stable atmosphere. unstable atmosphere mixing height definition the mixed layer can be defined as...
TRANSCRIPT
![Page 1: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/1.jpg)
Stable Atmosphere
![Page 2: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/2.jpg)
Unstable Atmosphere
![Page 3: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/3.jpg)
Mixing Height Definition
The mixed layer can be defined as the altitude above ground level to which pollutants vertically disperse. Fearon
![Page 4: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/4.jpg)
Mixing Height Definition
The height of the layer adjacent to the ground over which an emitted inert non-buoyant tracer will be mixed (by turbulence) with a time scale of about one hour or less. Beyrich
![Page 5: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/5.jpg)
Mixing Height Definition
The thickness Z, of the mixed layer, defined as the location of a capping temperature inversion or statically stable layer of air.
Glossary of Meteorology
![Page 6: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/6.jpg)
Reasons for Capping Inversion
Because of summertime Pacific High, average inversion ht along California coast is about 400 meters
Marine layer is usually 1500 to 2000 feet deep in Bay Area
Rising air cools, and descending air warms, making the mixed layer adiabatic
![Page 7: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/7.jpg)
Types of Mixing
MECHANICAL MIXING
•Predominates at nighttime
•Turbulence due to wind shear
•Turbulence due to obstacles
•Turbulence is proportional to wind speed (ie. H= 125 U)
![Page 8: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/8.jpg)
Types of Mixing Height
CONVECTIVE MIXING HEIGHT
•Is a daytime phenomenon - due to heating by the sun
•On sunny or partly cloudy days, is dominate from one hour after sunrise to one hour before sunset (13 deg above horizon). On overcast days, figure two hours.
![Page 9: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/9.jpg)
Convective VS Mechanical
Convective Mixing usually dominates over Mechanical Mixing
During very windy conditions smoke plumes will stay close to the ground
![Page 10: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/10.jpg)
WHERE TO GET INFORMATION ON MIXING HEIGHTS
![Page 11: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/11.jpg)
Holtzworth Techinque
![Page 12: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/12.jpg)
NOAA models (such as ETA or SRI) can generate soundings for current time or future time for any location. www.arl.noaa.gov/ready/cmet.html
Model-Based Soundings
![Page 13: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/13.jpg)
www.weather.nps.navy.mil/profiler/coastprof.html
![Page 14: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/14.jpg)
DRI Web Page with Mixing Hts
www.cefa.dri.edu/Operational_Products/NCEP_Exp/exp_index.htm
![Page 15: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/15.jpg)
Model Calculations
Model being developed by EPA (AIRMET) will calculated hourly mixing ht values using Monin Obukhov length and friction velocity
Need measurements of net radiation and heat flux, in addition to winds, temperature and RH
![Page 16: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/16.jpg)
Complex Terrain
Upper air data tend to be collected over simple terrain
Extrapolating mixing depths to elevated terrain is not straight forward
![Page 17: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/17.jpg)
Mixing Depth Observationsat Flat-Land Sites in Bay Area
![Page 18: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/18.jpg)
Issue #1
How to estimate mixing depth on site?
![Page 19: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/19.jpg)
Estimating Mixing Heights
Most plans say will use Oakland Sounding and test burns
Burn elevation may be higher than Oakland mixing depth
How is height of smoke determined during test burns
![Page 20: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/20.jpg)
Issue #2
Burning before meeting the mixing height prescription.
![Page 21: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/21.jpg)
TITLE 17, SECTION 80160, PART J
“Require the land manager or his/her designee conducting a prescribed burn to ensure that all conditions and requirements stated in the smoke management plan are met on the day of the burn event and prior to ignition.”
![Page 22: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/22.jpg)
•Many plans prescribe a mixing depth of 1500 feet agl
•There is a reference to this value in a table in the “Smoke Management Training Workshop Manual”
•The problem is that this height is often the maximum mixing depth, and is not reached until 2 – 3 pm.
Meeting Prescription
![Page 23: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/23.jpg)
END
![Page 24: Stable Atmosphere. Unstable Atmosphere Mixing Height Definition The mixed layer can be defined as the altitude above ground level to which pollutants](https://reader031.vdocuments.us/reader031/viewer/2022020308/56649f2f5503460f94c48e07/html5/thumbnails/24.jpg)
Holtzworth Technique