2. Mixing Height (MH) National Weather Association’s 40th Annual Meeting 2015 10/20/20152 The height above the surface that aerosols vertically disperse. Also referred to as boundary layer depth. Important in fire weather as it is used to predict how well smoke from a fire will ventilate. Important to air pollution by providing the depth pollutants will disperse to.

3. Motivation National Weather Association’s 40th Annual Meeting 2015 10/20/20153 R20 – Research from Desert Research Institute shows that there are likely more accurate methods to calculate mixing height. Currently no standard method to calculate mixing height. No verification data readily available to verify mixing height. Highlight a potential new dataset.

4. Methods of Calculating MH National Weather Association’s 40th Annual Meeting 2015 10/20/20154 Holzworth Method - (Parcel Method). WR Parcel Method – Same as Holzworth, but 2 degrees added to surface temperature. Stull Method – Similar to Holzworth but uses Virtual Potential Temperature. Bulk Richardson Number – Uses a combination of convective/shear turbulence Utilized data from NCEI Integrated Global Radiosonde Archive for upper air analysis.

5. National Weather Association’s 40th Annual Meeting 2015 10/20/20155

6. National Weather Association’s 40th Annual Meeting 2015 10/20/20156 Holzworth Stull WR Holzworth Richardson

7. Mesowest Above Surface Networks National Weather Association’s 40th Annual Meeting 2015 10/20/20157

8. Verification Method National Weather Association’s 40th Annual Meeting 2015 10/20/20158 Ceilometer data from Viasala CL31. Persistent Cold-Air Pool Study (PCAPS) and University of Utah. Multiple methods for calculation of mixing height from data. Used the Idealized Profile method for this study. Ceilometer not co-located with upper air site.

9. Ceilometer Time/Height National Weather Association’s 40th Annual Meeting 2015 10/20/20159

10. Ceilometer Time/Height National Weather Association’s 40th Annual Meeting 2015 10/20/201510 Holzworth Stull WR Holzworth Richardson

11. Ceilometer Time/Height National Weather Association’s 40th Annual Meeting 2015 10/20/201511 Holzworth Stull WR Holzworth Richardson

12. Verification National Weather Association’s 40th Annual Meeting 2015 10/20/201512 Holzworth WR Holzworth Stull Richardson

13. Verification (Spring) National Weather Association’s 40th Annual Meeting 2015 10/20/201513 * Below 2000 m

14. Verification PCAPS (Winter) National Weather Association’s 40th Annual Meeting 2015 10/20/201514

15. Verification (Year) National Weather Association’s 40th Annual Meeting 2015 10/20/201515 * Below 2000 m

16. Verification (Year) National Weather Association’s 40th Annual Meeting 2015 10/20/201516 * Below 2000 m

17. Summary National Weather Association’s 40th Annual Meeting 2015 10/20/201517 Initial verification shows there is significant uncertainty in the sounding approach compared to the ceilometer. Of the sounding approaches blending the methods seems to be the most skillful. Caveats – Dataset too small to be statistically significant. – Most useful method may be geographically dependent. – Ceilometer data is only useful if aerosols are present. – Verification method for calculating mixing height is not as robust as one would hope for. R20 – Apply method to models through SmartInits.

18. Acknowledgements National Weather Association’s 40th Annual Meeting 2015 10/20/201518 John Horel – University of Utah Joseph Young – University of Utah/Mesowest Persistent Cold Air Pool Study (PCAPS)