Diatom productivity in Northern Lake Malawi during the past 25,000 years: implications for the Position of the Intertropical Convergence Zone at Millennial and Shorter Time Scales

2007 ◽  
pp. 93-116 ◽  
Author(s):  
Thomas C. Johnson ◽  
Erik T. Brown ◽  
James McManus
Keyword(s):  
Time Scales ◽  
Lake Malawi ◽  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
The Past ◽  
Diatom Productivity

scholarly journals Obliquity pacing of the western Pacific Intertropical Convergence Zone over the past 282,000 years

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Yi Liu ◽  
Li Lo ◽  
Zhengguo Shi ◽  
Kuo-Yen Wei ◽  
Chien-Ju Chou ◽  
...  
Keyword(s):  
Intertropical Convergence Zone ◽  
Western Pacific ◽  
Convergence Zone ◽  
The Past ◽  
The Western Pacific

Seasonal changes in distribution of the African armyworm, Spodoptera exempta (Wlk.) (Lep., Noctuidae), with special reference to eastern Africa

1969 ◽  
Vol 58 (4) ◽  
pp. 661-728 ◽  
Author(s):  
E. S. Brown ◽  
Elizabeth Betts ◽  
R. C. Rainey
Keyword(s):  
Seasonal Changes ◽  
Intertropical Convergence Zone ◽  
Seasonal Migration ◽  
Spodoptera Exempta ◽  
Eastern Africa ◽  
Convergence Zone ◽  
The South ◽  
The Past ◽  
North East ◽  
South West Monsoon

Emigration of moths of the Noctuid Spodoptera exempta (Wlk.) from their developmental sites occurred within a few hours of emergence, and captive moths have lived in semi-outdoor conditions for several weeks. Flight has been recorded at all times of night in the Kenya highlands, and has shown a very marked association, seasonally, nightly and even hourly, with rain; it has been observed at temperatures down to 13°C, and inferred at temperatures several degrees lower, so that over the greater part of eastern Africa flight activity is very unlikely to be restricted by low temperatures.The breeding season of S. exempta differs markedly and consistently in different parts of eastern Africa; outbreaks of larvae recorded over the past forty years in Kenya, Tanzania and Uganda have been confined to November-July (very largely to December-May), alternating with those recorded over the past twenty years in Ethiopia, which have been confined to March-December (very largely April to August). The progressive establishment of a network of fifty light-traps in these countries since late 1962 has repeatedly recorded the arrival of invading moths before the first infestations of larvae, and has also provided evidence of a strikingly complete seasonal evacuation of much of the region; all traps in Kenya and most of those in Tanzania have revealed a period of several months in every year without a single moth of S. exempta.Seasonal successions of moth catches and outbreaks of larvae have provided repeated evidence of a progressive northward movement of populations of S. exempta, developing in March in Tanzania and Kenya, and extending across Ethiopia, in some years as far as northern Eritrea by June. The extent of these inferred displacements is consistent with the evidence so far available on behaviour and other factors affecting range of flight, which has been examined in as much detail as the limited data permit.Evidence of a return migration southwards to Kenya and Tanzania is relatively scanty. There are some indications of a north to south sequence of moth catches and outbreaks; the heaviest infestations in Kenya and Tanzania during the four-year period of detailed study were preceded by the largest catches so far recorded at the relevant time of year in Ethiopia; and in several years the first moths arriving in Kenya and Tanzania, in November-December, have appeared with the onset of the north-east monsoon, representing the southward movement of the intertropical convergence zone. Conversely, appearances of moths towards the northern limits of their inferred seasonal migration, in Ethiopia and around the Gulf of Aden in June, have shown an analogous association with the establishment of the south-west monsoon, i.e., with the northward movement of the intertropical convergence zone. Brief reference is made to evidence of seasonal migration in other parts of Africa; possibly in some years the eastern African populations may be supplemented by migrants from the south.Two recorded moth ‘ swarms ’ have been associated with weather systems characterised by particularly vigorous wind-convergence. It is suggested that wind-convergence may have contributed to the density of the ‘ swarms ’ and of the subsequent infestations of larvae.The overall effect of the seasonal changes in distribution which have been demonstrated is to bring the population into areas experiencing seasonal rains. Such a pattern of seasonal migration is likely to be of particular survival value for grass-eating insects, and such concentration of the insects as may be attributable to the associated wind-convergence may be significant in relation to the status of such insects as pests of cereal crops.Records in the literature of long-range geographical displacements of some other Lepidoptera have been found to be associated in a similar manner with analogous systems of wind and weather in other parts of the world.

CO2 radiative forcing and Intertropical Convergence Zone influences on western Pacific warm pool climate over the past 400ka

2014 ◽  
Vol 86 ◽  
pp. 24-34 ◽  
Author(s):  
Kazuyo Tachikawa ◽  
Axel Timmermann ◽  
Laurence Vidal ◽  
Corinne Sonzogni ◽  
Oliver Elison Timm
Keyword(s):  
Radiative Forcing ◽  
Warm Pool ◽  
Intertropical Convergence Zone ◽  
Western Pacific ◽  
Convergence Zone ◽  
Western Pacific Warm Pool ◽  
The Past ◽  
Pacific Warm Pool

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.

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