The influence of the 1992-1993 el niño on the reproductive biology of Scomber japonicus peruanus (Jordán & Hubb, 1925)

The influence of the 1992-1993 El Niño events on the reproductive behavior of the Scomber japonicus peruanus (Chub mackerel) was studied from samples collected monthly, along the Peruvian coast (3º23'S-14º00'S), from January 1990 to December 1993. The monthly variation of the gonadosomatic index and the frequency of the periods of gonad maturation evidenced that the spawning of the species occurred all year long, being more intense in summer. The values of the gonadosomatic index were higher during the occurrence of the 1992-1993 El Niño, while the body weight and gonad weight decreased. Regarding the condition factor, its values decreased in females over 35 cm in fork length.<br>A influência do evento El Niño 1992-1993 no comportamento reprodutivo de Scomber japonicus peruanus (cavalinha) foi estudada a partir de amostras coletadas mensalmente, ao longo do litoral peruano (3º23'S-14º00'S), de janeiro de 1990 a dezembro de 1993. A variação mensal do índice gonadossomático e a freqüência dos estágios de maturação gonadal evidenciaram que a desova da cavalinha ocorreu o ano inteiro, sendo mais intensa no verão. Os valores do índice gonadossomático foram mais elevados durante o evento El Niño, mas, em contraposição, as fêmeas apresentaram peso menor. Os dados mostraram que o fator de condição diminuiu em fêmeas com mais de 35 cm de comprimento furcal

The variation of large-magnitude volcanic ash cloud formation with source latitude

Very large magnitudes of explosive volcanic eruptions can produce giant ash clouds with diameters of hundreds to thousands of kilometers. These ash clouds are controlled by gravity and rotational forces, leading to a more radially constrained shape than clouds produced by smaller eruptions. Here we develop a dynamic model of the formation of large ash clouds that are produced by eruptions of constant intensity and finite duration, incorporating source latitude, eruption type, magnitude, and intensity. The cloud grows as a stratified intrusion in the stratosphere to an equilibrium shape that approximates an ellipsoid of revolution, rotating anticyclonically as a solid body, at sufficient large distances from the equator. More generally, the structure of the cloud is determined by the source latitude ? s and the parameter Y s = y s(?/Nd 0)1/2, wherein y s is the distance of the source from the equator, ? is the north-south gradient of the Coriolis frequency, N is the buoyancy frequency of the stratosphere, and d 0 is the maximum cloud thickness. A steady solution for an equilibrium cloud exists if Y s lies above a boundary that ranges from ?/2 at the equator to 0 at the pole. These clouds move westward at an increasing rate with decreasing latitude. Below this boundary steady solutions appear not to exist and the nature of the breakdown of the solution at the boundary suggests that the cloud, or part of it, moves toward and across the equator. The above parameters may be expressed in terms of latitude and cloud volume, which enables the model to be applied to the ash clouds of past large-magnitude eruptions. The results suggest that the behavior of clouds formed from plinian phases with eruption magnitudes M &lt; 6.5 (M = log10 m ? 7, wherein m is the erupted mass in kilograms) depends on source latitude and eruption intensity, whereas for M &gt; 6.5 they could achieve interhemispheric transport from most latitudes. For clouds from co-ignimbrite sources, for M &lt; 7.5, cross-equatorial transport is only possible for sources in the tropics, but for M &gt; 8, it is possible from most latitudes

Learning spaces: Built, natural and digital considerations for learning and learners

Learning spaces: Built, natural and digital considerations for learning and learner