Unexpected increase in precipitation intensity with temperature - A result of mixing of precipitation types?

Using synoptic weather types and comparing high-resolution precipitation and temperature station data, a separation of large-scale and convective precipitation events is performed. We present percentiles of both types and their superposition for varying precipitation accumulation timescales. In some temperature ranges, large-scale, convective and total precipitation percentiles follow increases with temperature at rates higher than that of the saturation humidity increase of the atmosphere of roughly 7% per degree Kelvin - as given by the Clausius-Clapeyron (CC) relation. However, the increase in total precipitation is found to be due to the transition between the corresponding percentiles of the large-scale and convective types, rather than their individual sections of steep increase. Furthermore, convective precipitation displays a leveling-off towards higher temperatures. This poses further challenges to reconcile arguments brought forward elsewhere - namely those suggesting convective precipitation as the driver of the super-CC increase - with the present observational data. (C) 2011 Elsevier B.V. All rights reserved.