We show that low-level jets(LLJs)occurred in 11 out of 22 radiosonde profiles in late austral summer over the coastal region of the Amundsen Sea Embayment,with ten of the LLJs directed offshore.The LLJs had core speed...We show that low-level jets(LLJs)occurred in 11 out of 22 radiosonde profiles in late austral summer over the coastal region of the Amundsen Sea Embayment,with ten of the LLJs directed offshore.The LLJs had core speeds from 9 to 32 m s^(-1),jet core heights from 80 to 800 m,and were associated with strong,low-level temperature inversions.Seven of the observed offshore LLJs were reasonably simulated by the polar-optimized Weather Research and Forecasting(Polar WRF)model,with output from the model subsequently used to elucidate their generation mechanisms.This study shows that one of the offshore LLJs simulated by the Polar WRF was caused by katabatic winds,while the remaining six were caused by the enhancement of katabatic winds by synoptic forcing in response to a low-pressure system over the Bellingshausen Sea,i.e.,the offshore wind component associated with this system plays a crucial role in the enhancement of the katabatic LLJ.Examination of the Polar WRF output further shows that the LLJs extended over large areas of the Amundsen Sea Embayment,resulting in substantially enhanced near-surface wind speeds over both the Thwaites and Pine Island ice shelves,as well as the open ocean over the continental shelf.The wind-driven forcing associated with the LLJs could perhaps have important impacts on the redistribution of snow over the ice shelves significantly,as well as to affecting sea-ice and ocean circulation variability,including the transport of relatively warm water over the continental shelf to the ice shelf cavities and extension basal melting.展开更多
以0505号强台风"海棠"为例,利用"侵台台风之飞机侦察及下投式探空仪观测实验"(Dropsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)提供的高垂直分辨率GPS下投式探空仪(Dropsonde)...以0505号强台风"海棠"为例,利用"侵台台风之飞机侦察及下投式探空仪观测实验"(Dropsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)提供的高垂直分辨率GPS下投式探空仪(Dropsonde)观测资料,研究和比较了2次观测时段"海棠"的动力及热力结构差异,结果表明,第2次观测时的"海棠"在气旋式入流的强度和范围、高层暖区的强度和范围等方面均较第1次明显增强和扩大,且"海棠"环流的顶层发展出了一定强度和厚度的反气旋出流,加上"海棠"逐步移入高海温区和处于有利的弱垂直风切变环境中,"海棠"进一步增强;其次,用该观测资料对Frank等1999和2001年的数值模拟结果(垂直风切变通过激发热带气旋眼墙内部垂直运动的一波不对称结构而导致热带气旋结构的不对称分布)进行了验证。结果表明,观测分析结果与Frank等的数值模拟结果能较好地吻合,解释了环境垂直风切变对台风不对称结构的可能影响。展开更多
基金support from the European Union’s Horizon 2020 research and innovation framework program under Grant No.101003590(PolarRES)funding from the Indian Institute of Technology Kharagpur and the Ministry of Education,Government of India。
文摘We show that low-level jets(LLJs)occurred in 11 out of 22 radiosonde profiles in late austral summer over the coastal region of the Amundsen Sea Embayment,with ten of the LLJs directed offshore.The LLJs had core speeds from 9 to 32 m s^(-1),jet core heights from 80 to 800 m,and were associated with strong,low-level temperature inversions.Seven of the observed offshore LLJs were reasonably simulated by the polar-optimized Weather Research and Forecasting(Polar WRF)model,with output from the model subsequently used to elucidate their generation mechanisms.This study shows that one of the offshore LLJs simulated by the Polar WRF was caused by katabatic winds,while the remaining six were caused by the enhancement of katabatic winds by synoptic forcing in response to a low-pressure system over the Bellingshausen Sea,i.e.,the offshore wind component associated with this system plays a crucial role in the enhancement of the katabatic LLJ.Examination of the Polar WRF output further shows that the LLJs extended over large areas of the Amundsen Sea Embayment,resulting in substantially enhanced near-surface wind speeds over both the Thwaites and Pine Island ice shelves,as well as the open ocean over the continental shelf.The wind-driven forcing associated with the LLJs could perhaps have important impacts on the redistribution of snow over the ice shelves significantly,as well as to affecting sea-ice and ocean circulation variability,including the transport of relatively warm water over the continental shelf to the ice shelf cavities and extension basal melting.
文摘以0505号强台风"海棠"为例,利用"侵台台风之飞机侦察及下投式探空仪观测实验"(Dropsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)提供的高垂直分辨率GPS下投式探空仪(Dropsonde)观测资料,研究和比较了2次观测时段"海棠"的动力及热力结构差异,结果表明,第2次观测时的"海棠"在气旋式入流的强度和范围、高层暖区的强度和范围等方面均较第1次明显增强和扩大,且"海棠"环流的顶层发展出了一定强度和厚度的反气旋出流,加上"海棠"逐步移入高海温区和处于有利的弱垂直风切变环境中,"海棠"进一步增强;其次,用该观测资料对Frank等1999和2001年的数值模拟结果(垂直风切变通过激发热带气旋眼墙内部垂直运动的一波不对称结构而导致热带气旋结构的不对称分布)进行了验证。结果表明,观测分析结果与Frank等的数值模拟结果能较好地吻合,解释了环境垂直风切变对台风不对称结构的可能影响。
