| Big Bog | |
|---|---|
 Rain gauge on a ridge overlooking the Big Bog | |
| Highest point | |
| Elevation | 5,400 ft (1,600 m) |
| Coordinates | 20°43′44″N156°05′31″W / 20.729°N 156.092°W /20.729; -156.092 |
| Geography | |
  Big Bog | |
TheBig Bog is ahigh-altitude bog on the island ofMaui, the largest in theHawaiian Islands. It is located onHaleakala's eastrift zone, at the border betweenHāna Forest Reserve andHaleakalā National Park. It is alleged to be one of thewettest places on Earth, with a reported annual rainfall of 404 inches (10,300 mm)[1] for the period 1992-2018 according to theUniversity of Hawaiʻi at Mānoa.
While the summit ofMount Waiʻaleʻale onKauai has long been considered the wettest place in the Hawaiian Islands, and was claimed to be the second wettest place on Earth,[2] itsNOAA-reported annual rainfall of 373.85 inches (9,495.8 mm)[3] is exceeded by Big Bog's 30-year average.
The Big Bog has atropical rainforest climate (KöppenAf), with no observable dry season and nearly constant torrential rainfall. Prior to the establishment of the station there in 1992, rainfall for Big Bog was estimated at around 4,600 millimetres (180 in) per year. However, the first full year of recorded data showed 13,995 millimetres (551.0 in) of rainfall, which is one of the highest annual rainfall totals measured in the Hawaiian Islands.[4] Since then, the annual average has been recorded as 404 inches (10,300 mm). Clear days are essentially nonexistent, and even when it is not raining, it is almost certainly cloudy or foggy. The lack of adequate drainage has caused moisture to accumulate, forming the bog.[4]
| Climate data for Big Bog (HN-164) 1993-2011 | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average rainfall inches (mm) | 32.17 (817.0) | 24.94 (633.6) | 52.07 (1,322.7) | 38.51 (978.1) | 25.52 (648.2) | 28.51 (724.2) | 32.80 (833.0) | 31.04 (788.5) | 26.07 (662.2) | 38.31 (973.1) | 38.02 (965.8) | 36.42 (925.0) | 404.38 (10,271.4) |
| Source:[5] | |||||||||||||
The Big Bog lies at 5,400 feet (1,600 m), very close to thetrade wind inversion layer, leading to persistent transport of moisture rich air by the northeast trade winds up the steep mountain slopes. These trade winds condense to form clouds and precipitation. Its reputation as the cloudiest place in the Hawaiian Islands is supported by its average solar radiation and potentialevapotranspiration being the lowest amongst recorded locations in the state, and relative humidity and cloud attenuation the highest.[4]
"30-year mean precipitation at Big Bog for the POR of 1978-2007 is 404.4".
"Wai'ale'ale means 'rippling water' or 'overflowing water' in Hawaiian and is the second wettest spot on earth".
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