本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)的ERA5客观再分析资料、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的红外卫星云图资料,对...本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)的ERA5客观再分析资料、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的红外卫星云图资料,对2006年6月14~20日发生在北大西洋上的一个爆发性气旋进行分析。该气旋由热带风暴阿尔贝托(Tropical Storm Alberto)变性后发展而来,是2000—2016年的17个夏季(6、7和8月)发生在北大西洋上的中心气压加深率最大的爆发性气旋个例。该气旋的演变过程可划分为初始、发展、成熟和衰亡四个阶段。本文旨在分析气旋演变过程中的云系特点、气旋爆发前后的高低空环流形势和高低空相互作用。分析显示,低层强烈的温度平流导致的大气斜压性是利于气旋发展的重要环境条件;500 hPa槽前的正涡度平流可为气旋发展提供动力强迫;高层异常PV的下传对气旋发展有促进作用;潜热释放(Q2/CP)主要位于对流层的中低层,这有利于气旋发展。利用Zwack-Okossi方程进行诊断分析发现,在该气旋发展过程中绝对涡度平流项和非绝热项的贡献为正,且非绝热加热对气旋快速发展的贡献最大,而温度平流项和绝热项对气旋发展起阻碍作用。展开更多
An explosive cyclone that took place over the Northwestern Pacific from 12 UTC 18 to 18 UTC 21 November 2007 was investigated.The synoptic situations and structure of this cyclone were documented by using the 1°&...An explosive cyclone that took place over the Northwestern Pacific from 12 UTC 18 to 18 UTC 21 November 2007 was investigated.The synoptic situations and structure of this cyclone were documented by using the 1°×1°final analysis data of the National Center for Environmental Prediction.This cyclone developed explosively around 18 UTC 19 and reached its maximum deepening rate(MDR,1.3 Bergeron)around 06 UTC 20 November 2007.At its MDR moment,the surface cyclone center was located in the downstream of the upper-level trough and northern entrance zone of the upper-level jet.The diagnosis using Zwack-Okossi equation suggested that cyclonic-vorticity advection and warm air advection acted to deepen this cyclone,while adiabatic cooling suppressed its development.In an investigation of this cyclone development,numerical sensitivity results obtained by using the Weather and Research Forecasting model showed that the latent heat release in the lower level had less contribution,whereas the surface sensible and latent fluxes played important roles.With a warmer ocean surface,the cyclone tended to intensify.Two topography tests were designed to examine the mountain influences on the development of this cyclone:removing a mountain and doubling the height of a mountain.Results show that the Changbai Mountains suppressed the development of the cyclone by preventing the southern moisture air from invading the inland.Without the moisture air,no latent heat release occurs when this cyclone passes over the Changbai Mountains.展开更多
The onset of South China Sea summer monsoon in 1998 occurred on May 21st. Using the U.S. National Centers for Environmental Prediction reanalysis data, this paper examines the physical process of the weakening of a su...The onset of South China Sea summer monsoon in 1998 occurred on May 21st. Using the U.S. National Centers for Environmental Prediction reanalysis data, this paper examines the physical process of the weakening of a subtropical anticyclone in West Pacific during the onset period using the Zwack-Okossi vorticity equation. Results show that during the pre-onset period, the positive vorticity advection in front of an upper tropospheric trough was the most dominant physical mechanism for the increase of the cyclonic vorticity on the 850-hPa layer over the South China Sea and its nearby region. The secondary contribution to the increase of the cyclonic vorticity was the warm-air advection. After the onset, the magnitude of the latent-heat warming term rapidly increased and its effect on the increase of the cyclonic vorticity was about the same as the positive-vorticity advection. The adiabatic term and divergence term contributed negatively to the increase of the cyclonic vorticity most of the time. Thus, the positive vorticity advection is the most important physical mechanism for the weakening of the West Pacific subtropical anticyclone over the South China Sea during the onset period.展开更多
文摘本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)的ERA5客观再分析资料、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的红外卫星云图资料,对2006年6月14~20日发生在北大西洋上的一个爆发性气旋进行分析。该气旋由热带风暴阿尔贝托(Tropical Storm Alberto)变性后发展而来,是2000—2016年的17个夏季(6、7和8月)发生在北大西洋上的中心气压加深率最大的爆发性气旋个例。该气旋的演变过程可划分为初始、发展、成熟和衰亡四个阶段。本文旨在分析气旋演变过程中的云系特点、气旋爆发前后的高低空环流形势和高低空相互作用。分析显示,低层强烈的温度平流导致的大气斜压性是利于气旋发展的重要环境条件;500 hPa槽前的正涡度平流可为气旋发展提供动力强迫;高层异常PV的下传对气旋发展有促进作用;潜热释放(Q2/CP)主要位于对流层的中低层,这有利于气旋发展。利用Zwack-Okossi方程进行诊断分析发现,在该气旋发展过程中绝对涡度平流项和非绝热项的贡献为正,且非绝热加热对气旋快速发展的贡献最大,而温度平流项和绝热项对气旋发展起阻碍作用。
基金This study is supported by the National Key R&D Program of China(Nos.2017YFC1404100 and 2017YFC 1404101)the National Natural Science Foundation of China(Nos.41775042 and 41275049).
文摘An explosive cyclone that took place over the Northwestern Pacific from 12 UTC 18 to 18 UTC 21 November 2007 was investigated.The synoptic situations and structure of this cyclone were documented by using the 1°×1°final analysis data of the National Center for Environmental Prediction.This cyclone developed explosively around 18 UTC 19 and reached its maximum deepening rate(MDR,1.3 Bergeron)around 06 UTC 20 November 2007.At its MDR moment,the surface cyclone center was located in the downstream of the upper-level trough and northern entrance zone of the upper-level jet.The diagnosis using Zwack-Okossi equation suggested that cyclonic-vorticity advection and warm air advection acted to deepen this cyclone,while adiabatic cooling suppressed its development.In an investigation of this cyclone development,numerical sensitivity results obtained by using the Weather and Research Forecasting model showed that the latent heat release in the lower level had less contribution,whereas the surface sensible and latent fluxes played important roles.With a warmer ocean surface,the cyclone tended to intensify.Two topography tests were designed to examine the mountain influences on the development of this cyclone:removing a mountain and doubling the height of a mountain.Results show that the Changbai Mountains suppressed the development of the cyclone by preventing the southern moisture air from invading the inland.Without the moisture air,no latent heat release occurs when this cyclone passes over the Changbai Mountains.
文摘The onset of South China Sea summer monsoon in 1998 occurred on May 21st. Using the U.S. National Centers for Environmental Prediction reanalysis data, this paper examines the physical process of the weakening of a subtropical anticyclone in West Pacific during the onset period using the Zwack-Okossi vorticity equation. Results show that during the pre-onset period, the positive vorticity advection in front of an upper tropospheric trough was the most dominant physical mechanism for the increase of the cyclonic vorticity on the 850-hPa layer over the South China Sea and its nearby region. The secondary contribution to the increase of the cyclonic vorticity was the warm-air advection. After the onset, the magnitude of the latent-heat warming term rapidly increased and its effect on the increase of the cyclonic vorticity was about the same as the positive-vorticity advection. The adiabatic term and divergence term contributed negatively to the increase of the cyclonic vorticity most of the time. Thus, the positive vorticity advection is the most important physical mechanism for the weakening of the West Pacific subtropical anticyclone over the South China Sea during the onset period.
