Meso-scale atmospheric events promote phytoplankton blooms in the coastal Bay of Bengal

The Bay of Bengal is considered to be a low productive region compared to the Arabian Sea based on conventional seasonal observations. Such seasonal observations are not representative of a calendar year since the conventional approach might miss episodic high productive events associated with extreme atmospheric processes. We examined here the influence of extreme atmospheric events, such as heavy rainfall and cyclone Sidr, on phytoplankton biomass in the western Bay of Bengal using both in situ time-series observations and satellite derived Chlorophyll a (Chl a) and sea surface temperature (SST). Supply of nutrients through the runoff driven by episodic heavy rainfall (234 mm) on 4–5 October 2007 caused an increase in Chl a concentration by four times than the previous in the coastal Bay was observed within two weeks. Similar increase in Chl a, by 3 to 10 times, was observed on the right side of the cyclone Sidr track in the central Bay of Bengal after the cyclone Sidr. These two episodic events caused phytoplankton blooms in the western Bay of Bengal which enhanced ~40% of fishery production during October–December 2007 compared to that in the same period in 2006.     

Modulation of Convectively Coupled Kelvin Wave Activity in the Tropical Pacific by ENSO

The influence of El Nio-Southern Oscillation (ENSO) on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific (EP) El Nio, central Pacific (CP) El Nio, and La Nia years, respectively, to 30-yr (1982-2011) mean statistics. The convectively coupled Kelvin waves in this study are represented by the two leading modes of empirical orthogonal function (EOF) of 2-25-day band-pass filtered daily outgoing longwave radiation (OLR), with the estimated zonal wavenumber of 3 or 4, period of 8 days, and eastward propagating speed of 17 ms-1 . The most significant impact of ENSO on the Kelvin wave activity is the intensification of the Kelvin waves during the EP El Nios. The impact of La Nia on the reduction of the Kelvin wave intensity is relatively weaker, reflecting the nonlinearity of tropical deep convection and the associated Kelvin waves in response to ENSO sea surface temperature (SST) anomalies. The impact of the CP El Nio on the Kelvin waves is less significant due to relatively weaker SST anomalies and smaller spatial coverage. ENSO may also alter the frequency, wavelength, and phase speed of the Kelvin waves. This study demonstrates that low-frequency ENSO SST anomalies modulate high-frequency tropical disturbances, an example of weather-climate linkage.     

Comments on: 'Petrogenesis of Proterozoic Lamproites and Kimberlites from the Cuddapah Basin and Dharwar Craton, Southern India'

Kimberlites intrude the late Archaean eastern Dharwar Cratonin two spatially separate fields (150 km apart, near Mahbubnagarin the north and Anantapur in the south) to the west of theProterozoic Cuddapah Basin in southern India. Two lamproitebodies intrude the thick Cuddapah Basin sediments near Chelimaand Zangamarajupalle, and a third occurs just outside the presentNE margin of the basin near Ramannapeta. Chalapathi Rao et al.(2004) have studied this spatially, and possibly temporally,close association of kimberlites and lamproites to provide insightsinto their genesis and genetic relationship. Although the mainemphasis of their paper is the petrochemical characterizationof these two suites of rocks, they also report Sr–Nd isotopedata for a small subset of samples, which they use to provideconstraints on the nature of the mantle source regions. Of some     

Eurasian snow cover and seasonal forecast of Indian summer monsoon rainfall

Abstract

This paper presents the relationship between Indian summer monsoon total rainfall and two parameters from Eurasian snow cover, one being the winter snow cover extent and the other the area of spring snowmelt. Satellite-derived Eurasian snow cover extent and Indian monsoon rainfall data were obtained from the NOAA/NESDIS and the India Meteorological Department (IMD) for the period 1966–1985. Seasonal cyclic variations of snow cover showed a higher swing in both the winter and the spring seasons of the cycle as compared to the remaining seasons of the year in the lower region of the cycle. The established inverse relation between winter snow cover and monsoon rainfall during June to September is further extended. Winter snow cover is very strongly correlated with spring snowmelt over Eurasia. Spring snowmelt area is obtained by subtracting the May snow cover extent from that of the previous February. The variations of spring snowmelt were also compared with Indian total monsoon rainfall. The detected correlation is stronger between snowmelt and monsoon rainfall than between the winter snow cover and the monsoon rainfall. There is also a significant multiple correlation among winter snow cover, spring snowmelt and monsoon rainfall. Lastly, a significant multiple correlation suggested a multiple regression equation which might improve the climatic prediction of monsoon rainfall over India.     

Plant studies in Himachal Pradesh,Western Himalaya: a systematic review

Owing to a predicted rise in temperature, increase in precipitation and the escalating anthropogenic stresses, the Himalayan ecosystems are the most threatened non-polar regions of the world. In the past, there have been racing extinctions and range shifts of several life forms in this region, particularly of the plant species. Therefore, consistent qualitative and quantitative records on botanical baseline data on a regular basis are indispensable. The current communication attempts to provide a detailed account on the current state of knowledge and research gaps in floristic studies of Himachal Pradesh, Western Himalaya. Based on an extensive review of more than 140 studies in the form of scientific peer reviewed literature on floristics, medicinal and aromatic plants(MAPs), rare, endangered, threatened and endemic species and ethno-botany, it is revealed that the number of floristic studies in Himachal Pradesh have surged in the past years but studies pertaining to the lower plants remain meagre. Unfortunately, the remote valleys including micro-watersheds lying in the coldarid regions are relatively less studied in terms of available growing stock and population status of MAPs. Depleting traditional ethno-botanical knowledge has been the major concern and, many threatened MAPs need to be accessed globally following IUCN standards. Thus, documentation of the conservation status of key MAPs, setting aside conservation areas around viable populations of threatened species, developing germplasm banks of the priority MAPs and monitoring the impacts of climate change has been suggested.