Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum
Posted By: Geoff Manikin
Date: 18-December-06 2116Z
Sorry for the late notice, but two small changes were made to the operational RUC on 12 December 2006. The first change was to add some smoothing to the fields brought in from the NAM to create the boundary conditions for the RUC. This was in response to a model failure on 21 November which was traced to sharp vertical gradients associated with an unusual southward push of polar air to the model's southern boundary.
The second change is a modification of the treatment of lakes in northern Minnesota and Manitoba which are not resolved well in the current water temperature data. As discussed in the posting in this forum on 5 September, representative nearby lake points with reliable data are used for these lakes. We ran into problems, however, last month when the lakes used for data were frozen while the "real" lakes were not. The cold model temperatures over the frozen lakes were brought southward to the unfrozen lakes, leading to erroneous cold values. The code has been modified to use the local model temperatures when the lake from which data is being borrowed is frozen.
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