A numerical model study of the effects of interannual timescale wave propagation on the predictability of the Atlantic meridional overturning circulation

We investigate processes leading to uncertainty in forecasts of the Atlantic meridional overturning circulation (AMOC). A climate model is used to supply initial conditions for ensemble simulations in which members initially have identical ocean states but perturbed atmosphere states. Baroclinic transports diverge on interannual timescales even though the ocean is not eddy-permitting. Interannual fluctuations of the model AMOC in the subtropical gyre are caused by westward propagating Rossby waves. Divergence of the predicted AMOC with time occurs because the waves develop different phases in different ensemble members predominantly due to differences in eastern boundary windstress curl. These windstress fluctuations communicate with interior ocean transports via modifications to the vertical velocity and the vortex stretching term dw/dz. Consequently, errors propagate westwards resulting in longer predictability times in the interior ocean compared with the eastern boundary. Another source of divergence is transport anomalies propagating along the Gulf Stream (and other boundary currents). The propagation mechanism seems to be predominantly advection by mean currents, and we show that the arrival of westward propagating waves can trigger development of these anomalies. The mean state of the AMOC has a small effect on interannual predictability in the subtropical gyre, most likely because eastern boundary windstress curl predictability is not strongly dependent on the state of the AMOC in the subtropics. Eastern boundary windstress curl was more predictable at 45{degree sign}N when the AMOC was in a strongly decreasing state, but, unlike at 30{degree sign}N, no mechanism was found linking windstress curl fluctuations with deep transports

Simple Method for Enrichment of Azadirachtin from Neem Seeds

990-994Azadirachtin the principle active constituent of Azadirachta indica ranges from 0.3 to 0.6 per cent. A simplified procedure, when compared to established methods, has been adopted to enrich azadirachtin ‘A’ to 50 per cent using minimum possible steps without resorting to chromatographic techniques. It involves additional partition with CCl4 before final extraction which removes most of nimbin, salanin, and allied triterpenoids. Enriched product finds immense utility in preparing formulations with high azadirachtin and also in isolating pure azadirachtin by adopting preparative HPLC

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Not AvailableDuring a fishing voyage of M. T. 'Kalyani ' 111 of the Deep Sea Fishing Station, 'Bombay, in February 1965, in one of the surface plankton hauls made at 71° IYE., 19"35'N. to the West-North-West of Bombay a considerable number of elongated and elliptical eggs with segmented yolk (Fig. 1) were observed. This type of egg is believed to belong to the genus Anchoviella. The eggs were found to be in a very -early stage of development with the embryo just begintling to take shape. The length of the eggs varied from 1.04 mm. to 1.24mm, and the breadth from 0.49 mm,Not Availabl