Detection of possible thunderstorm formation inferred from weather element changes at ground level on a mountain slope

Authors and Affiliation: Vishnu R, Murali Das S, Sampath S and Mohan Kumar G, Centre for Earth Science Studies, Akkulam, Trivandrum, Kerala

Journal: Journal of Lightning Research, II, 12-24, 2010

Abstract: In India, Kerala state is known to have relatively high lightning incidence. The nature of spatial and temporal distribution of past incidents, type of thunderclouds which cause lightning, the topography, proximity to a mountain range 

and sea point to the possibility of the mountain weather aiding in Cb formation. For investigating the role of mountain weather in convective Cb formation a field station consisting of an automatic weather station and a lightning detector was established on the slope of the nearby Western Ghats mountain range. On thunderstorm days the mountain weather data show specific reduction in air temperature with synchronized increase in relative humidity along with a reduction in pressure of the order of 0.5 hPa between 10:00 h and 18:00 h. The variations in data are indicative of a strong updraft. The lightning detector showed thunderstorm activity, aligned with the direction of the mountain range, about an hour after detecting the changes in weather elements. Water vapour for thunderstorm formation seems to come from the nearby sea as indicated by the wind data. Data collected for three years show that existence of strong updrafts seem to be a characteristic of the mountain weather during thunderstorm months. Data from a coastal station located 40 km south west of the mountain station do not indicate updrafts either on the thunderstorm days or otherwise. As updrafts can lead to Cb formation monitoring weather elements as discussed here is useful for detecting thunderstorms at the developing stage itself.

Prevalence of autochthonous Vibrio cholera and role of abiotic environmental factors in their distribution along the Kerala- Karnataka Coast

Authors and Affiliation: V.S. Sudhanandh , S. Amaldev and K.N. Babu, Centre for Earth Science Studies, Akkulam, Trivandrum, Kerala

Journal: Research Journal of Microbiology, 5(11), 2010, 1083-1092

Abstract: Occurrence and distribution of Vibrio cholerae (VC) with respect to different abiotic environmental factors were studied for a period of three year from 2003-2005 and interpreted using Principal component analysis and Pearson correlation. Study reveals the serious dimensions of increase in VC population (2.67% in 2003, 5.33% in 2004 and 92% in 2005 in Mangalore) over the years. Among all stations, Kochi and Mangalore seems to be highly polluted. The PCA extracted four significant main components explains more than 75% of the variance. Of them the most contributing descriptors in the first PC (24.29%) were total nitrogen, silicate, temperature and V.cholerae. On the other hand V. cholerae showed significant positive correlation against temperature (0.01 levels) and also with total nitrogen and silicate (0.05 levels). Component plot showed that variables have tendency to accumulate into three distinct groups. V. cholerae and temperature belongs to one group and nutrients on the other group, which indicate that temperature and nutrients are the major factor governing the distribution of V. cholerae. The result of the study provides insight into the ecology of this aquatic species and is potentially important to the understanding of the epidemiology of cholerae on a global scale.

Late quaternary evolution of Ashtamudi-Sasthamkotta lake systems of Kerala, south west India

Authors and Affiliation: (a)K M Nair, (b)D Padmalal, (c)K P N Kumaran, (b)R Sreeja, (c)Ruta B Limaye, (b)Reji Srinivas, (a) Vakkom Moulavi Foundation Trust, Trivandrum, Kerala 695 037, India (b)Centre for Earth Science Studies, Akkulam, Trivandrum, Kerala 695 031, India (c)Palynology and Palaeoclimate Laboratory, Palaeobiology Group, Agarkar Research Institute, Pune 411 004, India

Journal: Journal of Asian Earth Sciences (2010), Volume: 37 (4) 361-372

Abstract: Sedimentological and palynological analysis of two borehole samples collected from the confluence of Kallada River with the Ashtamudi lake in the south west coast of India have been addressed while ascertaining the late quaternary evolution. Of the two borehole samples, the one collected from Pangod (903'N-7642'E) reveals a fining upward sequence with medium to coarse sand (3.05m) at base, organic carbon rich, silt and fine sand dominated sediments (2m) at the middle and yellowish brown, muddy sediments (3.2m) at the top. The middle layer embeds a suite of partly carbonized, sub-fossil logs of wet evergreen to semi-evergreen vegetation. The palynoflora of this layer reveals that the depositional site is within the tidal limit and deposition occurred under high precipitation and atmospheric humidity. The similarity in 14C dates of a wood at 5m bgl (749090yrs BP) and the embedding sediments (748080yrs BP) indicate quick burial of the riparian vegetation. The West Kallada borehole (930'N-7637'E) reveals Middle to Late Holocene sequence of clayey silt (6250110yrs BP-388080yrs BP) and sand resting unconformably over greyish white, clayey sand with pebbles and granules derived from laterite provenance. Palynological analysis shows that the Holocene sedimentation took place under marine/nearly marine environment and later changed to brackish water and finally to freshwater environment. Marine transgression ~6000yrs BP coupled with heavy rainfall in the hinterlands was responsible for faster sedimentation in the region. The heavy mineral contents, especially opaques, garnet and sillimanite in the sediment samples of the study area as well as the bathymetric configuration of the Ashtamudi, Sasthamkotta and Chelupola lakes reiterate the fact that these lakes have been evolved from an embayment consequent to incomplete/partial silting up during Early to Middle Holocene higher sea levels and also under high rainfall of the Holocene climatic optimum of around 10,000-7000yrs BP.

Changing pattern of species composition and species utilization in homegardens of Kerala, India

Authors and Affiliation: Chandrashekara UM and Baiju EC, Kerala Forest Research Institute Sub Centre, Chandakunnu P.O., Nilambur 679 342, Kerala, India

Journal: Tropical Ecology 51(2): 221-233, 2010

Abstract: Tropical homegardens are traditional agroforestry systems with complex structure and multiple functions. These multi-species production systems are regarded as the model systems for designing sustainable agroecosystems. However, with the advent of market economy, mixed species tropical homegardens are being transformed into single species dominant homegardens. The objective of this study was to analyze the impact of homegarden transformation on species diversity and also changing pattern of usage of species wealth by farmers in Kerala. The plant diversity index values ranged from 1.02 to 2.97 with significantly (P < 0.05) greater value in old mixed-species homegardens (OMSHG) followed by new mixedspecies homegardens (NMSHG), old single species dominant homegardens (OSSHG) and new single-species homegardens (NSSHG). About 65 % - 83 % of total number of naturally growing species in mixed species homegardens and 20 % - 30 % in single species dominant homegardens are managed. The ratio between actual usage of species and the potential uses of species in each homegarden was calculated. The value obtained for naturally growing species was significantly greater (P < 0.05) in the old homegardens than in new homegardens. We conclude that the knowledge base on the properties and potential uses of naturally growing species in homegardens is depleting due to transformation of homegardens into single species dominant systems.

Relationship between heavy mineral placer deposits and hinterland rocks of southern Kerala: A new approach for source-to-sink link from the chemistry

Authors and Affiliation: G.R. Ravindra Kumar & C. Sreejith, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Indian Journal of Geo-Marine Sciences, Vol. 39 (4), December 2010, pp. 562-571

Abstract: Beach sediments of the Kerala coast contain rich economically important heavy mineral deposits. Most previous studies have traced the source of heavy minerals to the Precambrian crystalline formations in the hinterland based on comparative mineral occurrences. No previous study has attempted to utilize petrological and geochemical characteristics and mineral chemistry of source rocks to effectively compare and determine sediment provenance. A clear knowledge on the composition of minerals from source and sink is important in precise recognition of source rock. Present study consists the geological, geomorphologic setting and mineralogical characteristics of hinterland rocks to trace their connection to placer deposits. It is recognized that garnet as the abundant heavy mineral in the placer sediments and in source rocks of different ages and petrogenetic affinity. Garnet composition varies between different source rock types due to its strong dependency on the bulk rock composition. In order to decipher the provenance we have compared major element composition of garnet in the source rocks and placer deposits. Compelling similarities in mineralogical and mineral chemical characteristics of garnets (Alm68Prp28Grs3Sps1) is noted between khondalites and placer sediments suggesting latter as major source rock for placer deposits of southern Kerala. The study demonstrates excellent potential of garnets in identifying placer mineral source.

Environmental Impact Assessment of sand mining from the small catchment river in the southwestern coast of India. Environmental Management

Authors and Affiliation: Sreedharan Sreebha and Damodaran Padmalal, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Environmental Management (2011), Vol. 47, pp.130-140.

Abstract: In the past few decades, the demand for construction grade sand is increasing in many parts of the world due to rapid economic development and subsequent growth of building activities. This, in many of the occasions, has resulted in indiscriminate mining of sand from in-stream and floodplain areas leading to severe damages to the river basin environment. The case is rather alarming in the small catchment rivers like those draining the southwestern coast of India due to limited sand resources in their alluvial reaches. Moreover, lack of adequate information on the environmental impact of river sand mining is a major lacuna challenging regulatory efforts in many developing countries. Therefore, a scientific assessment is a pre-requisite in formulating management strategies in the sand mining-hit areas. In this context, a study has been made as a case to address the environmental impact of sand mining from the in-stream and floodplain areas of three important rivers in the southwestern coast of India namely the Chalakudy, Periyar and Muvattupuzha rivers, whose lowlands host one of the fast developing urban-cum-industrial centre, the Kochi city. The study reveals that an amount of 11.527 million ty(-1) of sand (8.764 million ty(-1) of in-stream sand and 2.763 million ty(-1) of floodplain sand) is being mined from the midland and lowland reaches of these rivers for construction of buildings and other infrastructural facilities in Kochi city and its satellite townships. Environmental Impact Assessment (EIA) carried out as a part of this investigation shows that the activities associated with mining and processing of sands have not only affected the health of the river ecosystems but also degraded its overbank areas to a large extent. Considering the degree of degradation caused by sand mining from these rivers, no mining scenario may be opted in the deeper zones of the river channels. Also, a set of suggestions are made for the overall improvement of the rivers and its biophysical environment.

Evolution of the coastal wetland systems of SW India during the Holocene: Evidence from marine and terrestrial archives of Kollam coast, Kerala

Authors and Affiliation : D. Padmalal, K.P.N. Kumaran, K.M. Nair, B. Baijulal, Ruta B. Limaye, S. Vishnu Mohan, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Quaternary International, Volume 237, Issues 1-2, 15 May 2011, Pages 123-139

Abstract: Kerala coast in southwest India is endowed with an interlacing network of wetlands evolved during the Late Quaternary. The wetlands in the southern part of Kerala, especially around Kollam district, show antecedent characteristics and are incised on the Neogene sediments. These wetlands include 20.0–35.0 m thick deposits of Holocene sediments containing good archives of landform evolution and climate changes. Holocene sedimentation was initiated at about 8920 ± 110 BP and is represented mainly by sub-fossil wood/peat or carbonaceous clays. Subsequent deposition of brackish water to marine sediments occurred in the Middle Holocene. The proposed evolutionary model reveals that many wetland bodies including Sasthamkotta Lake, Chelupola Lake, Chittumalachira Lake and Kotta Lake were evolved from the proto-estuarine basins. The upper arms of the pre-Holocene Ashtamudi and Paravur estuaries were cut off due to progradation of alluvial sediments during the Holocene Climatic Optimum.