(Lack of) Snow on Hawaii

I know you might be looking at the title of today’s post and thinking “snow? Hawaii? How do those two things go together?” and the answer would be mountains. You may also be thinking “why should I care?” and the answer to that would be that snow can be a reservoir of freshwater when melted in the warmer months and is needed for skiing and other such activities (which have business applications); snow can also be culturally important or act as an indicator of climate.
Snow is intermittent on Hawaii’s tallest mountains; Mouna Kea and Mouna Loa (respectively, 4207 meters (13,802 feet) and 4169 meters (13,678 feet)). Snow is usually present, if it all, in November to April, but has been seen in summertime. These two mountains see several large (30 centimeters (one foot) or more of snow, extending down to 3300 meters (10,827 ft) elevation, sometimes even lower. Sometimes snow is seen on Haeleakala, on Maui, with a 3055 meter (10,023 feet) elevation.
Mauna Kea and Mauna Lua, seen via satellite, and covered in snow. Image credit: NASA Earth Observatory.
This brings us to today’s article, Monitoring and Projecting Snow on Hawaii Island, written by Chunxi Zhang, Kevin Hamilton, and Yuqing Wang. Published in 2017 in the American Geophysical Union’s journal Earth’s Future, the authors use snow on the aforementioned mountains to look at climate change. 
The authors did not have an observation-based database about snow cover on Hawaiian mountains, so they created what is, to their knowledge, the first such database. They used daily satellite data, which was then used to find seasonal and annual data. Snow cover varies widely from year to year; some years there was almost no snow on the mountains, other years had 70 days of the November to April period (these less snowy/ snowier seasons correspond to the El Nino and La Nina weather phenomenons). On occasion, the snow extended down to 2600 meters (8530 feet).
With the database in place, the authors turned to a climate model known as the “Weather Research and Forecasting” model (scientists aren’t always known for their original naming…). They made some adaptations to fine-tune the model for Hawaii. The first run of the model was from the start of 1990 to the end of 2015, and it agreed with what they had seen in the observational database. A second run was aimed at 2080 to 2105, adjusting for the expected emission of greenhouse gases, and also factoring in changes in sea surface temperature, humidity, air temperature, and other factors. This had an effect of a large reduction of snowfall. The elevation at which freezing occurred rose 600 to 700 meters (1969 to 2297 feet). These drastic effects are one of many that are likely to be seen in the coming decades if nothing is done to change the course of the climate; one of the many ways science impacts our everyday lives.



Hansen, Kathryn. Snow-Capped Summits in HawaiiNASA Earth Observatory. 25 Dec 2016. Web.
The source of the used image. The page has a few other photos and information about snow on Hawaii.
Zhang, C., K. Hamilton, and Y. Wang (2017), Monitoring and projecting snow on Hawaii Island, Earth’s Future, 5doi:10.1002/2016EF000478
Today’s main post.



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