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Recent studies have challenged the validity of the Redfield ratio. It is proposed that physical and biogeochemical processes govern the geographical variations in carbon : nitrogen : phosphorus (C : N : P) ratios. However, this proposal remains to be examined through concurrent observations of C : N : P ratios with physical and biogeochemical processes in various marine reservoirs. Here, we sampled the Arabian Sea for its C, N, and P content in organic and inorganic pools during the winter monsoon. We analyzed the role of convective mixing, eddies, and N2fixation to explain the variation in observed elemental ratios. Convective mixing injected the cold water and enhanced the supply of N and P nutrients in the top layer (surface to 50–75 m) of the northern Arabian Sea. This led to a decrease in the N : P and C : P ratios in the particulate organic matter in the northern region, but C : N : P increased equatorward, averaging 245 : 32 : 1 in the top layer of the Arabian Sea. The variation in the elemental ratios in the top layer is best explained by the changes in water temperature. N2fixation contributed negligibly to the N : P ratio of the export flux. The substantial decrease in N : P ratios of nutrients in the subsurface waters is most likely caused by the denitrifying conditions in the Arabian Sea. As the processes of convective mixing and eddies are are prevalent oceanic processes, our observations underpin that the interplay of these processes leads to changes in the elemental ratios globally.

Fog and associated significant reduced visibility lead to flight cancellation, delay and diversion at IGI airport during the winter months every year. In the present study, a 24-hr and 48-hr fog/visibility forecast with value addition method has been implemented at IGI airport during the months of December and January, 2020–2021. The meteorological parameters information related to fog is obtained from IMD-GFS model outputs. A detailed forecast verification has also been carried out using the METAR and synoptic observations. Results indicated that the 24-hr fog/visibility forecast has promising skill score with a hit rate of 0.92 and Critical Success Index (CSI) of 0.68, whereas the false alarm ratio (0.28) is quite low. This indicates that the method has reasonable predictive accuracy and can be used for fog/visibility forecasting at regional scale. However, the 48-hr forecast scheme performance needs to be improved. In addition, detailed analysis has also been performed on various surface meteorological parameters such as wind speed and relative humidity during the period and the results were in agreement with the fog/visibility observations in most of the cases. In future, the current fog/visibility forecasting method would be further improved with increased robustness of the models used and also be objective.