Abstract

Today I finished my dissertation and gave the first copy to one of my committee members. I plan to give copies to the rest of the committee tomorrow. (I couldn't today because it takes a long time to print 122 pages on an ink jet)

The abstract for my dissertation/seminar is now public, so I'll post it here if anyone is interested in knowing more about what I've been working on for the past 3 years.

By the way, all of you are invited to my seminar on Tuesday March 28 at 3:30 PM in Sarkey's Energy Center (SEC) A235. I'll likely be challenging some long-held beliefs of people in the room. It should be interesting, especially if there are a lot of skeptics.

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The Uncoupled Surface Layer

One of the greatest challenges faced by weather forecasters is the large spatial variability of temperature that occurs at small scales, particularly on clear nights with light wind. The physical processes that create this variability were analyzed using 3 years of meteorological observations from the Crosstimber Micronet, an automated microscale surface observation network in central Oklahoma.

The observations revealed extreme microscale temperature gradients (i.e., > 10°C across less than 200 m of land) across the Micronet. These gradients were shown to be created by the unique surface energy balance within a turbulence-free layer of air that sometimes develops near the ground. This layer is called the uncoupled surface layer (USL).

Based on the surface energy budget and parameterizations derived from observations of the USL at the Micronet, the Uncoupled Surface Layer forecast model (USL model) was developed to predict near-surface temperatures on clear nights. The USL model represents a new approach to temperature forecasting that, heretofore, has not been documented in the scientific literature.

Nine diverse locations across central Oklahoma, central California, and southern California were selected for verification of forecasts by the USL model on clear nights from June-December 2005. These forecasts were compared with concurrent forecasts by operational Model Output Statistics (MOS), a well-respected forecasting technique used operationally for decades.

Forecasts by the USL model were 0.5-4.1°C (21-72%) more accurate than those by MOS. The largest improvements over MOS were observed at the Crosstimber Micronet (72%) and Cuyama, California (67%). Both are located in sheltered valleys that are considered very favorable for development of the USL. The USL model also substantially outperformed MOS at locations that are considered less favorable for USL development (e.g., urban areas along the Pacific Coast).

The accuracy of the USL model confirms that the uncoupled surface layer is an important feature of the near-surface nocturnal boundary layer at a wide variety of locations. The results also suggest that the USL model is likely to have a significant impact on the future of nighttime temperature forecasting.

posted by Matt @ 5:52 AM