DIAGNOSTIC EVALUATION OF METEOROLOGICAL MODEL PERFORMANCE

1. DIAGNOSTIC EVALUATION OF METEOROLOGICAL MODEL PERFORMANCE Don Lehrman William Knuth Prepared for the September 14, 2006 CCOS Technical Committee Meeting

2. Evaluation Objective • Objective is to evaluate how MM5 handles critical meteorological processes such as: • Nocturnal jet • Fresno eddy • Land-sea breeze • Delta winds • Vertical mixing • Fluxes across defined planes • Slope flows

3. Preliminary Draft Report July-August 2000 Episode • Central San Joaquin Valley • Visalia • Flux Plane • North San Joaquin Valley • Stevenson • Sacramento Valley • Pleasant Grove • Granite Bay (temperature and winds) • Coast and Delta Region • Bodega Bay • Franklin Field • Walnut Grove Tower (ozone, temperature, winds) • Sierra Slope Winds • Trimmer

4. Preliminary Draft Report (cont) July 1999 Episode • Central San Joaquin Valley • Visalia • Coast and Delta Region • Walnut Grove Tower (ozone, temperature, winds)

5. Draft Report Conclusions • For the SJV: The timing and magnitude of the major meteorological features exhibited in the measured data—nocturnal jet, eddy, diurnal variation and depth of the up-valley/down-valley flows-- were captured in the model-derived wind fields • Flux calculations across a plane in the central SJV using the measured and modeled winds from three monitoring sites agreed well • For the SacV: It was noted that although the modeled timing and magnitude of the major meteorological features in the wind fields generally agreed with the measured data, there were potential serious errors in the wind speed detail

6. Draft Report Conclusions (cont.) • In the Delta region (Walnut Grove tower and SacX profiler): Results were mixed in that modeled and actual wind speed magnitudes were generally similar, there were serious discrepancies in the reported wind direction • At the coast (Bodega Bay): There were strong vertical shears and well defined land-sea breeze regimes measured which were were captured remarkably well by the model-derived wind • For the Sierra slope-induced flows (Trimmer). The timing and depth of the drainage and upslope winds were reproduced closely by MM5

7. Suggested Additional Tasks • Examine the horizontal windfields – same features • How well does the model handle terrain induced winds? • The latter task is to use surface observations

8. Horizontal Wind Field • Compared MM5 output to subjectively drawn streamlines at 3 levels and at 4 times over the diurnal cycle • 200, 400 and 1000 meters • 04, 10, 16 and 22 PST • July 30th, July 31st, and August 1st

10. Upper Air Sites -CCOS

11. July 30 Summary

12. July 31 Summary

13. August 1 Summary

25. Summary • For the most part, MM5 seems to emulate the observed wind features very well in the SJV • With some exceptions, MM5 emulated the observed wind features well in the SacV • MM5 did not seem to handle the observed winds in the (north) Bay and Delta as well as in the other regions • Sierra slope winds not behaving as expected

26. Remaining Tasks • Respond to reviewers comments • Examine terrain induced winds using surface data • Determine which set of surface data to use • Examine winds in cross-sections orthogonal to the Sierra crest • Final report

27. DIAGNOSTIC EVALUATION OF METEOROLOGICAL MODEL PERFORMANCE Don Lehrman William Knuth Prepared for the September 14, 2006 CCOS Technical Committee Meeting