The North Equatorial Countercurrent and the Zonality of the Intertropical Convergence Zone

2021 ◽  
Author(s):  
Zhikuo Sun ◽  
Jianhua Lu
Keyword(s):  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
The North

scholarly journals An Intertropical Convergence Zone shift controlled the terrestrial material supply on the Ninetyeast Ridge

2021 ◽  
Author(s):  
Xudong Xu ◽  
Jianguo Liu ◽  
Yun Huang ◽  
Lanlan Zhang ◽  
Liang Yi ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Last Glacial Maximum ◽  
Intertropical Convergence Zone ◽  
Glacial Maximum ◽  
Sediment Supply ◽  
Convergence Zone ◽  
Ninetyeast Ridge ◽  
Last Glacial ◽  
The North ◽  
Terrestrial Material

Abstract. Among various climate drivers, direct evidence for the Intertropical Convergence Zone (ITCZ) control of sediment supply on the millennium scale is lacking, and the changes in ITCZ migration demonstrated in paleoclimate records need to be better investigated. Here, we use clay minerals and Sr-Nd isotopes obtained from a gravity core on the Ninetyeast Ridge to track the corresponding source variations and analyze the relationship between terrestrial material supplementation and climatic changes. On the glacial-interglacial scale, chemical weathering weakened during the North Atlantic cold climate periods, and falling sea level hindered the transport of smectite into the study area due to the exposure of islands. However, the influence of the South Asian monsoon on the sediment supply was not obvious on the millennium scale. We suggest that the north-south migration of the ITCZ controlled the rainfall in Myanmar and further directly determined the supply of clay minerals on the millennium scale because the transport of smectite was highly connected with ITCZ location. Furthermore, the regional shift of the ITCZ induced an abnormal increase in the smectite percentage during the late Last Glacial Maximum (LGM) in our records. The smectite percentage in the studied core is similar to distinct ITCZ records in different time periods, revealing that regional changes in the ITCZ were significantly obvious, and that the ITCZ is not a simple N-S displacement and closer connections occurred between the Northern-Southern Hemispheres in the eastern Indian Ocean during the late Last Glacial Maximum (LGM).

Role of the climatological intertropical convergence zone in the seasonal footprinting mechanism of the El Niño-Southern Oscillation

2021 ◽  
pp. 1-43
Author(s):  
Jae-Heung Park ◽  
Mi-Kyung Sung ◽  
Young-Min Yang ◽  
Jiuwei Zhao ◽  
Soon-Il An ◽  
...  
Keyword(s):  
North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
The North ◽  
The Pacific ◽  
The North Pacific ◽  
Northern Branch ◽  
Mean State

AbstractThe North Pacific Oscillation (NPO), a primary atmospheric mode over the North Pacific in boreal winter, is known to trigger the El Niño-Southern Oscillation (ENSO) in the following winter, the process of which is recognized as the seasonal footprinting mechanism (SFM). Based on the analysis of model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we found that the SFM acts differently among models, and the correlation between the NPO and subsequent ENSO events, called the SFM efficiency, depends on the background mean state of the model. That is, SFM efficiency becomes stronger as the climatological position of the Pacific Intertropical Convergence Zone (ITCZ) moves poleward, representing an intensification of the northern branch of the ITCZ. When the Pacific ITCZ is located poleward, the wind-evaporation-sea surface temperature (SST) feedback becomes stronger as the precipitation response to the SST anomaly is stronger in higher latitudes compared to that of lower latitudes. In addition, such active ocean-atmosphere interactions enhance NPO variability, favoring the SFM to operate efficiently and trigger an ENSO event. Consistent with the model results, the observed SFM efficiency increased during the decades in which the northern branch of the climatological ITCZ was intensified, supporting the importance of the tropical mean state of precipitation around the Pacific ITCZ.

OH measurement near the Intertropical Convergence Zone in the Pacific

1987 ◽  
Vol 92 (D2) ◽  
pp. 2020 ◽  
Author(s):  
L. I. Davis ◽  
John V. James ◽  
Charles C. Wang ◽  
Chuan Guo ◽  
Peter T. Morris ◽  
...  
Keyword(s):  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
The Pacific

scholarly journals Dynamics of the Intertropical Convergence Zone of the East Pacific

2006 ◽  
Vol 63 (2) ◽  
pp. 582-597 ◽  
Author(s):  
David J. Raymond ◽  
Christopher S. Bretherton ◽  
John Molinari
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Deep Convection ◽  
Intertropical Convergence Zone ◽  
Surface Fluxes ◽  
Balance Model ◽  
Convergence Zone ◽  
East Pacific ◽  
Layer Flow ◽  
Sst Gradient

Abstract The dynamical factors controlling the mean state and variability of the east Pacific intertropical convergence zone (ITCZ) and the associated cross-equatorial boundary layer flow are investigated using observations from the East Pacific Investigation of Climate (EPIC2001) project. The tropical east Pacific exhibits a southerly boundary layer flow that terminates in the ITCZ. This flow is induced by the strong meridional sea surface temperature (SST) gradient in the region. Away from the equator and from deep convection, it is reasonably well described on a day-to-day basis by an extended Ekman balance model. Variability in the strength and northward extent of this flow is caused by variations in free-tropospheric pressure gradients that either reinforce or oppose the pressure gradient associated with the SST gradient. These free-tropospheric gradients are caused by easterly waves, tropical cyclones, and the Madden–Julian oscillation. Convergence in the boundary layer flow is often assumed to be responsible for destabilizing the atmosphere to deep convection. An alternative hypothesis is that enhanced total surface heat fluxes associated with high SSTs and strong winds act to produce the necessary destabilization. Analysis of the moist entropy budget of the planetary boundary layer shows that, on average, surface fluxes generate over twice the destabilization produced by boundary layer convergence in the east Pacific ITCZ.

Studies of winds and weather during migrations of Simulium damnosum Theobald (Diptera: Simuliidae), the vector of onchocerciasis in West Africa

1980 ◽  
Vol 70 (4) ◽  
pp. 693-716 ◽  
Author(s):  
J. I. Magor ◽  
L. J. Rosenberg
Keyword(s):  
West Africa ◽  
Time Of Arrival ◽  
Convergence Zone ◽  
Gonotrophic Cycle ◽  
Inter Tropical Convergence Zone ◽  
The North ◽  
Simulium Damnosum ◽  
Host Seeking ◽  
First Time ◽  
High Winds

AbstractReports of the presence and absence of biting by Simulium damnosum Theo. in the Volta River Basin in 1962, 1966 and 1975 were used to identify occasions when sites were invaded by parous and nulliparous females. Circumstantial evidence suggests that this insect is a wind-borne migrant, and the weather before and during some of these invasions was examined. Although most invasions studied took place south of the Inter-tropical Convergence Zone, for the first time evidence is presented suggesting that migration also takes place to the north of this zone. Immigrants were captured at the invaded sites only when light winds or calms were present. This cannot, however, be used as proof that S. damnosum migrates and lands only where winds are light or it is calm because host-seeking is inhibited by high winds and the time of arrival, as opposed to capture on a host, is unknown. Until the factors initiating emigration, as well as the height, duration and number of flights in each gonotrophic cycle and the time of immigration are known, the present findings cannot be tested rigorously nor can wind records be used to trace the source of immigrants.

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