The National Weather Service in Honolulu just announced a wind advisory for the Haleakala Summit until 6pm tonight. These sorts of bulletins are pretty typical now and then, but a recent study from four University of Hawaii scientists seems to show that the all-important Trade Winds–which literally breathe life and rain into the Hawaiian Islands–just aren’t blowing like they used to.
Here’s what Hawaii News Now reported last night:
The number of days of northeast trade winds is decreasing, according to new research from the University of Hawaii. And while it means more days with muggy weather and volcanic haze, it also is resulting in longer-term effects for the state.
The state’s climate, rain forests and generally delightful nature all come from the trades. If they stop blowing, the islands will dry up and life here just won’t be the same.
The study was actually published back in June in the Journal of Geophysical Research. It has four authors: Jessica A. Garza, Pao-Shin Chu, Chase W. Norton and Thomas A. Schroeder, all from UH’s Department of Meteorology. I seem to have let my subscription lapse, which means I won’t be paying the $25 the journal wants for a copy of the actual article. But here’s the article’s abstract, which is available online:
Changes in the frequency and intensity of the prevailing northeast and east trade winds from 1973-2009 are analyzed from four land stations in the Hawaiian Islands. A nonparametric robust trend analysis indicates a downward trend in northeast trade wind frequency since 1973. At the Honolulu International Airport, northeast trade wind days usually occurred 291 days per year 37 years ago are observed to occur only 210 days per year in 2009. In contrast, the frequency of the east trade winds has increased over the past 37 years. Comparison of observations from four ocean buoys with land stations for the last 26 years (1984–2009) is presented. The northeast trade frequency is found to decrease for all eight stations while the east trade winds are found to increase in frequency. These results are similar to the longer (1973–2009) data set. Most buoys revealed an increase in trade wind speeds since 1984. The NCEP/NCAR reanalysis II data are used to analyze surface winds and sea level pressure (SLP) over the north Pacific. A northeast to east shifting of winds and an increase in SLP is found to occur from the 1980s to the 2000s epoch. Linear trends in reanalysis II from 1980 to 2009 indicated a strengthening of northeast trade winds over the Hawaiian Islands and in the subtropical eastern North Pacific with an extension of increased northerlies off the California coast. Meanwhile, southeast trades in the eastern North Pacific reduced their strength. Changes in trades in the western Pacific are relatively small.
What’s causing this decrease in winds is still unknown, according to the Hawaii News Now story, though climate change–that mischievous bugbear that continues to haunt faithful Republicans–is a prime suspect. The kinds of wind changes discussed in the study are still pretty small, but if I were the Hawaii Tourism Authority, which prospers because of Hawaii’s pleasing, gentle climate, stuff like this would worry me considerably.
Photo: NASA/Wikimedia Commons