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11.
Pushp R. Tiwari Sarat C. Kar Uma C. Mohanty Sagnik Dey Palash Sinha P. V. S. Raju M. S. Shekhar 《Acta Geophysica》2014,62(4):930-952
The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies. 相似文献
12.
We examined seismic characteristics, b value and fractal dimension of the aftershock sequence of the January 26, 2001 Bhuj earthquake (Mw 7.7) that occurred in the Kutch failed rift basin, western margin of the Stable Continental Region (SCR) of India. A total of about 2,000 events (M?≥?2.0) were recorded within two and a half months, immediately after the main shock. Some 795 events were precisely relocated by simultaneous inversion. These relocated events are used for mapping the frequency-magnitude relation (b value) and fractal correlation dimension (Dc) to understand the seismic characteristics of the aftershocks and the source zone of the main shock. The surface maps of the b value and Dc reveal two distinct tectonic arms or zones of the V-shaped aftershock area, western zone and eastern zone. The b value is relatively higher (~1.6) in the western zone compared to a lower value (~1.4) in the eastern zone. The Dc map also shows a higher value (1.2–1.35) in the western zone compared to a lower Dc (0.80–1.15) in the eastern zone; this implies a positive correlation between Dc and b value. Two cross sections, E–W and N–S, are examined. The E–W sections show similar characteristics, higher b value and higher Dc in the western zone and lower in the eastern zone with depth. The N–S sections across the fault zones, however, show unique features; it imaged both the b and Dc characteristics convincingly to identify two known faults, the Kutch Mainland fault and the South Wagad fault (SWF), one stepping over the other with a seismogenic source zone at depth (20–35?km). The source zone at depth is imaged with a relatively lower b and higher Dc at the ‘fault end’ of the SWF showing a negative correlation. These observations, corroborated with the seismic tomography as well as with the proposed geological/tectonic model, shed a new light to our understanding on seismogenesis of the largest SCR earthquake in India in the recent years. 相似文献
13.
Siddarth Shankar Das Karanam Kishore Kumar K.N. Uma 《Journal of Atmospheric and Solar》2010,72(16):1184-1194
Continuous measurements of 3-dimensional winds, spectral parameters, and tropopause height for ~114 h during the passage of a tropical depression using mesosphere–stratosphere–troposphere (MST) radar at Gadanki (13.5°N, 79.2°E) are discussed. The spectral analysis of zonal and meridional winds shows the presence of inertia-gravity wave (IGW) with the dominant periodicity of 56 h and intrinsic period of 27 h in the upper troposphere and lower stratosphere (UTLS). The strengthening of easterly jet and associated wind shears during the passage of the depression is one of the causative mechanisms for exciting the IGW. A well-established radar method is used to identify the tropopause and to study its response to the propagating atmospheric disturbances. The significance of the present study lies in showing the response of tropopause height to the IGW during tropical depression for the first time, which will have implications in stratosphere–troposphere exchange processes. 相似文献
14.
Knowledge of dielectric permittivity of the soil provides direct measure of soil moisture content. A methodology to determine soil moisture based on the reflection coefficient measurement by a pseudo vector method using a horn antenna has been presented. To verify the efficacy of the method, measurements have been carried out at S, C & X band frequencies at two moisture levels and the corresponding emissivity parameters computed. Results so obtained are in good agreement with the already reported data and the direct moisture measurements. This method is expected to be of interest to agricultural scientists and to those involved in the application of remote sensing in crop studies. 相似文献
15.
Estimation and monitoring of crop evapotranspiration (ETc) or consumptive water use over large-area holds the key to irrigation management plans and regional drought preparedness. The objective of this study was to estimate ETc by applying the simplified-surface energy balance index (S-SEBI) model to Landsat-8 data for the 2014–2015 period in parts of North India. An average ETc was estimated 2.72 and 2.47 in mm day?1 with 0.22, 0.18 standard deviation and 0.11, 0.07 standard error for Kharif and Rabi crops, respectively. On validation part, a close relationship was observed between S-SEBI derived and scintillometer observed evaporative fraction with 0.85 correlation coefficient and 0.86 agreement index. The statistical analysis also endorses the results accuracy and reliability with 0.026 and 0.602, relative root-mean square errors and model efficiency for wheat crop, respectively. The study showed that normalized difference vegetation index and LST are closely related and serve as a proxy for qualitative representation of ETc. 相似文献
16.
The massive Zn-(Pb) sulfide ore body at Rampura-Agucha in Bhilwara district, Rajasthan, occurs within graphitic metapelites
surrounded by garnet-biotite-sillimanite gneiss containing concordant bodies of amphibolite. These rocks and the sulfide ores
have been studied to estimate the pressure, temperature and fluid composition associated with upper amphibolite facies metamorphism.
Geothermobarometric calculations involving garnet-biotite and garnet-hornblende pairs, as well as sphalerite-hexagonal pyrrhotite-pyrite
and garnet-plagioclase-sillimanite-quartz assemblages indicate that the most pervasive P-T condition during peak of regional
metamorphism was 650°C and 6 kb, and was attained between the first and second deformations in the region. Some temperature-pressure
estimates also cluster around 500°C–5.1 kb which probably represent retrograde cooling during unloading.
Consideration of devolatilization equilibria in the C-O-H-S system at the pervasive metamorphic conditions mentioned above
shows that the metamorphic fluid was H2O-rich (
) but also had a substantial component of
.
and
were the other important phases in the fluid. CO (XCO = 0.002) and
were the minor phases in the fluid. It is probable that a part of this aqueous fluid was consumed by re-/neocrystallization
of hydrous silicate phases like chlorite during the retrogressive metamorphic path, so that fluid entrapped in quartz below
450°C was rendered CO2-rich (Holleret al 1996). 相似文献
17.
Rupa Ghosh R. K. Sehgal Pradeep Srivastava U. K. Shukla A. C. Nanda D. S. Singh 《Journal of the Geological Society of India》2016,88(5):559-568
We describe an elephant skull recovered from a cliff section of Dhasan river of Marginal Ganga Plain. The dental morphology and cranial features of the skull have been compared with the known species of Elephas from the Indian subcontinent. Although it shows very near resemblance to Elephas namadicus, but being an isolated specimen its specific identity cannot be proclaimed with certainty. As such, the specimen is provisionally referred as E. cf. namadicus. The Optically Stimulated Luminescence ages place this find at ~56 ka BP. This is the first chronologically well constrained report of E. cf. namadicus from the Ganga Plain. 相似文献
18.
Igor V. Polyakov Vladimir A. Alexeev Uma S. Bhatt Evgenia I. Polyakova Xiangdong Zhang 《Climate Dynamics》2010,34(2-3):439-457
Climate fluctuations in the North Atlantic Ocean have wide-spread implications for Europe, Africa, and the Americas. This study assesses the relative contribution of the long-term trend and variability of North Atlantic warming using EOF analysis of deep-ocean and near-surface observations. Our analysis demonstrates that the recent warming over the North Atlantic is linked to both long-term (including anthropogenic and natural) climate change and multidecadal variability (MDV, ~50–80 years). Our results suggest a general warming trend of 0.031 ± 0.006°C/decade in the upper 2,000 m North Atlantic over the last 80 years of the twentieth century, although during this time there are periods in which short-term trends were strongly amplified by MDV. For example, MDV accounts for ~60% of North Atlantic warming since 1970. The single-sign basin-scale pattern of MDV with prolonged periods of warming (cooling) in the upper ocean layer and opposite tendency in the lower layer is evident from observations. This pattern is associated with a slowdown (enhancement) of the North Atlantic thermohaline overturning circulation during negative (positive) MDV phases. In contrast, the long-term trend exhibits warming in tropical and mid-latitude North Atlantic and a pattern of cooling in regions associated with major northward heat transports, consistent with a slowdown of the North Atlantic circulation as evident from observations and confirmed by selected modeling results. This localized cooling has been masked in recent decades by warming during the positive phase of MDV. Finally, since the North Atlantic Ocean plays a crucial role in establishing and regulating the global thermohaline circulation, the multidecadal fluctuations discussed here should be considered when assessing long-term climate change and variability, both in the North Atlantic and at global scales. 相似文献
19.
Mapping salt-affected soils in Sangrur district (Punjab) using aerial photo-interpretation technique
P. K. Sharma Jawahar L. Sehgal K. R. Sharma 《Journal of the Indian Society of Remote Sensing》1976,4(1-2):43-54
A detailed-reconnaissance soil survey of the Sangrur district was undertaken through systematic aerial photo-interpretation technique and a soil map on 1: 50,000 scale showing the association of soil series prepared. The salt-affected soils have been grouped into 4 soil associations and 8 soil series based on the diffrences in texture, drainge, profile development and degree of deterioration. The salt-affected soils are found both in plains and Channels. The piain unit without distinct parcelling (barren) white and fine textured tones represented the association of salic Natraqualfs (Ghabdan series) and Aquic Natruststalfs (Kaheru series). The piain units partly cultivated whitish-gray, fine to medium textured tones consisted of a association of Natraquic Calciorthids (Langrian and Narikc series) and Natraquic Camborthids (Isri Series). Lastly, the piain units with pattern of dark-tone and light mottles (mottled-iones,) distinct parceiling, cultivated consists of Typic Ustochrepts (Balewal series), Aquic Camborthids (Phaguwala series) and Natraquic Calciorthids (Marike series). The filled up Channels whitish-gray tones, concave relief, cultivated comprise wet soils (Jatwan series) which have been classified as Aeric Halaquepts. It is found that about 17% of the mapped area in Sangrur district is salt-affected, out of which 12% consisiing Ghabdan, Kaheru, Langrian and Isri series is severely salt-affected and rest 5% consisting, Phaguwala, Narike and Jatwan series is moderately to slightly affected. 相似文献
20.