A model of the Algol type close binary TT hydrae     

A. G. Kulkarni  K. D. Abhyankar 《Journal of Astrophysics and Astronomy》1981,2(2):119-132

UBV photometric observations and elements of TT Hydrae obtained by Kulkarni and Abhyankar (1980) are combined with the radial velocity curve of Popper (1979, personal communication) to derive the absolute dimensions and. a model of this important Algol system. While the photometric ratios of radii inV andB are in agreement givingk = 0.3812 for a limb darkening coefficient ofx = 0.6, application of Irwin’s (1947) method givesx = 0.4 forU. The primary is found to be a main sequence Al V star of mass 2.61M _⊙ and radius 2.01 R_⊙, and the secondary is classified as a Kl III star of mass 0.70M _⊙ and radius 5.33R _⊙. The observed Fourier coefficients for the light outside the eclipse agree with those calculated from theory for the reflection and ellipticity effects. The system shows an ultraviolet excess of 0.5 to 0.6 magnitudes during primary eclipse, which is attributed to an asymmetric circumstellar distribution of matter around the primary. The evolutionary status of the secondary, which does not appear to fill its Roche lobe completely, is discussed.  相似文献   

XX Cam—The Inactive R CrB star     

I. Kameswara Rao  N. M. Ashok  P. V. Kulkarni 《Journal of Astrophysics and Astronomy》1980,1(1):71-78

Infrared observations obtained six years apart of the R CrB type star XX Cam do not show any infrared excess, unlike all the other members of the class. The observed colours match a 7000 K black body energy distribution quite well. From the year 1898 till todate, apparently XX Cam has undergone only one visual light minimum in 1940. The lack of infrared excess, the abundance peculiarities and further lack of small amplitude light variations with periods of few tens of days, which are characteristic of R CrB type stars, are discussed in terms of theoretical pulsation models of helium stars.  相似文献   

Vertical Variation of Madden-Jullian Oscillations in the Normal Monsoon Season as Revealed Through MST Radar Wind Data     

D. Narayana Rao  H. R. Singh  J. R. Kulkarni  A. Y. Chandrika  S. Vijaya Bhaskara Rao 《Meteorology and Atmospheric Physics》2000,73(1-2):55-59

Summary  Mesosphere-Stratosphere-Troposphere (MST) Radar wind data for the period June through September 1996 have been examined to study vertical variation of Madden-Jullian Oscillations in wind and eddy kinetic energy (eke) in the normal monsoon season. The domain of analysis in the vertical is from 6 to 20 km with a height resolution of 150 m. Fast-Fourier-Transformation (FFT) has been applied to zonal (u), meridional(v) components of wind to extract the Madden-Jullian oscillations and eke. There are three dominant modes viz., 50–70, 30–40 and 10–20 day periodicity, which contain considerable fraction of energy and show high degree of vertical variability. The peak amplitude of 50–70 day mode in u, 30–40 mode in v and eke were observed at 16–17 km just below the tropopause level. The peak amplitudes of 30–40 day mode in u and 50–70 day mode in v were found in the height region of 13–16 km. To understand the origin and propagation of these waves, wave energy is calculated. The wave energy is higher at tropospheric heights than at lower stratospheric heights indicating that the origin of these waves is in the troposphere, and a part of the energy leaks into the stratosphere. Received September 17, 1998/Revised September 26, 1999  相似文献   

Hydrogeological framework of the Deccan basalt groundwater systems, west-central India     

H. Kulkarni  S. B. Deolankar  A. Lalwani  B. Joseph  S. Pawar 《Hydrogeology Journal》2000,8(4):368-378

Deccan basalts of west-central India are hydrogeologically inhomogeneous rocks. A proper understanding of the physical framework of the basalts within which groundwater resides and moves is a key to the hydrogeology of these rocks. Two types of basalt, the vesicular amygdaloidal basalt and the compact basalt, occur as alternate layers in the volcanic pile. Although the rocks are generally inhomogeneous, structures in the basalt, such as sheet joints and vertical joints, serve as zones of groundwater flow. In the shallow subsurface, two groundwater systems are operative. Groundwater system A consists of a vesicular amygdaloidal basalt underlain by a compact basalt, whereas groundwater system B consists of a vesicular amygdaloidal basalt overlain by a compact basalt. Groundwater system A has a better developed network of openings and, as a consequence, this system has a higher transmissivity and storage coefficient than groundwater system B. Wells tapping groundwater system A have higher yields on average and irrigate more hectares of cropland than do wells tapping groundwater system B. This simple systems concept offers a practical methodology for understanding the geometry of the physical framework that contains groundwater in the Deccan basalts. The efficacy of the concept is in its widespread utility for the region. The concept may also be extrapolated to help understand the hydrogeology of deeper Deccan basalt groundwater systems.  相似文献   

Projected changes in South Asian summer monsoon by multi-model global warming experiments   总被引：1，自引：0，他引：1  

S. S. Sabade  Ashwini Kulkarni  R. H. Kripalani 《Theoretical and Applied Climatology》2011,103(3-4):543-565

South Asian summer monsoon (June through September) rainfall simulation and its potential future changes are evaluated in a multi-model ensemble of global coupled climate models outputs under World Climate Research Program Coupled Model Intercomparison Project (WCRP CMIP3) dataset. The response of South Asian summer monsoon to a transient increase in future anthropogenic radiative forcing is investigated for two time slices, middle (2031–2050) and end of the twenty-first century (2081–2100), in the non-mitigated Special Report on Emission Scenarios B1, A1B and A2 .There is large inter-model variability in the simulation of spatial characteristics of seasonal monsoon precipitation. Ten out of the 25 models are able to simulate space–time characteristics of the South Asian monsoon precipitation reasonably well. The response of these selected ten models has been examined for projected changes in seasonal monsoon rainfall. The multi-model ensemble of these ten models projects a significant increase in monsoon precipitation with global warming. The substantial increase in precipitation is observed over western equatorial Indian Ocean and southern parts of India. However, the monsoon circulation weakens significantly under all the three climate change experiments. Possible mechanisms for the projected increase in precipitation and for precipitation–wind paradox have been discussed. The surface temperature over Asian landmass increases in pre-monsoon months due to global warming and heat low over northwest India intensifies. The dipole snow configuration over Eurasian continent strengthens in warmer atmosphere, which is conducive for the enhancement in precipitation over Indian landmass. No notable changes have been projected in the El Niño–Monsoon relationship, which is useful for predicting interannual variations of the monsoon.  相似文献   

Performance of GCMs for seasonal prediction over India��a case study for 2009 monsoon     

Nachiketa Acharya  Sarat C. Kar  U. C. Mohanty  Makarand A. Kulkarni  S. K. Dash 《Theoretical and Applied Climatology》2011,105(3-4):505-520

The 2009 drought in India was one of the major droughts that the country faced in the last 100?years. This study describes the anomalous features of 2009 summer monsoon and examines real-time seasonal predictions made using six general circulation models (GCMs). El Ni?o conditions evolved in the Pacific Ocean, and sea surface temperatures (SSTs) over the Indian Ocean were warmer than normal during monsoon 2009. The observed circulation patterns indicate a weaker monsoon in that year over India with weaker than normal convection over the Bay of Bengal and Indian landmass. Skill of the GCMs during hindcast period shows that neither these models simulate the observed interannual variability nor their multi-model ensemble (MME) significantly improves the skill of monsoon rainfall predictions. Except for one model used in this study, the real-time predictions with longer lead (2- and 1-month lead) made for the 2009 monsoon season did not provide any indication of a highly anomalous monsoon. However, with less lead time (zero lead), most of the models as well as the MME had provided predictions of below normal rainfall for that monsoon season. This study indicates that the models could not predict the 2009 drought over India due to the use of less warm SST anomalies over the Pacific in the longer lead runs. Hence, it is proposed that the uncertainties in SST predictions (the lower boundary condition) have to be represented in the model predictions of summer monsoon rainfall over India.  相似文献   

Radio observations of a few giant sources     

C. Konar  D. J. Saikia  C. H. Ishwara-Chandra  V. K. Kulkarni 《Monthly notices of the Royal Astronomical Society》2004,355(3):845-854

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On the interpretation of the observed angular-size-flux-density relation for extragalactic radio sources     

V. K. Kapahi  V. K. Kulkarni  C. R. Subrahmanya 《Journal of Astrophysics and Astronomy》1987,8(1):33-50

The interpretation of the observed relation between median angular sizes (θ _m) of extragalactic radio sources and flux density at 408 MHz has been examined. The predictedθ _m-S relations based on well-observed strong sources in parent samples selected at 178 and 1400 MHz, and existing models of the evolving radio luminosity function can be made to fit the observed relation only by invoking cosmological evolution in linear sizes even for theq ₀ = 0 universe. Predictions based on a parent sample at 2.7 GHz are shown to overestimate the contribution of steep-spectrum, compact (SSC) sources in low-frequency samples unless the downward curvature in the spectra of such sources is taken into account. When approximate corrections are made for this effect, predictions based on the 2.7 GHz parent sample cannot obviate the need for linear size evolution as claimed in the literature.  相似文献   

An integrated flood inundation model for coastal urban watershed of Navi Mumbai,India     

A. T. Kulkarni  T. I. Eldho  E. P. Rao  B. K. Mohan 《Natural Hazards》2014,73(2):403-425

Most urban agglomerations located in the Mumbai coastal region in India are vulnerable to flooding due to increasing frequency of the short-duration heavy rainfall, by virtue of their location at foothills on one side and tidal variations on the other side. Steep slopes in the catchment ensure fast runoff and tidal variation adds to backwater effect in the drainage system, which together are favorable for flooding. The present study simulates the flood inundation due to heavy rainfall and high-tide conditions in a coastal urban catchment within Mumbai region with detention pond. Overland flow is modeled using a mass balance approach, which can adapt to hilly slopes and smoothly accommodate detention pond hydraulics. Dynamic wave channel routing based on finite element method captures the backwater effects due to tidal variation, and raster-based flood inundation model enables direct use of digital elevation model. The integrated model is capable of simulating detention pond hydraulics within the raster flood model for heavy rainfall events. The database required for the model is obtained from the geographical information system (GIS) and remote sensing techniques. Application of the integrated model to literature problems and the catchment of the study area for two non-flooding events gave satisfactory results. Further, the model is applied to an extreme rainfall event of July 26, 2005, coinciding with high-tide conditions, which revealed vulnerability of the area to flooding despite of an existing detention pond. A sensitivity analysis on the location of detention pond indicated that catchment response can be better governed by relocating the detention pond to upstream of existing detention pond especially when heavy rainfall events are becoming frequent.  相似文献   

About the variability in thunderstorm and rainfall activity over India and its association with El Niño and La Niña     

M. K. Kulkarni  J. V. Revadekar  Hamza Varikoden 《Natural Hazards》2013,69(3):2005-2019

Thunderstorms are of much importance in tropics, as this region is considered to have central role in the convective overturn of the atmosphere and play an important role in rainfall activity. It is well known that El Niño and La Niña are well associated with significant climate anomalies at many places around the globe. Therefore, an attempt is made in this study to analyze variability in thunderstorm days and rainfall activity over Indian region and its association with El Niño and La Niña using data of thunderstorm day’s for 64 stations well distributed all over India for the period 1981–2005 (25 years). It is seen that thunderstorm activity is higher and much variable during pre-monsoon (MAM) and southwest monsoon (JJAS) than the rest of the year. Positive correlation coefficients (CCs) are seen between thunderstorms and rainfall except for the month of June during which the onset of the southwest monsoon sets over the country. CCs during winter months are highly correlated. Composite anomalies in thunderstorms during El Niño and La Niña years suggest that ENSO conditions altered the patterns of thunderstorm activity over the country. Positive anomalies are seen during pre-monsoon (MAM) and southwest monsoon months (JAS) during La Niña years. Opposite features are seen in southwest monsoon during El Niño periods, but El Niño favors thunderstorm activity during pre-monsoon months. There is a clear contrast between the role of ENSO during southwest monsoon and post-monsoon on thunderstorm activity over the country. Time series of thunderstorms and precipitation show strong association with similarities in their year-to-year variation over the country.  相似文献