Analysis Of The Differences Between The Tropical Low Pressure In The Bay Of Bengal Region And The Storm Intensity In The Bay Of Bengal

In the Bay of Bengal,the Bay of Bengal storm and tropical low-pressure activities are similar in scope and cover almost the entire year.From the perspective of tropical cyclones,both of them belong to the cyclonic low-pressure system.The two systems are only the difference in intensity.Why is there a difference in the frequency of activity between the two seasons?What is the cause of the monsoon depression during the prevailing period of the Indian monsoon(June to September)?These issues relate to the role of seasonal changes in sea temperature and atmospheric circulation in promoting or restricting the development of tropical cyclones.In this paper,the GPI index is used to analyze the sea surface temperature(SST),high and low vertical shear,middle and low humidity and low layer absolute vorticity at different stages of cyclone generation.(1)Sea surface temperature(SST):The sea surface temperature above 27 ? is conducive to the formation of tropical cyclone TC.(2)Relative humidity of 700hPa:Relative humidity of 700hPa.From the average field,the relative humidity can generate tropical cyclones when the relative humidity is greater than 60%.With a large increase,the relative humidity of TS at 700hpa is basically higher than 75%,so the larger relative humidity of 700hPa is conducive to the development of tropical cyclones.(3)Vertical velocity:Using the defined vertical velocity,it is one of the important factors distinguishing the storm of the Bay of Bengal storm and the low-pressure TD of the monsoon.The scattered situation is basically the same,but the phase difference ratio is increased at different stages.Only a small(5?15m·s-1)is beneficial to the development of TS,but for monsoon low voltage TD,larger(greater than 20m·s-1)A TD can be generated.(4)Low-level disturbance:low-level disturbance includes low-level heat,momentum and Coriolis force,heat is mainly related to sea surface temperature SST;momentum problem is related to low-level convergence and accumulation and high-level divergence,and it is found that there is a large accumulation in wind field.When the low-level convergence and the high-level divergence match are more suitable,it is more conducive to the formation of tropical cyclone TC.The Ekman suction phenomenon is too small,so that the development strength of TC is not strong,but the TC structure collapses when it is too large.The bias is related to latitude and is also affected by the terrain.