Implementing the coherence matrix of the partially polarized wave to enhance efficiency of radar observation of the objects

В статье обоснована возможность радиолокационного наблюдения объектов при наличии атмосферного фона. Радиолокационное наблюдение объектов при наличии мешающего фона основано на выделении эхо-сигнала объекта из суммарного эхо-сигнала (объект+фон) по их поляризационному различию. При этом использована матрица когерентности частично поляризованной волны, позволившая установить структуру ее флуктуирующей компоненты. Элементами матрицы когерентности являются действительные параметры Стокса, которые измеряются на выходе приемника судовой РЛС. Отраженная от навигационного объекта и атмосферного фона электромагнитная волна является частично поляризованной и ее полная интенсивность равна сумме интенсивностей стабильной и флюктуирующей компонент. Элементы флюктуирующей компоненты матрицы когерентности отражают поляризационную структуру частично поляризованной волны и представляют дисперсии случайных поляризационных параметров Стокса и их статистическую связь. Для неполяризованной волны матрица когерентности является диагональной в любом поляризационном базисе. Суммарная матрица когерентности позволяет получить информацию о поляризации частично поляризованной волны, отраженной от навигационного объекта и атмосферного фона. Необходимым условием дистанционного радиолокационного наблюдения навигационных объектов, находящихся в зоне атмосферного фона, является разделение эхо-сигнала на эхо-сигнал навигационного объекта и эхо-сигнал атмосферного образования. Отраженная от навигационного объекта и атмосферного фона электромагнитная волна является частично поляризованной и ее полная интенсивность равна сумме интенсивностей стабильной и флюктуирующей компонент. Элементы флюктуирующей компоненты матрицы когерентности отражают поляризационную структуру частично поляризованной волны и представляют дисперсии случайных поляризационных параметров Стокса и их статистическую связь. Для неполяризованной волны матрица когерентности является диагональной в любом поляризационном базисе. Суммарная матрица когерентности позволяет получить информацию о поляризации частично поляризованной волны, отраженной от навигационного объекта и атмосферного фона. Необходимым условием дистанционного радиолокационного наблюдения навигационных объектов, находящихся в зоне атмосферного фона, является разделение эхо-сигнала на эхо-сигнал навигационного объекта и эхо-сигнал атмосферного образования. This article substantiates the possibility of radar observation of objects in the presence of atmospheric background. In the presence of an interfering background the radar observation of objects is based on the separation of the object's echo signal from the general echo signal (object + background) in accordance with its polarization difference. Therefore, the coherence matrix of a partially polarized wave is used, which allows to establish the structure of its fluctuating component. The elements of the coherence matrix are the actual Stokes parameters, which are measured at the output of the ship's radar receiver. The electromagnetic wave reflected from the navigation object and the atmospheric background is partially polarized and its total intensity is equal to the sum of the intensities of the stable and fluctuating components. The elements of the fluctuating component of the coherence matrix reflect the polarization structure of the partially polarized wave and represent the variances of the random Stokes polarization parameters and their statistical relationship. For an unpolarized wave, the coherence matrix is ​​diagonal in any polarization basis. The total coherence matrix provides information on the polarization of a partially polarized wave reflected from the navigation object and the atmospheric background. A necessary condition for remote radar observation of navigation objects located in the atmospheric background zone is the separation of the echo signal into the echo signal of the navigation object and the echo signal of the atmospheric formation. According to the Stokes theorem, the echo signal of a partially polarized wave is decomposed into polarized and unpolarized components. A fully polarized component of a total partially polarized wave has only one type of polarization — linear, circular, or elliptical. The unpolarized component does not have any predominant polarization. The echo signal of the total partially polarized wave is considered as a result of the addition of the intensities of two independent fully polarized components. The polarization of the first component corresponds to the echo signal of the navigation object, and the polarization of the second component corresponds to the echo signal of the atmospheric formation.

Development of a potential energy surface for the O3–Ar system: rovibrational states of the complex

Collisional stabilization is an important step in the process of atmospheric formation of ozone.

Formation of polyaromatic hydrocarbon (PAH)-quinones during the gas phase reactions of PAHs with the OH radical in the atmosphere

Environmental context Atmospheric quinones present a potential toxic risk to human health because of their involvement in the generation of reactive oxygen species. Gas phase reactions of naphthalene and phenanthrene with the OH radical are investigated in a laboratory reaction chamber to provide a preliminary assessment of the importance of the atmospheric formation of quinones. Abstract In light of the potential toxicity of quinones (QNs) to human health, previous studies carried out measurement of QNs in ambient air samples and from motor vehicle emissions to understand the characteristics and the sources of QNs in the atmosphere. The major compounds observed in the ambient air samples comprised two and three benzene rings and included polyaromatic hydrocarbon (PAH)-quinones (PAH-QNs) such as 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), 9,10-phenanthrenequinone (9,10-PQ) and 9,10-anthraquinone (9,10-AQ). Although these PAH-QNs are found in vehicular emissions, they may also be formed by the photochemical reactions of gas phase PAHs with atmospheric oxidants. In this study, to allow an assessment of the importance of the atmospheric formation of PAH-QNs and to understand more clearly the sources of PAH-QNs in the atmosphere, the formation yields of PAH-QNs from the gas phase reactions of naphthalene and phenanthrene with the OH radical were observed in a laboratory reaction chamber. In addition, the phase distribution of the PAH-QNs was determined. For naphthoquinones (NQs), the formation yields of 1,4-NQ and 1,2-NQ were 1.5±0.4 and 5.1±2.7% respectively. The measured yields of PQs were 3.6±0.8% for 9,10-PQ and 2.7±1.1% for 1,4-PQ. From the measured yield data, the atmospheric formation of PAH-QNs was estimated and the importance of the atmospheric formation of PAH-QNs from the gas phase reaction of PAHs with the OH radical is discussed.

Atmospheric formation of the NO3 radical from gas-phase reaction of HNO3 acid with the NH2 radical: proton-coupled electron-transfer versus hydrogen atom transfer mechanisms

The amidogen radical abstracts the hydrogen from nitric acid through a proton coupled electron transfer mechanism rather than by an hydrogen atom transfer process.

Receptor modelling of secondary particulate matter at UK sites

Complementary approaches have been taken to better understand the sources and their spatial distribution for secondary inorganic (nitrate and sulphate) and secondary organic aerosol sampled at a rural site (Harwell) in the southern United Kingdom. A concentration field map method was applied to 1581 daily samples of chloride, nitrate and sulphate from 2006 to 2010, and 982 samples for organic carbon and elemental carbon from 2007 to 2010. This revealed a rather similar pattern of sources for nitrate, sulphate and secondary organic carbon within western/central Europe, which in the case of nitrate and sulphate, correlated significantly with EMEP emissions maps of NOx and SO2. A slightly more southerly source emphasis for secondary organic carbon may reflect the contribution of biogenic sources. Trajectory clusters confirm this pattern of behaviour with a major contribution from mainland European sources. Similar behaviours of, on the one hand, sulphate and organic carbon and, on the other hand, EC and nitrate showed that the former are more subject to regional influence than the latter in agreement with the slower atmospheric formation of sulphate and secondary organic aerosol than for nitrate, and the local/mesoscale influences upon primary EC. In a separate study, measurements of sulphate, nitrate, elemental and organic carbon were made in 100 simultaneously collected samples at Harwell and at a suburban site in Birmingham (UK). This showed a significant correlation in concentrations between the two sites for all of the secondary constituents, further indicating secondary organic aerosol to be a regional pollutant behaving similarly to sulphate and nitrate.