1

DIAGNOSTIC EVALUATION OF METEOROLOGICAL DIAGNOSTIC EVALUATION OF METEOROLOGICAL MODEL PERFORMANCEMODEL PERFORMANCE

Don LehrmanDon Lehrman

William KnuthWilliam 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

• 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

July-August 2000 Episode

4

Preliminary Draft Report (cont)

• Central San Joaquin Valley– Visalia

• Coast and Delta Region– Walnut Grove Tower (ozone, temperature, winds)

July 1999 Episode

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

9

10

Upper Air Sites -CCOS

11

July 30 Summary

Chart Date and TimeHeight (m-

agl) Coastal and Bay Delta Sacramento ValleySJV Nocturnal Jet / Fresno

Eddy Southern SJV Outflow

200

Shultz Eddy Formed Fresno Eddy formed Bakersfield Eddy formed but suspect strong SW outflow

500

Shultz Eddy present Fresno Eddy centered

near Parlier

Light and variable winds

1000North Bay questionable

200North Bay questionable Offshore flow questionable

Southwest Sac Valley questionable

Fresno Eddy present

500

Fresno Eddy present

1000Northbay coastal hills

Not consistent with Richmond and Travis measured winds

Southwest Sac Valley questionable

200

500

1000

200North Bay questionable Light and variable

winds Moderate jet present

500

1000

July 30 at 0400 PST

July 30 at 1000 PST

July 30 at 1600 PST

July 30 at 2200 PST

12

July 31 SummaryChart Date and Time

Height (m-agl) Coastal and Bay Delta Sacramento Valley

SJV Nocturnal Jet / Fresno Eddy Southern SJV Outflow

200

North Bay questionable

500

1000

MM5 brings Sac Valley air to Bay area which is not

consistent with measurements

MM5 brings Sac Valley air to Bay area which is not

consistent with measurements

MM5 brings Sac Valley air to Bay area which is not

consistent with measurements

200

MM5 closes Fresno eddy. Unconsistent with Parlier

measurements.

500

1000

200

May be more flow through

Delta region than MM5 produces

Light and variable winds

500

1000

North Bay questionable

200

Does not represent Delta inflow breeze

May be more flow through Delta region than MM5

produces

500

North Bay questionable

1000

July 31 at 0400 PST

July 31 at 1000 PST

July 31 at 1600 PST

July 31 at 2200 PST

13

August 1 SummaryChart Date and Time

Height (m-agl) Coastal and Bay Delta Sacramento Valley

SJV Nocturnal Jet / Fresno Eddy Southern SJV Outflow

200

Poor agreement between MM5 and streamlines. Also winds

offshore look unrealistic

Poor agreement between MM5 and streamlines. Travis and

SacX winds ignored

Fresno Eddy did not form

500

Poor agreement between MM5 and streamlines

Poor agreement between MM5 and streamlines

Fresno Eddy did not formPoor agreement between MM5

and streamlines

1000

200

Fresno Eddy did not form

500

Poor agreement between MM5 and measured winds

Poor agreement between MM5 and measured winds

MM5 winds NW Fresno look bogus

1000

MM5 winds NW Fresno look bogus

MM5 winds SE Bakersfield look bogus

200

500

1000

200

500

1000

Aug 1 at 0400 PST

Aug 1 at 1000 PST

Aug 1 at 1600 PST

Aug 1 at 2200 PST

14

15

16

17

18

19

20

21

22

23

24

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 DIAGNOSTIC EVALUATION OF METEOROLOGICAL MODEL PERFORMANCEMODEL PERFORMANCE

Don LehrmanDon Lehrman

William KnuthWilliam Knuth

Prepared for the September 14, 2006 CCOS Technical Committee Meeting