Non-physical Kain-Fritsch Precipitation Bands

The Problem

As seen in the lower left quadrant of the image above, the accumulated non-convective precipitation at hour 60 in the forecast from 0Z July 19, 2011 has a non-physical linear appearance in the model's u direction. In this case, the winds are blowing west to east in this southern portion of the East Pacific High. The case studies described below indicate that this problem is due to the new Kain-Fritsch cumulus scheme as found in WRF versions 3.1.1 and 3.3.

Case Study Plots

Product Forecast Hour Case

The Cases

Name	Abbreviation	WRF Version	WRF cu_physics	Description
1. Kain-Fritsch	kf	3.1.1	1	Real-time, version 3.1.1 with standard, new Kain-Fritsch Scheme
2. Old Kain-Fritsch	kf99	3.1.1	99	Older Kain-Fritsch scheme does not have the problem.
3. Grell	grell	3.1.1	3	Grell-Devenyi ensemble scheme does not have the problem.
4. Grell5	grell5	3.1.1	5	New Grell 3d ensemble cumulus scheme does not have the problem.
5. Kain-Fritsch in WRF3.3	kfv33	3.3	1	Kain-Fritsch scheme as found in WRF version 3.3 still has the problem.
6. Old Kain-Fritsch WRFV3.3	kf99v33	3.3	99	Old Kain-Fritsch in WRFV3.3 does not have the problem.
7. Kain-Fritsch No FDDA Ptop50	kfptop50nofdda	3.1.1	1	Kain-Fritsch without FDDA analysis nudging and with the model top at 50 mb instead of 100 mb.