Recursos de colección

ETD at Indian Institute of Science (2.482 recursos)

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 39

  1. Fine-Scale Structure Of The Diurnal Cycle Of Global Tropical Rainfall

    Chattopadhyay, Bodhisattwa
    The fine-scale structure of global (30N-30S) tropical rainfall is characterised using 13 years (1998-2010) of 3-hourly and daily, 0.25-degree Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product. At the outset, the dominant timescales present in rainfall are identified. Specifically, the Fourier spectrum (in time) is estimated in two ways (a) spectrum of spatially averaged (SoSA) rainfall; and (b) spatial average of the spectrum (SAoS) of rainfall at each grid point. This procedure is applied on rainfall at the 3-hourly and daily temporal resolutions. Both estimates of the spectrum show the presence of a very strong seasonal cycle. But, at subseasonal...

  2. Scaling Characteristics Of Tropical Rainfall

    Madhyastha, Karthik
    We study the space-time characteristics of global tropical rainfall. The data used is from the Tropical Rainfall Measuring Mission (TRMM) and spans the years 2000-2009. Using anomaly fields constructed by removing a single mean and by subtracting the climatology of the ten year dataset, we extract the dominant modes of variability of tropical rainfall from an Empirical Orthogonal Function (EOF) analysis. To our knowledge, this is the first attempt at applying the EOF formal-ism to high spatio-temporal resolution global tropical rainfall. Spatial patterns and temporal indices obtained from the EOF analysis with single annual mean removed show large scale patterns...

  3. Role Of Sea Surface Temperature Gradient In Intraseasonal Oscillation Of Convection In An Aquaplanet Model

    Das, Surajit
    In this thesis we examine intra-seasonal oscillations (ISO) in the aqua-planet setup of the Community Atmospheric Model (CAM) version 5.1, mainly based on July and January climatological sea surface temperature (SST). We investigate mainly two questions -what should be the SST distribution for the existence of (a) northward moving ISO in summer, and (b) eastward moving MJO-like modes in winter. In the first part of the thesis we discuss the northward propagation. A series of experiments were performed with zonally symmetric and asymmetric SST distributions. The basic lower boundary condition is specified from zonally averaged observed July and January SST....

  4. Variation Of Marine Boundary Layer Characteristic Over Bay Of Bengal And Arabian Sea

    Rai, Deepika
    The atmospheric boundary layer (ABL) is the lowest layer of the atmosphere where surface effects are felt on time scales of about an hour. While its properties are determined by the surface characteristics, season and synoptic conditions, they in turn determine convective cloud properties and are required for the representation of cloud processes in atmospheric models. Further, interaction of the ABL with the surface layer of the ocean is a key component of ocean-atmosphere coupling. ABL characteristics over ocean surrounding the sub-continent become very important for understanding the monsoon processes during the monsoon season because the roots of many monsoon...

  5. Water Soluble Inorganic Aerosol Chemical Characteristics Over An Urban Site In Southern India

    Nair, Aswathy V
    Aerosol are solid or liquid particles suspended in the atmosphere ranging in size from 10 3 to 102 m. Aerosol influence both the regional and global climate of the earth by its direct and indirect effect. Role of atmospheric aerosols on the radiative forcing of atmosphere is a matter of serious research for past few decades and still it remains highly uncertain as acknowledged by Intergovernmental Panel on Climate Change. Heterogeneous nature of aerosol both spatially and temporally makes it more complex in estimating radiative forcing compared to that of greenhouse gases. Compounding to the existing difficulty in determining the...

  6. 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...

  7. Simulation Of Monsoon Precipitation And Its Variation By Atmospheric General Circulation Models

    Surendran, Sajani

  8. 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...

  9. Simulations Of Tropical Surface Winds : Seasonal Cycle And Interannual Variability

    Hameed, Saji N

  10. The Bay Of Bengal Circulation In An Ocean General Circulation Model

    Vinayachandran, P N

  11. A Two Dimensional Plume In A Rotating Fluid

    Raju, Jampana V S

  12. Difference In Land-Ocean Response And The Regional Impact Of Geo-Engineering

    Nag, Bappaditya

  13. Intraseasonal Variability Of The Northeast Indian Ocean Circulation In An Ocean Model

    Senan, Retish

  14. Mixed Layer Thermodynamics Of The Southeastern Arabian Sea Using ARMEX Observations

    Parampil, Sindu Raj

  15. The Role Of Water Vapor In The Clear-sky Greenhouse Effect In The Tropics

    Acharya, Sumedh

  16. Retrieval Of Dust Aerosols Using METEOSAT Infrared Radiance

    Singh, Deepshikha

  17. 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...

  18. 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...

  19. 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...

  20. 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...

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