Occasionally, my mind takes me back to Eniwetok by way of clouds. At night, when the sky is bright with moonglow and clouds are moving in familiar ways, I see and feel the celestial dome of Eniwetok nearly five decades ago. Oh, that I could hear the lapping of waves as well.
It is a fleeting transfiguration I liken it to visions told by immigrants of seeing long-gone family and homeland. The connection between people, places and events that shape our lives profoundly seems latent, ready to be recalled anytime the conditions are right.
What special aspects of clouds stay in my memory so tenaciously? Perhaps it is their differences. Like snowflakes, no two clouds are exactly the same. A colleague has reminisced: "...some types of clouds didn't look the same at Eniwetok as they do over Kentucky -- especially at night." He continued: "I see cumulus clouds drifting between the moon and me in Kentucky; as they commence obscuring the moon, it grows fainter and fainter until it is totally obliterated. Then, when the midpoint of the cloud has passed, the moon begins to emerge once more. At Eniwetok," he explained. " the clouds appeared much less dense, and the image of the moon never went away completely. It stayed visible --sometimes brilIiant-- through the cloud. How can that be?"
Maybe my friend was witness to magic in the South Sea Island skies--legendary intrigue of the South Pacific. It s the stuff that draws us to island sunsets and moonlight on coconut palms. We' ve long been aware that mid-latitude cloudwatchers relocated to low-latitude (or, high-latitude] soon perceive the clouds to be different. Sometimes more, sometimes less, but different than they appeared back home.
It is predictable my Kentucky friend would notice such cloud antics. Since the time when weather work emerged from the primordial soup of the alchemists, it's practitioners have been known by their peculiar way of looking skyward in search of clouds on the first step they make out-of-doors. That reflex glance toward the heavens is the first lesson the entered apprentice learns--a habit formed to last a lifetime. Clouds are the wcatherman's (Oops! weatherperson's...) stethoscope--a common but reliable instrument for diagnosing rhythms of the air's inner workings and hidden mechanisms (mushroom varieties not included).
What makes clouds at Eniwetok so different--so translucent by Kentucky standards? Some of the explanation lies with the abundance of time--professional and discretionary available for watching clouds at this tiny island. There are physical explanations to validate my friend's observations as well.
First, there are climatological aspects that differ greatly between Kentucky and Eniwetok; and one that influences clouds, especially at night, stems from the time of day (on average) that rainfall peaks. Low latitude rain generally follows the sun. That is maximum rainfall coincides with maximum heating. Therefore, the greatest vertical development of clouds at Eniwetok --the time they are most dense--is in the afternoon. By nightfall, rain has usually diminished a lot or ended, and cloud thickness is minimized. What remains are puffy cumulus with a little vertical extent, and the moon shines brightly through them.
Unlike the tropical sea and island regime, Kentucky's rainfall pattern is thoroughIy mid-latitude continental . In that, rainfall tends to be nocturnal, which leads to greater cloud development between late afternoon and the predawn hours just when we'd like to see the moonlight. Kentucky also has far more stratiform clouds that become effective moon-blockers.
Another factor in creating the phenomena my friend noticed is the angle at which the moon's reflected light strikes the earth. Since the moon travels in about the same plane as the sun, it is seen practically overhead at Eniwetok--and sometimes directly overhead. Never is it seen so high in the sky over Kentucky. Consequently, the incoming light passes through far less attenuating atmosphere in reaching Eniwetok than it does to reach Kentucky. Further, because of the difference in the relative angles at which the light reaches the earth at the two latitudes, a given measure of light is spread over more area in Kentucky than it is at Eniwetok. The combined results lead to enhanced brilliance at low latitudes, and make memorable views of the moon through relatively thin clouds.
There may be other reasons as well— things having to do with cloud physics, size and density of condensation nuclei, mean lifting condensation levels, trajectories, and so forth. People with more curiosity should frequent a technical library. One should remember however, that too much understanding increases the risk of shattering another South Seas fantasy. As for me, when someone asks why the moon looks a certain way through the clouds, I'm most apt to reply, "...it depends."
Donald Whitman
E-Mail: Donwhitman1@aol.com
Kansas City, August 1998
