Effects of cloud types on cloud-radiation interaction over the Asian monsoon region     

Bipasha Paul Shukla  V. Sathiyamoorthy  P. K. Pal  P. C. Joshi 《Theoretical and Applied Climatology》2009,97(3-4):287-295

This paper quantifies the sensitivity of radiation budget quantities to different cloud types over the Asian monsoon region using the International Satellite Cloud Climatology Project. Multiple regression was used to estimate the radiative effects of individual cloud type. It was observed that the regression performed better when the solution was constrained with clear sky fluxes, which is evident by an improvement in R ² statistics. The sensitivity coefficients calculated for the Asian monsoon region reveal that, while the LWCRCF and SWCRF will be most vulnerable to changes in cloud cover of deep convective clouds, NETCRF will be susceptible to changes in the nimbostratus clouds. Although the cloud radiative forcing of individual cloud types are found to be similar in sign to previous global findings, their magnitudes are found to vary. It is seen that cirrus clouds play an important role in governing the radiative behavior of this region.  相似文献   

Discovery of three new pulsars in a 610-MHz pulsar survey with the GMRT     

B. C. Joshi  M. A. McLaughlin  A. G. Lyne  D. A. Ludovici  N. A. Pawar  A. J. Faulkner  D. R. Lorimer  M. Kramer  M. L. Davies 《Monthly notices of the Royal Astronomical Society》2009,398(2):943-948

We report on the discovery of three new pulsars in the first blind survey of the north Galactic plane  (45° < l < 135°; | b | < 1°)  with the Giant Meterwave Radio telescope (GMRT) at an intermediate frequency of 610 MHz. The survey covered 106 deg² with a sensitivity of roughly 1 mJy to long-period pulsars (pulsars with period longer than 1 s). The three new pulsars have periods of 318, 933 and 1056 ms. Their timing parameters and flux densities, obtained in follow-up observations with the Lovell Telescope at Jodrell Bank and the GMRT, are presented. We also report on pulse nulling behaviour in one of the newly discovered pulsars, PSR J2208+5500.  相似文献   

Study of Distribution and Asymmetry of Solar Active Prominences during Solar Cycle 23     

Navin Chandra Joshi  Neeraj Singh Bankoti  Seema Pande  Bimal Pande  Kavita Pandey 《Solar physics》2009,260(2):451-463

In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP) for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West (E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical study shows that the N – S asymmetry is more significant then the E – W asymmetry.  相似文献   

The role of fluids in the formation of talc deposits of Rema area,Kumaun Lesser Himalaya     

Rajesh Sharma  Prabha Joshi  P. D. Pant 《Journal of the Geological Society of India》2009,73(2):237-248

Talc deposits of Rema area in the Kumaun Inner Lesser Himalaya are hosted within high magnesium carbonates of the Proterozoic Deoban Formation. These deposits occur as irregular patches or pockets mainly within magnesite bodies, along with impurities of magnesite, dolomite and clinochlore. Textures represent different phases of reactions between magnesite and silica to produce talc. Petrography, XRD and geochemistry reveal that the talc has primarily developed at the expense of magnesite and silica, leaving dolomite largely un-reacted. Early fluid inclusions in magnesite and dolomite associated with talc are filled with H₂O+NaCl+KCl ± MgCl₂ ± CaCl₂ fluids, which represent basin fluid system during diagenesis of carbonates. Their varied degree of re-equilibration was although not pervasive but points to increased burial, and hence requires careful interpretation. H₂O-CO₂ fluid with XCO₂ between 0.06 and 0.12 was equilibrated with talc formation. The reaction dolomite+quartz → talc was not extensive because T-X_CO2 was not favourable, and talc was developed principally after magnesite+quartz.  相似文献   

Five dimensional Bianchi type-V cosmological models described by a binary mixture of perfect fluid and dark energy with Λ-term     

Shantanu Kumar Biswal  Santosh Kumar Agarwalla  Munesh Chandra Adhikary 《Astrophysics and Space Science》2012,337(2):645-650

Some recent experimental observations have been shown that inclusion of electron collisions damping in inertial Alfvén wave (IAW) dynamics may be important for laboratory as well as space plasmas. This paper presents the numerical simulation of model equation governing the nonlinear dynamics of IAW in low-beta plasmas. When the nonlinearity arises due to the ponderomotive force and Joule heating driven density perturbations, the model equation turns out to be a modified nonlinear Schr?dinger equation (MNLS). The electron collisions are introduced only in the electron momentum equation. The damped localized structures of IAW with sidebands are obtained. Also, the effect of collisional damping on power spectra of magnetic fluctuations with different scaling laws has been studied. These turbulent structures may be responsible for particle acceleration in laboratory and space plasmas.  相似文献   

Software for interactively visualizing solar vector magnetograms of udaipur solar observatory     

Sanjay Gosain  Sanjiv Tiwari  Jayant Joshi  P. Venkatakrishnan 《Journal of Astrophysics and Astronomy》2008,29(1-2):107-111

The Solar Vector Magnetograph (SVM) at Udaipur Solar Observatory saw its first light in April 2005. The retrieval of vector fields from the imaging spectro-polarimetric observational data requires a substantial amount of computer post-processing. The GUI-based data reduction and analysis software have been developed to make the data processing pipeline user-friendly and less time-consuming. In this paper we describe these software packages.  相似文献   

A possible disk mechanism for the 23-day QPO in Mkn 501     

J.H. Fan  F.M. Rieger  T.X. Hua  U.C. Joshi  J. Li  Y.X. Wang  J.L. Zhou  Y.H. Yuan  J.B. Su  Y.W. Zhang 《Astroparticle Physics》2008,28(6):508-515

  相似文献   

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir,Borneo:Implications for reservoir characterization and flow simulation     

Numair A.Siddiqui  Mu.Ramkumar  Abdul Hadi A.Rahman  Manoj J.Mathew  M.Santosh  Chow W.Sum  David Menier 《地学前缘(英文版)》2019,10(3):957-971

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2 D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo.Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics.These proportions were then enumerated in terms of static digital outcrop model(DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone(porosity 21.25%-41.2%and permeability 1265.20-5986.25 mD) and moderate quality sandstone(porosity 10.44%-28.75% and permeability 21.44-1023.33 mD). Whereas, in more heterolithic sandstone(wavy-to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone(porosity 3.4%-12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.  相似文献   

Analysis of urban built-up areas and surface urban heat island using downscaled MODIS derived land surface temperature data     

Sandip Mukherjee  P. K. Joshi  R. D. Garg 《国际地球制图》2017,32(8):900-918

Regional scale urban built-up areas and surface urban heat islands (SUHI) are important for urban planning and policy formation. Owing to coarse spatial resolution (1000 m), it is difficult to use Moderate Resolution Imaging Spectroradiometer (MODIS) Land surface temperature (LST) products for mapping urban areas and visualization, and SUHI-related studies. To overcome this problem, the present study downscaled MODIS (1000 m resolution)-derived LST to 250 m resolution to map and visualize the urban areas and identify the basic components of SUHI over 12 districts of Punjab, India. The results are compared through visual interpretation and statistical procedure based on similarity analysis. The increased entropy value in the downscaled LST signifies higher information content. The temperature variation within the built-up and its environs is due to difference in land use and is depicted better in the downscaled LST. The SUHI intensity analysis of four cities (Ludhiana, Patiala, Moga and Vatinda) indicates that mean temperature in urban built-up core is higher (38.87 °C) as compared to suburban (35.85 °C) and rural (32.41 °C) areas. The downscaling techniques demonstrated in this paper enhance the usage of open-source wide swath MODIS LST for continuous monitoring of SUHI and urban area mapping, visualisation and analysis at regional scale. Such initiatives are useful for the scientific community and the decision-makers.  相似文献   

Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations     

Joshi  Sneh  Kar  Sarat C. 《Theoretical and Applied Climatology》2018,131(3-4):1449-1464

Theoretical and Applied Climatology - Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea...  相似文献