soil are all described. Boundary conditions are required at the limits of the model's domain to provide the meteorological forcing for the RCM. Information about all the climate elements as they evolve through being modified by the processes 22 Generating high resolution climate change scenarios using PRECIS represented in the model is produced. For a detailed description of the model, please see the PRECIS Handbook, Jones et al (2004).

At the moment, we are making a dynamic dowscaling for South American Andes . The region is contained in a grid of 150 x 150 at resolution 50 km (Figure 1). Are in process runs as follows:

GCM Scenario Period
HadCM3Q0 SRES A1B 1950 - 2100
HadCM3Q3 SRES A1B 1950 - 2100
HadCM3Q16 SRES A1B 1950 - 2100
ECHAM4 SRES A2 1989 - 2100
ECHAM4 SRES B2 2069 - 2100
ECHAM5 SRES A1B 1950 - 2100
HadAM3P Baseline 1960 - 1990
HadAM3P SRES A2 2070 - 2100
HadAM3P SRES B2 2070 - 2100
ERA40 Reanalisys 1957 - 2000
NCEP:R2 Reanalisys 1979 - 2005
ERA-Interim Reanalisys 1988 - 1997
ERA15 Reanalisys 1979 - 1993

Figure 1. Procesing Zone, Latin American Andes.