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11.
R K Sarangi Prakash Chauhan Shailesh Nayak 《Journal of the Indian Society of Remote Sensing》2001,29(4):197-201
Remote sensing of ocean colour yields information on the constituents of sea water, such as the concentration of phytoplankton
pigments, suspended sediments and yellow substances. It is well understood that the study of ocean colour is significantly
related with the primary production and zonation of potential fishing sites in coastal and oceanic waters. The major pigment
constituent is predominated by chlorophyll-a (ocean colour pigment of phytoplankton). The chlorophyll mapping on regular basis
plays a major role in assessing water quality and classifying different water types. IRS P-3 MOS-B satellite data for three
consecutive passes of path 94, during the period of January-February 1997 have been used to derive chlorophyll-a concentration.
The present study emphasizes on the chlorophyll mapping using IRS-P3 MOS-B data for the coastal and offshore water of Maharashtra
coast, India. 相似文献
12.
The dynamics of terrestrial ecosystems depends on interactions between carbon, nutrient and hydrological cycles. Terrestrial ecosystems retain carbon in live biomass (aboveground and belowground), decomposing organic matter, and soil. Carbon is exchanged naturally between these systems and the atmosphere through photosynthesis, respiration, decomposition, and combustion. Human activities change carbon stock in these pools and exchanges between them and the atmosphere through land-use, land-use change, and forestry.In the present study we estimated the wood (stem) biomass, growing stock (GS) and carbon stock of Indian forests for 1984 and 1994. The forest area, wood biomass, GS, and carbon stock were 63.86 Mha, 4327.99 Mm3, 2398.19 Mt and 1085.06 Mt respectively in 1984 and with the reduction in forest area, 63.34 Mha, in 1994, wood biomass (2395.12 Mt) and carbon stock (1083.69 Mt) also reduced subsequently. The Conifers, of temperate region, stocked maximum carbon in their woods, 28.88 to 65.21 t C ha−1, followed by Mangrove forests, 28.24 t C ha−1, Dipterocarp forests, 28.00 t C ha−1, and Shorea robusta forests, 24.07 t C ha−1. Boswellia serrata, with 0.22 Mha forest area, stocked only 3.91 t C ha−1. To have an idea of rate of carbon loss the negative changes (loss of forest area) in forest area occurred during 1984–1994 (10yrs) and 1991–1994 (4yrs) were also estimated. In India, land-use changes and fuelwood requirements are the main cause of negative change. Total 24.75 Mt C was lost during 1984–1994 and 21.35 Mt C during 1991–94 at a rate of 2.48 Mt C yr−1 and 5.35 Mt C yr−1 respectively. While in other parts of India negative change is due to multiple reasons like fuelwood, extraction of non-wood forest products (NWFPs), illicit felling etc., but in the northeastern region of the country shifting cultivation is the only reason for deforestation. Decrease in forest area due to shifting cultivation accounts for 23.0% of the total deforestation in India, with an annual loss of 0.93 Mt C yr−1. 相似文献
13.
Praveen Gupta Amit Kumar Dubey Nandita Goswami Raghvendra Pratap Singh Prakash Chauhan 《Marine Geodesy》2015,38(3):614-625
In the absence of many gauging stations in the major and mighty river systems, there is a need for satellite-based observations to estimate temporal variations in the river water storage and associated water management. In this study, SARAL/AltiKa application for setting up hydraulic model (HEC-RAS) and river flow simulations over Tapi River India has been discussed. Waveform data of 40 Hz from Ka band altimeter has been used for water levels retrieval in the Tapi river. SARAL/AltiKa retrieved water levels were converted to discharge in the upstream location (track-926) using the rating curve available for the nearby gauging site and using linear spatial interpolation technique. Steady state simulations were done for various flow conditions in the upstream. Validation of river flow model was done in the downstream location (track-367) by comparing simulated and altimeter retrieved water levels (RMSE 0.67 m). Validated model was used to develop rating curve between water levels and simulated discharge for the downstream location which enables to monitor discharge variations from satellite platform in the absence of in situ observations. It has been demonstrated that SARAL/AltiKa data has potential for river flow monitoring and modeling which will feed for flood disaster forecasting, management and planning. 相似文献
14.
Shivani Shah B. M. Rao Prashant Kumar P. K. Pal 《Journal of Earth System Science》2010,119(6):775-781
Since the beginning of the summer monsoon 2009, experimental mesoscale weather forecasts in real time are being generated
using WRF model by the Meteorology and Oceanography Group at the Space Applications Centre (ISRO) and are disseminated through
MOSDAC () to various users. To begin with, the 12 h, 24 h and 48 h forecasts for the western India region are made available. A study
is undertaken to comprehensively assess the cloudiness prediction performance of WRF model. The evaluations have been made
over the three months period during monsoon 2009. INSAT cloud imagery data has been used as a reference for these evaluations.
The verification strategy includes computation of various skill scores. It is seen that probability of detection (POD) of
cloud is 84% and the false alarm rate (FAR) is around 18%. It is hoped that this assessment will provide information on the
use of these forecasts in various applications. 相似文献
15.
The high/low-amplitude anisotropic wave train events (HAE/LAE) in CR intensity have been investigated during the period 1981–1990, using the neutron monitoring data for different latitudes. In all, 21 HAE and 15 LAE cases have been studied. It has been observed that the phase of the diurnal anisotropy remains in the same co-rotational direction for the majority of the HAE/LAE cases. However, it has also been observed that the phase of the diurnal anisotropy changes to later hours in some of the HAE cases, whereas it changes to early hours in some of the LAE cases. Further, the amplitude of the semi-diurnal anisotropy for HAE/LAE cases remains statistically the same; however, the phase of the semi-diurnal anisotropy for HAE has been found to shift to later hours for all events. Furthermore, the HAE occur dominantly during the declining phase of solar activity, whereas LAE occur dominantly during the minimum solar activity period. The geomagnetic activity index-Ap has been observed to remain low during the period of each HAE/LAE. The possible phenomenon to cause the enhanced/low-amplitude daily variation has been proposed to appear on the back side of the Sun. 相似文献
16.
Kapil Chauhan Nicholas Hutchins Jason Monty Ivan Marusic 《Boundary-Layer Meteorology》2013,147(1):41-50
Two-point correlations of the fluctuating streamwise velocity are examined in the atmospheric surface layer over the salt flats of Utah’s western desert, and corresponding structure inclination angles are obtained for neutral, stable and unstable conditions. The neutral surface-layer results supplement evidence for the invariance of the inclination angle given in Marusic and Heuer (Phys Rev Lett 99:114504, 2007). In an extension of those results it is found that the inclination angle changes drastically under different stability conditions in the surface layer, varying systematically with the Monin–Obukhov stability parameter in the unstable regime. The variation is parametrized and subsequently can be used to improve existing near-wall models in the large-eddy simulation of the atmospheric surface layer. 相似文献
17.
P. V. Nagamani Prakash Chauhan Nivedita Sanwlani M. M. Ali 《Journal of the Indian Society of Remote Sensing》2012,40(1):137-143
Ocean-colour remote sensing in optically shallow waters is influenced by contribution from the water column depth as well
as by the substrate type. Therefore, it is required to include the contribution from the water column and substrate bottom
type for bathymetry estimation. In this report we demonstrate the use of Artificial Neural Network (ANN) based approach to
spectrally distinguish various benthic bottom types and estimate depth of substrate bottom simultaneously in optically shallow
waters. We have used in-water radiative transfer simulation modeling to generate simulated top-of-the-water column reflectance
the four major benthic bottom types viz. sea grass, coral sand, green algae and red algae using Hydrolight simulation model.
The simulated remote sensing reflectance, for the four benthic bottom types having benthic bottom depth up to 30 m were generated
for moderately clear waters. A multi-layer perceptron (MLP) type neural network was trained using the simulated data. ANN
based approach was used for classification of the benthic bottom type and simultaneous inversion of bathymetry. Simulated
data was inverted to yield benthic bottom type classification with an accuracy of ~98% for the four benthic substrate types
and the substrate depth were estimated with an error of 0% for sea grass, 1% for coral sand and 1–3% for green and red algae
up to 25 m, whereas for substrate bottom deeper than 25 m depth the classification errors increased by 2–5% for three substrate
bottom types except sea grass bottom type. The initial results are promising which needs validation using the in-situ measured
remote sensing reflectance spectra for implementing further on satellite data. 相似文献
18.
This study aims to illustrate how remotely sensed oceanic variables and fishing operations data can be used to predict suitable habitat of fishery resources in Geographic Information System. We used sea surface height anomaly (SSHa), sea surface temperature (SST), chlorophyll concentration (CC), photosynthetically active radiation (PAR) and fishing depth as predictor variables. Fishery data of Indian squid (Loligo spp.) and catfish (Tachysurus spp.) for study period (1998–2004) were segregated randomly to create training and validation. Catch was normalized into Catch per unit Effort (kg h?1). Generalized additive modelling was performed on training data and then tested on validation data. Suitable ranges of SST, CC, SSHa and PAR for different species distributions were derived and integrated to predict their spatial distributions. Results indicated good match between predicted and actual catch. Monthly probability maps of predicted habitat areas coincide with high catch of the particular month for the study period. 相似文献
19.
Nivedita Sanwlani Prakash Chauhan Ranganath R. Navalgund 《Journal of the Indian Society of Remote Sensing》2010,38(4):617-626
Space-borne ocean-colour remote sensor-detected radiance is heavily contaminated by solar radiation backscattered by the atmospheric
air molecules and aerosols. Hence, the first step in ocean-colour data processing is the removal of this atmospheric contribution
from the sensor-detected radiance to enable detection of optically active oceanic constituents e.g. chlorophyll-a, suspended sediment etc. In standard atmospheric correction procedure for OCEANSAT-1 Ocean Colour Monitor (OCM) data, NIR
bands centered at 765 and 865 nm wavelengths were used for aerosol characterization. Due to high absorption by water molecules,
ocean surface in these two wavelengths acts as dark background, therefore, sensor detected radiance can be assumed to have
major contribution from atmospheric scattering. For coastal turbid waters this assumption of dark surface fails due to the
presence of highly scattering sediments which causes sufficient water-leaving radiance in NIR bands and lead to over-estimation
of aerosol radiance resulting in negative water leaving radiance for λ < 700 nm. In the present study, for the turbid coastal
waters in the northern Bay of Bengal, the concept of spatial homogeneity of aerosol and water leaving reflectance has been
applied to perform atmospheric correction of OCAEANSAT-1 OCM data. The results of the turbid water atmospheric correction
have also been validated using in-situ measured water-leaving radiance. Comparison of satellite derived water-leaving radiance for five coastal stations with in-situ measured radiance spectra, indicates an improvement over the standard atmospheric correction algorithm giving physically
realistic and positive values. Root Mean Square Error (RMSE) between the in-situ measured and satellite derived water leaving radiance for wavelengths 412 nm, 443 nm, 490 nm, 512 nm and 555 nm was found
to be 1.11, 0.718, 0.575, 0.611 and 0.651%, respectively, using standard atmospheric correction procedure. By the use of spatial
homogeneity concept, this error was reduced to 0.125, 0.173, 0.176, 0.225, and 0.290 and the correlation coefficient arrived
at 0.945, which is an improvement over the standard atmospheric correction procedure. 相似文献
20.
Jamaledin Baniamerian Shuang Liu Xiangyun Hu Maurizio Fedi Mahak Singh Chauhan Mahmoud Ahmed Abbas 《Geophysical Prospecting》2020,68(7):2320-2342
Inversion of magnetic data is complicated by the presence of remanent magnetization, and it provides limited information about the magnetic source because of the insufficiency of data and constraint information. We propose a Fourier domain transformation allowing the separation of magnetic anomalies into the components caused by induced and remanent magnetizations. The approach is based on the hypothesis that each isolated source is homogeneous with a uniform and specific Koenigsberger ratio. The distributions of susceptibility and remanent magnetization are subsequently recovered from the separated anomalies. Anomaly components, susceptibility distribution and distribution of the remanent and total magnetization vectors (direction and intensity) can be achieved through the processing of the anomaly components. The proposed method therefore provides a procedure to test the hypotheses about target source and magnetic field, by verifying these models based on available information or a priori information from geology. We test our methods using synthetic and real data acquired over the Zhangfushan iron-ore deposit and the Yeshan polymetallic deposit in eastern China. All the tests yield favourable results and the obtained models are helpful for the geological interpretation. 相似文献