During the movement of Typhoon Hato(2017)over land,heavy rainfall occurred when the spiral rainband which was about 100 km distance away from the center of the typhoon passed the Dayao Mountain(with an elevation of 1....During the movement of Typhoon Hato(2017)over land,heavy rainfall occurred when the spiral rainband which was about 100 km distance away from the center of the typhoon passed the Dayao Mountain(with an elevation of 1.2 km).In this study,the structures and forming mechanism of the heavy rainband along the mountain range are investigated by using high-resolution model simulations.The results show the importance of topography in causing the heavy rainband.Upslope of the steep terrain lifts the cyclonic flow to produce strong upward motion when the rainband passes across with high wind speed.At the same time,the warm and humid air is lifted to the steep slope,causing unstable energy to accumulate over the windward slope,which is conducive to the occurrence of rainfall.In particular,the convective cells generated upstream of rainband will further strengthen and develop due to the uplift when they move close to the mountain foot.Some precipitation particles in the convective cells fall to the ground while others move downstream with the intense updrafts,forming heavy rainfall near the summit.As a result,the largest accumulative rainfall coincides well with the orientation of the mountain ridge.展开更多
Following classical theory,a two-layer frontal model is designed.It assumes that frontal surface is the zero-order discontinuity of density.In this paper,the model is used to study orographically distorted and occlude...Following classical theory,a two-layer frontal model is designed.It assumes that frontal surface is the zero-order discontinuity of density.In this paper,the model is used to study orographically distorted and occluded fronts.It is indi- cated that the distortion and occlusion of cold fronts are different under different conditions of orography.Frontal in- tensity also influences the distortion and occlusion.Some rules are revealed and compared with observations.In addition,we have analysed the vertical structure of cold front above mountains and found that frontal surface may be bulged under the influence of orography when it climes the mountain.The bulge of frontal surface is just like the bore as pointed out by Long (1972) when he analysed fluid over obstacles.展开更多
基金Key-Area Research and Development Program of Guangdong Province of China(2020B1111200001)National Natural Science Foundation of China(41875070,41575040)+1 种基金Beijige Open Research Fund for Nanjing Joint Center of Atmospheric Research(NJCAR2018MS02)Science and Technology Program of Yunnan(2018BC007)。
文摘During the movement of Typhoon Hato(2017)over land,heavy rainfall occurred when the spiral rainband which was about 100 km distance away from the center of the typhoon passed the Dayao Mountain(with an elevation of 1.2 km).In this study,the structures and forming mechanism of the heavy rainband along the mountain range are investigated by using high-resolution model simulations.The results show the importance of topography in causing the heavy rainband.Upslope of the steep terrain lifts the cyclonic flow to produce strong upward motion when the rainband passes across with high wind speed.At the same time,the warm and humid air is lifted to the steep slope,causing unstable energy to accumulate over the windward slope,which is conducive to the occurrence of rainfall.In particular,the convective cells generated upstream of rainband will further strengthen and develop due to the uplift when they move close to the mountain foot.Some precipitation particles in the convective cells fall to the ground while others move downstream with the intense updrafts,forming heavy rainfall near the summit.As a result,the largest accumulative rainfall coincides well with the orientation of the mountain ridge.
文摘Following classical theory,a two-layer frontal model is designed.It assumes that frontal surface is the zero-order discontinuity of density.In this paper,the model is used to study orographically distorted and occluded fronts.It is indi- cated that the distortion and occlusion of cold fronts are different under different conditions of orography.Frontal in- tensity also influences the distortion and occlusion.Some rules are revealed and compared with observations.In addition,we have analysed the vertical structure of cold front above mountains and found that frontal surface may be bulged under the influence of orography when it climes the mountain.The bulge of frontal surface is just like the bore as pointed out by Long (1972) when he analysed fluid over obstacles.
