Segmentation of Main Boundary Thrust and Main Central Thrust in Western Himalaya for assessment of seismic hazard     

Singh Mridula  Amita Sinvhal  Hans Raj Wason  Swati Singh Rajput 《Natural Hazards》2016,84(1):383-403

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Elevational Dependence of Air Temperature Variability and Trends in British Columbia's Cariboo Mountains, 1950–2010     

Aseem Raj Sharma  Stephen J. Déry 《大气与海洋》2016,54(2):153-170

Pristine mountain environments are more sensitive to climate change than other land surfaces. Climatic variations in mountainous terrain are still poorly understood. Previous studies revealed inconsistent findings on the elevational dependence of warming in the mountains. In this study, the trends and elevational dependence of air temperature in the Cariboo Mountains Region (CMR) of British Columbia are explored using a surface air temperature dataset with a spatial resolution of five arc minutes over the 1950–2010 period. A Mann-Kendall test is performed for evaluation of trends and their significance. In recent decades the CMR has been warming at a faster rate than regional and global warming. The minimum air temperature trend shows significant amplified warming at higher elevations. The snow–albedo feedback and changes in cloud cover over the CMR may possibly be the major physical mechanisms responsible for these trends. The implications of such changes on the endangered mountain caribou and water resources of the area are also discussed.  相似文献   

Performance of Global Soil Moisture Products in Crop Growing Region of Central India     

Sitiraju Srinivasa Rao  Dinesh Kumar Sahadevan  Milind R. Wadodkar  M/ S. S. Nagaraju  Sudipta Chattaraj  William Joseph  Prasanth Rajankar  Titu Sengupta  M. V. Venugopalan  Subrata N. Das  Asok Kumar Joshi  Jaswanth Raj Sharma  Eadara Amminedu 《Journal of the Indian Society of Remote Sensing》2016,44(2):277-285

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Landslide detection in the Himalayas using machine learning algorithms and U-Net     

Meena  Sansar Raj  Soares  Lucas Pedrosa  Grohmann  Carlos H.  van Westen  Cees  Bhuyan  Kushanav  Singh  Ramesh P.  Floris  Mario  Catani  Filippo 《Landslides》2022,19(5):1209-1229

Landslides - Event-based landslide inventories are essential sources to broaden our understanding of the causal relationship between triggering events and the occurring landslides. Moreover,...  相似文献   

Validation of SWH and SSHA from SARAL/AltiKa Using Jason-2 and In-Situ Observations     

Suchandra Aich Bhowmick  Rashmi Sharma  K. N. Babu  A. K. Shukla  Raj Kumar  R. Venkatesan 《Marine Geodesy》2015,38(3):193-205

The focus of this study is the validation of significant wave height (SWH) and sea surface height anomaly (SSHA) obtained from the first Ka-band altimeter AltiKa onboard SARAL (Satellite for ARGOS and Altimeters). It is a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales (CNES). This is done using in-situ observations from buoy and Jason-2 measurements. Validation using buoy observations are at particular locations while that using Jason-2 altimeter is an attempt towards global validation of Altika products. The results clearly indicate that the SARAL/AltiKa provide high-quality data and the errors are within a predefined range of accuracy. A parallel validation of SWH from other altimeters, which monitored ocean since last decade, like EnviSAT and Jason-2 was also performed with buoy observations. The results clearly show that the accuracy of AltiKa SWH is much better than EnviSAT and comparable to reference mission Jason-2. The accuracy is quite good for the calm sea while in the rough seas the accuracy degrades some. The inter-comparison of SARAL/AltiKa SSHA with Jason-2 indicates a fair match between them. These validation exercises demonstrate the high quality of AltiKa products, usable for practical applications.  相似文献   

Prediction of satellite orbits contraction due to diurnally varying oblate atmosphere and altitude-dependent scale height using KS canonical elements     

Xavier James Raj 《Planetary and Space Science》2009,57(11):1312-1320

A new non-singular analytical theory for the motion of near-Earth satellite orbits with the air drag effect is developed in terms of uniformly regular KS canonical elements. Diurnally varying oblate atmosphere is considered with variation in density scale height dependent on altitude. The series expansion method is utilized to generate the analytical solutions and terms up to fourth-order terms in eccentricity and c (a small parameter dependent on the flattening of the atmosphere) are retained. Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. The important drag perturbed orbital parameters: semi-major axis and eccentricity are obtained up to 500 revolutions, with the present analytical theory and by numerical integration over a wide range of perigee height, eccentricity and inclination. The differences between the two are found to be very less. A comparison between the theories generated with terms up to third- and fourth-order terms in c and e shows an improvement in the computation of the orbital parameters semi-major axis and eccentricity, up to 9%. The theory can be effectively used for the re-entry of the near-Earth objects, which mainly decay due to atmospheric drag.  相似文献   

Contraction of near-Earth satellite orbits using uniformly regular KS canonical elements in an oblate atmosphere with density scale height variation with altitude     

M. Xavier James Raj 《Planetary and Space Science》2009,57(1):34-41

A new non-singular analytical theory for the contraction of near-Earth satellite orbits under the influence of air drag is developed in terms of uniformly regular Kustaanheimo and Stiefel (KS) canonical elements using an oblate atmosphere with variation of density scale height with altitude. The series expansions include up to fourth power in terms of eccentricity and c (a small parameter dependent on the flattening of the atmosphere). Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. It is observed that the analytically computed values of the semi-major axis and eccentricity are consistent with the numerically integrated values up to 500 revolutions over a wide range of the drag-perturbed orbital parameters. The theory can be effectively used for re-entry of near-Earth objects.  相似文献   

Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time-scale     

Arti Goyal    Gopal-Krishna  G. C. Anupama  D. K. Sahu  R. Sagar  S. Britzen  M. Karouzos †  M. F. Aller  H. D. Aller 《Monthly notices of the Royal Astronomical Society》2009,399(3):1622-1632

We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R -band monitoring for a minimum duration of ∼4 hours, on 17 nights spanning 11 years (1998–2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of  ≥3 per cent  on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of  ≳4  hours duration is known to be high  (∼50 per cent)  . Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties.  相似文献   

An integrated approach for resource development using remote sensing — A case study specific to hill areas     

A K Gupta  P P Nageswara Rao  K Ganesha Raj  C B S Dutt  M G Chandrasekhar 《Journal of the Indian Society of Remote Sensing》1993,21(2):99-108

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Aircraft observations of electrical conductivity in warm clouds     

P. Ernest Raj  P. C. S. Devar  A. M. Selvam  A.S.R. Murty 《大气科学进展》1993,10(1):95-102

Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, India. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and coro-na discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other investigators.Classical static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivi-ty measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mech-anism of vertical mixing in clouds lends support to coovective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.  相似文献