scholarly journals Cirrus optical properties observed with lidar, radiosonde, and satellite over the tropical Indian Ocean during the aerosol-polluted northeast and clean maritime southwest monsoon

2007 ◽  
Vol 112 (D17) ◽  
Author(s):  
P. Seifert ◽  
A. Ansmann ◽  
D. Müller ◽  
U. Wandinger ◽  
D. Althausen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Southwest Monsoon

Do dragonflies migrate across the western Indian Ocean?

2009 ◽  
Vol 25 (4) ◽  
pp. 347-358 ◽  
Author(s):  
R. Charles Anderson
Keyword(s):  
Indian Ocean ◽  
Return Migration ◽  
Bird Species ◽  
Tropical Indian Ocean ◽  
Western Indian Ocean ◽  
Southwest Monsoon ◽  
Inter Tropical Convergence Zone ◽  
Arrival Dates ◽  
Pantala Flavescens ◽  
Do So

Abstract:In the tropical Indian Ocean, the Maldive Islands lack surface freshwater, so are unsuitable for dragonfly reproduction. Nevertheless, millions of dragonflies (Insecta, Odonata; mostly globe skimmer, Pantala flavescens) appear suddenly every year starting in October. Arrival dates in the Maldives and India demonstrate that the dragonflies travel from southern India, a distance of some 500–1000 km. Dates of arrival and occurrence coincide with the southward passage of the Inter-tropical Convergence Zone (ITCZ). Circumstantial evidence suggests that the dragonflies fly with north-easterly tail winds, within and behind the ITCZ, at altitudes over 1000 m. It is proposed that this massive movement of dragonflies is part of an annual migration across the western Indian Ocean from India to East Africa. Arrival dates in the Seychelles support this hypothesis. Dragonflies also appear (in smaller numbers) in the Maldives in May, with the onset of the southwest monsoon, suggesting a possible return migration from Africa. These proposed migrations of dragonflies, regularly crossing 3500 km or more of open ocean, were previously unknown. It is known that these dragonflies exploit ephemeral rain pools for reproduction; the monsoons and ITCZ bring not only alternating, seasonal rains to India and Africa, but also appropriate winds for dragonflies to follow those rains. Several bird species migrate from India across the western Indian Ocean to wintering grounds in Africa. They do so at the same time as the dragonflies, presumably taking advantage of the same seasonal tail winds. Many of these birds also eat dragonflies; the possible significance of this was not previously appreciated.

scholarly journals Influences of Seasonal Monsoons on the Taxonomic Composition and Diversity of Bacterial Community in the Eastern Tropical Indian Ocean

2021 ◽  
Vol 11 ◽  
Author(s):  
Ping Gao ◽  
Guangxun Du ◽  
Duo Zhao ◽  
Qinsheng Wei ◽  
Xuelei Zhang ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Indian Ocean ◽  
Bacterial Community ◽  
Environmental Changes ◽  
Tropical Indian Ocean ◽  
Southwest Monsoon ◽  
Gene Profiling ◽  
Rrna Gene ◽  
Northeast Monsoon ◽  
Vertical Variation

The Indian Ocean is characterized by its complex physical systems and strong seasonal monsoons. To better understand effects of seasonal monsoon-driven circulation on the bacterioplanktonic community structure in surface waters and the bacterial distribution response to vertical stratification, patterns of seasonal, and vertical distribution of bacterial communities in the Eastern Tropical Indian Ocean were investigated using 16S rRNA gene profiling. Water samples were collected during the Southwest monsoon (from June to August), the fall inter-monsoon (from October and November) and the Northeast monsoon (from December to January), respectively, onboard during three cruises from July 2016 to January 2018. Surface bacterioplankton communities in these three seasons and in the upper water (3–300 m with six depths) during the Northeast monsoon contained a diverse group of taxa, mainly Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes, and Chloroflexi. Redundancy discriminant analysis (RDA) uncovered that temperature, salinity, and dissolved oxygen (DO) were crucial environmental parameters that affected the structure of bacterial community in overall surface samples. However, significant differences in the composition of the bacterial community are likely due to changes in concentrations of salinity during the fall inter-monsoon, while phosphate for both the Southwest monsoon and the Northeast monsoon. Pearson's analysis revealed that the seasonal variation rather than the vertical variation of environmental factors had a more significant impact on the composition of bacterial community. In addition, a clear seasonal pattern of bacterial co-occurrence showed that inter-taxa associations during the fall inter-monsoon were closer than during the Northeast monsoon and the Southwest monsoon. Overall, our results implied clear differences in the composition of bacterial community, with more pronounced seasonal variation compared to the vertical variation in response to environmental changes.

Vertical distribution of bigeye tuna Thunnus obesus in the tropical Indian Ocean

2013 ◽  
Vol 20 (3) ◽  
pp. 660-671 ◽  
Author(s):  
Xuezhong CHEN ◽  
Shenglong YANG ◽  
Yu Zhang ◽  
Wei FAN ◽  
Yumei WU
Keyword(s):  
Indian Ocean ◽  
Vertical Distribution ◽  
Tropical Indian Ocean ◽  
Bigeye Tuna ◽  
Thunnus Obesus

Interannual variability of the Tropical Indian Ocean mixed layer depth

2012 ◽  
Vol 40 (3-4) ◽  
pp. 743-759 ◽  
Author(s):  
M. G. Keerthi ◽  
M. Lengaigne ◽  
J. Vialard ◽  
C. de Boyer Montégut ◽  
P. M. Muraleedharan
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Ocean Mixed Layer Depth

Assessment of mass-induced sea level variability in the Tropical Indian Ocean based on GRACE and altimeter observations

2021 ◽  
Vol 95 (2) ◽  
Author(s):  
Shiva Shankar Manche ◽  
Rabindra K. Nayak ◽  
Prakash Chandra Mohanty ◽  
M. V. R. Shesasai ◽  
V. K. Dadhwal
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Tropical Indian Ocean ◽  
Sea Level Variability

scholarly journals Seasonality and Dynamics of Atmospheric Teleconnection from the Tropical Indian Ocean and the Western Pacific to West Antarctica

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 849
Author(s):  
Hyun-Ju Lee ◽  
Emilia-Kyung Jin
Keyword(s):  
Indian Ocean ◽  
Rossby Wave ◽  
Tropical Indian Ocean ◽  
Western Pacific ◽  
Tropical Region ◽  
Formation Mechanisms ◽  
West Antarctica ◽  
Background Flow ◽  
The Impact ◽  
The Western Pacific

The global impact of the tropical Indian Ocean and the Western Pacific (IOWP) is expected to increase in the future because this area has been continuously warming due to global warming; however, the impact of the IOWP forcing on West Antarctica has not been clearly revealed. Recently, ice loss in West Antarctica has been accelerated due to the basal melting of ice shelves. This study examines the characteristics and formation mechanisms of the teleconnection between the IOWP and West Antarctica for each season using the Rossby wave theory. To explicitly understand the role of the background flow in the teleconnection process, we conduct linear baroclinic model (LBM) simulations in which the background flow is initialized differently depending on the season. During JJA/SON, the barotropic Rossby wave generated by the IOWP forcing propagates into the Southern Hemisphere through the climatological northerly wind and arrives in West Antarctica; meanwhile, during DJF/MAM, the wave can hardly penetrate the tropical region. This indicates that during the Austral winter and spring, the IOWP forcing and IOWP-region variabilities such as the Indian Ocean Dipole (IOD) and Indian Ocean Basin (IOB) modes should paid more attention to in order to investigate the ice change in West Antarctica.

Sign in / Sign up

Export Citation Format

Share Document