To investigate aerosol optical properties in the Beijing metropolitan area,aerosol absorption coefficient(Ab) ,scattering coefficient(Sc) ,and fine particulate matter(PM2.5) were measured in the Beijing urban area from 20 May to 30 August 2009.The average Ab,Sc,single scattering albedo(SSA) ,and PM2.5 concentration were 58.0±39.5 M m-1,343.5±353.7 M m-1,0.80±0.10 and 63.6±50.0-g m-3,respectively,during the observation period.Ab,Sc,and SSA all showed single peak diurnal variations,with their maximum values being measured at 0500,1000,and 1300 local time,respectively.Ab and Sc had a strong positive correlation with PM2.5,and Ab,Sc,and PM2.5 all had positive correlations with relative humidity and negative correlations with wind speed.
Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical properties of aerosols were conducted in July 2008 at an urban site in Guangzhou,Southern China.The mean PM 2.5 concentration for the entire period was 53.7±23.2 μg m 3.The mean PM 2.5 concentration (82.7±25.4 μg m 3) on hazy days was roughly two times higher than that on clear days (38.8±8.7 μg m 3).The total water-soluble ion species and the total average carbon accounted for 47.9%±4.3% and 35.2%±4.5%,respectively,of the major components of PM 2.5.The increase of secondary and carbonaceous aerosols,in particular ammonium sulfate,played an important role in the formation of haze pollution.The mean absorption and scattering coefficients and the single scattering albedo over the whole period were 53±20 M m 1,226±111 M m 1,and 0.80±0.04,respectively.PM 2.5 had a high linear correlation with the aerosol extinction coefficient,elemental carbon (EC) was correlated with aerosol absorption,and organic carbon (OC) and SO 4 2 were tightly linked to aerosol scattering.
The radiance lights data in 2006 from the National Oceanic and Atmospheric Administration Air Force Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) and authoritative energy data distributed by the United State Energy Information Administration were applied to estimate the global distribution of anthropogenic heat flux.A strong linear relationship was found to exist between the anthropogenic heat flux and the DMSP/OLS radiance data.On a global scale,the average value of anthropogenic heat flux is approximately 0.03 W m 2 and 0.10 W m 2 for global land area.The results indicate that global anthropogenic heat flux was geographically concentrated and distributed,fundamentally correlating to the economical activities.The anthropogenic heat flux concentrated in the economically developed areas including East Asia,Europe,and eastern North America.The anthropogenic heat flux in the concentrated regions,including the northeastern United States,Central Europe,United Kingdom,Japan,India,and East and South China is much larger than global average level,reaching a large enough value that could affect regional climate.In the center of the concentrated area,the anthropogenic heat flux density may exceed 100 W m 2,according to the results of the model.In developing areas,including South America,Central and North China,India,East Europe,and Middle East,the anthropogenic heat flux can reach a level of more than 10 W m 2 ;however,the anthropogenic heat flux in a vast area,including Africa,Central and North Asia,and South America,is low.With the development of global economy and urban agglomerations,the effect on climate of anthropogenic heat is essential for the research of climate change.
A large number of experimental and theoretical investigations of carbon dioxide (CO 2 ) spectra have been conducted since the most recent update of the High-Resolution Transmission Molecular Absorption (HITRAN) database. To maintain optimal parameters, the HITRAN 2004 CO 2 line list has been completely replaced by HITRAN 2008 data in the near-infrared region from 4300 cm-1 to 7000 cm-1 . To examine the effect of this change on the retrieval of CO 2 vertical column data from reflected sunlight spectra in the 1.61-μm spectral window, synthetic measurements for a given atmospheric state and instrument setup were generated and compared using radiative transfer model with the line-transition parameters from the HITRAN 2004 and 2008 databases. Simulated retrievals were then performed based on the optimal estimation retrieval theory. The results show that large systematic errors in atmospheric CO 2 column retrievals were induced by the differences in the HITRAN laboratory line parameters in the 1.61-μm region. The retrieved CO 2 columns were underestimated by >10 ppm using the HITRAN 2004 data, and improvements resulting from the use of the improved HITRAN database were more pronounced at a higher spectral resolution.
High-quality In0.2Ga0.8N epilayers were grown on a GaN template at temperatures of 520 and 580℃via plasma-assisted molecular beam epitaxy.The X-ray rocking curve full widths at half maximum（FWHM） of（10.2） reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature.When the growth temperature increases to 580℃,the FWHM of（00.2） reflections for these samples is very narrow and keeps similar,while significant improvement of（10.2） reflections with an FWHM value of 612 arcsec has been observed.This improved quality in InGaN layers grown at 580℃is also reflected by the much larger size of the crystalline column from the AFM results,stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.
PM2.5 aerosols were sampled in urban Chengdu from April 2009 to January 2010, and their chemical compositions were characterized in detail for elements, water soluble inorganic ions, and carbonaceous matter. The annual average of PM2.5 was 165 μg m-3 , which is generally higher than measurements in other Chinese cities, suggesting serious particulate pollution issues in the city. Water soluble ions contributed 43.5% to the annual total PM2.5 mass, carbonaceous aerosols including elemental carbon and organic carbon contributed 32.0%, and trace elements contributed 13.8%. Distinct daily and seasonal variations were observed in the mass concentrations of PM2.5 and its components, reflecting the seasonal variations of different anthropogenic and natural sources. Weakly acidic to neutral particles were found for PM2.5 . Major sources of PM2.5 identified from source apportionment analysis included coal combustion, traffic exhaust, biomass burning, soil dust, and construction dust emissions. The low nitrate: sulfate ratio suggested that stationary emissions were more important than vehicle emissions. The reconstructed masses of ammonium sulfate, ammonium nitrate, particulate carbonaceous matter, and fine soil accounted for 79% of the total measured PM2.5 mass; they also accounted for 92% of the total measured particle scattering.
Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by nu- merical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth's Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.
Based on the integrating sphere traced from the National Institute of Standards and Technology(NIST,USA), a sphere calibration method and protocol for the China aerosol remote sensing network(CARSNET)Cimel sun photometer was established. Four CE318 sun photometers were verified using the proposed calibration method and operational protocol. The calibration results showed that the instrument coefficients differed by less than 3% for visible(~5% for infrared) wavelengths from the original ones stated by Cimel Electronique. In situ validation experiment data showed that radiances at ±6° measured by sun collimator(aureole) were consistent with those measured by sky collimator(sky), under both almucantar(ALMUC)^nd principal plane(PPLAN) scenarios. Differences at all wavelengths were less than 1%, indicating that the method and protocol are suitable for CARSNET field sun photometer calibration, and would benefit improvement of data quality and accuracy of network observations.
Stable light data from Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) satellites and authoritative energy consumption data distributed by National Bureau of Statistics of China were applied to estimating the distribution of anthropogenic heat release in China from 1992 to 2009. A strong linear relationship was found between DMSP/OLS digital number data and anthropogenic heat flux density (AHFD). The results indicate that anthropogenic heat release in China was geographically concentrated and was fundamentally correlated with economic activities. The anthropogenic heat release in economically developed areas in northern, eastern, and southern China was much larger than other regions, whereas it was very small in northwestern and southwestern China. The mean AHFD in China increased from 0.07 W m-2 in 1978 to 0.28 W m-2 in 2008. The results indicate that in the anthropogenic heat-concentrated regions of Beijing, the Yangtze River Delta, and the Pearl River Delta, the AHFD levels were much higher than the average. The effect of aggravating anthropogenic heat release on climate change deserves further investigation.
The line-transition parameters of the High Resolution Transmission (HITRAN) 2008 database have been updated relative to previous editions. The transmission spectra and sensitivity to changes in CO2 concentrations using line parameters from the HITRAN 2004 and HITRAN 2008 databases are compared to evaluate the effect of the database updates on retrievals of carbon dioxide vertical columns from nearinfrared reflected sunlight. This comparison is done in three spectral regions covering the 2.06-, 1.61-, and 1.58-μm CO2bands used by the Greenhouse Gases Observatory Satellite (GOSAT) instrument and the planned successor to the Orbiting Carbon Observatory (OCO). The updates to the HITRAN database have the largest effects on the transmittance and the off-line to on-line transmittance ratio in the 2.06-μm region and the smallest effects on these parameters in the 1.58-μm region. The influence of the updates to the HITRAN database on the off-line to on-line ratio calculation in the narrow spectral region 4855-4880 cm-1 could be equivalent to a change in CO2 of more than 50 ppmv. Use of the HITRAN 2004 database will lead to an underestimate of the column CO2abundance in the 2.06- and 1.61-μm spectral regions, whereas it will lead to an overestimate of the column CO2abundance in the 1.58-μm spectral region.
