During the early stages of their invasion of Ukraine, Russia experienced a significant loss when its flagship, the Moskva, was sunk by Ukrainian forces in the Black Sea. The vessel’s destruction was a surprise not only to the Russians, but also to many who observed this conflict at the time, but now researchers believe they have evidence that the Ukrainian army benefited from an unusual weather phenomenon that made the attack possible.

According to the work of two radar experts at the Swedish Defense Research Agency and a meteorologist from the Swedish Meteorological and Hydrological Institute, the Ukrainian military were only able to see and target the Moskva missile cruiser because of a temperature inversion that occurred at the time. During this unique event, the usual situation switched around, whereby cooler air was at lower altitudes with warmer air above it.

This, they argue, allowed the Ukrainians’ radar signal to refract off the atmosphere, carrying it much further than would normally be possible. This is why the Ukrainians were able to see and subsequently sink the warship.

“Before launching an anti-ship missile,” the researchers write in their paper, “a target must first be detected and positioned, for example by an accompanying radar system. However, when the missiles hit the Moskva she was well beyond the normal radar horizon of any ground-based radar system, making the ship undetectable under normal circumstances.”

The fact that the Ukrainians were able to hit the Moskva was therefore something of a mystery, which led some to suggest that a US aircraft had tipped them off to its location, a rumor that has since been denied.  

Interestingly, as the researchers note, an alternative explanation was offered by the newspaper Ukrainska Pravda in December 2022. According to a series of interviews they conducted with military personnel, weather conditions had allowed the Ukrainian’s R-360 Neptune anti-ship missile system, complete with its search-and-track radar (known as Mineral-U) to spot the vessel in the Black Sea.

The impact the atmosphere can have on radar has been studied for almost a century. It is known that radio waves can be attenuated (weakened or interfered with) by rain and are normally refracted slightly towards the Earth due to variations in the atmosphere.

The existing models used to calculate radar’s horizon in “normal” atmospheric conditions can therefore sometimes underestimate or overestimate its reach due to prevailing meteorological conditions.

“In this work, we have examined [the Ukrainska Pravda’s claim] by calculating the atmospheric refractivity from meteorological reanalysis data and thereafter applying an electromagnetic wave propagation model,” the authors write. “We found that at the time of the missile launch the atmospheric conditions were indeed allowing a ground-based radar to detect targets close to the sea surface at much longer distances than normal.”

“The results show that atmospheric conditions must be considered carefully, even during warfare, as their impact on radar wave propagation can be considerable. With increasingly detailed and accurate meteorological reanalysis data available, it is now possible to perform in-depth analyses of past atmospheric propagation conditions.”

The study is published in the Bulletin of the American Meteorological Society.