THE GREEN FLASH 

Written by Doug Weibel, SV Frolic

Have you seen the Green Flash?  If you have not, then do not watch the Pirates of the Caribbean movies and set your expectations by what you see there.  Real green flashes are not so flashy, but are pretty special nonetheless.  

Most often, the green flash is seen as the sun sets over water with no clouds on the horizon.  Just as the sun is going out of sight over the horizon, its light is refracted by layers of the lower atmosphere.  A green flash is most likely on warm, calm evenings with an inversion.  Seeing a green flash over the ocean often involves an inversion caused by the warmed daytime air sitting over the constant-temperature ocean.

I have no real information to support this, but the cruising community wisdom seems to be that to best see a green flash, you should not look at the sun while it is setting till the very last seconds.  I suppose this is because you don’t want your pupils to constrict by looking at the bright sun.  Just sneak quick peeks now and then to see how the sunset is progressing, and when there is just a sliver left, take a good look!  If you are lucky, the last remnant of the sun crossing the horizon will change from yellow to orange to neon green!  Sometimes just a speck of green, but sometimes a fiery ember.  It lasts just a moment, and that is part of the appeal.  A really good green flash will provoke a reaction!  We were with other cruisers on the deck at the Cape Santa Maria resort in the Bahamas for sundowners the first time I saw a really good green flash, and the whole assemblage broke out in exclamations and applause.  Jules Verne described the color of the green flash as one “which no artist could ever obtain on his palette, a green of which neither the varied tints of vegetation nor the shades of the most limpid sea could ever produce the like! If there is a green in Paradise, it cannot be but of this shade, which most surely is the true green of Hope.”

So what if you are already a green flash aficionado?  Did you know you can see a green flash with the sunrise?  Yep.  Obviously, this is much harder to do as not only do you need the correct conditions for the atmospheric phenomena to occur, but you have to be looking at the precise moment the first bit of sunlight clears the horizon.  You have no sunset to monitor and gauge the time to look, and you are not likely to find a source to tell you the precise second sunrise will occur in your location.  Seems I’m less likely to be in an anchorage with open water to the east, which may be much of the reason I haven’t pursued trying to see a morning green flash.  But, I bet a dedicated soul could get accustomed to the growing dawn light, know just when to look, and see one.

There are two other green flashes you can see.  I stumbled on this the other night.  It was perhaps the second night of a new moon, setting at around 9:30 which is fortunately earlier than “cruiser’s midnight”.  I stepped outside to sniff at the weather and admire the stars and immediately was taken with the setting moon, low on the horizon and a rich dusky orange.  I immediately wondered if the moon too can produce a green flash, and the answer is yes!  The sun’s light, reflected off the moon and then refracted by the lower atmosphere, can produce that subtle green.  Now, for full disclosure, I did not see a moon green flash that evening, and I don’t know that it would be possible with a new moon as the tips of the crescent are the last to dip below the horizon, so there is just not much light to work with.  Pictures I have seen of a moon green flash appear as a near-full moon setting pre-dawn, so if you want to see this elusive event, plan to get up early.

Now you might wonder if the setting moon can produce a green flash, then can a rising moon?  Apparently, yes.  Good luck on seeing that one.  Also, on the elusive side, there is a very rare blue flash!  You would be most likely to see this with the setting sun.  The refraction of the sun’s light bends the shorter wavelengths, blue and green, upwards so they are still above the horizon while the longer wavelengths, yellow and red, are blocked by the horizon.  However, blue light is scattered by the gasses and particles in the atmosphere, the reason the sky is blue.  So for a blue flash to occur, not only must the conditions for refraction be present, but the atmosphere must be very clear so that less scattering of the blue occurs.

One of the joys of cruising is that it seems to make it easier to have more of a connection with nature.  Why is it easier to step out on deck and look at the stars than it is to go out onto the back patio of a house?  I don’t know, but it seems to be the case.  Seeing the star field from a remote anchorage without light pollution feels like a real privilege, and seeing green flashes more so.  If you haven’t seen a setting-sun green flash yet, I hope you have an opportunity soon, and if you are already friends with this atmospheric phenomenon, then perhaps you can pursue its more elusive brethren.  Enjoy the sky!