Meteorology and Smoke Management ARB Smoke Management Workshop April 15-16, 2009

1. Meteorologyand Smoke ManagementARB Smoke Management WorkshopApril 15-16, 2009 Kevin Durkee Senior Meteorologist kdurkee@aqmd.gov South Coast Air QualityManagement District

2. Overview • Meteorology Review • Wind • Atmospheric Stability • Smoke Plume Behavior • SCAQMD Burn Day Decision Making

3. Meteorology & Air Quality • Meteorology controls accumulation and dispersion of smoke and air pollution. • Transport defines source and receptor areas. • Weather conditions affect burn conditions • e.g., humidity, fuel moisture, … • Weather conditions can accelerate or slow chemical reactions in the atmosphere. • Weather conditions can contribute to enhanced day-specific emissions rates.

4. WIND • Wind is described by Speed and Direction • Direction defined from True North by where the wind comes from • (N = 360°, E = 90°, S = 180°, W = 270°) • Wind Speed is typically measured in miles per hour, knots or meters per second or discussed in general descriptions • (e.g., Calm, Light, Gentle, Moderate, Fresh, Strong, Gale)

5. WIND • Wind is driven by a combination of: • pressure differences (gradients) • temperature gradients • e.g., land/sea breeze, • terrain • e.g., mountain/valley flows, Santa Ana winds

6. Thermally Driven Wind Flows • Sea Breeze / Land Breeze • Mountain / Valley Flows

7. Daytime Burning is Preferred

8. Effect of Wind Speedon Smoke Plumes • Wind speed determines the horizontal motion and bending of the plume from vertical • Wind Speed affects dilution of the plume • Light winds (stagnation) inhibits horizontal dispersion of pollutants

9. Effect of Wind Directionon Smoke Plumes • Wind Direction determines transport direction of the plume effluents • A varying Wind Direction will disperse the plume more effectively • Wind Directions are given as the direction from which the wind blows • (e.g., a southerly wind comes from the south and blows toward the north)

11. Southern California WildfiresOctober 22, 2007Strong Offshore Flow (Santa Ana Winds)

12. Southern California WildfiresOctober 25, 2007Weak Sea Breeze - Stagnation

13. Southern California WildfiresOctober 26, 2007Coastal Eddy – Southerly Winds

14. Atmospheric Stability • Stability is determined by the vertical temperature profile of the atmosphere • as measured by weather balloons, aircraft or remote sensing • Stable Air - • Resists vertical motion (less mixing) • Limits smoke dispersion • Unstable Air - • Encourages vertical motion (more mixing) • Aids smoke dispersion • Processes that heat from below or cool from above will make the atmosphere more unstable

15. Thermal Structure of the Atmosphere • Vertical temperature profile • Temperature usuallydecreases with altitude • A Temperature Inversion occurs when the temperature increases with altitude. • A very stable condition that reduces vertical mixing • An elevated inversion can create a lid that traps pollutants in a layer near the ground

16. Inversion Types • Radiation Inversion • Due to nighttime cooling of surface • Colder air pools in drainages • Marine Inversion • Occurs when air cooled by water undercuts warmer air above • Subsidence Inversion • Due to sinking (subsiding) warmed by compression • Occurs with high pressure aloft

17. Mixing Height • The vertical extent an air parcel will rise when heated • Mixing height rises as the day warms • Nighttime mixing heights are near the surface until daybreak • Mixing peaks in late afternoon • Mixed layer collapses after sunset

18. Dry Adiabatic Lapse Rate Neutral Layer Height Max Mixing Height Temperature Inversion (Stable Layer) Mixed Layer Max Surface Temp Temperature Mixing Height

19. Mixing Height Cross Section

20. Inversion over Los Angeles

21. Stability Effectson Smoke Plumes • An air parcel or plume is unstable and it will rise if it is more buoyant than the surrounding air. This occurs when the plume is hotter than the atmosphere. • An air parcel or plume is stable and it will not rise if it is less buoyant than the surrounding air. • The interaction of the plume with different atmospheric lapse rates determines the shape of the plume.

22. Stability Effects on Smoke Plumes (within inversion) (mixing below, inversion aloft)

23. VERY UNSTABLE CONDITION (LOOPING) 1000' SFC 10 ˚F NEUTRAL OR SLIGHTLY STABLE CONDITION (CONING) 1000' SFC 10 ˚F INVERSION CONDITION (FANNING) 1000' SFC 10 ˚F INVERSION BELOW, MIXING ALOFT (LOFTING) 1000' SFC 10 ˚F MIXING BELOW, INVERSION ALOFT (FUMIGATION) 1000' SFC 10 ˚F

24. Temperature Inversion over Los Angeles (1950s) - Fumigation

25. Smoke Dispersion (Ventilation) Processes(Putting it all together) • ADVECTION: Wind-Driven Transport • DIFFUSION: Microscale Motions that Expand the Pollutant Cloud • MECHANICAL TURBULENCE:Wind- & Terrain-Generated Mixing • THERMAL TURBULENCE & CONVECTION: Driven by Heating & Stability

26. AIR POLLUTION PLUME 1) Release 2) Travel And Dilution 3) Receptor Wind Temperature

27. Ventilation Index • VI = Mixing Height x Wind Speed / 1000 • Example: • Mixing Height = 5000 feet • Transport wind = 12 knots • Ventilation Index = 5000’ x 12 kt / 1000 = 60 kt-ft

28. Smog front reaching Riverside in afternoon

29. Visual Indicators of Stable Air • Stratus clouds – layered with little vertical motion • Smoke column drifts horizontally after limited rise • Poor visibility in lower levels due to accumulation of smoke or haze • Fog • Light, steady winds

31. Visual Indicators of Unstable Air • Vertical growth of clouds • Cumulus clouds • Gusty winds • Good visibility • Dust devils

33. Hotter burn with dry material and sufficient oxygen enhances smoke plume rise

34. SCAQMDBurn Day Decision Making • For Agricultural and Wildland Fire Use Burns • Burn Considerations • Meteorological Conditions • Air Quality • Burners also need: • Permission (burn authorization number) from the local air quality authority • Permission from local fire protection agency

35. Burn Decision Regulatory Documents • California Code of Regulations, Title 17 • Smoke Management Guidelines for Agricultural and Prescribed Burning • CCR Title 17, Sections 80100 – 801330 • Effective March 14, 2001 • http://www.arb.ca.gov/smp/regs/RevFinRegwTOC.pdf • Local Air Quality Disctrict Rules • SCAQMD Rule 444 – Open Burning • http://www.aqmd.gov/rules/reg/reg04/r444.pdf • SCAQMD Rule 208 – Permit and Burn Authorization for Open Burning • http://www.aqmd.gov/rules/reg/reg02/r208.pdf

36. CCR Title 17 • Provides for a daily burn authorization system that: • regulates agricultural & prescribed burning; • minimizes smoke impacts on smoke sensitive areas, avoids cumulative smoke impacts, and prevents public nuisance; • Can specify the amount, timing and location of each burn event

37. CCR Title 17 • The burn authorization system shall consider: • air quality; • meteorological conditions expected during burning, including wind speeds and directions at the surface and aloft, and atmospheric stability; • types and amounts of materials to be burned; • location and timing of materials to be burned; • locations of smoke sensitive areas; and • smoke from all burning activities, including burning in neighboring air districts or regions which may affect the district or region.

38. SCAQMD Jurisdiction Burn Areas • Area 40 – South Coast Air Basin • SCAQMD issues forecast by noon for tomorrow • Considers meteorology and air quality • Area 53 – Mojave Desert Air Basin • Forecasts by CARB in conjunction with local air districts • Area 55 – Salton Sea Air Basin • Coachella Valley forecasts by CARB with SCAQMD override for air quality • Imperial County forecasts by CARB in conjunction with local air districts

39. Title 17 Meteorological Criteria §80220. South Coast Air Basin. • A permissive-burn day will be declared when at least one of the following criteria is met: • The expected height of the inversion base, if any, near 6:00 a.m. at Los Angeles International Airport is 1,500 feet MSL or higher; • The expected maximum mixing height during the day is above 3,500 feet above the surface; • The expected mean surface wind between 6:00 a.m. and noon is greater than five miles per hour.

40. Central Los Angeles 6 am – Noon Winds 59% of CELA Hourly Morning Wind Speeds ≤ 5 mph

41. Morning Inversion ≥ 1500 feet • Analysis of SCAQMD Coastal Morning Soundings at Loyola Marymount University (1981-1985): • ~ 51% of days had either no inversion or an inversion base ≥ 1500 feet • Conversely, ~ 49% of days had a temperature inversion below 1500 feet

42. NO BURN DAY: Surface based Inversion Predicted LA Max Sfc Temp = 68˚F (20 C) Predicted Max Mixing = 1350 feet AM Winds < 5 mph

43. BURN DAY: Surface based Inversion Predicted LA Max Sfc Temp = 79˚F (26 C) Predicted Max Mixing = 7380 feet AM Winds < 5 mph

44. Title 17 Meteorological Criteria §80311. Mojave Desert Air Basin. • A permissive-burn day will be declared when the following criteria are met: • Near the time of day when the surface temperature is at a minimum, the temperature at 3,000 feet above the surface is not warmer than the surface temperature by more than 13 degrees Fahrenheit; • The expected temperature at 3,000 feet above the surface is colder than the expected surface temperature by at least 11 degrees Fahrenheit for 4 hours; • The expected daytime wind speed at 3,000 feet above the surface is at least 5 miles per hour.

45. Title 17 Meteorological Criteria §80280. Salton Sea Air Basin. • A permissive-burn day will be declared when at least three of the following criteria are met: • Near the time of day when the surface temperature is at a minimum, the temperature at 3,000 feet above the surface is not warmer than the surface temperature by more than 13 degrees Fahrenheit. • The expected temperature at 3,000 feet above the surface is colder than the expected surface temperature by at least 11 degrees Fahrenheit for 4 hours. • The expected daytime wind speed at 3,000 feet above the surface is at least 5 miles per hour. • The expected daytime wind direction in the mixing layer is not southeasterly.

46. Southern California’sAir Pollution Climatology • Abundant Sunshine & Heat • Drives photochemical reactions • Light Winds • Little horizontal dispersion • Strong, Low Elevated Temperature Inversion • Limits vertical mixing • Sea Breeze Transport • Pushes pollutants inland against mountains

47. Smog Formation InversionLayer SMOG Ocean Breeze

48. Combined impact of smoke and other air pollution is important

49. South Coast Air BasinPrimary Air Quality Impact Areas O3 O3 PM2.5, NO2 PM10, PM2.5 CO

50. Air Quality Index (AQI) • Non-dimensional method to communicate air quality levels and health risk • Applicable for multiple pollutants and simplifies public outreach • Ozone, PM2.5, PM10, NO2, & CO • Separates air quality into 6 categories • Good • Moderate • Unhealthy for Sensitive Groups (USG) • Unhealthy • Very Unhealthy • Hazardous