Inelastic vibrational Raman scattering by liquid water is one significant limitation to the accuracy of the retrieval of trace gas constituents in atmosphere over waters, particularly over clear ocean waters, while using satellite data with differential optical absorption spectroscopy technique (DOAS). The effect which is similar to the Ring effect in atmosphere results in the filling-in of Fraunhofer lines, which is known as solar absorption lines. The inelastic component of the liquid water scattering causes a net increase of radiance in the line because more radiations shift to the wavelength of an absorption line than from this wavelength to other wavelengths. The solar spectrum transmitting atmosphere is convolved with vibrational Raman scattering coefficient of liquid water, divided by the original computed spectrum, with a cubic polynomial subtracted off, to create differential water Ring spectrum. This method is suggested in order to obtain an effective differential water Ring coeffient for the DOAS fitting process, which could be used to improve the accuracy of the retrieval of the trace gases concentration. The method does not rely on radiative transfer model of water, which would be time-consuming and depending on lot of parameters. Therefore, it is very fast and convenient.
Three typical polluted dust particles (i.e., single coated dust, two-sphere/spheroid system, and coated dust with aggregate) including internal and semi-external mixtures are modeled, and their scattering properties at 1.6-μm wavelength are calculated by using the generalized multi-sphere Mie-solution (GMM) method. We investigate the influences of particle size, morphology, and chemical composition on the scattering parameters of polluted dust particles. The analysis results demonstrate that the single scattering albedo of coated dust is much smaller than that of pure dust, especially for the spheroidal black carbon (BC) coated dust. When a dust particle semi-mixes with another aerosol particle to form a two-sphere/spheroid system, its scattering properties are much more sensitive to the size and species of monomers than the monomer shape. If an aggregated BC attaches to the coated dust, the scattering properties of whole particle mainly depend on the host particle (coated dust).
Global climate change is one of the most challenging issues facing the world today. Atmospheric aerosols and carbon dioxide (CO 2 ), as two key factors driving the global climate change, have earned enormous attention from scientist around the world [1]. One challenge for the satellite measurements of CO 2 using this SWIR wavelength range (∼1.6µm) is the impact of multiple scattering by aerosols and cirrus [2]. Since the rapid economic growth and associated increase in fossil fuel consumption have caused serious particulate pollution in many regions of China [3], remote sensing of CO 2 using SWIR band in China needs to pay more attention to the scattering properties of aerosol particles and the multiple scattering. Considering the complexity of morphological and chemical properties, aerosol particles are grouped based on a large number of TEM/SEM images, and then their scattering properties at 1.6µm band are calculated by the T-matrix method [4] and GMM method [5]. In this study, the Monte Carlo method is used to solve the multiple scattering problem by simulating photons transport in the scattering media. We combined this multiple scattering model with the LBLRTM [6] as a forward radiative transfer model for studying the impact of aerosol scattering on the satellite observations of CO 2 using SWIR band. Finally, based on the GOCART aerosol component products, AERONET aerosol size distribution products, CALIPSO aerosol profile products, and MODIS aerosol optical depth and surface albedo products, the monthly variability of errors in CO 2 concentrations over China were calculated and analyzed. The results indicate that AOD and surface albedo are two of most important factors for the satellite observations of CO 2 . For low surface albedo, the retrieved CO 2 columns are undervalued when aerosol scattering is neglected. While for moderate and high surface albedos, the retrieved CO 2 columns are overvalued. As shown in Fighre 1, CO 2 concentrations are overestimated in western regions of China, especially in desert areas (a maximum of ∼7.08% in September), and those are underestimated in eastern regions (a minimum of ∼−6.9% in June).
It has been found that the concentration of atmospheric methane (CH4) has rapidly increased since 2007 after a decade of nearly constant concentration in the atmosphere. As an important greenhouse gas, such an increase could enhance the threat of global warming. To better quantify this increasing trend, a novel statistic method, i.e. the Ensemble Empirical Mode Decomposition (EEMD) method, was used to analyze the CH4 trends from three different measurements: the mid–upper tropospheric CH4 (MUT) from the space-borne measurements by the Atmospheric Infrared Sounder (AIRS), the CH4 in the marine boundary layer (MBL) from NOAA ground-based in-situ measurements, and the column-averaged CH4 in the atmosphere (XCH4) from the ground-based up-looking Fourier Transform Spectrometers at Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC). Comparison of the CH4 trends in the mid–upper troposphere, lower troposphere, and the column average from these three data sets shows that, overall, these trends agree well in capturing the abrupt CH4 increase in 2007 (the first peak) and an even faster increase after 2013 (the second peak) over the globe. The increased rates of CH4 in the MUT, as observed by AIRS, are overall smaller than CH4 in MBL and the column-average CH4. During 2009–2011, there was a dip in the increase rate for CH4 in MBL, and the MUT-CH4 increase rate was almost negligible in the mid-high latitude regions. The increase of the column-average CH4 also reached the minimum during 2009–2011 accordingly, suggesting that the trends of CH4 are not only impacted by the surface emission, however that they also may be impacted by other processes like transport and chemical reaction loss associated with [OH]. One advantage of the EEMD analysis is to derive the monthly rate and the results show that the frequency of the variability of CH4 increase rates in the mid–high northern latitude regions is larger than those in the tropics and southern hemisphere.
PM2.5 has become one of the primary pollutants in China, and heavy smogs usually occurred over the eastern China in recent years. Some scientific issues such as the sources of the fine particles, the formation mechanism of the severe pollutions and the interactions between air quality and regional climate change, are hot points in the field of air quality monitoring and modeling studies. Satellite remote sensing has been recognized as an important and effective approach to analyze these scientific issues. We have developed a series of retrieval algorithms to assess the spatial and temporal variations of haze pollutions, aerosols, gaseous pollutants, and greenhouse gases (GHGs). This paper puts forward three directions of future research in atmospheric environment remote sensing in China. The first one is to improve the satellite retrieving methods of atmospheric components in order to better quantify their amounts over China. The second one is to enhance the performance of atmospheric models by refining emission inventory and by assisting the source apportionment of pollutants based on satellite data. So far, there are still many unclear problems concerning atmospheric emissions and formation processes of the haze clouds, which may introduce large uncertainties in model simulations. The last one is to advance our understanding of the complex interactions between haze clouds and regional climate change in the eastern China.
Abstract Axillary bud is an important aspect of plant morphology, contributing to the final tobacco yield. However, the mechanisms of axillary bud development in tobacco remain largely unknown. To investigate this aspect of tobacco biology, the metabolome and proteome of the axillary buds before and after topping were compared. A total of 569 metabolites were differentially abundant before and 1, 3, and 5 days after topping. KEGG analyses further revealed that the axillary bud was characterized by a striking enrichment of metabolites involved in flavonoid metabolism, suggesting a strong flavonoid biosynthesis activity in the tobacco axillary bud after topping. Additionally, 9035 differentially expressed proteins (DEPs) were identified before and 1, 3, and 5 days after topping. Subsequent GO and KEGG analyses revealed that the DEPs in the axillary bud were enriched in oxidative stress, hormone signal transduction, MAPK signaling pathway, and starch and sucrose metabolism. The integrated proteome and metabolome analysis revealed that the indole-3-acetic acid (IAA) alteration in buds control dormancy release and sustained growth of axillary bud by regulating proteins involved in carbohydrate metabolism, amino acid metabolism, and lipid metabolism. Notably, the proteins related to reactive oxygen species (ROS) scavenging and flavonoid biosynthesis were strongly negatively correlated with IAA content. These findings shed light on a critical role of IAA alteration in regulating axillary bud outgrowth, and implied a potential crosstalk among IAA alteration, ROS homeostasis, and flavonoid biosynthesis in tobacco axillary bud under topping stress, which could improve our understanding of the IAA alteration in axillary bud as an important regulator of axillary bud development.
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