Potential Associations Between Low-Level Jets and Intraseasonal and Semi-Diurnal Variations in Coastal Chlorophyll—A Over the Beibuwan Gulf, South China Sea

Remote Sensing

Shuhong Liu¹  Yuanjian Yang¹  Guicai Ning²  Danling Tang³  Chengcheng Liu⁴  Hong Yan⁴ 

[1] Collaborative Innovation Centre on Forecast and Evaluation of Meteorological Disasters, School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing 210044, China;Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Hong Kong 999077, China;Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), & Guangdong Key Laboratory of Ocean Remote Sensing, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China;

关键词: chlorophyll-a;    sea surface temperature;    low-level jets;    intraseasonal and semi-diurnal scales;    Beibuwan Gulf;    Himawari-8;   

DOI  :  10.3390/rs13061194

来源: DOAJ

【 摘 要 】

Low-level jet (LLJ) significantly affects the synoptic-scale hydrometeorological conditions in the South China Sea, although the impact of LLJs on the marine ecological environment is still unclear. We used multi-satellite observation data and meteorological reanalysis datasets to study the potential impact of LLJs on the marine biophysical environment over the Beibuwan Gulf (BBG) in summer during 2015–2019. In terms of the summer average, the sea surface wind vectors on LLJ days became stronger in the southwesterly direction relative to those on non-LLJ days, resulting in enhanced Ekman pumping (the maximum upwelling exceeds 10 × 10^–6 m s^–1) in most areas of the BBG, accompanied by stronger photosynthetically active radiation (increased by about 20 μmol m^–2 s^–1) and less precipitation (decreased by about 3 mm day^–1). These LLJ-induced hydrometeorological changes led to an increase of about 0.3 °C in the nearshore sea surface temperature and an increase of 0.1–0.5 mg m⁻³ (decrease of 0.1–0.3 mg m⁻³) in the chlorophyll-a (chl-a) concentrations in nearshore (offshore) regions. Intraseasonal and diurnal changes in the incidence and intensity of LLJs potentially resulted in changes in the biophysical ocean environment in nearshore regions on intraseasonal and semi-diurnal timescales. The semi-diurnal peak and amplitude of chl-a concentrations on LLJ days increased with respect to those on non-LLJ days. Relative to the southern BBG, LLJ events exhibit greater impacts on the northern BBG, causing increases of the semi-diurnal peak and amplitude with 1.5 mg m⁻³ and 0.7 mg m⁻³, respectively. This work provides scientific evidence for understanding the potential mechanism of synoptic-scale changes in the marine ecological environment in marginal seas with frequent LLJ days.

【 授权许可】

Unknown