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Message: too much precip, too small diurnal cycle

Posted by Stan Benjamin on 18 Sep 98, 17:03 MT

Some ugly behavior has become apparent in the RUC2 and the 40km MAPS.
It appears that over the past month or so, the precipitation has become
excessive over much of the eastern half of the country, and even
to some extent in the West. We also have noted too little warming in
the daytime and too little cooling at night. This diurnal cycle problem
existed before, but seems to be worse recently.

This note is to let you know we've noticed and are working on it. Right now
we believe that the precip and sfc temp behavior are linked. The soil
moisture has become too high in the areas of excessive precip, and this
has damped the diurnal cycle, especially the daytime heating. We
suspect a feedback between the convective precipitation and the surface
fluxes, and have made a change in the 40km MAPS that alleviates this
problem some. If this fix or a variant appears to be effective, we will
work to get it into the RUC2 as soon as possible.

We welcome comments on any particular behavior you may have noted that
may relate to this problem.

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