Jones, Roger ORCID: 0000-0001-6970-2797 and Harrold, T. I (2003) Generation of local-scale rainfall scenarios using changes in GCM rainfall: a refinement of the perturbation method. In: MODSIM 2003: International Congress on Modelling and Simulation: Proceedings. Post, David A, ed. Modelling and Simulation Society of Australia and New Zealand, Canberra, pp. 11-16.

Abstract

Global Climate Models (GCMs) are the best tools from which future climate scenarios can be constructed. GCMs simulate important large-scale features of the Earth’s climate system. However, it is changes in local-scale climate that will most affect rainfall. A popular approach for producing rainfall scenarios at scales relevant for hydrological impact studies is to calculate the average percentage change in GCM grid square rainfall from current to future conditions, with separate calculations for each month, and then to scale observed records of point daily rainfall by these percentage changes. This is termed the perturbation method. The main advantage of this method is that it is simple and easy to apply. However, the use of monthly GCM outputs ignores possible changes in daily extremes or the frequency of wet days, which are of great interest in hydrological impact studies. A refinement of the perturbation method is presented, which uses a daily pattern of change rather than the average percentage change. These patterns of change are then used to scale ranked historical point daily rainfall. This method is sensitive to the changes in extreme daily rainfalls and changes in the frequency of wet days simulated by the GCM, producing a more realistic sequence of changed daily rainfall, compared to the commonly used approach of simply scaling all the historical rainfall values in each month by the same amount. International Congress on Modelling and Simulation Integrative Modelling of Biophysical, Social, and Economic Systems for Resource Management Solutions Jupiters Hotel and Casino, Townsville, Australia 14-17 July 2003

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