Madhulatha A.,National Atmospheric Research Laboratory |
Rajeevan M.,Ministry of Earth science
Meteorology and Atmospheric Physics | Year: 2017
Main objective of the present paper is to examine the role of various parameterization schemes in simulating the evolution of mesoscale convective system (MCS) occurred over south-east India. Using the Weather Research and Forecasting (WRF) model, numerical experiments are conducted by considering various planetary boundary layer, microphysics, and cumulus parameterization schemes. Performances of different schemes are evaluated by examining boundary layer, reflectivity, and precipitation features of MCS using ground-based and satellite observations. Among various physical parameterization schemes, Mellor–Yamada–Janjic (MYJ) boundary layer scheme is able to produce deep boundary layer height by simulating warm temperatures necessary for storm initiation; Thompson (THM) microphysics scheme is capable to simulate the reflectivity by reasonable distribution of different hydrometeors during various stages of system; Betts–Miller–Janjic (BMJ) cumulus scheme is able to capture the precipitation by proper representation of convective instability associated with MCS. Present analysis suggests that MYJ, a local turbulent kinetic energy boundary layer scheme, which accounts strong vertical mixing; THM, a six-class hybrid moment microphysics scheme, which considers number concentration along with mixing ratio of rain hydrometeors; and BMJ, a closure cumulus scheme, which adjusts thermodynamic profiles based on climatological profiles might have contributed for better performance of respective model simulations. Numerical simulation carried out using the above combination of schemes is able to capture storm initiation, propagation, surface variations, thermodynamic structure, and precipitation features reasonably well. This study clearly demonstrates that the simulation of MCS characteristics is highly sensitive to the choice of parameterization schemes. © 2017 Springer-Verlag Wien
Ratnam M.V.,National Atmospheric Research Laboratory |
Santhi Y.D.,Sri Venkateswara University |
Rajeevan M.,Ministry of Earth science |
Rao S.V.B.,Sri Venkateswara University
Atmospheric Research | Year: 2013
Convection plays an important role in maintaining the thermodynamic structure of the atmosphere particularly in the tropical regions and it is often associated with clouds and precipitation. In the present study we report the diurnal variation of various stability indices observed using intensive radiosonde observations made during October 2010 to October 2011 over Indian tropical region, Gadanki (13.5°N, 79.2°E). Simultaneous co-located microwave radiometer (MWR) observations collected during April-October 2011 are used for comparison. Detailed comparison between these two independent techniques has been made which will be very much useful in assessing the data from MWR for Nowcasting. In general, MWR observations show warm (cold) bias in the temperature, except at 0.5. km, when compared to radiosonde observations below (above) 3-4. km, assuming latter as a standard technique. In case of water vapor, MWR observations show wet (dry) bias below (above) 2-3. km depending on the time. Nevertheless, very good comparison in several convection indices is noticed between the two different techniques, particularly in the trends though some differences are noticed in the amplitudes. For about 25% of time MWR is unable to estimate the Convective Available Potential Energy (CAPE) as equilibrium level is above the altitude that MWR can detect. Strong diurnal variation in CAPE and other thermodynamic parameters is noticed with maximum in the afternoon and minimum in the early morning hours in all the seasons except in winter over this tropical station. © 2012 Elsevier B.V.
Madhulatha A.,National Atmospheric Research Laboratory |
Rajeevan M.,Ministry of Earth science |
Venkat Ratnam M.,National Atmospheric Research Laboratory |
Bhate J.,National Atmospheric Research Laboratory |
Naidu C.V.,Andhra University
Journal of Geophysical Research: Atmospheres | Year: 2013
In the present study, the feasibility of nowcasting convective activity is examined by using thermodynamic indices derived from the ground-based microwave radiometer (MWR) observations located at a tropical station, Gadanki (13.5°N, 79.2°E). There is a good comparison between thermodynamic parameters derived from MWR and colocated GPS radiosonde observations, indicating that MWR observations can be used to develop techniques for nowcasting severe convective activity. Using MWR observations, a nowcasting technique was developed with the data of 26 thunderstorm cases observed at Gadanki. The analysis showed that there are sharp changes in some thermodynamic indices, such as the K index, the humidity index, precipitable water content, the stability index, and equivalent potential temperature lapse rates, about 2-4 h before the occurrence of thunderstorm. A superepoch analysis was made to examine the composite temporal variations of the thermodynamic indices associated with the occurrence of thunderstorms. The superepoch analysis revealed that 2-4 h prior to the storm occurrence, appreciable variations in many parameters are observed, suggesting thermodynamic evolution of the boundary layer convective instability. It is further demonstrated that by monitoring these variations it is possible to predict the ensuing thunderstorm activity over the region at least 2 h in advance. The association between the temporal evolution of thermodynamic indices and convective activity has been tested for the independent case of nine thunderstorms. The present results suggest that ground-based MWR observations can be used effectively to predict the occurrence of thunderstorms at least 2 h in advance. Key Points Validation of radiometer data with radiosonde Corelation between lightning activity and instability indices Nowcasting scheme for severe convection using radiometer data. © 2012 American Geophysical Union. All Rights Reserved.
Rawat G.,Wadia Institute of Himalayan Geology |
Arora B.R.,Ministry of Earth science |
Gupta P.K.,Indian Institute of Technology Roorkee
Tectonophysics | Year: 2014
Magnetotelluric (MT) measurements along a profile cutting across the Garhwal Himalaya of India are inverted to obtain 2-D electrical resistivity structures of the Himalayan wedge and of the underthrusting Indian plate. The imaged resistivity cross-section is dominated by a low-angle north-east dipping intra-crustal high conducting layer (IC-HCL) with an average thickness of 5. km. At transition from the Lesser Himalaya to the Higher Himalaya, the IC-HCL is marked by a ramp structure across which its top jumps from a depth of 8. km to 13. km. High conductivity of the layer is caused by pounding of upward propagating metamorphic fluids trapped by tectonically induced neutral buoyancy. In compression regime of the Himalaya, the mechanical weakening effects of the fluids counteract the fault-normal stresses, thereby facilitating thrust-type earthquakes on a plane imaged as the top of the IC-HCL. It is suggested that in the Himalaya collision belt, like the active subduction zone, the active seismic plane forming seat of large and great earthquakes is located a few kilometers above the top of the down-going plate. In this tectonic setting, the high conductance ramp symbolizes a block of low shear strength and high strain, which under the deviatoric stresses release accentuated stresses into the brittle crust, thereby generating small but more frequent earthquakes in the narrow Himalayan Seismic Belt. In response to either the co-seismic pumping or the stress transfer during inter-seismic period, the upward infiltration of fluid fluxes into the over pressurized zones sufficiently reduces the shear strength of local thrusts and shear zones, turning these into locales of concentrated seismicity. © 2014 Elsevier B.V.
Dastidar P.G.,Ministry of Earth science |
Mallik A.,Bose Institute of India |
Mandal N.,Bose Institute of India
Scientometrics | Year: 2013
Shrimp aquaculture constitutes a major economic activity of some middle- and low-level economies in the world. Though it is practiced by around 70 countries, it is primarily dominated by China, Thailand, Indonesia, Vietnam, Ecuador and India. These six countries account for 80 % of the global shrimp production. The study has highlighted the role of research in the development of the industry by taking the examples of Penaeus vannamei and P. monodon. In case of the former, a seven time rise in quantum of research (studied by the number of publications as a proxy) could induce five time increase in production, whereas, in the latter case similar pattern was not noticed. The study has observed that based on shrimp production and research contribution; the major 30 countries associated with shrimp aquaculture could be categorized as: (i) high production, high-research contribution, (ii) low production, high-research contribution and (iii) high production, low-research contribution. The countries under the third category are at great risk and may suffer huge economic losses in the event of outbreak of any disease. By generating network map of research linkage across different countries the study has highlighted the potential countries for strengthening the existing linkage and fostering new linkage for knowledge consolidation. The study has given some suggestion for policy formulation for achieving a rapid growth of shrimp aquaculture in the world. © 2013 Akadémiai Kiadó, Budapest, Hungary.
Maini P.,Ministry of Earth science |
Rathore L.S.,Mausam Bhavan
Current Science | Year: 2011
A pilot study was conducted to assess the economic impact of weather forecast-based advisories issued to 15 of the 127 Agrometeorological Advisory Service (AAS) units of the Ministry of Earth Sciences, Government of India. Six seasons comprising three Kharif (summer) and three Rabi (winter) during 2003-2007 were chosen. The major crops chosen for the study included food grains, oilseeds, cash crops, fruit and vegetable crops. The sample set consisted of 80 farmers, comprising 40 responding and 40 non-responding farmers. The main aim was to study the percentage increase/ decrease in the yield and net return due to AAS. Results obtained suggest that the AAS farmers accrued a net benefit of 10-15% in the overall yield and a reduction by 2-5% in the cost of cultivation over the non-AAS farmers.
Jain S.K.,Indian Institute of Technology Roorkee |
Kumar V.,Ministry of Earth science |
Kumar V.,National Institute of Hydrology |
Saharia M.,National Institute of Technology Silchar
International Journal of Climatology | Year: 2013
The northeast region (NER) of India covers an area of 0.26 million km2. This region is one of the highest rainfall-receiving regions on the planet. Consequently, it has huge water and hydropower potential and analysis of rainfall and temperature trends would be of interest to water and energy planners. Trends in monthly, seasonal, and annual rainfall and temperature on the subdivision and regional scale for the NER were examined in this study. Trend analysis of rainfall data series for 1871-2008 did not show any clear trend for the region as a whole, although there are seasonal trends for some seasons and for some hydro-meteorological subdivisions. Similar analysis for temperature data showed that all the four temperature variables (maximum, minimum, and mean temperatures and temperature range) had rising trend. Notably for the post-monsoon season, the Sen's estimator of slope (°C/year) was 0.019, 0.011, and 0.015 for the maximum, minimum, and mean temperature, respectively. © 2012 Royal Meteorological Society.
Pandey A.,Ministry of Earth science
International Journal of Mining Science and Technology | Year: 2013
Polymetallic sulphides have been consistent source of metals like iron, copper, zinc and lead. Apart from these they are also seen as economically viable resources of silver and gold. As the demand of these metals is showing an astoundingly increasing trend, the search for their resources has also increased in similar folds. This has resulted in many nations' focus on deep seabed resources of the polymetallic sulphides. Consequently, International Seabed Authority (ISBA) has provided 'Regulations' to obtain plan of work for exploration of polymetallic sulphide deposits in deep seabed 'Area'. Following the release of these Regulations, several countries are in the process of obtaining the licence for exploration of these metals from the deep seabed regions. Detailed information about the science and ISBA Regulations for exploration of polymetallic sulphide deposits is prerequisite to submit an application to ISBA for their exploration. The current contribution provides a comprehensive review of the science behind locating polymetallic sulphide deposits in geological setting of deep seabed as well as about the ISBA Regulations for their exploration. © 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.
Shah S.K.,University of Lucknow |
Bhattacharyya A.,University of Lucknow |
Chaudhary V.,Ministry of Earth science
Dendrochronologia | Year: 2014
The relationship of streamflow records of the Lachen River with tree-ring parameters of total tree-ring width (TRW), earlywood width (EWW) and latewood width (LWW) chronologies of Larix griffithiana from Lachen, North Sikkim, Eastern Himalaya was generated. These chronologies correlate significantly with the observed discharge of the Lachen River where the EWW chronology explains 61.2% of the streamflow variance. Based on this result, Lachen River discharge for the period of previous year March to current year February was reconstructed using EWW chronology, which extends back to AD 1790. In the smoothed reconstructed data the period of extreme low streamflows were during AD 1791-1805, 1813-1822 and 1914-1925 and the extreme highs were during AD 1823-1835, 1879-1890, 1926-1946 and 1980-1989. The streamflow is also found to be lower than average during the monsoon failure (or East India Drought) of AD 1792-1796 and past great droughts of AD 1876-1878. The lower tree growth during AD 1816-1822 is consistent with that of the Tambora volcanic eruption of Indonesia in AD 1815. High spectral power at 4-8 years in the reconstructed streamflow is similar to that of ENSO range. © 2012 Elsevier GmbH.
Verma M.,Ministry of Earth science |
Bansal B.K.,Ministry of Earth science
International Journal of Earth Sciences | Year: 2013
The Indian subcontinent is characterized by various tectonic units viz., Himalayan collision zone in North, Indo-Burmese arc in north-east, failed rift zones in its interior in Peninsular Indian shield and Andaman Sumatra trench in south-east Indian Territory. During the last about 100 years, the country has witnessed four great and several major earthquakes. Soon after the occurrence of the first great earthquake, the Shillong earthquake (M w: 8.1) in 1897, efforts were started to assess the seismic hazard in the country. The first such attempt was made by Geological Survey of India in 1898 and since then considerable progress has been made. The current seismic zonation map prepared and published by Bureau of Indian Standards, broadly places seismic risk in different parts of the country in four major zones. However, this map is not sufficient for the assessment of area-specific seismic risks, necessitating detailed seismic zoning, that is, microzonation for earthquake disaster mitigation and management. Recently, seismic microzonation studies are being introduced in India, and the first level seismic microzonation has already been completed for selected urban centres including, Jabalpur, Guwahati, Delhi, Bangalore, Ahmadabad, Dehradun, etc. The maps prepared for these cities are being further refined on larger scales as per the requirements, and a plan has also been firmed up for taking up microzonation of 30 selected cities, which lie in seismic zones V and IV and have a population density of half a million. The paper highlights the efforts made in India so far towards seismic hazard assessment as well as the future road map for such studies. © 2013 Springer-Verlag Berlin Heidelberg.