Oceanic mixed layer variations during the movement of cyclone along symmetric tracks in the Indian Ocean

111-122The understanding of significant changes in the oceanic mixed layer is important for dynamical prediction of tropical cyclone. Present study aims at examining the variations in the upper ocean parameters during the movement of tropical cyclone in northern and southern Indian Ocean, by applying 1½ layer wind driven reduced gravity ocean model. Different idealized tracks in the Bay of Bengal and their mirror images in southern hemisphere are considered, The model produced mixed layer depth, temperature and currents are compared for northern and southern hemispheric cyclone cases. Also the effect of latitude for westward moving cyclones in both the hemisphere is investigated. For this, tracks in the Arabian Sea and their counter parts in the southern hemisphere are considered. The maximum cooling found in the wake of cyclone is of the order of 3 - 4°C, which is comparable with earlier studies and observations. This significant cooling can cause weakening of the storm. This can be useful for prediction especially in the event of a cyclonic storm heading towards land and likely to make land fall. Moreover it is also seen that the mixed layer is cooled more on the right (left) of the storm track in northern (southern) hemisphere. This cooling decreases for the storms translating along higher latitudes implying the sensitivity of the latitudinal location of the storm. </span

Interannual variability in simulated circulation along east coast of India

115-120A two and a half layer reduced gravity model is used to simulate the upper layer circulation along the east coast of India. The model climatology of upper layer circulations obtained from 15 year model simulation (1977-1991) is found to be in good agreement with the observed currents. A cyclonic gyre found in June-July around 10°N in the lower layer (~60m below surface) has large interannual variability. The gyre is absent in 1982 and 1984 and is very weak in 1987. Transport anomalies computed at four sections along the coast indicate large interannual variability. The upper layer transports along some section have shown a periodicity of 5-6 years

Numerical simulation of North Indian Ocean State prior to the onset of SW monsoon using SSM/I winds

The Sea Surface Temperatures (SST) and currents are simulated over the north Indian Ocean, during the onset phase of southwest monsoon for the three years 1994, 1995, and 1996, using daily Special Sensor Microwave/Imager (SSM/I) winds and National Center for Environmental Prediction (NCEP) heat fluxes as forcings in the 21/2 layer thermodynamic numerical ocean model. The results are discussed for the 30-day period from 16 May to 13 June for all the three years, to determine the ocean state during the onset phase of SW monsoon. The maximum variability in the simulated SST is found along the Somali coast, Indian coasts, and equatorial regions. The maximum SST in the North Arabian Sea is found to be greater than 30°C and minimum SST in the west equatorial region is 25°C during the onset phase of all three years. Model SSTs are in agreement with Reynolds SST. SST gradients in the north-south as well as in the east-west directions, west of 80°E are found to change significantly prior to the onset. It can be inferred from the study that the SST gradient of 2.5°C/2000 km is seen due north and due west of the region 2°-7°S, 60°-65°E, about 8 to 10 days prior to the arrival of SW monsoon near Kerala coast. Upper and lower layer circulation fields do not show prominent interannual variability

Effects of untreated bed nets on the transmission of Plasmodium falciparum, P. vivax and Wuchereria bancrofti in Papua New Guinea

The impact of untreated bed nets on the transmission of human malaria and filariasis in a village in a hyperendemic area of Papua New Guinea was studied. In anopheline mosquitoes, the Plasmodium falciparum sporozoite antigen positivity rate, filarial infection rates and human blood indices dropped significantly after bed nets were introduced. This reduction in human-vector contact did not affect mosquito density as no significant difference in either landing rates or indoor resting catches was found. The number of bed nets in a house and ownership of dogs were factors significantly associated with a reduction in the number of indoor resting mosquitoes. However, the reduction in the P. falciparum sporozoite antigen rate in mosquitoes was not accompanied by a reduction in either malaria parasite or antibody prevalences'or titres against the P. falciparum circumsporozoite protein