Friday, 30 October 2009

High altitude vog

The rule of thumb on Mauna Kea is that vog, the stuff given off by the active volcano Kilauea, tends not to get above approximately 10,000 feet. When you see haze in the atmosphere above this level it's usually attributed to "Gobi Desert dust"; dirt from the Gobi Desert in Asia blown into the atmosphere by local storms and then brought to Hawai`i across the Pacific by high level winds.

I can't recall ever reading the research paper but apparently there was a study carried out some years ago using the observatories on Mauna Loa (probably the NOAA atmospheric monitoring facility) that found the haze was in fact not due to dust but pollutants from China's industrial regions. If anyone is aware of the study I refer to, I'd be more than grateful for a link to the paper!

With the rather active state of Kilauea recently, it seems on days when the trade winds are not blowing and convection becomes dominant on the Big Island, vog does get to the summit levels and even higher. My guess is that there is so much vog compared to recent years that an observable amount now breaks through the usual inversion layer and escapes to higher altitudes whereas previously some vog might get to higher levels although it wouldn't be enough to be noticed by the casual observer.

Although I can't be certain the picture above shows vog, about 10 minutes after sunset the sky took on a very unusual colour with a pinkish tone high above us. The GOES infrared satellite images indicated there was no cirrus nearby yet there was clearly something at mid-to-high altitude and the vog at slightly lower elevations, such as 9,000 feet at Hale Pohaku, was amongst the worst I had experienced. Whatever it was, it made for another gorgeous if somewhat unusual sunset!

A larger version of the picture is available by clicking on the image above. Incidentally, Subaru is to the left with the twin Kecks on the right. Haleakala, on the island of Maui, is visible to the far right.

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