Thursday, May 05, 2011


[Warning:  I'm getting flaky here.  I just couldn't keep up, but you can get a sense of the talk.  People are leaving now for concurrent session.  I have to divide into three.]

Quantitative Precipitation Forecasting. The State Climatologist, Peter Olsson, is the lunch speaker.

1. Water Vapor
2. Cooling of the Atmosphere

Lifting agents - Large - warm front; Small - mountains

Small end of the scale

Cloud microphysics - cloud droplets to raindrops (2000 microns) - We don't really know what happens in the cloud. Can't do in a cloud chamber. Numerical models - scale from micron to thousands of kilometers.

Disclaimer #1: Gridded finite models and Spectral models
#2: differences between models used to be huge. Not so much any more.

Model Grids - [I'm not quite close enough to read the slides from my table near the electric outlet]

Global Climate models
Regional climate model
High resolution forecast model

Sorry, this is way over my head.

Now he's talking about Orographic Precipitation - Compared to Girdwood, we have a 5:1 difference. Which side of the mountain you're on.

From Wikipedia:

Orographic precipitation, also known as relief precipitation, is precipitation generated by a forced upward movement of air upon encountering a physiographic upland (see anabatic wind). This lifting can be caused by two mechanisms:

1. The upward deflection of large scale horizontal flow by the orography.
2. The anabatic or upward vertical propagation of moist air up an orographic slope caused by daytime heating of the mountain barrier surface.
He went through various technical problems in predicting. 

Mountains play significant role in precipitation and we have lots of mountains.  We tend to under predict in the winter and overpredict in summer.  QPF is not a cookbook for predictions near the mountains. 

How does this affect climate models?  A lot more guesswork going into what they have to do. 

I simply can't capture all he's saying.  You probably need to contact him if you want the details. 

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