Extended Abstract (760K)J3.5
Educational mismatches between traditional dynamic meteorology lessons and applied forecaster training with high-resolution gridded diagnostics
Paul Nutter, Univ. of Northern Colorado, Greeley, CO
Meteorology students have traditionally been taught that the Rossby number scales as 0.1 for mid-latitude, synoptic scale motions and that the ageostrophic wind, similarly, is small compared to the geostrophic wind. The development of quasi-geostrophic (QG) theory follows, which provides a convenient framework for diagnosing vertical motions. QG theory also indicates that divergence of the ageostrophic wind induces a transverse secondary circulation at straight jetstreak entrance and exit regions that serves to restore geostrophic balance while playing an important role in frontogenesis. In practice, the ascending branch of these transverse circulations is cited frequently as one ingredient of developing severe convective weather.
A combination of personal experience from undergraduate meteorology laboratory exercises, communications with practicing forecasters, and literature review on jetstreak dynamics reveals that such lessons of dynamic meteorology are ineffective when viewing related diagnostic fields using high-resolution gridded data. This mismatch between theory and practice constitutes a challenge to educators working to prepare new forecasters for professional service. A search of keywords from National Weather Service Area Forecast Discussions reveals inconsistent use of QG theory in forecasting. This result provides proxy evidence that forecasters seek to apply dynamic meteorology concepts in practice, but that such practice may vary based on forecaster experience, education, and forecast office priorities.
Case examples are prepared using GeMPAK and IDV to illustrate how traditional diagnostics of synoptic-scale dynamic meteorology cannot usually be effectively downscaled for application to high-resolution gridded output. Furthermore, calculations using the North-American Regional Reanalysis show that the probability distribution of Rossby Numbers peaks around 0.3 in the vicinity of mid-latitude jetstreak entrance and exit regions. This result suggests that forecasters must apply advanced dynamical concepts involving both synoptic-scale and mesoscale processes to adequately describe evolving forecast scenarios. Although QG theory is a useful way to understand dynamical characteristics of typical (i.e., composite) mid-latitude weather systems, it is an over simplification when applied in practice to individual cases, especially when forecasting impact weather at a specific point. Therefore, educators must adapt to the availability of high-resolution datasets by presenting case studies earlier, and more often throughout the student's curriculum, which are designed to highlight both strengths and weaknesses of theories in synoptic-scale dynamic meteorology.
Joint Session 3, Using technology to enhance learning: innovations and evidence (Part 1)
Tuesday, 22 January 2008, 1:30 PM-3:00 PM, 209
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