Non-physical Kain-Fritsch Precipitation Bands

The Problem

banded imagebanded imagebanded image
As seen in the lower left quadrant of the lefthand 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.

As seen in the image above right, standing waves of precipitation develop in this case from 2012101912. For more on this case, see below.

Case Study Plots
ProductForecast HourCase

The Cases

NameAbbreviationWRF VersionWRF cu_physicsDescription
1. Kain-Fritschkf3.1.11Real-time, version 3.1.1 with standard, new Kain-Fritsch Scheme
2. Old Kain-Fritschkf993.1.199Older Kain-Fritsch scheme does not have the problem.
3. Grellgrell3.1.13Grell-Devenyi ensemble scheme does not have the problem.
4. Grell5grell53.1.15New Grell 3d ensemble cumulus scheme does not have the problem.
5. Kain-Fritsch in WRF3.3kfv333.31Kain-Fritsch scheme as found in WRF version 3.3 still has the problem.
6. Old Kain-Fritsch WRFV3.3kf99v333.399Old Kain-Fritsch in WRFV3.3 does not have the problem.
7. Kain-Fritsch No FDDA Ptop50kfptop50nofdda3.1.11Kain-Fritsch without FDDA analysis nudging and with the model top at 50 mb instead of 100 mb.
8. WRF v3.4.1 Kain-Fritsch Ptop50wrfv341kf3.4.11Kain-Fritsch with the model top at 50 mb instead of 100 mb.
9. WRF v3.4.1 Grell Ptop50wrfv341grell3.4.11Grell with the model top at 50 mb instead of 100 mb.

Table 2. Additional 12-km and 4-km Cases
InitializationDomainProductHourCases (control click to select multiple)
Choose a date:
 Choose a domain
36-km
12-km
4-km
 All products
------ Moisture ---------
Low clouds sfc to 3000 feet
Low clouds 3 - 10Kft
Middle clouds 10-20Kft
High clouds about 20Kft
700 mb Vertical Velocity
OLR
Integrated Cloud
1-hour Precip
3-hour Precip
24-hour Precip
Western Washington 24-hour Precip
Western Washington 3-hour Precip
Western Washington 1-hour Precip
500mb Vorticity
--- Vertical Cross Sections (Nov 30 case only) --
N-S at 126W, total cloud mr
N-S at 126W, total precip mr
N-S at 126W, rain water mr
N-S at 126W, vertical velocity
N-S at 127W, total cloud mr
N-S at 127W, total precip mr
N-S at 127W, rain water mr
N-S at 127W, vertical velocity
 Choose an hour  Hour 0
Hour 6
Hour 12
Hour 18
Hour 21
Hour 24
Hour 30
Hour 33
Hour 36
Hour 48
All hours