This study reveals the barotropic dynamics associated with the formation and growth of tropical cyclone Nargis in 2008,during its formation stage.Strong equatorial westerlies occurred over the southern Bay of Bengal i...This study reveals the barotropic dynamics associated with the formation and growth of tropical cyclone Nargis in 2008,during its formation stage.Strong equatorial westerlies occurred over the southern Bay of Bengal in association with the arrival of an intraseasonal westerly event during the period 22-24 April 2008. The westerlies,together with strong tropical-subtropical easterlies,constituted a large-scale horizontal shear flow,creating cyclonic vorticity and thereby promoting the incipient disturbance that eventually evolved into Nargis.This basic zonal flow in the lower troposphere was barotropically unstable,with the amplified disturbance gaining more kinetic energy from the easterly jet than from the westerly jet during 25-26 April. This finding suggests that more attention should be paid to the unstable easterly jet when monitoring and predicting the development of tropical cyclones.Energetics analyses reveal that barotropic energy conversion by the meridional gradient of the basic zonal flow was indeed an important energy source for the growth of Nargis.展开更多
Tropical and subtropical evergreen broad-leaved forests(EBFs)and needle-leaved forests(ENFs)in China exhibit complex leaf shedding strategies in responses to soil water availability,vapor pressure deficits(VPDs)and su...Tropical and subtropical evergreen broad-leaved forests(EBFs)and needle-leaved forests(ENFs)in China exhibit complex leaf shedding strategies in responses to soil water availability,vapor pressure deficits(VPDs)and sunlight availability.However,the seasonal variations and triggers of litterfall differ significantly in tropical/subtropical forests,and there are still many uncertainties.Herein,we aim to explore the distinct climatic factors of seasonal litterfall in a climate–phenology correlation framework.We collected seasonal litterfall data from 85 sites across tropical/subtropical China and used linear correlation coefficients between sunlight and rainfall to partition synchronous/asynchronous climates.Additional phase analysis and structural equation model analysis were conducted to model the climatic triggers of tropical phenology.Results indicated two types of tropical litterfall phenology under two types of climates.In synchronous climates,where seasonal sunlight and rainfall are positively correlated,the litterfall peak of the unimodal phenology and the first litterfall peak of the bimodal phenology both happen at the end of dry season.The second litterfall peak of the bimodal phenology occurs at the end of rainy season due to water stress.In asynchronous climates,where seasonal sunlight and rainfall are negatively correlated,VPD shows consistent seasonal variations with incoming sunlight.The leaf senescence is accelerated at the end of dry season by higher VPD;while soil water deficit is in anti-phase with sunlight and mainly controls the second litterfall peak of the bimodal phenology in EBF.Our findings provide an important reference for modeling tropical phenology in Earth system models.展开更多
The increase of total organic carbon content of the late Oligocene-early Miocene terrigenously-dominated marine shales in the shallower depth intervals was reported in the Ying-Qiong Basin,South China Sea.The organic ...The increase of total organic carbon content of the late Oligocene-early Miocene terrigenously-dominated marine shales in the shallower depth intervals was reported in the Ying-Qiong Basin,South China Sea.The organic enriched lower Sanya Formation shales(early Miocene)have biomarker characteristics of tropical/subtropical plants,with abundant high molecular weight n-alkanes,angiosperm-derived oleanane,rearranged oleananesⅠ,Ⅱ,Ⅱ,tricyclic/tetracyclic terpanes including des-A-oleanane,X,*,Y,Z,Z1 and bicadinanes W,T,T1,R.The biomarker characteristics are suggestive of larger influx of the dominant tropical/subtropical angiosperms in flora under a warming and more humid climate during depositions of the lower Sanya Formation(early Miocene)than the older Lingshui Formation(late Oligocene).The tropical/subtropical angiosperm input was thought as the prime control of terrigenous organic matter enrichment relative to the redox condition,and the coeval sea level changes and seafloor spreading in the South China Sea.Enrichment of the terrigenous organic matter in the early Miocene shales is likely in association with the coeval peak East Asian summer monsoon intensity in the South China Sea.展开更多
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-Q11-04)the National Basic Research Program of China(2010CB950401)the National Natural Science Foundation of China(Grant Nos. 40975052,40875034,and 40821092).
文摘This study reveals the barotropic dynamics associated with the formation and growth of tropical cyclone Nargis in 2008,during its formation stage.Strong equatorial westerlies occurred over the southern Bay of Bengal in association with the arrival of an intraseasonal westerly event during the period 22-24 April 2008. The westerlies,together with strong tropical-subtropical easterlies,constituted a large-scale horizontal shear flow,creating cyclonic vorticity and thereby promoting the incipient disturbance that eventually evolved into Nargis.This basic zonal flow in the lower troposphere was barotropically unstable,with the amplified disturbance gaining more kinetic energy from the easterly jet than from the westerly jet during 25-26 April. This finding suggests that more attention should be paid to the unstable easterly jet when monitoring and predicting the development of tropical cyclones.Energetics analyses reveal that barotropic energy conversion by the meridional gradient of the basic zonal flow was indeed an important energy source for the growth of Nargis.
基金supported by the National Natural Science Foundation of China(grant numbers 31971458 and 41971275)Special High-Level Plan Project of Guangdong Province(grant number 2016TQ03Z354)+1 种基金Forestry Science and Technology Innovation Project of Guangdong Province(grant number 2021KJCX003)‘GDAS’Project of Science and Technology Development(grant numbers 2020GDASYL-20200302001,2020GDASYL-20200102002).
文摘Tropical and subtropical evergreen broad-leaved forests(EBFs)and needle-leaved forests(ENFs)in China exhibit complex leaf shedding strategies in responses to soil water availability,vapor pressure deficits(VPDs)and sunlight availability.However,the seasonal variations and triggers of litterfall differ significantly in tropical/subtropical forests,and there are still many uncertainties.Herein,we aim to explore the distinct climatic factors of seasonal litterfall in a climate–phenology correlation framework.We collected seasonal litterfall data from 85 sites across tropical/subtropical China and used linear correlation coefficients between sunlight and rainfall to partition synchronous/asynchronous climates.Additional phase analysis and structural equation model analysis were conducted to model the climatic triggers of tropical phenology.Results indicated two types of tropical litterfall phenology under two types of climates.In synchronous climates,where seasonal sunlight and rainfall are positively correlated,the litterfall peak of the unimodal phenology and the first litterfall peak of the bimodal phenology both happen at the end of dry season.The second litterfall peak of the bimodal phenology occurs at the end of rainy season due to water stress.In asynchronous climates,where seasonal sunlight and rainfall are negatively correlated,VPD shows consistent seasonal variations with incoming sunlight.The leaf senescence is accelerated at the end of dry season by higher VPD;while soil water deficit is in anti-phase with sunlight and mainly controls the second litterfall peak of the bimodal phenology in EBF.Our findings provide an important reference for modeling tropical phenology in Earth system models.
基金The National Natural Science Foundation of China under contract No.42202184the National Science and Technology Major Project under contract No.2016ZX05026。
文摘The increase of total organic carbon content of the late Oligocene-early Miocene terrigenously-dominated marine shales in the shallower depth intervals was reported in the Ying-Qiong Basin,South China Sea.The organic enriched lower Sanya Formation shales(early Miocene)have biomarker characteristics of tropical/subtropical plants,with abundant high molecular weight n-alkanes,angiosperm-derived oleanane,rearranged oleananesⅠ,Ⅱ,Ⅱ,tricyclic/tetracyclic terpanes including des-A-oleanane,X,*,Y,Z,Z1 and bicadinanes W,T,T1,R.The biomarker characteristics are suggestive of larger influx of the dominant tropical/subtropical angiosperms in flora under a warming and more humid climate during depositions of the lower Sanya Formation(early Miocene)than the older Lingshui Formation(late Oligocene).The tropical/subtropical angiosperm input was thought as the prime control of terrigenous organic matter enrichment relative to the redox condition,and the coeval sea level changes and seafloor spreading in the South China Sea.Enrichment of the terrigenous organic matter in the early Miocene shales is likely in association with the coeval peak East Asian summer monsoon intensity in the South China Sea.
