Mechanisms for the spatio-temporal development of the Tropical Pacific Meridional Mode (TPMM) are investigated using a coupled ocean-atmosphere model and observations. In both observations and the ...model, this meridional mode displays decadal variations and is most pronounced in spring and early summer. The model simulation suggests that once SST anomalies in the subtropical northeastern Pacific are initiated, say by northeasterly trade wind variability, perturbations evolve into a merdional dipole in 2–3 months. A wind-evaporative-SST feedback causes a southwestward propagation of initial subtropical SST anomalies, while anomalous equatorial upwelling helps form the southern lobe of the meridional dipole. The TPMM development is a fast process (a few months) and depends on the seasonal cycle.
The sea surface temperature (SST) anomaly of the eastern Indian Ocean (EIO) exhibits cold anomalies in the boreal summer or fall during El Niño development years and warm anomalies in winter or ...spring following the El Niño events. There also tend to be warm anomalies in the boreal summer or fall during La Niña development years and cold anomalies in winter or spring following the La Niña events. The seasonal phase-locking of SST change in the EIO associated with El Niño/Southern Oscillation is linked to the variability of convection over the maritime continent, which induces an atmospheric Rossby wave over the EIO. Local air-sea interaction exerts different effects on SST anomalies, depending on the relationship between the Rossby wave and the mean flow related to the seasonal migration of the buffer zone, which shifts across the equator between summer and winter. The summer cold events start with cooling in the Timor Sea, together with increasing easterly flow along the equator. Negative SST anomalies develop near Sumatra, through the interaction between the atmospheric Rossby wave and the underneath sea surface. These SST anomalies are also contributed to by the increased upwelling of the mixed layer and the equatorward temperature advection in the boreal fall. As the buffer zone shifts across the equator towards boreal winter, the anomalous easterly flow tends to weaken the mean flow near the equator, and the EIO SST increases due to the reduction of latent heat flux from the sea surface. As a result, wintertime SST anomalies appear with a uniform and nearly basin-wide pattern beneath the easterly anomalies. These SST anomalies are also caused by the increase in solar radiation associated with the anticyclonic atmospheric Rossby wave over the EIO. Similarly, the physical processes of the summer warm events, which are followed by wintertime cold SST anomalies, can be explained by the changes in atmospheric and oceanic fields with opposite signs to those anomalies described above.PUBLICATION ABSTRACT
The locomotor activities of individual specimens of Uca subcylindrica (Stimpson) collected from semi-arid, supratidal habitats in south Texas and northeastern Mexico were studied in the laboratory ...using periodogram analysis. When crabs were placed under constant darkness (DD) or constant illumination (LL), free-running circadian rhythms were observed in the activity recordings. The locomotor activity of strongly rhythmic crabs in LL has an average period length of 24.4 h. Crabs held in DD express motor rhythms with periods of approximately 24.0 h. In LL the most common wave form for activity is unimodal, while under DD it is bimodal. Recordings under natural illumination (NL) revealed that both period length and the time of maximum activity (phasing) varied through the year. During winter months, the crabs are primarily diurnal with peaks in activity occurring between 0900 and 2100 h and possess a circadian rhythm with a 23.9 h period. During summer, crabs were nocturnal with maximal activity between 1300 and 0600 and a circadian period closer to 24.0 h. In these experiments, the rhythmic locomotor activities of U. subcylindrica are best described as "circadian". This is unusual for a genus known for its expression of circatidal and circalunidian rhythms.
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