Observation of Low-Level Jets in the Eastern Tropical Indian Ocean Based on Shipborne Coherent Doppler Lidar

In contrast to the Pacific and Atlantic Oceans, the Indian Ocean has lacked in-situ observations of wind profiles over open sea areas for decades. In 2021, a shipborne coherent Doppler lidar（CDL） was used to observe in-situ wind profiles in the eastern tropical Indian Ocean. This equipment successfully captured low-level jets（LLJs） in the region, and their characteristics were thoroughly analyzed. Results reveal that the observed wind speed of LLJs in the eastern Indian Ocean ranges from 6-1 m s-1 to 10 m s during the boreal winter and spring seasons, showing a height range of 0.6 to 1 km and two peak times at 0800 and 2000 UTC. This wind shear is weaker than that in land or offshore areas, ranging from 01 s-1 to 0.006 s-1. Moreover, the accuracy of the CDL data is compared to that of ERA5 data in the study area. The results indicate that the zonal wind from ERA5 data significantly deviated from the CDL measurement data, and the overall ERA5 data are substantially weaker than the in-situ observations. Notably, ERA5 underestimates northwestward LLJs.