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21.
Impact of satellite soundings on the simulation of heavy rainfall associated with tropical depressions 总被引:1,自引:1,他引:0
The present study is carried out to examine the impact of temperature and humidity profiles from moderate resolution imaging
spectroradiometer (MODIS) or/and atmospheric infrared sounder (AIRS) on the numerical simulation of heavy rainfall events
over the India. The Pennsylvania State University–National Centre for Atmospheric Research fifth-generation mesoscale model
(MM5) and its three-dimensional variational (3D-Var) assimilation technique is used for the numerical simulations. The heavy
rainfall events occurred during October 26–29, 2005, and October 27–30, 2006, were chosen for the numerical simulations. The
results showed that there were large differences observed in the initial meteorological fields from control experiment (CNT;
without satellite data) and assimilation experiments (MODIS (assimilating MODIS data), AIRS; (assimilating AIRS data); BOTH
(assimilating MODIS and AIRS data together)). The assimilation of satellite data (MODIS, AIRS, and BOTH) improved the predicted
thermal and moisture structure of the atmosphere when compared to CNT. Among the experiments, the predicted track of tropical
depressions from MODIS was closer to the observed track. Assimilation of MODIS data also showed positive impact on the spatial
distribution and intensity of predicted rainfall associated with the depressions. The statistical skill scores obtained for
different experiments showed that assimilation of satellite data (MODIS, AIRS, and BOTH) improved the rainfall prediction
skill when compared to CNT. Root mean square error in quantitative rainfall prediction is less in the experiment which assimilated
MODIS data when compared to other experiments. 相似文献
22.
D. Bhattacharya G. B. Joshi Rakesh Sharma 《Journal of the Geological Society of India》2011,78(1):57-62
Several small lensoidal bodies of felsic volcanics are exposed in a curvilinear pattern within the brecciated granitoids of
Bundelkhand Gneissic Complex (BGC) at Mohar. Sub-surface data reveals extensive presence of these felsic volcanics below the
sediment of Vindhyan Supergroup. It occurs like a sheet with thickness varying from 12 m to 134 m. Its lateral extent has
been traced upto 4.8 km. Multiple flows of felsic magma are identified based on colour, granularity, cross cutting relations
and cyclic distribution of multiple vesicular bands along the entire thickness of felsic magma. The felsic rock contains upto
13.21% K2O. Chemical composition of these felsic volcanics varies across the column. Petrographically and chemically all these felsic
volcanics are identified as rhyolite or rhyolite tuff. 相似文献
23.
The impact of realistic representation of sea surface temperature (SST) on the numerical simulation of track and intensity
of tropical cyclones formed over the north Indian Ocean is studied using the Weather Research and Forecast (WRF) model. We
have selected two intense tropical cyclones formed over the Bay of Bengal for studying the SST impact. Two different sets
of SSTs were used in this study: one from TRMM Microwave Imager (TMI) satellite and other is the weekly averaged Reynold’s
SST analysis from National Center for Environmental Prediction (NCEP). WRF simulations were conducted using the Reynold’s
and TMI SST as model boundary condition for the two cyclone cases selected. The TMI SST which has a better temporal and spatial
resolution showed sharper gradient when compared to the Reynold’s SST. The use of TMI SST improved the WRF cyclone intensity
prediction when compared to that using Reynold’s SST for both the cases studied. The improvements in intensity were mainly
due to the improved prediction of surface latent and sensible heat fluxes. The use of TMI SST in place of Reynold’s SST improved
cyclone track prediction for Orissa super cyclone but slightly degraded track prediction for cyclone Mala. The present modeling
study supports the well established notion that the horizontal SST gradient is one of the major driving forces for the intensification
and movement of tropical cyclones over the Indian Ocean. 相似文献
24.
Rakesh K. Malik Pradeep Gothoskar P. K. Manohran G. Swarup K. Subramanian V. Balasubramanian 《Journal of Astrophysics and Astronomy》1995,16(3-4):393-398
Jupiter flux at 327 MHz was monitored using the Ooty radio telescope from July 12th to July 29th during the collision of comet
Shoemaker-Levi 9 with Jupiter. Flux was found to increase steadily from July 17th to July 26th by ∼ 2–5 Jy, after which it
declined to its pre-event value. The comparison of 327 MHz observations with those at 840 MHz and 2240 MHz indicates that
the enhancement was mainly due to the increased synchrotron emission and the contribution of thermal emission was very small
at metric-decimetric frequencies. The enhancement in radio emission was found to be more at 840 MHz than at 327 or 2240 MHz.
The steepening of the spectrum between 327 and 840 MHz as well as between 2240 and 840 MHz was also noted. 相似文献
25.
26.
The inelastic response of one-storey, asymmetric-plan systems to two excitations is presented and analysed with the objective of identifying the influence of system parameters: uncoupled lateral vibration period, uncoupled torsional-to-lateral frequency ratio, stiffness eccentricity, relative values of the strength and stiffness eccentricities, and yield factor. Furthermore, the influence of yielding on the response of asymmetric-plan systems is examined. In particular, we determine whether the well known relationship between the response of yielding and elastic single-degree-of-freedom (SDF) systems is also applicable to asymmetric-plan systems. 相似文献
27.
Anumeha Shukla Rakesh Chandra Mehrotra 《Journal of the Geological Society of India》2016,87(5):520-524
Thick lignite deposits on the western margin of India were preserved on account of thick vegetation which got buried underneath due to tectonic activities that occurred in northwestern part of India during the early Palaeogene. Study of the fossil flora preserved in these beds is important to deduce the palaeoclimate of the region. Therefore, a field work was undertaken to collect plant fossils from the Tarkeshwar lignite mine, Surat district, Gujarat (western India) which is still unexplored as far as the plant mega-remains are concerned. A fossil wood is systematically described from the Cambay Shale Formation of the mine considered to be of early Eocene in age. It shows close affinities with Holigarna (Anacardiaceae), particularly with H. beddomei and H. grahamii. This genus is evergreen in nature and grows in the Indo-Malayan region, while both the modern analogues of the fossil are endemic to semi-evergreen to evergreen forests ofWestern Ghats, south India, located at the equator. This not only confirms the palaeolatitudinal position of the Indian subcontinent at the equator during the early Palaeogene, but also indicates the presence of equatorial rain forest in the Indian subcontinent during the period. Based on the timetree, Sapindales started to diverge in the early Palaeocene (62–57 Ma) as its oldest fossil is from the K-Pg boundary. Discovery of the present anacardiaceous fossil (belonging to Sapindales) from the early Eocene strengthens the above phylogenetic view. 相似文献
28.
Landslides - The reliable landslide hazard assessment entails a robust understanding of frequency-magnitude analysis of the landslide inventory. Previous studies proposed that the landslide... 相似文献
29.
R. Nagendra Satish J. Patel Rakesh Deepankar A. N. Reddy 《Journal of the Geological Society of India》2010,76(5):525-532
Well preserved ichnofossils were found in Kulakkalnattam sandstone exposed at Kulakkalnattam stream in Ariyalur area, Cauvery Basin. It consists of infaunal structures of both suspension and deposit feeders. Five ichnofossils are present in a fine to coarse grain sandstone which includes Ophiomorpha, Palaeophycus, Planolites Skolithos, and Thalassinoides. The study infers that ichnofossils Skolithos and Ophiomorpha are infaunal colonization of the suspension feeders in high energy condition in shifting substrate, whereas Thalassinoides and Planolites-Palaeophycus ichnofossils indicate infaunal deposit feeders living at the sediment-sediment interface in low to moderate energy conditions. Furthermore, the abundance and diversity of the trace fossils indicates there was alternatively fluctuations in energy conditions which lead to development of Skolithos and Cruziana ichnofacies type condition during the deposition of Kulkkallanattam sandstone in foreshore-shoreface environments. 相似文献
30.
Rakesh K. Goel 《地震工程与结构动力学》2001,30(9):1399-1416
This study investigated the effects of neglecting off‐diagonal terms of the transformed damping matrix on the seismic response of non‐proportionally damped asymmetric‐plan systems with the specific aim of identifying the range of system parameters for which this simplification can be used without introducing significant errors in the response. For this purpose, a procedure is presented in which modal damping ratios computed by neglecting off‐diagonal terms of the transformed damping matrix are used in the traditional modal analysis. The effects of the simplification are evaluated first by comparing the aforementioned modal damping ratios with the apparent damping ratios obtained from the complex‐valued eigenanalysis. The variation of a parameter that was defined by Warburton and Soni as an indicator of the errors introduced by the simplification is examined next. Finally, edge deformations obtained from the simplified procedure are compared with those obtained from the direct integration of the equations of motion. It is found that the simplified procedure may be used without introducing significant errors in response for most practical values of the system parameters. Furthermore, estimates of the edge deformations, in general, tend to be on the conservative side. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献