After compositing three representative ENSO indices,El Nio events have been divided into an eastern pattern(EP) and a central pattern(CP).By using EOF,correlation and composite analysis,the relationship and possible m...After compositing three representative ENSO indices,El Nio events have been divided into an eastern pattern(EP) and a central pattern(CP).By using EOF,correlation and composite analysis,the relationship and possible mechanisms between Indian Ocean Dipole(IOD) and two types of El Nio were investigated.IOD events,originating from Indo-Pacific scale air-sea interaction,are composed of two modes,which are associated with EP and CP El Ni o respectively.The IOD mode related to EP El Nio events(named as IOD1) is strongest at the depth of 50 to 150 m along the equatorial Indian Ocean.Besides,it shows a quasi-symmetric distribution,stronger in the south of the Equator.The IOD mode associated with CP El Nio(named as IOD2) has strongest signal in tropical southern Indian Ocean surface.In terms of mechanisms,before EP El Nio peaks,anomalous Walker circulation produces strong anomalous easterlies in equatorial Indian Ocean,resulting in upwelling in the east,decreasing sea temperature there;a couple of anomalous anticyclones(stronger in the south) form off the Equator where warm water accumulates,and thus the IOD1 occurs.When CP El Nio develops,anomalous Walker circulation is weaker and shifts its center to the west,therefore anomalous easterlies in equatorial Indian Ocean is less strong.Besides,the anticyclone south of Sumatra strengthens,and the southerlies east of it bring cold water from higher latitudes and northerlies west of it bring warm water from lower latitudes to the 15° to 25°S zone.Meanwhile,there exists strong divergence in the east and convergence in the west part of tropical southern Indian Ocean,making sea temperature fall and rise separately.Therefore,IOD2 lies farther south.展开更多
Horticultural practice in the Himalayas has great importance not only for economic development but also for environmental restoration. In the entire Himalayan mountain system, from Jammu and Kashmir Himalaya to Assam ...Horticultural practice in the Himalayas has great importance not only for economic development but also for environmental restoration. In the entire Himalayan mountain system, from Jammu and Kashmir Himalaya to Assam Himalaya, the practice of horticulture is centuries old, which includes varieties of fruits along with availability of high quality and quantity. In terms of the Alaknanda Basin, which is centrally located in the Himalayan system, the practice of horticulture does not get commercial level; only it is cultivated domestically. The climatic conditions ranging from sub-tropical (low-lying river valleys) to alpine and frigid (highly elevated regions) are suited for varieties of fruit cultivation, yet the benefit of this could not be utilized by the residents who are working in the agricultural fields. Besides, less proportion of land is devoted for fruit cultivation along with domestic production of fruits. The varieties of fruit cultivated in the basin range from mango-guava-papaya, stone-net, citrus to apple at the different elevations. Along with the cultivated fruits, varieties of wild fruits are also found in the jungle. There are four climatic zones suitable for the production of various fruits as below:? Sub-tropical zone including the lower part of the Alaknanda, Pindar, Nandakini, and Mandakini rivers is suitable for mango, guava, and papaya; ? Sub-temperate zone in the middle basin of the Alaknanda, Pindar, Nandakini and Mandakini rivers is a good place for citrus fruits, particularly orange and lemon; ? Temperate zone occupying the Dauli, Vishnu Ganga, Upper Pinder, Nandakini and Mandakini rivers is highly productive for apple, nut and stone fruits; ? Alpine meadows in the highly elevated region are known as Bugyal famous for herb culture. Each of these zones has distinct physical features, environmental conditions and socio-economic identity for fruit cultivation. The present paper aims to discuss about the vertical zonation of the horticultural farming and its nature, in terms of development, in the Alaknada Basin.展开更多
As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared...As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared. The DCC intensity and area varies more significantly in the Indian Ocean than the western Pacific sector, while the DCC frequency is comparable in both sectors at the seasonal scale. Although the Indian Ocean sector is strongly dominated by the seasonal evolution, the interannual variations in the two sectors are comparable for all three DCC properties(frequency, intensity, and area). Besides,Walker circulation is closely correlated with the interannual variability of DCCs in both sectors. The Walker circulation strengthens(weakens) as the DCCs shift eastward(westward) over the Indian Ocean sector and westward(eastward) over the western Pacific sector. When more or stronger DCCs occur over the Indian Ocean sector(western Pacific sector), the Walker circulation becomes stronger(weaker) and shifts westward(eastward). Interestingly, the response of the Walker circulation to DCC variability over the warm pool is asymmetry. The asymmetry response of the Walker circulation to the negative and positive DCC anomaly may be related to the non-linearity internal variability of the atmosphere. DCCs over the Indian Ocean sector have a much weaker nonlinear correlation with the Walker circulation than DCCs over the western Pacific sector.展开更多
基金National Key Basic Research Program of China(973 Program,2012CB417403)
文摘After compositing three representative ENSO indices,El Nio events have been divided into an eastern pattern(EP) and a central pattern(CP).By using EOF,correlation and composite analysis,the relationship and possible mechanisms between Indian Ocean Dipole(IOD) and two types of El Nio were investigated.IOD events,originating from Indo-Pacific scale air-sea interaction,are composed of two modes,which are associated with EP and CP El Ni o respectively.The IOD mode related to EP El Nio events(named as IOD1) is strongest at the depth of 50 to 150 m along the equatorial Indian Ocean.Besides,it shows a quasi-symmetric distribution,stronger in the south of the Equator.The IOD mode associated with CP El Nio(named as IOD2) has strongest signal in tropical southern Indian Ocean surface.In terms of mechanisms,before EP El Nio peaks,anomalous Walker circulation produces strong anomalous easterlies in equatorial Indian Ocean,resulting in upwelling in the east,decreasing sea temperature there;a couple of anomalous anticyclones(stronger in the south) form off the Equator where warm water accumulates,and thus the IOD1 occurs.When CP El Nio develops,anomalous Walker circulation is weaker and shifts its center to the west,therefore anomalous easterlies in equatorial Indian Ocean is less strong.Besides,the anticyclone south of Sumatra strengthens,and the southerlies east of it bring cold water from higher latitudes and northerlies west of it bring warm water from lower latitudes to the 15° to 25°S zone.Meanwhile,there exists strong divergence in the east and convergence in the west part of tropical southern Indian Ocean,making sea temperature fall and rise separately.Therefore,IOD2 lies farther south.
文摘Horticultural practice in the Himalayas has great importance not only for economic development but also for environmental restoration. In the entire Himalayan mountain system, from Jammu and Kashmir Himalaya to Assam Himalaya, the practice of horticulture is centuries old, which includes varieties of fruits along with availability of high quality and quantity. In terms of the Alaknanda Basin, which is centrally located in the Himalayan system, the practice of horticulture does not get commercial level; only it is cultivated domestically. The climatic conditions ranging from sub-tropical (low-lying river valleys) to alpine and frigid (highly elevated regions) are suited for varieties of fruit cultivation, yet the benefit of this could not be utilized by the residents who are working in the agricultural fields. Besides, less proportion of land is devoted for fruit cultivation along with domestic production of fruits. The varieties of fruit cultivated in the basin range from mango-guava-papaya, stone-net, citrus to apple at the different elevations. Along with the cultivated fruits, varieties of wild fruits are also found in the jungle. There are four climatic zones suitable for the production of various fruits as below:? Sub-tropical zone including the lower part of the Alaknanda, Pindar, Nandakini, and Mandakini rivers is suitable for mango, guava, and papaya; ? Sub-temperate zone in the middle basin of the Alaknanda, Pindar, Nandakini and Mandakini rivers is a good place for citrus fruits, particularly orange and lemon; ? Temperate zone occupying the Dauli, Vishnu Ganga, Upper Pinder, Nandakini and Mandakini rivers is highly productive for apple, nut and stone fruits; ? Alpine meadows in the highly elevated region are known as Bugyal famous for herb culture. Each of these zones has distinct physical features, environmental conditions and socio-economic identity for fruit cultivation. The present paper aims to discuss about the vertical zonation of the horticultural farming and its nature, in terms of development, in the Alaknada Basin.
基金supported by the National Natural Science Foundation of China (Grants Nos. 91637208 & 41405146)the Key Project of Science Foundation of Yunnan Province (Grant No. 2016FA041)the Key Research Program of Frontier Sciences of CAS (Grant No. QYZDB-SSW-DQC2017)
文摘As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared. The DCC intensity and area varies more significantly in the Indian Ocean than the western Pacific sector, while the DCC frequency is comparable in both sectors at the seasonal scale. Although the Indian Ocean sector is strongly dominated by the seasonal evolution, the interannual variations in the two sectors are comparable for all three DCC properties(frequency, intensity, and area). Besides,Walker circulation is closely correlated with the interannual variability of DCCs in both sectors. The Walker circulation strengthens(weakens) as the DCCs shift eastward(westward) over the Indian Ocean sector and westward(eastward) over the western Pacific sector. When more or stronger DCCs occur over the Indian Ocean sector(western Pacific sector), the Walker circulation becomes stronger(weaker) and shifts westward(eastward). Interestingly, the response of the Walker circulation to DCC variability over the warm pool is asymmetry. The asymmetry response of the Walker circulation to the negative and positive DCC anomaly may be related to the non-linearity internal variability of the atmosphere. DCCs over the Indian Ocean sector have a much weaker nonlinear correlation with the Walker circulation than DCCs over the western Pacific sector.