Now showing items 1-9 of 9
| Abstract: | This thesis entitled southern hemispheric features and their Teleconnection with indian summer monsoon.Southern hemisphere is entirely distinct from the northern hemisphere in many aspects, which is well reflected in atmospheric and oceanic properties.The thesis consists of eight chapters, in which the first chapter contains an overview of southern hemisphere. In this chapter, variability in southern hemisphere is described along with Indian summer monsoon and its teleconnection. The different types of data sets used and various methodologies adopted in the present thesis were described in Chapter 2. The period of climate shift and the magnitude of anomalies after the climate shift, which extended from troposphere to stratopause level, were investigated in detail and presented in chapter 3. Chapter 4 depicts the recent trend and variability in southern stratosphere. The higher order variability during various months and the frequency of extremity is included in this chapter.Climatology of divergence and convergence after the documented shift is reported in chapter 5.Southern extratropical connection to Indian summer monsoon through the modulation of SAM is presented in Chapter 6.Chapter 7 deals with the modulation of SAM‐Monsoon link through North Atlantic Oscillation. |
| Description: | Department of Atmospheric Sciences Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3086 |
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| Dyuthi-T1060.pdf | (15.23Mb) |
| Abstract: | The objective of the present study is to understand the spatial and temporal variability of sea surface temperature(SST), precipitable water, zonal and meridional components of wind stress over the tropical Indian Ocean to understand the different scales of variability of these features of Indian Ocean. Empirical Orthogonal Function (EOF) and wavelet analysis techniques are utilized to understand the standing oscillations and multi scale oscillations respectively. The study has been carried out over Indian Ocean and South Indian Ocean. For the present study, NCEP/NCAR(National Center for Environmental Prediction National Center for Atmospheric Research) reanalyzed daily fields of sea surface temperature, zonal and meridional surface wind components and precipitable water amount during 1960-1998 are used. The principle of EOF analysis and the methodology used for the analysis of spatial and temporal variance modes. |
| URI: | http://dyuthi.cusat.ac.in/purl/667 |
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| Dyuthi-T0087.pdf | (5.702Mb) |
| Abstract: | Ozone present in the atmosphere not only absorbs the biologically harmful ultraviolet radiation but also is an important ingredient of the climate system. The radiative absorption properties of ozone make it a determining factor in the structure of the atmosphere. Ozone in the troposphere has many negative impacts on humans and other living beings. Another significant aspect is the absorption of outgoing infrared radiation by ozone thus acting as a greenhouse gas. The variability of ozone in the atmosphere involves many interconnections with the incoming and outgoing radiation, temperature circulation etc. Hence ozone forms an important part of chemistry-climate as well as radiative transfer models. This aspect also makes the quantification of ozone more important. The discovery of Antarctic ozone hole and the role of anthropogenic activities in causing it made it possible to plan and implement necessary preventive measures. Continuous monitoring of ozone is also necessary to identify the effect of these preventive steps. The reactions involving the formation and destruction of ozone are influenced significantly by the temperature fluctuations of the atmosphere. On the other hand the variations in ozone can change the temperature structure of the atmosphere. Indian subcontinent is a region having large weather and climate variability which is evident from the large interannual variability of monsoon system over the region. Nearly half of Indian region comprises the tropical region. Most of ozone is formed in the tropical region and transported to higher latitudes. The formation and transport of ozone can be influenced by changes in solar radiation and various atmospheric circulation features. Besides industrial activities and vehicular traffic is more due to its large population. This may give rise to an increase in the production of tropospheric ozone which is greenhouse gas. Hence it becomes necessary to monitor the atmospheric ozone over this region. This study probes into the spatial distribution and temporal evolution of ozone over Indian subcontinent and discusses the contributing atmospheric parameters. |
| Description: | Department of Atmospheric Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3555 |
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| Dyuthi-T1537.pdf | (10.16Mb) |
| Description: | Department of Atmospheric Sciences, School of Marine Sciences, Cochin University of Science And Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2131 |
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| Dyuthi-T0491.pdf | (10.62Mb) |
| Abstract: | The aim of the present study is to understand the characteristics and properties of different wave modes and the vertical circulation pattern in the troposphere and lower stratosphere over Indian region using data obtained from the Indian Mesosphere-Stratosphere Troposphere (MST) radar, National Center for Environmental Prediction/National Centres of Atmospheric Research (NCEP/NCAR) reanalysed data and radiosonde observations.Studies on the vertical motion in monsoon Hadley circulation are carried out and the results are discussed . From the analysis of MST radar data, an overall picture of vertical motion of air over Indian region is explained and noted that there exists sinking motion both during winter and summer. Besides, the study shows that there is an anomalous northerly wind in the troposphere over the southern peninsular region during southwest monsoon season.The outcome of the study on intrusion of mid-latitude upper tropospheric trough and associated synoptic-scale vertical velocity over the tropical Indian latitudes are reported and discussed . It shows that there is interaction between north Indian latitudes and tropical easterly region, when there is an eastward movement of Western Disturbance across the country. It explains the strengthening of westerlies and a change of winter westerlies into easterlies in the tropical troposphere and lower stratosphere. The divergence field computed over the MST radar station shows intensification in the downward motion in association with the synoptic systems of the northwest Indian region. |
| Description: | Department of Atmospheric Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2115 |
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| Dyuthi-T0469.pdf | (3.484Mb) |
| Abstract: | The present study illustrates the biennial oscillation in different ocean-atmosphere parameters associated with interannual variability of Indian summer monsoon rainfall.It also accounts the role of different processes like ENSO, IOD, QBO and ISO in the monsoon variability during the TBO years. |
| Description: | Department of Atmospheric Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1945 |
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| Dyuthi-T0475.pdf | (14.80Mb) |
| Abstract: | This doctoral thesis addresses the growing concern about the significant changes in the climatic and weather patterns due to the aerosol loading that have taken place in the Indo Gangetic Plain(IGP)which includes most of the Northern Indian region. The study region comprises of major industrial cities in India (New Delhi, Kanpur, Allahabad, Jamshedpur and Kolkata). Northern and central parts of India are one of the most thickly populated areas in the world and have the most intensely farmed areas. Rapid increase in population and urbanization has resulted in an abrupt increase in aerosol concentrations in recent years. The IGP has a major source of coal; therefore most of the industries including numerous thermal power plants that run on coal are located around this region. They inject copious amount of aerosols into the atmosphere. Moreover, the transport of dust aerosols from arid locations is prevalent during the dry months which increase the aerosol loading in theatmosphere. The topography of the place is also ideal for the congregation of aerosols. It is bounded by the Himalayas in the north, Thar Desert in the west, the Vindhyan range in the south and Brahmaputra ridge in the east. During the non‐monsoon months (October to May) the weather in the location is dry with very little rainfall. Surface winds are weak during most of the time in this dry season. The aerosols that reach the location by means of long distance transport and from regional sources get accumulated under these favourable conditions. The increase in aerosol concentration due to the complex combination of aerosol transport and anthropogenic factors mixed with the contribution from the natural sources alters the optical properties and the life time of clouds in the region. The associated perturbations in radiative balance have a significant impact on the meteorological parameters and this in turn determines the precipitation forming process. Therefore, any change in weather which disturbs the normal hydrological pattern is alarming in the socio‐economic point of view. Hence, the main focus of this work is to determine the variation in transport and distribution of aerosols in the region and to understand the interaction of these aerosols with meteorological parameters and cloud properties. |
| Description: | Department of Atmospheric Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2764 |
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| Dyuthi-T0787.pdf | (6.630Mb) |
| Abstract: | The main purpose of the thesis is to improve the state of knowledge and understanding of the physical structure of the TMCS and its short range prediction. The present study principally addresses the fine structure, dynamics and microphysics of severe convective storms.The structure and dynamics of the Tropical cloud clusters over Indian region is not well understood. The observational cases discussed in the thesis are limited to the temperature and humidity observations. We propose a mesoscale observational network along with all the available Doppler radars and other conventional and non—conventional observations. Simultaneous observations with DWR, VHF and UHF radars of the same cloud system will provide new insight into the dynamics and microphysics of the clouds. More cases have to be studied in detail to obtain climatology of the storm type passing over tropical Indian region. These observational data sets provide wide variety of information to be assimilated to the mesoscale data assimilation system and can be used to force CSRM.The gravity wave generation and stratosphere troposphere exchange (STE) processes associated with convection gained a great deal of attention to modem science and meteorologist. Round the clock observations using VHF and UHF radars along with supplementary data sets like DWR, satellite, GPS/Radiosondes, meteorological rockets and aircrafl observations is needed to explore the role of convection and associated energetics in detail. |
| Description: | Department of Atmospheric Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2985 |
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| Dyuthi-T0965.pdf | (30.03Mb) |
Now showing items 1-9 of 9
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