1. ICE-POP WORKSOP Sep 5-9 2016, Korea
FOG FORMATION,
DEVELOPMENT AND DISSIPATION:
MEASUREMENTS AND VARIABILITY
Ismail Gultepe
Cloud Physics and Severe Weather Research Section,
Science and Tech Branch, Environment Canada, Toronto, Ontario, M3H5T4
ICE-POP WORKSOP Sep , Korea

2. Objectives Classify fog types Evaluate instruments for Vis
Emphasize variability, scale issues

3. VIS reduction due to fog particles
Vis=f(Vrh;Vmix;Vliquidfog;Vicefog;
Vdrizzle;Vrain;Vsnow;Vblows)

4. Vis versus Nd

5. Vis versus LWC

6. VIS VERSUS f(LWC;Nd)

7. Vis parameterization
RUC Vis
Fixed LWC

8. FOG MICROPHYSICAL PARAMETERIZATION MATERHORN 2015 JAN

9. Ice crystal shapes Jan 28 2010 Jan 28 2010 March 7 2010 March 4 2010

10. Fog Formation Saturation wrt water or ice CCN and IN nuclei
Nd=f(CCN;Sw)
Ni-f(IN, Si)

11. Fog Development
When air parcel has enough CCN(IN) and RH~100% or >100%, droplets (ice crystals) form.
Development or fog intensity increases with increasing Nd(Ni) or LWC(IWC)
It happens when a cooling processes occurs and IN or CCN increases
Cooling occurs due to advection, radiation, subsidence, mixing, precipitation, upslope etc.

12. Fog Dissipation Dissipation of fog happens due to =precipitation,
=mixing with warm and dry air, and
=heating processes such as SW heating and warm air advection.

13. MATERHORN 2015 ICE FOG DISSIPATION
MATERHORN: Mountain Terrain Atmospheric Modeling and Observations Project

14. Visibility Instruments Based on extinction of visible light using forward and backscattering techniques

15. VIS FOR ICE FOG CONDITIONS
1.7 KM
0.3 KM
0.5 KM

16. Microphysical sensors

18. Variability in Measurements

20. Comparisons of Vis for snow conditions
FD12P
SENTRY

21. Comparisons of snow PR

22. SWE SENSOR amount water in snow layer

23. Variability/Uncertainty in Model Predictions
SCALE ISSUES
MICROPHYSICAL SCHEMES
VISIBILITY PARAMETERIZATIONS
UNCERTAINITY IN THE BOUNDARY CONDITIONS

24. MODEL VIS-SCALE ISSUES

25. LWC comparisons at various
forecast hours

26. Vis versus RHw
5% accuracy of RHw measurements is needed.

27. VIS-PRrain

28. CONCLUSIONS
Multiple sensor approach (MSA) is needed to measure same physical parameter (e.g. precip rate, extinction…)
Multiple model runs/ensemble simulations at different initialization times are needed because of variability in the predicted microphysical parameters.
Microphysical parameterizations are needed to be improved
Observational based nowcasting schemes are needed.