Goal:

Analysis of the diurnal cycle of precipitation - in particular, broken down into intensity, frequency and amounts - as a test bed for a hierarchy of models across all scales with a focus on North America summertime. Radars, gauges, and satellites are used for data sources.  

Use above analysis to address the deficiencies in current models and what needs to be improved to obtain a proper simulation of the dirunal cycle of precipitation in weather and climate models.

We will conduct case studies of the onset, duration, intensity and frequency of precipitation as a function of time of day.

First, diagnostic analyses will be performed on the diurnal cycle of observational fields during summers having a good QPE as well as other databases of observed/analyzed truth, such as periods examined by Carbone et al. or the summer of 1993 floods.

Second, diagnostic analyses of prediction models (e.g., NCEP, ECMWF) and also the CAM run with specialized SSTs and boundary conditions will be conducted to determine errors/ biases in precipitation (i.e., amounts, frequency, intensity) for the same periods as the aforementioned observational analysis. The differences between these predictions and reality will quantify which aspects of the diurnal cycle are responsible for the model errors/bias in precipitation, convective parameterization, surface-process parameterization, etc. (Dai et al. 1999).

Third, regional modeling using lateral boundary conditions and surface boundary conditions on selected cases will be conducted (perhaps in collaboration with USWRP) and hourly statistics compiled.

Finally, we will employ constrained objective analyses of soundings and other data to determine the large-scale moisture and temperature advection --- the evolving "large-scale forcing" for use in the CRMs. Note that the QPE on the continental scale is involved here.

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