Sunday, November 26, 2023

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Tracking Radar Detects Animals Trapped within Tropical Hurricanes


Super Typhoon Lekima imaged from space by a NASA satellite

The source is “Journal of Geophysical Research: Biogeosciences”.

Following the occurrence of Super Typhoon Lekima in mainland China in August 2019, several bird species were observed in locations where they were previously not documented. A recent study uncovers the probable explanation for their presence.

Some winged animals, like birds and insects, can get stuck in the center of a tropical cyclone and be transported as it moves. While many studies have looked at the intentional movement of these creatures, only a small number have utilized radar to monitor those caught in the eye of a storm.

Huang and colleagues analyzed polarimetric radar data from Lekima’s approach towards the coast of Wenzhou, a city on China’s central coast. Through radar analysis, they detected biological particles within the storm’s center based on their distinctive characteristics, such as strong differential reflectivity, low cross-correlation coefficient values, and fluctuating differential phase values.

The researchers observed an increase in echoes from flying animals as the storm Lekima approached the coast, by paying attention to signals that met specific criteria. As the storm reached land, the distribution of these creatures within the eye shifted from circular to oblong, leading the researchers to conclude that exhausted birds were seeking refuge on the ground. Additionally, some birds may be carried by the cyclone up to hundreds of kilometers away from where it makes landfall.

The authors observed that Lekima captured more birds compared to Hurricane Irene in 2011. In contrast, the eye of Irene mainly contained swarms of insects.

The authors suggest that utilizing radar to monitor the flight patterns of animals and insects within the eyes of tropical cyclones could provide insight into the movement of invasive species and aid in differentiating between meteorological and biological signals for weather tracking purposes. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2023JG007533, 2023)

“I am a science writer, Nathaniel Scharping (@nathanielscharp).”

Reference: Scharping, N. (2023), Radar observations of animals affected by tropical cyclones, Eos, 104, https://doi.org/10.1029/2023EO230363. Published on 27 September 2023.

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