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Re: RUC analysis change implementation likely tomo
Posted By: Stan Benjamin In Response To: Re: RUC analysis change implementation likely tomo (Jack Glendening)
Date: 30-September-04 1913Z
In Response To: Re: RUC analysis change implementation likely tomo (Jack Glendening)
Jack - I looked at this a little bit today after writing a little code to monitor some of these statistics in an FSL development RUC cycle. There are typically about 7000 surface obs in the RUC domain, including METARs and mesonet obs. One of these, about 3% of these stations typically are more than 4 degK colder (in virtual pot temp) than the 1h forecast, after interpolation to try to match stations and model grid elevations. About 25-30% are typically at least 1 degK colder than the background 1h forecast (this is a 1-day sample!). These differences are not too different for the analysis itself (see next paragraph). For the last couple of days, the use of PBL-depth in the assimilation only affects analyses between 15z and 00z. This is related to seasonal variations, of course, as days (and deeper PBL diurnal periods) become shorter and PBL depths decrease.
These percentages are affected (i.e. increased) by local representativeness issues from siting or elevation-difference adjustments, especially for the mesonet observations. The fact that the analysis fit to these same surface observations is not too different from that for the 1h forecasts tends to confirm this hypothesis. I should write some additional code at some point to look at these same stats w/ METAR observations only, but thought I'd post now with what I had found. Thanks for the good question, as always. Stan
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