Gotowa bibliografia na temat „Mid-troposphere Cyclones”

In this paper a simple relationship is employed to investigate relative impacts on the movement and landfall of tropical cyclone in the Bay of Bengal region when geopotential height of different troposphere levels is used as an input. Five tropical cyclone during pre-monsoon and post-monsoon season over the Bay of Bengal region has been selected for the study. The RS/RW data of coastal stations namely Kolkata (Dumdum), Dhaka, Agartala, Bhubaneswar, Visakhapatnam, Machlipatnam, Chennai and Karaikal has been collected for the period of the cyclones under study. The geopotential height of different standard levels has been plotted against the time for the stations for every cyclone. The study suggests that the cyclone moves towards and cross near the station having relatively steeper decrease in geopotential height upto mid tropical level followed by increased in geopotential height.

Explosive cyclones (ECs) occur frequently over the Japan Sea. The most rapidly intensifying EC over the Japan Sea during the 44-year period 1979–2022, in the cold season (October–April), was examined to reveal the variations in the key factors at different explosive development stages. The EC deepened at a maximum deepening rate of 3.07 bergerons and explosive development lasted for 15 h. At the initial moment of explosive development, the EC had distinctive low-level baroclinicity, the low-level water vapor convergence was weak, and mid-level cyclonic vorticity advection was far away from the EC’s center. At the moment at which the EC reached the maximum deepening rate, the low-level water vapor convergence and mid-level cyclonic vorticity advection increased distinctly and approached the EC’s center. A diagnostic analysis using the Zwack–Okossi equation showed that the main contributor to the initial explosive development was warm-air advection. Through the evolutionary process of the explosive development, the non-key factors of the cyclonic vorticity advection and diabatic heating at the initial explosive development stage increased quickly and became key factors contributing to the maximum explosive development. The key factors contributing to the explosive development varied with the stage of explosive development. The cross-section and vertical profile of each term suggested that the cyclonic vorticity advection was enhanced in the upper troposphere and diabatic heating increased in the middle troposphere.

Abstract. Simulations are conducted with a cloud-resolving numerical model to examine the transformation of a weak incipient mid-level cyclonic vortex into a tropical cyclone. Results demonstrate that two distinct pathways are possible and that development along a particular pathway is sensitive to model physics and initial conditions. One pathway involves a steady increase of the surface winds to tropical cyclone strength as the radius of maximum winds gradually decreases. A notable feature of this evolution is the creation of small-scale lower tropospheric cyclonic vorticity anomalies by deep convective towers and subsequent merger and convergence by the low-level secondary circulation. The second pathway also begins with a strengthening low-level circulation, but eventually a significantly stronger mid-level circulation develops. Cyclogenesis occurs subsequently when a small-scale surface concentrated vortex forms abruptly near the center of the larger-scale circulation. The small-scale vortex is warm core throughout the troposphere and results in a local surface pressure fall of a few millibars. It usually develops rapidly, undergoing a modest growth to form a small tropical cyclone. Many of the simulated systems approach or reach tropical cyclone strength prior to development of a prominent mid-level vortex so that the subsequent formation of a strong small-scale surface concentrated vortex in these cases could be considered intensification rather than genesis. Experiments are performed to investigate the dependence on the inclusion of the ice phase, radiation, the size and strength of the incipient mid-level vortex, the amount of moisture present in the initial vortex, and the sea surface temperature. Notably, as the sea surface temperature is raised, the likelihood of development along the second pathway is increased. This appears to be related to an increased production of ice. The sensitivity of the pathway taken to model physics and initial conditions revealed by these experiments raise the possibility that the solution to this initial value problem is near a bifurcation point. Future improvements to model parameterizations and more accurate observations of the transformation of disturbances to tropical cyclones should clarify the conditions that favor a particular pathway when starting from a mid-level vortex.

Abstract. Simulations are conducted with a cloud-resolving numerical model to examine the transformation of a weak incipient mid-level cyclonic vortex into a tropical cyclone. Results demonstrate that two distinct pathways are possible and that development along a particular pathway is sensitive to model physics and initial conditions. One pathway involves a steady increase of the surface winds to tropical cyclone strength as the radius of maximum winds gradually decreases. A notable feature of this evolution is the creation of small-scale lower tropospheric cyclonic vorticity anomalies by deep convective towers and subsequent merger and convergence by the low-level secondary circulation. The second pathway also begins with a strengthening low-level circulation, but eventually a significantly stronger mid-level circulation develops. Cyclogenesis occurs subsequently when a small-scale surface concentrated vortex forms abruptly near the center of the larger-scale circulation. The small-scale vortex is warm core throughout the troposphere and results in a fall in local surface pressure of a few millibars. It usually develops rapidly, undergoing a modest growth to form a small tropical cyclone. Many of the simulated systems approach or reach tropical cyclone strength prior to development of a prominent mid-level vortex so that the subsequent formation of a strong small-scale surface concentrated vortex in these cases could be considered intensification rather than genesis. Experiments are performed to investigate the dependence on the inclusion of the ice phase, radiation, the size and strength of the incipient mid-level vortex, the amount of moisture present in the initial vortex, and the sea surface temperature. Notably, as the sea surface temperature is raised, the likelihood of development along the second pathway is increased. This appears to be related to an increased production of ice. The sensitivity of the pathway taken to model physics and initial conditions revealed by these experiments raise the possibility that the solution to this initial value problem is near a bifurcation point. Future improvements to model parameterizations and more accurate observations of the transformation of disturbances to tropical cyclones should clarify the conditions that favor a particular pathway when starting from a mid-level vortex.