BMKG Sounds Rumble Due To Lightning Reflection

Topographic map of Malang, East Java, which is a basin and hilly, which is prone to inversion layer formation. (Photo: Antara)

JAKARTA - The Meteorology, Climatology and Geophysics Agency (BMKG) said that the boom that occurred in Malang, East Java and a number of other areas was caused by the reflection of the sound of lightning in the inversion layer in the atmosphere. mystery, the cause is the presence of an inversion layer in the atmosphere, unless it is proven that there is a meteor, "said BMKG Coordinator for Earthquake and Tsunami Mitigation, Daryono in Jakarta, Saturday. He explained that in meteorology there is a term known as" temperature inversion ", which is the crushed layer of cold air. by a layer of warmer air in the atmosphere. This air layer is formed when warm air rises above the colder air layer, then spreads and expands in the atmosphere. The heat sources can come from industrial activities, fires, traffic, the release of heat from the sun's radiation received, radiation from the earth's surface, etc. This phenomenon, he said, is actually unusual because in normal conditions the higher the air temperature, the cooler it should be. , so that the phenomenon of inversion layer formation can only occur at a certain time as long as the conditions for its formation are met. The inversion layer can also be formed when there is a pressure anomaly in the atmosphere or there is hot air moving from another place. Hot air and gases moving up into the atmosphere, he said, will be retained by this warm air layer because it forms a kind of hood (inversion cap) that covers it. areas and trapping gases and heat rising from the earth. He gave a simple example, that is, if you are near an industrial area, you sometimes smell an unpleasant smell that lasts a long time in certain weather conditions. This is because gases or pollutants cannot rise to the atmosphere and are trapped under the inversion layer. The inversion layer has been recognized as a factor in the haze disaster in a number of countries. The severe haze events in 1948 in Donora, Pennsylvania, (USA) and in 1952 in London, England, were caused by an increase in the inversion layer in the atmosphere. The London smog disaster lasted a week and killed up to 12,000 people, but the gases and pollutant particulates are not the only thing that the inversion layer holds. Some people have reported hearing strange noises during the formation of the inversion layer in the atmosphere. Sound waves originating from trains, cars, lightning, and other sound sources can bounce off the inversion layer and be heard elsewhere. This occurs because the inversion layer acts as a less than perfect reflector of acoustic waves, radio waves and even light. The inversion layer can also make sounds louder so that they are heard far away. Like honking a car horn in a closed garage, it's certainly louder than honking on a highway. This is because the sound is trapped in a narrow space. The inversion layer makes the sound of lightning unable to spread upwards or spread in all directions, because it is trapped and can only spread to the surface of the earth. In this case the sound of lightning will be heard louder and can be heard far away in the area covered by the inversion layer. The sound of lightning is like traveling through an audio channel similar to a "tropospheric duct." In theory, sound is an acoustic wave that has been proven to be reflected off an inversion layer. Under conditions of temperature inversion, sound waves are refracted downwards, and therefore can be heard at a greater distance. This is the basic concept of why the inversion layer can make the sound of lightning heard far away due to the multi-reflection process. The sound of lightning when it is far away and under certain atmospheric conditions can change its "anatomy" so that it is no longer like the original lightning sound at the source, but can resemble a boom. Apart from reflecting ordinary acoustic waves, the inversion layer is also capable of reflecting extreme mechanical and acoustic waves in the form of shock waves . So that it can spread sound and vibration effects over a further area. Furthermore, he said, topography plays an important role in developing and resisting the inversion layer. Cold air can accumulate in valley basins or lowlands on the coast under certain weather conditions. So that areas with this kind of morphology are prone to inversion phenomena during the rainy season.

One of the many areas in Indonesia that is prone to the formation of an inversion layer is the Malang area. With a topography in the form of a basin surrounded by mountains, this area is vulnerable to temperature inversion under certain conditions, namely when cold air is trapped in the valley and a layer of warm air covers it from above. At the time the Malang basin is covered with an inversion layer, it seems as if a "giant tunnel" is formed. Enough with a lightning incident that occurs nearby or from another place, the boom will spread along the valley and reflect repeatedly, similar to the formation of an echo, as reported by some Malang residents a few days ago, said Daryono.

This news was previously broadcast on VOI by quoting from Antara News Agency with the title "BMKG: Banging Sounds in Malang Caused by Inversion Layers in the Atmosphere".

However, some time later, Antara corrected the news and we broadcast it with the title "BMKG says the boom was caused by the sound of lightning."