ETD at Indian Institute of Science
Repository of Theses and Dissertations of Indian Institute of Science, Bangalore, India. The repository has been developed to capture, disseminate and preserve research theses of Indian Institute of Science.
Centre for Atmospheric and Oceanic Sciences (caos)
Mostrando recursos 1 - 20 de 34
Assesment Of Air Quality And Anthropogenic Aerosol Fraction Over India Using Observations And Model - Srivastava, Nishi
Air quality degradation is emerging to be an issue of major concern in India. Recent investigations have shown that anthropogenic aerosols have significant impact on climate as well as on health. In fourth assessment report of IPCC, it has been mentioned that radiative effects of anthropogenic aerosols constitute one of the major uncertainties in assessing aerosol-induced climate impact. In addition to climate impacts, aerosol causes respiratory and cardiovascular diseases, air quality degradation, acidification of aquatic and terrestrial ecosystems. Characterization of anthropogenic aerosol fraction (defined as the fraction of anthropogenic aerosols to composite aerosols) is an appealing topic of research in...
Observed Subseasonal Variability Of Temperarture And Salinity In The Tropical Indian Ocean - Parampil, Sindu Raj
Subseasonal variability of tropical Indian Ocean sea surface temperature is thought to influence the active-break cycle of the Asian monsoon. There are several open questions related to the role of surface fluxes, large-scale ocean circulation and subsurface ocean processes in the subseasonal variability of upper ocean temperature. We present a unified study of the subseasonal (2-90 day) variability of surface heat flux and upper ocean temperature and salinity throughout the tropical Indian Ocean in all seasons. We focus on the relation between surface fluxes and ocean response using a new satellitebased
daily heat flux. The role of ocean processes (advection, entrainment...
Investigation Of Aerosol Characteristics Over Inland, Coastal And Island Locations In India - Vinoj, V
This thesis is based on measurements of aerosol optical and microphysical properties made at inland, coastal and island locations in India. Aerosol vertical distribution measurements have also been made both using surface based and aircraft borne instruments. In addition to these, satellite based measurements (MODIS and OMI) have also been used to estimate regional aerosol radiative forcing over the oceanic regions around India.
The measurements at an inland, continental, urban location reveals the large effect of anthropogenic activities on aerosol characteristics at surface and the atmospheric vertical column. A clear seasonality is observed in aerosol optical and microphysical properties as...
Cloud Properties Over SHAR Region Derived From Weather RADAR Data - Bhattacharya, Anwesa
Weather radars are increasingly used for the study of clouds, understanding the precipitation systems and also for forecasting very short range weather (one hour to a few hours). Now, Doppler Weather Radar (DWR) data are available in India and it is possible to study cloud properties at fine temporal and spatial scales. Radar is a complex system and calibration of a radar is not an easy job. But derived cloud properties strongly depend on the absolute magnitude of the reflectivity. Therefore, there is a need to check how data from two or more radars compare if they measure a common...
Fine-Scale Structure Of Diurnal Variations Of Indian Monsoon Rainfall : Observational Analysis And Numerical Modeling - Sahany, Sandeep
In the current study, we have presented a systematic analysis of the diurnal cycle of rainfall over the Indian region using satellite observations, and evaluated the ability of the Weather Research and Forecasting Model (WRF) to simulate some of the salient features of the observed diurnal characteristics of rainfall. Using high resolution simulations, we also investigate the underlying mechanisms of some of the observed diurnal signatures of rainfall. Using the Tropical Rain-fall Measuring Mission (TRMM) 3-hourly, 0.25 ×0.25 degree 3B42 rainfall product for nine years (1999-2007), we extract the finer spatial structure of the diurnal scale signature of Indian summer...
Impact Of Dynamical Core And Diurnal Atmosphere Occean Coupling On Simulation Of Tropical Rainfall In CAM 3.1, AGCM - Kumar, Suvarchal
In first part of the study we discuss impact of dynamical core in simulation of tropical rainfall. Over years many new dynamical cores have been developed for atmospheric models to increase efficiency and reduce numerical errors. CAM3.1 gives an opportunity to study the impact of the dynamical core on simulations with its three dynamical cores namely Eulerian spectral(EUL) , Semilagrangian dynamics(SLD) and Finite volume(FV) coupled to a single parametrization package. A past study has compared dynamical cores of CAM3 in terms on tracer transport and has showed advantages using FV in terms of tracer transport. In this study we compare...
Biennial Oscillation Of Indian Summer Monsoon And Global Surface Climate In The Present Decade - Menon, Arathy
The ENSO-monsoon system is known to have a biennial component. Here we show using high resolution satellite data, mainly daily rainfall and sea surface temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM), and daily scatterometer surface winds from QuickSCAT, that there is a clear biennial oscillation (TBO) in summer monsoon rainfall over Central India – Bay of Bengal (Cl-BoB) and the far west Pacific in the period 1999-2005. Summer (JJAS) mean rainfall oscillates between high and low values in alternate years; the rainfall is high in the odd years 1999, 2001, 2003, and 2005, and low in even years...
Changes In The Duration-Depth Characteristics Of Indian Monsoon Rainfall During 1951-2000 - Ratan, Ram
Several previous studies have found that various characteristics of the Indian monsoon rainfall have shown secular changes over the past century. In this study, using a gridded (1degree) daily rainfall dataset, we analyse the spatio-temporal characteristics of the intensity and duration of monsoon (June through September) rainfall for secular changes over the last 50 years. The characteristics of the duration of rain events are described by wet and dry spells. A wet/dry spell is defined as a period of consecutive days with rainfall above/below a particular threshold. We choose to use a threshold that is a function of the local...
A Variable Resolution Global Spectral Method With Finer Resolution Over The Tropics - Janakiraman, S
Variable resolution method helps to study the local scale phenomenon of interest within the context of global scale atmosphere/ocean dynamics. Global spectral methods based on spherical harmonics as basis functions are known to resolve a given function defined on the sphere, in an uniform manner. Though known for its mathematical elegance and higher order accuracy, global spectral methods are considered to be restrictive for developing mesh-refinement strategies. The only mesh refinement strategy available until now is due to the pioneering work of F. Schmidt. Schmidt transformation can study only one region with higher resolution.
The study of tropical dynamics is...
Aerosol Absorption And Source Characteristics Over Different Environments - Sindhu, Kapil Dev
Extremely fine liquid droplets or solid particles, those remain suspended in the air, are known as aerosols. They are produced by natural sources and anthropogenic activities. Several types of aerosols produced by different processes are present in the atmosphere and every type of aerosol species exhibit different types of physical and chemical properties. Though making up only a small fraction of atmospheric mass aerosols are capable of altering Earth’s climate by scattering and absorbing incoming solar radiation and absorbing outgoing radiation. Adding to the complexity, they can act as cloud condensation nuclei and modify cloud properties.
Major objective of this thesis...
An Assessment Of The Simulation Of Monsoon And Inter Tropical Convergence Zone In Coupled Ocean-Atmosphere Models - Vidyunmala, V
Monsoons and Intertropical Convergence Zones (ITCZ) exhibit variability at various temporal and spatial scales. The temporal scale of variability encompasses scales from the intraseasonal through interannual to interdecadal time scales. Anthropogenic climate change can also have an impact on ITCZ and monsoons. Thus it is necessary to assess the ability of coupled ocean atmospheric models (commonly known as AOGCM) to simulate these aspects of variability of tropical climate. This has been studied with simulations from 20 AOGCMs and their AGCM from IPCCAR4 archive. In addition, we have used our own 100 year simulation with CCSM2 and also simulations with its...