text | "China Science Daily" Reporter Liao Yang Correspondent Li Hezhao
Photos of "Haihao" of the Yellow Sea on January 7, 2021. Photo provided by the research team
January 7, 2021, the Yellow Sea in Qingdao "wasted" and a large area of white clouds rose on the vast sea surface, under the rising sun, it was like a fairyland. This rare wonder is called the "Haihao" phenomenon. Li Xiaofeng's team, a researcher at the Institute of Oceanography of the Chinese Academy of Sciences, combined several in-orbit satellite data to conduct a comprehensive observation and analysis of the related thermodynamics, biology and dynamics processes of the "Haihao" phenomenon, and accurately simulated the phenomenon using the regional marine meteorological coupled model (ROMS-WRF). Related research was recently published in the Journal of Atmospheric Science.
study found that the upflow induced by the strong cold current in winter compensated for the marine upper heat lost due to the sharp drop in temperature, making the maximum sea temperature difference that day reach nearly 20 degrees Celsius. Under the huge sea temperature difference and corresponding interaction, seawater evaporates rapidly, making the water vapor near the sea surface close to saturation. This is the main reason for the "Haihao" phenomenon.
Li Xiaofeng introduced that the occurrence of the "Haihao" phenomenon is dominated by thermal instability factors, rather than dynamic factors. Thermodynamic instability promotes the evaporation of surface seawater. The emergence of the "Haihao" phenomenon usually requires two conditions: "condensation nucleus" and "temperature difference".
team embedded the chemical aerosol radiation transmission module (GOCART) into the coupling model and found that 0.5~1.5 micron sea salt particles as the main condensation nucleus were released into the low-altitude atmosphere as the evaporation process, promoting the formation of "Haihao". At the same time, this also increased the PM2.5 content on that day by 50%.
In addition, in view of the special rough texture characteristics of the sea surface presented by the "Haihao" phenomenon, the research team developed a new image analysis method - the SAR ellipse length algorithm. The results show that the further offshore line, the stronger the atmospheric instability, which causes the convection of the underlying atmosphere to continue to develop and form a larger sea surface cell texture structure.
Related paper information:
https://doi.org/10.1175/JAS-D-22-0065.1
