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21.
P. Rajakumar S. Sanjeevi S. Jayaseelan G. Isakkipandian M. Edwin P. Balaji G. Ehanthalingam 《Journal of the Indian Society of Remote Sensing》2007,35(1):31-42
Remote sensing and Geographic Information System (GIS) are well suited to landslide studies. The aim of this study is to prepare
a landslide susceptibility map of a part of Ooty region, Tamil Nadu, India, where landslides are common. The area of the coverage
is approximately 10 × 14 km in a hilly region where planting tea, vegetables and cash crops are in practice. Hence, deforestation,
formation of new settlements and changing land use practices are always in progress. Land use and land cover maps are prepared
from Indian Remote Sensing Satellite (IRS 1C - LISS III) imagery. Digital Elevation Model (DEM) was developed using 20 m interval
contours, available in the topographic map. Field studies such as local enquiry, land use verification, landslide location
identification were carried out. Analysis was carried out with GIS software by assigning rank and weights for each input data.
The output shows the possible landslide areas, which are grouped for preparation of landslide susceptibility maps. 相似文献
22.
Ocean Dynamics - In this study, the behaviour of cyclones in the Bay of Bengal in future climatic conditions is analysed with the help of an ocean-atmosphere coupled model. The weather research and... 相似文献
23.
Balaji B. Maruthi Sridhar Robert K. Vincent Wentworth B. Clapham Subramania I. Sritharan John Osterberg Christopher M.U. Neale 《国际地球制图》2013,28(8):649-662
Saltcedar (Tamarix ramosissima), an invasive shrub species, has successfully invaded large extents of several riparian zones in the western United States and northern Mexico. Mapping the distribution and abundance of saltcedar over these large areas through a multi-seasonal, cost-effective monitoring approach using satellite remote sensing is very essential. Ground truth surveys were conducted at 79 locations where the spectral reflectance measurements of vegetation, type of plant species, plant heights, soil samples and GPS co-ordinates were recorded. All the sampling was designed to coincide with the satellite overpass period. The Landsat TM colour-composite spectral ratio image (normalized difference vegetative index (NDVI), R 1,5 and R 1,7 as green, blue and red) can clearly identify and map the areas infested with saltcedar. The Landsat image analysis shows that these spectral ratios can be applied to multiple satellite overpasses for monitoring the seasonal progression of the saltcedar growth over time. 相似文献
24.
Yeonsang?HwangEmail author Martyn?Clark Balaji?Rajagopalan George?Leavesley 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(2):295-320
Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational
points to the specific grid points. We compare and contrast the performance of regression-based statistical methods for the
spatial estimation of precipitation in two hydrologically different basins and confirmed that widely used regression-based
estimation schemes fail to describe the realistic spatial variability of daily precipitation field. The methods assessed are:
(1) inverse distance weighted average; (2) multiple linear regression (MLR); (3) climatological MLR; and (4) locally weighted
polynomial regression (LWP). In order to improve the performance of the interpolations, the authors propose a two-step regression
technique for effective daily precipitation estimation. In this simple two-step estimation process, precipitation occurrence
is first generated via a logistic regression model before estimate the amount of precipitation separately on wet days. This
process generated the precipitation occurrence, amount, and spatial correlation effectively. A distributed hydrologic model
(PRMS) was used for the impact analysis in daily time step simulation. Multiple simulations suggested noticeable differences
between the input alternatives generated by three different interpolation schemes. Differences are shown in overall simulation
error against the observations, degree of explained variability, and seasonal volumes. Simulated streamflows also showed different
characteristics in mean, maximum, minimum, and peak flows. Given the same parameter optimization technique, LWP input showed
least streamflow error in Alapaha basin and CMLR input showed least error (still very close to LWP) in Animas basin. All of
the two-step interpolation inputs resulted in lower streamflow error compared to the directly interpolated inputs. 相似文献
25.
C. Balaji M. Deiveegan S. P. Venkateshan R. M. Gairola A. Sarkar V. K. Agarwal 《Journal of Earth System Science》2009,118(4):331-343
In the present study, forward radiative transfer simulations are carried out for the tropical cyclone Fanoos that hit the coast off south India in December 2005. The in-house radiative transfer package used for this study employs
the doubling and adding method to calculate radiances leaving the top of the one dimensional precipitating atmosphere. The
particle drop size distribution is assumed to follow a modified gamma distribution in respect of the cloud liquid water and
cloud ice water content. For precipitation, the Marshall-Palmer particle size distribution is used. All the hydrometeor particles
are assumed to be spherical and Lorentz Mie theory is used to evaluate the interaction parameters like absorption, scattering
coefficients and polarized scattering matrix. In order to validate the drop size distributions and interaction parameter calculations,
the simulated brightness temperatures are compared with the TMI measured brightness temperatures for all the channels. For
carrying out this exercise, vertical hydrometeors retrieved by TMI are used as input. The differences between simulated and
measured brightness temperatures are found to be within ±10%. The maximum difference in the brightness temperatures between
the present work and the Eddington model which the TRMM algorithm employs is about 4.5K. This may become significant when
retrieval of precipitation is attempted by combining the forward model with a suitable retrieval strategy, under tropical
conditions. 相似文献
26.
For central India and its west coast, rainfall in the early (15 May–20 June) and late (15 September–20 October) monsoon season correlates with Pacific Ocean sea-surface temperature (SST) anomalies in the preceding month (April and August, respectively) sufficiently well, that those SST anomalies can be used to predict such rainfall. The patterns of SST anomalies that correlate best include the equatorial region near the dateline, and for the early monsoon season (especially since ~1980), a band of opposite correlation stretching from near the equator at 120°E to ~25°N at the dateline. Such correlations for both early and late monsoon rainfall and for both regions approach, if not exceed, 0.5. Although correlations between All India Summer Monsoon Rainfall and typical indices for the El Ni?o-Southern Oscillation (ENSO) commonly are stronger for the period before than since 1980, these correlations with early and late monsoon seasons suggest that ENSO continues to affect the monsoon in these seasons. We exploit these patterns to assess predictability, and we find that SSTs averages in specified regions of the Pacific Ocean in April (August) offer predictors that can forecast rainfall amounts in the early (late) monsoon season period with a ~25% improvement in skill relative to climatology. The same predictors offer somewhat less skill (~20% better than climatology) for predicting the number of days in these periods with rainfall greater than 2.5?mm. These results demonstrate that although the correlation of ENSO indices with All India Rainfall has decreased during the past few decades, the connections with ENSO in the early and late parts have not declined; that for the early monsoon season, in fact, has grown stronger in recent decades. 相似文献
27.
The objective of the present work is to develop a general purpose, polarized, microwave radiative transfer forward model, including calculation of interaction parameters for fast, simultaneous and accurate generation of radiances, for use in a wide variety of atmospheric retrieval applications. This complete polarized model includes the generation of atmospheric profiles, calculation of the interaction parameters and the solution of the vector radiative transfer equations. In the present work, the doubling and adding method is used to calculate radiances. Mie theory is used for spherical particles to evaluate the polarized scattering matrix. Two types of sea surface models applicable for specular and diffuse surfaces respectively are implemented. The model has been validated against standard benchmark cases and experimental data available in literature. While the model is itself generic, parametric studies are performed to study the influence of the vertical structure of the atmosphere, for two polarizations and a set of frequencies to be used on the microwave imager aboard the proposed Indo-French climate research satellite MEGHA-TROPIQUES. 相似文献
28.
Pablo A. Mendoza Martyn P. Clark Naoki Mizukami Ethan D. Gutmann Jeffrey R. Arnold Levi D. Brekke Balaji Rajagopalan 《水文研究》2016,30(7):1071-1095
End users face a range of subjective decisions when evaluating climate change impacts on hydrology, but the importance of these decisions is rarely assessed. In this paper, we evaluate the implications of hydrologic modelling choices on projected changes in the annual water balance, monthly simulated processes, and signature measures (i.e. metrics that quantify characteristics of the hydrologic catchment response) under a future climate scenario. To this end, we compare hydrologic changes computed with four different model structures – whose parameters have been obtained using a common calibration strategy – with hydrologic changes computed with a single model structure and parameter sets from multiple options for different calibration decisions (objective function, local optima, and calibration forcing dataset). Results show that both model structure selection and the parameter estimation strategy affect the direction and magnitude of projected changes in the annual water balance, and that the relative effects of these decisions are basin dependent. The analysis of monthly changes illustrates that parameter estimation strategies can provide similar or larger uncertainties in simulations of some hydrologic processes when compared with uncertainties coming from model choice. We found that the relative effects of modelling decisions on projected changes in catchment behaviour depend on the signature measure analysed. Furthermore, parameter sets with similar performance, but located in different regions of the parameter space, provide very different projections for future catchment behaviour. More generally, the results obtained in this study prompt the need to incorporate parametric uncertainty in multi‐model frameworks to avoid an over‐confident portrayal of climate change impacts. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
29.
In this study, retrieval of temperature and humidity profiles of atmosphere from INSAT 3D-observed radiances has been accomplished. As the first step, a fast forward radiative transfer model using an Artificial neural network has been developed and it was proven to be highly effective, giving a correlation coefficient of 0.97. In order to develop this, a diverse set of physics-based clear sky profiles of pressure (P), temperature (T) and specific humidity (q) has been developed. The developed database was further used for geophysical retrieval experiments in two different frameworks, namely, an ANN and Bayesian estimation. The neural network retrievals were performed for three different cases, viz., temperature only retrieval, humidity only retrieval and combined retrieval. The temperature/humidity only ANN retrievals were found superior to combined retrieval using an ANN. Furthermore, Bayesian estimation showed superior results when compared with the combined ANN retrievals. 相似文献
30.
Geoelectrical resistivity investigation using Vertical Electrical Sounding (VES) technique was conducted at Port Blair, South Andaman Island, to locate the fractures in different formations and to decipher its groundwater potential. A total of 40 VES were carried out covering the entire study area using Schlumberger electrode configuration out of which 34 VES fall in Andaman Flysch formations and the remaining VES in Ophiolite formations. The interpreted resistivity results were integrated with nine borehole lithologs for the subsurface analysis. The combination of VES with borehole litholog data has provided a close correspondence on subsurface hydrogeological conditions. The interpreted VES data of various formations showed drastic variations in the resistivity ranging from higher in Ophiolite, moderate in Andaman Flysch and very low in valleys of Andaman Flysch formations. The study further revealed that the weathered and fractured volcanics of Ophiolite groups of rocks and sandstone that occur in the Andaman Flysch formations constitute the productive water bearing zones categorized as good groundwater potential zone. Based on the geoelectrical parameters, viz., thickness of layers and the layer resistivity values, a groundwater potential map was prepared, in which good, moderate, and poor groundwater zones were demarcated. Further, numerical, spatial and litho-geoelectric models of resistivity were analyzed in terms of groundwater potential and these models have thus enabled to prepare a comprehensive groundwater development and management plans proving its efficacy in this art of exploratory investigations. 相似文献