174 research outputs found

    Model and In-Situ Salinity Variability in the Tropical Pacific

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    Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

    Impacts of Two Types of El NiƱo and La NiƱa Events on Typhoon Activity

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    The HadISST (Hadley Centre Sea Ice and Sea Surface Temperature) dataset is used to define the years of El NiƱo, El NiƱo Modoki, and La NiƱa events and to find out the impacts of these events on typhoon activity. The results show that the formation positions of typhoon are farther eastward moving in El NiƱo years than in La NiƱa years and much further eastward in El NiƱo Modoki years. The lifetime and the distance of movement are longer, and the intensity of typhoons is stronger in El NiƱo and in El NiƱo Modoki years than in La NiƱa years. The Accumulated Cyclone Energy of typhoon is highly correlated with the Oceanic NiƱo Index with a correlation coefficient of 0.79. We also find that the typhoons anomalously decrease during El NiƱo years but increase during El NiƱo Modoki years. Besides, there are two types of El NiƱo Modoki, I and II. The intensity of typhoon in El NiƱo Modoki I years is stronger than in El NiƱo Modoki II years. Furthermore, the centroid position of the Western Pacific Warm Pool is strongly related to the area of typhoon formation with a correlation coefficient of 0.95

    Hyperspectral sensing for turbid water quality monitoring in freshwater rivers: Empirical relationship between reflectance and turbidity and total solids

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    Total suspended solid (TSS) is an important water quality parameter. This study was conducted to test the feasibility of the band combination of hyperspectral sensing for inland turbid water monitoring in Taiwan. The field spectral reflectance in the Wu river basin of Taiwan was measured with a spectroradiometer; the water samples were collected from the different sites of the Wu river basin and some water quality parameters were analyzed on the sites (in situ) as well as brought to the laboratory for further analysis. To obtain the data set for this study, 160 in situ sample observations were carried out during campaigns from August to December, 2005. The water quality results were correlated with the reflectivity to determine the spectral characteristics and their relationship with turbidity and TSS. Furthermore, multiple-regression (MR) and artificial neural network (ANN) were used to model the transformation function between TSS concentration and turbidity levels of stream water, and the radiance measured by the spectroradiometer. The value of the turbidity and TSS correlation coefficient was 0.766, which implies that turbidity is significantly related to TSS in the Wu river basin. The results indicated that TSS and turbidity are positively correlated in a significant way across the entire spectrum, when TSS concentration and turbidity levels were under 800 mgĀ·L(-1) and 600 NTU, respectively. Optimal wavelengths for the measurements of TSS and turbidity are found in the 700 and 900 nm range, respectively. Based on the results, better accuracy was obtained only when the ranges of turbidity and TSS concentration were less than 800 mgĀ·L(-1) and less than 600 NTU, respectively and used rather than using whole dataset (R(2) = 0.93 versus 0.88 for turbidity and R(2) = 0.83 versus 0.58 for TSS). On the other hand, the ANN approach can improve the TSS retrieval using MR. The accuracy of TSS estimation applying ANN (R(2) = 0.66) was better than with the MR approach (R(2) = 0.58), as expected due to the nonlinear nature of the transformation model

    Orderly arranged NLO materials on exfoliated layeredtemplates based on dendrons with alternating moietiesat the peripheryā€ 

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    Nonlinear optical dendrons with alternating terminal groups of the stearyl group (C18) and chromophorewere prepared through a convergent approach. These chromophore-containing dendrons were used asthe intercalating agents for montmorillonite via an ion-exchange process. An orderly exfoliatedmorphology is obtained by mixing the dendritic structure intercalated layered silicates with a polyimide.As a result, optical nonlinearity, i.e. the Pockels effect was observed for these nanocomposites withoutresorting to the poling process. EO coefficients of 9ā€“22 pm V 1 were achieved despite that relativelylow NLO densities were present in the nanocomposites, particularly for the samples comprising thedendrons with alternating moieties. In addition, the hedging effects of the stearyl group on the selfalignmentbehavior, electro-optical (EO) coefficient and temporal stability of the dendron-intercalatedmontmorillonite/polyimide nanocomposites were also investigated

    Local Magnetic Field Role in Star Formation

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    We highlight distinct and systematic observational features of magnetic field morphologies in polarized submm dust continuum. We illustrate this with specific examples and show statistical trends from a sample of 50 star-forming regions.Comment: 4 pages, 3 figures; to appear in the EAS Proceedings of the 6th Zermatt ISM Symposium "Conditions and Impact of Star Formation from Lab to Space", September 201
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