A couple of days ago I heard a familiar, but mysterious booming I’d not encountered in a while. Called “yamanari” (literally, “mountain roaring”) among Japanese mountaineers, it is an irregular deep booming sound, reminiscent of distant artillery. I first heard it about 23 years ago in the mountains near Tokyo, and that timing is significant for reasons I’ll explain below. It is inaudible in cities, drowned out by the hubbub. A wizard living atop Tokyo’s tallest peak (Kumotori, now highly radioactive, so thank goodness he had moved on) explained it as signaling the approach of a storm.
This was before the Net, and any respectable library in Japan had closed stacks, meaning you had to tell the librarian the title and author and wait while she got it for you; no browsing. So the best I could do was guess at the cause. From my flying I knew a lot about orogenic waves, i.e., stationary atmospheric waves that form over mountains in a wind, a lot like rapids in a stream. These shift as the wind changes, so I guessed the shifting was the cause. Probably in the ball park.
Yesterday, the Net turned up nothing about “yamanari,” except some guy’s Net name, but further searches brought up something called “acoustic gravity waves in the upper atmosphere,” and evidence suggesting they were related to earthquakes and auroras as well as violent storms. Sound waves form in the upper atmosphere and interact with the ionosphere. Wherever there is a boundary with distinct changes, such as mesosphere to ionosphere, any perturbance of that boundary can cause moving waves driven by gravity, like a pebble cast into a pond.
Apparently, such disturbances were heard worldwide in the months following the March 11 earthquake, in places without mountains, and experienced more as a hum than a booming. http://geochangemag.org/index.php?option=com_content&view=article&id=142:strange-sounds-in-sky-explained-by-scientists-&catid=1:global-news&Itemid=9
Because most of the sound is below the audible spectrum, i.e., very low frequency, what we hear is just the tip of the iceberg. This seems to sparked further scientific interest in the phenomenon, but it still remains a mystery. They’ve been reported in connection with atomic testing and earthquakes http://onlinelibrary.wiley.com/doi/10.1029/JZ072i005p01599/abstract , severe convective storms (i.e., thunderstorms), auroral activity, solar eclipse, volcanic eruptions, and “the passage of the solar terminator” http://www.ufa.cas.cz/files/OHA/0403.pdf . (The latter apparently means “twilight.”)
I think it could be expected as well with HAARP, but I cannot speculate as to the degree. What I can say is that the reason they were as clearly audible and frequent as they were 23 years ago, with no obvious connection to storms, was probably that we were approaching solar maximum.
When I heard the booming two days ago, it was distinct enough to be heard indoors, and it was followed by a minor storm. At the same time, however, Japan’s weather agency began predicting a major storm due to a low pressure system approaching from China. This one has all the power of a typhoon, with severe rain and wind forecasted for later today. I would expect the sounds we heard to be related to this larger storm.
I am conservative in my assessment of these things. Spring storms have been getting bigger each year, and several have seemed like typhoons in recent years, but this is the first time the weather service has warned of hurricane force winds and rains in conjunction with a storm of mid-latitude origin. Would any of you want to comment on why the powers-that-be might want to augment a storm heading to Japan right now?