The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a lar...The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a large groups and mass migrations during which significant crop loss and food security issues may occur. Currently, the most recent upsurge of desert locust is prevailing across Eastern Africa and Southwestern Asia. Usually desert locusts are restricted to regions like semi-arid and arid regions. A super cyclonic storm, namely Amphan originated during May 2020, in the Bay of Bengal of North Indian Ocean has influenced numerous swarms to migrate from the Thar desert region to other parts of India. In this research, satellite data were used to investigate the reasons for this sudden swarm migration. The results that revealed the wind jets passing above the Thar desert region have integrated with the cyclogenesis of Amphan and led to the formation of conduits. The favorable conditions in the conduits include the open sky conditions, air temperature and fresh vegetation availability. Moreover, the wind settings in the conduits have enabled the swarm migrate to follow the downwind facing the sunrays during early mornings for an easy and successful take-off. It is observed that during the take-off session the wind speed at 850 hPa pressure level is mostly double than that of surface wind in both the conduits.展开更多
Tropical cyclones are intense weather systems that originate over warm tropical oceans and they alter the dynamical,chemical,and biological state of the oceans.Here,the reasons for the rapid intensification of Super c...Tropical cyclones are intense weather systems that originate over warm tropical oceans and they alter the dynamical,chemical,and biological state of the oceans.Here,the reasons for the rapid intensification of Super cyclone Amphan that occurred in May 2020 in the Bay of Bengal(BoB)are thoroughly investigated.One of the main causes for the intensification of Amphan into a super cyclone is the rise in sea surface temperature(SST).Additionally,the warm-core eddies present in the track of cyclones also contributed to its rapid intensification.The Tropical Cyclone Heat Potential(TCHP)and Upper Ocean Heat Content(OHC)were consistent and remained high throughout the cyclone period to maintain its high intensity.Although there were greater cyclone-induced cold wakes during the period,the background SST conditions were still higher and were favourable for the cyclone to intensify further.The vertical wind shear in both shallow and deep layers was minimal,which further helped the formation of a stable and strong cyclonic vortex,and thus contributed to its rapid intensification.The behaviour of cyclone Amphan in future scenarios is analysed using a coupled atmosphere-ocean model.Compared to the current scenario,the severity of cyclones is expected to increase in the future(RCP 8.5).Early landfall is observed in the case of RCP 4.5.As a result of elevated UOHC,Amphan attains more strength in the RCP 8.5 than it does in the present scenario.The translational speed increases in the future,which makes the cyclone move faster.Due to the passage of Amphan,there is a reduction in UOHC,which is higher in the case of a future warm climate.This suggests that additional energy from the ocean is transferred to the atmosphere,causing the cyclone to intensify further.According to the results from the coupled atmosphere-ocean model,the future warm atmospheric and oceanic conditions will be more favourable for the genesis and development of stronger cyclones.展开更多
文摘The desert locust, <em>Schistocerca gregaria</em> Forsk. (Orthoptera: Acrididae) is a peculiar insect that exhibits density-dependent phase polyphenism. Gregarious phase enables desert locust to form a large groups and mass migrations during which significant crop loss and food security issues may occur. Currently, the most recent upsurge of desert locust is prevailing across Eastern Africa and Southwestern Asia. Usually desert locusts are restricted to regions like semi-arid and arid regions. A super cyclonic storm, namely Amphan originated during May 2020, in the Bay of Bengal of North Indian Ocean has influenced numerous swarms to migrate from the Thar desert region to other parts of India. In this research, satellite data were used to investigate the reasons for this sudden swarm migration. The results that revealed the wind jets passing above the Thar desert region have integrated with the cyclogenesis of Amphan and led to the formation of conduits. The favorable conditions in the conduits include the open sky conditions, air temperature and fresh vegetation availability. Moreover, the wind settings in the conduits have enabled the swarm migrate to follow the downwind facing the sunrays during early mornings for an easy and successful take-off. It is observed that during the take-off session the wind speed at 850 hPa pressure level is mostly double than that of surface wind in both the conduits.
文摘Tropical cyclones are intense weather systems that originate over warm tropical oceans and they alter the dynamical,chemical,and biological state of the oceans.Here,the reasons for the rapid intensification of Super cyclone Amphan that occurred in May 2020 in the Bay of Bengal(BoB)are thoroughly investigated.One of the main causes for the intensification of Amphan into a super cyclone is the rise in sea surface temperature(SST).Additionally,the warm-core eddies present in the track of cyclones also contributed to its rapid intensification.The Tropical Cyclone Heat Potential(TCHP)and Upper Ocean Heat Content(OHC)were consistent and remained high throughout the cyclone period to maintain its high intensity.Although there were greater cyclone-induced cold wakes during the period,the background SST conditions were still higher and were favourable for the cyclone to intensify further.The vertical wind shear in both shallow and deep layers was minimal,which further helped the formation of a stable and strong cyclonic vortex,and thus contributed to its rapid intensification.The behaviour of cyclone Amphan in future scenarios is analysed using a coupled atmosphere-ocean model.Compared to the current scenario,the severity of cyclones is expected to increase in the future(RCP 8.5).Early landfall is observed in the case of RCP 4.5.As a result of elevated UOHC,Amphan attains more strength in the RCP 8.5 than it does in the present scenario.The translational speed increases in the future,which makes the cyclone move faster.Due to the passage of Amphan,there is a reduction in UOHC,which is higher in the case of a future warm climate.This suggests that additional energy from the ocean is transferred to the atmosphere,causing the cyclone to intensify further.According to the results from the coupled atmosphere-ocean model,the future warm atmospheric and oceanic conditions will be more favourable for the genesis and development of stronger cyclones.
