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Global Climate Model Simulations of Southern South America

Blazquez, J. and Nuñez, M.N. 2013. Performance of a high resolution global model over southern South America. International Journal of Climatology 33: 904-919.
Writing as background for their work, Blazquez and Nuñez (2013) state that "nowadays climate models are the main tool to analyze the behavior of meteorological events and to study their development and evolution," while noting that "in recent years they have been used to evaluate the impact of increased anthropogenic greenhouse gas emissions to the atmosphere." And in regard to this particular function, they add that "the first step to understand climate changes that are likely to occur in the future is the assessment of the present climate," which "allows determining the model deficiencies." Thus, Blazquez and Nuñez say their paper "evaluates a present climate simulation over southern South America performed with the Meteorological Research Institute/Japanese Meteorological Agency (MRI/JMA) high resolution global model."

Comparing their simulated wind results with data from the European Centre Medium Range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA 40), and their temperature and precipitation simulations with data from various meteorological stations, the two Argentinian researchers report discovering the following model deficiencies: (1) speeds of the low level jet and the westerlies "are generally underestimated," (2) at upper levels "the westerlies are overestimated over central Argentina," (3) during December-February, March-May and September-November, "the MRI/JMA global model underestimates the temperature over east of Argentina, west of Uruguay, south of Chile and over tropical latitudes,"(4) contemporaneously, "overestimates are observed over central Argentina," while (5) "in June-August the model underestimates the temperature over most of Argentina, south of Chile and to the north of 20°S," (6) "the model overestimates temperature interannual variability in all regions and all seasons, except in JJA," (7) in all seasons the model yields "an underestimation of the precipitation in the southeast of Brazil and south of Peru and an overestimation in Bolivia, Uruguay, north and central Chile and north of Peru," while (8) "during the dry season (JJA) the model greatly overestimates the precipitation over northeastern and central Argentina, (9) "in regions located over mountainous areas the model presents a poor reproduction of the annual cycle," and (10) "observed precipitation trends are generally positive whereas simulated ones are negative."

In light of these many problems with the MRI/JMA global climate model, it is strange that Blazquez and Nuñez would conclude that it is "a good tool to represent the present climate in southern South America and might also be used to simulate future climate changes." What do you think?

Archived 13 August 2013