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1.
A new CFAR ship target detection method in SAR imagery 总被引：8，自引：2，他引：6
Many ship target detection methods have been developed since it was verified that ship could be imaged with the space-based SAR systems. Most developed detection methods mostly emphasized ship detection rate but not computation time. By making use of the advantages of the K-distribution CFAR method and two-parameter CFAR method, a new CFAR ship target detection algorithm was proposed. In that new method, we use the K-distribution CFAR method to calculate a global threshold with a certain false-alarm rate. Then the threshold is applied to the whole SAR imagery to determine the possible ship target pixels, and a binary image is given as the preliminary result. Mathematical morphological filter are used to filter the binary image. After that step, we use the two-parameter CFAR method to detect the ship targets. In the step, the local sliding window only works in the possible ship target pixels of the SAR imagery. That step avoids the statistical calculation of the background pixels, so the method proposed can much improve the processing speed. In order to test the new method, two SAR imagery with different background were used, and the detection result shows that that method can work well in different background circumstances with high detection rate. Moreover, a synchronous ship detection experiment was carried out in Qingdao port in October 28, 2005 to verify the new method and one ENVISAT ASAR imagery was acquired to detect ship targets. It can be concluded from the experiment that the new method not only has high detection rate, but also is time-consuming, and is suitable for the operational ship detection system. 相似文献
2.
基于X波段微波雷达的近海水深数值模拟与反演 总被引：2，自引：2，他引：0
3.
Coral reefs are an sensitive-to-environment complex marine ecosystem. The ecosystem of corals is rich in biodiversity. Remote sensing offers a powerful tool for categorizing coral reefs and is the most cost-effective approach for the large-scale reef survey. The Dongsha Atoll, more than 300 km2 with an average depth of 10 m, is located at the northern continental margin of the South China Sea. It has been abused by destructive fishing during recent decades. Three satellite imageries (Quickbird2, ETM and SPOT5) are used to evaluate the capabilities of SPOT5 imagery to provide data that are useful for categorizing the current distribution of coral reefs therein. During the data processing, unsupervised classification functions are adopted for ETM and SPOT5 data, while the supervised classification method is used for Quickbird2. The classes are (or not) merged into coral reef, and then will be operated by vectorization, simplification, and topological analysis. There are 1 331 coral reefs larger than 100 m2 with a detection limit of 3×3 pixels at the multi-band data of Quickbird2, which is taken as the comparison baseline. The results extracted from SPOT5 and ETM images are less in number and area than those from the Quickbird2 image, whereas the results from SPOT5 data are better than those of ETM data at the silty lagoon due to its higher resolution. SPOT5 XS band 2 fails to distinguish the deep substrate inside the atoll compared with ETM data because of its poor penetration capability. Only SPOT XS band 1 cannot be used to differentiate coral reef from sand bottom. Merging the SPOT5 multi-bands data with the spatial resolution of SPOT5 pan-data and referring to ETM imagery are expected to provide an optimal satellite-based approach for mapping of coral reefs. 相似文献
4.
You Yuming Hou Min Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Assistant Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1992,(3)
- The data of landsat TM of multi-temporal for Lingdingyang Estuary, Pearl River in China is firstly used with suspended sediment concentration of field measurement to establish a correlative model equation. After the ratio processing of TM data and atmospheric correction, the images of suspended sediment concentration of different temporals are exported from the image processing systems AREIS II and III. These images express the characteristics of suspended sediment distribution, the mode of sediment transport and the extent of dispersion under the actions of tidal current and wind condition of different seasons. 相似文献
5.
This paper proposes a rain considered geophysical model function (GMF), to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency (JMA). The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section (NRCS) is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective. 相似文献
6.
A coastline is defined as the average spring tide line. Different types of seacoast, such as sandy, silty, and bio- logical coast, have different indicators of interpretation. It is very difficult to develop a universal method for interpreting all shorelines. Therefore, the sandy, the silty, and the biological coast are regarded as research objects, and with data mining technolog,found the rules of interpretation of those three types of coastlines. Then, an intelligent coastline interpretation method based on rules was proposed. Firstly, the rules for ex- tracting the waterline in Landsat TM/ETM＋ （Thematic Mapper/Enhanced Thematic Mapper Plus） imagery were discovered. Then, through analyzing the features of sandy, silty and biological coast, the indicators of interpreting different types of shoreline were determined. According to the indicators, the waterline could be corrected to the real coastline. In order to verify the validity of the proposed algorithms, three Landsat TM/ETM＋ imageries were selected for case studies. The experimental results showed that the proposed methods could interpret the coastlines of sandy; silty, and biological coasts with high precision and without human intervention, which exceeded three pixels. 相似文献
7.
基于背景场的一种新的赤潮监测算法 总被引：1，自引：1，他引：0
Remote sensing has been proven to be an effective means of monitoring red tides. The spectral information is an important basis for establishing a model to monitor red tides. The spectral curves of red tide events are analyzed and compared with multiyear monthly averaged spectral curves based on MODIS data from July 2002 to June 2012, as well as spectral differences at the same location during red tide presence and absence. A red tide monitoring algorithm is developed based on the background field to extract the red tide information of the East China Sea （ECS）. With the application of the algorithm in the ECS, the results reveal that the developed model can effectively determine the location of red tides, with good correspondence to the results from an official bulletin. This demonstrates that the algorithm can effectively extract the red tide information. 相似文献
8.
《海洋学报(英文版)》2017,(3)
A WAVEWATCH III version 3.14(WW3) wave model is used to evaluate input/dissipation source term packages WAM3, WAM4 and TC96 considering the effect of atmospheric instability. The comparisons of a significant wave height acquired from the model with different packages have been performed based on wave observation radar and HY-2 altimetry significant wave height data through five experiments in the South China Sea domain spanning latitudes of 0°–35°N and longitudes of 100°–135°E. The sensitivity of the wind speed correction parameter in the TC96 package also has been analyzed. From the results, the model is unable to dissipate the wave energy efficiently during a swell propagation with either source packages. It is found that TC96 formulation with the "effective wind speed" strategy performs better than WAM3 and WAM4 formulations. The wind speed correction parameter in the TC96 source package is very sensitive and needs to be calibrated and selected before the WW3 model can be applied to a specific region. 相似文献
9.
The tidal current is generally predominant in China's offshore areas. The vertical structure of the observedtidal current is quite complicated with the presence of seasonal thermocline. The observed tidal current may be divided into two parts, an averaged barotropic tide current and a variation tide current. A method for studying the vertical structure of tidal current is developed from the constitution and distribution of energy, and the vertical structure of the observed tide current in the North Huanghai Sea is studied on the basis of the method. The result shows that the reason why the energy of the tidal current is concentrated on the neighbourhood of the thermocline mainly lies in the internal tides i under certain conditions, the fact that the direction of the internal tide current above the thermocline is opposite to the one below the thermocline will be able to cause the rotary directions of the observed tidal current above and below the thermocline to be in opposite. The interaction between th 相似文献
10.
A practical algorithm of atmospheric correction for turbid coastal and inland waters is provided. The present algorithm uses the property that the water-leaving radiance at 412 nm increases very tittle with the increasing of water turbidity. Thus, in very turbid coastal and inland waters, the radiance at 412 nm can be used to estimate the aerosol scattering radiance at 865 nm. The performance of the new algorithm is validated with simulation for several cases. It is found that the retrieved remotely sensed reflectance is usually with error less than 10% for the first six bands of SeaWiFS. This new algorithm is also tested under various atmospheric conditions in the Changjiang River Estuary and the Hangzhou Bay where the sediment concentration is very high and the standard SeaWiFS atmospheric correction algorithm creates a mask due to atmospheric correction failure. The result proves the efficiency of this simple algorithm in reducing the errors of the water-leaving radiance retrieving using SeaWiFS satellite data. 相似文献
11.
Intensive Pyropia aquaculture in the coast of southwestern Yellow Sea and its subsequent waste, including disposed Ulva prolifera, was speculated to be one of the major sources for the large-scale green tide proceeding in the Yellow Sea since 2007. It was, however, unclear how the detached U. prolifera responded and resumed growing after they detached from its original habitat. In this study, we investigated the growth and photosynthetic response of the detached U. prolifera to various temperature, salinity and irradiance in the laboratory. The photosynthetic rate of the detached U. prolifera was significantly higher at moderate temperature levels(14–27°C)and high salinity(26–32), with optimum at 23°C and 32. Both low(14°C) and highest temperature(40°C), as well as low salinity(8) had adverse effects on the photosynthesis. Compared with the other Ulva species, U. prolifera showed higher saturated irradiance and no significant photoinhibition at high irradiance, indicating the great tolerance of U. prolifera to the high irradiance. The dense branch and complex structure of floating mats could help protect the thalli and reduce photoinhibition in field. Furthermore, temperature exerted a stronger influence on the growth rate of the detached U. prolifera compared to salinity. Overall, the high growth rate of this detached U. prolifera(10.6%–16.7% d~(–1)) at a wide range of temperature(5–32°C) and salinity(14–32) implied its blooming tendency with fluctuated salinity and temperature during floating. The environmental parameters in the southwestern Yellow Sea at the beginning of green tide were coincident with the optimal conditions for the detached U. prolifera. 相似文献
12.
Evaluation of ADEOS-II GLI ocean color atmospheric correction using SIMBADA handheld radiometer data
Hajime Fukushima Mitsuhiro Toratani Hiroshi Murakami Pierre-Yves Deschamps Robert Frouin Akihiko Tanaka 《Journal of Oceanography》2007,63(3):533-543
The performance of the “version 2” Global Imager (GLI) standard atmospheric correction algorithm, which includes empirical
absorptive aerosol correction and sun glint correction, was evaluated using data collected with handheld above-water SIMBADA
radiometers during 23 cruises of opportunity (research vessels, merchant ships), mostly in the North Atlantic and European
seas. A number of 100 match-up data sets of GLI-derived and SIMBADA-measured normalized water-leaving radiance (nL
W
) and aerosol optical thickness (AOT) were sorted out, using objective selection criteria, and analyzed. The Root-Mean-Square
(RMS) difference between GLI and SIMBADA nL
W
was about 0.32 μW/cm2/nm/sr for the 412 nm band, showing improvement by 30% in RMS difference with respect to the conventional “version 1” GLI
atmospheric correction algorithm, and the mean difference (or bias) was reduced significantly. For AOT, the RMS difference
was 0.1 between GLI estimates and SIMBADA measurements and the bias was small (a few 0.01), but the ?ngstr?m exponent was
systematically underestimated, by 0.4 on average, suggesting a potential GLI calibration offset in the near infrared. The
nL
W
differences were not correlated to AOT, although performance was best in very clear conditions (AOT less than 0.05 in the
865 nm band). Despite the relatively large scatter between estimated and measured nL
W
, the derived chlorophyll-a concentration estimates, applying the same ratio algorithm (GLI OC4V4) to GLI and SIMBADA, were
consistent and highly correlated in the range of 0.05–2 μg/l. The large variability in chlorophyll-a concentration estimate
for clear clean water areas (e.g. with the concentration range lower than about 0.05 μg/l) turns out to be due to the nature
of the “band ratio” based in-water algorithm. 相似文献
13.
Chlorophyll-a concentration (C chl) variations in the cross section within and outside the Peter the Great Bay shelf during different stages of the winter–spring phytoplankton bloom in 2003–2005 has been considered based on a ship (obtained during the R/V Akademik M.A. Lavrent’ev voyage of February 26 to March 9, 2003) and MODIS-Aqua spectroradiometer and the SeaWiFS color-scanner satellite data. A comparison of the C chl variability obtained from the ship and satellite data indicates that these data are inconsistent. According to satellite data obtained at the MUMM atmospheric correction, the C chl variability is distorted less than the NIR-correction data. Studying the variations in the coefficients of light absorption by the detritus and yellow substance (a dg) and light backscattering by suspended particles (b bp), C chl, chlorophyll-a fluorescence (F chl) according to the satellite data allow us to state that the variations in the discrepancy between the satellite and ship C chl values are mainly caused by the variations in the content of the detritus and yellow substance in water. Based on the satellite data, it has been revealed that the a dg values increase with increasing wind mixing after the phytoplankton bloom (about 2–5 km areas where the a dg, C chl, F chl, and bbp values abruptly increased in 2005, apparently due to eddy formation). It has been indicated that the F chl characteristic, which is close to C chl, increases when the favorable conditions for the phytoplankton bloom deteriorate. Therefore, this characteristic cannot be used to identify C chl under the indicated conditions. 相似文献
14.
The estimated characteristics of the atmospheric boundary layer, obtained by the simulation of wind wave fields using three versions of the WAM numerical model are compared with the well-known empirical dependences of drag coefficient C d on wind speed U 10 and wave age A, as well as with the dependence of dimensionless roughness height z n on inverse wave age u*/с р. Calculations carried out for several years in the areas of the Pacific and Indian oceans, based on the ERA-interim and CFSR wind reanalyses have shown good agreement between the model and empirical dependences C d (U 10) and C d (A). The range of estimated variability for z n (u*/с р ) has been found to be significantly less than empirical. It has been also found that estimated values of wind speed U 10W (t) are overestimated from 5 to 10% in all versions of WAM models compared with the input wind reanalysis U 10R (t) at the moments of appearance maximum values of wind U 10R (t). The reasons for the established features of the WAM model and their dependence on the model version are discussed. 相似文献
15.
Upper ocean heat content and atmospheric anomaly fields in the off-equatorial North Pacific related to ENSO 总被引：2，自引：1，他引：1
We have investigated interannual-scale variations of oceanic and atmospheric anomaly fields, such as upper ocean heat content (OHC), sea surface temperature (SST), latent heat flux (LHF) through the sea surface, sea level pressure (SLP) and wind stress curl (WSC) in the tropical Pacific and their relationships to El Niño/Southern Oscillation (ENSO) events. The results reported here show that the OHC and SST anomalies are almost in phase and lead LHF anomalies in the western tropical Pacific (WTP) region, which are preferable to the generation of subsequent atmospheric anomalies in the WTP. We also describe linear relationships between the amplitudes of these variables in the WTP. In addition, the results show that the both WSC and LHF anomalies are in phase with the temporal trend of OHC anomalies in the WTP, and suggest a combined effect of the local WSC and LHF anomaly in the WTP and ENSO-related, off-equatorial, westward propagating OHC anomaly to generate a large OHC anomaly in the WTP. In contrast to the WTP, OHC and SST anomalies are not in phase to the east of the WTP. The results also indicate that OHC anomalies in the WTP have a potential effect on the generation of an equatorial OHC anomaly via both a reflection of waves at the western boundary and atmospheric variations, which force the enhancement of western equatorial OHC anomaly. Therefore, the WTP is a key region where ENSO events are significantly modulated, and OHC anomalies in the WTP play an important role in the subsequent ENSO event. 相似文献
16.
V. A. Yankovsky V. A. Kuleshova R. O. Manuilova A. O. Semenov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(4):514-525
The paper presents a new model of electronic-vibrational kinetics of the products of ozone and molecular oxygen photodissociation
in the terrestrial middle atmosphere. The model includes 45 excited states of the oxygen molecules O2(b
1, Σ
g
+
,v= 0−2), O2 (a
1Δ
g
, v= 0−5), and O2(X
3Σ
g
−
, v= 1−35) and of the metastable atom O (1
D) and over 100 aeronomic reactions. The model takes into account the dependence of quantum yields of the production of O2(a
1Δ
g
, v= 0−5) in a singlet channel of ozone photolysis in the Hartley band on the wavelength of photolytic emission. Taking account
of the electronic-vibrational kinetics is important in retrieval of the vertical profiles of ozone concentration from measured
intensities of the Atm and IR Atm emissions of the oxygen bands above 65 km and leads to an increase in the ozone concentration
retrieved from the 1.27-μm emission, in contrast to the previous model of pure electronic kinetics. Sensitivity analysis of
the new model is made for variations in the concentrations of atmospheric constituents ([O2], [N2], [O(3P)], [O3], [CO2]), the gas temperature, rate constants of the reactions, and quantum yields of the reaction products. A group of reactions
that most strongly affect the uncertainty of ozone retrieval from measured intensities of atmospheric emissions of molecular
oxygen O2(b
1Σ
g
+
, v) and O2(a
1Δ
g
, v) has been determined.
Original Russian Text ? V.A. Yankovsky, V.A. Kuleshov, R.O. Manuilova, A.O. Semenov, 2007, published in Izvestiya AN. Fizika
Atmosfery i Okeana, 2007, Vol. 43, No. 4, pp. 557–569. 相似文献
17.
A. K. Zalota G. A. Kolyuchkina A. V. Tiunov S. V. Biriukova V. A. Spiridonov 《Oceanology》2017,57(2):289-297
This work concerns the trophic web positioning of the alien crab Rhithropanopeus harrisii and other common marine invertebrate species and fishes in the benthic ecosystem of the shallows of Taman Bay, Sea of Azov. The base of the trophic web in this system is composed of phytoplankton, macrophytes (algae and marine grasses), and reeds that use atmospheric carbon for photosynthesis. Analysis of the isotopic composition of nitrogen and carbon has shown that although marine grasses are dominating primary producers in the shallows of the bay, primary consumers (such as Cerastoderma glaucum, Porifera gen. sp., Gammarus aequicauda, Deshayesorchestia deshayesii and Idotea balthica) only partially use this organic source; instead, they use a combination of different sources of primary production. It has been shown that the food source of the alien crab is primarily of animal origin. In Taman Bay, R. harrisii is on the same trophic level as other carnivores/scavengers: benthic fishes Syngnathus nigrolineatus, Gobius spp. and native crab Pilumnus hirtellus and shrimp Palaemon adspersus. 相似文献
18.
The atmospheric effect on the characteristics of infrasonic signals from explosions has been studied. New methods have been proposed to remotely estimate the energy of explosions using the data of infrasonic wave registration. One method is based on the law of conservation of acoustic pulse I, which is equal to the product of the wave profile area S/2 of the studied infrasonic signal and the distance to the source EI [kt] = 1.38 × 10–10 (I [kg/s])1.482. The second method is based on the relationship between the explosion energy and the dominant period T of the recorded signal, EТ [kt] =1.02 × (Т [s]2/σ)3/2, where σ is a dimensionless distance used for determining the degree of manifestation of nonlinear effects in the propagation of sound along ray trajectories. When compared to the conventional EW (Whitaker’s) relation, the advantage of the EI relation is that it can be used for pulsed sources located at an arbitrary height over the land surface and having an arbitrary form of the initial-pulse profile and for any type of infrasonic arrivals. A distinctive feature of the expression for EТ is that the atmospheric effect on the characteristics of recorded infrasonic signals is explicitly taken into account. These methods have been tested using infrasonic data recorded at a distance of 322 km from the sources (30 explosions caused by a fire that occurred at the Pugachevo armory in Udmurtia on June 2, 2011). For the same explosion, empirical relations have been found between energy values obtained by different methods: EI = 1.107 × E W , E Т = 2.201 × E I . 相似文献
19.
Using the three-dimensional nonlinear finite-element thermohydrodynamic model QUODDY-4, we obtain two solutions giving an idea of the role of the nonlinear interaction of tidal harmonics in the formation of their spatial structure. The first solution is induced by the total tide (M 2 + S 2 + K 1 + O 1) at the open boundary and by the total static tide inside the area under consideration; then, the solution obtained is subject to harmonic analysis. The second solution is obtained by specifying such tidal sea level elevations at the open boundary that meet individual tidal harmonics. These two solutions are compared. It is shown that the differences between the solutions for the S 2, K 1, and O 1 waves can be significant, especially near the open boundary between the White and Barents seas. This conclusion remains valid also for the maximum velocities (major semiaxes of the ellipses) of the barotropic (depth-average) tidal current as well as for the average (over the tidal cycle) densities of the total tidal energy and components of the tidal-energy budget. The emergence of this feature indicates that there are resonance modes with frequencies that differ from those of the S 2, K 1, and O 1 harmonics to a lesser extent than the M 2 harmonic frequency. The same conclusion can be made by comparing the values of the amplification factor, which is defined as the ratio between the actual and static tides, for the system of the Barents and White seas as a whole and for Mezen Bay in the White Sea and Czech Bay in the Barents Sea, taken separately. 相似文献
20.
Phytoplankton and bacteria diversity were studied before, during and after red tide phenomena during spring season 2015 in the Eastern Harbour (E.H.) of Alexandria, Egypt. Fifty five species of phytoplankton were identified and represented different distinct classes “Bacillariophyceae; Dinophyceae, Chlorophyceae, Cyanophyceae and Eugelenophyceae”. Also, Diatom formed the most dominant group. The average number of the phytoplankton density varied from 4.8 × 104 to 1.1 × 106 cell l-1 during the study period and Skeletonema costatum was the agent causing the red tide. The existence percentages of bacteria ranged from 2.6 to 17.9% on all media tested. The bacterial isolates on the nutrient agar medium represented the highest existence with a total percentage of 43.6%, followed by MSA medium (25.7%), while the lowest percentage was for the AA medium at 7.8%. However, twelve isolates were selected as representative for bacterial community during study interval. Based on the morphological, biochemical, physiological and enzymatic characteristics, the bacterial strains were described. Depending on the 16S rDNA gene sequence, three common antagonists were aligned as: Vibrio toranzoniae strain Vb 10.8, Ruegeria pelagia strain NBRC 102038 and Psychrobacter adeliensis strain DSM 15333. The interaction between these bacteria and S. costatum was studied. The growth of S. costatum was significantly lower whenever each bacterium was present as compared to axenic culture. More specifically, 30% (v/v) of the all tested bacteria showed the strongest algicidal activities, as all S. costatum cells were killed after two days. 10% of R. pelagia and P. adeliensis also showed significant algicidal activities within six days. 相似文献