Re: [Phys-l] Humidity and visibility

[Bernard Cleyet <bernardcleyet@redshift.com>]

If Bright Science still has Mim's -- evidently not as not on the SAS sale page.  However,  they do have the instruction to make ones own haze monitoring station.

http://www.scifair.org/downloads.html#haze


Evidently Forrest Mims was the first to use LEDs as detectors.


bc purchase a couple of the R/S Sun & Sky Monitoring Stations when they were remaindered a few months ago.

> or aerosols from pine trees (e.g., Lake Tahoe).

The early Alta California Spanish explorers reported such haze.  Later Republicans used it as justification for not accepting pollution control.


On 2010, Jun 01, , at 08:24, LaMontagne, Bob wrote:

> The kind of haziness you refer to requires water to condense into tiny droplets - so a relative a relative humidity near 100 percent is usually required. The other important variable is the presence of condensation nuclei for droplets to form. Haziness is a complex interplay of these two quantities. Here in the northeast (RI) we seldom get haziness unless there is a strong inversion layer (warm air overlying cooler air) that limits convection and traps water vapor and condensation nuclei in a shallow layer.  Houston and coastal Florida are other good examples of humidity haze. A notable exception was this weekend where lots of condensation nuclei were drifting down to RI from the wildfires in Montreal - causing extreme haze (1/2 mile visibility) even though the relative humidity was only around 70 percent (although there was an inversion around 3-4000 ft throughout most of the day).
>
> Haziness in the dry southwest can be caused by scattering from power plant pollutants (e.g., Grand Canyon) or aerosols from pine trees (e.g., Lake Tahoe).
>
> Bob at PC