Surface sensible heat flux over a deep moist convective region and its interplay with synoptic and mesoscale features     

R. Pradhan  U. K. De  P. K. Sen 《Journal of Earth System Science》1994,103(3):353-367

The surface parameters are being evaluated using a methodology which considers the vertical temperature structure of MONTBLEX ’90. For this 30 metre micrometeorological tower data are utilised. In this process, a concept of isolated layers has been introduced. The parameters have been evaluated following two successive iterative processes to give a consistent value both in the flux-profile relation and the related similarity relation. The heat flux obtained using the present methodology, is then utilised to examine its interplay with the synoptic as well as mesoscale features. The existence of such an interplay is observed.  相似文献   

Impact of Doppler Radar Wind in Simulating the Intensity and Propagation of Rainbands Associated with Mesoscale Convective Complexes Using MM5-3DVAR System     

S. Abhilash  Someshwar Das  S. R. Kalsi  M. Das Gupta  K. Mohankumar  John P. George  S. K. Banerjee  S. B. Thampi  D. Pradhan 《Pure and Applied Geophysics》2007,164(8-9):1491-1509

Pre-monsoon rainfall around Kolkata (northeastern part of India) is mostly of convective origin as 80% of the seasonal rainfall is produced by Mesoscale Convective Systems (MCS). Accurate prediction of the intensity and structure of these convective cloud clusters becomes challenging, mostly because the convective clouds within these clusters are short lived and the inaccuracy in the models initial state to represent the mesoscale details of the true atmospheric state. Besides the role in observing the internal structure of the precipitating systems, Doppler Weather Radar (DWR) provides an important data source for mesoscale and microscale weather analysis and forecasting. An attempt has been made to initialize the storm-scale numerical model using retrieved wind fields from single Doppler radar. In the present study, Doppler wind velocities from the Kolkata Doppler weather radar are assimilated into a mesoscale model, MM5 model using the three-dimensional variational data assimilation (3DVAR) system for the prediction of intense convective events that occurred during 0600 UTC on 5 May and 0000 UTC on 7 May, 2005. In order to evaluate the impact of the DWR wind data in simulating these severe storms, three experiments were carried out. The results show that assimilation of Doppler radar wind data has a positive impact on the prediction of intensity, organization and propagation of rain bands associated with these mesoscale convective systems. The assimilation system has to be modified further to incorporate the radar reflectivity data so that simulation of the microphysical and thermodynamic structure of these convective storms can be improved.  相似文献   

Some observations from the data taken in and around Kharagpur during the onset of the monsoon, 1990     

R Pradhan  B Roy  U K De  D K Rakshit 《Journal of Earth System Science》1996,105(1):17-29

During MONTBLEX 1990, various observational platforms were operated at Kharagpur and the nearby Kalaikunda Air Base. Using the data from all the platforms, one can draw the following conclusions. The temperature and wind data obtained from various sensors have overall compatibility. Sodar wind data indicate the presence of a low level jet at around 300 m above ground. The inversion height may be evaluated from the vertical profile of the sodar back-scatter echo intensity. The sub-synoptic or synoptic scale convergence modulates the inversion height and the presence of cloud-base within the inversion height in turn modulates the sensible heat and momentum fluxes.  相似文献   

利用光学遥感数据、GIS及人工神经网络模型分析区域滑坡灾害(英文)   总被引：3，自引：0，他引：3  

Biswajeet Pradhan Saro Lee 《地学前缘》2007,14(6):143-152

用光学遥感数据和地理信息系统(GIS)分析了马来西亚Selangor地区的滑坡灾害。通过遥感图像解译和野外调查,在研究区内确定出滑坡发生区。通过GIS和图像处理,建立了一个集地形、地质和遥感图像等多种信息的空间数据库。滑坡发生的因素主要为:地形坡度、地形方位、地形曲率及与排水设备距离;岩性及与线性构造距离;TM图像解译得到的植被覆盖情况;Landsat图像解译得到的植被指数;降水量。通过建立人工神经网络模型对这些因素进行分析后得到滑坡灾害图:由反向传播训练方法确定每个因素的权重值,然后用该权重值计算出滑坡灾害指数,最后用GIS工具生成滑坡灾害图。用遥感解译和野外观测确定出的滑坡位置资料验证了滑坡灾害图,准确率为82.92%。结果表明推测的滑坡灾害图与滑坡实际发生区域足够吻合。  相似文献   

Cylindrically symmetric inhomogeneous universe with electromagnetic field in string cosmology     

Anirudh Pradhan  Anju Rai  Sheel Kumar Singh 《Astrophysics and Space Science》2007,312(3-4):261-265

Cylindrically symmetric inhomogeneous string cosmological model in presence of electromagnetic field is investigated. We have assumed that F ₂₃ is the only non-vanishing component of F _ij . To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ ¹ ₁ of the shear tensor σ ⁱ _j . The physical and geometric aspects of the model are also discussed.   相似文献   

OPserver: interactive online computations of opacities and radiative accelerations     

C. Mendoza  M. J. Seaton  P. Buerger  A. Bellorín  M. Meléndez †  J. González  L. S. Rodríguez  F. Delahaye  E. Palacios  A. K. Pradhan  C. J. Zeippen 《Monthly notices of the Royal Astronomical Society》2007,378(3):1031-1035

Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client–server architecture and transcribed as a subroutine library. This implementation increases efficiency in stellar modelling where element stratification due to diffusion processes is depth dependent, and thus requires repeated fast opacity re-estimates. Three user modes are provided to fit different computing environments, namely, a web browser, a local workstation and a distributed grid.  相似文献   

High-temperature behaviour of the helium-like KαG ratio: the effect of improved recombination rate coefficients for calcium, iron and nickel     

J. Oelgoetz  C. J. Fontes  H. L. Zhang  M. Montenegro  S. N. Nahar  A. K. Pradhan 《Monthly notices of the Royal Astronomical Society》2007,382(2):761-769

  相似文献   

Five dimensional universe model with variable cosmological term Λ and a big bounce     

G. S. Khadekar  Vaishali Kamdi  Anirudh Pradhan  Saeed Otarod 《Astrophysics and Space Science》2007,310(1-2):141-147

We assume the four dimensional induced matter of the 5D Ricci flat bouncing cosmological solution contains a perfect fluid. The big bounce singularity of simple 5D cosmological model is studied with the cosmological term Λ=α ρ and Λ=β H ² where α and β are constants and ρ and H are respectively energy density and Hubble parameter. This big bounce singularity is found to be an event horizon at which the scale factor and mass density of the universe are finite, while the pressure is infinite.   相似文献   

Effect of Lime Stabilized Soil Cushion on Strength Behaviour of Expansive Soil     

Jagadish Prasad Sahoo  Pradip Kumar Pradhan 《Geotechnical and Geological Engineering》2010,28(6):889-897

An experimental investigation was undertaken to study the effects of lime-stabilized soil-cushion on the strength behavior of expansive soil. In the present investigation, a series of laboratory tests (Unconfined compression tests and CBR tests) were conducted on both expansive soil alone and expansive soil cushioned with lime-stabilized non-expansive cohesive soil. Lime contents of 2, 4, 6, 8 and 10% by dry weight of cohesive non-swelling soil was used in the stabilized soil cushion. Both expansive soil and lime stabilized soil cushion were compacted to Standard Proctor’s optimum condition with thickness ratio 2:1. Tests on cushioned expansive soils were conducted at different curing and soaking periods i.e., 7, 14, 28 and 56 days. The test results revealed that maximum increase in strength was achieved after 14 days of curing or soaking period with 8% of lime content.  相似文献   

Mechanism and geochemical implications of the Late Holocene organic carbon burial event: an example from the southwest coast of India   总被引：1，自引：0，他引：1  

B. Ajaykumar  Mahesh Mohan  M. S. Shylesh Chandran  K. K. Jayasooryan  K. S. Unni  A. P. Thomas 《Environmental Earth Sciences》2010,59(7):1409-1416

Carbonaceous clay found in the palaeo-deposits of Meenachil River basin was analysed for the total organic carbon, nitrogen and textural characters. Radiocarbon dating of this clay formation and the embedded carbonized wood fragments was also done. The values obtained for the organic carbon, nitrogen and C/N ratio of the carbonaceous clay exhibited a very remarkable range, suggestive of different environmental conditions of formation. It is evident from the present study that since the lignin and cellulose are the dominant components of terrestrial higher plants, allochthonous and submerged organic matter have high C/N ratio. The radio carbon dating of the sediment and wood samples suggested that the palaeo-deposits of Meenachil River basin were formed as result of many transgrassive–regressive episodes, which had started even before the formation of Vembanad Lake. The formation of carbonaceous clay, as found sandwiched in palaeo-deposits, was due to the global eustatic sea-level fluctuations and tectonism.  相似文献