A global evaluation of fronts and precipitation in the ACCESS model

Abstract

How global precipitation will change in the future is of great socio-economic importance. It is therefore vital that climate models are able to adequately simulate the characteristics of precipitation and the individual precipitation events. Fronts play an important role in providing precipitation and they can be associated with heavy rain and flooding. In this paper the ACCESS1.3 atmosphere model is evaluated in terms of frontal and non-frontal precipitation. An objective front identification method is applied to data from reanalysis and the model. The fronts are then linked to daily precipitation from observational estimates and the model. The proportion of precipitation associated with fronts and the average intensity of precipitation associated with fronts are then calculated and compared. The frequency of fronts and the proportion of precipitation associated with fronts are well captured by the model. The intensity of precipitation when a front is present is underestimated by the model in most regions, consistent with many previous studies. Decomposing the total precipitation error into components associated with the frequency and intensity of both frontal and non-frontal precipitation shows that the non-frontal precipitation errors contribute the most to the total error, and that there are compensating errors in the model. This regime- and process-based method of model evaluation provides a useful tool to gain deeper understanding into the sources of precipitation errors in climate models.