The Life Cycle of Indian Ocean Hotspots

2013 ◽  
pp. 91-103 ◽  
Author(s):  
Robert A. Duncan ◽  
Michael Storey
Keyword(s):  
Life Cycle ◽  
Indian Ocean

Indo-Pacific warm pool expansion modulates MJO lifecycle

2020 ◽  
Author(s):  
Panini Dasgupta ◽  
Roxy Mathew Koll ◽  
Michael J. McPhaden ◽  
Tamaki Suematsu ◽  
Chidong Zhang ◽  
...  
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
Southern Oscillation ◽  
Average Rate ◽  
Warm Pool ◽  
Dominant Mode ◽  
Maritime Continent ◽  
Pacific Warm Pool ◽  
The Indian Ocean ◽  
The Impact

<p>The Madden–Julian Oscillation (MJO) is the most dominant mode of intraseasonal<br>variability in the tropics, characterized by an eastward propagating zonal circulation pattern<br>and rain bands. MJO is very crucial phenomenon due to its interactions with other<br>timescales of ocean-atmosphere like El Niño Southern Oscillation, tropical cyclones,<br>monsoons, and the extreme rainfall events all across the globe. MJO events travel almost<br>half of the globe along the tropical oceans, majorly over the Indo-Pacific Warm Pool<br>(IPWP) region. This IPWP region has been warming during the twentieth and early twenty-<br>first centuries in response to increased anthropogenic emissions of greenhouse gases and<br>is projected to warm further. However, the impact of the warming of the IPWP region on<br>the MJO life cycle is largely unknown. Here we show that rapid warming over the IPWP<br>region during 1981–2018 has significantly changed the MJO life cycle, with its residence<br>time decreasing over the Indian Ocean by 3–4 days, and increasing over the Indo-Pacific<br>Maritime Continent by 5–6 days. We find that these changes in the MJO life cycle are<br>associated with a twofold expansion of the Indo-Pacific warm pool. The warm pool has<br>been expanding on average by 2.3 × 105 km2 per year during 1900–2018 and at an<br>accelerated average rate of 4 × 105 km2 per year during 1981–2018. The accelerated<br>warm pool expansion has increased moisture in the lower and middle troposphere over<br>IPWP and thereby increased the gradient of lower-middle tropospheric moisture between<br>the Indian Ocean and western Pacific. This zonal gradient of moisture between the Indian Ocean<br>and west Pacific and the increased subsidence over the Indian ocean due to increased<br>convective duration of MJO over maritime continent are likely the reasons behind the<br>changing lifecycle of MJO.</p>

scholarly journals The Intraseasonal Variability of the Indian Summer Monsoon Using TMI Sea Surface Temperatures and ECMWF Reanalysis

2008 ◽  
Vol 21 (11) ◽  
pp. 2519-2539 ◽  
Author(s):  
Nicholas P. Klingaman ◽  
Hilary Weller ◽  
Julia M. Slingo ◽  
Peter M. Inness
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
General Circulation ◽  
Function Analysis ◽  
Intraseasonal Variability ◽  
Equatorial Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Sst Anomalies

Abstract The northward-propagating intraseasonal (30–40 day) oscillation (NPISO) between active and break monsoon phases exerts a critical control on summer-season rainfall totals over India. Advances in diagnosing these events and comprehending the physical mechanisms behind them may hold the potential for improving their predictability. While previous studies have attempted to extract active and break events from reanalysis data to elucidate a composite life cycle, those studies have relied on first isolating the intraseasonal variability in the record (e.g., through bandpass filtering, removing harmonics, or empirical orthogonal function analysis). Additionally, the underlying physical processes that previous studies have proposed have varied, both among themselves and with studies using general circulation models. A simple index is defined for diagnosing NPISO events in observations and reanalysis, based on lag correlations between outgoing longwave radiation (OLR) over India and over the equatorial Indian Ocean. This index is the first to use unfiltered OLR observations and so does not specifically isolate intraseasonal periods. A composite NPISO life cycle based on this index is similar to previous composites in OLR and surface winds, demonstrating that the dominance of the intraseasonal variability in the monsoon climate system eliminates the need for more complex methods (e.g., time filtering or EOF analysis) to identify the NPISO. This study is also among the first to examine the NPISO using a long-period record of high-resolution sea surface temperatures (SSTs) from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager. Application of this index to those SSTs demonstrates that SST anomalies exist in near quadrature with convection, as suggested by recent coupled model studies. Analysis of the phase relationships between atmospheric fields and SSTs indicates that the atmosphere likely forced the SST anomalies. The results of this lag-correlation analysis suggest that the oscillation serves as its own most reliable—and perhaps only—predictor, and that signals preceding an NPISO event appear first over the Indian subcontinent, not the equatorial Indian Ocean where the events originate.

Evolution, Properties, and Spatial Variability of MJO Convection near and off the Equator during DYNAMO

2015 ◽  
Vol 72 (11) ◽  
pp. 4126-4147 ◽  
Author(s):  
Weixin Xu ◽  
Steven A. Rutledge ◽  
Courtney Schumacher ◽  
Masaki Katsumata
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
Spatial Variability ◽  
Deep Convection ◽  
Equatorial Indian Ocean ◽  
Zonal Winds ◽  
The North ◽  
Central Indian Ocean ◽  
Research And Teaching ◽  
Strong Upward Motion

Abstract This study investigates the evolution, structure, and spatial variability of Madden–Julian oscillation (MJO) convection observed during the 2011/12 Dynamics of the MJO (DYNAMO) field campaign. Generally, the C-band radars located in the near-equatorial Indian Ocean—Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) on Addu Atoll (Gan) and NASA TOGA on the R/V Roger Revelle (Revelle)—observed similar trends in echo-top heights, stratiform rain fraction, and precipitation feature size across the MJO life cycle. These trends are closely related to changes in mid- to upper-tropospheric moisture, sea surface temperature (SST), zonal wind, and diagnosed vertical air motions. However, the evolution of convection, moisture, and vertical air motion at the R/V Mirai (Mirai), located in the intertropical convergence zone (ITCZ) at 8°S, exhibited a pattern nearly opposite to Gan and Revelle. When the MJO was active over the equator, convection was suppressed around Mirai owing to induced subsidence by the strong upward motion to the north. SST and zonal winds near Mirai were nearly invariant across the MJO life cycle, indicating little influence from the MJO in these fields. Compared to Gan and Revelle, Mirai had a significant amount of precipitation that fell from shallow and isolated convection. There were subtle differences in the evolution and properties of the convection observed between Gan and Revelle. Deep convection occurred slightly earlier at Gan compared to Revelle, consistent with the west-to-east progression of the MJO in the central Indian Ocean. Furthermore, convective deepening was more gradual over Revelle compared to Gan, especially during the October MJO event.

scholarly journals Regional Heat Sources and the Active and Break Phases of Boreal Summer Intraseasonal (30–50 Day) Variability*

2005 ◽  
Vol 62 (8) ◽  
pp. 2726-2748 ◽  
Author(s):  
H. Annamalai ◽  
K. R. Sperber
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
Linear Model ◽  
Equatorial Indian Ocean ◽  
Boreal Summer ◽  
Heat Sources ◽  
West Pacific ◽  
Low Level ◽  
Cseof Analysis ◽  
Three Components

Abstract The boreal summer intraseasonal variability (BSISV) associated with the 30–50-day mode is represented by the coexistence of three components: poleward propagation of convection over the Indian and tropical west Pacific longitudes and eastward propagation along the equator. The hypothesis that the three components influence each other has been investigated using observed outgoing longwave radiation (OLR), NCEP–NCAR reanalysis, and solutions from an idealized linear model. The null hypothesis is that the three components are mutually independent. Cyclostationary EOF (CsEOF) analysis is applied on filtered OLR to extract the life cycle of the BSISV. The dominant CsEOF mode is significantly tied to the observed spatial rainfall pattern associated with the active/break phases over the Indian subcontinent. The components of the heating patterns from CsEOF analysis serve as prescribed forcings for the dry version of the linear model. This allows one to investigate the possible roles that the regional heat sources and sinks play in driving the large-scale monsoon circulation at various stages of the BSISV life cycle. To understand the interactive nature between convection and circulation, the moist version of the model is forced with intraseasonal SST anomalies. The linear models reproduce the major features of the BSISV seen in the reanalysis. The linear model suggests three new findings: (i) The circulation anomalies that develop as a Rossby wave response to suppressed convection over the equatorial Indian Ocean associated with the previous break phase of the BSISV results in low-level convergence and tropospheric moisture enhancement over the equatorial western Indian Ocean and helps trigger the next active phase of the BSISV. (ii) The development of convection over the tropical west Pacific forces descent anomalies to the west. This, in conjunction with the weakened cross-equatorial flow due to suppressed convective anomalies over the equatorial Indian Ocean, reduces the tropospheric moisture over the Arabian Sea and promotes westerly wind anomalies that do not recurve over India. As a result the low-level cyclonic vorticity shifts from India to Southeast Asia and break conditions are initiated over India. (iii) The circulation anomalies forced by equatorial Indian Ocean convective anomalies significantly influence the active/break phases over the tropical west Pacific. The model solutions support the hypothesis that the three components of the BSISV influence each other but do not imply that such an influence is responsible for the space–time evolution of the BSISV. Further, the applicability of the model results to the observed system is constrained by the assumption that linear interactions are sufficient to address the BSISV and that air–sea interaction and transient forcing are excluded.

Ultrastructural analysis of “Sensory” surface nerve endings and “putative” neurotransmitter sites in Schistosoma mansoni Miracidia

1989 ◽  
Vol 47 ◽  
pp. 962-963
Author(s):  
Betty Ruth Jones ◽  
Steve Chi-Tang Pan
Keyword(s):  
Nervous System ◽  
Life Cycle ◽  
Schistosoma Mansoni ◽  
Snail Host ◽  
Complex Life Cycle ◽  
Rational Approach ◽  
Effective Control ◽  
The Social ◽  
Social And Economic Development ◽  
Basic Biology

INTRODUCTION: Schistosomiasis has been described as “one of the most devastating diseases of mankind, second only to malaria in its deleterious effects on the social and economic development of populations in many warm areas of the world.” The disease is worldwide and is probably spreading faster and becoming more intense than the overall research efforts designed to provide the basis for countering it. Moreover, there are indications that the development of water resources and the demands for increasing cultivation and food in developing countries may prevent adequate control of the disease and thus the number of infections are increasing.Our knowledge of the basic biology of the parasites causing the disease is far from adequate. Such knowledge is essential if we are to develop a rational approach to the effective control of human schistosomiasis. The miracidium is the first infective stage in the complex life cycle of schistosomes. The future of the entire life cycle depends on the capacity and ability of this organism to locate and enter a suitable snail host for further development, Little is known about the nervous system of the miracidium of Schistosoma mansoni and of other trematodes. Studies indicate that miracidia contain a well developed and complex nervous system that may aid the larvae in locating and entering a susceptible snail host (Wilson, 1970; Brooker, 1972; Chernin, 1974; Pan, 1980; Mehlhorn, 1988; and Jones, 1987-1988).

A freeze-fracture-etched study of the physarum polycephalum plasma membrane during early formation of the macroplasmodial stage

1993 ◽  
Vol 51 ◽  
pp. 346-347
Author(s):  
Randolph W. Taylor ◽  
Henrie Treadwell
Keyword(s):  
Plasma Membrane ◽  
Life Cycle ◽  
Growth Phase ◽  
Filter Paper ◽  
Physarum Polycephalum ◽  
Freeze Fracture ◽  
Petri Dish ◽  
Wire Screen ◽  
Wide Mouth ◽  
Sterile Filter

The plasma membrane of the Slime Mold, Physarum polycephalum, process unique morphological distinctions at different stages of the life cycle. Investigations of the plasma membrane of P. polycephalum, particularly, the arrangements of the intramembranous particles has provided useful information concerning possible changes occurring in higher organisms. In this report Freeze-fracture-etched techniques were used to investigate 3 hours post-fusion of the macroplasmodia stage of the P. polycephalum plasma membrane.Microplasmodia of Physarum polycephalum (M3C), axenically maintained, were collected in mid-expotential growth phase by centrifugation. Aliquots of microplasmodia were spread in 3 cm circles with a wide mouth pipette onto sterile filter paper which was supported on a wire screen contained in a petri dish. The cells were starved for 2 hrs at 24°C. After starvation, the cells were feed semidefined medium supplemented with hemin and incubated at 24°C. Three hours after incubation, samples were collected randomly from the petri plates, placed in plancettes and frozen with a propane-nitrogen jet freezer.

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