MM5 SIMMULATIONS OF MESOSCALE TRANSPORT FROM THE SFBA TO SACRAMENTO & SJV

DURING A CCOS 30 JULY-02 AUG. 2000 OZONE EPISODE

By

Tesfamichael B. Ghidey, LBNL, SJSU

Robert D. Bornstein, SJSU

Robert Van Buskirk, LBNL

3 June 2004

Prepared for BAAQMD

MM5 configurationMM5 configuration• Version 3.6.0Version 3.6.0• Three domains Three domains

– 36, 12, 4 km36, 12, 4 km– 55 x 55, 91 x 91, 190 x 190 grid points 55 x 55, 91 x 91, 190 x 190 grid points

• 32 sigma levels 32 sigma levels – up to 100 mbup to 100 mb– first full sigma level at 19 m first full sigma level at 19 m

• GDAS IC and BCGDAS IC and BC• Analysis nudging only for V and T forAnalysis nudging only for V and T for

– 36 km domain36 km domain– above PBLabove PBL

• No obs nudgingNo obs nudging• Five layer soil model, Gayno-Seaman PBLFive layer soil model, Gayno-Seaman PBL• Start: 1200 UTC on 28 JulyStart: 1200 UTC on 28 July• Length: 7.5 daysLength: 7.5 days• LBNL LINUX single processor: 15 daysLBNL LINUX single processor: 15 days

Output focus-areasOutput focus-areas• V (meso format; m/s): V (meso format; m/s):

barb = 1, flag = 5 barb = 1, flag = 5 • 36 km synoptics: 36 km synoptics:

NWS vs MM5 NWS vs MM5 • 4 km (sub-areas)4 km (sub-areas)

– SFBA + C. Valley: SFBA + C. Valley: regional regional

transporttransport– Carquinez St.: Carquinez St.:

flow split into CVflow split into CV– Livermore: ozone maxLivermore: ozone max

700 hPa NWS PREVIEW:700 hPa NWS PREVIEW:1200 UTC OR 0500 PDT1200 UTC OR 0500 PDT

Movement of inland H causes Movement of inland H causes episodes episodes

• Pre-episode: over Nevada Pre-episode: over Nevada

• Episode days: moves SW to over SJV Episode days: moves SW to over SJV and intensifiesand intensifies

• Post-episode: dissipatesPost-episode: dissipates

SAC ozone day: SJV Syn H at max intensity; SW flow over SFBASAC ozone day: SJV Syn H at max intensity; SW flow over SFBA

Surface NWS PREVIEW: Surface NWS PREVIEW: 1200 UTC or 0500 PDT1200 UTC or 0500 PDT

• Note: Warm-core upper-H projects Note: Warm-core upper-H projects down-ward to form sfc inverted down-ward to form sfc inverted thermal L thermal L

• Pre-episode: over Nevada Pre-episode: over Nevada

• Episode days: moves over SJV and Episode days: moves over SJV and intensifiesintensifies

• Post-episode: weakensPost-episode: weakens

LIV episode day: trough moves NW, forms closed low, with N-S axis thru LIV episode day: trough moves NW, forms closed low, with N-S axis thru central CA; SE-flow over Sac central CA; SE-flow over Sac

MM5 Domain-1: 700 hPa WINDS PREVIEW

• NWS charts approximate pressure NWS charts approximate pressure center locationscenter locations

• Cannot give flow details in SFBA, Car-Cannot give flow details in SFBA, Car-quinez Strait, & SJVquinez Strait, & SJV

• MM5 simulations showMM5 simulations show– Pre-episode H: E of SFBA over NevPre-episode H: E of SFBA over Nev– Episode days: bulge from H extends Episode days: bulge from H extends

westward over SFBAwestward over SFBA– Post-episode H: back E of SFBA over Post-episode H: back E of SFBA over

Az Az

H H

H

SJV episode: L correctly gone; inland H moves S to Az/Utah border; bulge forms SJV episode: L correctly gone; inland H moves S to Az/Utah border; bulge forms correctly into 2correctly into 2ndnd H (vs. “apparent split” obs); Fresno eddy forms (not in obs); H (vs. “apparent split” obs); Fresno eddy forms (not in obs);

NW flow over SFBA correctly curves S to SJV (vs SE flow over SFBA)NW flow over SFBA correctly curves S to SJV (vs SE flow over SFBA)

L

MM5 Domain-1: SFC WINDS PREVIEW (12 UTC OR 05 PDT)

• Movement (N & then S) of thermal L Movement (N & then S) of thermal L

from S-CA cause episodesfrom S-CA cause episodes– Convergence into LIVConvergence into LIV– Increased flow to Sac from SFBAIncreased flow to Sac from SFBA– Increased flow into SJV from SFBAIncreased flow into SJV from SFBA– Moves offshoreMoves offshore

• Flow details in Domain-3Flow details in Domain-3

L

L

SJV episode day: not much change in Lows (correct); more flow S SJV episode day: not much change in Lows (correct); more flow S into SJVinto SJV

DOMAIN-3: 700 hPa PREVIEW (2100 UTC or 0400 PDT)

• SFBA + CV FOCISFBA + CV FOCI• Offshore H formation & Fresno eddy Offshore H formation & Fresno eddy

movement cause episodesmovement cause episodes• Initial flow from S does not produce SFBA Initial flow from S does not produce SFBA

to Sac transportto Sac transport• Newly formed H directs SFBA flow to Sac & Newly formed H directs SFBA flow to Sac &

con-current eddy blocks SFBA flow into SJVcon-current eddy blocks SFBA flow into SJV• When eddy moves to NWhen eddy moves to N

– SFBA flow into Sac blockedSFBA flow into Sac blocked– SFBA flow into SJV allowed SFBA flow into SJV allowed

L

H

SJV episode: Fresno eddy moved N & H moves inland (both better defined than in D-1); SJV episode: Fresno eddy moved N & H moves inland (both better defined than in D-1); flow around eddy blocks SFBA flow to SAC, but forces it S into SJVflow around eddy blocks SFBA flow to SAC, but forces it S into SJV

DOMAIN-3: SUMMARY OF SFC TRANSPORT TO LIVERMORE (KEY

HOURS)

• Daytime confluence E of LIV (on Mt Daytime confluence E of LIV (on Mt peak) causes episode (max ozone on peak) causes episode (max ozone on Mt peak)Mt peak)– Flow from N from Carquinez StraitsFlow from N from Carquinez Straits– Flow from W thru GGGFlow from W thru GGG– Upslope from E-side of hills E of LIVUpslope from E-side of hills E of LIV

• For episode needFor episode need– Strong confluenceStrong confluence– Low speedsLow speeds

Episode afternoon (1400 PDT): W flow thru GGG & strong con into Eastern LivEpisode afternoon (1400 PDT): W flow thru GGG & strong con into Eastern Liv

DOMAIN 3: SFC TRANSPORT TO SAC SUMMARY

• TRANSPORT FROM SFBA BLOCKED BY TRANSPORT FROM SFBA BLOCKED BY OPPOSING FLOW ON DAYS BEFORE OPPOSING FLOW ON DAYS BEFORE AND AFTER SAC EPISODEAND AFTER SAC EPISODE

• TRANSPORT FROM SFBA NOT TRANSPORT FROM SFBA NOT BLOCKED ON DAY OF SAC EPISODEBLOCKED ON DAY OF SAC EPISODE

LIV-episode late-afternoon (1800 PDT): flow to SAC from SFBA blockedLIV-episode late-afternoon (1800 PDT): flow to SAC from SFBA blocked

SAC-episode late-afternoon (1800 PDT): flow to SAC from SFBA not blockedSAC-episode late-afternoon (1800 PDT): flow to SAC from SFBA not blocked

DOMAIN 3: SFC TRANSPORT TO SJV SUMMARY

• TRANSPORT FROM SFBA TO SJV TRANSPORT FROM SFBA TO SJV MUST NOT BE BLOCKED BY MUST NOT BE BLOCKED BY OPPOSING FLOWSOPPOSING FLOWS

• FLOW INTO SJV MUST FLOW INTO SJV MUST – NOT BE TOO FAST NOT BE TOO FAST – SHOW CONFLUENCESHOW CONFLUENCE

SAC EPISODE NIGHT: TRANSPORT TO SJV FROM SFBA IS BLOCKEDSAC EPISODE NIGHT: TRANSPORT TO SJV FROM SFBA IS BLOCKED

SJV EPISODE NIGHT: TRANSPORT TO SJV FROM SFBA & CON WINDSSJV EPISODE NIGHT: TRANSPORT TO SJV FROM SFBA & CON WINDS

THE END