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Abstract Water bodies up to 0.9 ha surface area, which are indistinguishable by Landsat Multispectral Scanner (MSS) due to the latter's poor spatial resolution of 80 m, can be identified and mapped reliably and reasonably within ±10% accuracy by Landsat Thematic Mapper (TM) false colour composite because of its higher spectral and spatial resolution of 30 m. Comparative study of Landsat TM and the Survey of India topographical maps revealed reductions in the water surface and drainage basin areas up to 1.8 to 2.4 and 6.0 to 8.0 times, respectively, over a period of 28 years (1958–1986) due to the biotic interference resulting in desertification in the large adjoining areas. 相似文献
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Abstract Over-exploitation of an alluvial aquifer in India has occurred since tubewells were drilled into deeper aquifers. Field information concerning-the fall in both the water table and the piezometric heads in the deeper aquifers has been examined and a numerical model has been developed to represent a heavily exploited area. Predictions using the model suggest that the annual declines in the water table and the piezometric heads are accelerating as the water table moves into a zone having a lower specific yield. Careful monitoring of the movement of the water table is proposed. 相似文献
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Hemantkumar S. Chaudhari Samir Pokhrel Sachiko Mohanty Subodh K. Saha 《Theoretical and Applied Climatology》2013,114(3-4):459-477
This study has identified probable factors that govern ISMR predictability. Furthermore, extensive analysis has been performed to evaluate factors leading to the predictability aspect of Indian Summer Monsoon Rainfall (ISMR) using uncoupled and coupled version of National Centers for Environmental Prediction Coupled Forecast System (CFS). It has been found that the coupled version (CFS) has outperformed the uncoupled version [Global Forecast System (GFS)] of the model in terms of prediction of rainfall over Indian land points. Even the spatial distribution of rainfall is much better represented in the CFS as compared to that of GFS. Even though these model skills are inadequate for the reliable forecasting of monsoon, it imparts the capacious knowledge about the model fidelity. The mean monsoon features and its evolution in terms of rainfall and large-scale circulation along with the zonal and meridional shear of winds, which govern the strength of the monsoon, are relatively closer to the observation in the CFS as compared to the GFS. Furthermore, sea surface temperature–rainfall relation is fairly realistic and intense in the coupled version of the model (CFS). It is found that the CFS is able to capture El Niño Southern Oscillation ISMR (ENSO-ISMR) teleconnections much strongly as compared to GFS; however, in the case of Indian Ocean Dipole ISMR teleconnections, GFS has the larger say. Coupled models have to be fine-tuned for the prediction of the transition of El Niño as well as the strength of the mature phase has to be improved. Thus, to sum up, CFS tends to have better predictive skill on account of following three factors: (a) better ability to replicate mean features, (b) comparatively better representation of air–sea interactions, and (c) much better portrayal of ENSO-ISMR teleconnections. This study clearly brings out that coupled model is the only way forward for improving the ISMR prediction skill. However, coupled model’s spurious representation of SST variability and mean model bias are detrimental in seasonal prediction. 相似文献
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Abstract A conceptual basin model of the instantaneous unit sediment graph was developed for sediment graph prediction from arid upland basins by routing mobilized sediments through a series of linear reservoirs. The sediment graphs generated by convolution of the instantaneous unit sediment graph compared reasonably well with the observed ones for four representative arid upland sub-basins in the Luni basin, India. The mobilized sediment during a storm was related to effective precipitation and the parameters of the model were estimated from observed events. The model can be applied to ungauged flow events through parameterization. 相似文献
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Petrochemical studies of granitoid rocks from the eastern part of Kumaun region suggest that the leading edge of India represents an active arc during Late Paleoproterozoic times. It has been observed that melt generation for granodiorite rocks from the eastern Almora Nappe and Chhiplakot klippe along with the Askot klippe was caused through a subduction‐related process involving hydrous partial melting of a Paleoproterozoic amphibole‐ and/or garnet‐bearing mafic source with the involvement of sediments from the subduction zone. The medium‐ to high‐K basic rocks, common in subduction‐related magmatic arcs, can also explain the generation of the high‐K granodiorites of the Chhiplakot klippe. The augen gneisses from the eastern Almora nappe and Chhiplakot klippe along with the Askot klippe further show geochemical similarity with the associated granodiorites, suggesting there is a genetic linkage with one another. 相似文献
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Determining the optimum cell size of digital elevation model for hydrologic application 总被引：1，自引：0，他引：1
Scale is one of the most important but unsolved issues in various scientific disciplines that deal with spatial data. The
arbitrary choice of grid cell size for contour interpolated digital elevation models (DEM) is one of the major sources of
uncertainty in the hydrologic modelling process. In this paper, an attempt was made to identify methods for determining an
optimum cell size for a contour interpolated DEM in prior to hydrologic modelling. Twenty-meter interval contour lines were
used to generate DEMs of five different resolutions, viz., 30, 45, 60, 75, and 90 m using TOPOGRID algorithm. The obtained DEMs were explored for their intrinsic quality using four
different methods, i.e., sink analysis, fractal dimension of derived stream network, entropy measurement and semivariogram
modelling. These methods were applied to determine the level artifacts (interpolation error) in DEM surface as well as derived
stream network, spatial information content and spatial variability respectively. The results indicated that a 90 m cell size
is sufficient to capture the terrain variability for subsequent hydrologic modelling in the study area. The significance of
this research work is that it provides methods which DEM users can apply to select an appropriate DEM cell size in prior to
detailed hydrologic modelling. 相似文献
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NAND L SHARMA JAGDISH C KUNIYAL MAHAVIR SINGH PRIYANKA SHARMA KESAR CHAND AJAY KUMAR NEGI MANUM SHARMA HARINDER KUMAR THAKUR 《Journal of Earth System Science》2011,120(2):281-290
The concentration of ultrafine aerosol particles of aitken and nucleation mode having size in the range of 1–20 nm was monitored
with water-based Condensation Particle Counter. The monitoring was carried out from midnight-to-midnight in every alternate
day on a fortnightly basis to represent summer, monsoon and winter (autumn) seasons of 2008 at Mohal (1154 m amsl) and Kothi
(2530 m amsl) in Kullu-Manali area of the northwestern Himalayan region of India. The results indicate that diurnal pattern
has faint bimodal structure with two peaks, one in morning and the other in evening at both the sites but it is not as distinct
as found in plains. There is rather a constant particle density pattern of large magnitude consistent with vehicular movement
from morning till evening. The monthly 24 h average particle density gradually picks up from January, increases rapidly in
summer months and then decreases in monsoon season at Mohal but at Kothi it keeps on rising from April to October with a slight
more increase in September. The particle density is more in summer than in monsoon season at Mohal, a trend opposite to plains.
It may be due to the development of warm thermal layer on valley floor while a cold layer develops along snowy hilltops in
winter leading to convection of fine particle up the slopes of valley during daytime. At Kothi, the trend is same as it is
in continental plains but opposite to Mohal. The relatively more value of particle density in September and October at both
the sites may be due to month long International Kullu Dussehra fair in the valley. The vehicular survey conducted agrees
well with entire study period averaged diurnal variations and monthly 24 h averaged value of fine particle density. The average
value of ultrafine particle density at each hour of a day for entire study period is 20369 ± 1230 Ncm − 3 and 14389 ± 1464 Ncm − 3 at Mohal and Kothi sites, respectively. The comparison with earlier results shows a significant increase indicating impact
of vehicular onslaught on pure air of this hilly region. 相似文献