DSCOVR_EPIC_L2_AER_01

Atmospheric Science Data Center

2018-04-23

DSCOVR_EPIC_L2_AER_01 The Aerosol UV product provides aerosol and UV products in three tiers. Tier 1 products include Absorbing Aerosol Index (AAI) and above-cloud-aerosol optical depth (ACAOD). Tier 2 ...

An operational retrieval algorithm for determining aerosol optical properties in the ultraviolet

NASA Astrophysics Data System (ADS)

Taylor, Thomas E.; L'Ecuyer, Tristan S.; Slusser, James R.; Stephens, Graeme L.; Goering, Christian D.

2008-02-01

This paper describes a number of practical considerations concerning the optimization and operational implementation of an algorithm used to characterize the optical properties of aerosols across part of the ultraviolet (UV) spectrum. The algorithm estimates values of aerosol optical depth (AOD) and aerosol single scattering albedo (SSA) at seven wavelengths in the UV, as well as total column ozone (TOC) and wavelength-independent asymmetry factor (g) using direct and diffuse irradiances measured with a UV multifilter rotating shadowband radiometer (UV-MFRSR). A novel method for cloud screening the irradiance data set is introduced, as well as several improvements and optimizations to the retrieval scheme which yield a more realistic physical model for the inversion and increase the efficiency of the algorithm. Introduction of a wavelength-dependent retrieval error budget generated from rigorous forward model analysis as well as broadened covariances on the a priori values of AOD, SSA and g and tightened covariances of TOC allows sufficient retrieval sensitivity and resolution to obtain unique solutions of aerosol optical properties as demonstrated by synthetic retrievals. Analysis of a cloud screened data set (May 2003) from Panther Junction, Texas, demonstrates that the algorithm produces realistic values of the optical properties that compare favorably with pseudo-independent methods for AOD, TOC and calculated Ångstrom exponents. Retrieval errors of all parameters (except TOC) are shown to be negatively correlated to AOD, while the Shannon information content is positively correlated, indicating that retrieval skill improves with increasing atmospheric turbidity. When implemented operationally on more than thirty instruments in the Ultraviolet Monitoring and Research Program's (UVMRP) network, this retrieval algorithm will provide a comprehensive and internally consistent climatology of ground-based aerosol properties in the UV spectral range that can be used for both validation of satellite measurements as well as regional aerosol and ultraviolet transmission studies.

Global Distribution of Dust, Smoke, Volcanic Ash, and Pollutant Aerosols Seen from Space

NASA Technical Reports Server (NTRS)

Herman, Jay R.; Hsu, Christina; Krotkov, Nickolay; Torres, Omar

1998-01-01

New technique for observing aerosols from space, using ultraviolet (UV) wavelengths, have been developed during the past three years. The chief benefit from observing aerosols in the UV is that they are easily visible over both land and water. While there is presently more than one satellite that can observe aerosols in the UV, only Total Ozone Mapping Spectrometer (TOMS) has a long-term record (since 1979) and adequate spatial resolutions (50 to 100 km) to observe the seasonal and interannual variations, and to locate some of the land sources of dust, smoke, volcanic ash and sulfate pollutants. The data has been assembled into daily images of the atmospheric aerosol loading in terms of optical depth and UV transmittance. For the major sources of aerosols, it is common for at least 50% of the total UV to be absorbed underneath aerosol plumes. This is particularly true for the spectacular smoke plumes originating from the recent Indonesian and Mexican fires, as well as under the huge African dust plumes. The sulfate pollutants are mostly present in the Northern Hemisphere and are associated with regions of high industrial activity. The location and seasonal dependence of these aerosol plumes over Europe and North America will be contrasted with the relatively clean Southern Hemisphere. Because of the success of this technique, it has formed the basis for a new generation of space-borne aerosol detection instruments. These new instruments combine the UV observations with the more traditional visible-wavelength data to obtain a more comprehensive characterization of aerosols that is possible with either UV or visible techniques by themselves.

Aerosol Absorption Effects in the TOMS UV Algorithm

NASA Technical Reports Server (NTRS)

Torres, O.; Krotkov, N.; Bhartia, P. K.

2004-01-01

The availability of global long-term estimates of surface UV radiation is very important, not only for preventive medicine considerations, but also as an important tool to monitor the effects of the stratospheric ozone recovery expected to occur in the next few decades as a result of the decline of the stratospheric chlorine levels. In addition to the modulating effects of ozone and clouds, aerosols also affect the levels of UV-A and W-B radiation reaching the surface. Oscillations in surface W associated with the effects of aerosol absorption may be comparable in magnitude to variations associated with the stratospheric ozone recovery. Thus, the accurate calculation of surface W radiation requires that both the scattering and absorption effects of tropospheric aerosols be taken into account. Although absorption effects of dust and elevated carbonaceous aerosols are already accounted for using Aerosol Index technique, this approach does not work for urban/industrial aerosols in the planetary boundary layer. The use of the new TOMS long-term global data record on UV aerosol absorption optical depth, can improve the accuracy of TOMS spectral UV products, by properly including the spectral attenuation effects of carbonaceous, urban/industrial and mineral aerosols. The TOMS data set on aerosol properties will be discussed, and results of its use in the TOMS surface W algorithm will be presented.

Developing an Approach to Model UV Fluxes in Smoke Laden Conditions over Central Asia

NASA Astrophysics Data System (ADS)

Park, Y. H.; Sokolik, I. N.

2016-12-01

The UV characteristics of smoke aerosols are valuable inputs to the UV Index forecasts, air quality studies, and assessments of the impact of regional environmental changes. The wavelength dependence of light absorption by aerosol particles is pronounced throughout the UV spectral region. Also in assumption that smoke consists of BC, OC, and Sulfate, the mass fraction of smoke is different with fire types. The purpose of this study is to introduce an approach to calculate the UV fluxes in the aerosol laden conditions, and investigate the irradiance compared to measured irradiance in the UV spectrum. To compute the spectral optical properties (e.g., the effective single scattering albedo, asymmetry parameter, and aerosol optical thickness) for the selected scenarios, the representative size distribution and the refractive index are selected and used in the Mie code. Smoke aerosol information (e.g. emission injection height, mass concentration of smoke components) from WRF Chem is applied to run tropospheric ultraviolet and visible (TUV) model. Using the TUV model, we make the comparisons between model and measured irradiance in UV spectrum in smoke aerosol conditions. An advantage of this approach and the uncertainty of the evaluation are discussed. Overall, the results of this investigation show that this approach is valuable to estimate UV fluxes in smoke laden conditions.

Discussion of vicarious calibration of GOSAT/TANSO-CAI UV-band (380nm) and aerosol retrieval in wildfire region in the OCO-2 and GOSAT observation campaign at Railroad Valley in 2016

NASA Astrophysics Data System (ADS)

Hashimoto, M.; Kuze, A.; Bruegge, C. J.; Shiomi, K.; Kataoka, F.; Kikuchi, N.; Arai, T.; Kasai, K.; Nakajima, T.

2016-12-01

The GOSAT (Greenhouse Gases Observing Satellite) / TANSO-CAI (Cloud and Aerosol Imager, CAI) is an imaging sensor to measure cloud and aerosol properties and observes reflected sunlight from the atmosphere and surface of the ground. The sensor has four bands from near ultraviolet (near-UV) to shortwave infrared, 380, 674, 870 and 1600nm. The field of view size is 0.5 km for band-1 through band-3, and 1.5km for band-4. Band-1 (380nm) is one of unique function of the CAI. The near-UV observation offers several advantages for the remote sensing of aerosols over land: Low reflectance of most surfaces; Sensitivity to absorbing aerosols; Absorption of trace gases is weak (Höller et al., 2004). CAI UV-band is useful to distinguish absorbing aerosol (smoke) from cloud. GOSAT-2/TANSO-CAI-2 that will be launched in the future also has UV-bands, 340 and 380nm. We carried out an experiment to calibrate CAI UV-band radiance using data taken in a field campaign of OCO-2 and GOSAT at Railroad Valley in 2016. The campaign period is June 27 to July 3 in 2016. We measured surface reflectance by using USB4000 Spectrometer with 74-UV collimating lens (Ocean Optics) and Spectralon (Labsphere). USB4000 is a UV spectrometer, and its measurement range from 300 to 520nm. We simulated CAI UV-band radiance using a vector type of radiation transfer code, i.e. including polarization calculation, pstar3 (Ota et al., 2010) using measured surface reflectance and atmospheric data, pressure and relative humidity by radiosonde in the same campaign, and aerosol optical depth by AERONET, etc. Then, we evaluated measured UV radiances with the simulated data. We show the result of vicarious calibration of CAI UV-band in the campaign, and discuss about this method for future sensor, CAI-2. Around the campaign period, there was wildfire around Los Angeles, and aerosol optical thickness (AOT) observed by AERONET at Rail Road valley and Caltech sites is also high. We tried to detect and retrieve aerosol properties using CAI data around campaign region by the multi-wavelength and multi-pixel method (MWPM) (Hashimoto AGU Fall meeting, 2014) using CAI UV-band. In the analysis, we use CAI four bands to retrieve aerosol optical properties including cloud optical characteristics. We also like to introduce the analysis result of aerosol optical properties during wildfire.

Spectral Absorption Properties of Aerosol Particles from 350-2500nm

NASA Technical Reports Server (NTRS)

Martins, J. Vanderlei; Artaxo, Paulo; Kaufman, Yoram J.; Castanho, Andrea D.; Remer, Lorraine A.

2009-01-01

The aerosol spectral absorption efficiency (alpha (sub a) in square meters per gram) is measured over an extended wavelength range (350 2500 nm) using an improved calibrated and validated reflectance technique and applied to urban aerosol samples from Sao Paulo, Brazil and from a site in Virginia, Eastern US, that experiences transported urban/industrial aerosol. The average alpha (sub a) values (approximately 3 square meters per gram at 550 nm) for Sao Paulo samples are 10 times larger than alpha (sub a) values obtained for aerosols in Virginia. Sao Paulo aerosols also show evidence of enhanced UV absorption in selected samples, probably associated with organic aerosol components. This extra UV absorption can double the absorption efficiency observed from black carbon alone, therefore reducing by up to 50% the surface UV fluxes, with important implications for climate, UV photolysis rates, and remote sensing from space.

Effect of Aerosols on Surface Radiation and Air Quality in the Central American Region Estimated Using Satellite UV Instruments

NASA Astrophysics Data System (ADS)

Bhartia, P. K.; Torres, O.; Krotkov, N. A.

2007-05-01

Solar radiation reaching the Earth's surface is reduced by both aerosol scattering and aerosol absorption. Over many parts of the world the latter effect can be as large or larger than the former effect, and small changes in the aerosol single scattering albedo can either cancel the former effect or enhance it. In addition, absorbing aerosols embedded in clouds can greatly reduce the amount of radiation reaching the surface by multiple scattering. Though the potential climatic effects of absorbing aerosols have received considerable attention lately, their effect on surface UV, photosynthesis, and photochemistry can be equally important for our environment and may affect human health and agricultural productivity. Absorption of all aerosols commonly found in the Earth's atmosphere becomes larger in the UV and blue wavelengths and has a relatively strong wavelength dependence. This is particularly true of mineral dust and organic aerosols. However, these effects have been very difficult to estimate on a global basis since the satellite instruments that operate in the visible are primarily sensitive to aerosol scattering. A notable exception is the UV Aerosol Index (AI), first produced using NASA's Nimbus-7 TOMS data. AI provides a direct measure of the effect of aerosol absorption on the backscattered UV radiation in both clear and cloudy conditions, as well as over snow/ice. Although many types of aerosols produce a distinct color cast in the visible images, and aerosols absorption over clouds and snow/ice could, in principle be detected from their color, so far this technique has worked well only in the UV. In this talk we will discuss what we have learned from the long-term record of AI produced from TOMS and Aura/OMI about the possible role of aerosols on surface radiation and air quality in the Central American region.

Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

NASA Astrophysics Data System (ADS)

Marley, N. A.; Gaffney, J. S.; Castro, T.; Salcido, A.; Frederick, J.

2008-07-01

Measurements of aerosol absorption and scattering were obtained in Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006. A comparison of aerosol absorption and scattering was obtained in Mexico City at site T0 located in the northern part of Mexico City at the Instituto Mexicano del Petróleo Laboratories and at site T1 located at the Universidad Tecnológica de Tecamac, 18 miles northwest of T0. Hourly averages of aerosol absorption were similar at both sites, ranging from 6 93 Mm-1 with an average of 31 Mm-1 at T0; and from 2 104 Mm-1 with an average of 19 Mm-1 at T1. Aerosol scattering at T0 ranged from 16 344 Mm-1 with an average of 105 Mm-1; while the scattering values at T1 were lower than T0 ranging from 2 136 with an average of 53 Mm-1. Aerosol single scattering albedos (SSAs) were determined at both sites using these data. SSAs at T1 ranged from 0.44 0.90 with an average 0.75 as compared to hose at T0, range 0.51 0.93 with an average of 0.77. Broadband UV-B intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UV-B intensities with the simultaneous UV-B measurements obtained at site T0 and at site T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosol scattering Ångstrom coefficient at T0 suggests the larger diffuse radiation is due to the predominance of submicron aerosols at T0 with aerosol scattering of UV-B radiation peaked in the forward direction, leading to the enhancement observed at ground level.

Retrieval of Aerosol Absorption Properties from Satellite Observations

NASA Technical Reports Server (NTRS)

Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo

2012-01-01

The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

Satellite-Based Evidence of Wavelength-Dependent Aerosol Absorption in Biomass Burning Smoke Inferred from Ozone Monitoring Instrument

NASA Technical Reports Server (NTRS)

Jethva, H.; Torres, O.

2012-01-01

We provide satellite-based evidence of the spectral dependence of absorption in biomass burning aerosols over South America using near-UV measurements made by the Ozone Monitoring Instrument (OMI) during 2005-2007. In the current near-UV OMI aerosol algorithm (OMAERUV), it is implicitly assumed that the only absorbing component in carbonaceous aerosols is black carbon whose imaginary component of the refractive index is wavelength independent. With this assumption, OMI-derived aerosol optical depth (AOD) is found to be significantly over-estimated compared to that of AERONET at several sites during intense biomass burning events (August-September). Other well-known sources of error affecting the near-UV method of aerosol retrieval do not explain the large observed AOD discrepancies between the satellite and the ground-based observations. A number of studies have revealed strong spectral dependence in carbonaceous aerosol absorption in the near-UV region suggesting the presence of organic carbon in biomass burning generated aerosols. A sensitivity analysis examining the importance of accounting for the presence of wavelength-dependent aerosol absorption in carbonaceous particles in satellite-based remote sensing was carried out in this work. The results convincingly show that the inclusion of spectrally-dependent aerosol absorption in the radiative transfer calculations leads to a more accurate characterization of the atmospheric load of carbonaceous aerosols.

Comparisons of spectral aerosol single scattering albedo in Seoul, South Korea

NASA Astrophysics Data System (ADS)

Mok, Jungbin; Krotkov, Nickolay A.; Torres, Omar; Jethva, Hiren; Li, Zhanqing; Kim, Jhoon; Koo, Ja-Ho; Go, Sujung; Irie, Hitoshi; Labow, Gordon; Eck, Thomas F.; Holben, Brent N.; Herman, Jay; Loughman, Robert P.; Spinei, Elena; Lee, Seoung Soo; Khatri, Pradeep; Campanelli, Monica

2018-04-01

Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols

NASA Astrophysics Data System (ADS)

Gyawali, M.; Arnott, W. P.; Zaveri, R. A.; Song, C.; Moosmüller, H.; Liu, L.; Mishchenko, M. I.; Chen, L.-W. A.; Green, M. C.; Watson, J. G.; Chow, J. C.

2011-09-01

We present the first laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet (UV) wavelength (i.e. 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA';s acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Exact T-matrix method calculations were used to model the absorption and scattering characteristics of fractal-like agglomerates of different compactness and varying number of monomers. With these calculations, we attempted to estimate the number of monomers and fractal dimension of laboratory generated kerosene soot. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009, and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.

Spectral dependence on the correction factor of erythemal UV for cloud, aerosol, total ozone, and surface properties: A modeling study

NASA Astrophysics Data System (ADS)

Park, Sang Seo; Jung, Yeonjin; Lee, Yun Gon

2016-07-01

Radiative transfer model simulations were used to investigate the erythemal ultraviolet (EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors (CFEUV) for UV-A [CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from -5.0% to 25.0% for aerosols, and from -9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions (i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%-4.1% per 0.1 albedo change, depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.

Carbon Isotopic Measurements and Aerosol Optical Determinations during CARES: Indications of the Importance of Background Biogenic Aerosols

NASA Astrophysics Data System (ADS)

Gaffney, J. S.; Marley, N. A.; Begum, M.; Sturchio, N. C.; Guilderson, T. P.

2011-12-01

High volume size-fractionated aerosol samples were obtained in Cool, CA during the Carbonaceous Aerosol and Radiative Effects Study (CARES) in June of 2010. This site was chosen to study the regional impacts of carbonaceous aerosols originating from the Sacramento area. Samples were collected for 6 to 24 hour time periods on quartz fiber filters by using slotted impactors to allow for collection of sample size cuts above and below one micron. Both total carbon content and carbon isotopic composition, including 13C/12C and 14C, were determined on the samples. In addition, Ångstrom absorption exponents (AAEs) were determined for the region of 300-900 nm on the sub-micron size cut by using state of the art diffuse reflectance UV-visible spectroscopy with integrating sphere technology. The overall carbonaceous aerosol loadings were found to be quite low and relatively constant during the study, suggesting that most of the aerosols at the site were locally formed background aerosols. The 14C data is consistent with a substantial fraction (~80 %) being from modern carbon sources and 13C/12C results indicate that the carbon source was from C-3 plants. This is consistent with a significant fraction of the aerosols in the area arising from secondary formation from biogenic precursor emissions from trees, most likely mono- and sesquiterpenes. These results are compared to past results obtained in Mexico City and discussed in terms of the potential importance of biogenic emissions to UV absorbing aerosols as these are anticipated to increase with climate change. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328 and Grant No. DE-FG02-07-ER64329 as part of the Atmospheric Systems Research program.

Comparisons of Spectral Aerosol Single Scattering Albedo in Seoul, South Korea

NASA Technical Reports Server (NTRS)

Mok, Jungbin; Krotkov, Nickolay A.; Torres, Omar; Jethva, Hiren; Loughman, Robert P.; Spinei, Elena; Campanelli, Monica; Li, Zhanqing; Go, Sujung; Labow, Gordon;

UV lidar measurements of the stratospheric aerosol layer and comparison with other optical data

NASA Technical Reports Server (NTRS)

Uchino, O.

1985-01-01

After the violent volcanic eruptions of El Chichon in Mexico (17.33 deg. N, 93.20 deg. W) in late March and early April 1982, enhanced stratospheric aerosols have been monitored by ruby (lasing wavelength lambda=694.3 nm) or Nd:YAG lidars (lambda=1064 or 532 nm). By these lidars, visible or near-infrared optical informations of stratospheric aerosols and their space-time variations can be obtained. It is usually difficult to measure the background level of stratospheric aerosols by an ultraviolet (UV) lidar, since Rayleigh scattering prevails over Mie scattering in the stratosphere. However, after the large volcanic eruptions, UV lidar measurements of stratospheric aerosols are possible. In order to obtain UV optical properties of stratospheric aerosols, measurements have been made at Fukuoka (33.65 deg. N, 130.35 deg. E) by a p-terphenyl dye laser at a wavelength of 340.5 nm. Observational results during October 1982, through May 1983, are shown and are compared with the results obtained by a ruby lidar at Tsukuba (36.05 deg. N, 140.13 deg. E).

The OMI Aerosol Absorption Product: An A-train application

NASA Astrophysics Data System (ADS)

Torres, O.; Jethva, H. T.; Ahn, C.

2017-12-01

Because of the uniquely large sensitivity of satellite-measured near-UV radiances to absorption by desert dust, carbonaceous and volcanic ash aerosols, observations by a variety of UV-capable sensors have been routinely used over the last forty years in both qualitative and quantitative applications for estimating the absorption properties of these aerosol types. In this presentation we will discuss a multi-sensor application involving observations from A-train sensors OMI, AIRS and CALIOP for the creation of a 13-year record of aerosol optical depth (AOD) and single scattering albedo (SSA). Determination of aerosol type, in terms of particle size distribution and refractive index, is an important algorithmic step that requires using external information. AIRS CO measurements are used as carbonaceous aerosols tracer to differentiate this aerosol type from desert dust. On the other hand, the height of the absorbing aerosol layer, an important parameter in UV aerosol retrievals, is prescribed using a CALIOP-based climatology. The combined use of these observations in the developments of the OMI long-term AOD/SSA record will be discussed along with an evaluation of retrieval results using independent observations.

Total ozone column, aerosol optical depth and precipitable water effects on solar erythemal ultraviolet radiation recorded in Malta.

NASA Astrophysics Data System (ADS)

Bilbao, Julia; Román, Roberto; Yousif, Charles; Mateos, David; Miguel, Argimiro

2013-04-01

The Universities of Malta and Valladolid (Spain) developed a measurement campaign, which took place in the Institute for Energy Technology in Marsaxlokk (Southern Malta) between May and October 2012, and it was supported by the Spanish government through the Project titled "Measurement campaign about Solar Radiation, Ozone, and Aerosol in the Mediterranean area" (with reference CGL2010-12140-E). This campaign provided the first ground-based measurements in Malta of erythemal radiation and UV index, which indicate the effectiveness of the sun exposure to produce sunburn on human skin. A wide variety of instruments was involved in the campaign, providing a complete atmospheric characterization. Data of erythemal radiation and UV index (from UVB-1 pyranometer), total shortwave radiaton (global and diffuse components from CM-6B pyranometers), and total ozone column, aerosol optical thickness, and precitable water column (from a Microtops-II sunphotometer) were available in the campaign. Ground-based and satellite instruments were used in the analysis, and several intercomparisons were carried out to validate remote sensing data. OMI, GOME, GOME-2, and MODIS instruments, which provide data of ozone, aerosol load and optical properties, were used to this end. The effects on solar radiation, ultraviolet and total shortwave ranges, of total ozone column, aerosol optical thickness and precipitable water column were obtained using radiation measurements at different fixed solar zenith angles. The empirical results shown a determinant role of the solar position, a negligible effect of ozone on total shortwave radiation, and a stronger attenuation provided by aerosol particles in the erythemal radiation. A variety of aerosol types from different sources (desert dust, biomass burning, continental, and maritime) reach Malta, in this campaign several dust events from the Sahara desert occurred and were analyzed establishing the air mass back-trajectories ending at Malta at several heights calculated by means of the HYSPLIT model. Hence, changes in the UV index due to atmospheric aerosol were characterized.

Modelled and measured effects of clouds on UV Aerosol Indices on a local, regional, and global scale

NASA Astrophysics Data System (ADS)

Penning de Vries, M.; Wagner, T.

2010-10-01

The UV Aerosol Indices (UVAI) form one of very few available tools in satellite remote sensing that provide information on aerosol absorption. The UVAI are also quite insensitive to surface type and are determined in the presence of clouds - situations where most aerosol retrieval algorithms do not work. The UVAI are most sensitive to elevated layers of absorbing aerosols, such as mineral dust and smoke from biomass burning, but they can also be used to study non-absorbing aerosols, such as sulphate and secondary organic aerosols. Although UVAI are determined for cloud-contaminated pixels, clouds do affect the value of UVAI in several ways. One way to correct for these effects is to remove clouded pixels using a cloud filter. However, this causes a large loss of data, biases the results towards clear skies, and removes all potentially very interesting pixels where aerosols and clouds co-exist. We here propose to correct the effects of clouds on UVAI in a more sophisticated way, namely by simulating the contribution of clouds to UVAI, and then subtracting it from the measured data. To this aim, we modelled UVAI from clouds by using measured cloud optical parameters - either with low spatial resolution from SCIAMACHY, or high resolution from MERIS - as input. The modelled UVAI were compared with UVAI measured by SCIAMACHY on different spatial (local, regional and global) and temporal scales (single measurement, daily means and seasonal means). The general dependencies of UVAI on cloud parameters were quite well reproduced, but several issues remain unclear: compared to the modelled UVAI, measured UVAI show a bias, in particular for large cloud fractions, and much larger scatter. Also, the viewing angle dependence differs for measured and modelled UVAI. The modelled UVAI from clouds will be used to correct measured UVAI for the effect of clouds, thus allowing a more quantitative analysis of UVAI and enabling investigations of aerosol-cloud interactions.

UV Lidar Receiver Analysis for Tropospheric Sensing of Ozone

NASA Technical Reports Server (NTRS)

Pliutau, Denis; DeYoung, Russell J.

2013-01-01

A simulation of a ground based Ultra-Violet Differential Absorption Lidar (UV-DIAL) receiver system was performed under realistic daytime conditions to understand how range and lidar performance can be improved for a given UV pulse laser energy. Calculations were also performed for an aerosol channel transmitting at 3 W. The lidar receiver simulation studies were optimized for the purpose of tropospheric ozone measurements. The transmitted lidar UV measurements were from 285 to 295 nm and the aerosol channel was 527-nm. The calculations are based on atmospheric transmission given by the HITRAN database and the Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological data. The aerosol attenuation is estimated using both the BACKSCAT 4.0 code as well as data collected during the CALIPSO mission. The lidar performance is estimated for both diffuseirradiance free cases corresponding to nighttime operation as well as the daytime diffuse scattered radiation component based on previously reported experimental data. This analysis presets calculations of the UV-DIAL receiver ozone and aerosol measurement range as a function of sky irradiance, filter bandwidth and laser transmitted UV and 527-nm energy

Ultraviolet Satellite Measurements of Volcanic Ash. Chapter 12

NASA Technical Reports Server (NTRS)

Carn, S. A.; Krotkov, N. A.

2016-01-01

Ultraviolet (UV) remote sensing of volcanic ash and other absorbing aerosols from space began with the launch of the first Total Ozone Mapping Spectrometer (TOMS) instrument in 1978. Subsequent UV satellite missions (TOMS, GOME, SCIAMACHY, OMI, GOME-2, OMPS) have extended UV ash measurements to the present, generating a unique multidecadal record. A UV Aerosol Index (UVAI) based on two near-UV wavelengths, equally applicable to multispectral (TOMS, DSCOVR) or hyperspectral (GOME, SCIAMACHY, OMI, GOME-2, OMPS) instruments, has been used to derive a unique absorbing aerosol climatology across multiple UV satellite missions. Advantages of UV ash measurements relative to infrared (IR) techniques include the ability to detect ash at any altitude (assuming no clouds), above clouds, and over bright surfaces, where visible and IR techniques may fail. Disadvantages include the daytime-only restriction and nonspecificity to silicate ash, since UV measurements are sensitive to any UV-absorbing aerosol, including smoke, desert dust, and pollution. However, simultaneous retrieval of sulfur dioxide (SO2) abundance and UVAI provides robust discrimination of volcanic clouds. Although the UVAI is only semiquantitative, it has proved successful at detecting and tracking volcanic ash clouds from many volcanic eruptions since 1978. NASA A-Train measurements since 2006 (eg, CALIOP) have provided much improved constraints on volcanic ash altitude, and also permit identification of aerosol type through sensor synergy. Quantitative UV retrievals of ash optical depth, effective particle size, and ash column mass are possible and require assumptions of ash refractive index, particle size distribution, and ash layer altitude. The lack of extensive ash refractive index data in the UV-visible and the effects of ash particle shape on retrievals introduce significant uncertainty in the retrieved parameters, although limited validation against IR ash retrievals has been successful. In this contribution, we review UV ash detection and retrieval techniques and provide examples of volcanic eruptions detected in the approx. 37 year data record.

Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.

NASA Astrophysics Data System (ADS)

Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

2007-12-01

Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the aerosol Angstrom absorption exponents by linear regression over the entire UV-visible spectral range. These results are compared to results obtained from the absorbance measurements obtained in the field. The differences in calculated Angstrom absorption exponents between the field and laboratory measurements are attributed partly to the differences in time resolution of the sample collection resulting in heavier particle pileup on the filter surface of the 12-hour samples. Some differences in calculated results can also be attributed to the presence of narrow band absorbers below 400 nm that do not fall in the wavelengths covered by the 7 wavelengths of the aethalometer. 1. Marley, N.A., J.S. Gaffney, J.C. Baird, C.A. Blazer, P.J. Drayton, and J.E. Frederick, "The determination of scattering and absorption coefficients of size-fractionated aerosols for radiative transfer calculations." Aerosol Sci. Technol., 34, 535-549, (2001). This work was conducted as part of the Department of Energy's Atmospheric Science Program as part of the Megacity Aerosol Experiment - Mexico City during MILAGRO. This research was supported by the Office of Science (BER), U.S. Department of Energy Grant No. DE-FG02-07ER64329. We also wish to thank Mexican Scientists and students for their assistance from the Instituto Mexicano de Petroleo (IMP) and CENICA.

Retrieval of the aerosol optical thickness from UV global irradiance measurements

NASA Astrophysics Data System (ADS)

Costa, M. J.; Salgueiro, V.; Bortoli, D.; Obregón, M. A.; Antón, M.; Silva, A. M.

2015-12-01

The UV irradiance is measured at Évora since several years, where a CIMEL sunphotometer integrated in AERONET is also installed. In the present work, measurements of UVA (315 - 400 nm) irradiances taken with Kipp&Zonen radiometers, as well as satellite data of ozone total column values, are used in combination with radiative transfer calculations, to estimate the aerosol optical thickness (AOT) in the UV. The retrieved UV AOT in Évora is compared with AERONET AOT (at 340 and 380 nm) and a fairly good agreement is found with a root mean square error of 0.05 (normalized root mean square error of 8.3%) and a mean absolute error of 0.04 (mean percentage error of 2.9%). The methodology is then used to estimate the UV AOT in Sines, an industrialized site on the Atlantic western coast, where the UV irradiance is monitored since 2013 but no aerosol information is available.

Variations of aerosol size distribution, chemical composition and optical properties from roadside to ambient environment: A case study in Hong Kong, China

NASA Astrophysics Data System (ADS)

Zhang, Qian; Ning, Zhi; Shen, Zhenxing; Li, Guoliang; Zhang, Junke; Lei, Yali; Xu, Hongmei; Sun, Jian; Zhang, Leiming; Westerdahl, Dane; Gali, Nirmal Kumar; Gong, Xuesong

2017-10-01

This study investigated the ;roadside-to-ambient; evolution of particle physicochemical and optical properties in typical urban atmospheres of Hong Kong through collection of chemically-resolved PM2.5 data and PM2.5 size distribution at a roadside and an ambient site. Roadside particle size distribution showed typical peaks in the nuclei mode (30-40 nm) while ambient measurements peaked in the Aitken mode (50-70 nm), revealing possible condensation and coagulation growth of freshly emitted particles during aging processes. Much higher levels of anthropogenic chemical components, i.e. nitrate, sulfate, ammonium, organic carbon (OC) and elemental carbon (EC), but lower levels of OC/EC and secondary inorganic aerosols (SIA)/EC ratios appeared in roadside than ambient particles. The high OC/EC and SIA/EC ratios in ambient particles implied high contributions from secondary aerosols. Black carbon (BC), a strong light absorbing material, showed large variations in optical properties when mixed with other inorganic and organic components. Particle-bound polycyclic aromatic hydrocarbons (p-PAHs), an indicator of brown carbon (BrC), showed significant UV-absorbing ability. The average BC and p-PAHs concentrations were 3.8 and 87.6 ng m-3, respectively, at the roadside, but were only 1.5 and 18.1 ng m-3 at the ambient site, suggesting BC and p-PAHs concentrations heavily driven by traffic emissions. In contrast, PM2.5 UV light absorption coefficients (babs-BrC,370nm) at the ambient site (4.2 Mm-1) and at the roadside site (4.1 Mm-1) were similar, emphasizing that particle aging processes enhanced UV light-absorbing properties, a conclusion that was also supported by the finding that the Absorption Ångström coefficient (AAC) value at UV wavelengths (AAC_UV band) at the ambient site were ∼1.7 times higher than that at the roadside. Both aqueous reaction and photochemically produced secondary organic aerosol (SOA) for ambient aerosols contributed to the peak values of babs-BrC,370nm in ambient particles at midnight and around noon, highlighting that secondary BrC had different sources and particle aging in the atmosphere affected BrC and BC properties and related aerosol light absorption.

Assessment of OMI Near-UV Aerosol Optical Depth over Land

NASA Technical Reports Server (NTRS)

Ahn, Changwoo; Torres, Omar; Jethva, Hiren

2014-01-01

This is the first comprehensive assessment of the aerosol optical depth (AOD) product retrieved from the near-UV observations by the Ozone Monitoring Instrument (OMI) onboard the Aura satellite. The OMI-retrieved AOD by the ultraviolet (UV) aerosol algorithm (OMAERUV version 1.4.2) was evaluated using collocated Aerosol Robotic Network (AERONET) level 2.0 direct Sun AOD measurements over 8 years (2005-2012). A time series analysis of collocated satellite and ground-based AOD observations over 8 years shows no discernible drift in OMI's calibration. A rigorous validation analysis over 4 years (2005-2008) was carried out at 44 globally distributed AERONET land sites. The chosen locations are representative of major aerosol types such as smoke from biomass burning or wildfires, desert mineral dust, and urban/industrial pollutants. Correlation coefficient (p) values of 0.75 or better were obtained at 50 percent of the sites with about 33 percent of the sites in the analysis reporting regression line slope values larger than 0.70 but always less than unity. The combined AERONET-OMAERUV analysis of the 44 sites yielded a p of 0.81, slope of 0.79, Y intercept of 0.10, and 65 percent OMAERUV AOD falling within the expected uncertainty range (largest of 30 percent or 0.1) at 440 nanometers. The most accurate OMAERUV retrievals are reported over northern Africa locations where the predominant aerosol type is desert dust and cloud presence is less frequent. Reliable retrievals were documented at many sites characterized by urban-type aerosols with low to moderate AOD values, concentrated in the boundary layer. These results confirm that the near-ultraviolet observations are sensitive to the entire aerosol column. A simultaneous comparison of OMAERUV, Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue, and Multiangle Imaging Spectroradiometer (MISR) AOD retrievals to AERONET measurements was also carried out to evaluate the OMAERUV accuracy in relation to those of the standard aerosol satellite products. The outcome of the comparison indicates that OMAERUV, MODIS Deep Blue, and MISR retrieval accuracies in arid and semiarid environments are statistically comparable.

Using the OMI Aerosol Index and Absorption Aerosol Optical Depth to evaluate the NASA MERRA Aerosol Reanalysis

NASA Astrophysics Data System (ADS)

Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

2014-12-01

A radiative transfer interface has been developed to simulate the UV Aerosol Index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and Aerosol Absorption Optical Depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the Aerosol Robotic Network (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the South African and South American biomass burning regions indicates that revising the spectrally-dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons. Finally, during a period where the Asian region was mainly dominated by anthropogenic aerosols, we have performed a qualitative analysis in which the specification of anthropogenic emissions in GEOS-5 is adjusted to provide insight into discrepancies observed in AI comparisons.

Using the OMI aerosol index and absorption aerosol optical depth to evaluate the NASA MERRA Aerosol Reanalysis

NASA Astrophysics Data System (ADS)

Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

2015-05-01

A radiative transfer interface has been developed to simulate the UV aerosol index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and aerosol absorption optical depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the AErosol RObotic NETwork (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model-produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the southern African and South American biomass burning regions indicates that revising the spectrally dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons. Finally, during a period where the Asian region was mainly dominated by anthropogenic aerosols, we have performed a qualitative analysis in which the specification of anthropogenic emissions in GEOS-5 is adjusted to provide insight into discrepancies observed in AI comparisons.

Estimation of UV index in the clear-sky using OMI PROFOZ and AERONET data

NASA Astrophysics Data System (ADS)

Lee, H.; Kim, J.; Jeong, U.

2016-12-01

Due to a strong influence to the human health and ecosystem environment, continuous monitoring of the surface-level ultraviolet (UV) radiation is important nowadays. UV index (UVI) is a simple parameter to show the strength of surface UV radiation, therefore UVI has been widely utilized for the purpose of UV monitoring. In this work, we also try to develop our own retrieval algorithm for better estimation of UVI. The amount of UVA (320-400 nm) and UVB (290-320 nm) radiation at the Earth surface depends on the extent of Rayleigh scattering by atmospheric gas molecules, the radiative absorption by ozone, radiative scattering by clouds, and both absorption and scattering by airborne aerosols. Thus advanced consideration of these factors is the essential part to establish the process of UVI estimation. In this study, we estimate UV Index (UVI) at Seoul first in a clear-sky atmosphere, and then validate this estimated UVI comparing to UVI from Brewer spectrophotometer measurements located at Yonsei University in Seoul. We use the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model version 2.6 for our UVI calculation. To consider the ozone and aerosol influence in a real situation, we input ozone and temperature profiles from the Ozone Monitoring Instrument (OMI) Aura vertical profile ozone (PROFOZ) data, and aerosol properties from the AErosol RObotic NETwork (AERONET) measurements at Seoul into the model. Inter-comparison of UVI is performed for the year 2011, 2012 and 2014, and resulted in a high correlation coefficient (R=0.95) under clear-sky condition. But a slight overestimation of Brewer UVI occurred under high AOD conditions in clear-sky. Because our UVI algorithm does not account for surface absorbing aerosols, it is lead to systematic overestimation of surface UV irradiances. Therefore, we also investigate the effect of absorbing aerosol on the amount of UV irradiance in the clear-sky over East Asia.

Direct Retrieval of Sulfur Dioxide Amount and Altitude from Spaceborne Hyperspectral UV Measurements: Theory and Application

NASA Technical Reports Server (NTRS)

Yang, Kau; Liu, Xiong; Bhartia, Pawan K.; Krotkov, Nickolay A.; Carn, Simon A.; Hughes, Eric J.; Krueger, Arlin J.; Spurr, Robert D.; Trahan, Samuel G.

2010-01-01

We describe the physical processes by which a vertically localized absorber perturbs the top-of-atmosphere solar backscattered ultraviolet (UV) radiance. The distinct spectral responses to perturbations of an absorber in its column amount and layer altitude provide the basis for a practical satellite retrieval technique, the Extended Iterative Spectral Fitting (EISF) algorithm, for the simultaneous retrieval of these quantities of a SO2 plume. In addition, the EISF retrieval provides an improved UV aerosol index for quantifying the spectral contrast of apparent scene reflectance at the bottom of atmosphere bounded by the surface and/or cloud; hence it can be used for detection of the presence or absence of UV absorbing aerosols. We study the performance and characterize the uncertainties of the EISF algorithm using synthetic backscattered UV radiances, retrievals from which can be compared with those used in the simulation. Our findings indicate that the presence of aerosols (both absorbing and nonabsorbing) does not cause large errors in EISF retrievals under most observing conditions when they are located below the SO2 plume. The EISF retrievals assuming a homogeneous field of view can provide accurate column amounts for inhomogeneous scenes, but they always underestimate the plume altitudes. The EISF algorithm reduces systematic errors present in existing linear retrieval algorithms that use prescribed SO2 plume heights. Applying the EISF algorithm to Ozone Monitoring Instrument satellite observations of the recent Kasatochi volcanic eruption, we demonstrate the successful retrieval of effective plume altitude of volcanic SO2, and we also show the improvement in accuracy in the corresponding SO2 columns.

Validation of TOMS Aerosol Products using AERONET Observations

NASA Technical Reports Server (NTRS)

Bhartia, P. K.; Torres, O.; Sinyuk, A.; Holben, B.

2002-01-01

The Total Ozone Mapping Spectrometer (TOMS) aerosol algorithm uses measurements of radiances at two near UV channels in the range 331-380 nm to derive aerosol optical depth and single scattering albedo. Because of the low near UV surface albedo of all terrestrial surfaces (between 0.02 and 0.08), the TOMS algorithm has the capability of retrieving aerosol properties over the oceans and the continents. The Aerosol Robotic Network (AERONET) routinely derives spectral aerosol optical depth and single scattering albedo at a large number of sites around the globe. We have performed comparisons of both aerosol optical depth and single scattering albedo derived from TOMS and AERONET. In general, the TOMS aerosol products agree well with the ground-based observations, Results of this validation will be discussed.

Anthropogenic changes in the surface all-sky UV-B radiation through 1850-2005 simulated by an Earth system model

NASA Astrophysics Data System (ADS)

Watanabe, S.; Takemura, T.; Sudo, K.; Yokohata, T.; Kawase, H.

2012-06-01

The historical anthropogenic change in the surface all-sky UV-B (solar ultraviolet: 280-315 nm) radiation through 1850-2005 is evaluated using an Earth system model. Responses of UV-B dose to anthropogenic changes in ozone and aerosols are separately evaluated using a series of historical simulations including/excluding these changes. Increases in these air pollutants cause reductions in UV-B transmittance, which occur gradually/rapidly before/after 1950 in and downwind of industrial and deforestation regions. Furthermore, changes in ozone transport in the lower stratosphere, which is induced by increasing greenhouse gas concentrations, increase ozone concentration in the extratropical upper troposphere and lower stratosphere. These transient changes work to decrease the amount of UV-B reaching the Earth's surface, counteracting the well-known effect increasing UV-B due to stratospheric ozone depletion, which developed rapidly after ca. 1980. As a consequence, the surface UV-B radiation change between 1850 and 2000 is negative in the tropics and NH extratropics and positive in the SH extratropics. Comparing the contributions of ozone and aerosol changes to the UV-B change, the transient change in ozone absorption of UV-B mainly determines the total change in the surface UV-B radiation at most locations. On the other hand, the aerosol direct and indirect effects on UV-B play an equally important role to that of ozone in the NH mid-latitudes and tropics. A typical example is East Asia (25° N-60° N and 120° E-150° E), where the effect of aerosols (ca. 70%) dominates the total UV-B change.

Anthropogenic changes in the surface all-sky UV-B radiation through 1850-2005 simulated by an Earth system model

NASA Astrophysics Data System (ADS)

Watanabe, S.; Takemura, T.; Sudo, K.; Yokohata, T.; Kawase, H.

2012-02-01

The historical anthropogenic change in the surface all-sky UV-B (solar ultraviolet: 280-315 nm) radiation through 1850-2005 is evaluated using an Earth system model. Responses of UV-B dose to anthropogenic changes in ozone and aerosols are separately evaluated using a series of historical simulations including/excluding these changes. Increases in these air pollutants cause reductions in UV-B transmittance, which occur gradually/rapidly before/after 1950 in and downwind of industrial and deforestation regions. Furthermore, changes in ozone transport in the lower stratosphere, which is induced by increasing greenhouse gas concentrations, increase ozone concentration in the extratropical upper troposphere and lower stratosphere. These transient changes work to decrease the amount of UV-B reaching the Earth's surface, counteracting the well-known effect increasing UV-B due to stratospheric ozone depletion, which developed rapidly after ca. 1980. As a consequence, the surface all-sky UV-B radiation change between 1850 and 2000 is negative in the tropics and NH extratropics and positive in the SH extratropics. Comparing the contributions of ozone and aerosol changes to the UV-B change, the transient change in ozone absorption of UV-B mainly determines the total change in the surface all-sky UV-B radiation at most locations. On the other hand, the aerosol direct and indirect effects on UV-B play an equally important role to that of ozone in the NH mid-latitudes and tropics. A typical example is East Asia (25° N-60° N and 120° E-150° E), where the effect of aerosols (ca. 70%) dominates the total UV-B change.

Impact of Tropospheric Aerosol Absorption on Ozone Retrieval from buv Measurements

NASA Technical Reports Server (NTRS)

Torres, O.; Bhartia, P. K.

1998-01-01

The impact of tropospheric aerosols on the retrieval of column ozone amounts using spaceborne measurements of backscattered ultraviolet radiation is examined. Using radiative transfer calculations, we show that uv-absorbing desert dust may introduce errors as large as 10% in ozone column amount, depending on the aerosol layer height and optical depth. Smaller errors are produced by carbonaceous aerosols that result from biomass burning. Though the error is produced by complex interactions between ozone absorption (both stratospheric and tropospheric), aerosol scattering, and aerosol absorption, a surprisingly simple correction procedure reduces the error to about 1%, for a variety of aerosols and for a wide range of aerosol loading. Comparison of the corrected TOMS data with operational data indicates that though the zonal mean total ozone derived from TOMS are not significantly affected by these errors, localized affects in the tropics can be large enough to seriously affect the studies of tropospheric ozone that are currently undergoing using the TOMS data.

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyawali, Madhu S.; Arnott, W. Patrick; Zaveri, Rahul A.

2012-03-08

We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 Januarymore » 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM{sub 2.5} and PM{sub 10} (particulate matter with aerodynamic diameters less than 2.5 {mu}m and 10 {mu}m, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO{sub 2}). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Angstrom exponent of absorption (AEA), and Angstrom exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.« less

Photoacoustic Optical Properties at UV, VIS, and near IR Wavelengths for Laboratory Generated and Winter Time Ambient Urban Aerosols

NASA Technical Reports Server (NTRS)

Gyawali, M.; Arnott, W. P.; Zaveri, R. A.; Song, C.; Moosmuller, H.; Liu, L.; Mishchenko, M. I.; Chen, L.-W.A.; Green, M. C.; Watson, J. G.;

Airborne rhinovirus detection and effect of ultraviolet irradiation on detection by a semi-nested RT-PCR assay

PubMed Central

Myatt, Theodore A; Johnston, Sebastian L; Rudnick, Stephen; Milton, Donald K

2003-01-01

Background Rhinovirus, the most common cause of upper respiratory tract infections, has been implicated in asthma exacerbations and possibly asthma deaths. Although the method of transmission of rhinoviruses is disputed, several studies have demonstrated that aerosol transmission is a likely method of transmission among adults. As a first step in studies of possible airborne rhinovirus transmission, we developed methods to detect aerosolized rhinovirus by extending existing technology for detecting infectious agents in nasal specimens. Methods We aerosolized rhinovirus in a small aerosol chamber. Experiments were conducted with decreasing concentrations of rhinovirus. To determine the effect of UV irradiation on detection of rhinoviral aerosols, we also conducted experiments in which we exposed aerosols to a UV dose of 684 mJ/m2. Aerosols were collected on Teflon filters and rhinovirus recovered in Qiagen AVL buffer using the Qiagen QIAamp Viral RNA Kit (Qiagen Corp., Valencia, California) followed by semi-nested RT-PCR and detection by gel electrophoresis. Results We obtained positive results from filter samples that had collected at least 1.3 TCID50 of aerosolized rhinovirus. Ultraviolet irradiation of airborne virus at doses much greater than those used in upper-room UV germicidal irradiation applications did not inhibit subsequent detection with the RT-PCR assay. Conclusion The air sampling and extraction methodology developed in this study should be applicable to the detection of rhinovirus and other airborne viruses in the indoor air of offices and schools. This method, however, cannot distinguish UV inactivated virus from infectious viral particles. PMID:12525263

ATTENUATION OF SOLAR UV RADIATION BY AEROSOLS DURING AIR POLLUTION EPISODES

EPA Science Inventory

Increase in the amount of solar UV radiation reaching the surface due to decrease in stratospheric ozone continues to be a major concern (WMO, 1998). However, recent studies show that absorption and smattering by aerosols during air pollution episode decreases the amount of radi...

Near UV Aerosol Group Report

NASA Technical Reports Server (NTRS)

Torres, Omar

2013-01-01

2012-13 Report of research on aerosol and cloud remote sensing using UV observations. The document was presented at the 2013 AEROCENTER Annual Meeting held at the GSFC Visitors Center, May 31, 2013. The Organizers of the meeting are posting the talks to the public Aerocentr website, after the meeting.

A Global, Decadal, Quantitative Record of Absorbing Aerosols above Cloud Using OMI's Near-UV Observations

NASA Astrophysics Data System (ADS)

Torres, O.; Jethva, H. T.; Ahn, C.

2016-12-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes of the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over dark surface, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing (warming) at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud directly depends on the aerosol loading, microphysical and optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. Physically based on the strong `color ratio' effect in the near-UV caused by the spectral absorption of aerosols above cloud, the algorithm, formally named as OMACA, retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. Here, we present the algorithm architecture and results from an 11-year global record (2005-2015) including global climatology of frequency of occurrence and ACAOD. The theoretical uncertainty analysis and planned validation activities using measurements from upcoming field campaigns are also discussed.

A Ten-Year Global Record of Absorbing Aerosols Above Clouds from OMI's Near-UV Observations

NASA Technical Reports Server (NTRS)

Jethva, Hiren; Torres, Omar; Ahn, Changwoo

2016-01-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes associated with the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regional of the world. Contrary to the cloud-free scenario over dark surface, for which aerosols are known to produce a net cooling effect (negative radiative forcing) on climate, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud depends directly on the aerosol loading, microphysical-optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of optical depth of absorbing aerosols above clouds retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. The presence of absorbing aerosols above cloud reduces the upwelling radiation reflected by cloud and produces a strong 'color ratio' effect in the near-UV region, which can be unambiguously detected in the OMI measurements. Physically based on this effect, the OMACA algorithm retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. The algorithm architecture and results from a ten-year global record including global climatology of frequency of occurrence and above-cloud aerosol optical depth, and a discussion on related future field campaigns are presented.

Broadband optical extinction measurements and complex refractive indices in the ultraviolet spectral region for biogenic secondary organic aerosol exposed to ammonia

NASA Astrophysics Data System (ADS)

Flores, J.; Washenfelder, R. A.; Lee, H.; Segev, L.; Nizkorodov, S.; Brown, S. S.; Rudich, Y.

2013-12-01

The interaction between aerosols and sunlight plays an important role in the radiative balance of Earth's atmosphere. Aerosols can both scatter and absorb solar radiation causing surface cooling and heating of the atmosphere. These interactions depend on the optical properties of the aerosols (i.e., complex refractive index). Secondary organic aerosol (SOA) account for a significant fraction of the tropospheric aerosol. However, their chemical, physical, and optical properties, especially as they are processed in the atmosphere (aging), are still poorly understood. In this study, SOA formed by the ozonolysis of various biogenic volatile organic compound (BVOC) precursors (α-pinene, limonene, and α-humulene) were exposed to humid air containing various concentrations of gaseous ammonia which has been shown to cause the biogenic SOA to ';brown' on filters. The extent of absorption of the SOA in the aerosol phase cause by the exposure to gaseous ammonia was measured by a newly developed instrument to measure aerosol extinction as a function of wavelength using Broadband Cavity Enhanced Spectroscopy (BBCES) with a broadband light source. Size-selected measurements of the humid SOA exposed to NH3 for about 1.5 hours were used to derive complex refractive indices (RI) as a function of wavelength in the UV spectral region (from 360 - 420nm). The imaginary part of the refractive index did not exceed 0.05 in the 360 - 420 nm range for SOA formed from the three BVOCs even at high concentrations of NH3 (>1ppm), allowing to place an upper limit of k = 0.05. Furthermore, the small k values are consistent with bulk UV-VIS measurements. However, for the α-pinene SOA, the real part of the RI slightly increased from n = 1.49 to n = 1.55 with negligible spectral dependence. For limonene and α-humulene the real part remind constant within error calculations. Based on these observations, reactive uptake of gaseous ammonia is not expected to significantly affect absorption and scattering properties of SOA particles.

Development and Testing of the New Surface LER Climatology for OMI UV Aerosol Retrievals

NASA Technical Reports Server (NTRS)

Gupta, Pawan; Torres, Omar; Jethva, Hiren; Ahn, Changwoo

2014-01-01

Ozone Monitoring Instrument (OMI) onboard Aura satellite retrieved aerosols properties using UV part of solar spectrum. The OMI near UV aerosol algorithm (OMAERUV) is a global inversion scheme which retrieves aerosol properties both over ocean and land. The current version of the algorithm makes use of TOMS derived Lambertian Equivalent Reflectance (LER) climatology. A new monthly climatology of surface LER at 354 and 388 nm have been developed. This will replace TOMS LER (380 nm and 354nm) climatology in OMI near UV aerosol retrieval algorithm. The main objectives of this study is to produce high resolution (quarter degree) surface LER sets as compared to existing one degree TOMS surface LERs, to product instrument and wavelength consistent surface climatology. Nine years of OMI observations have been used to derive monthly climatology of surface LER. MODIS derived aerosol optical depth (AOD) have been used to make aerosol corrections on OMI wavelengths. MODIS derived BRDF adjusted reflectance product has been also used to capture seasonal changes in the surface characteristics. Finally spatial and temporal averaging techniques have been used to fill the gaps around the globes, especially in the regions with consistent cloud cover such as Amazon. After implementation of new surface data in the research version of algorithm, comparisons of AOD and single scattering albedo (SSA) have been performed over global AERONET sites for year 2007. Preliminary results shows improvements in AOD retrievals globally but more significance improvement were observed over desert and bright locations. We will present methodology of deriving surface data sets and will discuss the observed changes in retrieved aerosol properties with respect to reference AERONET measurements.

Influence of Desert Dust Intrusions on Ground-based and Satellite Derived Ultraviolet Irradiance in Southeastern Spain

NASA Technical Reports Server (NTRS)

Krotkov, Nickolay A.; Anton, Manuel; Valenzuela, Antonio; Roman, Roberto; Lyamani, Hassan; Arola, Antti; Olmo, Francisco J.; Alados-Arboledas

2012-01-01

The desert dust aerosols strongly affect propagation of solar radiation through the atmosphere, reducing surface irradiance available for photochemistry and photosynthesis. This paper evaluates effects of desert dust on surface UV erythemal irradiance (UVER), as measured by a ground-based broadband UV radiometer and retrieved from the satellite Ozone Monitoring Instrument (OMI) at Granada (southern Spain) from January 2006 to December 2010. The dust effects are characterized by the transmittance ra tio of the measured UVER to the corresponding modeled clear sky value. The transmittance has an exponential dependency on aerosol optical depth (AOD), with minimum values of approximately 0.6 (attenuation of approximately 40%). The OMI UVER algorithm does not account for UV aerosol absorption, which results in overestimation of the ground-based UVER especially during dust episodes with a mean relative difference up to 40%. The application of aerosol absorption post-correction method reduces OMI bias up to approximately 13%. The results highlight great effect of desert dust on the surface UV irradiance in regions like southern Spain, where dust intrusions from Sahara region are very frequent.

Synthesis of Poly(N-isopropylacrylamide) Microcapsules for Drug Delivery Applications via UV Aerosol Photopolymerization

NASA Astrophysics Data System (ADS)

Roberson, Nicole; Denmark, Daniel; Witanachchi, Sarath

Hybrid drug delivery systems composed of thermoresponsive polymers and magnetic nanoparticles have been developed using chemical methods to deliver controlled amounts of a biotherapeutic to target tissue. These methods can be expensive, time intensive, and produce impure composites due to the use of surfactants during polymer synthesis. In this study, UV aerosol photopolymerization is used to synthesize N-isoplopylacrylamide (NIPAM) monomers, N,N-methylenebisacrylamide (MBA) crosslinker, and irgacure 2959 photoinitiator into the transporting microcapsule for drug delivery. The method of UV aerosol photopolymerization allows for the continuous, cost effective, and time efficient synthesis of a high concentration of pure polymers in a short amount of time; toxic surfactants are not necessary. Optimal NIPAM monomer, MBA crosslinker, and irgacure 2959 photoinitiator concentrations were tested and analyzed to synthesize a microcapsule with optimal conditions for controlled drug delivery. Scanning Electron Microscope (SEM) imaging reveals that synthesis of polymer microcapsules of about 30 micrometers in size is effective through UV aerosol photopolymerization. Findings will contribute greatly to the field of emergency medicine. This work was supported by the United States Army (Grant No. W81XWH1020101/3349).

Synergy Between Occultation, Limb and Nadir Satellite Data to Study Atmospheric Ozone, Aerosols and Radiation

NASA Astrophysics Data System (ADS)

Bhartia, P. K.; Loughman, R. P.; Ziemke, J. R.

2017-12-01

There is a widespread concern in the atmospheric chemistry community about the continuity of long-term datasets of ozone and related species needed to understand changes in Earth's atmospheric composition, particularly in the climate-sensitive upper tropospheric/lower stratospheric (UTLS) region. The MLS instrument on NASA 's Aura satellite designed to make such measurements is now more than 13 years old. The Canadian ACE-FTS solar occultation instrument is even older, and ESA's MIPAS instrument ceased operation in 2012. There are currently no plans to replace these instruments. Yet, at the same time for some of the atmospheric composition products we are arguably entering a golden era in space-based measurements. New generation of nadir-viewing instruments operating in IR, VIS and UV wavelengths are already flying and soon there will be 3 UV/VIS instruments in geostationary orbits. The limb-viewing component of the OMPS instrument launched on the Suomi NPP satellite in 2011 is capable of measuring ozone and aerosols at 2 km vertical resolution down to about 12 km. NASA is building another copy of this instrument for launch on JPSS-2 in 2022 and there are plans to build more. The SAGE III instrument installed on the International Space Station earlier this year has restarted the venerable time series of ozone and aerosols that ended in 2005 with the demise of SAGE II. However, we argue that to make best use of these assets it is desirable to take advantage of the synergies between these instruments. Several multi-instrument tropospheric ozone products are already available. We expect continued efforts to improve these products by doing joint retrieval of limb, IR and UV nadir data. Another promising area is to combine solar occultation and limb-scattered data to produce aerosol extinction profiles at high spatial resolution, and to constrain aerosol size distribution parameters and refractive indices- an approach similar to the almucantar technique pioneered by the ground-based AERONET network. Finally, we discuss how limb and nadir back-scattered radiances could be synergistically combined to estimate spectrally-resolved hemispherical albedo of the planet from the UV to near-IR for climate studies.

Aerosol Absorption Retrievals from the PACE Broad Spectrum Ocean Color Instrument (OCI)

NASA Technical Reports Server (NTRS)

Mattoo, Shana; Remer, Lorraine A.; Levy, Robert C.; Gupta, Pawan; Ahmad, Ziauddin; Martins, J. Vanderlei; Lima, Adriana Rocha; Torres, Omar

2016-01-01

The PACE (Pre-­Aerosol, Clouds and ocean Ecosystem) mission, anticipated for launch in the early 2020s, is designed to characterize oceanic and atmospheric properties. The primary instrument on-­-board will be a moderate resolution (approximately 1 km nadir) radiometer, called the Ocean Color Instrument (OCI). OCI will provide high spectral resolution (5 nm) from the UV to NIR (350 - 800 nm), with additional spectral bands in the NIR and SWIR. The OCI itself is an excellent instrument for atmospheric objectives, providing measurements across a broad spectral range that in essence combines the capabilities of MODIS and OMI, but with the UV channels from OMI to be available at moderate resolution. (Image credit: PACE Science Definition Team Report). Objective: Can we make use of the UV-­SWIR measurements to derive information about aerosol absorption when aerosol loading is high?

A long term study of the relations between erythemal UV-B irradiance, total ozone column, and aerosol optical depth at central Argentina

NASA Astrophysics Data System (ADS)

Palancar, Gustavo G.; Olcese, Luis E.; Achad, Mariana; López, María Laura; Toselli, Beatriz M.

2017-09-01

Global ultraviolet-B irradiance (UV-B, 280-315 nm) measurements made at the campus of the University of Córdoba, Argentina were analyzed to quantify the effects of ozone and aerosols on surface UV-B erythemal irradiance (UVER). The measurements have been carried out with a YES Pyranometer during the period 2000-2013. The effect of ozone and aerosols has been quantified by means of the Radiation Amplification Factor (RAF) and by an aerosol factor (AF, analogous to RAF), respectively. The overall mean RAF under cloudless conditions was (1.2 ± 0.3) %, ranging from 0.67 to 2.10% depending on solar zenith angle (SZA) and on Aerosol Optical Depth (AOD). The RAF increased with the SZA with a clear trend. Similarly, the aerosol effect under almost-constant ozone and SZA showed that, on average, a 1% increase in AOD forced a decrease of (0.15 ± 0.04) % in the UVER, with a range of 0.06 to 0.27 and no defined trend as a function of the SZA. To analyze the effect of absorbing aerosols, an effective single scattering albedo (SSA) was determined by comparing the experimental UVER with calculations carried out with the TUV radiative transfer model.

Direct-to-diffuse UV Solar Irradiance Ratio for a UV rotating Shadowband Spectroradiometer and a UV Multi-filter Rotating Shadowband Radiometer

NASA Astrophysics Data System (ADS)

Lantz, K.; Kiedron, P.; Petropavlovskikh, I.; Michalsky, J.; Slusser, J.

2008-12-01

. Two spectroradiometers reside that measure direct and diffuse UV solar irradiance are located at the Table Mountain Test Facility, 8 km north of Boulder, CO. The UV- Rotating Shadowband Spectrograph (UV-RSS) measures diffuse and direct solar irradiance from 290 - 400 nm. The UV Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR) measures diffuse and direct solar irradiance in seven 2-nm wide bands, i.e. 300, 305, 311, 317, 325, and 368 nm. The purpose of the work is to compare radiative transfer model calculations (TUV) with the results from the UV-Rotating Shadowband Spectroradiometer (UV-RSS) and the UV-MFRSR to estimate direct-to-diffuse solar irradiance ratios (DDR) that are used to evaluate the possibility of retrieving aerosol single scattering albedo (SSA) under a variety of atmospheric conditions: large and small aerosol loading, large and small surface albedo. For the radiative transfer calculations, total ozone measurements are obtained from a collocated Brewer spectrophotometer.

Fluorescence spectra and biological activity of aerosolized bacillus spores and MS2 bacteriophage exposed to ozone at different relative humidities in a rotating drum

NASA Astrophysics Data System (ADS)

Ratnesar-Shumate, Shanna; Pan, Yong-Le; Hill, Steven C.; Kinahan, Sean; Corson, Elizabeth; Eshbaugh, Jonathan; Santarpia, Joshua L.

2015-03-01

Biological aerosols (bioaerosols) released into the environment may undergo physical and chemical transformations when exposed to atmospheric constituents such as solar irradiation, reactive oxygenated species, ozone, free radicals, water vapor and pollutants. Aging experiments were performed in a rotating drum chamber subjecting bioaerosols, Bacillus thuringiensis Al Hakam (BtAH) spores and MS2 bacteriophages to ozone at 0 and 150 ppb, and relative humidities (RH) at 10%, 50%, and 80+%. Fluorescence spectra and intensities of the aerosols as a function of time in the reaction chamber were measured with a single particle fluorescence spectrometer (SPFS) and an Ultra-Violet Aerodynamic Particle Sizer® Spectrometer (UV-APS). Losses in biological activity were measured by culture and quantitative polymerase chain reaction (q-PCR) assay. For both types of aerosols the largest change in fluorescence emission was between 280 and 400 nm when excited at 263 nm followed by fluorescence emission between 380 and 700 nm when excited at 351 nm. The fluorescence for both BtAH and MS2 were observed to decrease significantly at high ozone concentration and high RH when excited at 263 nm excitation. The decreases in 263 nm excited fluorescence are indicative of hydrolysis and oxidation of tryptophan in the aerosols. Fluorescence measured with the UV-APS (355-nm excitation) increased with time for both BtAH and MS2 aerosols. A two log loss of MS2 bacteriophage infectivity was observed in the presence of ozone at ~50% and 80% RH when measured by culture and normalized for physical losses by q-PCR. Viability of BtAH spores after exposure could not be measured due to the loss of genomic material during experiments, suggesting degradation of extracelluar DNA attributable to oxidation. The results of these studies indicate that the physical and biological properties of bioaerosols change significantly after exposure to ozone and water vapor.

Fluorescence spectra and biological activity of aerosolized bacillus spores and MS2 bacteriophage exposed to ozone at different relative humidities in a rotating drum

DOE PAGES

Ratnesar-Shumate, Shanna; Pan, Yong-Le; Hill, Steven C.; ...

2015-10-14

Biological aerosols (bioaerosols) released into the environment may undergo physical and chemical transformations when exposed to atmospheric constituents such as solar irradiation, reactive oxygenated species, ozone, free radicals, water vapor and pollutants. Aging experiments were performed in a rotating drum chamber subjecting bioaerosols, Bacillus thuringiensis Al Hakam (BtAH) spores and MS2 bacteriophages to ozone at 0 and 150 ppb, and relative humidities (RH) at 10%, 50%, and 80+%. Fluorescence spectra and intensities of the aerosols as a function of time in the reaction chamber were measured with a single particle fluorescence spectrometer (SPFS) and an Ultra-Violet Aerodynamic Particle Sizer® Spectrometermore » (UV-APS). Losses in biological activity were measured by culture and quantitative polymerase chain reaction (q-PCR) assay. For both types of aerosols the largest change in fluorescence emission was between 280 and 400 nm when excited at 263 nm followed by fluorescence emission between 380 and 700 nm when excited at 351 nm. The fluorescence for both BtAH and MS2 were observed to decrease significantly at high ozone concentration and high RH when excited at 263 nm excitation. The decreases in 263 nm excited fluorescence are indicative of hydrolysis and oxidation of tryptophan in the aerosols. Fluorescence measured with the UV-APS (355-nm excitation) increased with time for both BtAH and MS2 aerosols. A two log loss of MS2 bacteriophage infectivity was observed in the presence of ozone at ~50% and 80% RH when measured by culture and normalized for physical losses by q-PCR. Viability of BtAH spores after exposure could not be measured due to the loss of genomic material during experiments, suggesting degradation of extracelluar DNA attributable to oxidation. The results of these studies indicate that the physical and biological properties of bioaerosols change significantly after exposure to ozone and water vapor.« less

Fluorescence spectra and biological activity of aerosolized bacillus spores and MS2 bacteriophage exposed to ozone at different relative humidities in a rotating drum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ratnesar-Shumate, Shanna; Pan, Yong-Le; Hill, Steven C.

Biological aerosols (bioaerosols) released into the environment may undergo physical and chemical transformations when exposed to atmospheric constituents such as solar irradiation, reactive oxygenated species, ozone, free radicals, water vapor and pollutants. Aging experiments were performed in a rotating drum chamber subjecting bioaerosols, Bacillus thuringiensis Al Hakam (BtAH) spores and MS2 bacteriophages to ozone at 0 and 150 ppb, and relative humidities (RH) at 10%, 50%, and 80+%. Fluorescence spectra and intensities of the aerosols as a function of time in the reaction chamber were measured with a single particle fluorescence spectrometer (SPFS) and an Ultra-Violet Aerodynamic Particle Sizer® Spectrometermore » (UV-APS). Losses in biological activity were measured by culture and quantitative polymerase chain reaction (q-PCR) assay. For both types of aerosols the largest change in fluorescence emission was between 280 and 400 nm when excited at 263 nm followed by fluorescence emission between 380 and 700 nm when excited at 351 nm. The fluorescence for both BtAH and MS2 were observed to decrease significantly at high ozone concentration and high RH when excited at 263 nm excitation. The decreases in 263 nm excited fluorescence are indicative of hydrolysis and oxidation of tryptophan in the aerosols. Fluorescence measured with the UV-APS (355-nm excitation) increased with time for both BtAH and MS2 aerosols. A two log loss of MS2 bacteriophage infectivity was observed in the presence of ozone at ~50% and 80% RH when measured by culture and normalized for physical losses by q-PCR. Viability of BtAH spores after exposure could not be measured due to the loss of genomic material during experiments, suggesting degradation of extracelluar DNA attributable to oxidation. The results of these studies indicate that the physical and biological properties of bioaerosols change significantly after exposure to ozone and water vapor.« less

Aerosol column absorption measurements using co-located UV-MFRSR and AERONET CIMEL instruments

NASA Astrophysics Data System (ADS)

Krotkov, N.; Labow, G.; Herman, J.; Slusser, J.; Tree, R.; Janson, G.; Durham, B.; Eck, T.; Holben, B.

2009-08-01

Column aerosol absorption properties in the visible wavelengths are measured routinely in worldwide locations by NASA AERONET network (http://aeronet.gsfc.nasa.gov), while similar optical properties in UV can be derived from diffuse and global irradiance measurements measured with Multifilter Rotating Shadowband Radiometer (MFRSR) instruments of the USDA UV-MFRSR network (http://uvb.nrel.colostate.edu). To enable direct comparisons between the two techniques, we have modified our UV-MFRSR by replacing standard 300nm filter with 440nm filter used in AERONET network. The modified UV/VIS-MFRSR has been mostly deployed at AERONET calibration site at NASA GSFC in Greenbelt, MD, but also at number of field campaigns. While the UV-MSFRSR instrument is highly susceptible to calibration drifts, these drifts can be accurately assessed using co-located AERONET direct-sun AOT data. In 2006 quartz dome has been installed atop the MFRSR diffuser, which stabilized calibration drifts in 2007-2009. After correcting for remaining calibration changes, the AOT and single scattering albedo (SSA) at the UV wavelengths can be accurately inferred by fitting the measurements of global and diffuse atmospheric transmittances with the forward RT model at each UV-MFRSR spectral channel. Derived AOT and SSA at common wavelength 440nm by two different techniques are generally in good agreement. We also found that SSA becomes smaller in the UV wavelengths and has strong wavelength dependence across blue and near-UV spectral range. The measured enhanced UV absorption might suggest the presence of selectively UV absorbing aerosols. High spectral resolution SSA measurements in UV-VIS wavelengths are called for.

Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

NASA Astrophysics Data System (ADS)

Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

2011-12-01

Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the averaged carbon oxidation state (OSc). The heterogeneous reaction of SOA with molecular halogens released from the simulated salt-pan at different simulated environmental conditions leads to changes of several physico-chemical features of the aerosol. However, the halogen release mechanisms are also affected by the presence of organic aerosols. One order of magnitude less BrO was detected by an active Differential Optical Absorption Spectroscopy (DOAS) instrument in the presence of SOA compared to experiments without SOA. This work was supported by the German Research Foundation within the HALOPROC project. Ofner, J., Krüger, H.-U., Grothe, H., Schmitt-Kopplin, P., Whitmore, K., and Zetzsch, C. (2011), Atmos. Chem. Phys., 11, 1-15.

Enhanced UV Absorption in Carbonaceous Aerosols during MILAGRO and Identification of Potential Organic Contributors.

NASA Astrophysics Data System (ADS)

Mangu, A.; Kelley, K. L.; Marchany-Rivera, A.; Kilaparty, S.; Gunawan, G.; Gaffney, J. S.; Marley, N. A.

2007-12-01

Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) during the month of March, 2006 by using a 7- channel aethalometer (Thermo-Anderson). These measurements, obtained at 370, 470, 520, 590, 660, 880, and 950 nm at a 5 minute time resolution, showed an enhanced absorption in the UV over that expected from carbon soot alone. Samples of fine atmospheric aerosols (less than 0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. The samples were collected on quartz fiber filters with high volume impactor samplers. The samples have been characterized for total carbon content (stable isotope ratio mass spectroscopy) and natural radionuclide tracers (210Pb, 210Po, 210Bi, 7Be, 13C, 14C, 40K, 15N). Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV-visible spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples (1). The continuous spectra also show an enhanced UV absorption over that expected from carbon soot and the general profiles are quite similar to those observed for humic and fulvic acids found as colloidal materials in surface and groundwaters (2), indicating the presence of humic-like substances (HULIS) in the fine aerosols. The spectra also show evidence of narrow band absorbers below 400 nm typical of polycyclic aromatics (PAH) and nitrated aromatic compounds. Spectra were also obtained on NIST standard diesel soot (SRM 2975), NIST standard air particulate matter (SRM 8785), and nitrated PAH compounds for comparison. Potential organic aerosol components are identified which contribute to the enhanced absorption observed in the field. The wavelength dependence of the mass specific absorption is obtained from these spectra and total carbon measurements. The wavelength dependence of the aerosol complex refractive index (m = n +ik) in the UV-visible spectral region is determined by application of the Kramers Kronig function. The importance of the aerosol absorption in the infrared spectral region to radiative forcing will be discussed. 1. Marley, N.A., J.S. Gaffney, J.C. Baird, C.A. Blazer, P.J. Drayton, and J.E. Frederick, Aerosol Sci. Technol., 34, 535-549, (2001). 2. N.A. Marley, J.S. Gaffney, and K.A. Orlandini, Chapter 7 in Humic/Fulvic Acids and Organic Colloidal Materials in the Environment, ACS Symposium Series 651, American Chemical Society, Washington, D.C., pp. 96-107, 1996. This work was conducted as part of the Department of Energy's Atmospheric Science Program as part of the Megacity Aerosol Experiment - Mexico City during MILAGRO. This research was supported by the Office of Science (BER), U.S. Department of Energy Grant No. DE-FG02-07ER64329. We also wish to thank Mexican Scientists and students for their assistance from the Instituto Mexicano de Petroleo (IMP) and CENICA.

Characterization of aerosol scattering and spectral absorption by unique methods: a polar/imaging nephelometer and spectral reflectance measurements of aerosol samples collected on filters

NASA Astrophysics Data System (ADS)

Dolgos, Gergely; Martins, J. Vanderlei; Remer, Lorraine A.; Correia, Alexandre L.; Tabacniks, Manfredo; Lima, Adriana R.

2010-02-01

Characterization of aerosol scattering and absorption properties is essential to accurate radiative transfer calculations in the atmosphere. Applications of this work include remote sensing of aerosols, corrections for aerosol distortions in satellite imagery of the surface, global climate models, and atmospheric beam propagation. Here we demonstrate successful instrument development at the Laboratory for Aerosols, Clouds and Optics at UMBC that better characterizes aerosol scattering phase matrix using an imaging polar nephelometer (LACO-I-Neph) and enables measurement of spectral aerosol absorption from 200 nm to 2500 nm. The LACO-I-Neph measures the scattering phase function from 1.5° to 178.5° scattering angle with sufficient sensitivity to match theoretical expectations of Rayleigh scattering of various gases. Previous measurements either lack a sufficiently wide range of measured scattering angles or their sensitivity is too low and therefore the required sample amount is prohibitively high for in situ measurements. The LACO-I-Neph also returns expected characterization of the linear polarization signal of Rayleigh scattering. Previous work demonstrated the ability of measuring spectral absorption of aerosol particles using a reflectance technique characterization of aerosol samples collected on Nuclepore filters. This first generation methodology yielded absorption measurements from 350 nm to 2500 nm. Here we demonstrate the possibility of extending this wavelength range into the deep UV, to 200 nm. This extended UV region holds much promise in identifying and characterizing aerosol types and species. The second generation, deep UV, procedure requires careful choice of filter substrates. Here the choice of substrates is explored and preliminary results are provided.

Broadband Measurement of Aerosol Extinction in the Visible Range

NASA Astrophysics Data System (ADS)

He, Quanfu; Bluvshtein, Nir; Segev, Lior; Flores, Michel; Rudich, Yinon; Washenfelder, Rebecca; Brown, Steven

2017-04-01

Atmospheric aerosols influence the Earth's radiative budget directly by scattering and absorbing incoming solar radiation. Aerosol direct forcing remains one of the largest uncertainties in quantifying the role that aerosols play in the Earth's radiative budget. The optical properties of aerosols vary as a function of wavelength, but few measurements reported the wavelength dependence of aerosol extinction cross section and complex refractive indices, particularly in the blue and visible spectral range. There is also currently a large gap in our knowledge of how the optical properties evolve as a function of atmospheric aging in the visible spectrum. In this study, we constructed a new and novel laboratory instrument to measure aerosol extinction as a function of wavelength, using cavity enhanced spectroscopy with a white light source. This broadband cavity enhanced spectroscopy (BBCES) covers the 395-700 nm spectral region using a broadband light source and a grating spectrometer with charge-coupled device detector (CCD). We evaluated this BBCES by measuring extinction cross section for aerosols that are pure scattering, slightly absorbing and strongly absorbing atomized from standard materials. We also retrieved the refractive indices from the measured extinction cross sections. Secondary organic aerosols from biogenic and anthropogenic precursors were "aged" to differential time scales (1 to 10 days) in an Oxidation Flow Reactor (OFR) under the combined influence of OH, O3 and UV light. The new BBCES was used to online measure the extinction cross sections of the SOA. This talk will provide a comprehensive understanding of aerosol optical properties alerting during aging process in the 395 - 700 nm spectrum.

Comparisons Between Ground Measurements of Broadband UV Irradiance (300-380 nm) and TOMS UV Estimates at Moscow for 1979-2000

NASA Technical Reports Server (NTRS)

Yurova, Alla Y.; Krotkov, Nicholay A.; Herman, Jay R.; Bhartia, P. K. (Technical Monitor)

2002-01-01

We show the comparisons between ground-based measurements of spectrally integrated (300 nm to 380 nm) ultraviolet (UV) irradiance with satellite estimates from the Total Ozone Mapping Spectrometer (TOMS) total ozone and reflectivity data for the whole period of TOMS measurements (1979-2000) over the Meteorological Observatory of Moscow State University (MO MSU), Moscow, Russia. Several aspects of the comparisons are analyzed, including effects of cloudiness, aerosol, and snow cover. Special emphasis is given to the effect of different spatial and temporal averaging of ground-based data when comparing with low-resolution satellite measurements (TOMS footprint area 50-200 sq km). The comparisons in cloudless scenes with different aerosol loading have revealed TOMS irradiance overestimates from +5% to +20%. A-posteriori correction of the TOMS data accounting for boundary layer aerosol absorption (single scattering albedo of 0.92) eliminates the bias for cloud-free conditions. The single scattering albedo was independently verified using CIMEL sun and sky-radiance measurements at MO MSU in September 2001. The mean relative difference between TOMS UV estimates and ground UV measurements mainly lies within 1 10% for both snow-free and snow period with a tendency to TOMS overestimation in snow-free period especially at overcast conditions when the positive bias reaches 15-17%. The analysis of interannual UV variations shows quite similar behavior for both TOMS and ground measurements (correlation coefficient r=0.8). No long-term trend in the annual mean bias was found for both clear-sky and all-sky conditions with snow and without snow. Both TOMS and ground data show positive trend in UV irradiance between 1979 and 2000. The UV trend is attributed to decreases in both cloudiness and aerosol optical thickness during the late 1990's over Moscow region. However, if the analyzed period is extended to include pre-TOMS era (1968-2000 period), no trend in ground UV irradiance is detected.

Using satellite-based measurements to explore ...

EPA Pesticide Factsheets

New particle formation (NPF) can potentially alter regional climate by increasing aerosol particle (hereafter particle) number concentrations and ultimately cloud condensation nuclei. The large scales on which NPF is manifest indicate potential to use satellite-based (inherently spatially averaged) measurements of atmospheric conditions to diagnose the occurrence of NPF and NPF characteristics. We demonstrate the potential for using satellite-measurements of insolation (UV), trace gas concentrations (sulfur dioxide (SO2), nitrogen dioxide (NO2), ammonia (NH3), formaldehyde (HCHO), ozone (O3)), aerosol optical properties (aerosol optical depth (AOD), Ångström exponent (AE)), and a proxy of biogenic volatile organic compound emissions (leaf area index (LAI), temperature (T)) as predictors for NPF characteristics: formation rates, growth rates, survival probabilities, and ultrafine particle (UFP) concentrations at five locations across North America. NPF at all sites is most frequent in spring, exhibits a one-day autocorrelation, and is associated with low condensational sink (AOD×AE) and HCHO concentrations, and high UV. However, there are important site-to-site variations in NPF frequency and characteristics, and in which of the predictor variables (particularly gas concentrations) significantly contribute to the explanatory power of regression models built to predict those characteristics. This finding may provide a partial explanation for the reported spatia

Modelled and measured effects of clouds on UV Aerosol Indices on a local, regional, and global scale

NASA Astrophysics Data System (ADS)

Penning de Vries, M.; Wagner, T.

2011-12-01

The UV Aerosol Indices (UVAI) form one of very few available tools in satellite remote sensing that provide information on aerosol absorption. The UVAI are also quite insensitive to surface type and are determined in the presence of clouds - situations where most aerosol retrieval algorithms do not work. The UVAI are most sensitive to elevated layers of absorbing aerosols, such as mineral dust and smoke, but they can also be used to study non-absorbing aerosols, such as sulphate and secondary organic aerosols. Although UVAI are determined for cloud-contaminated pixels, clouds do affect the value of UVAI in several ways: (1) they shield the underlying scene (potentially containing aerosols) from view, (2) they enhance the apparent surface albedo of an elevated aerosol layer, and (3) clouds unpolluted by aerosols also yield non-zero UVAI, here referred to as "cloudUVAI". The main purpose of this paper is to demonstrate that clouds can cause significant UVAI and that this cloudUVAI can be well modelled using simple assumptions on cloud properties. To this aim, we modelled cloudUVAI by using measured cloud optical parameters - either with low spatial resolution from SCIAMACHY, or high resolution from MERIS - as input. The modelled cloudUVAI were compared with UVAI determined from SCIAMACHY reflectances on different spatial (local, regional and global) and temporal scales (single measurement, daily means and seasonal means). The general dependencies of UVAI on cloud parameters were quite well reproduced, but several issues remain unclear: compared to the modelled cloudUVAI, measured UVAI show a bias, in particular for large cloud fractions. Also, the spread in measured UVAI is larger than in modelled cloudUVAI. In addition to the original, Lambert Equivalent Reflector (LER)-based UVAI algorithm, we have also investigated the effects of clouds on UVAI determined using the so-called Modified LER (MLER) algorithm (currently applied to TOMS and OMI data). For medium-sized clouds the MLER algorithm performs better (UVAI are closer to 0), but like for LER UVAI, MLER UVAI can become as large as -1.2 for small clouds and deviate significantly from zero for cloud fractions near 1. The effects of clouds should therefore also be taken into account when MLER UVAI data are used. Because the effects of clouds and aerosols on UVAI are not independent, a simple subtraction of modelled cloudUVAI from measured UVAI does not yield a UVAI representative of a cloud-free scene when aerosols are present. We here propose a first, simple approach for the correction of cloud effects on UVAI. The method is shown to work reasonably well for small to medium-sized clouds located above aerosols.

The complex refractive index of atmospheric and model humic-like substances (HULIS) retrieved by a cavity ring down aerosol spectrometer (CRD-AS).

PubMed

Dinar, E; Riziq, A Abo; Spindler, C; Erlick, C; Kiss, G; Rudich, Y

2008-01-01

Atmospheric aerosols absorb and reflect solar radiation causing surface cooling and heating of the atmosphere. The interaction between aerosols and radiation depends on their complex index of refraction, which is related to the particles' chemical composition. The contribution of light absorbing organic compounds, such as HUmic-LIke Substances (HULIS) to aerosol scattering and absorption is among the largest uncertainties in assessing the direct effect of aerosols on climate. Using a Cavity Ring Down Aerosol Spectrometer (CRD-AS), the complex index of refraction of aerosols containing HULIS extracted from pollution, smoke, and rural continental aerosols, and molecular weight-fractionated fulvic acid was measured at 390 nm and 532 nm. The imaginary part of the refractive index (absorption) substantially increases towards the UV range with increasing molecular weight and aromaticity. At both wavelengths, HULIS extracted from pollution and smoke particles absorb more than HULIS from the rural aerosol. Sensitivity calculations for a pollution-type aerosol containing ammonium sulfate, organic carbon (HULIS), and soot suggests that accounting for absorption by HULIS leads in most cases to a significant decrease in the single scattering albedo and to a significant increase in aerosol radiative forcing efficiency, towards more atmospheric absorption and heating. This indicates that HULIS in biomass smoke and pollution aerosols, in addition to black carbon, can contribute significantly to light absorption in the ultraviolet and visible spectral regions.

Satellite estimation of surface spectral ultraviolet irradiance using OMI data in East Asia

NASA Astrophysics Data System (ADS)

Lee, H.; Kim, J.; Jeong, U.

2017-12-01

Due to a strong influence to the human health and ecosystem environment, continuous monitoring of the surface ultraviolet (UV) irradiance is important nowadays. The amount of UVA (320-400 nm) and UVB (290-320 nm) radiation at the Earth surface depends on the extent of Rayleigh scattering by atmospheric gas molecules, the radiative absorption by ozone, radiative scattering by clouds, and both absorption and scattering by airborne aerosols. Thus advanced consideration of these factors is the essential part to establish the process of UV irradiance estimation. Also UV index (UVI) is a simple parameter to show the strength of surface UV irradiance, therefore UVI has been widely utilized for the purpose of UV monitoring. In this study, we estimate surface UV irradiance at East Asia using realistic input based on OMI Total Ozone and reflectivity, and then validate this estimated comparing to UV irradiance from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) data. In this work, we also try to develop our own retrieval algorithm for better estimation of surface irradiance. We use the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model version 2.6 for our UV irradiance calculation. The input to the VLIDORT radiative transfer calculations are the total ozone column (TOMS V7 climatology), the surface albedo (Herman and Celarier, 1997) and the cloud optical depth. Based on these, the UV irradiance is calculated based on look-up table (LUT) approach. To correct absorbing aerosol, UV irradiance algorithm added climatological aerosol information (Arola et al., 2009). The further study, we analyze the comprehensive uncertainty analysis based on LUT and all input parameters.

MAX-DOAS retrieval of aerosol extinction properties in Madrid, Spain

NASA Astrophysics Data System (ADS)

Wang, Shanshan; Cuevas, Carlos A.; Frieß, Udo; Saiz-Lopez, Alfonso

2017-04-01

We present Multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements performed in the urban environment of Madrid, Spain, from March to September 2015. The O4 absorption in the ultraviolet (UV) spectral region was used to retrieve the aerosol extinction profile using an inversion algorithm. The results show a good agreement between the hourly retrieved aerosol optical depth (AOD) and the correlative Aerosol Robotic Network (AERONET) product. Higher AODs are found in the summer season due to the more frequent occurrence of Saharan dust intrusions. The surface aerosol extinction coefficient as retrieved by the MAX-DOAS measurements was also compared to in situ PM2:5 concentrations. The level of agreement between both measurements indicates that the MAX-DOAS retrieval has the ability to characterize the extinction of aerosol particles near the surface. The retrieval algorithm was also used to study a case of severe dust intrusion on 12 May 2015. The capability of the MAX-DOAS retrieval to recognize the dust event including an elevated particle layer is investigated along with air mass back-trajectory analysis.

Radiative characteristics of clouds embedded in smoke derived from airborne multiangular measurements

NASA Astrophysics Data System (ADS)

Gautam, Ritesh; Gatebe, Charles K.; Singh, Manoj K.; Várnai, Tamás.; Poudyal, Rajesh

2016-08-01

Clouds in the presence of absorbing aerosols result in their apparent darkening, observed at the top of atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the large radiative effect and potential impacts on regional climate, above-cloud aerosols have recently been characterized in multiple satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, recent literature indicates large uncertainties in satellite retrievals of above-cloud aerosol optical depth (AOD) and single scattering albedo (SSA), which are among the most important parameters in the assessment of associated radiative effects. In this study, we analyze radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in Canada during the 2008 summer season. We found a strong positive reflectance (R) gradient in the UV-visible (VIS)-near infrared (NIR) spectrum for clouds embedded in dense smoke, as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. Several cases of clouds embedded in thick smoke were found, when the aircraft made circular/spiral measurements, which not only allowed the complete characterization of angular distribution of smoke scattering but also provided the vertical distribution of smoke and clouds (within 0.5-5 km). Specifically, the largest darkening by smoke was found in the UV/VIS, with R0.34μm reducing to 0.2 (or 20%), in contrast to 0.8 at NIR wavelengths (e.g., 1.27 µm). The observed darkening is associated with large AODs (0.5-3.0) and moderately low SSA (0.85-0.93 at 0.53 µm), resulting in a significantly large instantaneous aerosol forcing efficiency of 254 ± 47 W m-2 τ-1. Our observations of smoke-cloud radiative interactions were found to be physically consistent with theoretical plane-parallel 1-D and Monte Carlo 3-D radiative transfer calculations, capturing the observed gradient across UV-VIS-NIR. Results from this study offer insights into aerosol-cloud radiative interactions and may help in better constraining satellite retrieval algorithms.

Radiative Characteristics of Clouds Embedded in Smoke Derived from Airborne Multiangular Measurements

NASA Technical Reports Server (NTRS)

Gautam, Ritesh; Gatebe, Charles K.; Singh, Manoj; Varnai, Tamas; Poudyal, Rajesh

2016-01-01

Clouds in the presence of absorbing aerosols result in their apparent darkening, observed at the top of atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the large radiative effect and potential impacts on regional climate, above-cloud aerosols have recently been characterized in multiple satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, recent literature indicates large uncertainties in satellite retrievals of above-cloud aerosol optical depth (AOD) and single scattering albedo (SSA), which are among the most important parameters in the assessment of associated radiative effects. In this study, we analyze radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in Canada during the 2008 summer season. We found a strong positive reflectance (R) gradient in the UV-visible (VIS)-near infrared (NIR) spectrum for clouds embedded in dense smoke, as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. Several cases of clouds embedded in thick smoke were found, when the aircraft made circular/spiral measurements, which not only allowed the complete characterization of angular distribution of smoke scattering but also provided the vertical distribution of smoke and clouds (within 0.5-5 km). Specifically, the largest darkening by smoke was found in the UV/VIS, with R(sub 0.34 microns) reducing to 0.2 (or 20%), in contrast to 0.8 at NIR wavelengths (e.g., 1.27 microns). The observed darkening is associated with large AODs (0.5-3.0) and moderately low SSA (0.85-0.93 at 0.53 microns), resulting in a significantly large instantaneous aerosol forcing efficiency of 254 +/- 47 W/sq m/t. Our observations of smoke-cloud radiative interactions were found to be physically consistent with theoretical plane-parallel 1-D and Monte Carlo 3-D radiative transfer calculations, capturing the observed gradient across UV-VIS-NIR. Results from this study offer insights into aerosol-cloud radiative interactions and may help in better constraining satellite retrieval algorithms.

Accuracy Assessments and Validation of an Expanded UV Irradiance Database from Satellite Total Ozone Mapping Spectrometer (TOMS)

NASA Technical Reports Server (NTRS)

Krotkov, N. A.; Herman, J.; Fioletov, V.; Seftor, C.; Larko, D.; Vasilkov, A.

2004-01-01

The TOMS UV irradiance database (1978 to 2000) has been expanded to include 5 new products (noon irradiance at 305, 310, 324, and 380 nm, and noon erythemal-weighted irradiance), in addition to the existing erythemal daily exposure, which permit direct Comparisons with ground-based measurements from UV spectrometers. Sensitivity studies are conducted to estimate uncertainties of the new TOMS UV irradiance data due to algorithm apriori assumptions. Comparisons with Brewer spectrometers as well as filter radiometers are used to review of the sources of known errors. Inability to distinguish between snow and cloud cover using only TOMS data results in large errors in estimating surface UV using snow climatology. A correction is suggested for the case when the regional snow albedo is known from an independent source. The summer-time positive bias between TOMS UV estimations and Brewer measurements can be seen at all wavelengths. This suggests the difference is not related to ozone absorption effects. We emphasize that uncertainty of boundary layer UV aerosol absorption properties remains a major source of error in modeling UV irradiance in clear sky conditions. Neglecting aerosol absorption by the present TOMS algorithm results in a positive summertime bias in clear-sky UV estimations over many locations. Due to high aerosol variability the bias is strongly site dependent. Data from UV-shadow-band radiometer and well-calibrated CIMEL sun-sky radiometer are used to quantify the bias at NASA/GSFC site in Greenbelt, MD. Recommendations are given to enable potential users to better account for local conditions by combining standard TOMS UV data with ancillary ground measurements.

Assessment of capabilities of multiangle imaging photo-polarimetry for atmospheric correction in presence of absorbing aerosols

NASA Astrophysics Data System (ADS)

Kalashnikova, O. V.; Garay, M. J.; Xu, F.; Seidel, F. C.; Diner, D. J.

2015-12-01

Satellite remote sensing of ocean color is a critical tool for assessing the productivity of marine ecosystems and monitoring changes resulting from climatic or environmental influences. Yet water-leaving radiance comprises less than 10% of the signal measured from space, making correction for absorption and scattering by the intervening atmosphere imperative. Traditional ocean color retrieval algorithms utilize a standard set of aerosol models and the assumption of negligible water-leaving radiance in the near-infrared. Modern improvements have been developed to handle absorbing aerosols such as urban particulates in coastal areas and transported desert dust over the open ocean, where ocean fertilization can impact biological productivity at the base of the marine food chain. Even so, imperfect knowledge of the absorbing aerosol optical properties or their height distribution results in well-documented sources of error. In the UV, the problem of UV-enhanced absorption and nonsphericity of certain aerosol types are amplified due to the increased Rayleigh and aerosol optical depth, especially at off-nadir view angles. Multi-angle spectro-polarimetric measurements have been advocated as an additional tool to better understand and retrieve the aerosol properties needed for atmospheric correction for ocean color retrievals. The central concern of the work to be described is the assessment of the effects of absorbing aerosol properties on water leaving radiance measurement uncertainty by neglecting UV-enhanced absorption of carbonaceous particles and by not accounting for dust nonsphericity. In addition, we evaluate the polarimetric sensitivity of absorbing aerosol properties in light of measurement uncertainties achievable for the next generation of multi-angle polarimetric imaging instruments, and demonstrate advantages and disadvantages of wavelength selection in the UV/VNIR range. The phase matrices for the spherical smoke particles were calculated using a standard Mie code, while those for non-spherical dust particles were calculated using the numerical approach described by Dubovik et al., 2006. A vector Markov Chain radiative transfer code including bio-optical models was used to evaluate TOA and water leaving radiances.

Comparison of the response of four aerosol detectors used with ultra high pressure liquid chromatography.

PubMed

Hutchinson, Joseph P; Li, Jianfeng; Farrell, William; Groeber, Elizabeth; Szucs, Roman; Dicinoski, Greg; Haddad, Paul R

2011-03-25

The responses of four different types of aerosol detectors have been evaluated and compared to establish their potential use as a universal detector in conjunction with ultra high pressure liquid chromatography (UHPLC). Two charged-aerosol detectors, namely Corona CAD and Corona Ultra, and also two different types of light-scattering detectors (an evaporative light scattering detector, and a nano-quantity analyte detector [NQAD]) were evaluated. The responses of these detectors were systematically investigated under changing experimental and instrumental parameters, such as the mobile phase flow-rate, analyte concentration, mobile phase composition, nebulizer temperature, evaporator temperature, evaporator gas flow-rate and instrumental signal filtering after detection. It was found that these parameters exerted non-linear effects on the responses of the aerosol detectors and must therefore be considered when designing analytical separation conditions, particularly when gradient elution is performed. Identical reversed-phase gradient separations were compared on all four aerosol detectors and further compared with UV detection at 200 nm. The aerosol detectors were able to detect all 11 analytes in a test set comprising species having a variety of physicochemical properties, whilst UV detection was applicable only to those analytes containing chromophores. The reproducibility of the detector response for 11 analytes over 10 consecutive separations was found to be approximately 5% for the charged-aerosol detectors and approximately 11% for the light-scattering detectors. The tested analytes included semi-volatile species which exhibited a more variable response on the aerosol detectors. Peak efficiencies were generally better on the aerosol detectors in comparison to UV detection and particularly so for the light-scattering detectors which exhibited efficiencies of around 110,000 plates per metre. Limits of detection were calculated using different mobile phase compositions and the NQAD detector was found to be the most sensitive (LOD of 10 ng/mL), followed by the Corona CAD (76 ng/mL), then UV detection at 200 nm (178 ng/mL) using an injection volume of 25 μL. Copyright © 2011 Elsevier B.V. All rights reserved.

Direct on-strip analysis of size- and time-resolved aerosol impactor samples using laser induced fluorescence spectra excited at 263 and 351 nm.

PubMed

Wang, Chuji; Pan, Yong-Le; James, Deryck; Wetmore, Alan E; Redding, Brandon

2014-04-11

We report a novel atmospheric aerosol characterization technique, in which dual wavelength UV laser induced fluorescence (LIF) spectrometry marries an eight-stage rotating drum impactor (RDI), namely UV-LIF-RDI, to achieve size- and time-resolved analysis of aerosol particles on-strip. The UV-LIF-RDI technique measured LIF spectra via direct laser beam illumination onto the particles that were impacted on a RDI strip with a spatial resolution of 1.2mm, equivalent to an averaged time resolution in the aerosol sampling of 3.6 h. Excited by a 263 nm or 351 nm laser, more than 2000 LIF spectra within a 3-week aerosol collection time period were obtained from the eight individual RDI strips that collected particles in eight different sizes ranging from 0.09 to 10 μm in Djibouti. Based on the known fluorescence database from atmospheric aerosols in the US, the LIF spectra obtained from the Djibouti aerosol samples were found to be dominated by fluorescence clusters 2, 5, and 8 (peaked at 330, 370, and 475 nm) when excited at 263 nm and by fluorescence clusters 1, 2, 5, and 6 (peaked at 390 and 460 nm) when excited at 351 nm. Size- and time-dependent variations of the fluorescence spectra revealed some size and time evolution behavior of organic and biological aerosols from the atmosphere in Djibouti. Moreover, this analytical technique could locate the possible sources and chemical compositions contributing to these fluorescence clusters. Advantages, limitations, and future developments of this new aerosol analysis technique are also discussed. Published by Elsevier B.V.

Aerobiology of the built environment: Synergy between Legionella and fungi.

PubMed

Alum, Absar; Isaacs, Galahad Zachariah

2016-09-02

The modern built environment (BE) design creates unique ecological niches ideal for the survival and mutual interaction of microbial communities. This investigation focused on the synergistic relations between Legionella and the fungal species commonly found in BEs and the impact of these synergistic relationships on the survival and transmission of Legionella. A field study was conducted to identify the types and concentrations of fungi in BEs. The fungal isolates purified from BEs were cocultured with Legionella to study their synergistic association. Cocultured Legionella cells were aerosolized in an air-tight chamber to evaluate the efficacy of ultraviolet (UV) to inactivate these cells. Aspergillus, Alternaria, and Cladosporium were the most common fungi detected in samples that tested positive for Legionella. After coculturing, Legionella cells were detected inside fungal hyphae. The microscopic observations of Legionella internalization in fungal hyphae were confirmed by molecular analyses. UV disinfection of the aerosolized Legionella cells that were cocultured with fungi indicated that fungal spores and propagules act as a shield against UV radiation. The shield effect of fungal spores on Legionella cells was quantified at >2.5 log10. This study provides the first evidence, to our knowledge, of Legionella cell presence inside fungi detected in an indoor environment. This symbiotic relationship with fungi results in longer survival of Legionella under ambient conditions and provides protection against UV rays. Copyright © 2016. Published by Elsevier Inc.

Infrared Absorption by Atmospheric Aerosols in Mexico City during MILAGRO.

NASA Astrophysics Data System (ADS)

Kelley, K. L.; Mangu, A.; Gaffney, J. S.; Marley, N. A.

2007-12-01

Past research in our group using cylindrical internal reflectance spectroscopy has indicated that aqueous aerosols could contribute to the radiative warming as greenhouse species (1,2). Although aerosol radiative effects have been known for sometime and are considered one of the major uncertainties in climate change modeling, most of the studies have focused on the forcing due to scattering and absorption of radiation in the uv- visible region (3). Infrared spectral information also allows the confirmation of key functional groups that are responsible for enhanced absorption observations from secondary organics in the uv-visible region. This work extends our efforts to evaluate the infrared absorption by aerosols, particularly organics, that are now found to be a major fraction of urban and regional aerosols in the 0.1 to 1.0 micron size range and to help identify key types of organics that can contribute to aerosol absorption. During the MILAGRO campaign, quartz filter samples were taken at 12-hour intervals from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. These samples were taken at the two super-sites, T-0 (Instituto Mexicano de Petroleo in Mexico City) and T-1 (Universidad Technologica de Tecamac, State of Mexico). The samples have been characterized for total carbon content (stable isotope mass spectroscopy) and natural radionuclide tracers, as well as for their UV-visible spectroscopic properties by using integrating sphere diffuse reflectance spectroscopy (Beckman DU with a Labsphere accessory). These same samples have been characterized in the mid and near infrared spectral ranges using diffuse reflection spectroscopy (Nicolet 6700 FTIR with a Smart Collector accessory). Aerosol samples were removed from the surfaces of the aerosol filters by using Si-Carb sampler. The samples clearly indicate the presence of carbonyl organic constituents and the spectra are quite similar to those observed for humic and fulvic acids found as colloidal materials in surface and groundwaters (4). Examples of the IR spectra obtained and variance as a function of time at the two sites will be presented. The spectra are taken in Kubelka - Munk format, which also allows the infrared absorption strengths to be evaluated as function of wavelength. The wavelength dependence of the aerosol complex refractive index (m = n + ik) in the infrared spectral region is determined by application of the Kramers Kronig function. The importance of the aerosol absorption in the infrared spectral region to radiative forcing will be discussed. 1. N.A. Marley, J.S. Gaffney, and M.M. Cunningham,Environ. Sci. Technol. 27 2864-2869 (1993). 2. N.A. Marley, J.S. Gaffney, and M.M. Cunningham, Spectroscopy 7 44-53 (1992). 3. J.S. Gaffney and N.A. Marley, Atmospheric Environment, New Directions contribution, 32, 2873-2874 (1998). 4. N.A. Marley, J.S. Gaffney, and K.A. Orlandini, Chapter 7 in Humic/Fulvic Acids and Organic Colloidal Materials in the Environment, ACS Symposium Series 651, American Chemical Society, Washington, D.C., pp. 96-107, 1996. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX- Mex) under the support of the Atmospheric Science Program. This research was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328.

Evaluation of ultraviolet radiation, ozone and aerosol interactions in the troposphere using automatic differentiation. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmichael, G.R.; Potra, F.

1998-10-06

A major goal of this research was to quantify the interactions between UVR, ozone and aerosols. One method of quantification was to calculate sensitivity coefficients. A novel aspect of this work was the use of Automatic Differentiation software to calculate the sensitivities. The authors demonstrated the use of ADIFOR for the first time in a dimensional framework. Automatic Differentiation was used to calculate such quantities as: sensitivities of UV-B fluxes to changes in ozone and aerosols in the stratosphere and the troposphere; changes in ozone production/destruction rates to changes in UV-B flux; aerosol properties including loading, scattering properties (including relativemore » humidity effects), and composition (mineral dust, soot, and sulfate aerosol, etc.). The combined radiation/chemistry model offers an important test of the utility of Automatic Differentiation as a tool in atmospheric modeling.« less

Effects of urban agglomeration on surface-UV doses: a comparison of Brewer measurements in Warsaw and Belsk, Poland, for the period 2013-2015

NASA Astrophysics Data System (ADS)

Czerwińska, Agnieszka E.; Krzyścin, Janusz W.; Jarosławski, Janusz; Posyniak, Michał

2016-11-01

Specific aerosols and cloud properties over large urban regions seem to generate an island, similar to the well-known urban heat island, leading to lower ultraviolet (UV) radiation intensity compared to the surrounding less polluted areas, thus creating a shield against excessive human exposure to UV radiation. The present study focuses on differences between erythemal and UVA (324 nm) doses measured by the Brewer spectrophotometers in Warsaw (52.3° N, 21.0° E) and Belsk (51.8° N, 20.8° E). The latter is a rural region located about 60 km south-west of the city. Ratios between erythemal and UVA partly daily doses, obtained during all-sky and cloudless-sky conditions for the period May 2013-December 2015, were analysed to infer a specific cloud and aerosol forcing on the surface UV doses over Warsaw. Radiative model simulations were carried out to find sources of the observed differences between the sites. It was found that Warsaw urban agglomeration induced 8 and 6 % attenuation of the erythemal and UVA doses respectively. This is mostly due to the lower sun elevation in Warsaw during the near-noon measurements and the larger optical depth of the city aerosols and increased cloudiness. It could be hypothesised that the expected stronger absorption of the solar UV radiation by urban aerosols is compensated for here by a higher surface reflectivity over the city.

UV-B measurements in India

NASA Astrophysics Data System (ADS)

Prasad, B. S. N.; Gayathri, H. B.; Muralikrishnan, N.

1992-01-01

Global UV-B flux (sum of direct and diffuse radiations) data at four wavelengths 280, 290, 300 and 310 nm are recorded at several locations in India as part of Indian Middle Atmosphere Programme (IMAP). The stations have been selected considering distinct geographic features and possible influence of atmospheric aerosols and particulates on the ground reaching UV-B flux. Mysore (12.6°N, 76.6°E) has been selected as a continental station largely free from any industrial pollution and large scale bio-mass burning. An examination of the ground reaching UV-B flux at Mysore shows a marked dirunal and seasonal asymmetry. This can be attributed to the seasonally varying atmospheric aerosols and particulates which influence the scattering of UV-B radiation. The available parameterization models are used to reproduce the experimental UV-B irradiance by varying the input parameters to the model. These results on the dirunal and seasonal variation of global UV-B flux from experiment and models are discussed in this paper.

Photochemical Cycling of Humic-Like Substances in Atmospheric Aerosols

NASA Astrophysics Data System (ADS)

Rincon, A. G.; Guzman, M. I.; Hoffmann, M. R.; Colussi, A. J.

2007-12-01

Colored, humic-like substances (HULIS) arising from the biodegradation of organic detritus are widespread in natural surface waters, where they ultimately undergo solar photolysis into small alpha-dicarbonylic species, such as glyoxal, glyoxylic and pyruvic acids. Diversely generated and chemically dissimilar HULIS are also found in the atmospheric aerosol. How are significant levels of colored HULIS produced and sustained in the concentrated aerosol phase under intense solar irradiation? Here, this issue is tackled by investigating the solar photolysis of aqueous pyruvic acid (PA) solutions at concentrations representative of the atmospheric aerosol using UV-absorption, high resolution electrospray mass, and nuclear magnetic resonance spectrometries. Under such conditions, PA is not photodegraded but yields polyfunctional polymers, whose mass and UV-absorption spectra remain unaffected after 3, 8 and 22 h photolysis. Unless diluted, these polymers undergo condensation/polymerization in the post-photolysis period into mass < 700 Da species that absorb in the visible, and are bleached upon resuming irradiation. The re- photolyzed solutions recover the mass and UV-absorption spectra of first photolyzed solutions. Whereas initial pH has no effect on the mechanism of reaction, ammonium bisulfate, a major component of the aerosol, markedly influences these processes. These findings suggest that the chemical identity and concentration levels of complex organic substances in the aerosol are the result of dynamic photochemical processing in the condensed phase.

Aerosol layer height from synergistic use of VIIRS and OMPS

NASA Astrophysics Data System (ADS)

Lee, J.; Hsu, N. Y. C.; Sayer, A. M.; Kim, W.; Seftor, C. J.

2017-12-01

This study presents an Aerosol Single-scattering albedo and Height Estimation (ASHE) algorithm, which retrieves the height of UV-absorbing aerosols by synergistically using the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Ozone Mapping and Profiler Suite (OMPS). ASHE provides height information over a much broader area than ground-based or spaceborne lidar measurements by benefitting from the wide swaths of the two instruments used. As determination of single-scattering albedo (SSA) of the aerosol layer is the most critical part for the performance and coverage of ASHE, here we demonstrate three different strategies to constrain the SSA. First, ASHE is able to retrieve the SSA of UV-absorbing aerosols when Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) provides vertical profiles of the aerosol layer of interest. Second, Aerosol Robotic Network (AERONET) inversions can directly constrain the SSA of the aerosol layer when collocated with VIIRS or OMPS. Last, a SSA climatology from ASHE, AERONET, or other data sources can be used for large-scale, aged aerosol events, for which climatological SSA is well-known, at the cost of a slight decrease in retrieval accuracy. The same algorithm can be applied to measurements of similar type, such as those made by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI), for a long-term, consistent data record.

Dust Aerosol Particle Size at the Mars Science Laboratory Landing Site

NASA Astrophysics Data System (ADS)

Vicente-Retortillo, Alvaro; Martínez, Germán; Renno, Nilton; Lemmon, Mark; de la Torre-Juárez, Manuel

2017-04-01

We have developed a new methodology to retrieve dust aerosol particle size from Mars Science Laboratory (MSL) observations [1]. We use photodiode output currents measured by the Rover Environmental Monitoring Station (REMS) UV sensor (UVS), ancillary data records (ADR) containing the geometry of the rover and the Sun, and values of the atmospheric opacity retrieved from Mastcam measurements. In particular, we analyze REMS UVS measurements when the Sun is blocked by the masthead and the mast of the rover since the behavior of the output currents during these shadow events depends on the dust phase function, which depends on particle size. The retrieved dust effective radii show a significant seasonal variability, ranging from 0.6 μm during the low opacity season (Ls = 60° - 140°) to 2 μm during the high opacity season (Ls = 180° - 360°). The relationship between atmospheric opacity and dust particle size indicates that dust-lifting events originate at various distances from Gale Crater. The external origin of high dust content events is consistent with the strong and persistent northerly and northwesterly winds at Gale Crater during the perihelion season centered around Ls = 270° [2]. From an interannual perspective, the general behavior of the particle size evolution in MY 31-32 is similar to that in MY 32-33, although some differences are noted. During the low opacity season (Ls = 60° - 140°), the retrieved dust effective radii in MY 33 are significantly lower than in MY 32. A larger contribution of water ice clouds to the total atmospheric opacity during the aphelion season of MY 33 can partially explain such a departure. Differences during the perihelion season are caused by interannual variability of enhanced opacity events. The determination of dust aerosol particle size is important to improve the accuracy of models in simulating the UV environment at the surface [3] and in predicting heating rates, which affect the atmospheric thermal and dynamical fields, and aerosol atmospheric transport, including gravitational settling rates. References: [1] Vicente-Retortillo, A. et al., GRL, submitted. [2] Rafkin, S. et al. (2016), Icarus, 280, 114-138. [3] Webster, C.R., et al. (2016), AGU Fall Meeting.

Changes in biologically active ultraviolet radiation reaching the Earth's surface.

PubMed

McKenzie, Richard L; Björn, Lars Olof; Bais, Alkiviadis; Ilyasad, Mohammad

2003-01-01

Since publication of the 1998 UNEP Assessment, there has been continued rapid expansion of the literature on UV-B radiation. Many measurements have demonstrated the inverse relationship between column ozone amount and UV radiation, and in a few cases long-term increases due to ozone decreases have been identified. The quantity, quality and availability of ground-based UV measurements relevant to assessing the environmental impacts of ozone changes continue to improve. Recent studies have contributed to delineating regional and temporal differences due to aerosols, clouds, and ozone. Improvements in radiative transfer modelling capability now enable more accurate characterization of clouds, snow-cover, and topographical effects. A standardized scale for reporting UV to the public has gained wide acceptance. There has been increased use of satellite data to estimate geographic variability and trends in UV. Progress has been made in assessing the utility of satellite retrievals of UV radiation by comparison with measurements at the Earth's surface. Global climatologies of UV radiation are now available on the Internet. Anthropogenic aerosols play a more important role in attenuating UV irradiances than has been assumed previously, and this will have implications for the accuracy of UV retrievals from satellite data. Progress has been made inferring historical levels of UV radiation using measurements of ozone (from satellites or from ground-based networks) in conjunction with measurements of total solar radiation obtained from extensive meteorological networks. We cannot yet be sure whether global ozone has reached a minimum. Atmospheric chlorine concentrations are beginning to decrease. However, bromine concentrations are still increasing. While these halogen concentrations remain high, the ozone layer remains vulnerable to further depletion from events such as volcanic eruptions that inject material into the stratosphere. Interactions between global warming and ozone depletion could delay ozone recovery by several years, and this topic remains an area of intense research interest. Future changes in greenhouse gases will affect the future evolution of ozone through chemical, radiative, and dynamic processes In this highly coupled system, an evaluation of the relative importance of these processes is difficult: studies are ongoing. A reliable assessment of these effects on total column ozone is limited by uncertainties in lower stratospheric response to these changes. At several sites, changes in UV differ from those expected from ozone changes alone, possibly as a result of long-term changes in aerosols, snow cover, or clouds. This indicates a possible interaction between climate change and UV radiation. Cloud reflectance measured by satellite has shown a long-term increase at some locations, especially in the Antarctic region, but also in Central Europe, which would tend to reduce the UV radiation. Even with the expected decreases in atmospheric chlorine, it will be several years before the beginning of an ozone recovery can be unambiguously identified at individual locations. Because UV-B is more variable than ozone, any identification of its recovery would be further delayed.

The atmospheric structure and dynamical properties of Neptune derived from ground-based and IUE spectrophotometry

NASA Technical Reports Server (NTRS)

Baines, Kevin H.; Smith, Wm. Hayden

1990-01-01

A wide range of recent full-disk spectral observations is used to constrain the atmospheric structure and dynamical properties of Neptune; analytical determinations are made of the abundances of such spectrally active gas species as the deep-atmosphere CH4 molar fraction and the mean ortho/para hydrogen ratio in the visible atmosphere, as well as stratospheric and tropospheric aerosol properties. Compared to Uranus, the greater abundance and shorter lifetimes of Neptunian particulates in the stratospheric region irradiated by the solar UV flux indicate that such radiation is the darkening agent of stratospheric aerosols on both planets.

A study of aerosol absorption and height retrievals with a hyperspectral (UV to NIR) passive sensor

NASA Astrophysics Data System (ADS)

Gasso, S.

2017-12-01

With the deployment of the first sensor (TOMS, in 1978) with capabilities to detect aerosol absorption (AA) from space, there has been a continuous evolution in hardware and algorithms used to measured this property. Although with TOMS and its more advanced successors (such as OMI) made significant progress in globally characterizing AA , there is room for improvement especially by taking advantage of sensors with extended spectral coverage (UV to NIR) and high spatial resolution (<1 km). While such unique sensor does not exist yet, the collocation of observations from different platforms that jointly fulfill those characteristics (e.g. A-Train, S-NPP) confirm that it is possible to fully retrieve all AA parameters that modulate absorption in the upwelling radiance (AOD, SSA and aerosol layer height). However, such combined approaches still have some drawbacks such as the difficulty to account for cloud contamination. The upcoming deployment of satellite detectors with the desired features all in one sensor (PACE, TropOMI, GEMS) prompt a revision of the AA retrieval technique used in past approaches. In particular,the TropOMI mission, a hyperspectral UV-to-NIR sensor with moderate ( 5km nadir pixel) spatial resolution to be launched in Fall 2017. In addition , the sensor will include sensing capabilities for the wavelength range of the Oxygen bands A and B at very high wavelength resolution. This study will be centered on the aerosol detection capabilities of TropOMI. Because the spectral range covered, it is theoretically possible to simultaneously retrieve the aerosol optical depth, the single scattering albedo and aerosol mean height without assuming any of them as it was the case with previous retrieval approaches. Specifically, we intend to present a theoretical study based on simulated radiances at selected UV, VIS and near-IR bands (including the Oxygen bands) and evaluate the sensitivity of this sensor to different levels of aerosol concentration, height and absorption properties (imaginary index) along with particle size distribution.

Preliminary results of aerosols' optical properties studied with EPF measurements from the SPICAM/UV instrument

NASA Astrophysics Data System (ADS)

Willame, Y.; Vandaele, A.-C.; Depiesse, C.; Gillotay, D.; Kochenova, S.; Montmessin, F.

2011-10-01

Aerosols on Mars have an important impact on the radiative transfer properties of its atmosphere. Today their spectral properties and therefore their interaction with UV radiation are only poorly known. Improving the radiative transfer modeling requires a better knowledge of their characteristics, in particular of their phase function, single scattering albedo and opacity. We will show that such information can be accessed by using EPF observations.

Numerical Study on the Particle Trajectory Tracking in a Micro-UV Bio-Fluorescence Sensor.

PubMed

Byeon, Sun-Seok; Cho, Moon-Young; Lee, Jong-Chul; Kim, Youn-Jea

2015-03-01

A micro-UV bio-fluorescence sensor was developed to detect primary biological aerosols including bacteria, bacterial spores, fungal spores, pollens, viruses, algae, etc. In order to effectively detect the bio-particles in a micro-UV bio-fluorescence sensor, numerical calculations were performed to adjust for appropriate flow conditions of the sensor by regulating the sample aerosols and sheath flow. In particular, a CFD-based model of hydrodynamic processes was developed by computing the trajectory of particles using commercially available ANSYS CFX-14 software and the Lagrangian tracking model. The established model was evaluated with regard to the variation of sheath flow rate and particle size. Results showed that the sheath flow was changed rapidly at the end of nozzle tip, but the sample particles moved near the center of aerosol jet for aerodynamic focusing with little deviation from the axis.

Analysis of reflectance spectra of UV-absorbing aerosol scenes measured by SCIAMACHY

NASA Astrophysics Data System (ADS)

de Graaf, M.; Stammes, P.; Aben, E. A. A.

2007-01-01

Reflectance spectra from 280-1750 nm of typical desert dust aerosol (DDA) and biomass burning aerosol (BBA) scenes over oceans are presented, measured by the space-borne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). DDA and BBA are both UV-absorbing aerosols, but their effect on the top-of-atmosphere (TOA) reflectance is different due to differences in the way mineral aerosols and smoke reflect and absorb radiation. Mineral aerosols are typically large, inert particles, found in warm, dry continental air. Smoke particles, on the other hand, are usually small particles, although often clustered, chemically very active and highly variable in composition. Moreover, BBA are hygroscopic and over oceans BBA were invariably found in cloudy scenes. TOA reflectance spectra of typical DDA and BBA scenes were analyzed, using radiative transfer simulations, and compared. The DDA spectrum was successfully simulated using a layer with a bimodal size distribution of mineral aerosols in a clear sky. The spectrum of the BBA scene, however, was determined by the interaction between cloud droplets and smoke particles, as is shown by simulations with a model of separate aerosol and cloud layers and models with internally and externally mixed aerosol/cloud layers. The occurrence of clouds in smoke scenes when sufficient water vapor is present usually prevents the detection of optical properties of these aerosol plumes using space-borne sensors. However, the Absorbing Aerosol Index (AAI), a UV color index, is not sensitive to scattering aerosols and clouds and can be used to detect these otherwise obscured aerosol plumes over clouds. The amount of absorption of radiation can be expressed using the absorption optical thickness. The absorption optical thickness in the DDA case was 0.42 (340 nm) and 0.14 (550 nm) for an aerosol layer of optical thickness 1.74 (550 nm). In the BBA case the absorption optical thickness was 0.18 (340 nm) and 0.10 (550 nm) for an aerosol/cloud layer of optical thickness 20.0 (550 nm). However, this reduced the cloud albedo by about 0.2 (340 nm) and 0.15 (550 nm). This method can be an important tool to estimate the global impact of absorption of shortwave radiation by smoke and industrial aerosols inside clouds.

UV spectral irradiance measurements in New Zealand: Effects of Pinatubo volcanic aerosol

NASA Technical Reports Server (NTRS)

Mckenzie, Richard L.

1994-01-01

Since late 1989, regular UV spectral irradiance measurements have been made at Lauder, New Zealand (45 deg S, 170 deg E), whenever weather permits. Here, the instrumentation and measurement strategy are outlined, and early results are discussed. Following the eruption of Mt Pinatubo in June 1991, large amounts of volcanic aerosol were injected into the stratosphere and were subsequently transported to New Zealand's latitudes in the latter half of 1991. This provides an opportunity to investigate the effects of volcanic aerosols on UV irradiances measured at this clean-air site. Although changes in global (sum of diffuse plus direct) irradiances were below the detection threshold, there were significant changes in the partitioning of radiation between the direct beam and diffuse skylight. Decreases by nearly a factor of two in the direct/diffuse ratio were observed at longer wavelengths, and at smaller solar zenith angles (sza's). The aerosol optical depth due to volcanic aerosol over Lauder in December 1991 was 0.15 plus or minus 0.02 at 450 nm, with lower values at shorter wavelengths. Although effects were relatively small in the UVB region, an implication of the changes is that the contrast between shade and direct sun is reduced, so that shaded areas received relatively more radiation in the summer of 1991/92 in New Zealand.

Field test of a new instrument to measure UV/Vis (300-700 nm) ambient aerosol extinction spectra in Colorado during DISCOVER-AQ

NASA Astrophysics Data System (ADS)

Jordan, C. E.; Anderson, B. E.; Beyersdorf, A. J.; Dibb, J. E.; Greenslade, M. E.; Martin, R.; Scheuer, E. M.; Shook, M.; Thornhill, K. L., II; Troop, D.; Winstead, E.; Ziemba, L. D.

2014-12-01

An optical instrument has been developed to investigate aerosol extinction spectra in the ambient atmosphere. Based on a White-type cell design and using a differential optical approach, aerosol extinction spectra over the 300-700 nm ultraviolet and visible (UV/Vis) wavelength range are obtained. Laboratory tests conducted at NASA Langley Research Center (NASA LaRC) in March 2014 showed good agreement with Cavity Attenuated Phase Shift (CAPS PMex, Aerodyne Research) extinction measurements (at 450, 530, and 630 nm) for a variety of aerosols, e.g., scatterers such as polystyrene latex spheres and ammonium sulfate; absorbers such as dust (including pigmented minerals), smoke (generated in a miniCAST burning propane) and laboratory smoke analogs (e.g., fullerene soot and aquadag). The instrument was field tested in Colorado in July and August 2014 aboard the NASA mobile laboratory at various ground sites during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign. A description of the instrument, results from the laboratory tests, and summer field data will be presented. The instrument provides a new tool for probing in situ aerosol optical properties that may help inform remote sensing approaches well into the UV range.

The first UV spectrum of Triton - IUE observations from 2600 to 3200 A

NASA Technical Reports Server (NTRS)

Stern, S. Alan; Skinner, T. E.; Brosch, N.; Van Santvoort, J.; Trafton, L. M.

1989-01-01

The results of the first observations of Triton's spectrum below 3300 A are reported. Triton's 2700 A geometric albedo is found to be 0.28 + or - 0.04. The albedo increases monotonically from 2600 to 3200 A, with a slope of 0.13 + or - 0.03 per 1000 A. This positive slope is qualitatively similar to, but shallower than, Triton's visible albedo slope and argues against a strong Rayleigh scattering signature. Triton's integrated flux is found to be 1.5 times Pluto's, indicating Triton to be either more reflective in the UV, or bigger, or both. The redness of Triton's visible and UV colors argues against an extremely bright surface and for a larger radius than Pluto's. A lower limit on the radius of 1240 + or - 90 km is derived. The spectrum observed by IUE is consistent with either an icy surface or a suspended aerosol layer which preferentially absorbs UV light.

The formation of sulfate and elemental sulfur aerosols under varying laboratory conditions: implications for early earth.

PubMed

DeWitt, H Langley; Hasenkopf, Christa A; Trainer, Melissa G; Farmer, Delphine K; Jimenez, Jose L; McKay, Christopher P; Toon, Owen B; Tolbert, Margaret A

2010-10-01

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 × 10(9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO(2)) by UV light with λ < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are elemental sulfur (S(8)) and sulfuric acid (H(2)SO(4)) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO(2) either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H(2)) or methane (CH(4)), increased the formation of S(8). With UV photolysis, formation of S(8) aerosols is highly dependent on the initial SO(2) pressure; and S(8) is only formed at a 2% SO(2) mixing ratio and greater in the absence of a reductant, and at a 0.2% SO(2) mixing ratio and greater in the presence of 1000 ppmv CH(4). We also found that organosulfur compounds are formed from the photolysis of CH(4) and moderate amounts of SO(2). The implications for sulfur aerosols on early Earth are discussed. Key Words: S-MIF-Archean atmosphere-Early Earth-Sulfur aerosols.

Mechanical Properties of the Surface Material of Comet 67P/Churyumov-Gerasimenko Measured By the Casse Instrument Onboard the Philae Lander

NASA Astrophysics Data System (ADS)

Knapmeyer, M.; Fischer, H. H.; Seidensticker, K. J.; Arnold, W.; Faber, C.; Möhlmann, D.; Thiel, K.

2014-12-01

Satellite remote sensing of ocean color is a critical tool for assessing the productivity of marine ecosystems and monitoring changes resulting from climatic or environmental influences. Yet water-leaving radiance comprises less than 10% of the signal measured from space, making correction for absorption and scattering by the intervening atmosphere imperative. Traditional ocean color retrieval algorithms utilize a standard set of aerosol models and the assumption of negligible water-leaving radiance in the near-infrared. Modern improvements have been developed to handle absorbing aerosols such as urban particulates in coastal areas and transported desert dust over the open ocean, where ocean fertilization can impact biological productivity at the base of the marine food chain. Even so, imperfect knowledge of the absorbing aerosol optical properties or their height distribution results in well-documented sources of error. In the UV, the problem of UV-enhanced absorption and nonsphericity of certain aerosol types are amplified due to the increased Rayleigh and aerosol optical depth, especially at off-nadir view angles. Multi-angle spectro-polarimetric measurements have been advocated as an additional tool to better understand and retrieve the aerosol properties needed for atmospheric correction for ocean color retrievals. The central concern of the work to be described is the assessment of the effects of absorbing aerosol properties on water leaving radiance measurement uncertainty by neglecting UV-enhanced absorption of carbonaceous particles and by not accounting for dust nonsphericity. In addition, we evaluate the polarimetric sensitivity of absorbing aerosol properties in light of measurement uncertainties achievable for the next generation of multi-angle polarimetric imaging instruments, and demonstrate advantages and disadvantages of wavelength selection in the UV/VNIR range. The phase matrices for the spherical smoke particles were calculated using a standard Mie code, while those for non-spherical dust particles were calculated using the numerical approach described by Dubovik et al., 2006. A vector Markov Chain radiative transfer code including bio-optical models was used to evaluate TOA and water leaving radiances.

Characterization and error analysis of an operational retrieval algorithm for estimating column ozone and aerosol properties from ground-based ultra-violet irradiance measurements

NASA Astrophysics Data System (ADS)

Taylor, Thomas E.; L'Ecuyer, Tristan; Slusser, James; Stephens, Graeme; Krotkov, Nick; Davis, John; Goering, Christian

2005-08-01

Extensive sensitivity and error characteristics of a recently developed optimal estimation retrieval algorithm which simultaneously determines aerosol optical depth (AOD), aerosol single scatter albedo (SSA) and total ozone column (TOC) from ultra-violet irradiances are described. The algorithm inverts measured diffuse and direct irradiances at 7 channels in the UV spectral range obtained from the United States Department of Agriculture's (USDA) UV-B Monitoring and Research Program's (UVMRP) network of 33 ground-based UV-MFRSR instruments to produce aerosol optical properties and TOC at all seven wavelengths. Sensitivity studies of the Tropospheric Ultra-violet/Visible (TUV) radiative transfer model performed for various operating modes (Delta-Eddington versus n-stream Discrete Ordinate) over domains of AOD, SSA, TOC, asymmetry parameter and surface albedo show that the solutions are well constrained. Realistic input error budgets and diagnostic and error outputs from the retrieval are analyzed to demonstrate the atmospheric conditions under which the retrieval provides useful and significant results. After optimizing the algorithm for the USDA site in Panther Junction, Texas the retrieval algorithm was run on a cloud screened set of irradiance measurements for the month of May 2003. Comparisons to independently derived AOD's are favorable with root mean square (RMS) differences of about 3% to 7% at 300nm and less than 1% at 368nm, on May 12 and 22, 2003. This retrieval method will be used to build an aerosol climatology and provide ground-truthing of satellite measurements by running it operationally on the USDA UV network database.

Evaluation of systems for reducing the transmission of Porcine reproductive and respiratory syndrome virus by aerosol

PubMed Central

2006-01-01

Abstract The purpose of this study was to compare 3 methods for the reduction of aerosol transmission of Porcine reproductive and respiratory syndrome virus (PRRSV): high-efficiency particulate air (HEPA) filtration, low-cost filtration, and ultraviolet light (UV) irradiation. The HEPA-filtration system involved a pre-filter screen, a bag filter (EU8 rating), and a HEPA filter (EU13 rating). The low-cost-filtration system contained mosquito netting (pre-filter), a fiberglass furnace filter, and an electrostatic furnace filter. For UV irradiation, a lamp emitted UVC radiation at 253.7 nm. No form of intervention was used in the control group. The experimental facilities consisted of 2 chambers connected by a 1.3-m-long duct. Recipient pigs, housed in chamber 2, were exposed to artificial aerosols created by a mechanically operated mister containing modified live PRRSV vaccine located in chamber 1. Aerosol transmission of PRRSV occurred in 9 of the 10 control replicates, 8 of the 10 UVC-irradiation replicates, 4 of the 10 low-cost-filtration replicates, and 0 of the 10 HEPA-filtration replicates. When compared with no intervention, HEPA filtration and low-cost filtration significantly reduced PRRSV transmission (P < 0.0005 and = 0.0286, respectively), whereas UV irradiation had no effect (P = 0.5). However, low-cost filtration and UV irradiation were significantly less effective (P = 0.043 and P < 0.0005, respectively) than HEPA filtration. In conclusion, under the conditions of this study, HEPA filtration was significantly more effective at reducing aerosol transmission of PRRSV than the other methods evaluated. PMID:16548329

Evaluation of the impact of atmospheric ozone and aerosols on the horizontal global/diffuse UV Index at Livorno (Italy)

NASA Astrophysics Data System (ADS)

Scaglione, Daniele; Giulietti, Danilo; Morelli, Marco

2016-08-01

A study was conducted at Livorno (Italy) to evaluate the impact of atmospheric aerosols and ozone on the solar UV radiation and its diffuse component at ground in clear sky conditions. Solar UV radiation has been quantified in terms of UV Index (UVI), following the ISO 17166:1999/CIE S007/E-1998 international standard. UVI has been calculated by exploiting the libRadtran radiative transfer modelling software as a function of both the Aerosols Optical Depth (AOD) and the Total Ozone Column (TOC). In particular AOD and TOC values have been remotely sensed by the Ozone Monitoring Instrument (OMI) on board the NASA's EOS (Earth Observing System) satellites constellation. An experimental confirmation was also obtained by exploiting global UVI ground-based measurements from the 26/9/14 to 12/8/15 and diffuse UVI ground-based measurements from the 17/5/15 to 12/8/15. For every considered value of Solar Zenith Angle (SZA) and atmospheric condition, estimates and measurements confirm that the diffuse component contributes for more than 50% on the global UV radiation. Therefore an exposure of human skin also to diffuse solar UV radiation can be potentially harmful for health and need to be accurately monitored, e.g. by exploiting innovative applications such as a mobile app with a satellite-based UV dosimeter that has been developed. Global and diffuse UVI variations due to the atmosphere are primarily caused by the TOC variations (typically cyclic): the maximum TOC variation detected by OMI in the area under study leads to a corresponding variation in global and diffuse UVI of about 50%. Aerosols in the area concerned, mainly of maritime nature, have instead weaker effects causing a maximum variation of the global and diffuse UVI respectively of 9% and 35% with an SZA of 20° and respectively of 13% and 10% with an SZA of 60°.

UV-Vis-IR spectral complex refractive indices and optical properties of brown carbon aerosol from biomass burning

NASA Astrophysics Data System (ADS)

Sumlin, Benjamin J.; Heinson, Yuli W.; Shetty, Nishit; Pandey, Apoorva; Pattison, Robert S.; Baker, Stephen; Hao, Wei Min; Chakrabarty, Rajan K.

2018-02-01

Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering wildfires are the largest source of primary BrC, and fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density could influence the properties of the emitted aerosol. We measured in situ spectral (375-1047 nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of these fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (m = n + iκ). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (λ), moisture content, source depth, or geographic origin. With increasing λ from 375 to 532 nm, κ decreased from 0.014 to 0.003, with corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. The spectral variability of κ follows the Kramers-Kronig dispersion relation for a damped harmonic oscillator. For λ ≥ 532 nm, both κ and SSA showed no spectral dependency. We discuss differences between this study and previous work. The imaginary part κ was sensitive to changes in FPD, and we hypothesize mechanisms that might help explain this observation.

Product study of oleic acid ozonolysis as function of humidity

NASA Astrophysics Data System (ADS)

Vesna, O.; Sax, M.; Kalberer, M.; Gaschen, A.; Ammann, M.

The heterogeneous reaction of ozone with oleic acid (OA) aerosol particles was studied as function of humidity and reaction time in an aerosol flow reactor using an off-line gas chromatography mass spectrometry (GC-MS) technique. We report quantitative yields of the major C9 ozonolysis products in both gas and condensed phases and the effect of relative humidity on the product distribution. The measurements were carried out with OA aerosol particles at room temperature. The results indicate that the product yields are increasing with increasing relative humidity during the reaction. Nonanal (NN) was detected as the major gas-phase product (55.6 ± 2.3%), with 94.5 ± 2.4% of the NN yield in the gas, and 5.5 ± 2.7% in the particulate phase, whereas nonanoic, oxononanoic and azelaic acids were detected exclusively in the particulate phase. Using UV-spectrometry, we observed that peroxides make up the largest fraction of products, about half of the product aerosol mass, and their concentration decreased with increasing humidity.

Ultraviolet and visible radiation at Barrow, Alaska: Climatology and influencing factors on the basis of version 2 National Science Foundation network data

NASA Astrophysics Data System (ADS)

Bernhard, Germar; Booth, Charles R.; Ehramjian, James C.; Stone, Robert; Dutton, Ellsworth G.

2007-05-01

Spectral ultraviolet (UV) and visible irradiance has been measured near Barrow, Alaska (71°N, 157°W), between 1991 and 2005 with a SUV-100 spectroradiometer. The instrument is part of the U.S. National Science Foundation's UV Monitoring Network. Here we present results based on the recently produced "version 2" data release, which supersedes published "version 0" data. Cosine error and wavelength-shift corrections applied to the new version increased biologically effective UV dose rates by 0-10%. Corrected clear-sky measurements of different years are typically consistent to within ±3%. Measurements were complemented with radiative transfer model calculations to retrieve total ozone and surface albedo from measured spectra and for the separation of the different factors influencing UV and visible radiation. A climatology of UV and visible radiation was established, focusing on annual cycles, trends, and the effect of clouds. During several episodes in spring of abnormally low total ozone, the daily UV dose at 305 nm exceeded the climatological mean by up to a factor of 2.6. Typical noontime UV Indices during summer vary between 2 and 4; the highest UV Index measured was 5.0 and occurred when surface albedo was unusually high. Radiation levels in the UV-A and visible exhibit a strong spring-autumn asymmetry. Irradiance at 345 nm peaks on approximately 20 May, 1 month before the solstice. This asymmetry is caused by increased cloudiness in autumn and high albedo in spring, when the snow covered surface enhances downwelling UV irradiance by up to 57%. Clouds reduce UV radiation at 345 nm on average by 4% in March and by more than 40% in August. Aerosols reduce UV by typically 5%, but larger reductions were observed during Arctic haze events. Stratospheric aerosols from the Pinatubo eruption in 1991 enhanced spectral irradiance at 305 nm for large solar zenith angles. The year-to-year variations of spectral irradiance at 305 nm and of the UV Index are mostly caused by variations in total ozone and cloudiness. Changes in surface albedo that may occur in the future can have a marked impact on UV levels between May and July. No statistically significant trends in monthly mean noontime irradiance were found.

Atmospheric soundings by SPICAM occultation observations: aerosol and ozone vertical profiles

NASA Astrophysics Data System (ADS)

Montmessin, F.

2005-12-01

The SPICAM instrument is a highly versatile, dual spectrometer probing both the UV and the NIR spectral region and is currently flying around Mars onboard Mars Express. Since the beginning of MEx operations, SPICAM has collected about thousand atmospheric profiles while observing in a solar or a stellar occultation mode. UV spectra bear the signatures of several species; i.e carbon dioxide, ozone and aerosols, while infrared spectra potentially bring information on atmospheric condensates and on water vapor. This presentation will focus on the measured aerosol, ozone and water vapor profiles. For the aerosol, we will emphasize the numerous observations made in the polar night and will also discuss some high altitude clouds discovered in the southern hemisphere. Ozone and water vapor profiles will be presented along with some General Circulation Model comparisons. This work has been supported by CNES.

A UV-Vis photoacoustic spectrophotometer.

PubMed

Wiegand, Joseph R; Mathews, L Dalila; Smith, Geoffrey D

2014-06-17

A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles.

Rapid Formation of Molecular Bromine from Deliquesced NaBr Aerosol in the Presence of Ozone and UV Light

EPA Science Inventory

The formation of gas-phase bromine from aqueous sodium bromide aerosols is investigated through a combination of chamber experiments and chemical kinetics modeling. Experiments show that Br2(g) is produced rapidly from deliquesced NaBr aerosols in the presence of OH radicals prod...

Harmful and favourable ultraviolet conditions for human health over Northern Eurasia

NASA Astrophysics Data System (ADS)

Chubarova, Nataly; Zhdanova, Ekaterina

2014-05-01

We provide the analysis of the spatial and temporal distribution of ultraviolet (UV) radiation over Northern Eurasia taking into account for both its detrimental (erythema and eye-damage effects) and favourable (vitamin D synthesis) influence on human health. The UV effects on six different skin types are considered in order to cover the variety of skin types of European and Asian inhabitants. To better quantifying the vitamin D irradiance threshold we accounted for an open body fraction S as a function of effective air temperature. The spatial and temporal distribution of UV resources was estimated by radiative transfer (RT) modeling (8 stream DISORT RT code) with 1x 1 degree grid and monthly resolution. For this purpose special datasets of main input geophysical parameters (total ozone content, aerosol characteristics, surface UV albedo, UV cloud modification factor) have been created over the territory of Northern Eurasia, which can be of separate interest for the different multidisciplinary scientific applications over the PEEX domain. The new approaches were used to retrieve aerosol and cloud transmittance from different satellite and re-analysis datasets for calculating the solar UV irradiance at ground. Using model simulations and some experimental data we provide the altitude parameterization for different types of biologically active irradiance in mountainous area taking into account not only for the effects of molecular scattering but for the altitude dependence of aerosol parameters and surface albedo. Based on the new classification of UV resources (Chubarova, Zhdanova, 2013) we show that the distribution of harmful (UV deficiency and UV excess) and favorable UV conditions is regulated by various geophysical parameters (mainly, total ozone, cloudiness and open body fraction) and can significantly deviate from latitudinal dependence. The interactive tool for providing simulations of biologically active irradiance and its attribution to the different classes of UV resources is demonstrated. Reference: Natalia Chubarova, Yekaterina Zhdanova. Ultraviolet resources over Northern Eurasia, Photochemistry and Photobiology, Elsevier, 127, 2013, p. 38-51

Refractive Index and Absorption Attribution of Highly Absorbing Brown Carbon Aerosols from an Urban Indian City-Kanpur.

PubMed

Shamjad, P M; Tripathi, S N; Thamban, Navaneeth M; Vreeland, Heidi

2016-11-24

Atmospheric aerosols influence Earth's radiative balance, having both warming and cooling effects. Though many aerosols reflect radiation, carbonaceous aerosols such as black carbon and certain organic carbon species known as brown carbon have the potential to warm the atmosphere by absorbing light. Black carbon absorbs light over the entire solar spectrum whereas brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light. In developing countries, such as India, where combustion sources are prolific, the influence of brown carbon on absorption may be significant. In order to better characterize brown carbon, we present experimental and modeled absorption properties of submicron aerosols measured in an urban Indian city (Kanpur). Brown carbon here is found to be fivefold more absorbing at 365 nm wavelength compared to previous studies. Results suggest ~30% of total absorption in Kanpur is attributed to brown carbon, with primary organic aerosols contributing more than secondary organics. We report the spectral brown carbon refractive indices along with an experimentally constrained estimate of the influence of aerosol mixing state on absorption. We conclude that brown carbon in Kanpur is highly absorbing in nature and that the mixing state plays an important role in light absorption from volatile species.

Refractive Index and Absorption Attribution of Highly Absorbing Brown Carbon Aerosols from an Urban Indian City-Kanpur

PubMed Central

Shamjad, P. M.; Tripathi, S. N.; Thamban, Navaneeth M.; Vreeland, Heidi

2016-01-01

Atmospheric aerosols influence Earth’s radiative balance, having both warming and cooling effects. Though many aerosols reflect radiation, carbonaceous aerosols such as black carbon and certain organic carbon species known as brown carbon have the potential to warm the atmosphere by absorbing light. Black carbon absorbs light over the entire solar spectrum whereas brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light. In developing countries, such as India, where combustion sources are prolific, the influence of brown carbon on absorption may be significant. In order to better characterize brown carbon, we present experimental and modeled absorption properties of submicron aerosols measured in an urban Indian city (Kanpur). Brown carbon here is found to be fivefold more absorbing at 365 nm wavelength compared to previous studies. Results suggest ~30% of total absorption in Kanpur is attributed to brown carbon, with primary organic aerosols contributing more than secondary organics. We report the spectral brown carbon refractive indices along with an experimentally constrained estimate of the influence of aerosol mixing state on absorption. We conclude that brown carbon in Kanpur is highly absorbing in nature and that the mixing state plays an important role in light absorption from volatile species. PMID:27883083

Steady increase of secondary organic aerosol mass concentration and light extinction during the CARES 2010 Field Campaign

NASA Astrophysics Data System (ADS)

Gyawali, M. S.; Arnott, W. P.; Flowers, B. A.; Dubey, M. K.; Atkinson, D. B.; Song, C.; Zaveri, R. A.; Setyan, A.; Zhang, Q.; Mazzoleni, C.; Gorkowski, K.

2011-12-01

We present multispectral (355, 375, 405, 532, 870, 781, and 1047 nm) aerosol light absorption and scattering measurements for the 2010 Carbonaceous Aerosols and Radiative Effects (CARES) campaign in Sacramento, CA and the Sierra Nevada foothills. The short wavelength scattering at both sites gradually increased during the last 10 days of the campaign as diagnosed by a systematic increase in the Ångström exponent of scattering. The UV and near UV enhanced scattering was likely a consequence of the ultra and sub-micron aerosol which began to grow vigorously in the size range where scattering at shorter wavelengths begins to increase. Multispectral aerosol light absorption coefficients suggest the absence of short wavelength light absorption by brown carbon. Aerosol mass spectrometer data also shows the steady increase of secondary organic aerosol during the last 10 days of CARES. The time series of the measurements made between the two sites (T0 and T1) separated by the slope of the foothills are strikingly similar, except for isolated night time episodes of enhanced absorption at T0. This is possibly due to paving events or other nocturnal emissions markers

Passive remote sensing of aerosol layer height using near-UV multiangle polarization measurements

NASA Astrophysics Data System (ADS)

Wu, Lianghai; Hasekamp, Otto; van Diedenhoven, Bastiaan; Cairns, Brian; Yorks, John E.; Chowdhary, Jacek

2016-08-01

We demonstrate that multiangle polarization measurements in the near-UV and blue part of the spectrum are very well suited for passive remote sensing of aerosol layer height. For this purpose we use simulated measurements with different setups (different wavelength ranges, with and without polarization, different polarimetric accuracies) as well as airborne measurements from the Research Scanning Polarimeter (RSP) obtained over the continental USA. We find good agreement of the retrieved aerosol layer height from RSP with measurements from the Cloud Physics Lidar showing a mean absolute difference of less than 1 km. Furthermore, we found that the information on aerosol layer height is provided for large part by the multiangle polarization measurements with high accuracy rather than the multiangle intensity measurements. The information on aerosol layer height is significantly decreased when the shortest RSP wavelength (410 nm) is excluded from the retrieval and is virtually absent when 550 nm is used as shortest wavelength.

Analytical Stability-Indicating Methods for Alogliptin in Tablets by LC-CAD and LC-UV.

PubMed

Bertol, Charise Dallazem; Friedrich, Maria Tereza; Carlos, Graciela; Froehlich, Pedro Eduardo

2017-03-01

Stability-indicating LC methods using a UV detector and a charged aerosol detector (CAD) simultaneously were validated for the assessment of alogliptin (ALG) in tablets. The analysis was performed on a C8 column (250 × 4.6 mm, 5 μm) at a flow of 0.8 mL/min, using acetonitrile-10 mM ammonium acetate buffer (pH 3.5; 90 + 10, v/v) as mobile phase and UV detection at 275 nm. Validation followed the International Conference on Harmonization guidelines. The method was linear over the range of 25-200 μg/mL. Normality of the residuals showed a normal distribution, no autocorrelation, and homoscedasticity. LODs were 6.25 and 2.65 µg/mL and LOQs were 20.85 and 8.84 µg/mL for the CAD and the UV detector, respectively. The methods were precise and accurate. Excipients and degradation products did not interfere in the methods in studies of specificity. None of the factors studied in the analysis of robustness had a significant effect on the quantification of the ALG by the Pareto chart. The results of the assay obtained with LC-CAD and LC-UV were similar. The methods could be considered interchangeable and stability-indicating, and can be applied as an appropriate QC tool for analysis of ALG in tablets.

Current Status of Aerosol Retrievals from TOMS

NASA Technical Reports Server (NTRS)

Torres, O.; Herman, J. R.; Bhartia, P. K.; Ginoux, P.

1999-01-01

Properties of atmospheric aerosols over all land and water surfaces are retrieved from TOMS measurements of backscattered radiances. The TOMS technique, uses observations at two wavelengths. In the near ultraviolet (330-380 nm) range, where the effects of gaseous absorption are negligible. The retrieved properties are optical depth and a measure of aerosol absorptivity, generally expressed as single scattering albedo. The main sources of error of the TOMS aerosol products are sub-pixel cloud contamination and uncertainty on the height above the surface of UV-absorbing aerosol layers. The first error source is related to the large footprint (50 x 50 km at nadir) of the sensor, and the lack of detection capability of sub-pixel size clouds. The uncertainty associated with the height of the absorbing aerosol layers, on the other hand, is related to the pressure dependence of the molecular scattering process, which is the basis of the near-UV method of absorbing aerosol detection. The detection of non-absorbing aerosols is not sensitive to aerosol layer height. We will report on the ongoing work to overcome both of these difficulties. Coincident measurements of high spatial resolution thermal infrared radiances are used to address the cloud contamination issue. Mostly clear scenes for aerosol retrieval are selected by examining the spatial homogeneity of the IR radiance measurements within a TOMS pixel. The approach to reduce the uncertainty associated with the height of the aerosol layer by making use of a chemical transport model will also be discussed.

Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

NASA Astrophysics Data System (ADS)

Carlund, Thomas; Kouremeti, Natalia; Kazadzis, Stelios; Gröbner, Julian

2017-03-01

The determination of aerosol properties, especially the aerosol optical depth (AOD) in the ultraviolet (UV) wavelength region, is of great importance for understanding the climatological variability of UV radiation. However, operational retrievals of AOD at the biologically most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR (UV precision filter radiometer) sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high-altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V0) derived from Langley plot calibrations underestimate the true extraterrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument's spectral response functions also result in an apparent air-mass-dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore introduced. Langley calibrations performed 13-14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a high-accuracy standard precision filter radiometer, measuring AOD at 368-862 nm wavelengths, showed consistent results. Also, very good agreement was achieved by comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB is higher than that reported from AOD instruments measuring in UVA and visible ranges. However, the precision can be high among instruments using harmonized algorithms for ozone and Rayleigh optical depth as well as for air mass terms. For 4 months of comparison measurements with the UVPFR and a Brewer, the root mean squared AOD differences were found < 0.01 at all the 306-320 nm Brewer wavelengths.

Spectral Signature of Radiative Forcing by East Asian Dust-Soot Mixture

NASA Astrophysics Data System (ADS)

Zhu, A.; Ramanathan, V.

2007-12-01

The Pacific Dust Experiment (PACDEX) provides the first detailed sampling of dust-soot mixtures from the western Pacific to the eastern Pacific Ocean. The data includes down and up spectral irradiance, mixing state of dust and soot, and other aerosol properties. This study attempts to simulate the radiative forcing by dust-soot mixtures during the experimental period. The MODTRAN band model was employed to investigate the spectral signatures of solar irradiance change induced by aerosols at moderate spectral resolutions. For the short wave band (300-1100nm) used in this study, the reduction of downward irradiance at surface by aerosols greatly enhances with increasing wavelength in the UV band (300-400nm), reaches a maximum in the blue band, then gradually decreases toward the red band. In the near-IR band (700-1100nm), irradiance reduction by aerosols shows great fluctuations in the band with center wavelength at around 940nm, 820nm, 720nm, 760nm, 690nm, where the aerosol effect is overwhelmed by the water vapor and O2 absorptions. The spectral pattern of irradiance reduction varies for different aerosol species. The maximum reduction lies at around 450nm for soot, and shifting to about 490nm for East Asian mineral dust. It's worth noting that although soot aerosols reduce more irradiance than East Asian dust in the UV and blue band, the impact of dust to the irradiance exceeds that by soot at the longer wavelength band (i.e. around 550nm). The reduction of irradiance by East Asian dust (soot) in the UV band, visible band, and near-IR accounts for about 6% (10%), 56% (64%), and 38% (26%) of total irradiance reduction. As large amount of soot aerosols are involved during the long range transport of East Asian dust, the optical properties of dust aerosols are modified with different mixing state with soot, the spectral pattern of the irradiance reduction will be changed. The study of aerosol forcing at moderate spectral resolutions has the potential application for research on aerosol mixing state and its climate impacts.

Hygroscopicity of Early Earth and Titan Laboratory Aerosol Analogs

NASA Astrophysics Data System (ADS)

Hasenkopf, C. A.; Beaver, M. R.; Freedman, M. A.; Toon, O. B.; Tolbert, M. A.

2009-12-01

We have explored the ability of organic hazes, known to exist in the atmosphere of Titan and postulated to have existed in the Archean Earth atmosphere, to act as cloud condensation nuclei (CCN). These laboratory aerosol analogs are generated via UV-photolysis of early Earth and Titan analog gas mixtures and are designed to mimic the present day atmospheric conditions on Titan and the early Earth atmosphere before the rise of oxygen. Water uptake is observed to occur on the early Earth and Titan aerosol analogs at relative humidities of 80% - 90% via optical growth measurements using cavity ring-down aerosol extinction spectroscopy. We find the optical growth of these aerosols is similar to known slightly-soluble organic acids, such as phthalic and pyromellitic acids. On average, the optical growth of the early Earth analog is slightly larger than the Titan analog. In order to translate our measurements obtained in a subsaturated regime into the CCN ability of these particles, we rely on the hygroscopicity parameter κ, developed by Petters & Kreidenweis (2007). We retrieve κ = 0.17±0.03 and 0.06±0.01 for the early Earth and Titan analogs, respectively. This early Earth analog hygroscopicity value indicates that the aerosol could activate at reasonable water vapor supersaturations. We use previous aerosol mass spectrometry results to correlate the chemical structure of the two types of analog with their hygroscopicity. The hygroscopicity of the early Earth aerosol analog, coupled with the apparent lack of other good CCN during the Archean, helps explain the role of the organic haze in the indirect effect of clouds on the early Earth and indicates that it may have had a significant impact on the hydrological cycle.

Development of absorbing aerosol index simulator based on TM5-M7

NASA Astrophysics Data System (ADS)

Sun, Jiyunting; van Velthoven, Peter; Veefkind, Pepijn

2017-04-01

Aerosols alter the Earth's radiation budget directly by scattering and absorbing solar and thermal radiation, or indirectly by perturbing clouds formation and lifetime. These mechanisms offset the positive radiative forcing ascribed to greenhouse gases. In particular, absorbing aerosols such as black carbon and dust strongly enhance global warming. To quantify the impact of absorbing aerosol on global radiative forcing is challenging. In spite of wide spatial and temporal coverage space-borne instruments (we will use the Ozone Monitoring Instrument, OMI) are unable to derive complete information on aerosol distribution, composition, etc. The retrieval of aerosol optical properties also partly depends on additional information derived from other measurements or global atmospheric chemistry models. Common quantities of great interest presenting the amount of absorbing aerosol are AAOD (absorbing aerosol optical depth), the extinction due to absorption of aerosols under cloud free conditions; and AAI (absorbing aerosol index), a measure of aerosol absorption more directly derivable from UV band observations than AAOD. When comparing model simulations and satellite observations, resemblance is good in terms of the spatial distribution of both parameters. However, the quantitative discrepancy is considerable, indicating possible underestimates of simulated AAI by a factor of 2 to 3. Our research, hence, has started by evaluating to what extent aerosol models, such as our TM5-M7 model, represent the satellite measurements and by identifying the reasons for discrepancies. As a next step a transparent methodology for the comparison between model simulations and satellite observations is under development in the form of an AAI simulator based on TM5-M7.

Implications of MODIS impression of aerosol loading over urban and rural settlements in Nigeria: Possible links to energy consumption patterns in the country

NASA Astrophysics Data System (ADS)

Dom Onyeuwaoma, Nnaemeka

2016-07-01

A study of aerosol loading patterns in some selected cities in Nigeria was carried out using MODIS, TOMS/OMI AND AIRS satellite imageries for a period of 10 years. The results showed that an aerosol optical depth (AOD) loading obtained ranged from 0.02-0.9, UV aerosol index (AI) and carbon monoxide (CO) results ranged from 1.32- 2.43 and 2.22-2.6 molecule/cm2, respectively. The CO data was used to infer the presence of carbonecous aerosols from biomass, fossil combustion and industrial activities. This result indicates that areas with higher AOD and AI do not correspond in high CO loading. From the HYSPLIT and HAT analysis conducted it showed that advection plays important role in the dispersion of aerosols. This implies that aerosols can reside in a place remote from where they are generated. Also, the high concentration of CO aerosol in the southern cities suggests a high rate of industrial pollution as a result of fossil fuel burning, vehicular emissions, high population density and gas flaring. Therefore, emphasis should be on the need to switch to renewable energy options as an alternative to fossil fuel. Furthermore, plans for mitigations should not be limited to industrialized cities only but extended to other cities which might be bearing the real brunt of industrial emissions as shown in this work.

The Formation of Sulfate and Elemental Sulfur Aerosols Under Varying Laboratory Conditions: Implications for Early Earth

NASA Technical Reports Server (NTRS)

DeWitt, H. Langley; Hasenkopf, Christa A.; Trainer, Melissa G.; Farmer, Delphine K.; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A.

2010-01-01

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 x 10(exp 9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO2) by UV light with lambda < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are elemental sulfur (S8) and sulfuric acid (H2S04) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO2 either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H2) or methane (CH4), increased the formation of S8. With UV photolysis, formation of S8 aerosols is highly dependent on the initial SO2 pressure; and S8 is only formed at a 2% SO2 mixing ratio and greater in the absence of a reductant, and at a 0.2% SO2 mixing ratio and greater in the presence of 1000 ppmv CH4. We also found that organosulfur compounds are formed from the photolysis of CH4 and moderate amounts of SO2, The implications for sulfur aerosols on early Earth are discussed.

Airborne remote sensing of ultraviolet-absorbing aerosols during the NASA ATom, SEAC4RS and DC3 campaigns

NASA Astrophysics Data System (ADS)

Hall, S. R.; Ullmann, K.; Commane, R.; Crounse, J. D.; Daube, B. C.; Diskin, G. S.; Dollner, M.; Froyd, K. D.; Katich, J. M.; Kim, M. J.; Madronich, S.; Murphy, D. M.; Podolske, J. R.; Schwarz, J. P.; Teng, A.; Weber, R. J.; Weinzierl, B.; Wennberg, P. O.; Sachse, G.; Wofsy, S.

2017-12-01

Spectrally resolved up and down-welling actinic flux was measured from the NASA DC-8 aircraft by the Charged-coupled device Actinic Flux Spectroradiometers (CAFS) during recent campaigns including ATom, DC3 and SEAC4RS. The primary purpose is retrieval of 40 photolysis frequencies to complement the in situ chemistry. However, the spectra also provide the opportunity to examine absorption trends in the UV where few other measurements exist. In particular, absorption by brown (BrC) and black (BC) carbon aerosols result in characteristic UV signatures. A new technique exploits the spectral changes to detect the presence of these aerosols for qualitative, real-time, remote sensing of biomass burning (BB). The data may prove useful for examination of the evolution of BrC, including chemical processing and hygroscopic growth. The induced UV changes also feed back to the photolysis frequencies affecting the chemistry. Further work will determine the robustness of the technique and if quantitative spectral absorption retrievals are possible.

An Expanded UV Irradiance Database from TOMS Including the Effects of Ozone, Clouds, and Aerosol Attenuation

NASA Technical Reports Server (NTRS)

Herman, J.; Krotkov, N.

2003-01-01

The TOMS UV irradiance database (1978 to 2003) has been expanded to include five new products (noon irradiance at 305,310,324, and 380 nm, and noon erythemal-weighted irradiance), in addition to the existing erythemal daily exposure, that permit direct comparisons with ground-based measurements from spectrometers and broadband instruments. The new data are available on http://toms.gsfc.nasa.gov/>http://toms.gsfc.nasa.gov. Comparisons of the TOMS estimated irradiances with ground-based instruments are given along with a review of the sources of known errors, especially the recent improvements in accounting for aerosol attenuation. Trend estimations from the new TOMS irradiances permit the clear separation of changes caused by ozone and those caused by aerosols and clouds. Systematic differences in cloud cover are shown to be the most important factor in determining regional differences in UV radiation reaching the ground for locations at the same latitude (e.g., the summertime differences between Australia and the US southwest).

Aerosol Absorption Measurements in MILAGRO.

NASA Astrophysics Data System (ADS)

Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

2007-12-01

During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.

Unique airborne measurements at the tropopause of Fukushima Xe-133, aerosol, and aerosol precursors indicate aerosol formation via homogeneous and cosmic ray induced nucleation

NASA Astrophysics Data System (ADS)

Schlager, Hans; Arnold, Frank; Aufmhoff, Heinfried; Minikin, Andreas; Baumann, Robert; Simgen, Hardy; Lindemann, Stefan; Rauch, Ludwig; Kaether, Frank; Pirjola, Liisa; Schumann, Ulrich

2014-05-01

We report unique airborne measurements, at the tropopause, of the Fukushima radio nuclide Xe-133, aerosol particles (size, shape, number concentration, volatility), aerosol precursor gases (particularly SO2, HNO3, H2O). Our measurements and accompanying model simulations indicate homogeneous and cosmic ray induced aerosol formation at the tropopause. Using an extremely sensitive detection method, we managed to detect Fukushima Xe-133, an ideal transport tracer, at and even above the tropopause. To our knowledge, these airborne Xe-133 measurements are the only of their kind. Our investigations represent a striking example how a pioneering measurement of a Fukshima radio nuclide, employing an extremely sensitive method, can lead to new insights into an important atmospheric process. After the Fukushima accidential Xe-133 release (mostly during 11-15 March 2011), we have conducted two aircraft missions, which took place over Central Europe, on 23 March and 11 April 2011. In the air masses, encountered by the research aircraft on 23 March, we have detected Fukushima Xe-133 by an extremely sensitive method, at and even above the tropopause. Besides increased concentrations of Xe-133, we have detected also increased concentrations of the gases SO2, HNO3, and H2O. The Xe-133 data and accompanying transport model simulations indicate that a West-Pacific Warm Conveyor Belt (WCB) lifted East-Asian planetary boundary layer air to and even above the tropopause, followed by relatively fast quasi-horizontal advection to Europe. Along with Xe-133, anthropogenic SO2, NOx (mostly released from East-Asian ground-level combustion sources), and warer vapour were also lifted by the WCB. After the lift, SO2 and NOx experienced efficient solar UV-radiation driven conversion to the important aerosol precursors gases H2SO4 and HNO3. Our investigations indicate that, increased concentrations of the gases SO2, HNO3, and H2O promoted homogeneous and cosmic ray induced aerosol formation at and even above the tropopause.

Light absorption by secondary organic aerosol from α-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Chen; Gyawali, Madhu; Zaveri, Rahul A.

2013-10-25

It is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOAs) generated from dark α-pinene + O 3 and α-pinene + NO x + O 3 systems in the presence ofmore » neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532, and 870 nm. Significant light absorption at 355 and 405 nm was observed for the SOA formed from α-pinene + O 3 + NO 3 system only in the presence of highly acidic sulfate seed aerosols under dry conditions. In contrast, no absorption was observed when the relative humidity was elevated to greater than 27% or in the presence of neutral sulfate seed aerosols. Organic nitrates in the SOA formed in the presence of neutral sulfate seed aerosols were found to be nonabsorbing, while the light-absorbing compounds are speculated to be aldol condensation oligomers with nitroxy organosulfate groups that are formed in highly acidic sulfate aerosols. Finally and overall, these results suggest that dark α-pinene + O 3 and α-pinene + NO x + O 3 systems do not form light-absorbing SOA under typical atmospheric conditions.« less

Tropospheric Ozone Profiling Using Simulated GEO-CAPE Measurement

NASA Technical Reports Server (NTRS)

Natraj, Vijay; Li, Xiong; Kulawik, Susan; Chance, Kelly; Chatfield, Robert; Edwards, David P .; Eldering, Annmarie; Francis, Gene; Kurosu, Thomas; Pickering, Kenneth;

Features of tropospheric and stratospheric dust.

PubMed

Elterman, L; Wexler, R; Chang, D T

1969-05-01

A series of 119 profiles obtained over New Mexico comprise aerosol attenuation coefficients vs altitude to about 35 km. These profiles show the existence of several features. A surface convective dust layer extending up to about 5 km is seasonally dependent. Also, a turbidity maximum exists below the tropopause. The altitude of an aerosol maximum in the lower stratosphere is located just below that of the minimum temperature. The colder the minimum temperature, the greater is the aerosol content of the layer. This relationship suggests that the 20-km dust layer is due to convection in tropical air and advection to higher latitudes. Computed averages of optical thickness show that abatement of stratospheric dust from the Mt. Agung eruption became evident in April 1964. Results based on seventy-nine profiles characterizing volcanic dust abatement indicate that above 26 km, the aerosol scale height averages 3.75 km. Extrapolating with this scale height, tabulations are developed for uv, visible, and ir attenuation to 50 km. Optical mixing ratios are used to examine the aerosol concentrations at various altitudes, including a layer at 26 km having an optical thickness 10(-3) for 0.55-micro wavelength.

Light Absorption and Excitation-Emission Fluorescence of Urban Organic Aerosol Components and Their Relationship to Chemical Structure.

PubMed

Chen, Qingcai; Ikemori, Fumikazu; Mochida, Michihiro

2016-10-18

The present study used a combination of solvent and solid-phase extractions to fractionate organic compounds with different polarities from total suspended particulates in Nagoya, Japan, and their optical characteristics were obtained on the basis of their UV-visible absorption spectra and excitation-emission matrices (EEMs). The relationship between their optical characteristics and chemical structures was investigated based on high-resolution aerosol mass spectra (HR-AMS spectra), soft ionization mass spectra and Fourier transform infrared (FT-IR) spectra. The major light-absorption organics were less polar organic fractions, which tended to have higher mass absorption efficiencies (MAEs) and lower wavelength dependent Ångström exponents (Å) than the more polar organic fractions. Correlation analyses indicate that organic compounds with O and N atoms may contribute largely to the total light absorption and fluorescence of the organic aerosol components. The extracts from the aerosol samples were further characterized by a classification of the EEM profiles using a PARAFAC model. Different fluorescence components in the aerosol organic EEMs were associated with specific AMS ions and with different functional groups from the FT-IR analysis. These results may be useful to determine and further classify the chromophores in atmospheric organic aerosols using EEM spectroscopy.

Monitoring biological aerosols using UV fluorescence

NASA Astrophysics Data System (ADS)

Eversole, Jay D.; Roselle, Dominick; Seaver, Mark E.

1999-01-01

An apparatus has been designed and constructed to continuously monitor the number density, size, and fluorescent emission of ambient aerosol particles. The application of fluorescence to biological particles suspended in the atmosphere requires laser excitation in the UV spectral region. In this study, a Nd:YAG laser is quadrupled to provide a 266 nm wavelength to excite emission from single micrometer-sized particles in air. Fluorescent emission is used to continuously identify aerosol particles of biological origin. For calibration, biological samples of Bacillus subtilis spores and vegetative cells, Esherichia coli, Bacillus thuringiensis and Erwinia herbicola vegetative cells were prepared as suspensions in water and nebulized to produce aerosols. Detection of single aerosol particles, provides elastic scattering response as well as fluorescent emission in two spectral bands simultaneously. Our efforts have focuses on empirical characterization of the emission and scattering characteristics of various bacterial samples to determine the feasibility of optical discrimination between different cell types. Preliminary spectroscopic evidence suggest that different samples can be distinguished as separate bio-aerosol groups. In addition to controlled sample results, we will also discuss the most recent result on the effectiveness of detection outdoor releases and variations in environmental backgrounds.

Ultraviolet resources over Northern Eurasia.

PubMed

Chubarova, Natalia; Zhdanova, Yekaterina

2013-10-05

We propose a new climatology of UV resources over Northern Eurasia, which includes the assessments of both detrimental (erythema) and positive (vitamin D synthesis) effects of ultraviolet radiation on human health. The UV resources are defined by using several classes and subclasses - UV deficiency, UV optimum, and UV excess - for 6 different skin types. To better quantifying the vitamin D irradiance threshold we accounted for an open body fraction S as a function of effective air temperature. The spatial and temporal distribution of UV resources was estimated by radiative transfer (RT) modeling (8 stream DISORT RT code) with 1×1° grid and monthly resolution. For this purpose special datasets of main input geophysical parameters (total ozone content, aerosol characteristics, surface UV albedo, UV cloud modification factor) have been created over the territory of Northern Eurasia. The new approaches were used to retrieve aerosol parameters and cloud modification factor in the UV spectral region. As a result, the UV resources were obtained for clear-sky and mean cloudy conditions for different skin types. We show that the distribution of UV deficiency, UV optimum and UV excess is regulated by various geophysical parameters (mainly, total ozone, cloudiness and open body fraction) and can significantly deviate from latitudinal dependence. We also show that the UV optimum conditions can be simultaneously observed for people with different skin types (for example, for 4-5 skin types at the same time in spring over Western Europe). These UV optimum conditions for different skin types occupy a much larger territory over Europe than that over Asia. Copyright © 2013 Elsevier B.V. All rights reserved.

Fast simulation tool for ultraviolet radiation at the earth's surface

NASA Astrophysics Data System (ADS)

Engelsen, Ola; Kylling, Arve

2005-04-01

FastRT is a fast, yet accurate, UV simulation tool that computes downward surface UV doses, UV indices, and irradiances in the spectral range 290 to 400 nm with a resolution as small as 0.05 nm. It computes a full UV spectrum within a few milliseconds on a standard PC, and enables the user to convolve the spectrum with user-defined and built-in spectral response functions including the International Commission on Illumination (CIE) erythemal response function used for UV index calculations. The program accounts for the main radiative input parameters, i.e., instrumental characteristics, solar zenith angle, ozone column, aerosol loading, clouds, surface albedo, and surface altitude. FastRT is based on look-up tables of carefully selected entries of atmospheric transmittances and spherical albedos, and exploits the smoothness of these quantities with respect to atmospheric, surface, geometrical, and spectral parameters. An interactive site, http://nadir.nilu.no/~olaeng/fastrt/fastrt.html, enables the public to run the FastRT program with most input options. This page also contains updated information about FastRT and links to freely downloadable source codes and binaries.

Light-absorbing oligomer formation in secondary organic aerosol from reactive uptake of isoprene epoxydiols.

PubMed

Lin, Ying-Hsuan; Budisulistiorini, Sri Hapsari; Chu, Kevin; Siejack, Richard A; Zhang, Haofei; Riva, Matthieu; Zhang, Zhenfa; Gold, Avram; Kautzman, Kathryn E; Surratt, Jason D

2014-10-21

Secondary organic aerosol (SOA) produced from reactive uptake and multiphase chemistry of isoprene epoxydiols (IEPOX) has been found to contribute substantially (upward of 33%) to the fine organic aerosol mass over the Southeastern U.S. Brown carbon (BrC) in rural areas of this region has been linked to secondary sources in the summer when the influence of biomass burning is low. We demonstrate the formation of light-absorbing (290 < λ < 700 nm) SOA constituents from reactive uptake of trans-β-IEPOX onto preexisting sulfate aerosols as a potential source of secondary BrC. IEPOX-derived BrC generated in controlled chamber experiments under dry, acidic conditions has an average mass absorption coefficient of ∼ 300 cm(2) g(-1). Chemical analyses of SOA constituents using UV-visible spectroscopy and high-resolution mass spectrometry indicate the presence of highly unsaturated oligomeric species with molecular weights separated by mass units of 100 (C5H8O2) and 82 (C5H6O) coincident with the observations of enhanced light absorption, suggesting such oligomers as chromophores, and potentially explaining one source of humic-like substances (HULIS) ubiquitously present in atmospheric aerosol. Similar light-absorbing oligomers were identified in fine aerosol collected in the rural Southeastern U.S., supporting their atmospheric relevance and revealing a previously unrecognized source of oligomers derived from isoprene that contributes to ambient fine aerosol mass.

Satellite Detection of Smoke Aerosols Over a Snow/Ice Surface by TOMS

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Herman, Jay R.; Gleason, J. F.; Torres, O.; Seftor, C. J.

1998-01-01

The use of TOMS (Total Ozone Mapping Spectrometer) satellite data demonstrates the recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is effective over snow/ice surfaces. Instead of the traditional single wavelength (visible or infrared) method of measuring tropospheric aerosols, this method takes advantage of the wavelength dependent reduction in the backscattered radiance due to the presence of absorbing aerosols over snow/ice surfaces. An example of the resulting aerosol distribution derived from TOMS data is shown for an August 1998 event in which smoke generated by Canadian forest fires drifts over and across Greenland. As the smoke plume moved over Greenland, the TOMS observed 380 nm reflectivity over the snow/ice surface dropped drastically from 90-100% down to 30-40%. To study the effects of this smoke plume in both the UV and visible regions of the spectrum, we compared a smoke-laden spectrum taken over Greenland by the high spectral resolution (300 to 800 nm) GOME instrument with one that is aerosol-free. We also discuss the results of modeling the darkening effects of various types of absorbing aerosols over snow/ice surfaces using a radiative transfer code. Finally, we investigated the history of such events by looking at the nearly twenty year record of TOMS aerosol index measurements and found that there is a large interannual variability in the amount of smoke aerosols observed over Greenland. This information will be available for studies of radiation and transport properties in the Arctic.

TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

NASA Astrophysics Data System (ADS)

Zempila, Melina-Maria; van Geffen, Jos H. G. M.; Taylor, Michael; Fountoulakis, Ilias; Koukouli, Maria-Elissavet; van Weele, Michiel; van der A, Ronald J.; Bais, Alkiviadis; Meleti, Charikleia; Balis, Dimitrios

2017-06-01

This study aims to cross-validate ground-based and satellite-based models of three photobiological UV effective dose products: the Commission Internationale de l'Éclairage (CIE) erythemal UV, the production of vitamin D in the skin, and DNA damage, using high-temporal-resolution surface-based measurements of solar UV spectral irradiances from a synergy of instruments and models. The satellite-based Tropospheric Emission Monitoring Internet Service (TEMIS; version 1.4) UV daily dose data products were evaluated over the period 2009 to 2014 with ground-based data from a Norsk Institutt for Luftforskning (NILU)-UV multifilter radiometer located at the northern midlatitude super-site of the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki (LAP/AUTh), in Greece. For the NILU-UV effective dose rates retrieval algorithm, a neural network (NN) was trained to learn the nonlinear functional relation between NILU-UV irradiances and collocated Brewer-based photobiological effective dose products. Then the algorithm was subjected to sensitivity analysis and validation. The correlation of the NN estimates with target outputs was high (r = 0. 988 to 0.990) and with a very low bias (0.000 to 0.011 in absolute units) proving the robustness of the NN algorithm. For further evaluation of the NILU NN-derived products, retrievals of the vitamin D and DNA-damage effective doses from a collocated Yankee Environmental Systems (YES) UVB-1 pyranometer were used. For cloud-free days, differences in the derived UV doses are better than 2 % for all UV dose products, revealing the reference quality of the ground-based UV doses at Thessaloniki from the NILU-UV NN retrievals. The TEMIS UV doses used in this study are derived from ozone measurements by the SCIAMACHY/Envisat and GOME2/MetOp-A satellite instruments, over the European domain in combination with SEVIRI/Meteosat-based diurnal cycle of the cloud cover fraction per 0. 5° × 0. 5° (lat × long) grid cells. TEMIS UV doses were found to be ˜ 12.5 % higher than the NILU NN estimates but, despite the presence of a visually apparent seasonal pattern, the R2 values were found to be robustly high and equal to 0.92-0.93 for 1588 all-sky coincidences. These results significantly improve when limiting the dataset to cloud-free days with differences of 0.57 % for the erythemal doses, 1.22 % for the vitamin D doses, and 1.18 % for the DNA-damage doses, with standard deviations of the order of 11-13 %. The improvement of the comparative statistics under cloud-free cases further testifies to the importance of the appropriate consideration of the contribution of clouds in the UV radiation reaching the Earth's surface. For the urban area of Thessaloniki, with highly variable aerosol, the weakness of the implicit aerosol information introduced to the TEMIS UV dose algorithm was revealed by comparison of the datasets to aerosol optical depths at 340 nm as reported by a collocated CIMEL sun photometer, operating in Thessaloniki at LAP/AUTh as part of the NASA Aerosol Robotic Network.

Analysis of dust and marine aerosol optical depth spectral-curvature information in the UV to SWIR (Short Wave Infrared) wavelength regions.

NASA Astrophysics Data System (ADS)

O'Neill, N. T.; Smirnov, A.; Eck, T. F.; Sakerin, S.; Kabanov, D.

2005-12-01

Traditional sunphotometry in the UV, visible and very NIR (Near Infrared) spectral regions is weighted, in terms of spectral information content, towards sub-micron (fine mode) particles. Sunphotometry in the NIR and SWIR increases the diversity and information content of spectral aerosol optical depth (AOD) measurements for supermicron (coarse mode) particles. Two data sets representing dust aerosols from the UAE (United Arab Emirates) region and marine aerosols from the northern, tropical and southern Atlantic Ocean were analyzed in terms of their spectral curvature diversity and information content. The former data set was acquired using NIR-enhanced CIMEL sunphotometers (340, 340, 380, 440, 500, 670, 870, 1020, 1640 nm) as part of the August to October, 2004 UAE2 field campaign while the latter data set was acquired using an automated Russian UV to SWIR SP-5 sunphotometer (339, 423, 438, 484, 552, 633, 677, 777, 869, 1241, 1560, 2148, 4000 nm) as part of a October/December 2004 cruise campaign in the northern, tropical and south Atlantic Ocean. A Microtops hand-held sunphotometer was also employed to acquire VIS to NIR AOD spectra during the latter field campaign. Results will be presented in terms of robust micro-physical and spectral curvature parameters which characterize super-micron aerosols and, in a more general sense, in terms of what universal/fundamental optical inferences can be drawn from the two disperse data sets.

DSCOVR_EPIC_L2_O3SO2AI_01

Atmospheric Science Data Center

2018-06-29

... dioxide (SO2) from volcanic plumes, scene reflectivity, and aerosol index (AI), retrieved from the ultraviolet (UV) measurements of DSCOVR ... Access:   Order Data Parameters:  Aerosol Index (AI) Reflectivity at 340 nm Vertical Column of Ozone (O3) ...

Observations of fluorescent aerosol-cloud interactions in the free troposphere at the Sphinx high Alpine research station, Jungfraujoch

NASA Astrophysics Data System (ADS)

Crawford, I.; Lloyd, G.; Bower, K. N.; Connolly, P. J.; Flynn, M. J.; Kaye, P. H.; Choularton, T. W.; Gallagher, M. W.

2015-09-01

The fluorescent nature of aerosol at a high Alpine site was studied using a wide-band integrated bioaerosol (WIBS-4) single particle multi-channel ultra violet-light induced fluorescence (UV-LIF) spectrometer. This was supported by comprehensive cloud microphysics and meteorological measurements with the aims of cataloguing concentrations of bio-fluorescent aerosols at this high altitude site and also investigating possible influences of UV-fluorescent particle types on cloud-aerosol processes. Analysis of background free tropospheric air masses, using a total aerosol inlet, showed there to be a minor but statistically insignificant increase in the fluorescent aerosol fraction during in-cloud cases compared to out of cloud cases. The size dependence of the fluorescent aerosol fraction showed the larger aerosol to be more likely to be fluorescent with 80 % of 10 μm particles being fluorescent. Whilst the fluorescent particles were in the minority (NFl/NAll = 0.27±0.19), a new hierarchical agglomerative cluster analysis approach, Crawford et al. (2015) revealed the majority of the fluorescent aerosol were likely to be representative of fluorescent mineral dust. A minor episodic contribution from a cluster likely to be representative of primary biological aerosol particles (PBAP) was also observed with a wintertime baseline concentration of 0.1±0.4 L-1. Given the low concentration of this cluster and the typically low ice active fraction of studied PBAP (e.g. pseudomonas syringae) we suggest that the contribution to the observed ice crystal concentration at this location is not significant during the wintertime.

Biomass Burning Dominates Brown Carbon Absorption in the Rural Southeastern U.S.

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Attwood, A. R.; Brock, C. A.; Brown, S. S.; Guo, H.; Weber, R. J. J.; Xu, L.; Ng, N. L.; Stone, E. A.; Edgerton, E. S.; Baumann, K.; Hu, W.; Palm, B. B.; Jimenez, J. L.; Fry, J.; Ayres, B. R.; Draper, D.; Allen, H.

2014-12-01

Aerosol scattering and absorption are still among the largest uncertainties in quantifying radiative forcing. Brown carbon has a wavelength-dependent absorption that increases in the UV spectral region, and its major atmospheric sources include biomass burning, anthropogenic combustion of fossil fuels, and secondary organic aerosol. The rural Southeastern U.S. is influenced by high isoprene concentrations and varying concentrations of biomass burning aerosol, making it an ideal place to compare the relative contributions of these two sources to the brown carbon absorption budget. During the Southern Oxidant and Aerosol Study in summer 2013, we deployed a new field instrument that uses cavity enhanced spectroscopy with a broadband light source to measure aerosol optical extinction as a function of wavelength. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We combine these data with direct absorption measurements of water-soluble organic carbon obtained from a novel UV/VIS-WSOC instrument, and with aerosol composition measurements. We examine these data sets to determine: 1) the optical closure between measured dry aerosol extinction and values calculated from aerosol composition and size distribution; 2) the magnitude of brown and black carbon absorption; 3) the relative contributions of biomass burning, anthropogenic, and secondary organic aerosol contributions to brown carbon absorption in the Southeast U.S. during the summer. We conclude that biomass burning is a major contributor to optical absorption by organic aerosol in the rural southeastern U.S.

Optical, Physical and Chemical Properties of Tar Balls Observed During the Yosemite Aerosol Characterization Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hand, Jenny L.; Malm, W. C.; Laskin, Alexander

2005-11-09

The Yosemite Aerosol Characterization Study of summer 2002 (YACS) occurred during an active fire season in the western U. S., and provided an opportunity to investigate many unresolved issues related to the radiative effects of biomass burning aerosols. Single particle analysis was performed on field collected aerosol samples using an array of electron microscopy techniques. Amorphous carbon spheres, or “tar balls”, were present in samples collected during episodes of high particle light scattering coefficients that occurred during the peak of a smoke/haze event. The highest concentrations of light-absorbing carbon from a dual-wavelength aethalometer (λ = 370 and 880 nm) occurredmore » during periods when the particles were predominantly tar balls, indicating they do absorb light in the UV and near-IR range of the solar spectrum. Closure experiments of mass concentrations and light scattering coefficients during periods dominated by tar balls did not require any distinct assumptions of organic carbon molecular weight correction factors, density, or refractive index compared to periods dominated by other types of organic carbon aerosols. Measurements of the hygroscopic behavior of tar balls using an environmental SEM indicate that tar balls do not exhibit deliquescence, but do uptake some water at high (~83 %) relative humidity. The ability of tar balls to efficiently scatter and absorb light, and to absorb water has important implications for their role in regional haze and climate fence.« less

[Study on transformation mechanism of SOA from biogenic VOC under UV-B condition].

PubMed

Li, Ying-Ying; Li, Xiang; Chen, Jian-Min

2011-12-01

A laboratory study was carried out to investigate the biogenic volatile organic compounds (BVOC) in a lab-made glass chamber. The secondary organic aerosol (SOA) products can be detected under the UV photooxidation of BVOC. Pelargonium x Citrenella was chosen as the target plant in this research because it can release a large amount of BVOCs. The predominant 7 alkene and ketol compounds were detected by using solid phase microextraction (SPME) sampling and gas chromatography/mass spectrometry (GC/MS) analysis. The photochemical experiment indicated that these BVOC can be rapidly oxidized into SOA under UV-B irradiation. A tandem differential mobility analyzer (TDMA) was used to measure the size distribution and the hygroscopicity of the SOA. The particle diameter was in the range of 50 nm to 320 nm. The high hygroscopicity of SOA was also obtained and the size increased from 1.05 to 1.11 during the wet experiment.

Observations of fluorescent and biological aerosol at a high-altitude site in Central France

NASA Astrophysics Data System (ADS)

Gabey, A. M.; Vaitilingom, M.; Freney, E.; Boulon, J.; Sellegri, K.; Gallagher, M. W.; Crawford, I. P.; Robinson, N. H.; Stanley, W. R.; Kaye, P. H.

2013-01-01

Total bacteria, fungal spore and yeast counts were compared with UV Light-Induced Fluorescence (UV-LIF) measurements of ambient aerosol at the summit of the Puy de Dôme (pdD) mountain in Central France (1465 m a.s.l), which represents a background elevated site. Bacteria, fungal spores and yeast were enumerated by epifluorescence microscopy (EFM) and found to number 2.2 to 23 L-1 and 0.8 to 2 L-1, respectively. Bacteria counts on two successive nights were an order of magnitude larger than in the intervening day. A Wide Issue Bioaerosol Spectrometer, version 3 (WIBS-3) was used to perform UV-LIF measurements on ambient aerosol sized 0.8 to 20 μm. Mean total number concentration was 270 L-1 (σ = 66 L-1) found predominantly in a size mode at 2 μm for most of the campaign. Total concentration (fluorescent + non-fluorescent aerosol) peaked at 500 L-1 with a size mode at 1 μm because of a change in air mass origin lasting around 48 h. The WIBS-3 features two excitation and fluorescence detection wavelengths corresponding to different biological molecules. The mean fluorescent particle concentration after short-wave (280 nm; Tryptophan) excitation was 12 L-1 (σ = 6 L-1), and did not vary much through the campaign. In contrast the mean concentration of particles fluorescent after long-wave (370 nm; NADH) excitation was 95 L-1 (σ = 25 L-1), and a nightly rise and subsequent fall of up to 100 L-1 formed a strong diurnal cycle in the latter. The fluorescent populations exhibited size modes at 3 μm and 2 to 3 μm, respectively. A hierarchical agglomerative cluster analysis algorithm was applied to the data and used to extract different particle factors. A cluster concentration time series representative of bacteria was identified. This was found to exhibit a diurnal cycle with a maximum peak appearing during the day. Analysis of organic mass spectra recorded using an Aerosol Mass Spectrometer (AMS; Aerodyne Inc.) suggests that aerosol reaching the site at night was more aged than that during the day, indicative of sampling the residual layer at night. Supplementary meteorological data and previous work also show that pdD lies in the residual layer/free troposphere at night, and this is thought to cause the observed diurnal cycles in organic-type and fluorescent aerosol particles. Based on the observed disparity between bacteria and fluorescent particle concentrations, fluorescent non-PBA is likely to be important in the WIBS-3 data and the surprisingly high fluorescent concentration in the residual layer/free troposphere raises questions about a ubiquitous background in continental air during the summer.

OCAPI: a multidirectional multichannel polarizing imager

NASA Astrophysics Data System (ADS)

Le Naour, C.; Eichen, G.; Léon, J. F.

2017-11-01

OCAPI (Optical Carbonaceous and anthropogenic Aerosols Pathfinder Instrument) is an imager dedicated to the observation of the spectral, directional and polarized signatures of the solar radiance reflected by the Earth-Atmosphere system. The measurements are used to study air quality and pollution by tracking aerosol quantity, types and circulation at various scales in the visible range. The main characteristics of OCAPI are a 110° along track and cross track field of view, eight polarized channels distributed between 320 and 2130 nm. The resolution is 4 x 4 km2 in the visible and the shortwave infrared (SWIR) range, and 10 x 10 km2 in the UV. The instrumental concept is derived from POLDER and PARASOL with additional channels in the UV and SWIR to better determine aerosol properties and constrain Earth surface and cloud contributions in the detected signal. It is based on three wide field-ofview telecentric optics (UV, Visible and SWIR), a rotating wheel bearing spectral and polarized filters and two dimensional detector arrays at the focal plane of the optics. The instrument requirements, concept and budgets are presented.

Light absorption of secondary organic aerosol: Composition and contribution of nitro-aromatic compounds

EPA Science Inventory

Secondary organic aerosol (SOA) might affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collect...

A new parameterization of the UV irradiance altitude dependence for clear-sky conditions and its application in the on-line UV tool over Northern Eurasia

NASA Astrophysics Data System (ADS)

Chubarova, Nataly; Zhdanova, Yekaterina; Nezval, Yelena

2016-09-01

A new method for calculating the altitude UV dependence is proposed for different types of biologically active UV radiation (erythemally weighted, vitamin-D-weighted and cataract-weighted types). We show that for the specified groups of parameters the altitude UV amplification (AUV) can be presented as a composite of independent contributions of UV amplification from different factors within a wide range of their changes with mean uncertainty of 1 % and standard deviation of 3 % compared with the exact model simulations with the same input parameters. The parameterization takes into account for the altitude dependence of molecular number density, ozone content, aerosol and spatial surface albedo. We also provide generalized altitude dependencies of the parameters for evaluating the AUV. The resulting comparison of the altitude UV effects using the proposed method shows a good agreement with the accurate 8-stream DISORT model simulations with correlation coefficient r > 0.996. A satisfactory agreement was also obtained with the experimental UV data in mountain regions. Using this parameterization we analyzed the role of different geophysical parameters in UV variations with altitude. The decrease in molecular number density, especially at high altitudes, and the increase in surface albedo play the most significant role in the UV growth. Typical aerosol and ozone altitude UV effects do not exceed 10-20 %. Using the proposed parameterization implemented in the on-line UV tool (http://momsu.ru/uv/) for Northern Eurasia over the PEEX domain we analyzed the altitude UV increase and its possible effects on human health considering different skin types and various open body fraction for January and April conditions in the Alpine region.

Airborne Lidar measurements of aerosols, mixed layer heights, and ozone during the 1980 PEPE/NEROS summer field experiment

NASA Technical Reports Server (NTRS)

Browell, E. V.; Shipley, S. T.; Butler, C. F.; Ismail, S.

1985-01-01

A detailed summary of the NASA Ultraviolet Differential Absorption Lidar (UV DIAL) data archive obtained during the EPA Persistent Elevated Pollution Episode/Northeast Regional Oxidant Study (PEPE/NEROS) Summer Field Experiment Program (July through August 1980) is presented. The UV dial data set consists of remote measurements of mixed layer heights, aerosol backscatter cross sections, and sequential ozone profiles taken during 14 long-range flights onboard the NASA Wallops Flight Center Electra aircraft. These data are presented in graphic and tabular form, and they have been submitted to the PEPE/NEROS data archive on digital magnetic tape. The derivation of mixing heights and ozone profiles from UV Dial signals is discussed, and detailed intercomparisons with measurements obtained by in situ sensors are presented.

UV 380 nm reflectivity of the Earth's surface, clouds and aerosols

NASA Astrophysics Data System (ADS)

Herman, J. R.; Celarier, E.; Larko, D.

2001-03-01

The 380 nm radiance measurements of the Total Ozone Mapping Spectrometer (TOMS) have been converted into a global data set of daily (1979-1992) Lambert equivalent reflectivities R of the Earth's surface and boundary layer (clouds, aerosols, surface haze, and snow/ice) and then corrected to RPC for the presence of partly clouded scenes. Since UV surface reflectivity is between 2 and 8% for both land and water during all seasons of the year (except for ice and snow cover), reflectivities larger than the surface value indicate the presence of clouds, haze, or aerosols in the satellite field of view. A statistical analysis of 14 years of daily reflectivity data shows that most snow-/ice-free scenes observed by TOMS have a reflectivity less than 10% for the majority of days during a year. The 380 nm reflectivity data show that the true surface reflectivity is 2-3% lower than the most frequently occurring reflectivity value for each TOMS scene as seen from space. Most likely the cause is a combination of frequently occurring boundary layer water and/or aerosol haze. For most regions the observation of extremely clear conditions needed to estimate the surface reflectivity from space is a comparatively rare occurrence. Certain areas (e.g., Australia, southern Africa, portions of northern Africa) are cloud-free more than 80% of the year, which exposes these regions to larger amounts of UV radiation than at comparable latitudes in the Northern Hemisphere. Regions over rain forests, jungle areas, Europe and Russia, the bands surrounding the Arctic and Antarctic regions, and many ocean areas have significant cloud cover (R>15%) more than half of each year. In the low to middle latitudes the areas with the heaviest cloud cover (highest reflectivity for most of the year) are the forest areas of northern South America, southern Central America, the jungle areas of equatorial Africa, and high mountain regions such as the Himalayas or the Andes. The TOMS reflectivity data show both the presence of large nearly clear ocean areas and the effects of the major ocean currents on cloud production.

Light-Absorbing Brown Carbon Aerosol Constituents from Combustion of Indonesian Peat and Biomass.

PubMed

Budisulistiorini, Sri Hapsari; Riva, Matthieu; Williams, Michael; Chen, Jing; Itoh, Masayuki; Surratt, Jason D; Kuwata, Mikinori

2017-04-18

Light-absorbing brown carbon (BrC) constituents of organic aerosol (OA) have been shown to significantly absorb ultraviolet (UV) and visible light and thus impact radiative forcing. However, molecular identification of the BrC constituents is still limited. In this study, we characterize BrC constituents at the molecular level in (i) aerosols emitted by combustion of peat, fern/leaf, and charcoal from Indonesia and (ii) ambient aerosols collected in Singapore during the 2015 haze episode. Aerosols were analyzed using ultra performance liquid chromatography instrument interfaced to a diode array detector and electrospray ionization high-resolution quadrupole time-of-flight mass spectrometer operated in the negative ion mode. In the laboratory-generated aerosols, we identified 41 compounds that can potentially absorb near-UV and visible wavelengths, such as oxygenated-conjugated compounds, nitroaromatics, and S-containing compounds. The sum of BrC constituents in peat, fern/leaf, and charcoal burning aerosols are 16%, 35%, and 28% of the OA mass, respectively, giving an average contribution of 24%. On average, the BrC constituents account for 0.4% of the ambient OA mass; however, large uncertainties in mass closure remain because of the lack of authentic standards. This study highlights the potential of light-absorbing BrC OA constituents from peat, fern/leaf, and charcoal burning and their importance in the atmosphere.

Global Assessment of OMI Aerosol Single-scattering Albedo Using Ground-based AERONET and SKYNET Inversions

NASA Technical Reports Server (NTRS)

Jethva, Hiren; Torres, Omar; Ahn, Changwoo

2014-01-01

We compare the aerosol single-scattering albedo (SSA) retrieved by the near-UV two-channel algorithm (OMAERUV) applied to the Aura-Ozone Monitoring Instrument (OMI) measurements with an equivalent inversion made by the ground-based Aerosol Robotic Network (AERONET). This work is the first comprehensive effort to globally compare the OMI-retrieved SSA with that of AERONET using all available sites spanning the regions of biomass burning, dust, and urban pollution. An analysis of the co-located retrievals over 269 sites reveals that about 46 percent (69 percent) of OMI-AERONET matchups agree within the absolute difference of plus or minus 0.03 (plus or minus 0.05) for all aerosol types. The comparison improves to 52 percent (77 percent) when only 'smoke' and 'dust' aerosol types were identified by the OMAERUV algorithm. Regionally, the agreement between the two inversions was robust over the biomass burning sites of South America, Sahel, Indian subcontinent, and oceanic-coastal sites followed by a reasonable agreement over north-east Asia. Over the desert regions, OMI tends to retrieve higher SSA, particularly over the Arabian Peninsula. Globally, the OMI-AERONET matchups agree mostly within plus or minus 0.03 for the aerosol optical depth (440 nanometers) and UV-aerosol index larger than 0.4 and 1.0, respectively. We also compare the OMAERUV SSA against the inversion made by an independent network of ground-based radiometer called SKYNET with its operating sites in Japan, China, South-East Asia, India, and Europe. The advantage of the SKYNET database over AERONET is that it performs retrieval at near-UV wavelengths which facilitate the direct comparison of OMI retrievals with the equivalent ground-based inversion. Comparison of OMI and SKYNET over currently available sites reveals a good agreement between the two where more than 70 percent of matchups agree within the absolute difference of 0.05.

Data Continuity of Aerosol Index from Suomi NPP/OMPS Observations

NASA Astrophysics Data System (ADS)

Ahn, C.; Torres, O.; Tiruchirapalli, R.; Taylor, S.; Jethva, H. T.

2017-12-01

Since the development of the Aerosol Index (AI) concept from Nimubs-7 TOMS near-UV measurements, the AI product has been widely used by the aerosol community in a variety of applications including monitoring of the sources and sinks of carbonaceous and desert dust aerosols. The AI uses a pair of near-UV radiances to detect the presence of absorbing particles even over bright backgrounds such as clouds and snow/ice covered areas. Since its inception in the mid 90's, the AI has been available as a by-product of the total ozone product. Due to the implementation of a new total ozone algorithm, the standard AI product will no longer be available starting in 2018. To assure the continuity of the AI record, we have developed an improved AI algorithm that uses a better forward modeling method of the top of atmosphere radiances. The enhanced modelling capability accounts for the scattering of clouds using Mie theory, and includes the effect of wavelength and angle dependent surface reflectance effects. By doing this, we have significantly reduced angular dependent false AI signals such as sun glint over the ocean. We will discuss the improved AI algorithm and present the long term AI record from various UV space borne sensors including TOMS, OMI, OMPS, and EPIC with consistent AI algorithms, followed by future plans for near-real time processing and operational production of a new OMPS AI product.

Solar UV dose patterns in Italy.

PubMed

Meloni, D; Casale, G R; Siani, A M; Palmieri, S; Cappellani, F

2000-06-01

Since 1992 solar ultraviolet (UV) spectral irradiance (290-325 nm) has been measured at two Italian stations of Rome (urban site) and Ispra (semirural site) using Brewer spectrophotometry. The data collected under all sky conditions, are compared with the output of a sophisticated radiative transfer model (System for Transfer of Atmospheric Radiation--STAR model). The STAR multiple scattering scheme is able to cope with all physical processes relevant to the UV transfer through the atmosphere. The experience so far acquired indicates that, in spite of the unavoidable uncertainties in the input parameters (ozone, aerosol, surface albedo, pressure, temperature, relative humidity, cloud cover), measured and computed clear sky iradiances are in reasonable agreement. The STAR model is applied to build up the solar UV geographic patterns in Italy: the daily dose in the range 290-325 nm is computed at about 70 sites where a thorough and homogeneous climatology is available. For each month the concept of an idealized "standard day" is introduced and the surface distribution of solar UV field determined. The map of solar UV patterns for Italy, available for the first time, meets the study requirements in the field of skin and eye epidemiology, as well as in other investigations dealing with the impact of UV on the biosphere. The results are interpreted in terms of atmospheric and meteorological parameters modulating UV radiation reaching the ground.

DISCOVER-AQ: An Overview and Initial Comparisons of NO2 with OMI Observations

NASA Technical Reports Server (NTRS)

Pickering, Kenneth; Crawford, James; Krotkov, Nickolay; Bucsela, Eric; Lamsal, Lok; Celarier, Edward; Herman, Jay; Janz, Scott; Cohen, Ron; Weinheimer, Andrew

2011-01-01

The first deployment of the Earth Venture -1 DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) project was conducted during July 2011 in the Baltimore-Washington region. Two aircraft (a P-3B for in-situ sampling and a King Air for remote sensing) were used along with an extensive array of surface-based in-situ and remote sensing instrumentation. Fourteen flight days were accomplished by both aircraft and over 250 profiles of trace gases and aerosols were performed by the P-3B over surface air quality monitoring stations, which were specially outfitted with sunphotometers and Pandora UV/Vis spectrometers. The King Air flew with the High Spectral Resolution Lidar for aerosols and the ACAM UV/Vis spectrometer for trace gases. This suite of observations allows linkage of surface air quality with the vertical distributions of gases and aerosols, with remotely-sensed column amounts observed from the surface and from the King Air, and with satellite observations from Aura (OMI and TES), GOME-2, MODIS and GOES. The DISCOVER-AQ data will allow determination of under what conditions satellite retrievals are indicative of surface air quality, and they will be useful in planning new satellites. In addition to an overview of the project, a preliminary comparison of tropospheric column NO2 densities from the integration of in-situ P-3B observations, from the Pandoras and ACAM, and from the new Goddard OMI NO2 algorithm will be presented.

How do environmental and behavioral factors impact ultraviolet radiation effects on health: the RISC-UV Project

NASA Astrophysics Data System (ADS)

Correa, M. P.; Godin-Beekmann, S.; Haeffelin, M.; Saiag, P.; Mahe, E.; Brogniez, C.; Dupont, J. C.; Pazmiño, A.; Auriol, F.; Bonnel, B.

2009-04-01

Introduction: RISC-UV is a research project on "Impact of climate change on ultraviolet radiation and risks for health", a research project in which physicists, meteorologists and physicians work together to assess the relative role played by environmental and behavioral factors in the UV-related diseases as skin cancer and vitamin D deficiency. Environmental factors are related to the role played by the alteration in intensity of UV radiation at the Earth's surface resulting from variation in several factors affected by climate change and human activities: stratospheric ozone, cloud cover, aerosols and the reflectivity of the surface. On the other hand, behavioral factors are related to the sun over/underexposure and the correct use of sun-protection (hats, caps, sunglasses, sunscreen lotion, etc.). RISC-UV is organized around three main areas: 1) Organization of a workshop, scheduled for January 2009, which aims to describe the state of the art in the subject within each community and define the requirements of pathologists for epidemiological studies; 2) A pilot study intended to evaluate the consistency between UV measurements delivered simultaneously by satellite-based instruments, ground instruments, radiometers and individual dosimeters. This study is based on measurements campaigns and an analysis of the long-term consistency of data series relating to UV radiation and associated parameters; and 3) Analysis of the weights of medical, behavioral and environmental parameters involved in skin carcinogenesis. A detailed description of these areas can be found in http://www.gisclimat.fr/Doc/GB/D_projects/RISC-UV_GB.html. This presentation focuses on the first results of the UV experimental measurements performed between September 8th and October 8th 2008 in Palaiseau, France (48.7˚ N; 2.2˚ E; 170m - Haeffelin et al., 2005). A second campaign is foreseen for the spring of 2009. The purpose of these campaigns is to obtain, analyze and quantitatively link the UV radiation data obtained at various spatial scales (satellite, ground-based and spot measurements) by a variety of measuring systems. Moreover a set of atmospheric parameters (total ozone column, the vertical profile and optical thickness of aerosols, cloud cover and solar albedo) related to UV radiation is also collected. Material: The instrumental set consisted of several instruments for: 1) UV radiation measurements (a spectroradiometer, UV-A, UV-B, Erythemal UV and broadband solar pyranometers); 2) cloud, ozone and aerosol observations (photometer, Lidar and radiometers); and 3) personal monitors for UV index measurements, as handhelds, watches and mini-station. Results: Measurements performed in cloudy and sunny days around noon local time (± 1h) showed mean values of 3.3 ± 1.0 UVI, and the maximum UVI was 5.5 at noon on a clear sky day (September 14). The influence of cirrus clouds and aerosols radiation attenuation is currently studied on several case studies. From the mean UVI values, we estimated the time of necessary exposure for the induction of erythema of the skin and for the synthesis 1000 UI of vitamin D per day (1000 UI). (McKenzie et al., 2008). Preliminary results show that around solar noon (between 9 and 12 UTC that is 11 and 14 local time), on the one hand, about 45 min of exposure is required to cause skin redness and consequently lead to harmful effects on the human health. On the other hand, this exposure can be insufficient to lead to beneficial effects if we consider only the generally exposed parts of the body, as the hands and the face. It is only in the extreme conditions - exposure of the whole body - that the synthesis of the vitamin D can be done in 10 to 20 minutes. Otherwise an exposure during several hours is necessary. These results are particularly interesting with respect to possible problems of lack of vitamin D in the French population, mainly rickets (children) and osteosporosis (old persons), as well as other diseases related to the lack of vitamin D (Holick, 2004). A second campaign will be carried out during Spring 2009. This campaign will mainly focus on: 1) the comparisons of satellite retrievals and ground-based UV observations in order to relate different scales of UV measurements. Surface measurements will be performed in ten different sites located in the city of Paris and its suburbs; 2) the analysis of UV measurements in tilted surfaces using four pyranometers installed in different angles (horizontal, 45˚ , 90˚ and 180˚ ) ; 3) the measurements of surface albedo; and 4) the evaluation of cirrus and aerosol impact on UV radiation at the surface using collocated measurements like Lidar and Sunphotometers. Acknowledgments: SIRTA team. References: M. Haeffelin et al. SIRTA, a ground-based atmospheric observatory for cloud and aerosol research. Ann. Geophys., 23, 253-275, 2005 Holick, MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr 2004;79:362-71. Mc Kenzie, R; JB Liley; L.O Björn. UV Radiation: Balancing Risks and Benefits. Photochemistry and Photobiology, 2008.

Aromatic Structure in Simulates Titan Aerosol

NASA Technical Reports Server (NTRS)

Trainer, Melissa G.; Loeffler, M. J.; Anderson, C. M.; Hudson, R. L.; Samuelson, R. E.; Moore, M. A.

2011-01-01

Observations of Titan by the Cassini Composite Infrared Spectrometer (CIRS) between 560 and 20 per centimeter (approximately 18 to 500 micrometers) have been used to infer the vertical variations of Titan's ice abundances, as well as those of the aerosol from the surface to an altitude of 300 km [1]. The aerosol has a broad emission feature centered approximately at 140 per centimeter (71 micrometers). As seen in Figure 1, this feature cannot be reproduced using currently available optical constants from laboratory-generated Titan aerosol analogs [2]. The far-IR is uniquely qualified for investigating low-energy vibrational motions within the lattice structures of COITIDlex aerosol. The feature observed by CIRS is broad, and does not likely arise from individual molecules, but rather is representative of the skeletal movements of macromolecules. Since Cassini's arrival at Titan, benzene (C6H6) has been detected in the atmosphere at ppm levels as well as ions that may be polycyclic aromatic hydrocarbons (PAHs) [3]. We speculate that the feature may be a blended composite that can be identified with low-energy vibrations of two-dimensional lattice structures of large molecules, such as PAHs or nitrogenated aromatics. Such structures do not dominate the composition of analog materials generated from CH4 and N2 irradiation. We are performing studies forming aerosol analog via UV irradiation of aromatic precursors - specifically C6H6 - to understand how the unique chemical architecture of the products will influence the observable aerosol characteristics. The optical and chemical properties of the aromatic analog will be compared to those formed from CH4/N2 mixtures, with a focus on the as-yet unidentified far-IR absorbance feature. Preliminary results indicate that the photochemically-formed aromatic aerosol has distinct chemical composition, and may incorporate nitrogen either into the ring structure or adjoined chemical groups. These compositional differences are demonstrated in the aerosol mass spectra shown in Figure 2. The aromatic aerosol also demonstrates strong chemical reactivity when exposed to laboratory air, indicating substantial stored chemical potential. Oxidatoin and solubility studies wil be presented and implicatoins for prebiotic chemistry o nTitan will be discussed.

Retrieval of the ultraviolet aerosol optical depth during a spring campaign in the Bavarian Alps.

PubMed

Lenoble, Jacqueline; Martin, Timothy; Blumthaler, Mario; Philipona, Rolf; Albold, Astrid; Cabot, Thierry; de La Casinière, Alain; Gröbner, Julian; Masserot, Dominique; Müller, Martin; Pichler, Thomas; Seckmeyer, Günther; Schmucki, Daniel; Touré, Mamadou Lamine; Yvon, Alexis

2002-03-20

A measurement campaign was organized in March 1999 in the Bavarian Alps as part of the European project, Characteristics of the UV Radiation Field in the Alps (CUVRA), to analyze the effect of altitude, aerosols, and snow cover on ground-level UV spectral irradiance. We present the results of simultaneous measurements of aerosol optical depth (AOD) made at various sites on two cloudless days in March 1999. The two days exhibited different aerosol conditions. Results derived from spectral measurements of UV irradiance are compared with data from filter radiometer measurements made at discrete wavelengths extending from the UV to the near IR. The different methods generated values for the AOD that were in good agreement. This result confirms that one can use either method to retrieve the AOD with an uncertainty of approximately 0.03-0.05. On 18 March, high turbidity was observed at low altitude (400-nm AOD approximately 0.5 at 700 m above sea level), and the AOD decreased regularly with altitude; on 24 March, the turbidity was much less (0.11 at 700 m above sea level). On both days very low AODs (0.05-0.09) were measured at 3000 m above sea level. The spectral dependence of the AOD is often parameterized by the angstrom relationship; the alpha parameter is generally difficult or impossible to retrieve from spectral measurements because of the relatively narrow wavelength range (320-400 nm), and only one of the spectro-radiometers used during the campaign permits this retrieval. In most cases, during this field campaign, alpha was found by filter sunphotometers to be 1.1-1.5.

A charged aerosol detector/chemiluminescent nitrogen detector/liquid chromatography/mass spectrometry system for regular and fragment compound analysis in drug discovery.

PubMed

Jiang, Yutao; Hascall, Daniel; Li, Delia; Pease, Joseph H

2015-09-11

In this paper, we introduce a high throughput LCMS/UV/CAD/CLND system that improves upon previously reported systems by increasing both the quantitation accuracy and the range of compounds amenable to testing, in particular, low molecular weight "fragment" compounds. This system consists of a charged aerosol detector (CAD) and chemiluminescent nitrogen detector (CLND) added to a LCMS/UV system. Our results show that the addition of CAD and CLND to LCMS/UV is more reliable for concentration determination for a wider range of compounds than either detector alone. Our setup also allows for the parallel analysis of each sample by all four detectors and so does not significantly increase run time per sample. Copyright © 2015 Elsevier B.V. All rights reserved.

Cloud and aerosol polarimetric imager

NASA Astrophysics Data System (ADS)

Zhang, Junqiang; Shao, Jianbing; Yan, Changxiang

2014-02-01

Cloud and Aerosol Polarimetric Imager (CAPI), which is the first onboard cloud and aerosol Polarimetric detector of CHINA, is developed to get cloud and aerosol data of atmosphere to retrieve aerosol optical and microphysical properties to increase the reversion precision of greenhouse gasses (GHGs). The instrument is neither a Polarization and Direction of Earth's Reflectance (POLDER) nor a Directional Polarimetric Camera (DPC) type polarized camera. It is a multispectral push broom system using linear detectors, and can get 5 bands spectral data, from ultraviolet (UV) to SWIR, of the same ground feature at the same time without any moving structure. This paper describes the CAPI instrument characteristics, composition, calibration, and the nearest development.

Ultraviolet Studies of Jupiter's Hydrocarbons and Aerosols from Galileo

NASA Technical Reports Server (NTRS)

Gladstone, G. Randall

2001-01-01

This is the final report for this project. The purpose of this project was to support PI Wayne Pryor's effort to reduce and analyze Galileo UVS (Ultraviolet Spectrometer) data under the JSDAP program. The spectral observations made by the Galileo UVS were to be analyzed to determine mixing ratios for important hydrocarbon species (and aerosols) in Jupiter's stratosphere as a function of location on Jupiter. Much of this work is still ongoing. To date, we have concentrated on analyzing the variability of the auroral emissions rather than the absorption signatures of hydrocarbons, although we have done some work in this area with related HST-STIS data.

Linking NASA Data with Environmental Exposures and Health Outcomes in Theater of War

DTIC Science & Technology

2012-10-01

variations of tropospheric aerosols." Journal of the Atmospheric Sciences 60(1): 119-136. Brown, M., D. Lary, et al. (2006). "Using neural nets to...A. Tanskanen, et al. (2007). "Aerosols and surface UV products from ozone monitoring instrument observations: An overview." Journal of Geophysical

Exploitation of the UV Aerosol Index scattering angle dependence: Properties of Siberian smoke plumes

NASA Astrophysics Data System (ADS)

Penning de Vries, Marloes; Beirle, Steffen; Sihler, Holger; Wagner, Thomas

2017-04-01

The UV Aerosol Index (UVAI) is a simple measure of aerosols from satellite that is particularly sensitive to elevated layers of absorbing particles. It has been determined from a range of instruments including TOMS, GOME-2, and OMI, for almost four decades and will be continued in the upcoming Sentinel missions S5-precursor, S4, and S5. Despite its apparent simplicity, the interpretation of UVAI is not straightforward, as it depends on aerosol abundance, absorption, and altitude in a non-linear way. In addition, UVAI depends on the geometry of the measurement (viewing angle, solar zenith and relative azimuth angles), particularly if viewing angles exceed 45 degrees, as is the case for OMI and TROPOMI (on S5-precursor). The dependence on scattering angle complicates the interpretation and further processing (e.g., averaging) of UVAI. In certain favorable cases, however, independent information on aerosol altitude and absorption may become available. We present a detailed study of the scatter angle dependence using SCIATRAN radiative transfer calculations. The model results were compared to observations of an extensive Siberian smoke plume, of which parts reached 10-12 km altitude. Due to its large extent and the high latitude, OMI observed the complete plume in five consecutive orbits under a wide range of scattering angles. This allowed us to deduce aerosol characteristics (absorption and layer height) that were compared with collocated CALIOP lidar measurements.

The absorption budget of fresh biomass burning aerosol from realistic laboratory fires

NASA Astrophysics Data System (ADS)

Wagner, N. L.; Adler, G. A.; Franchin, A.; Lamb, K.; Manfred, K.; Middlebrook, A. M.; Selimovic, V.; Schwarz, J. P.; Washenfelder, R. A.; Womack, C.; Yokelson, R. J.

2017-12-01

Wildfires are expected to increase globally due to climate change. The smoke from these wildfires has a highly uncertain radiative effect, largely due to the lack of detailed understanding of its optical properties. As part of the NOAA FIREX project, we have measured the optical properties of smoke primarily from laboratory burning of North American fuels at the Missoula Fire Sciences Laboratory. Here, we present a budget of the aerosol absorption from a portion of the laboratory fires. The total aerosol absorption was measured with photoacoustic spectrometers (PAS) at four wavelengths (405 nm, 532 nm, 660 nm, 870 nm) spanning the visible spectral region. The aerosol absorption is attributed to black carbon which absorbs broadly across the visible and ultraviolet (UV) spectral region and brown carbon (BrC) which absorbs in the blue and UV spectral regions. Then aerosol absorption measurements are compared with measurements of refractory black carbon (rBC) concentration by laser induced incandescence (SP2) and measurements of BrC concentration from a particle-into-liquid sampler coupled to a liquid absorption cell (BrC-PILS). Periodically, a thermodenuder was inserted upstream of all of the instruments to constrain the relationship between aerosol volatility and absorption. We synthesize these measurements to constrain the various contributors to total absorption including effects of lensing on rBC absorption, and of BrC that is not volatilized in the thermodenuder.

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

DOE PAGES

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.; ...

2017-01-01

In this study, the WRF-Chem regional model is updated to improve simulated short-lived pollutants (e.g., aerosols, ozone) in the Arctic. Specifically, we include in WRF-Chem 3.5.1 (with SAPRC-99 gas-phase chemistry and MOSAIC aerosols) (1) a correction to the sedimentation of aerosols, (2) dimethyl sulfide (DMS) oceanic emissions and gas-phase chemistry, (3) an improved representation of the dry deposition of trace gases over seasonal snow, and (4) an UV-albedo dependence on snow and ice cover for photolysis calculations. We also (5) correct the representation of surface temperatures over melting ice in the Noah Land Surface Model and (6) couple and further test the recent KF-CuP (Kain–Fritsch +more » Cumulus Potential) cumulus parameterization that includes the effect of cumulus clouds on aerosols and trace gases. The updated model is used to perform quasi-hemispheric simulations of aerosols and ozone, which are evaluated against surface measurements of black carbon (BC), sulfate, and ozone as well as airborne measurements of BC in the Arctic. The updated model shows significant improvements in terms of seasonal aerosol cycles at the surface and root mean square errors (RMSEs) for surface ozone, aerosols, and BC aloft, compared to the base version of the model and to previous large-scale evaluations of WRF-Chem in the Arctic. These improvements are mostly due to the inclusion of cumulus effects on aerosols and trace gases in KF-CuP (improved RMSE for surface BC and BC profiles, surface sulfate, and surface ozone), the improved surface temperatures over sea ice (surface ozone, BC, and sulfate), and the updated trace gas deposition and UV albedo over snow and ice (improved RMSE and correlation for surface ozone). DMS emissions and chemistry improve surface sulfate at all Arctic sites except Zeppelin, and correcting aerosol sedimentation has little influence on aerosols except in the upper troposphere.« less

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.

In this study, the WRF-Chem regional model is updated to improve simulated short-lived pollutants (e.g., aerosols, ozone) in the Arctic. Specifically, we include in WRF-Chem 3.5.1 (with SAPRC-99 gas-phase chemistry and MOSAIC aerosols) (1) a correction to the sedimentation of aerosols, (2) dimethyl sulfide (DMS) oceanic emissions and gas-phase chemistry, (3) an improved representation of the dry deposition of trace gases over seasonal snow, and (4) an UV-albedo dependence on snow and ice cover for photolysis calculations. We also (5) correct the representation of surface temperatures over melting ice in the Noah Land Surface Model and (6) couple and further test the recent KF-CuP (Kain–Fritsch +more » Cumulus Potential) cumulus parameterization that includes the effect of cumulus clouds on aerosols and trace gases. The updated model is used to perform quasi-hemispheric simulations of aerosols and ozone, which are evaluated against surface measurements of black carbon (BC), sulfate, and ozone as well as airborne measurements of BC in the Arctic. The updated model shows significant improvements in terms of seasonal aerosol cycles at the surface and root mean square errors (RMSEs) for surface ozone, aerosols, and BC aloft, compared to the base version of the model and to previous large-scale evaluations of WRF-Chem in the Arctic. These improvements are mostly due to the inclusion of cumulus effects on aerosols and trace gases in KF-CuP (improved RMSE for surface BC and BC profiles, surface sulfate, and surface ozone), the improved surface temperatures over sea ice (surface ozone, BC, and sulfate), and the updated trace gas deposition and UV albedo over snow and ice (improved RMSE and correlation for surface ozone). DMS emissions and chemistry improve surface sulfate at all Arctic sites except Zeppelin, and correcting aerosol sedimentation has little influence on aerosols except in the upper troposphere.« less

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

NASA Astrophysics Data System (ADS)

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.; Berg, Larry K.; Fast, Jerome D.; Easter, Richard C.; Shrivastava, Manish; Thomas, Jennie L.

2017-10-01

In this study, the WRF-Chem regional model is updated to improve simulated short-lived pollutants (e.g., aerosols, ozone) in the Arctic. Specifically, we include in WRF-Chem 3.5.1 (with SAPRC-99 gas-phase chemistry and MOSAIC aerosols) (1) a correction to the sedimentation of aerosols, (2) dimethyl sulfide (DMS) oceanic emissions and gas-phase chemistry, (3) an improved representation of the dry deposition of trace gases over seasonal snow, and (4) an UV-albedo dependence on snow and ice cover for photolysis calculations. We also (5) correct the representation of surface temperatures over melting ice in the Noah Land Surface Model and (6) couple and further test the recent KF-CuP (Kain-Fritsch + Cumulus Potential) cumulus parameterization that includes the effect of cumulus clouds on aerosols and trace gases. The updated model is used to perform quasi-hemispheric simulations of aerosols and ozone, which are evaluated against surface measurements of black carbon (BC), sulfate, and ozone as well as airborne measurements of BC in the Arctic. The updated model shows significant improvements in terms of seasonal aerosol cycles at the surface and root mean square errors (RMSEs) for surface ozone, aerosols, and BC aloft, compared to the base version of the model and to previous large-scale evaluations of WRF-Chem in the Arctic. These improvements are mostly due to the inclusion of cumulus effects on aerosols and trace gases in KF-CuP (improved RMSE for surface BC and BC profiles, surface sulfate, and surface ozone), the improved surface temperatures over sea ice (surface ozone, BC, and sulfate), and the updated trace gas deposition and UV albedo over snow and ice (improved RMSE and correlation for surface ozone). DMS emissions and chemistry improve surface sulfate at all Arctic sites except Zeppelin, and correcting aerosol sedimentation has little influence on aerosols except in the upper troposphere.

Carbonaceous Aerosol Removal During Precipitation Events: Climate Implications

NASA Astrophysics Data System (ADS)

Gaffney, J. S.; Marley, N. A.; Bridges, G. L.; Marchany-Rivera, A.; Begum, M.

2009-12-01

Atmospheric aerosols and their links to clouds are one of the main focus areas of the Department of Energy’s Atmospheric Systems Research, due to the fact that aerosols and clouds constitute the major uncertainties in radiative forcing that need to be reduced for more accurate modeling of climate, particularly regional climate. The impact of absorbing aerosols on radiative balance of the atmosphere will depend on their atmospheric lifetimes as well as their UV-visible absorption profiles. Aerosol lifetimes depend on the aerosols ability to take up water and grow to sufficient size to be either removed by gravitational settling or to act as cloud condensation nuclei and be removed by precipitation scavenging. The investigation of uv-visible absorbing aerosols is underway using a seven-channel aethalometer to evaluate the change in aerosol optical absorption during precipitation events. Angstrom absorption exponents (AAEs) are determined before, during, and after rain events to examine the impact on the aerosol absorption profiles anticipated by removal of the water soluble short-wave absorbing species (i.e. HULIS) that can be produced by photochemical oxidation of biogenic emissions (isoprene, monoterpenes, sesquiterpenes). Aerosol absorption data are presented from observations made at the University of Arkansas at Little Rock and other sites, which clearly show that a significant amount of absorbing carbon is not removed during rain events, and that the organic matter removed is likely secondary organics produced from biogenic precursors. The dissolved organic carbon measured in precipitation samples along with determinations of natural radionuclide tracers are also used to help examine the extent of carbonaceous aerosol removal by precipitation. The data are discussed in terms of the potential impacts of anthropogenic enhancement of aerosol absorption by secondary organic aerosols adding to atmospheric heating and changes in atmospheric dynamics. The potential impacts of these organic aerosol species as sources of organic carbon in surface waters is also addressed. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328 and Grant No. DE-FG02-07-ER64329 as part of the Atmospheric Science Program.

403 nm cavity ring-down measurements of brown carbon aerosol

NASA Astrophysics Data System (ADS)

Kwon, D.; Grassian, V. H.; Kleiber, P.; Young, M. A.

2017-12-01

Atmospheric aerosol influences Earth's climate by absorbing and scattering incoming solar radiation and outgoing terrestrial radiation. One class of secondary organic aerosol (SOA), called brown carbon (BrC), has attracted attention for its wavelength dependent light absorbing properties with absorption coefficients that generally increase from the visible (Vis) to ultraviolet (UV) regions. Here we report results from our investigation of the optical properties of BrC aerosol products from the aqueous phase reaction of ammonium sulfate (AS) with methylglyoxal (MG) using cavity ring-down spectroscopy (CRDS) at 403 nm wavelength. We have measured the optical constants of BrC SOA from the AS/MG reaction as a function of reaction time. Under dry flow conditions, we observed no apparent variation in the BrC refractive index with aging over the course of 22 days. The retrieved BrC optical constants are similar to those of AS with n = 1.52 for the real component. Despite significant UV absorption observed from the bulk BrC solution, the imaginary index value at 403 nm is below our minimum detection limit which puts an upper bound of k as 0.03. These observations are in agreement with results from our recent studies of the light scattering properties of this BrC aerosol.

Assessment of Residential Biomass Burning During Winter in Las Vegas, Nevada

NASA Astrophysics Data System (ADS)

Brown, S. G.; Lee, T.; Olson, D.; Norris, G.; Roberts, P. T.; Collett, J. L.

2011-12-01

Concentrations of organic matter (OM) and black carbon (BC) were measured at a site in a residential area of Las Vegas, Nevada, and multiple analytical methods were used to determine the amounts attributable to biomass burning. In January 2008, measurements of a wood burning tracer, levoglucosan, were made via gas chromatography-mass spectroscopy (n=17). In addition, an Aerodyne High Resolution Aerosol Mass Spectrometer (HR-AMS) measured OM and C2H4O2+, a levoglucosan-derived fragment. During 2007 and 2008, two-channel Aethalometer data were also collected; the difference between the 370 nm and 880 nm channels (UV-BC difference) was used to indicate the presence of wood smoke. Concentrations of OM, BC, C2H4O2+, and levoglucosan, as well as the UV-BC difference, were all highest during the evening hours (generally between 1800 and 0000 LST). Average OM concentrations were 3.3 μg/m3 during January but were 6.9 μg/m3 during the overnight hours (between 1700 and 0000 LST). Median levoglucosan concentrations were 0.14 μg/m3. The correlation of levoglucosan with C2H4O2+ was very high (r2=0.92). During the evening hours, correlation between BC and C2H4O2+ was good (r2=0.79); however, correlation was poor during other hours (r2<0.40), suggesting that other emissions such as mobile-source emissions were likely the dominant source of BC during those hours. C2H4O2+ showed modest correlation with UV-BC (e.g., r2=0.45). Using EPA's positive matrix factorization tool, EPA PMF, on the January HR-AMS data, we determined that biomass burning organic aerosol (BBOA) constituted 12% of the OM on average, but about 25% of the OM during evening hours. BBOA correlated well with levoglucosan (r2=0.82) and C2H4O2+ (r2=0.93). Levoglucosan measurements suggested that wood burning could constitute 38% of the OM during the overnight periods on average, although this number greatly depends on the assumed ratio of levoglucosan to OM in a source profile for residential biomass burning. The particle size distributions of mass for OM and m/z 60 (which includes other ions but is dominated by C2H4O2+) were quite broad, peaking between 100 nm and 450 nm for m/z 60 and between 200 nm and 450 nm for OM, suggesting relatively fresh aerosol. H/C ratios were highest (typically 1.57) and O/C ratios were lowest (typically 0.25) during evening hours, and the OM/OC ratio was, on average, 1.47, also indicating very fresh aerosol. Using levoglucosan and AMS markers, we can separate residential biomass burning influences from other sources of carbonaceous aerosol in the area.

Secondary organic aerosol formation from isoprene photooxidation

NASA Astrophysics Data System (ADS)

Kroll, J. H.; Ng, N. L.; Murphy, S. M.; Flagan, R. C.; Seinfeld, J. H.

2005-12-01

We report chamber studies of the formation of secondary organic aerosol (SOA) from the oxidation of isoprene (2-methyl-1,3-butadiene). Isoprene is the most abundant non-methane hydrocarbon emitted into the troposphere (source strength of ~500 Tg/year), so even small SOA yields may have a large impact on global SOA production. Reactions are carried out in Caltech's dual 28 m3 Teflon chambers, and aerosol growth is monitored by a differential mobility analyzer (DMA) and an Aerodyne time-of-flight aerosol mass spectrometer (AMS). Isoprene oxidation is initiated by the UV irradiation of isoprene in the presence of hydrogen peroxide, with NO added for high-NOx experiments. These conditions ensure that isoprene oxidation is initiated by reaction with the OH radical, with negligible interference from other oxidants (ozone, nitrate radicals, and O atoms). Aerosol growth is observed under both high-NOx and low-NOx conditions, at isoprene concentrations lower than measured in previous studies (down to 8 ppb). SOA yields are found to be in the range of 1-2%. Yields exhibit a complex dependence on NOx concentration, likely a result of changes in the chemistry of organic peroxy radicals. It is shown that condensable compounds are formed from further reactions of first-generation isoprene oxidation products; the rates and products of such gas-phase reactions are at present poorly understood. Additionally, measurements of SOA composition indicate that these products undergo reactions in the aerosol phase, leading to the formation of low-volatility oligomeric products.

Improvement of retrieval algorithms for severe air pollution

NASA Astrophysics Data System (ADS)

Mukai, Sonoyo; Sano, Itaru; Nakata, Makiko

2016-10-01

Increased emissions of anthropogenic aerosols associated with economic growth can lead to increased concentrations of hazardous air pollutants. Furthermore, dust storms or biomass burning plumes can cause serious environmental hazards, yet their aerosol properties are poorly understood. Our research group has worked on the development of an efficient algorithm for aerosol retrieval during hazy episodes (dense concentrations of atmospheric aerosols). It is noted that near UV measurements are available for detection of carbonaceous aerosols. The biomass burning aerosols (BBA) due to large-scale forest fires and/or burn agriculture exacerbated the severe air pollution. It is known that global warming and climate change have caused increasing instances of forest fires, which have in turn accelerated climate change. It is well known that this negative cycle decreases the quality of the global environment and human health. The Japan Aerospace Exploration Agency (JAXA) has been developing a new Earth observing system, the GCOM (Global Change Observation Mission) project, which consists of two satellite series: GCOM-W1 and GCOM-C1. The first GCOM-C satellite will board the SGLI (second generation GLI [global imager]) to be launched in early 2017. The SGLI is capable of multi-channel (19) observation, including a near UV channel (0.380 μm) and two polarization channels at red and near-infrared wavelengths of 0.67 and 0.87 μm. Thus, global aerosol retrieval will be achieved with simultaneous polarization and total radiance. In this study, algorithm improvement for aerosol remote sensing, especially of BBA episodes, is examined using Terra/MODIS measurements from 2003, when the GLI and POLDER-2 sensors were working onboard the Japanese satellite ADEOS-2.

Ambient Observations of the Soot Aging Process during the SHARP Intensive Field Campaign

NASA Astrophysics Data System (ADS)

Reed, C.; Collins, D. R.; Khalizov, A. F.; Zheng, J.; Zhang, R.

2009-12-01

Soot aerosols affect climate both directly through absorption of solar radiation and indirectly by potentially serving as cloud condensation nuclei. Among the sources of uncertainty surrounding the effects of soot aerosol on the environment is the lack of scientific insight into the soot aging process, in which soot particles develop a coating of secondary species such as sulfates, ammonium, nitrate, and organics. Such processes may alter the behavior of soot by modifying particle morphology over time leading to changes in chemical, physical and scattering properties of the aerosol. However, it is often difficult to quantify such processes in the ambient environment due to the complex composition and spatial and temporal variability of the atmospheric aerosol. In order to better understand the effects of the environment on soot particles, it is desirable to study the processes responsible for their transformation in the ambient air without influence from variability in source region and history prior to sampling. To achieve this, the overall soot aging process in the ambient environment was physically isolated utilizing environmental chambers. Chamber measurements were conducted on the Moody Tower at the University of Houston using The Ambient Aerosol Chamber for Evolution Studies (AACES) during the SHARP campaign. AACES is a roughly cubical chamber constructed of a rigid acrylic outer shell, which transmits UV radiation both in the UV-B and UV-A ranges. FEP Teflon lines the inside of the chamber on all sides and the top, while expanded-PTFE (ePTFE) Teflon is used on the bottom of the chamber. The fibrous structure of the ePTFE acts as a barrier to particulates, while allowing gas molecules to move virtually unimpeded from the surrounding air into the chamber, creating an environment inside the chamber that is initially free of particles and continuously mimics the local ambient air. In order to study the effects of the soot aging process, a non-premixed propane flame was used to generate a polydisperse fresh soot aerosol. Then, using a differential mobility analyzer, a monodisperse, uncharged soot aerosol was injected into the environmental chamber. Observations of particle concentration, size, hygroscopicity, effective density, and light extinction and scattering properties were carried out over time using a tandem differential mobility analyzer system, an aerosol particle mass analyzer, a nephelometer and a cavity ringdown spectrometer. Results from preliminary analysis of the data collected during the campaign will be presented.

Evaluation of applicability of high-resolution multiangle imaging photo-polarimetric observations for aerosol atmospheric correction

NASA Astrophysics Data System (ADS)

Kalashnikova, Olga; Garay, Michael; Xu, Feng; Diner, David; Seidel, Felix

2016-07-01

Multiangle spectro-polarimetric measurements have been advocated as an additional tool for better understanding and quantifying the aerosol properties needed for atmospheric correction for ocean color retrievals. The central concern of this work is the assessment of the effects of absorbing aerosol properties on remote sensing reflectance measurement uncertainty caused by neglecting UV-enhanced absorption of carbonaceous particles and by not accounting for dust nonsphericity. In addition, we evaluate the polarimetric sensitivity of absorbing aerosol properties in light of measurement uncertainties achievable for the next generation of multi-angle polarimetric imaging instruments, and demonstrate advantages and disadvantages of wavelength selection in the UV/VNIR range. In this work a vector Markov Chain radiative transfer code including bio-optical models was used to quantitatively evaluate in water leaving radiances between atmospheres containing realistic UV-enhanced and non-spherical aerosols and the SEADAS carbonaceous and dust-like aerosol models. The phase matrices for the spherical smoke particles were calculated using a standard Mie code, while those for non-spherical dust particles were calculated using the numerical approach developed for modeling dust for the AERONET network of ground-based sunphotometers. As a next step, we have developed a retrieval code that employs a coupled Markov Chain (MC) and adding/doubling radiative transfer method for joint retrieval of aerosol properties and water leaving radiance from Airborne Multiangle SpectroPolarimetric Imager-1 (AirMSPI-1) polarimetric observations. The AirMSPI-1 instrument has been flying aboard the NASA ER-2 high altitude aircraft since October 2010. AirMSPI typically acquires observations of a target area at 9 view angles between ±67° at 10 m resolution. AirMSPI spectral channels are centered at 355, 380, 445, 470, 555, 660, and 865 nm, with 470, 660, and 865 reporting linear polarization. We tested prototype retrievals by comparing the retrieved aerosol concentration, size distribution, water-leaving radiance, and chlorophyll concentrations from Airborne Multiangle SpectroPolarimetric Imager-1 (AirMSPI-1) observations to values reported by the USC SeaPRISM AERONET-OC site off the coast of California. The retrieval was then applied to a variety of costal regions in California to evaluate variability in the water-leaving radiance under different atmospheric conditions. We will present results, and will discuss algorithm sensitivity and potential applications for future space-borne coastal monitoring.

Retrieving the Height of Smoke and Dust Aerosols by Synergistic Use of VIIRS, OMPS, and CALIOP Observations

NASA Technical Reports Server (NTRS)

Lee, Jaehwa; Hsu, N. Christina; Bettenhausen, Corey; Sayer, Andrew M.; Seftor, Colin J.; Jeong, Myeong-Jae

2015-01-01

Aerosol Single scattering albedo and Height Estimation (ASHE) algorithm was first introduced in Jeong and Hsu (2008) to provide aerosol layer height as well as single scattering albedo (SSA) for biomass burning smoke aerosols. One of the advantages of this algorithm was that the aerosol layer height can be retrieved over broad areas, which had not been available from lidar observations only. The algorithm utilized aerosol properties from three different satellite sensors, i.e., aerosol optical depth (AOD) and Ångström exponent (AE) from Moderate Resolution Imaging Spectroradiometer (MODIS), UV aerosol index (UVAI) from Ozone Monitoring Instrument (OMI), and aerosol layer height from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Here, we extend the application of the algorithm to Visible Infrared Imaging Radiometer Suite (VIIRS) and Ozone Mapping and Profiler Suite (OMPS) data. We also now include dust layers as well as smoke. Other updates include improvements in retrieving the AOD of nonspherical dust from VIIRS, better determination of the aerosol layer height from CALIOP, and more realistic input aerosol profiles in the forward model for better accuracy.

The role of cloud contamination, aerosol layer height and aerosol model in the assessment of the OMI near-UV retrievals over the ocean

NASA Astrophysics Data System (ADS)

Gassó, Santiago; Torres, Omar

2016-07-01

Retrievals of aerosol optical depth (AOD) at 388 nm over the ocean from the Ozone Monitoring Instrument (OMI) two-channel near-UV algorithm (OMAERUV) have been compared with independent AOD measurements. The analysis was carried out over the open ocean (OMI and MODerate-resolution Imaging Spectrometer (MODIS) AOD comparisons) and over coastal and island sites (OMI and AERONET, the AErosol RObotic NETwork). Additionally, a research version of the retrieval algorithm (using MODIS and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) information as constraints) was utilized to evaluate the sensitivity of the retrieval to different assumed aerosol properties. Overall, the comparison resulted in differences (OMI minus independent measurements) within the expected levels of uncertainty for the OMI AOD retrievals (0.1 for AOD < 0.3, 30 % for AOD > 0.3). Using examples from case studies with outliers, the reasons that led to the observed differences were examined with specific purpose to determine whether they are related to instrument limitations (i.e., pixel size, calibration) or algorithm assumptions (such as aerosol shape, aerosol height). The analysis confirms that OMAERUV does an adequate job at rejecting cloudy scenes within the instrument's capabilities. There is a residual cloud contamination in OMI pixels with quality flag 0 (the best conditions for aerosol retrieval according to the algorithm), resulting in a bias towards high AODs in OMAERUV. This bias is more pronounced at low concentrations of absorbing aerosols (AOD 388 nm ˜ < 0.5). For higher aerosol loadings, the bias remains within OMI's AOD uncertainties. In pixels where OMAERUV assigned a dust aerosol model, a fraction of them (< 20 %) had retrieved AODs significantly lower than AERONET and MODIS AODs. In a case study, a detailed examination of the aerosol height from CALIOP and the AODs from MODIS, along with sensitivity tests, was carried out by varying the different assumed parameters in the retrieval (imaginary index of refraction, size distribution, aerosol height, particle shape). It was found that the spherical shape assumption for dust in the current retrieval is the main cause of the underestimate. In addition, it is demonstrated in an example how an incorrect assumption of the aerosol height can lead to an underestimate. Nevertheless, this is not as significant as the effect of particle shape. These findings will be incorporated in a future version of the retrieval algorithm.

Surface Modified TiO2 Obscurants for Increased Safety and Performance

DTIC Science & Technology

2012-11-01

based obscurant devices in performance. 15. SUBJECT TERMS Obscurant, visible, IR , smoke, TiO2, aerosol, particle, surface modification...hexamethyldimethoxysilane IR Infrared wavelength LabRAM Lab scale Resonant Acoustic Mixer from Resodyn Corporation LPM Liters Per Minute M106 Currently fielded (Army...trinitrophloroglucinol UV-Vis Ultraviolet-visible wavelengths KEYWORDS Obscurant, visible, IR , smoke, TiO2, aerosol, particle, surface modification

Linking NASA Data with Environmental Exposures and Health Outcomes in Theater of War

DTIC Science & Technology

2013-10-01

variations  of   tropospheric   aerosols."  Journal  of  the  Atmospheric  Sciences  60(1):  119-­‐136.   Brown,  M.,  D...al.   (2007).   "Aerosols   and   surface   UV   products   from   ozone   monitoring   instrument   observations:   An

Aerosol effects on the UV irradiance in Santiago de Chile

NASA Astrophysics Data System (ADS)

Cordero, R. R.; Seckmeyer, G.; Damiani, A.; Jorquera, J.; Carrasco, J.; Muñoz, R.; Da Silva, L.; Labbe, F.; Laroze, D.

2014-11-01

Santiago de Chile (33°27‧ S-70°41‧ W) is a mid-latitude city of 6 million inhabitants with a complicated surrounding topography. Aerosol extinction in Santiago is determined by the semi-arid local climate, the urban pollution, a regional subsidence thermal inversion layer, and the boundary-layer wind airflow. In this paper we report on spectral measurements of the surface irradiance (at 290-600 nm wavelength range) carried out during 2013 in the heart of the city by using a double monochromator-based spectroradiometer system. These measurements were used to assess the effect of local aerosols, paying particular attention to the ultraviolet (UV) range. We found that the aerosol optical depth (AOD) exhibited variations likely related to changes in the subsidence thermal inversion and in the boundary-layer winds. Although the AOD at 350 nm typically ranged from 0.2 to 0.3, peak values of about 0.7 were measured. The AOD diminished with the wavelength and typically ranged from 0.1 to 0.2 at 550 nm. Our AOD data were found to be consistent with measurements of the particulate matter (PM) mass concentration.

Overall kinetics of heterogeneous elemental mercury reactions on TiO2 sorbent particles with UV radiation

EPA Science Inventory

A system consisting of a photochemical reaction was used to evaluate the kinetic parameters, such as reaction order and rate constant for the elemental mercury uptake by TiO2 in the presence of uv irradiation. TiO2 particles generated by an aerosol route were used in a fixed bed...

Real-time measurement of UV-inactivated Escherichia coli bacterial particles by electrospray-assisted UVAPS spectrometry.

PubMed

Jung, Jae Hee; Lee, Jung Eun; Bae, Gwi Nam

2011-08-01

The ultraviolet aerodynamic particle sizer (UVAPS) is a novel commercially available aerosol spectrometer for real-time continuous monitoring of viable bioaerosols, based on fluorescence from living microorganisms. In a previous study, we developed an electrospray-assisted UVAPS using biological electrospray techniques, which have the advantage of generating non-agglomerated single particles by the repulsive electrical forces. With this electrospraying of suspensions containing microorganisms, the analytical system can supply more accurate and quantitative information about living microorganisms than with conventional aerosolization. Using electrospray-assisted UVAPS, we investigated the characteristics of bacterial particles with various viabilities in real-time. Escherichia coli was used as the test microorganism, and its initial viability was controlled by the degree of exposure to UV irradiation. In the stable cone-jet domain, the particle size distributions of test bacterial particles remained almost uniform regardless of the degree of UV inactivation. However, the fluorescence spectra of the bacterial particles changed with the degree of UV inactivation. The fluorescence characteristics of UV-inactivated bacterial particles tended to show a similar decline with viability, determined by the sampling and culture method, although the percentage showing fluorescence was higher than that showing viability. Copyright © 2011 Elsevier B.V. All rights reserved.

Martian atmospheric O3 retrieval development for the NOMAD-UVIS spectrometer

NASA Astrophysics Data System (ADS)

Hewson, W.; Mason, J. P.; Leese, M.; Hathi, B.; Holmes, J.; Lewis, S. R.; Iriwin, P. G. J.; Patel, M. R.

2017-09-01

The composition of atmospheric trace gases and aerosols is a highly variable and poorly constrained component of the martian atmosphere, and by affecting martian climate and UV surface dose, represents a key parameter in the assessment of suitability for martian habitability. The ExoMars Trace Gas Orbiter (TGO) carries the Open University (OU) designed Ultraviolet and VIsible Spectrometer (UVIS) instrument as part of the Belgian-led Nadir and Occultation for MArs Discovery (NOMAD) spectrometer suite. NOMAD will begin transmitting science observations of martian surface and atmosphere back-scattered UltraViolet (UV) and visible radiation in Spring 2018, which will be processed to derive spatially and temporally averaged atmospheric trace gas and aerosol concentrations, intended to provide a better understanding of martian atmospheric photo-chemistry and dynamics, and will also improve models of martian atmospheric chemistry, climate and habitability. Work presented here illustrates initial development and testing of the OU's new retrieval algorithm for determining O3 and aerosol concentrations from the UVIS instrument.

Venus Upper Clouds and the UV Absorber From MESSENGER/MASCS Observations

NASA Astrophysics Data System (ADS)

Pérez-Hoyos, S.; Sánchez-Lavega, A.; García-Muñoz, A.; Irwin, P. G. J.; Peralta, J.; Holsclaw, G.; McClintock, W. M.; Sanz-Requena, J. F.

2018-01-01

One of the most intriguing, long-standing questions regarding Venus's atmosphere is the origin and distribution of the unknown UV absorber, responsible for the absorption band detected at the near-UV and blue range of Venus's spectrum. In this work, we use data collected by Mercury Atmospheric and Surface Composition Spectrometer (MASCS) spectrograph on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission during its second Venus flyby in June 2007 to address this issue. Spectra range from 0.3 μm to 1.5 μm including some gaseous H2O and CO2 bands, as well as part of the SO2 absorption band and the core of the UV absorption. We used the NEMESIS radiative transfer code and retrieval suite to investigate the vertical distribution of particles in the equatorial atmosphere and to retrieve the imaginary refractive indices of the UV absorber, assumed to be well mixed with Venus's small mode 1 particles. The results show a homogeneous equatorial atmosphere, with cloud tops (height for unity optical depth) at 75 ± 2 km above surface. The UV absorption is found to be centered at 0.34 ± 0.03 μm with a full width at half maximum of 0.14 ± 0.01 μm. Our values are compared with previous candidates for the UV aerosol absorber, among which disulfur oxide (S2O) and dioxide disulfur (S2O2) provide the best agreement with our results.

Combined use of Satellite and Surface Observations to Infer the Imaginary Part of Refractive Index of Saharan Dust

NASA Technical Reports Server (NTRS)

Sinyuk, Alexander; Torres, Omar; Dubovik, Oleg; Bhartia, P. K. (Technical Monitor)

2002-01-01

We present a method for retrieval of imaginary part of refractive index of desert dust aerosol in UV part of spectrum along with aerosol layer height above the ground. The method uses Total Ozone Mapping Spectrometer' (TOMS) measurements of the top of atmosphere radiances (331 nm, 360 nm) and aerosol optical depth provided by Aerosol Robotic Network (AERONET) (440 nm). Obtained values of imaginary part of refractive index retrieved for Saharan dust aerosol at 360 nm are significantly lower than previously reported values. The average retrieved values vary between 0.0054 and 0.0066 for different geographical locations. Our findings are in good agreement with the results of several recent investigations. The time variability of retrieved values for aerosol layer height is consistent with the predictions of dust transport model.

Effects of Radon and UV Exposure on Skin Cancer Mortality in Switzerland.

PubMed

Vienneau, Danielle; de Hoogh, Kees; Hauri, Dimitri; Vicedo-Cabrera, Ana M; Schindler, Christian; Huss, Anke; Röösli, Martin

2017-06-16

Skin cancer incidence in Switzerland is among the highest in the world. In addition to exposure to ultraviolet (UV) radiation, radon alpha particles attached to aerosols can adhere to the skin and potentially cause carcinogenic effects. We investigated the effects of radon and UV exposure on skin cancer mortality. Cox proportional hazard regression was used to study the association between exposures and skin cancer mortality in adults from the Swiss National Cohort. Modeled radon exposure and erythemal-weighted UV dose were assigned to addresses at baseline. Effect estimates were adjusted for sex, civil status, mother tongue, education, job position, neighborhood socioeconomic position, and UV exposure from outdoor occupation. The study included 5.2 million adults (mean age 48 y) and 2,989 skin cancer deaths, with 1,900 indicating malignant melanoma (MM) as the primary cause of death. Adjusted hazard ratios (HR) for MM at age 60 were 1.16 (95% CI: 1.04, 1.29) per 100 Bq/m 3 radon and 1.11 (1.01, 1.23) per W/m 2 in UV dose. Radon effects decreased with age. Risk of MM death associated with residential UV exposure was higher for individuals engaged in outdoor work with UV exposure (HR 1.94 [1.17, 3.23]), though not statistically significantly different compared to not working outdoors (HR 1.09 [0.99, 1.21], p =0.09). There is considerable variation in radon and UV exposure across Switzerland. Our study suggests both are relevant risk factors for skin cancer mortality. A better understanding of the role of the UV radiation and radon exposure is of high public health relevance. https://doi.org/10.1289/EHP825.

Effects of Radon and UV Exposure on Skin Cancer Mortality in Switzerland

PubMed Central

de Hoogh, Kees; Hauri, Dimitri; Vicedo-Cabrera, Ana M.; Schindler, Christian; Huss, Anke; Röösli, Martin

2017-01-01

Background: Skin cancer incidence in Switzerland is among the highest in the world. In addition to exposure to ultraviolet (UV) radiation, radon alpha particles attached to aerosols can adhere to the skin and potentially cause carcinogenic effects. Objectives: We investigated the effects of radon and UV exposure on skin cancer mortality. Methods: Cox proportional hazard regression was used to study the association between exposures and skin cancer mortality in adults from the Swiss National Cohort. Modeled radon exposure and erythemal-weighted UV dose were assigned to addresses at baseline. Effect estimates were adjusted for sex, civil status, mother tongue, education, job position, neighborhood socioeconomic position, and UV exposure from outdoor occupation. Results: The study included 5.2 million adults (mean age 48 y) and 2,989 skin cancer deaths, with 1,900 indicating malignant melanoma (MM) as the primary cause of death. Adjusted hazard ratios (HR) for MM at age 60 were 1.16 (95% CI: 1.04, 1.29) per 100Bq/m3 radon and 1.11 (1.01, 1.23) per W/m2 in UV dose. Radon effects decreased with age. Risk of MM death associated with residential UV exposure was higher for individuals engaged in outdoor work with UV exposure (HR 1.94 [1.17, 3.23]), though not statistically significantly different compared to not working outdoors (HR 1.09 [0.99, 1.21], p=0.09). Conclusions: There is considerable variation in radon and UV exposure across Switzerland. Our study suggests both are relevant risk factors for skin cancer mortality. A better understanding of the role of the UV radiation and radon exposure is of high public health relevance. https://doi.org/10.1289/EHP825 PMID:28686556

Spatio-temporal distribution of absorbing and non-absorbing aerosols derived from Aura-OMI Aerosol Index over Greece

NASA Astrophysics Data System (ADS)

Kaskaoutis, D. G.; Nastos, P. T.; Kosmopoulos, P. G.; Kambezidis, H. D.; Kharol, S. K.; Badarinath, K. V. S.

2009-04-01

The Aerosol Index (AI) observations derived from the Ozone Monitoring Instrument (OMI) on board the Dutch-Finnish Aura satellite are analyzed over Greece covering the whole period of the OMI available data, from September 2004 to August 2008. The objective of this study was to analyze the spatial, seasonal and inter-annual variability of AI over Greece, detected by OMI during 2004-2008, with an evaluation of potential contributing factors, including precipitation and long-range transport (Sahara dust and European pollution). The AI data cover the whole Greek territory (34o-42oN, 20o-28oE) with a spatial resolution of 0.25o x 0.25o (13 km x 24 km at nadir). The results show significant spatial and temporal variability of the seasonal and monthly mean AI, with higher values at the southern parts and lower values over northern Greece. On the other hand, the AI values do not show significant differences between the western and eastern parts and, therefore, the longitude-averaged AI values can be utilized to reveal the strong south-to-north gradient. This gradient significantly changes from season to season being more intense in spring and summer, while it is minimized in winter. Another significant remark is the dominance of negative AI values over northern Greece in the summer months, indicating the presence of non-UV absorbing aerosols, such as sulfate and sea-salt particles. The great geographical extent of the negative AI values in the summer months is indicative of long-range transport of such aerosols. In contrast, the high positive AI values over south Greece, mainly in spring, clearly reveal the UV-absorbing nature of desert-dust particles affecting the area during Saharan dust events. Synoptically, the spatial distribution in OMI-AI values was related to the Saharan dust events mainly over southern Greece and to the trans-boundary-pollution transport, consisting mainly of sulfate particles, in northern Greece. The annual variation of spatial-averaged AI values shows a predominant spring maximum (0.424±0.329, in April) and a summer minimum due to the negative AI values observed over northern Greece. In the cold period of the year (November to February) the AI values are higher over northern Greece compared to those in south, while in the rest of the year the opposite exists. This study is first of its kind utilizing OMI-AI data and its spatial and temporal distribution over Greece and can be the basis for other studies in the future.

New in situ Aerosol Spectral Optical Measurements over 300-700 nm, Extinction and Total Absorption, Paired with Absorption from Water- and Methanol-soluble Aerosol Extracts

NASA Astrophysics Data System (ADS)

Jordan, C. E.; Stauffer, R. M.; Lamb, B.; Novak, M. G.; Mannino, A.; Hudgins, C.; Thornhill, K. L., II; Crosbie, E.; Winstead, E.; Anderson, B.; Martin, R.; Shook, M.; Ziemba, L. D.; Beyersdorf, A. J.; Corr, C.

2017-12-01

A new in situ spectral aerosol extinction instrument (custom built, SpEx) built to cover the 300-700 nm range at 1 nm spectral resolution and temporal resolution of 4 minutes was deployed on the top deck ( 10 m above the water surface) of the R/V Onnuri during the KORUS-OC research cruise around South Korea in spring 2016. This new instrument was one component of a suite of in situ aerosol optical measurements that included 3-visible-wavelength scattering (Airphoton IN101 Nephelometer, at 450, 532, & 632 nm) and absorption (Brechtel Tricolor Absorption Photometer Model 2901, at 467, 528, & 652 nm) with sub-minute temporal resolution; two sets of filters (Teflon and glass fiber, both collected over 3 hour daytime and 12 hour overnight intervals) to provide aerosol absorption spectra over the same wavelength range as SpEx. The glass fiber filters were placed in the center of an integrating sphere (Labsphere DRA-CA-30) attached to a dual beam spectrophotometer (Cary 100 Bio UV-Visible Spectrophotometer) to measure total aerosol absorption spectra via an established method used by the ocean color community to obtain absorption spectra from particles suspended in sea water. Adapting this methodology for atmospheric aerosol measurements provides a new avenue to obtain spectral total aerosol absorption, particularly useful for expanding in situ measurement capabilities into the UV range. The Teflon filters were cut in half with one half extracted in deionized water and the other half extracted in methanol. The solutions were filtered and injected into a liquid waveguide capillary cell (World Precision Instruments LWCC-3100, 100 cm pathlength) to measure the absorption spectra for each solution. In addition, the water extracts were measured via ion chromatography (Dionex ICS-3000 Ion Chromatography System) to obtain water-soluble inorganic ion concentrations, as well as via aerosol mass spectrometry (Aerodyne Research, Inc. HR-ToF High Resolution Aerosol Mass Spectrometer) to obtain organic aerosol concentrations. Results from the KORUS-OC data set will be discussed. In particular, the relationships between the optical information and chemical information will be examined.

SPICAM: studying the global structure and composition of the Martian atmosphere

NASA Astrophysics Data System (ADS)

Bertaux, J.-L.; Fonteyn, D.; Korablev, O.; Chassefre, E.; Dimarellis, E.; Dubois, J. P.; Hauchecorne, A.; Lefèvre, F.; Cabane, M.; Rannou, P.; Levasseur-Regourd, A. C.; Cernogora, G.; Quemerais, E.; Hermans, C.; Kockarts, G.; Lippens, C.; de Maziere, M.; Moreau, D.; Muller, C.; Neefs, E.; Simon, P. C.; Forget, F.; Hourdin, F.; Talagrand, O.; Moroz, V. I.; Rodin, A.; Sandel, B.; Stern, A.

2004-08-01

The SPICAM (SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars) instrument consists of two spectrometers. The UV spectrometer addresses key issues about ozone and its H2O coupling, aerosols, the atmospheric vertical temperature structure and the ionosphere. The IR spectrometer is aimed primarily at H2O and abundances and vertical profiling of H2O and aerosols. SPICAM's density/temperature profiles will aid the development of meteorological and dynamical atmospheric models from the surface up to 160 km altitude. UV observations of the upper atmosphere will study the ionosphere and its direct interaction with the solar wind. They will also allow a better understanding of escape mechanisms, crucial for insight into the long-term evolution of the atmosphere.

Radiative characteristics of Clouds embedded in and occurring beneath Smoke analyzed using airborne multiangular measurements

NASA Astrophysics Data System (ADS)

Gautam, R.; Gatebe, C. K.; Varnai, T.; Singh, M.; Poudyal, R.

2016-12-01

Clouds in the presence of absorbing aerosols results in their apparent darkening, observed at the Top of Atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the warming/darkening effect and potential impacts on regional climate via semidirect and thermodynamic pathways, above-cloud aerosols have been characterized in recent satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, retrievals of aerosol and cloud properties are affected by large uncertainties when they co-occur. In this study, we present radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer (CAR), collected during the ARCTAS and SAFARI campaigns in Canada and southern Africa, respectively. Scattered cumulus clouds embedded in dense smoke over land (Canada) as well as smoke aerosols above marine stratocumulus clouds (southeast Atlantic) show characteristic spectral gradient across the UV-visible-NIR spectrum using CAR data. In general, clouds in the presence of smoke are impacted by absorbing aerosol-induced darkening at the shorter wavelengths (e.g. UV and blue bands), as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. The circular and spiral flights not only allowed the complete characterization of the angular distribution of smoke-cloud radiative interactions, but also provided the vertical distribution of smoke and clouds. Overall, the observational-based smoke-cloud radiative interactions were found to be physically consistent with theoretical 1D and 3D radiation calculations. These airborne observations are also complemented by satellite data from MODIS reflectances and CERES shortwave fluxes, providing a synergistic radiative impact assessment of clouds in the presence of smoke. http://car.gsfc.nasa.gov/

Quantifying the impact of smoke aerosol on the UV radiation

NASA Astrophysics Data System (ADS)

Sokolik, I. N.; Tatarskii, V.; Hall, S. R.; Petropavlovskikh, I. V.

2017-12-01

We present an analysis of the impact of smoke on the UV radiation. The analysis is performed for a case study by combining the modeling and measurements. The case study is focusing in wildfires occurred in California in ????. The fires have been affecting the environment in the region, posing a serious threat to the human well - being.The modeling is performed using a fully couple WRF- Chem- SMOKE model. The model uses the FRP MODIS satellite data to generate the smoke emission for an actual event. The smoke aerosol is treated in a size and composition resolved manner. The optical properties are computed online and provided to the TUV model that is incorporated in the WRF - Chem-SMOKE model. The analysis of the impact of smoke on the UV radiation is performed. We assess the impact of smoke on the TOA radiative forcing. Our results show a significant impact of smoke on the radiative regime of the atmosphere.

Airborne UV DIAL Measurements of Ozone and Aerosols

NASA Technical Reports Server (NTRS)

Grant, William B.; Browell, Edward V.

2000-01-01

The NASA Langley Research Center's airborne UV Differential Absorption Lidar (DIAL) system measures vertical profiles of ozone and aerosols above and below the aircraft along its flight track. This system has been used in over 20 airborne field missions designed to study the troposphere and stratosphere since 1980. Four of these missions involved tropospheric measurement programs in the Pacific Ocean with two in the western North Pacific and two in the South Pacific. The UV DIAL system has been used in these missions to study such things as pollution outflow, long-range transport, and stratospheric intrusions; categorize the air masses encountered; and to guide the aircraft to altitudes where interesting features can be studied using the in situ instruments. This paper will highlight the findings with the UV DIAL system in the Pacific Ocean field programs and introduce the mission planned for the western North Pacific for February-April 2001. This will be an excellent opportunity for collaboration between the NASA airborne mission and those with ground-based War systems in Asia Pacific Rim countries to make a more complete determination of the transport of air from Asia to the western Pacific.

Combined Use of Satellite and Surface Observations to Infer the Imaginary Part of Refractive Index of Saharan Dust

NASA Technical Reports Server (NTRS)

Sinyuk, Alexander; Torres, Omar; Dubovik, Oleg; Bhartia, P. K. (Technical Monitor)

2002-01-01

We present a method for retrieval of the imaginary part of refractive index of desert dust aerosol in the near UV part of spectrum. The method uses Total Ozone Mapping Spectrometer (TOMS) measurements of the top of the atmosphere radiances at 331 and 360 run and aerosol optical depth provided by the Aerosol Robotic Network (AERONET). Obtained values of imaginary part of refractive index retrieved for Saharan dust aerosol at 360 nm are significantly lower than previously reported values. The average retrieved values vary between 0.0054 and 0.0066 for different geographical locations. Our findings are in good agreement with the results of several recent investigations.

Global Increase in UV Irradiance during the Past 30 Years (1979-2008) Estimated from Satellite Data

NASA Technical Reports Server (NTRS)

Herman, Jay R.

2010-01-01

Zonal average ultraviolet irradiance (flux ultraviolet, F(sub uv)) reaching the Earth's surface has significantly increased since 1979 at all latitudes except the equatorial zone. Changes are estimated in zonal average F(sub uv) caused by ozone and cloud plus aerosol reflectivity using an approach based on Beer's law for monochromatic and action spectrum weighted irradiances. For four different cases, it is shown that Beer's Law leads to a power law form similar to that applied to erythemal action spectrum weighted irradiances. Zonal and annual average increases in F(sub uv) were caused by decreases in ozone amount from 1979 to 1998. After 1998, midlatitude annual average ozone amounts and UV irradiance levels have been approximately constant. In the Southern Hemisphere, zonal and annual average UV increase is partially offset by tropospheric cloud and aerosol transmission decreases (hemispherical dimming), and to a lesser extent in the Northern Hemisphere. Ozone and 340 nm reflectivity changes have been obtained from multiple joined satellite time series from 1978 to 2008. The largest zonal average increases in F(sub uv) have occurred in the Southern Hemisphere. For clear-sky conditions at 50 S, zonal average F(sub uv) changes are estimated (305 nm, 23%; erythemal, 8.5%; 310 nm, 10%; vitamin D production, 12%). These are larger than at 50 N (305 nm, 9%; erythemal, 4%; 310 nm, 4%; vitamin D production, 6%). At the latitude of Buenos Aires, Argentina (34.6 S), the clear-sky Fuv increases are comparable to the increases near Washington, D. C. (38.9 N): 305 nm, 9% and 7%; erythemal, 6% and 4%; and vitamin D production, 7% and 5%, respectively.

NARSTO ICARTT NEAX 2004 DOE G-1 DATA

Atmospheric Science Data Center

2018-04-09

... Probe Chemiluminescence UV Ozone Detector Pulsed Fluorescence HPLC Aerosol Spectrometer Probe Pyranometer Photometer ... Carbon Monixide Hydrogen Peroxide Sulfate Particles Nitrate Particles Crustal Particles Order Data:  ...

UV 380 nm Reflectivity of the Earth's Surface

NASA Technical Reports Server (NTRS)

Herman, J. R.; Celarier, E.; Larko, D.

2000-01-01

The 380 nm radiance measurements of TOMS (Total Ozone Mapping Spectrometer) have been converted into a global data set of daily (1979 to 1992) Lambert equivalent reflectivities R of the Earth's surface and boundary layer (clouds, aerosols, surface haze, and snow/ice). Since UV surface reflectivity is between 2 and 8% for both land and water during all seasons of the year (except for ice and snow cover), reflectivities larger than the surface value indicates the presence of clouds, haze, or aerosols in the satellite field of view. Statistical analysis of 14 years of daily data show that most snow/ice-free regions of the Earth have their largest fraction of days each year when the reflectivity is low (R less than 10%). The 380 nm reflectivity data shows that the true surface reflectivity is 2 to 3% lower than the most frequently occurring reflectivity value for each TOMS scene. The most likely cause of this could be a combination of frequently occurring boundary-layer water or aerosol haze. For most regions, the observation of extremely clear conditions needed to estimate the surface reflectivity from space is a comparatively rare occurrence. Certain areas (e.g., Australia, southern Africa, portions of northern Africa) are cloud-free more than 80% of the year, which exposes these regions to larger amounts of UV radiation than at comparable latitudes in the Northern Hemisphere. Regions over rain-forests, jungle areas, Europe and Russia, the bands surrounding the Arctic and Antarctic regions, and many ocean areas have significant cloud cover (R greater than 15%) more than half of each year. In the low to middle latitudes, the areas with the heaviest cloud cover (highest reflectivity for most of the year) are the forest areas of northern South America, southern Central America, the jungle areas of equatorial Africa, and high mountain regions such as the Himalayas or the Andes. The TOMS reflectivity data show the presence of large nearly clear ocean areas and the effects of the major ocean currents on cloud production.

The SOA formation model combined with semiempirical quantum chemistry for predicting UV-Vis absorption of secondary organic aerosols.

PubMed

Zhong, Min; Jang, Myoseon; Oliferenko, Alexander; Pillai, Girinath G; Katritzky, Alan R

2012-07-07

A new model for predicting the UV-visible absorption spectra of secondary organic aerosols (SOA) has been developed. The model consists of two primary parts: a SOA formation model and a semiempirical quantum chemistry method. The mass of SOA is predicted using the PHRCSOA (Partitioning Heterogeneous Reaction Consortium Secondary Organic Aerosol) model developed by Cao and Jang [Environ. Sci. Technol., 2010, 44, 727]. The chemical composition is estimated using a combination of the kinetic model (MCM) and the PHRCSOA model. The absorption spectrum is obtained by taking the sum of the spectrum of each SOA product calculated using a semiempirical NDDO (Neglect of Diatomic Differential Overlap)-based method. SOA was generated from the photochemical reaction of toluene or α-pinene at different NO(x) levels (low NO(x): 24-26 ppm, middle NO(x): 49 ppb, high NO(x): 104-105 ppb) using a 2 m(3) indoor Teflon film chamber. The model simulation reasonably agrees with the measured absorption spectra of α-pinene SOA but underestimates toluene SOA under high and middle NO(x) conditions. The absorption spectrum of toluene SOA is moderately enhanced with increasing NO(x) concentrations, while that of α-pinene SOA is not affected. Both measured and calculated UV-visible spectra show that the light absorption of toluene SOA is much stronger than that of α-pinene SOA.

Organic Aerosol Formation Photoenhanced by the Formation of Secondary Photo-sensitizers in ageing Aerosols

NASA Astrophysics Data System (ADS)

Aregahegn, Kifle; Nozière, Barbara; George, Christian

2013-04-01

Humankind is facing a changing environment possibly due to anthropogenic stress on the atmosphere. In this context, aerosols play a key role by affecting the radiative climate forcing, hydrological cycle, and by their adverse effect on health. The role of organic compounds in these processes is however still poorly understood because of their massive chemical complexity and numerous transformations. This is particularly true for Secondary Organic Aerosol (SOA), which are produced in the atmosphere by organic gases. Traditionally, the driving forces for SOA growth is believed to be the partitioning onto aerosol seeds of condensable gases, either emitted primarily or resulting from the gas phase oxidation of organic gases. However, even the most up-to-date models based on such mechanisms can not account for the SOA mass observed in the atmosphere, suggesting the existence of other, yet unknown formation processes. The present study shows experimental evidence that particulate phase chemistry produces photo-sensitizers that lead to photo-induced formation and growth of secondary organic aerosol in the near UV and the presence of volatile organic compounds (VOC) such as terpenes. By means of an aerosol flow tube reactor equipped with Scanning Mobility Particle Sizer (SMPS) having Kr-85 source aerosol neutralizer, Differential Mobility Analyser (DMA) and Condensation Particle Sizer (CPC), we identified that traces of the aerosol phase product of glyoxal chemistry as is explained in Gallway et al., and Yu et al., namely imidazole-2-carboxaldehyde (IC) is a strong photo-sensitizer when irradiated by near-UV in the presence of volatile organic compounds such as terpenes. Furthermore, the influence of pH, type and concentration of VOCs, composition of seed particles, relative humidity and irradiation intensity on particle growth were studied. This novel photo-sensitizer contributed to more than 30% of SOA growth in 19min irradiation time in the presence of terpenes in the system and has linear relationship with the irradiation intensity. These results demonstrate that, upon ageing, organic aerosols can produce photo-sensitizers which auto-photo-catalyses their SOA growth.

The Role of Cloud Contamination, Aerosol Layer Height and Aerosol Model in the Assessment of the OMI Near-UV Retrievals Over the Ocean

NASA Technical Reports Server (NTRS)

Gasso, Santiago; Torres, Omar

2016-01-01

Retrievals of aerosol optical depth (AOD) at 388 nm over the ocean from the Ozone Monitoring Instrument (OMI) two-channel near-UV algorithm (OMAERUV) have been compared with independent AOD measurements. The analysis was carried out over the open ocean (OMI and MODerate-resolution Imaging Spectrometer (MODIS) AOD comparisons) and over coastal and island sites (OMI and AERONET, the AErosol RObotic NETwork). Additionally, a research version of the retrieval algorithm (using MODIS and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) information as constraints) was utilized to evaluate the sensitivity of the retrieval to different assumed aerosol properties. Overall, the comparison resulted in differences (OMI minus independent measurements) within the expected levels of uncertainty for the OMI AOD retrievals (0.1 for AOD less than 0.3, 30% for AOD greater than 0.3). Using examples from case studies with outliers, the reasons that led to the observed differences were examined with specific purpose to determine whether they are related to instrument limitations (i.e., pixel size, calibration) or algorithm assumptions (such as aerosol shape, aerosol height). The analysis confirms that OMAERUV does an adequate job at rejecting cloudy scenes within the instrument's capabilities. There is a residual cloud contamination in OMI pixels with quality flag 0 (the best conditions for aerosol retrieval according to the algorithm), resulting in a bias towards high AODs in OMAERUV. This bias is more pronounced at low concentrations of absorbing aerosols (AOD 388 nm approximately less than 0.5). For higher aerosol loadings, the bias remains within OMI's AOD uncertainties. In pixels where OMAERUV assigned a dust aerosol model, a fraction of them (less than 20 %) had retrieved AODs significantly lower than AERONET and MODIS AODs. In a case study, a detailed examination of the aerosol height from CALIOP and the AODs from MODIS, along with sensitivity tests, was carried out by varying the different assumed parameters in the retrieval (imaginary index of refraction, size distribution, aerosol height, particle shape). It was found that the spherical shape assumption for dust in the current retrieval is the main cause of the underestimate. In addition, it is demonstrated in an example how an incorrect assumption of the aerosol height can lead to an underestimate. Nevertheless, this is not as significant as the effect of particle shape. These findings will be incorporated in a future version of the retrieval algorithm.

Preliminary results of aerosols' properties studied with EPF measurements from the SPICAM/UV instrument

NASA Astrophysics Data System (ADS)

Willame, Yannick; Carine Vandaele, Ann; Depiesse, Cedric; Gillotay, Didier; Kochenova, Svetlana; Montmessin, Franck

2013-04-01

Aerosols on Mars have an important impact on the radiative transfer properties of its atmosphere. Today their spectral properties and therefore their interaction with UV radiation are only poorly known. Improving the radiative transfer modeling requires a better knowledge of their characteristics, in particular of their opacity, phase function and single scattering albedo. Part of such information can be accessed by using EPF observations. The SPICAM instrument on board of the Mars-Express satellite is a 2 channel spectrometer. One channel operates in the ultraviolet (118-320 nm) and the second one in the infrared (1.0-1.7μm). SPICAM has been orbiting around the red planet since 2003 and has thus provided a large set of data. The instrument is capable of measuring under different geometries (nadir, limb, occultation) and one of them, called EPF (Emission Phase Function), can be a tool to study aerosols' properties. We have developed a new retrieval algorithm for nadir measurements based on the radiative transfer model LIDORT. This new code performs simulations of spectra taking into account gas absorption, surface reflection and scattering by aerosols and gases. The retrieval method, based on the optimal estimation, allows us up to now to deduce the ozone column density, the aerosols' optical depth and the surface albedo (with fixed wavelength dependencies). We are developing our model further in order to better study the aerosols' characteristics using EPF observations, which consist in looking at the same point on the planet while the satellite moves along the orbit. As the attempt to study all the aerosols' properties simultaneously was not convincing, we started studying their opacity and the influence of its altitude distribution with the other characteristics fixed. We will present preliminary results of our study on aerosols' properties using EPF data from SPICAM.

Preliminary results of aerosols' properties studied with EPF measurements from the SPICAM/UV instrument

NASA Astrophysics Data System (ADS)

Willame, Y.; Vandaele, A.-C.; Depiesse, C.; Gillotay, D.; Kochenova, S.; Montmessin, F.

2012-04-01

Aerosols on Mars have an important impact on the radiative transfer properties of its atmosphere. Today their spectral properties and therefore their interaction with UV radiation are only poorly known. Improving the radiative transfer modeling requires a better knowledge of their characteristics, in particular of their opacity, phase function and single scattering albedo. We will show that such information can be accessed by using EPF observations. The SPICAM instrument on board of the Mars-Express satellite is a 2 channel spectrometer. One channel operates in the ultraviolet (118-320 nm) and the second one in the infrared (1.0-1.7μm). SPICAM has been orbiting around the red planet since 2003 and has thus provided a large set of data. The instrument is capable of measuring under different geometries (nadir, limb, occultation) and one of them, called EPF (Emission Phase Function), is a practical tool to study aerosols' properties. We have developed a new retrieval algorithm for nadir measurements based on the radiative transfer model LIDORT. This new code performs simulations of spectra taking into account gas absorption, surface reflection and scattering by aerosols and gases. The retrieval method, based on the optimal estimation, allows us up to now to deduce the ozone column density, the aerosols' optical depth and the surface albedo (with fixed wavelength dependencies). We are developing our model further in order to better study the aerosols' characteristics using EPF observations, which consist in looking at the same point on the planet while the satellite moves along the orbit. As the attempt to study all the aerosols' properties simultaneously was not convincing, we will start with studying their opacity and its altitude distribution with the other characteristics fixed. We will present preliminary results of our study on aerosols' properties and their wavelength dependencies, using EPF data. The method will be illustrated by investigating SPICAM observations obtained in EPF mode.

Novel insight on photochemistry at interfaces: potential impact on Seconday Aerosol Formation?

NASA Astrophysics Data System (ADS)

Rossignol, S.; George, C.; Aregahegn, K.

2014-12-01

Traditionally, the driving forces for SOA growth is believed to be the partitioning onto aerosol seeds of condensable gases, either emitted primarily or resulting from the gas phase oxidation of organic gases. However, even the most up-to-date models based on such mechanisms cannot account for the SOA mass observed in the atmosphere, suggesting the existence of other, yet unknown formation processes. The present study shows experimental evidence that particulate phase chemistry produces photo-sensitizers that lead to photo-induced formation and growth of secondary organic aerosol in the near UV and the presence of volatile organic compounds (VOC) such as terpenes. By means of an aerosol flow tube reactor equipped with Scanning Mobility Particle Sizer (SMPS), Differential Mobility Analyzer (DMA) and Condensation Particle Sizer (CPC), we identified that traces in the aerosol phase of glyoxal chemistry products, namely imidazole-2-carboxaldehyde (IC) are strong photo-sensitizers when irradiated with near-UV. In the presence of volatile organic compounds such as terpenes, this chemistry leads to a fast aerosol growth. Given the potential importance of this new photosensitized growth pathway for ambient OA, the related reaction mechanism was investigated at a molecular level. Bulk and flow tube experiments were performed to identify major products of the reaction of limonene with the triplet state of IC by direct (+/-)ESI-HRMS and UPLC/(+/-)HESI-HRMS analysis. Detection of recombination products of IC with limonene or with itself, in bulk and flow tube experiment ts, showed that IC is able to initiate a radical chemistry in the aerosol phase under realistic irradiation conditions. Furthermore, highly oxygenated limonene reaction products were detected, clearly explaining the observed OA growth. The chemistry of peroxy radicals derived from limonene upon addition of oxygen explains the formation of such low-volatile compounds without any traditional gas phase oxidant. These results demonstrate that, upon ageing, organic aerosols can produce photo-sensitizers which auto-photo-catalyse their SOA growth.

Modern Day Re-analysis of Pinatubo SO2 Injection, Cloud dispersion and Stratospheric Aerosols

NASA Astrophysics Data System (ADS)

Bhartia, P. K.; Krotkov, N. A.; Aquila, V.; Hughes, E. J.; Li, C.; Fisher, B. L.

2016-12-01

Cataclysmic June 15 1991 eruption of Mt. Pinatubo injected largest amount of SO2 in the lower stratosphere during the satellite era. The resulting volcanic clouds were tracked by the NASA's Nimbus 7 TOMS sensor that provided first estimates of total emissions of SO2 gas ( 15+/-3 Mt). Over time SO2 converted to long-lasting sulfate aerosols affecting radiation balance and composition of the stratosphere. Large numbers of articles and papers published in the past 25 years make this the most well-studied volcanic eruption. Still, several unresolved scientific issues remain: SO2 injection height, subsequent lofting of SO2 and aerosols in the stratosphere, how much sulfate aerosols were produced in the eruption (i.e., initial sulfate to SO2 ratio), and impact on stratospheric ozone. To answer these questions we have re-analyzed past satellite measurements using modern day tools, such as re-analyzed wind data from Goddard Modeling and Assimilation Office (GMAO), improved trajectory analysis tools, better radiative transfer model to process backscatter UV data from N7/TOMS and two NOAA SBUV/2s sensors, which provided measurements at shorter UV wavelengths that are sensitive to aerosols and SO2 in the mid stratosphere ( 25 km). We have also re-analyzed aerosol data from SAGE, AVHRR, and several instruments on the UARS satellite. These data provide strong support for recent assessment by modelers that the bulk of SO2 mass injected by the volcano was well below the 25 km altitude, contrary to earlier estimates. We also find convincing evidence that there was significant amount of sulfate aerosols embedded even in the day-old SO2 cloud. These results strongly support the hypothesis that SO2 gas self-lofted to 25 km as seeen by UARS MLS several weeks after the eruption and aerosols to 35 km, as seen by the SAGE sensor several months later.

Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

NASA Astrophysics Data System (ADS)

Anet, J. G.; Muthers, S.; Rozanov, E.; Raible, C. C.; Peter, T.; Stenke, A.; Shapiro, A. I.; Beer, J.; Steinhilber, F.; Brönnimann, S.; Arfeuille, F.; Brugnara, Y.; Schmutz, W.

2013-11-01

The response of atmospheric chemistry and dynamics to volcanic eruptions and to a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere-ocean chemistry general circulation model SOCOL-MPIOM (modeling tools for studies of SOlar Climate Ozone Links-Max Planck Institute Ocean Model) covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric dynamics in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15%, which represents the presently discussed highest estimate of UV irradiance change caused by solar activity changes, causes global ozone decrease below the stratopause reaching as much as 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the mid-stratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere, allowing more water vapour to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx, leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the Dalton Minimum (DM) - this effect is especially well visible for NOx/NOy. Thus, this study also shows the non-linear behaviour of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the energetic particle precipitation. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

Development of a tunable Fabry-Perot interferometer UV camera for monitoring sulfur dioxide emissions

NASA Astrophysics Data System (ADS)

Tamminen, J.; Kujanpää, J.; Ojanen, H.; Saari, H.; Näkki, I.; Tukiainen, S.; Kyrölä, E.

2017-12-01

We present a novel UV camera for sulfur dioxide emission monitoring.The camera is equipped with a piezo-actuated Fabry-Perot interferometer allowing thefilter transmission to be tuned to match the differential absorption features ofsulfur dioxide in the wavelength region 305-320 nm. The differential absorption structuresare exploited to reduce the interfering effects of weakly wavelength dependent absorbers, suchas aerosols and black carbon, present in the exhaust gas. A data processing algorithm basedon two air gaps of the filter is presented allowing collection of a sufficient signal-to-noise ratio fordetecting sulfur dioxide in the ship plumes even in the designated emission control areas, such as the Baltic Seawhere the sulfur content limit of fuel oil is 0.1 %. First field tests performed inLänsisatama harbour, Helsinki Finland, indicate that sulfur dioxide can be detectedin ship plumes. The camera is light-weight and can be mounted to a drone.

The UV Sensor Onboard the Mars Science Laboratory Mission: Correction and Generation of UV Fluxes

NASA Astrophysics Data System (ADS)

Vicente-Retortillo, Á.; Martinez, G.; Renno, N. O.; Lemmon, M. T.; Gomez-Elvira, J.

2017-12-01

The Rover Environmental Monitoring Station UV sensor (UVS) onboard the Mars Science Laboratory mission has completed more than 1750 sols of measurements, providing an unprecedented coverage ranging from diurnal to interannual times scales [1,2]. The UVS is comprised of six photodiodes to measure the UV flux in the ranges 200-380, 320-380, 280-320, 200-280, 230-290 and 300-350 nm [3]. UV fluxes in units of W/m2 can be found in the NASA Planetary Data System (PDS). However, dust deposition on the UVS and a non-physical discontinuity in the calibration functions when the solar zenith angle is above 30º cause errors in these fluxes that increase with time. We have developed a technique to correct UV fluxes from the effects of dust degradation and inconsistencies in the angular response of the UVS. The photodiode output currents (available in the PDS as lower-level TELRDR products), ancillary data records (available in the PDS as ADR products) and dust opacity values derived from Mastcam observations are used for performing the corrections. The corrections have been applied to the UVA band (320-380 nm) for the first 1000 sols of the mission, providing excellent results [4]. We plan to correct the UV fluxes on each of the six UVS bands and to make these results available in the PDS. Data products generated by this study will allow comparisons of the UV radiation environment at Gale crater with that at the locations of the future missions ExoMars 2020 and Mars 2020, as well as the assessment of the potential survivability of biological contaminants brought to Mars from Earth. References: [1] Smith, M. D., et al. (2016), Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes, Icarus, 280, 234-248. [2] Vicente-Retortillo, Á., et al. (2017), Determination of dust aerosol particle size at Gale Crater using REMS UVS and Mastcam measurements, Geophys. Res. Lett., 44, 3502-3508. [3] Gómez-Elvira, J., et al. (2012), REMS: The environmental sensor suite for the Mars Science Laboratory rover, Space Sci. Rev. 170 (1-4), 583-640. [4] Martínez, G.M., et al. (2017), Generation of UV Radiation Data at Gale Crater by Correcting REMS UV Measurements from Dust Deposition and Sensor's Angular Response, LPSC 48.

Simulation comparison of aircraft landing performance in foggy conditions aided by different UV sensors.

PubMed

Lavigne, Claire; Durand, Gérard; Roblin, Antoine

2009-04-20

In the atmosphere pointlike sources are surrounded by an aureole due to molecular and aerosol scattering. UV phase functions of haze droplets have a very important forward peak that limits signal angular spreading in relation to the clear atmosphere case where Rayleigh scattering predominates. This specific property can be exploited using solar blind UV source detection as an aircraft landing aid under foggy conditions. Two methods have been used to compute UV light propagation, based on the Monte Carlo technique and a semi-empirical approach. Results obtained after addition of three types of sensor and UV runway light models show that an important improvement in landing conditions during foggy weather could be achieved by use of a solar blind UV intensified CCD camera with two stages of microchannel plates.

Comparisons of USDA UV shadow-band irradiance measurements with TOMS satellite and DISORT model retrievels under all sky conditions

NASA Astrophysics Data System (ADS)

Slusser, James R.; Krotkov, Nickolay A.; Gao, Wei; Herman, Jay R.; Labow, Gordon; Scott, Gwen

2002-01-01

Comparisons of UV irradiances measured by the USDA UVB Monitoring and Research Network at 305 and 368 nm with retrievals from the NASA TOMS and a multiple scattering radiative transfer code were made for an 18-month period from January 1, 2000 through May 31, 2001 for Las Cruces, New Mexico, USA (32.6 degree(s)N, 106.7 degree(s)W, 1317 m elevation) and Billings, Oklahoma, USA (36.6 degree(s)N, 97.5 degree(s)W, 317 m elevation). Agreement is generally within +/- 12% for all sky conditions and 8% for clear skies. The effects of aerosols is mostly less than 5%, consistent with the measured aerosol optical depths at 368 nm within the range of 0.05 and 0.25.

Ultraviolet light emitting diodes and bio-aerosol sensing

NASA Astrophysics Data System (ADS)

Davitt, Kristina M.

Recent interest in compact ultraviolet (UV) light emitters has produced advances in material quality and device performance from aluminum-rich alloys of the nitride semiconductor system. The epitaxial growth of device structures from this material poses remarkable challenges, and state-of-the-art in semiconductor UV light sources at wavelengths shorter than 350 nm is currently limited to LEDs. A portion of the work presented in this thesis involves the design and characterization of UV LED structures, with particular focus on sub-300 nm LEDs which have only been demonstrated within the last four years. Emphasis has been placed on the integration of early devices with modest efficiencies and output powers into a practical, fluorescence-based bio-sensing instrument. The quality of AlGaInN and AlGaN-based materials is characterized by way of the performance of 340 nm and 290 nm LEDs respectively. A competitive level of device operation is achieved, although much room remains for improvement in the efficiency of light emission from this material system. A preliminary investigation of 300 nm LEDs grown on bulk AIN shows promising electrical and optical characteristics, and illustrates the numerous advantages that this native substrate offers to the epitaxy of wide bandgap nitride semiconductors. The application of UV LEDs to the field of bio-aerosol sensing is pursued by constructing an on-the-fly fluorescence detection system. A linear array of UV LEDs is designed and implemented, and the capability of test devices to excite native fluorescence from bacterial spores is established. In order to fully capitalize on the reduction in size afforded by LEDs, effort is invested in re-engineering the remaining sensor components. Operation of a prototype system for physically sorting bio-aerosols based on fluorescence spectra acquired in real-time from single airborne particles excited by a UV-LED array is demonstrated using the bio-fluorophores NADH and tryptophan. Sensor performance is shown to be ultimately linked to the material quality of high aluminum fraction nitrides, and is expected to show progress as this field matures.

Comparison of ultraviolet detection and charged aerosol detection methods for liquid-chromatographic determination of protoescigenin.

PubMed

Filip, Katarzyna; Grynkiewicz, Grzegorz; Gruza, Mariusz; Jatczak, Kamil; Zagrodzki, Bogdan

2014-01-01

Escin, a complex mixture of pentacyclic triterpene saponins obtained from horse chestnut seeds extract (HCSE; Aesculus hippocastanum L.), constitutes a traditional herbal active substance of preparations (drugs) used for a treatment of chronic venous insufficiency and capillary blood vessel leakage. A new approach to exploitation of pharmacological potential of this saponin complex has been recently proposed, in which the β-escin mixture is perceived as a source of a hitherto unavailable raw material, pentacyclic triterpene aglycone-protoescigenin. Although many liquid chromatography methods are described in the literature for saponins determination, analysis of protoescigenin is barely mentioned. In this work, a new ultra-high performance liquid chromatography (UHPLC) method developed for protoescigenin quantification has been described. CAD (charged aerosol detection), as a relatively new detection method based on aerosol charging, has been applied in this method as an alternative to ultraviolet (UV) detection. The influence of individual parameters on CAD response and sensitivity was studied. The detection was performed using CAD and UV (200 nm) simultaneously and the results were compared with reference to linearity, accuracy, precision and limit of detection.

Characterization of Potential Aerosol Mass using an Oxidation Chamber coupled to an Aerodyne HR-ToF-AMS during DAURE, SHARP, and FLAME-3

NASA Astrophysics Data System (ADS)

Ortega, A. M.; Brune, W. H.; Cubison, M.; Lefer, B. L.; Schallharter, S.; Metzger, A.; Mueller, M.; Hansel, A.; Jimenez, J. L.

2009-12-01

The Potential Aerosol Mass (PAM) oxidation chamber (Kang et al., ACP 2007) used in front of an aerosol instrument provides an indication of the secondary inorganic and organic aerosol formation potential in an airmass. The chamber, a flow tube with small residence time, rapidly oxidizes ambient air through exposure to high concentrations of ozone (O3) and hydroxy (OH) and hydroperoxy (HO2) radicals. Here we use a recently-modified PAM chamber in conjunction with an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS; DeCarlo et al., Anal. Chem. 2006) during two ambient studies and one source study: the Determination of the Sources of the Atmospheric Aerosol in Urban and Rural Environments in Spain (DAURE) in February 2009, the Study of Houston Atmospheric Radical Precursors (SHARP) in April 2009, and the Fire Lab at Missoula Experiment phase 3 (FLAME-3) in Sep. 2009. The AMS samples alternatively between ambient air and chamber-processed air every 2.5 min., and a cycling of the UV light intensity (OH exposure) is also used with a maximum equivalent exposure of about 7 days. Large variations in the organic PAM were observed in the different studies. In particular very large PAM values were observed in several evenings in Houston when the site was impacted by emissions from petrochemical facilities. Optimum OH exposure for maximum PAM was observed at intermediate OH levels. For all experiments we compare the amount of SOA formed in the PAM chamber to the yield predicted by the measured precursors (from PTRMS instruments).

Absorption Properties of Mediterranean Aerosols Obtained from Multi-year Ground-based and Satellite Remote Sensing Observations

NASA Technical Reports Server (NTRS)

Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.

2013-01-01

Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately" absorbing with values of SSA close to approximately 0.94-0.95 +/- 0.04 (at 440 nm) in most cases except over the large cities of Rome and Athens, where aerosol appears more absorbing (SSA approximately 0.89-0.90 +/- 0.04). The aerosol Absorption Angstrom Exponent (AAE, estimated using 440 and 870 nm) is found to be larger than 1 for most sites over the Mediterranean, a manifestation of mineral dust (iron) and/or brown carbon producing the observed absorption. AERONET level-2 sun-photometer data indicate the existence of a moderate East-West gradient, with higher values over the eastern basin (AAEEast. = 1.39/AAEWest. = 1.33) due to the influence of desert dust. The North-South AAE gradient is more pronounced, especially over the western basin. Our additional analysis of AERONET level-1.5 data also shows that organic absorbing aerosols significantly affect some Mediterranean sites. These results indicate that current climate models treating organics as nonabsorbing over the Mediterranean certainly underestimate the warming effect due to carbonaceous aerosols. Acomparative analysis of the regional SSA variability has been attempted using satellite data. OMI and MODIS data show an absorbing zone (SSA approximately 0.90 at 470-500 nm) over Northeastern Africa that does not appear in the MISR retrievals. In contrast, MISR seems able to observe the East-West SSA gradient during summer, as also detected by AERONET. Also, the analysis of SSA provided by satellites indicates that the aerosol over the Mediterranean Sea appears less absorbing during spring (MAM) than summer (JJA).

Aerosol-associated changes in tropical stratospheric ozone following the eruption of Mount Pinatubo

NASA Technical Reports Server (NTRS)

Grant, William B.; Browell, Edward V.; Fishman, Jack; Brackett, Vincent G.; Veiga, Robert E.; Nganga, Dominique; Minga, A.; Cros, Bernard; Butler, Carolyn F.; Fenn, Marta A.

1994-01-01

The large amount of sulfuric acid aerosol formed in the stratosphere by conversion of sulfur dioxide emitted by the eruption of Mount Pinatubo (15.14 deg N, 120.35 deg E) in the Philippines around June 15, 1991, has had a pronounced effect on lower stratospheric ozone in the tropics. Measurements of stratospheric ozone in the tropics using electrochemical concentration cell (ECC) sondes before and after the eruption and the airborne UV differential absorption lidar (DIAL) system after the eruption are compared with Stratospheric Aerosol and Gas Experiment II (SAGE II) measurements from several years before the eruption and ECC sonde measurements from the year prior to the eruption to determine the resulting changes. Ozone decreases of up to 33 % compared with SAGE II climatological values were found to be directly correlated with altitude regions of enhanced aerosol loading in the 16- to 28-km range. A maximum partial-column decrease of 29 +/- Dobson units (DU) was found over the 16- to 28-km range in September 1991 along with small increases (to 5.9 +/- 2 DU) from 28 to 31.5 km. A large decrease of ozone was also found at 4 deg to 8 deg S from May to August 1992, with a maximum decrease of 33 +/- 7 DU found above Brazzaville in July. Aerosol data form the visible channel of the advanced very high resolution radiometer (AVHRR) and the visible wavelength of the UV DIAL system were used to examine the relationship between aerosol (surface area) densities and ozone changes. The tropical stratospheric ozone changes we observed in 1991 and 1992 are likely be explained by a combination of dynamical (vertical transport) perturbations, radiative perturbations on ozone photochemistry, and heterogeneous chemistry.

Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption

NASA Technical Reports Server (NTRS)

Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

2003-01-01

The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

Volcanic Cloud and Aerosol Monitor (VOLCAM) for Deep Space Gateway

NASA Astrophysics Data System (ADS)

Krotkov, N.; Bhartia, P. K.; Torres, O.; Li, C.; Sander, S.; Realmuto, V.; Carn, S.; Herman, J.

2018-02-01

We propose complementary ultraviolet (UV) and thermal Infrared (TIR) filter cameras for a dual-purpose whole Earth imaging with complementary natural hazards applications and Earth system science goals.

Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

NASA Astrophysics Data System (ADS)

Anet, J. G.; Muthers, S.; Rozanov, E.; Raible, C. C.; Peter, T.; Stenke, A.; Shapiro, A. I.; Beer, J.; Steinhilber, F.; Brönnimann, S.; Arfeuille, F.; Brugnara, Y.; Schmutz, W.

2013-06-01

The response of atmospheric chemistry and climate to volcanic eruptions and a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere-ocean-chemistry general circulation model SOCOL-MPIOM covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric climate in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15% causes global ozone decrease below the stratopause reaching 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the midstratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere allowing more water vapor to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the DM - this effect is especially well visible for NOx/NOy. Thus, this study highlights the non-linear behavior of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the EPP. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

Proceedings of the 20th Annual Conference on Atmospheric Transmission Models, 10-12 June 1997

DTIC Science & Technology

1998-05-21

which models multi - wavelength or tunable system performance over slant paths in the atmosphere. Both hard target and aerosol LIDAR systems may be... extinction due to aerosols is a Raman lidar. Raman lidars also have the capability to measure atmospheric temperature and humidity. The lidars we...ozone absorption. The present lidar system provides extinction measurements at UV and visible wavelengths. The tech- nique has been verified over a

Long-term solar UV radiation reconstructed by Artificial Neural Networks (ANN)

NASA Astrophysics Data System (ADS)

Feister, U.; Junk, J.; Woldt, M.

2008-01-01

Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980-1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.

UV Studies of Jupiter's Aerosols and Hydrocarbons

NASA Technical Reports Server (NTRS)

Pryor, Wayne

2004-01-01

This project funded research related to our involvement in the Galileo Ultraviolet Spectrometer experiment. Pryor was a Co-I on that experiment, which recently ended when Galileo crashed into Jupiter's atmosphere. It also funded related research on HST observations of Jupiter's atmosphere, and Cassini observations of Jupiter's atmosphere, and ground-based studies of Jupiter's atmosphere using the facilities of McDonald Observatory. Specific activities related to this grant include study of UV spectra returned by Galileo UVS and Cassini UVIS, development of simple models to explain these spectra, participation in archiving activities for these data sets, travel to conferences, and publication of scientific papers. Highlights of our Jupiter research efforts include: 1.) evidence for heavy hydrocarbons in Jupiter's atmosphere (from HST) (Clarke et al. poster), that may be the source of Jupiter's stratospheric aerosols, 2.) detection of auroral flares in Jupiter's atmosphere from Galileo (Pryor et al., 2001). 3.) establishing a connection between coronal mass ejections and auroral outbursts (Gurnett et al., 2002), and 4) establishing a connection between short-term variations in Jupiter's auroral emissions and radio emissions (Pryor et al. presented at AGU in 2002, paper in preparation).

Feasibility study for GCOM-C/SGLI: Retrieval algorithms for carbonaceous aerosols

NASA Astrophysics Data System (ADS)

Mukai, Sonoyo; Sano, Itaru; Yasumoto, Masayoshi; Fujito, Toshiyuki; Nakata, Makiko; Kokhanovsky, Alexander

2016-04-01

The Japan Aerospace Exploration Agency (JAXA) has been developing the new Earth observing system, GCOM (Global Change Observation Mission) project, which consists of two satellite series of GCOM-W1 and GCOM-C1. The 1st GCOM-C satellite will board the SGLI (second generation global imager) which also includes polarimetric sensor and be planed to launch in early of 2017. The SGLI has multi (19)-channels including near UV channel (380 nm) and two polarization channels at red and near-infrared wavelengths of 670 and 870 nm. EUMETSAT plans to collect polarization measurements with a POLDER follow on 3MI / EPS-SG in 2021. Then the efficient retrieval algorithms for aerosol and/or cloud based on the combination use of radiance and polarization are strongly expected. This work focuses on serious biomass burning episodes in East Asia. It is noted that the near UV measurements are available for detection of the carbonaceous aerosols. The biomass burning aerosols (BBA) generated by forest fire and/or agriculture biomass burning have influenced on the severe air pollutions. It is known that the forest fire increases due to global warming and a climate change, and has influences on them vice versa. It is well known that this negative cycle decreases the quality of global environment and human health. We intend to consider not only retrieval algorithms of remote sensing for severe air pollutions but also detection and/or distinction of aerosols and clouds, because mixture of aerosols and clouds are often occurred in the severe air pollutions. Then precise distinction of aerosols and clouds, namely aerosols in cloudy scenes and/or clouds in heavy aerosol episode, is desired. Aerosol retrieval in the hazy atmosphere has been achieved based on radiation simulation method of successive order of scattering 1,2. In this work, we use both radiance and polarization measurements observed by GLI and POLDER-2 on Japanese ADEOS-2 satellite in 2003 as a simulated data. As a result the possibility of GCOM-C1 / SGLI related to remote sensing for aerosols and/or clouds can be examined. [1] Mukai, S., M. Yasumoto and M. Nakata, 2014: Estimation of biomass burning influence on air pollution around Beijing from an aerosol retrieval model. The Scientific World Journal, Article ID 649648. [2] Mukai, S., M. Nakata, M. Yasumoto, I. Sano and A. Kokhanovsky, 2015:A study of aerosol pollution episode due to agriculture biomass burning in the east-central China using satellite data, Front. Environ. Sci., 3:57, doi: 10.3389/fenvs.2015.00057.

Investigation of the oxidation mechanisms of limonene photosensitized by imidazole-2-carboxaldehyde

NASA Astrophysics Data System (ADS)

Rossignol, Stéphanie; Tinel, Liselotte; Aregahegn, Kifle; George, Christian

2013-04-01

Recent studies have revealed the significant formation of light absorbing materials, including imidazole and imidazole derivatives, in aqueous aerosol mimics in the presence of both ammonium sulphate and glyoxal (Galloway et al. 2009; Yu et al. 2011; Kampf et al. 2012). Besides the potential impact on radiative properties of secondary organic aerosols, our team has shown that imidazole-2-carboxaldehyde (IC) acts as a photosensitizer, initiating aerosols growth in the presence of gaseous limonene and UV/visible light (Aregahegn et al., abstract submitted). This work focuses on the characterisation of the chemical mechanisms leading to this aerosols growth, and on the major products identification. The molecular composition of organic/aqueous solutions exposed to UV/visible light and containing IC and limonene is followed in time by HR-ESI-MS/MS in positive and negative modes. Limonene consumption is followed by HPLC-UV. HR-ESI-MS/MS analyses are performed in parallel on IC/ammonium sulphate aerosols exposed to gaseous limonene and UV/visible light, in particular to assess the relevance of in solution experiments. Besides, the lifetime of the triplet state of IC in aqueous/organic solutions in the presence of different terpenes is monitored by laser photolysis experiments and compared in order to explain the first steps of the photosensitized reaction. First HR-ESI-MS/MS results show the formation of the major "traditional" limonene oxidation products (e.g., coming from gas phase limonene ozonolysis) during the irradiation of organic solutions containing IC and limonene: limononaldehyde, keto-limononaldehyde, limonic acid, limononic acid ... Hundreds of other oxygenated species are however detected, typically with a number of carbon atoms ranging from 4 to 20 and with O/C ratios ranging from 0.2 to 0.7. Monomers and dimers of limonene oxidation products are observed but species with lower carbon numbers than monomeric compounds are predominant. Moreover, and surprisingly, the production rates of all products tend to increase with reaction time and the limonene consumption presents an apparent linearity. These preliminary findings would suggest, in our experimental conditions, an oxidation mechanism initiated by a relatively slow photosensitized process e.g., electron transfer from limonene to the triplet state of IC (which formation is confirmed by laser photolysis experiments), followed by an increase of radicals in the solution leading to an extended limonene oxidation. The UV radiation, and/or the low concentration of reactants, are susceptible in our context to limit the formation of oligomers (Bateman et al. 2011) and promote fragmentation pathways. If these hypothesis need to be confirmed, this study appears to be a pertinent way to investigate the mechanisms and to assess the importance of photosensitized reactions in secondary organic aerosols growth and, possibly, in other air/condensed phase surfaces present in the environment, such as air/sea interface. Bateman, A. P., et al. (2011). Physical Chemistry Chemical Physics 13(26) 12199-12212. Galloway, M. M., et al. (2009). Atmospheric Chemistry and Physics 9(10) 3331-3345. Kampf, C. J., et al. (2012). Atmospheric Chemistry and Physics 12(14) 6323-6333. Yu, G., et al. (2011). Environmental Science & Technology 45(15) 6336-6342.

Dynamic light absorption of biomass-burning organic carbon photochemically aged under natural sunlight

NASA Astrophysics Data System (ADS)

Zhong, M.; Jang, M.

2014-02-01

Wood-burning aerosol produced under smoldering conditions was photochemically aged with different relative humidity (RH) and NOx conditions using a 104 m3 dual outdoor chamber under natural sunlight. Light absorption of organic carbon (OC) was measured over the course of photooxidation using a UV-visible spectrometer connected to an integrating sphere. At high RH, the color decayed rapidly. NOx slightly prolonged the color of wood smoke, suggesting that NOx promotes the formation of chromophores via secondary processes. Overall, the mass absorption cross section (integrated between 280 and 600 nm) of OC increased by 11-54% (except high RH) in the morning and then gradually decreased by 19-68% in the afternoon. This dynamic change in light absorption of wood-burning OC can be explained by two mechanisms: chromophore formation and sunlight bleaching. To investigate the effect of chemical transformation on light absorption, wood smoke particles were characterized using various spectrometers. The intensity of fluorescence, which is mainly related to polycyclic aromatic hydrocarbons (PAHs), rapidly decreased with time, indicating the potential bleaching of PAHs. A decline of levoglucosan concentrations evinced the change of primary organic aerosol with time. The aerosol water content measured by Fourier transform infrared spectroscopy showed that wood-burning aerosol became less hygroscopic as photooxidation proceeded. A similar trend in light absorption changes has been observed in ambient smoke aerosol originating from the 2012 County Line wildfire in Florida. We conclude that the biomass-burning OC becomes less light absorbing after 8-9 h sunlight exposure compared to fresh wood-burning OC.

Contribution of particulate brown carbon to light absorption in the rural and urban Southeast US

NASA Astrophysics Data System (ADS)

Devi, J. Jai; Bergin, Michael H.; Mckenzie, Michael; Schauer, James J.; Weber, Rodney J.

2016-07-01

Measurements of wavelength dependent aerosol light absorption coefficients were carried out as part of the Southern Oxidant and Aerosol Study (SOAS) during the summer of 2013 to determine the contribution of light absorbing organic carbon (BrC) to total aerosol light absorption in a rural location (Centreville, AL) and an urban area (Atlanta, GA). The light absorption coefficients in the near UV and visible wavelengths were measured for both ambient air, as well as ambient air heated in a thermal denuder to 200 °C to remove the semi-volatile organic compounds. Atlanta measurements show dominance of semi-volatile brown carbon with an average absorption angstrom exponent (AAE) of 1.4 before heating and about 1.0 after heating. In urban Atlanta, a decrease of about ∼35% in the light absorption coefficient at 370 nm after heating indicates that light absorbing organic compounds are a substantial fraction of the light absorption budget. Furthermore, a considerable increase in the fraction of light absorption by the semi-volatile aerosol occurs during the daytime, likely linked with photochemistry. Measurements at rural Centerville, on the other hand, do not show any major change in AAE with values before and after heating of 0.99 and 0.98, respectively. Overall the results suggest that photochemical aged urban emissions result in the presence of light absorbing BrC, while at rural locations which are dominated by aged aerosol and local biogenic emissions (based on measurements of Angstrom exponents) BrC does not significantly contribute to light absorption.

On the evaluation of air mass factors for atmospheric near-ultraviolet and visible absorption spectroscopy

NASA Technical Reports Server (NTRS)

Perliski, Lori M.; Solomon, Susan

1993-01-01

The interpretation of UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or air mass factor, of light collected by the spectrometer is understood. A simple single scattering model and a Monte Carlo radiative transfer scheme have been developed to study the effects of multiple scattering, aerosol scattering, surface albedo and refraction on air mass factors for scattered light observations. At fairly short visible wavelengths (less than about 450 nm), stratospheric air mass factors are found to be relatively insensitive to multiple scattering, surface albedo and refraction, as well as aerosol scattering by background aerosols. Longer wavelengths display greater sensitivity to refraction and aerosol scattering. Tropospheric air mass factors are found to be highly dependent on aerosol scattering, surface albedo and, at long visible wavelengths (about 650 nm), refraction. Absorption measurements of NO2 and O4 are shown to support these conclusions.

Langley Mobile Ozone Lidar: Ozone and Aerosol Atmospheric Profiling for Air Quality Research

NASA Technical Reports Server (NTRS)

De Young, Russell; Carrion, William; Ganoe, Rene; Pliutau, Denis; Gronoff, Guillaume; Berkoff, Timothy; Kuang, Shi

2017-01-01

The Langley mobile ozone lidar (LMOL) is a mobile ground-based ozone lidar system that consists of a pulsed UV laser producing two UV wavelengths of 286 and 291 nm with energy of approximately 0.2 mJ/pulse 0.2 mJ/pulse and repetition rate of 1 kHz. The 527 nm pump laser is also transmitted for aerosol measurements. The receiver consists of a 40 cm parabolic telescope, which is used for both backscattered analog and photon counting. The lidar is very compact and highly mobile. This demonstrates the utility of very small lidar systems eventually leading to space-based ozone lidars. The lidar has been validated by numerous ozonesonde launches and has provided ozone curtain profiles from ground to approximately 4 km in support of air quality field missions.

Detection of biological warfare agents using ultra violet-laser induced fluorescence LIDAR

NASA Astrophysics Data System (ADS)

Joshi, Deepti; Kumar, Deepak; Maini, Anil K.; Sharma, Ramesh C.

This review has been written to highlight the threat of biological warfare agents, their types and detection. Bacterial biological agent Bacillus anthracis (bacteria causing the disease anthrax) which is most likely to be employed in biological warfare is being discussed in detail. Standoff detection of biological warfare agents in aerosol form using Ultra violet-Laser Induced Fluorescence (UV-LIF) spectroscopy method has been studied. Range-resolved detection and identification of biological aerosols by both nano-second and non-linear femto-second LIDAR is also discussed. Calculated received fluorescence signal for a cloud of typical biological agent Bacillus globigii (Simulants of B. anthracis) at a location of ˜5.0 km at different concentrations in presence of solar background radiation has been described. Overview of current research efforts in internationally available working UV-LIF LIDAR systems are also mentioned briefly.

Aerosol radiative effect in UV, VIS, NIR, and SW spectra under haze and high-humidity urban conditions

NASA Astrophysics Data System (ADS)

Zhang, Ming; Ma, Yingying; Gong, Wei; Wang, Lunche; Xia, Xiangao; Che, Huizheng; Hu, Bo; Liu, Boming

2017-10-01

Aerosol properties derived from sun-photometric observations at Wuhan during a haze period were analyzed and used as input in a radiative transfer model to calculate the aerosol radiative effect (ARE) in ultraviolet (UV), visible (VIS), near-infrared (NIR), and shortwave (SW) spectra. The results showed that the aerosol optical depth (AOD) at 440 nm increased from 0.32 under clear-air conditions to 0.85 during common haze and 1.39 during severe haze. An unusual inverse relationship was found between the Ångström exponent (AE) and AOD during the haze period at Wuhan. Under high-humidity conditions, the fine-mode median radius of aerosols increased from 0.113 μm to approximately 0.2-0.5 μm as a result of hygroscopic growth, which led to increases in the AOD and decreases in the AE simultaneously. These changes were responsible for the inverse relationship between AE and AOD at Wuhan. The surface ARE in the UV (AREUV), VIS (AREVIS), NIR (ARENIR), and SW (ARESW) spectra changed from -4.46, -25.37, -12.15, and -41.99 W/m2 under clear-air conditions to -9.48, -53.96, -29.81, and -93.25 W/m2 during common hazy days and -12.89, -80.16, -55.17, and -148.22 W/m2 during severe hazy days, respectively, and the percentages of AREUV, AREVIS, and ARENIR in ARESW changed from 11%, 61%, and 28%-9%, 54%, and 37%, respectively. Meanwhile, the ARE efficiencies (REE) in SW varied from -206.5 W/m2 under clear-air conditions to -152.94 W/m2 during the common haze period and -131.47 W/m2 during the severe haze period. The smallest decreasing rate of the REE in NIR was associated with the increase of ARENIR. The weakened REE values were related to the strong forward scattering and weak backward scattering of fine aerosol particles with increasing size resulting from hygroscopic growth, while the variation of the single scattering albedo showed less impact. Source region analysis by back trajectories and the concentration weighted trajectory (CWT) method showed that black carbon came from nearby regions with low trajectories, and the surrounding haze areas were major sources of fine-mode particles in the haze in Wuhan.

The atmospheric transparency measured with a LIDAR system at the Telescope Array experiment

NASA Astrophysics Data System (ADS)

Tomida, Takayuki; Tsuyuguchi, Yusuke; Arai, Takahito; Benno, Takuya; Chikawa, Michiyuki; Doura, Koji; Fukushima, Masaki; Hiyama, Kazunori; Honda, Ken; Ikeda, Daisuke; Matthews, John N.; Nakamura, Toru; Oku, Daisuke; Sagawa, Hiroyuki; Tokuno, Hisao; Tameda, Yuichiro; Thomson, Gordon B.; Tsunesada, Yoshiki; Udo, Shigeharu; Ukai, Hisashi

2011-10-01

An atmospheric transparency was measured using a LIDAR with a pulsed UV laser (355 nm) at the observation site of Telescope Array in Utah, USA. The measurement at night for two years in 2007-2009 revealed that the extinction coefficient by aerosol at the ground level is 0.033-0.012+0.016km-1 and the vertical aerosol optical depth at 5 km above the ground is 0.035-0.013+0.019. A model of the altitudinal aerosol distribution was built based on these measurements for the analysis of atmospheric attenuation of the fluorescence light generated by ultra high energy cosmic rays.

Size-Resolved Composition of Organic Aerosol on the California Central Coast

NASA Astrophysics Data System (ADS)

Babila, J. E.; Depew, C. J.; Heinrich, S. E.; Zoerb, M.

2016-12-01

Organic compounds represent a significant mass fraction of submicrometer aerosol and can influence properties such as radiative forcing and cloud formation. Despite their broad importance, a complete description of particle sources and composition is lacking. Here we present measurements of solvent-extracted organic compounds in ambient aerosol in San Luis Obispo, CA. Ambient particles were sampled and size segregated with a micro-orifice uniform deposit impactor (MOUDI). Water and methanol soluble organic carbon was characterized with electrospray ionization mass spectrometry (ESI-MS) and UV/Vis spectroscopy. Particle composition and influences from local and regional sources on the organic fraction will be discussed.

Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PubMed Central

Svensson, Christian R.; Messing, Maria E.; Lundqvist, Martin; Schollin, Alexander; Deppert, Knut; Pagels, Joakim H.; Rissler, Jenny; Cedervall, Tommy

2013-01-01

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs. PMID:24086363

A four parameter optimization and troubleshooting of a RPLC - charged aerosol detection stability indicating method for determination of S-lysophosphatidylcholines in a phospholipid formulation.

PubMed

Tam, James; Ahmad, Imad A Haidar; Blasko, Andrei

2018-06-05

A four parameter optimization of a stability indicating method for non-chromophoric degradation products of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1-stearoyl-sn-glycero-3-phosphocholine and 2-stearoyl-sn-glycero-3-phosphocholine was achieved using a reverse phase liquid chromatography-charged aerosol detection (RPLC-CAD) technique. Using the hydrophobic subtraction model of selectivity, a core-shell, polar embedded RPLC column was selected followed by gradient-temperature optimization, resulting in ideal relative peak placements for a robust, stability indicating separation. The CAD instrument parameters, power function value (PFV) and evaporator temperature were optimized for lysophosphatidylcholines to give UV absorbance detector-like linearity performance within a defined concentration range. The two lysophosphatidylcholines gave the same response factor in the selected conditions. System specific power function values needed to be set for the two RPLC-CAD instruments used. A custom flow-divert profile, sending only a portion of the column effluent to the detector, was necessary to mitigate detector response drifting effects. The importance of the PFV optimization for each instrument of identical build and how to overcome recovery issues brought on by the matrix effects from the lipid-RP stationary phase interaction is reported. Copyright © 2018 Elsevier B.V. All rights reserved.

Aqueous aerosol SOA formation: impact on aerosol physical properties.

PubMed

Woo, Joseph L; Kim, Derek D; Schwier, Allison N; Li, Ruizhi; McNeill, V Faye

2013-01-01

Organic chemistry in aerosol water has recently been recognized as a potentially important source of secondary organic aerosol (SOA) material. This SOA material may be surface-active, therefore potentially affecting aerosol heterogeneous activity, ice nucleation, and CCN activity. Aqueous aerosol chemistry has also been shown to be a potential source of light-absorbing products ("brown carbon"). We present results on the formation of secondary organic aerosol material in aerosol water and the associated changes in aerosol physical properties from GAMMA (Gas-Aerosol Model for Mechanism Analysis), a photochemical box model with coupled gas and detailed aqueous aerosol chemistry. The detailed aerosol composition output from GAMMA was coupled with two recently developed modules for predicting a) aerosol surface tension and b) the UV-Vis absorption spectrum of the aerosol, based on our previous laboratory observations. The simulation results suggest that the formation of oligomers and organic acids in bulk aerosol water is unlikely to perturb aerosol surface tension significantly. Isoprene-derived organosulfates are formed in high concentrations in acidic aerosols under low-NO(x) conditions, but more experimental data are needed before the potential impact of these species on aerosol surface tension may be evaluated. Adsorption of surfactants from the gas phase may further suppress aerosol surface tension. Light absorption by aqueous aerosol SOA material is driven by dark glyoxal chemistry and is highest under high-NO(x) conditions, at high relative humidity, in the early morning hours. The wavelength dependence of the predicted absorption spectra is comparable to field observations and the predicted mass absorption efficiencies suggest that aqueous aerosol chemistry can be a significant source of aerosol brown carbon under urban conditions.

Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

NASA Astrophysics Data System (ADS)

Alanen, Jenni; Simonen, Pauli; Saarikoski, Sanna; Timonen, Hilkka; Kangasniemi, Oskari; Saukko, Erkka; Hillamo, Risto; Lehtoranta, Kati; Murtonen, Timo; Vesala, Hannu; Keskinen, Jorma; Rönkkö, Topi

2017-07-01

Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM) chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6-268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA) formation potential was measured to be 9-20 mg kgfuel-1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize - more than half an hour - which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission source and system temperatures. Sulfate was measured to have the highest evaporation temperature, and nitrate had the lowest. The evaporation temperature of ammonium depended on the fractions of nitrate and sulfate in the particles. The average volatility of the total aged particles was measured to be lower than that of primary particles, indicating better stability of the aged natural gas engine-emitted aerosol in the atmosphere. According to the results of this study, the exhaust of a natural gas engine equipped with a catalyst forms secondary aerosol when the atmospheric ages in a PAM chamber are several days long. The secondary aerosol matter has different physical characteristics from those of primary particulate emissions.

Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition

PubMed Central

Sathasivam, Sanjayan; Bhachu, Davinder S.; Lu, Yao; Chadwick, Nicholas; Althabaiti, Shaeel A.; Alyoubi, Abdulrahman O.; Basahel, Sulaiman N.; Carmalt, Claire J.; Parkin, Ivan P.

2015-01-01

Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm3/V.s) and concentration (×1019 cm−3). XPS indicated the presence of both W6+ and W4+ in the TiO2 matrix, with the substitutional doping of W4+ inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2. PMID:26042724

Science Objectives of EOS-Aura's Ozone Monitoring Instrument (OMI)

NASA Technical Reports Server (NTRS)

Levelt, P. F.; Veefkind, J. P.; Stammes, P.; Hilsenrath, E.; Bhartia, P. K.; Chance, K. V.; Leppelmeier, G. W.; Maelkki, A.; Bhartia, Pawan (Technical Monitor)

2002-01-01

OMI is a UV/VIS nadir solar backscatter spectrograph, which provides near global coverage in one day with a spatial resolution of 13 x 24 sq km. OMI is a new instrument, with a heritage from the European satellite instruments GOME, GOMOS and SCIAMACHY. OMI's unique capabilities for measuring important trace gases with a small footprint and daily global coverage, in conjunction with the other Aura instruments, will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI will measure solar irradiance and Earth radiances in the wavelength range of 270 to 500 nm with spectral resolution of about 0.5 nm and a spectral sampling of about 2-3 per FWHM. From these observations, total columns of O3, NO2, BrO and SO2 will be derived from the back-scattered solar radiance using differential absorption spectroscopy (DOAS). The TOMS total ozone record will also be continued by employing the well established TOMS algorithm. Because of the high accuracy and spatial resolution of the measurements, a good estimate of tropospheric amounts of ozone and NO2 are expected. Ozone profiles will be derived using the optimal estimation method. The spectral aerosol optical depth will be determined from measurements between 340 and 500 nm. This will provide information on aerosol concentration, aerosol size distribution and aerosol type. This wavelength range makes it possible to retrieve aerosol information over both land and sea. OMI observations will also allow retrievals of cloud coverage and cloud heights. From these products, the UV-B flux at the surface can then be derived with high spatial resolution.

Assessing Impact of Aerosol Intercontinental Transport on Regional Air Quality and Climate: What Satellites Can Help

NASA Technical Reports Server (NTRS)

Yu, Hongbin

2011-01-01

Mounting evidence for intercontinental transport of aerosols suggests that aerosols from a region could significantly affect climate and air quality in downwind regions and continents. Current assessment of these impacts for the most part has been based on global model simulations that show large variability. The aerosol intercontinental transport and its influence on air quality and climate involve many processes at local, regional, and intercontinental scales. There is a pressing need to establish modeling systems that bridge the wide range of scales. The modeling systems need to be evaluated and constrained by observations, including satellite measurements. Columnar loadings of dust and combustion aerosols can be derived from the MODIS and MISR measurements of total aerosol optical depth and particle size and shape information. Characteristic transport heights of dust and combustion aerosols can be determined from the CALIPSO lidar and AIRS measurements. CALIPSO liar and OMI UV technique also have a unique capability of detecting aerosols above clouds, which could offer some insights into aerosol lofting processes and the importance of above-cloud transport pathway. In this presentation, I will discuss our efforts of integrating these satellite measurements and models to assess the significance of intercontinental transport of dust and combustion aerosols on regional air quality and climate.

NARSTO PAC2001 CONVAIR PM OZONE MET DATA

Atmospheric Science Data Center

2018-04-09

NARSTO PAC2001 CONVAIR PM OZONE MET DATA Project Title:  NARSTO Discipline:  Tropospheric Composition Field Campaigns Aerosols ... Temperature Probe Humidity Probe Wind Sensor UV Ozone Detector Optical Counter Location:  Lower Fraser ...

Absorbing Aerosols Above Cloud: Detection, Quantitative Retrieval, and Radiative Forcing from Satellite-based Passive Sensors

NASA Astrophysics Data System (ADS)

Jethva, H.; Torres, O.; Remer, L. A.; Bhartia, P. K.

2012-12-01

Light absorbing particles such as carbonaceous aerosols generated from biomass burning activities and windblown dust particles can exert a net warming effect on climate; the strength of which depends on the absorption capacity of the particles and brightness of the underlying reflecting background. When advected over low-level bright clouds, these aerosols absorb the cloud reflected radiation from ultra-violet (UV) to shortwave-IR (SWIR) and makes cloud scene darker-a phenomenon commonly known as "cloud darkening". The apparent "darkening" effect can be seen by eyes in satellite images as well as quantitatively in the spectral reflectance measurements made by space borne sensors over regions where light absorbing carbonaceous and dust aerosols overlay low-level cloud decks. Theoretical radiative transfer simulations support the observational evidence, and further reveal that the strength of the cloud darkening and its spectral signature (or color ratio) between measurements at two wavelengths are a bi-function of aerosol and cloud optical thickness (AOT and COT); both are measures of the total amount of light extinction caused by aerosols and cloud, respectively. Here, we developed a retrieval technique, named as the "color ratio method" that uses the satellite measurements at two channels, one at shorter wavelength in the visible and one at longer wavelength in the shortwave-IR for the simultaneous retrieval of AOT and COT. The present technique requires assumptions on the aerosol single-scattering albedo and aerosol-cloud separation which are supplemented by the Aerosol Robotic Network (AERONET) and space borne CALIOP lidar measurements. The retrieval technique has been tested making use of the near-UV and visible reflectance observations made by the Ozone Monitoring Instrument (OMI) and Moderate Resolution Imaging Spectroradiometer (MODIS) for distinct above-cloud smoke and dust aerosol events observed seasonally over the southeast and tropical Atlantic Ocean, respectively. This study constitutes the first attempt to use non-polarized and non-lidar reflectance observations-both of them shown to have above-cloud aerosols retrieval capability, to retrieve above-cloud AOT by a passive non-polarized sensor. The uncertainty analysis suggests that the present method should retrieve above-cloud AOT within -10% to 50% which mainly arises due to uncertainty associated with the single-scattering albedo assumption. Although, currently tested by making use of OMI and MODIS measurements, the present color ratio method can be equally applied to the other satellite measurements that carry similar or near-by channels in VIS region of the spectrum such as MISR and NPP/VIIRS. The capability of quantifying the above-cloud aerosol load will facilitate several aspects of cloud-aerosol interaction research such as estimation of the direct radiative forcing of aerosols above clouds; the sign of which can be opposite (warming) to cloud-free aerosol forcing (cooling), aerosol transport, indirect effects of aerosols on clouds, and hydrological cycle.

Methane photochemistry and methane production on Neptune

NASA Technical Reports Server (NTRS)

Romani, P. N.; Atreya, S. K.

1988-01-01

The Neptune stratosphere's methane photochemistry is presently studied by means of a numerical model in which the observed mixing ratio of methane prompts photolysis near the CH4 homopause. Haze generation by methane photochemistry has its basis in the formation of hydrocarbon ices and polyacetylenes; the hazes can furnish the requisite aerosol haze at the appropriate pressure levels required by observations of Neptune in the visible and near-IR. Comparisons of model predictions with Uranus data indicate a lower ratio of polyacetylene production to hydrocarbon ice, as well as a lower likelihood of UV postprocessing of the acetylene ice to polymers on Neptune, compared to Uranus.

Utilization of O4 slant column density to derive aerosol layer height from a spaceborne UV-visible hyperspectral sensor: sensitivity and case study

NASA Astrophysics Data System (ADS)

Park, S. S.; Kim, J.; Lee, H.; Torres, O.; Lee, K.-M.; Lee, S. D.

2015-03-01

The sensitivities of oxygen-dimer (O4) slant column densities (SCDs) to changes in aerosol layer height are investigated using simulated radiances by a radiative transfer model, Linearized Discrete Ordinate Radiative Transfer (LIDORT), and Differential Optical Absorption Spectroscopy (DOAS) technique. The sensitivities of the O4 SCDs to aerosol types and optical properties are also evaluated and compared. Among the O4 absorption bands at 340, 360, 380, and 477 nm, the O4 absorption band at 477 nm is found to be the most suitable to retrieve the aerosol effective height. However, the O4 SCD at 477 nm is significantly influenced not only by the aerosol layer effective height but also by aerosol vertical profiles, optical properties including single scattering albedo (SSA), aerosol optical depth (AOD), and surface albedo. Overall, the error of the retrieved aerosol effective height is estimated to be 414 m (16.5%), 564 m (22.4%), and 1343 m (52.5%) for absorbing, dust, and non-absorbing aerosol, respectively, assuming knowledge on the aerosol vertical distribution type. Using radiance data from the Ozone Monitoring Instrument (OMI), a new algorithm is developed to derive the aerosol effective height over East Asia after the determination of the aerosol type and AOD from the MODerate resolution Imaging Spectroradiometer (MODIS). The retrieved aerosol effective heights are lower by approximately 300 m (27 %) compared to those obtained from the ground-based LIDAR measurements.

Ozone and NO2 measurements from Aberystwyth and Lerwick

NASA Technical Reports Server (NTRS)

Bartlett, L. M.; Vaughan, Geraint

1994-01-01

Measurements of the total column of ozone and NO2 were obtained by a SAOZ UV/Visible spectrometer at Aberystwyth (52.4 deg N, 4.1 deg W) and Lerwick (60.1 deg N, 1.2 deg W) during the period March 1991 - April 1992. NO2 measurements show a marked decrease in 1992 compared with 1991, due to the effect of aerosols from Mt. Pinatubo. Ozone measurements appear to have been affected by the aerosols - comparisons with both Dobson and TOMS measurements are presented.

Tropical intercontinental optical measurement network of aerosol, precipitable water and total column ozone

NASA Technical Reports Server (NTRS)

Holben, B. N.; Tanre, D.; Reagan, J. A.; Eck, T. F.; Setzer, A.; Kaufman, Y. A.; Vermote, E.; Vassiliou, G. D.; Lavenu, F.

1992-01-01

A new generation of automatic sunphotometers is used to systematically monitor clear sky total column aerosol concentration and optical properties, precipitable water and total column ozone diurnally and annually in West Africa and South America. The instruments are designed to measure direct beam sun, solar aureole and sky radiances in nine narrow spectral bands from the UV to the near infrared on an hourly basis. The instrumentation and the algorithms required to reduce the data for subsequent analysis are described.

Condensed-Phase Photochemical Processes in Titan's Aerosols and Surface: The Role of Longer Wavelength Photochemistry

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Jacovi, Ronen; Lignell, Antti; Couturier, Isabelle

2011-01-01

We will discuss photochemical properties of Titan's organic molecules in the condensed phase as solid aerosols or surface material, from small linear polyyenes (polyacetylenes and polycyanoacetylenes) such as C2H2, C4N2, HC5N, etc. In particular we will focus on photochemistry caused by longer wavelength UV-VIS photons (greater than 250 nm) photons that make it through Titan's atmosphere to the haze region (approximately 100 km) and on to the surface of Titan.

A perspective on SOA generated in aerosol water from glyoxal and methylglyoxal and its impacts on climate-relevant aerosol properties

NASA Astrophysics Data System (ADS)

Sareen, N.; McNeill, V. F.

2011-12-01

In recent years, glyoxal and methylglyoxal have emerged to be potentially important SOA precursors with significant implications for climate-related aerosol properties. Here we will discuss how the chemistry of these and similar organic compounds in aerosol water can affect the aerosol optical and cloud formation properties. Aqueous-phase SOA production from glyoxal and methylglyoxal is a potential source of strongly light-absorbing organics, or "brown carbon". We characterized the kinetics of brown carbon formation from these precursors in mixtures of ammonium sulfate and water using UV-Vis spectrophotometry. This mechanism has been incorporated into a photochemical box model with coupled gas phase-aqueous aerosol chemistry. Methylglyoxal and related compounds also may impact an aerosol's ability to act as a cloud condensation nucleus. We recently showed via pendant drop tensiometry and aerosol chamber studies that uptake of methylglyoxal from the gas phase driven by aqueous-phase oligomerization chemistry is a potentially significant, previously unidentified source of surface-active organic material in aerosols. Results from pendant drop tensiometry showed significantly depressed surface tension in methylglyoxal-ammonium sulfate solutions. We further found that ammonium sulfate particles exposed to gas-phase methylglyoxal in a 3.5 m3 aerosol reaction chamber activate into cloud droplets at sizes up to 15% lower at a given supersaturation than do pure ammonium sulfate particles. The observed enhancement exceeds that predicted based on Henry's Law and our measurements of surface tension depression in bulk solutions, suggesting that surface adsorption of methylglyoxal plays a role in determining CCN activity. Methylglyoxal and similar gas-phase surfactants may be an important and overlooked source of enhanced CCN activity in the atmosphere. To characterize the SOA products formed in these solutions, an Aerosol Chemical Ionization Mass Spectrometer (CIMS) was used. These compounds included (hemi)acetals, aldol condensation products, and oligomeric species up to 759 amu. Since these products are vulnerable to oxidants such as O3 and OH in the atmosphere, kinetic studies were conducted to study their affect upon exposure to O3 and OH. Custom-designed flow tube reactors were coupled with the Aerosol-CIMS to monitor aerosol composition, and consequently this data was used to determine reactive uptake coefficients (γO3~10-8 and γOH~ 10-6). Additionally, the lifetime of these SOA species in the atmosphere can be estimated and if these time scales are sufficiently long, they may affect aerosol optical properties. The effect of oxidation on the optical properties is also currently being tested by collecting aerosol particles before and after oxidation on a quartz window and testing changes in absorption using the UV-Vis spectrophotometer. The results of all these studies will be integrated to understand the role of methylglyoxal as a SOA precursor and the effect on various aerosol properties, and this will be used as a model system to predict the fate of similar organics in the atmosphere.

NARSTO PAC2001 CESSNA VOC PM OZONE MET DATA

Atmospheric Science Data Center

2018-04-09

NARSTO PAC2001 CESSNA VOC PM OZONE MET DATA Project Title:  NARSTO Discipline:  Tropospheric Composition Field Campaigns Aerosols ... Temperature Probe Humidity Probe Wind Sensor UV Ozone Detector Optical Counter GC Location:  Lower Fraser ...

Detection of biological warfare agents using ultra violet-laser induced fluorescence LIDAR.

PubMed

Joshi, Deepti; Kumar, Deepak; Maini, Anil K; Sharma, Ramesh C

2013-08-01

This review has been written to highlight the threat of biological warfare agents, their types and detection. Bacterial biological agent Bacillus anthracis (bacteria causing the disease anthrax) which is most likely to be employed in biological warfare is being discussed in detail. Standoff detection of biological warfare agents in aerosol form using Ultra violet-Laser Induced Fluorescence (UV-LIF) spectroscopy method has been studied. Range-resolved detection and identification of biological aerosols by both nano-second and non-linear femto-second LIDAR is also discussed. Calculated received fluorescence signal for a cloud of typical biological agent Bacillus globigii (Simulants of B. anthracis) at a location of ~5.0 km at different concentrations in presence of solar background radiation has been described. Overview of current research efforts in internationally available working UV-LIF LIDAR systems are also mentioned briefly. Copyright © 2013 Elsevier B.V. All rights reserved.

Introduction of the new concept: Potential Aerosol Mass (PAM) for Inorganic and Organic Secondary Aerosol

NASA Astrophysics Data System (ADS)

Kang, E.; Root, M. J.; Brune, W. H.

2006-12-01

A new concept, the Potential Aerosol Mass (PAM), is being developed and tested in the laboratory with the goal of deploying instruments to measure PAM in the atmosphere. PAM can be defined as the maximum aerosol mass that precursor gases can be oxidized to form. In the PAM concept, all precursor gases are oxidized to low volatile compounds with excessive amount of oxidants in a small continuous-flow Teflon cylinder, resulting in aerosol formation. Excessive amounts of OH and O3 are produced by a UV light that shines into the Teflon chamber. For our studies, the aerosol mass is then detected with a real-time aerosol mass measurement instrument, the Rupprecht and Patashnick Tapered Element Oscillating Microbalance (TEOM) and Filter Dynamic Measurement System (FDMS). As a test of the system, SO2 was oxidized to sulfate; the measured and calculated conversion ratios of sulfate aerosol mass to SO2 mass agree to within 10%. We will discuss the results of a series of laboratory tests that have been conducted with α-pinene to determine the variables that most affect its Secondary Organic Aerosol (SOA) yield. We will also discuss the results of some atmospheric measurement tests made at a site on the Penn State University campus.

A simplified guide for charged aerosol detection of non-chromophoric compounds-Analytical method development and validation for the HPLC assay of aerosol particle size distribution for amikacin.

PubMed

Soliven, Arianne; Haidar Ahmad, Imad A; Tam, James; Kadrichu, Nani; Challoner, Pete; Markovich, Robert; Blasko, Andrei

2017-09-05

Amikacin, an aminoglycoside antibiotic lacking a UV chromophore, was developed into a drug product for delivery by inhalation. A robust method for amikacin assay analysis and aerosol particle size distribution (aPSD) determination, with comparable performance to the conventional UV detector was developed using a charged aerosol detector (CAD). The CAD approach involved more parameters for optimization than UV detection due to its sensitivity to trace impurities, non-linear response and narrow dynamic range of signal versus concentration. Through careful selection of the power transformation function value and evaporation temperature, a wider linear dynamic range, improved signal-to-noise ratio and high repeatability were obtained. The influences of mobile phase grade and glassware binding of amikacin during sample preparation were addressed. A weighed (1/X 2 ) least square regression was used for the calibration curve. The limit of quantitation (LOQ) and limit of detection (LOD) for this method were determined to be 5μg/mL and 2μg/mL, respectively. The method was validated over a concentration range of 0.05-2mg/mL. The correlation coefficient for the peak area versus concentration was 1.00 and the y-intercept was 0.2%. The recovery accuracies of triplicate preparations at 0.05, 1.0, and 2.0mg/mL were in the range of 100-101%. The relative standard deviation (S rel ) of six replicates at 1.0mg/mL was 1%, and S rel of five injections at the limit of quantitation was 4%. A robust HPLC-CAD method was developed and validated for the determination of the aPSD for amikacin. The CAD method development produced a simplified procedure with minimal variability in results during: routine operation, transfer from one instrument to another, and between different analysts. Copyright © 2017 Elsevier B.V. All rights reserved.

Vertical distribution of Martian aerosols from SPICAM/Mars-Express limb observations

NASA Astrophysics Data System (ADS)

Fedorova, A.; Korablev, O.; Bertaux, J.-L.; Rodin, A.; Perrier, S.; Moroz, V. I.

Limb spectroscopic observations provide invaluable information about vertical distribution of main atmospheric components in the Martian atmosphere, in particular vertical distribution and structure of aerosols, which play an important role in the heat balance of the planet. Only limited set of successful limb spectroscopic observations have been carried out on Mars so far, including those by MGS/TES spectrometer and Thermoscan and Auguste experiments of Phobos mission. Currently SPICAM instrument onboard Mars-Express spacecraft has accomplished several sequences of limb observations. First analysis of limb sounding data received by SPICAM IR and UV channels, which imply the presence of fine, deep, optically thin aerosol fraction extended over broad range of altitudes, is presented.

Space observations of aerosols and ozone; Proceedings of the Topical Meeting, Ottawa, Canada, May 16-June 2, 1982

NASA Technical Reports Server (NTRS)

Mccormick, M. P. (Editor); Lovill, J. E.

1982-01-01

The measurement of aerosols from space is discussed, taking into account the role of aerosols in climate, instrumentation and further measurement systems, retrieval procedures, measurements and observations, ground truth measurements, and effects on remote sensing and on climate. Aspects of ozone variability in the middle atmosphere are explored, giving attention to the quasi-biennial oscillation in equatorial stratospheric temperatures and total ozone, global pictures on the ozone field from high altitudes from DE-1, measurements of atmospheric ozone from aircraft and from balloons, a mesospheric ozone profile at sunset, periodic and aperiodic ozone variations in the middle and upper stratosphere, solar eclipse induced variations in mesospheric ozone concentrations, and solar UV and ozone balloon measurements. The determination of aerosol optical depth is considered along with a method for estimating cross radiance.

Volcanic-aerosol-induced changes in stratospheric ozone following the eruption of Mount Pinatubo

NASA Technical Reports Server (NTRS)

Grant, W. B.; Browell, E. V.; Fishman, J.; Brackett, V. G.; Fenn, M. A.; Butler, C. F.; Nganga, D.; Minga, A.; Cros, B.; Mayor, S. D.

1994-01-01

Measurements of lower stratospheric ozone in the Tropics using electrochemical concentrations cell (ECC) sondes and the airborne UV Differential Absorption Lidar (DIAL) system after the eruption of Mt. Pinatubo are compared with the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and ECC sonde measurements from below the eruption to determine what changes have occurred as a result. Aerosol data from the Advanced Very High Resolution Radiometer (AVHRR) and the visible and IR wavelengths of the lidar system are used to examine the relationship between aerosols and ozone changes. Ozone decreases of 30 percent at altitudes between 19 and 26 km, partial column (16-28 km) decreases of about 27 D.U., and slight increases (5.4 D.U.) between 28 and 31 km are found in comparison with SAGE 2 climatological values.

Global structure and composition of the martian atmosphere with SPICAM on Mars express

NASA Astrophysics Data System (ADS)

Bertaux, Jean-Loup; Korablev, O.; Fonteyn, D.; Guibert, S.; Chassefière, E.; Lefèvre, F.; Dimarellis, E.; Dubois, J. P.; Hauchecorne, A.; Cabane, M.; Rannou, P.; Levasseur-Regourd, A. C.; Cernogora, G.; Quémerais, E.; Hermans, C.; Kockarts, G.; Lippens, C.; de Maziere, M.; Moreau, D.; Muller, C.; Neefs, E.; Simon, P. C.; Forget, F.; Hourdin, F.; Talagrand, O.; Moroz, V. I.; Rodin, A.; Sandel, B.; Stern, A.

SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) Light, a light-weight (4.7 kg) UV-IR instrument to be flown on Mars Express orbiter, is dedicated to the study of the atmosphere and ionosphere of Mars. A UV spectrometer (118-320 nm, resolution 0.8 nm) is dedicated to nadir viewing, limb viewing and vertical profiling by stellar and solar occultation (3.8 kg). It addresses key issues about ozone, its coupling with H2O, aerosols, atmospheric vertical temperature structure and ionospheric studies. UV observations of the upper atmosphere will allow studies of the ionosphere through the emissions of CO, CO+, and CO2+, and its direct interaction with the solar wind. An IR spectrometer (1.0-1.7 μm, resolution 0.5-1.2 nm) is dedicated primarily to nadir measurements of H2O abundances simultaneously with ozone measured in the UV, and to vertical profiling during solar occultation of H2O, CO2, and aerosols. The SPICAM Light near-IR sensor employs a pioneering technology acousto-optical tunable filter (AOTF), leading to a compact and light design. Overall, SPICAM Light is an ideal candidate for future orbiter studies of Mars, after Mars Express, in order to study the interannual variability of martian atmospheric processes. The potential contribution to a Mars International Reference Atmosphere is clear.

Aerosol Particle Shape and Radiative Coupling in a Three Dimensional Titan GCM

NASA Astrophysics Data System (ADS)

Larson, Erik J.; Toon, O. B.; Friedson, A. J.; West, R. A.

2010-10-01

Understanding the aerosols on Titan is imperative for understanding the atmosphere as a whole. The aerosols affect the albedo, optical depth, as well as heating and cooling rates which in turn affect the circulation on Titan leading to feedback with the aerosol distribution. Correctly representing the aerosols in atmospheric models is crucial to understanding this atmosphere. Friedson et al. (2009, A global climate model of Titan's atmosphere and surface. Planet. SpaceSci. 57, 1931-1949.) produced a three-dimensional model for Titan using the NCAR CAM3 model, to which we coupled the aerosol microphysics model CARMA. We have also made the aerosols produced by CARMA interactive with the radiation code in CAM. We compare simulations with radiatively interactive aerosols with those using a prescribed aerosol radiative effect. Preliminary results show that this model is capable of reproducing the seasonal changes in aerosols on Titan and many of the associated phenomena. For instance, the radiatively interactive aerosols are lofted by winds more in the summer hemisphere than the non-radiatively interactive aerosols, which is necessary to reproduce the observed seasonal cycle of the albedo. We compare simulations using spherical particles to simulations using fractal aggregate particles, which are expected from laboratory and observational data. Fractal particles have higher absorption in the UV, slower fall velocities and faster coagulation rates than equivalent mass spherical particles. We compare model simulations with observational data from the Cassini and Huygens missions.

Retrieval of aerosol properties and water leaving radiance from multi-angle spectro-polarimetric measurement over coastal waters

NASA Astrophysics Data System (ADS)

Gao, M.; Zhai, P.; Franz, B. A.; Hu, Y.; Knobelspiesse, K. D.; Xu, F.; Ibrahim, A.

2017-12-01

Ocean color remote sensing in coastal waters remains a challenging task due to the complex optical properties of aerosols and ocean water properties. It is highly desirable to develop an advanced ocean color and aerosol retrieval algorithm for coastal waters, to advance our capabilities in monitoring water quality, improve our understanding of coastal carbon cycle dynamics, and allow for the development of more accurate circulation models. However, distinguishing the dissolved and suspended material from absorbing aerosols over coastal waters is challenging as they share similar absorption spectrum within the deep blue to UV range. In this paper we report a research algorithm on aerosol and ocean color retrieval with emphasis on coastal waters. The main features of our algorithm include: 1) combining co-located measurements from a hyperspectral ocean color instrument (OCI) and a multi-angle polarimeter (MAP); 2) using the radiative transfer model for coupled atmosphere and ocean system (CAOS), which is based on the highly accurate and efficient successive order of scattering method; and 3) incorporating a generalized bio-optical model with direct accounting of the total absorption of phytoplankton, CDOM and non-algal particles(NAP), and the total scattering of phytoplankton and NAP for improved description of ocean light scattering. The non-linear least square fitting algorithm is used to optimize the bio-optical model parameters and the aerosol optical and microphysical properties including refractive indices and size distributions for both fine and coarse modes. The retrieved aerosol information is used to calculate the atmospheric path radiance, which is then subtracted from the OCI observations to obtain the water leaving radiance contribution. Our work aims to maximize the use of available information from the co-located dataset and conduct the atmospheric correction with minimal assumptions. The algorithm will contribute to the success of current MAP instruments, such as the Research Scanning Polarimeter (RSP), and future ocean color missions, such as the Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission, by enabling retrieval of ocean biogeochemical properties under optically-complex atmospheric and oceanic conditions.

GOME-2 Tropospheric Ozone Profile Retrievals from Joint UV/Visible Measurement

NASA Astrophysics Data System (ADS)

Liu, X.; Zoogman, P.; Chance, K.; Cai, Z.; Nowlan, C. R.; Huang, G.; Gonzalez Abad, G.

2016-12-01

It has been shown from sensitivity studies that adding visible measurements in the Chappuis ozone band to UV measurements in the Hartley/Huggins ozone bands can significantly enhance retrieval sensitivity to lower tropospheric ozone from backscattered solar radiances due to deeper photon penetration in the visible to the surface than in the ultraviolet. The first NASA EVI (Earth Venture Instrument) TEMPO (Tropospheric Emissions: Monitoring of Pollution) instrument is being developed to measure backscattered solar radiation in two channels ( 290-490 and 540-740 nm) and make atmospheric pollution measurements over North America from the Geostationary orbit. However, this retrieval enhancement has yet to be demonstrated from existing measurements due to the weak ozone absorption in the visible and strong interferences from surface reflectance and aerosols and the requirement of accurate radiometric calibration across different spectral channels. We present GOME-2 retrievals from joint UV/visible measurements using the SAO ozone profile retrieval algorithm, to directly explore the retrieval improvement in lower tropospheric ozone from additional visible measurements. To reduce the retrieval interference from surface reflectance, we add characterization of surface spectral reflectance in the visible based on combining EOFs (Empirical Orthogonal Functions) derived from ASTER and other surface reflectance spectra with MODIS BRDF climatology into the ozone profile algorithm. The impacts of various types of aerosols and surface BRDF on the retrievals will be investigated. In addition, we will also perform empirical radiometric calibration of the GOME-2 data based on radiative transfer simulations. We will evaluate the retrieval improvement of joint UV/visible retrieval over the UV retrieval based on fitting quality and validation against ozonesonde observations.

Applying UV cameras for SO2 detection to distant or optically thick volcanic plumes

USGS Publications Warehouse

Kern, Christoph; Werner, Cynthia; Elias, Tamar; Sutton, A. Jeff; Lübcke, Peter

2013-01-01

Ultraviolet (UV) camera systems represent an exciting new technology for measuring two dimensional sulfur dioxide (SO2) distributions in volcanic plumes. The high frame rate of the cameras allows the retrieval of SO2 emission rates at time scales of 1 Hz or higher, thus allowing the investigation of high-frequency signals and making integrated and comparative studies with other high-data-rate volcano monitoring techniques possible. One drawback of the technique, however, is the limited spectral information recorded by the imaging systems. Here, a framework for simulating the sensitivity of UV cameras to various SO2 distributions is introduced. Both the wavelength-dependent transmittance of the optical imaging system and the radiative transfer in the atmosphere are modeled. The framework is then applied to study the behavior of different optical setups and used to simulate the response of these instruments to volcanic plumes containing varying SO2 and aerosol abundances located at various distances from the sensor. Results show that UV radiative transfer in and around distant and/or optically thick plumes typically leads to a lower sensitivity to SO2 than expected when assuming a standard Beer–Lambert absorption model. Furthermore, camera response is often non-linear in SO2 and dependent on distance to the plume and plume aerosol optical thickness and single scatter albedo. The model results are compared with camera measurements made at Kilauea Volcano (Hawaii) and a method for integrating moderate resolution differential optical absorption spectroscopy data with UV imagery to retrieve improved SO2 column densities is discussed.

Jupiter's Polar Haze

NASA Astrophysics Data System (ADS)

Carlson, B. E.

1997-07-01

The nature and distribution of stratospheric aerosols in the polar regions of Jupiter are investigated using a combination of ground-based, Hubble Space Telescope (HST), and Voyager IRIS measurements. Of particular interest are the connections between the enhanced UV absorption in the polar regions and the bright polar hoods evident in methane band images and the connections between the aerosol, the infrared "hot spot", and the auroras. Spatial maps of the hydrocarbon emissions constructed from the Voyager IRIS measurements reveal enhanced acetylene emission coincident with the region of enhanced methane emission but morphologically distinct from the region of enhanced ethane emission. This finding confirms the existence of altitude- dependent hydrocarbon chemistry. Ground-based and HST data reveal the presence of longitudinal structure in the latitudinal distribution of the aerosols (i.e., break-down in zonal symmetry) apparently associated with circulation anomalies induced by the polar hot spot. In addition, the HST data reveal a change in the aerosol properties (e.g., phase function) in the vicinity of the hot spot while ruling out changes in their height and/or optical depth distribution. The HST data also reveal differential UV absorption coincident with the aurora strengthening the connection between aerosol formation/hydrocarbon chemistry and the aurora. The spectral dependence of this absorption suggests enhancements of the higher order hydrocarbons (e.g., benzene). The mismatch in spatial resolution between infrared (Voyager IRIS/ground-based IRTF) and HST measurements coupled with the change in morphology of the hot spot as revealed by the structure of the methane/acetylene emission versus that of the ethane emission suggests the existence of more complex spatial structure and additional thermal emission anomalies associated with auroral processes unresolved by current infrared measurements

Evaluation of Machine Learning Algorithms for Classification of Primary Biological Aerosol using a new UV-LIF spectrometer

NASA Astrophysics Data System (ADS)

Ruske, S. T.; Topping, D. O.; Foot, V. E.; Kaye, P. H.; Stanley, W. R.; Morse, A. P.; Crawford, I.; Gallagher, M. W.

2016-12-01

Characterisation of bio-aerosols has important implications within Environment and Public Health sectors. Recent developments in Ultra-Violet Light Induced Fluorescence (UV-LIF) detectors such as the Wideband Integrated bio-aerosol Spectrometer (WIBS) and the newly introduced Multiparameter bio-aerosol Spectrometer (MBS) has allowed for the real time collection of fluorescence, size and morphology measurements for the purpose of discriminating between bacteria, fungal Spores and pollen. This new generation of instruments has enabled ever-larger data sets to be compiled with the aim of studying more complex environments, yet the algorithms used for specie classification remain largely invalidated. It is therefore imperative that we validate the performance of different algorithms that can be used for the task of classification, which is the focus of this study. For unsupervised learning we test Hierarchical Agglomerative Clustering with various different linkages. For supervised learning, ten methods were tested; including decision trees, ensemble methods: Random Forests, Gradient Boosting and AdaBoost; two implementations for support vector machines: libsvm and liblinear; Gaussian methods: Gaussian naïve Bayesian, quadratic and linear discriminant analysis and finally the k-nearest neighbours algorithm. The methods were applied to two different data sets measured using a new Multiparameter bio-aerosol Spectrometer. We find that clustering, in general, performs slightly worse than the supervised learning methods correctly classifying, at best, only 72.7 and 91.1 percent for the two data sets. For supervised learning the gradient boosting algorithm was found to be the most effective, on average correctly classifying 88.1 and 97.8 percent of the testing data respectively across the two data sets. We discuss the wider relevance of these results with regards to challenging existing classification in real-world environments.

Ultraviolet Rayleigh-Mie lidar for daytime-temperature profiling of the troposphere.

PubMed

Hua, Dengxin; Uchida, Masaru; Kobayashi, Takao

2005-03-01

A UV Rayleigh-Mie scattering lidar has been developed for daytime measurement of temperature and aerosol optical properties in the troposphere. The transmitter is a narrowband, injection-seeded, pulsed, third-harmonic Nd:YAG laser at an eye-safe wavelength of 355 nm. Two Fabry-Perot etalons (FPEs) with a dual-pass optical layout filter the molecular Rayleigh scattering components spectrally for retrieval of the temperature and provide a high rejection rate for aerosol Mie scattering in excess of 43 dB. The Mie signal is filtered with a third FPE filter for direct profiling of aerosol optical properties. The Mie scattering component in the Rayleigh signals, which will have influence on temperature measurements, is corrected by using a measure of aerosol scattering because of the relative insufficiency of Mie rejection of Rayleigh filters in the presence of dense aerosols or clouds, and the Mie rejection capability of system is thus improved. A narrowband interference filter is incorporated with the FPEs to block solar radiation. Also, the small field of view (0.1 mrad) of the receiver and the UV wavelength used enhance the ability of the lidar to suppress the solar background signal in daytime measurement. The system is relatively compact, with a power-aperture product of 0.18 W m(-2), and has a high sensitivity to temperature change (0.62%/K). Lidar measurements taken under different weather conditions (winter and summer) are demonstrated. Good agreement between the lidar and the radiosonde measurements was obtained in terms of lapse rates and inversions. Statistical temperature errors of less than 1 K up to a height of 2 km are obtainable, with an averaging time of approximately 12 min for daytime measurements.

Discrimination of Biomass Burning Smoke and Clouds in MAIAC Algorithm

NASA Technical Reports Server (NTRS)

Lyapustin, A.; Korkin, S.; Wang, Y.; Quayle, B.; Laszlo, I.

2012-01-01

The multi-angle implementation of atmospheric correction (MAIAC) algorithm makes aerosol retrievals from MODIS data at 1 km resolution providing information about the fine scale aerosol variability. This information is required in different applications such as urban air quality analysis, aerosol source identification etc. The quality of high resolution aerosol data is directly linked to the quality of cloud mask, in particular detection of small (sub-pixel) and low clouds. This work continues research in this direction, describing a technique to detect small clouds and introducing the smoke test to discriminate the biomass burning smoke from the clouds. The smoke test relies on a relative increase of aerosol absorption at MODIS wavelength 0.412 micrometers as compared to 0.47-0.67 micrometers due to multiple scattering and enhanced absorption by organic carbon released during combustion. This general principle has been successfully used in the OMI detection of absorbing aerosols based on UV measurements. This paper provides the algorithm detail and illustrates its performance on two examples of wildfires in US Pacific North-West and in Georgia/Florida of 2007.

UV–Vis Light-induced Aging of Titan’s Haze and Ice

NASA Astrophysics Data System (ADS)

Couturier-Tamburelli, Isabelle; Piétri, Nathalie; Le Letty, Vincent; Chiavassa, Thierry; Gudipati, Murthy

2018-01-01

The study of the photochemical aging of aerosols is an important tool for understanding Titan’s stratosphere/troposphere composition and evolution, particularly the haze. Laboratory simulations of the photoreactivity of the haze aerosol analogs provide insight into the photochemical evolution of Titan’s atmosphere at and below the haze layers. Here we use experimental simulations to investigate the evolution of the laboratory analogs of these organic aerosols under ultraviolet (UV)–visible (Vis) photons, which make it through the haze layers during their sedimentation process. We present experimental results for the aging of Titan’s aerosol analogs obtained from two dominant nitrogen-containing organics, HC3N and HCN, under simulated Titan atmospheric conditions (photons and temperature). We report that volatile nitriles condensed on haze particles could be incorporated through photochemistry and provide one such sink mechanism for nitrile compounds. We provide laboratory evidence that the organic aerosols could photochemically evolve during their sedimentation through Titan’s atmosphere.

Surface-Sensitive and Bulk Studies on the Complexation and Photosensitized Degradation of Catechol by Iron(III) as a Model for Multicomponent Aerosol Systems

NASA Astrophysics Data System (ADS)

Al-abadleh, H. A.; Tofan-Lazar, J.; Situm, A.; Ruffolo, J.; Slikboer, S.

2013-12-01

Surface water plays a crucial role in facilitating or inhibiting surface reactions in atmospheric aerosols. Little is known about the role of surface water in the complexation of organic molecules to transition metals in multicomponent aerosol systems. We will show results from real time diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments for the in situ complexation of catechol to Fe(III) and its photosensitized degradation under dry and humid conditions. Catechol was chosen as a simple model for humic-like substances (HULIS) in aerosols and aged polyaromatic hydrocarbons (PAH). It has also been detected in secondary organic aerosols (SOA) formed from the reaction of hydroxyl radicals with benzene. Given the importance of the iron content in aerosols and its biogeochemistry, our studies were conducted using FeCl3. For comparison, these surface-sensitive studies were complemented with bulk aqueous ATR-FTIR, UV-vis, and HPLC measurements for structural, quantitative and qualitative information about complexes in the bulk, and potential degradation products. The implications of our studies on understanding interfacial and condensed phase chemistry relevant to multicomponent aerosols, water thin islands on buildings, and ocean surfaces containing transition metals will be discussed.

Interpreting the Ultraviolet Aerosol Index Observed with the OMI Satellite Instrument to Understand Absorption by Organic Aerosols: Implications for Atmospheric Oxidation and Direct Radiative Effects

NASA Technical Reports Server (NTRS)

Hammer, Melanie S.; Martin, Randall V.; Donkelaar, Aaron van; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

2016-01-01

Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOSChem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Angstrom exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30% over South America in September, up to 20% over southern Africa in July, and up to 15% over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus reducing the bias against observed values. We calculate the direct radiative effect (DRE) of BrC using GEOS-Chem coupled with the radiative transfer model RRTMG (GC-RT). Treating organic aerosol as containing more strongly absorbing BrC changes the global annual mean all-sky top of atmosphere (TOA) DRE by +0.03Wm(exp -2) and all-sky surface DRE by -0.08Wm(exp -2). Regional changes of up to +0.3Wm(exp -2) at TOA and down to -1.5Wm(exp -2) at the surface are found over major biomass burning regions.

Observations of fluorescent and biological aerosol at a high-altitude site in central France

NASA Astrophysics Data System (ADS)

Gabey, A. M.; Vaitilingom, M.; Freney, E.; Boulon, J.; Sellegri, K.; Gallagher, M. W.; Crawford, I. P.; Robinson, N. H.; Stanley, W. R.; Kaye, P. H.

2013-08-01

Total bacteria, fungal spore and yeast counts were compared with ultraviolet-light-induced fluorescence (UV-LIF) measurements of ambient aerosol at the summit of the Puy de Dôme (PdD) mountain in central France (1465 m a.s.l), which represents a background elevated site. Bacteria, fungal spores and yeast were enumerated by epifluorescence microscopy (EFM) and found to number 2.2 to 23 L-1 and 0.8 to 2 L-1, respectively. Bacteria counts on two successive nights were an order of magnitude larger than in the intervening day. A wide issue bioaerosol spectrometer, version 3 (WIBS-3) was used to perform UV-LIF measurements on ambient aerosol sized 0.8 to 20 μm. Mean total number concentration was 270 L-1 (σ = 66 L-1), found predominantly in a size mode at 2 μm for most of the campaign. Total concentration (fluorescent + non-fluorescent aerosol) peaked at 500 L-1 with a size mode at 1 μm because of a change in air mass origin lasting around 48 h. The WIBS-3 features two excitation and fluorescence detection wavelengths corresponding to different biological molecules, although non-biological interferents also contribute. The mean fluorescent particle concentration after short-wave (280 nm; associated with tryptophan) excitation was 12 L-1 (σ = 6 L-1), and did not vary much throughout the campaign. In contrast, the mean concentration of particles fluorescent after long-wave (370 nm; associated with NADH) excitation was 95 L-1 (σ = 25 L-1), and a nightly rise and subsequent fall of up to 100 L-1 formed a strong diurnal cycle in the latter. The two fluorescent populations exhibited size modes at 3 μm and 2 to 3 μm, respectively. A hierarchical agglomerative cluster analysis algorithm was applied to the data and used to extract different particle factors. A cluster concentration time series representative of bacteria was identified. This was found to exhibit a diurnal cycle with a maximum peak appearing during the day. Analysis of organic mass spectra recorded using an aerosol mass spectrometer (AMS; Aerodyne Inc.) suggests that aerosol reaching the site at night was more aged than that during the day, indicative of sampling the residual layer at night. Supplementary meteorological data and previous work also show that PdD lies in the residual layer/free troposphere at night, and this is thought to cause the observed diurnal cycles in organic-type and fluorescent aerosol particles. Based on the observed disparity between bacteria and fluorescent particle concentrations, fluorescent non-PBA is likely to be important in the WIBS-3 data and the surprisingly high fluorescent concentration in the residual layer/free troposphere raises questions about a ubiquitous background in continental air during the summer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson III, David J.; Sulzberger, Barbara; Zepp, Richard G.

Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solarmore » UV-B radiation. Mineralisation of organic matter results in the production and release of CO 2, whereas the biological pump is the main biological process for CO 2 removal by aquatic ecosystems. This research also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO 2, as well as of chemical and biological contaminants. Lastly,, interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces.« less

Retrievals of aerosol optical depth and Angström exponent from ground-based Sun-photometer data of Singapore.

PubMed

Salinas, Santo V; Chew, Boon N; Liew, Soo C

2009-03-10

The role of aerosols in climate and climate change is one of the factors that is least understood at the present. Aerosols' direct interaction with solar radiation is a well understood mechanism that affects Earth's net radiative forcing. However, quantifying its magnitude is more problematic because of the temporal and spatial variability of aerosol particles. To enhance our understanding of the radiative effects of aerosols on the global climate, Singapore has joined the AERONET (Aerosol Robotic Network) worldwide network by contributing ground-based direct Sun measurements performed by means of a multiwavelength Sun-photometer instrument. Data are collected on an hourly basis, then are uploaded to be fully screened and quality assured by AERONET. We use a one year data record (level 1.5/2.0) of measured columnar atmospheric optical depth, spanning from November 2006 to October 2007, to study the monthly and seasonal variability of the aerosol optical depth and the Angström exponent. We performed independent retrievals of these parameters (aerosol optical depth and Angström exponent) by using the photometer's six available bands covering the near-UV to near-IR (380-1080 nm). As a validation, our independent retrievals were compared with AERONET 1.5/2.0 level direct Sun product.

Utilization of O4 slant column density to derive aerosol layer height from a space-borne UV-visible hyperspectral sensor: sensitivity and case study

NASA Astrophysics Data System (ADS)

Park, Sang Seo; Kim, Jhoon; Lee, Hanlim; Torres, Omar; Lee, Kwang-Mog; Lee, Sang Deok

2016-02-01

The sensitivities of oxygen-dimer (O4) slant column densities (SCDs) to changes in aerosol layer height are investigated using the simulated radiances by a radiative transfer model, the linearized pseudo-spherical vector discrete ordinate radiative transfer (VLIDORT), and the differential optical absorption spectroscopy (DOAS) technique. The sensitivities of the O4 index (O4I), which is defined as dividing O4 SCD by 1040 molecules2 cm-5, to aerosol types and optical properties are also evaluated and compared. Among the O4 absorption bands at 340, 360, 380, and 477 nm, the O4 absorption band at 477 nm is found to be the most suitable to retrieve the aerosol effective height. However, the O4I at 477 nm is significantly influenced not only by the aerosol layer effective height but also by aerosol vertical profiles, optical properties including single scattering albedo (SSA), aerosol optical depth (AOD), particle size, and surface albedo. Overall, the error of the retrieved aerosol effective height is estimated to be 1276, 846, and 739 m for dust, non-absorbing, and absorbing aerosol, respectively, assuming knowledge on the aerosol vertical distribution shape. Using radiance data from the Ozone Monitoring Instrument (OMI), a new algorithm is developed to derive the aerosol effective height over East Asia after the determination of the aerosol type and AOD from the MODerate resolution Imaging Spectroradiometer (MODIS). About 80 % of retrieved aerosol effective heights are within the error range of 1 km compared to those obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements on thick aerosol layer cases.

Optical Properties of Black and Brown Carbon Aerosols from Laboratory Combustion of Wildland Fuels

NASA Astrophysics Data System (ADS)

Beres, N. D.; Molzan, J.

2015-12-01

Aerosol light absorption in the solar spectral region (300 nm - 2300 nm) of the atmosphere is key for the direct aerosol radiative forcing, which is determined by aerosol single scattering albedo (SSA), asymmetry parameter, and by the albedo of the underlying surface. SSA is of key importance for the sign and quantity of aerosol direct radiative forcing; that is, does the aerosol make the earth look darker (heating) or whiter (cooling)? In addition, these optical properties are needed for satellite retrievals of aerosol optical depth and properties. During wildland fires, aerosol optical absorption is largely determined by black carbon (BC) and brown carbon (BrC) emissions. BC is strongly absorbing throughout the solar spectrum, while BrC absorption strongly increases toward shorter wavelength and can be neglected in the red and infrared. Optical properties of BrC emitted from wildland fires are poorly understood and need to be studied as function of fuel type and moisture content and combustion conditions. While much more is known about BC optical properties, knowledge for the ultraviolet (UV) spectral region is still lacking and critically needed for satellite remote sensing (e.g., TOMS, OMI) and for modeling of tropospheric photochemistry. Here, a project to better characterize biomass burning aerosol optical properties is described. It utilizes a laboratory biomass combustion chamber to generate aerosols through combustion of different wildland fuels of global and regional importance. Combustion aerosol optics is characterized with an integrating nephelometer to measure aerosol light scattering and a photoacoustic instrument to measure aerosol light absorption. These measurements will yield optical properties that are needed to improve qualitative and quantitative understanding of aerosol radiative forcing and satellite retrievals for absorbing carbonaceous aerosols from combustion of wildland fuels.

Utilization of O4 Slant Column Density to Derive Aerosol Layer Height from a Space-Borne UV-Visible Hyperspectral Sensor: Sensitivity and Case Study

NASA Technical Reports Server (NTRS)

Park, Sang Seo; Kim, Jhoon; Lee, Hanlim; Torres, Omar; Lee, Kwang-Mog; Lee, Sang Deok

2016-01-01

The sensitivities of oxygen-dimer (O4) slant column densities (SCDs) to changes in aerosol layer height are investigated using the simulated radiances by a radiative transfer model, the linearized pseudo-spherical vector discrete ordinate radiative transfer (VLIDORT), and the differential optical absorption spectroscopy (DOAS) technique. The sensitivities of the O4 index (O4I), which is defined as dividing O4 SCD by 10(sup 40) molecules (sup 2) per centimeters(sup -5), to aerosol types and optical properties are also evaluated and compared. Among the O4 absorption bands at 340, 360, 380, and 477 nanometers, the O4 absorption band at 477 nanometers is found to be the most suitable to retrieve the aerosol effective height. However, the O4I at 477 nanometers is significantly influenced not only by the aerosol layer effective height but also by aerosol vertical profiles, optical properties including single scattering albedo (SSA), aerosol optical depth (AOD), particle size, and surface albedo. Overall, the error of the retrieved aerosol effective height is estimated to be 1276, 846, and 739 meters for dust, non-absorbing, and absorbing aerosol, respectively, assuming knowledge on the aerosol vertical distribution shape. Using radiance data from the Ozone Monitoring Instrument (OMI), a new algorithm is developed to derive the aerosol effective height over East Asia after the determination of the aerosol type and AOD from the MODerate resolution Imaging Spectroradiometer (MODIS). About 80 percent of retrieved aerosol effective heights are within the error range of 1 kilometer compared to those obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements on thick aerosol layer cases.

Utilization of O4 Slant Column Density to Derive Aerosol Layer Height from a Spaceborne UV-Visible Hyperspectral Sensor: Sensitivity and Case Study

NASA Technical Reports Server (NTRS)

Park, Sang Seo; Kim, Jhoon; Lee, Hanlim; Torres, Omar; Lee, Kwang-Mog; Lee, Sang Deok

2016-01-01

The sensitivities of oxygen-dimer (O4) slant column densities (SCDs) to changes in aerosol layer height are investigated using the simulated radiances by a radiative transfer model, the linearized pseudo-spherical vector discrete ordinate radiative transfer (VLIDORT), and the Differential Optical Absorption Spectroscopy (DOAS) technique. The sensitivities of the O4 index (O4I), which is defined as dividing O4 SCD by 10(exp 40) sq molecules cm(exp -5), to aerosol types and optical properties are also evaluated and compared. Among the O4 absorption bands at 340, 360, 380, and 477 nm, the O4 absorption band at 477 nm is found to be the most suitable to retrieve the aerosol effective height. However, the O4I at 477 nm is significantly influenced not only by the aerosol layer effective height but also by aerosol vertical profiles, optical properties including single scattering albedo (SSA), aerosol optical depth (AOD), particle size, and surface albedo. Overall, the error of the retrieved aerosol effective height is estimated to be 1276, 846, and 739 m for dust, non-absorbing, and absorbing aerosol, respectively, assuming knowledge on the aerosol vertical distribution shape. Using radiance data from the Ozone Monitoring Instrument (OMI), a new algorithm is developed to derive the aerosol effective height over East Asia after the determination of the aerosol type and AOD from the MODerate resolution Imaging Spectroradiometer (MODIS). About 80% of retrieved aerosol effective heights are within the error range of 1 km compared to those obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements on thick aerosol layer cases.

On the Specification of Smoke Injection Heights for Aerosol Forecasting

NASA Astrophysics Data System (ADS)

da Silva, A.; Schaefer, C.; Randles, C. A.

2014-12-01

The proper forecasting of biomass burning (BB) aerosols in global or regional transport models requires not only the specification of emission rates with sufficient temporal resolution but also the injection layers of such emissions. While current near realtime biomass burning inventories such as GFAS, QFED, FINN, GBBEP and FLAMBE provide such emission rates, it is left for each modeling system to come up with its own scheme for distributing these emissions in the vertical. A number of operational aerosol forecasting models deposits BB emissions in the near surface model layers, relying on the model's parameterization of turbulent and convective transport to determine the vertical mass distribution of BB aerosols. Despite their simplicity such schemes have been relatively successful reproducing the vertical structure of BB aerosols, except for those large fires that produce enough buoyancy to puncture the PBL and deposit the smoke at higher layers. Plume Rise models such as the so-called 'Freitas model', parameterize this sub-grid buoyancy effect, but require the specification of fire size and heat fluxes, none of which is readily available in near real-time from current remotely-sensed products. In this talk we will introduce a bayesian algorithm for estimating file size and heat fluxes from MODIS brightness temperatures. For small to moderate fires the Freitas model driven by these heat flux estimates produces plume tops that are highly correlated with the GEOS-5 model estimate of PBL height. Comparison to MINX plume height estimates from MISR indicates moderate skill of this scheme predicting the injection height of large fires. As an alternative, we make use of OMPS UV aerosol index data in combination with estimates of Overshooting Convective Tops (from MODIS and Geo-stationary satellites) to detect PyCu events and specify the BB emission vertical mass distribution in such cases. We will present a discussion of case studies during the SEAC4RS field campaign in August-September 2013.

Spectral Optical Properties of the Polluted Atmosphere of Mexico City (Spring-Summer 1992)

NASA Technical Reports Server (NTRS)

Vasilyev, O. B.; Contreras, A. Leyva; Valazquez, A. Muhlia; Peralta-Fabi, R.; Ivlev, L. S.; Kovalenko, A. P.; Vasilyev, A. V.; Jukov, V. M.; Welch, Ronald M.

1995-01-01

A joint Mexican, Russian, and American research effort has been initiated to develop new methods to remotely sense atmospheric parameters using ground-based, aircraft, and satellite observations. As a first step in this program, ground-based spectrophotometric measurements of the direct solar radiation have been obtained for the extremely polluted Mexico City atmosphere for the period of April-June 1992. These observations were made at more than 1300 channels in the spectral range of 0.35-0.95 microns. In the UltraViolet (UV) portions of the spectrum (e.g., 0.35 microns), aerosol optical thicknesses were found to range between 0.6 and 1.2; in the visible portion of the spectrum (e. g., 0.5 microns) they ranged from 0.5 to 0.8; and in the Near-Infrared (NIR) spectra (e.g., 0.85 micron), values of 0.3 - 0.5 were found. Applying a Spectral Optical Depth (SOD) model of tau(lambda) = C + A(lambda(sup -varies as), values of 1.55 less than varies as less than 1.85 were obtained for polluted, cloudless days, with values of 1.25 less than varies as less than 1.60 on days with haze. The aerosol particles in the polluted Mexico City atmosphere were found to be strongly absorbing, with a single-scattering albedo of 0.7 - 0.9 in the UV, 0.6 - 0.8 in the visible portion of the spectrum, and 0.4 - 0.7 in the NIR. These values are possibly consistent with a high soot concentration, contributed both by vehicular traffic and heavy industry. Analysis of the measured aerosol SOD using the optical parameters of an urban aerosol model pemiits the concentration of aerosol particles to be estimated in the vertical column; a maximum value of 3 x 10(exp 9) 1/sq cm was found. This concentration of aerosol particles exceeds that found in most other regions of the globe by at least an order of magnitude. Near the ground the aerosol size distributions measured using an optical particle counter were found to be strongly multimodal.

The actinic UV-radiation budget during the ESCOMPTE campaign 2001: results of airborne measurements with the microlight research aircraft D-MIFU

NASA Astrophysics Data System (ADS)

Junkermann, Wolfgang

2005-03-01

During the ESCOMPTE campaign 2001, the vertical distribution of ultraviolet actinic radiation was investigated with concurrent measurements of ozone, aerosol size distributions, and scattering coefficients using a microlight aircraft as airborne platform. Three-dimensional (3D) measurements were performed on a regional scale in the area between Avignon, Aix-en-Provence, and Marseille up to an altitude of 4000 m a.s.l. The results show a pronounced dependence of the vertical actinic flux distribution on aerosol load and stratification while horizontally no significant variability was observed. Furthermore, investigations under cloudy conditions and in the vicinity of cumulus clouds were performed allowing comparisons with one-dimensional and recently published three-dimensional model results. Cloud effects of scattered convective clouds were often found to be masked by aerosols and the aerosol content was generally the dominating factor controlling radiation transfer.

Aerosols correction of the OMI tropospheric NO2 retrievals over cloud-free scenes: Different methodologies based on the O2-O2 477 nm band

NASA Astrophysics Data System (ADS)

Chimot, Julien; Vlemmix, Tim; Veefkind, Pepijn; Levelt, Pieternel

2016-04-01

Numerous studies have drawn attention to the complexities related to the retrievals of tropospheric NO2 columns derived from satellite UltraViolet-Visible (UV-Vis) measurements in the presence of aerosols. Correction for aerosol effects will remain a challenge for the next generation of air quality satellite instruments such as TROPOMI on Sentinel-5 Precursor, Sentinel-4 and Sentinel-5. The Ozone Monitoring Instrument (OMI) instrument has provided daily global measurements of tropospheric NO2 for more than a decade. However, aerosols are not explicitly taken into account in the current operational OMI tropospheric NO2 retrieval chain (DOMINO v2 [Boersma et al., 2011]). Our study analyses 2 approaches for an operational aerosol correction, based on the use of the O2-O2 477 nm band. The 1st approach is the cloud-model based aerosol correction, also named "implicit aerosol correction", and already used in the operational chain. The OMI O2-O2 cloud retrieval algorithm, based on the Differential Optical Absorption Spectroscopy (DOAS) approach, is applied both to cloudy and to cloud-free scenes with aerosols present. Perturbation of the OMI cloud retrievals over scenes dominated by aerosols has been observed in recent studies led by [Castellanos et al., 2015; Lin et al., 2015; Lin et al., 2014]. We investigated the causes of these perturbations by: (1) confronting the OMI tropospheric NO2, clouds and MODIS AQUA aerosol products; (2) characterizing the key drivers of the aerosol net effects, compared to a signal from clouds, in the UV-Vis spectra. This study has focused on large industrialised areas like East-China, over cloud-free scenes. One of the key findings is the limitation due to the coarse sampling of the employed cloud Look-Up Table (LUT) to convert the results of the applied DOAS fit into effective cloud fraction and pressure. This leads to an underestimation of tropospheric NO2 amount in cases of particles located at elevated altitude. A higher sampling of the variation of O2-O2 SCD and continuum reflectance as a function of effective cloud parameters in case of low effective cloud fraction values is requested for applying an aerosol correction. The updates of the OMI O2-O2 cloud algorithm, based on the scheduled new OMI cloud LUT, will be presented in terms of impacts of the effective cloud retrievals and reduced biases of tropospheric NO2 columns over cloud-free scenes dominated by aerosols in China. A 2nd approach is investigated, assuming a more explicit aerosol correction. Previous analyses pointed out that the O2-O2 spectra contain information about aerosols: the continuum reflectance is primarily constrained by the Aerosol Optical thickness (AOT) while the O2-O2 Slant Column Density (SCD) mostly results from the combination of AOT and aerosols altitude. We have developed a first prototype algorithm allowing to retrieve information about AOT and aerosol altitude from the O2-O2 DOAS fit. We will discuss preliminary sensitivities and the potential accuracy of the associated explicit aerosol correction, without the use of effective cloud parameters.

Development and validation of reversed phase high performance liquid chromatography method for determination of dexpanthenol in pharmaceutical formulations.

PubMed

Kulikov, A U; Zinchenko, A A

2007-02-19

This paper describes the validation of an isocratic HPLC method for the assay of dexpanthenol in aerosol and gel. The method employs the Vydac Proteins C4 column with a mobile phase of aqueous solution of trifluoroacetic acid and UV detection at 206 nm. A linear response (r>0.9999) was observed in the range of 13.0-130 microg mL(-1). The method shows good recoveries and intra and inter-day relative standard deviations were less than 1.0%. Validation parameters as specificity, accuracy and robustness were also determined. The method can be used for dexpanthenol assay of panthenol aerosol and gel with dexpanthenol as the method separates dexpanthenol from aerosol or gel excipients.

Respirable form of crystals of cromoglycic acid.

PubMed

Chan, H K; Gonda, I

1989-02-01

Respirable crystals of cromoglycic acid (CA) were prepared by precipitation of CA with hydrochloric acid from aqueous solutions of cromolyn sodium and subsequent recrystallization from hot water or mixtures of dimethyl sulphoxide and water. The properties of the materials were established by melting point measurements, UV, IR, and NMR spectroscopy, and X-ray diffraction. Aerosols of CA were generated by nebulization of dilute CA suspensions and drying. The aerodynamic size distribution of CA in the dried aerosols was found by cascade impaction, and could be characterized by a logarithmic normal function with a mass median aerodynamic diameter (MMAD) of 0.7 micron and geometric standard deviation (sigma g) of 1.9. The likely advantages and problems of CA aerosols in the prevention of asthma are discussed.

Aerosol retrieval for APEX airborne imaging spectrometer: a preliminary analysis

NASA Astrophysics Data System (ADS)

Seidel, Felix; Nieke, Jens; Schläpfer, Daniel; Höller, Robert; von Hoyningen-Huene, Wolfgang; Itten, Klaus

2005-10-01

In order to achieve quantitative measurements of the Earth's surface radiance and reflectance, it is important to determine the aerosol optical thickness (AOT) to correct for the optical influence of atmospheric particles. An advanced method for aerosol detection and quantification is required, which is not strongly dependant on disturbing effects due to surface reflectance, gas absorption and Rayleigh scattering features. A short review of existing applicable methods to the APEX airborne imaging spectrometer (380nm to 2500nm), leads to the suggested aerosol retrieval method here in this paper. It will measure the distinct radiance change between two near-UV spectral bands (385nm & 412nm) due to aerosol induced scattering and absorption features. Atmospheric radiation transfer model calculations have been used to analyze the AOT retrieval capability and accuracy of APEX. The noise-equivalent differential AOT is presented along with the retrieval sensitivity to various input variables. It is shown, that the suggested method will be able to identify different aerosol model types and measure AOT and columnar size distribution. The proposed accurate AOT determination will lead to a unique opportunity of two-dimensional pixel-wise mapping of aerosol properties at a high spatial resolution. This will be helpful especially for regional climate studies, atmospheric pollution monitoring and for the improvement of aerosol dispersion models and the validation of aerosol algorithms on spaceborne sensors.

Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks

DOE PAGES

Erickson III, David J.; Sulzberger, Barbara; Zepp, Richard G.; ...

2014-11-07

Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solarmore » UV-B radiation. Mineralisation of organic matter results in the production and release of CO 2, whereas the biological pump is the main biological process for CO 2 removal by aquatic ecosystems. This research also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO 2, as well as of chemical and biological contaminants. Lastly,, interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces.« less

Small molecules as tracers in atmospheric secondary organic aerosol

NASA Astrophysics Data System (ADS)

Yu, Ge

Secondary organic aerosol (SOA), formed from in-air oxidation of volatile organic compounds, greatly affects human health and climate. Although substantial research has been devoted to SOA formation and evolution, the modeled and lab-generated SOA are still low in mass and degree of oxidation compared to ambient measurements. In order to compensate for these discrepancies, the aqueous processing pathway has been brought to attention. The atmospheric waters serve as aqueous reaction media for dissolved organics to undergo further oxidation, oligomerization, or other functionalization reactions, which decreases the vapor pressure while increasing the oxidation state of carbon atoms. Field evidence for aqueous processing requires the identification of tracer products such as organosulfates. We synthesized the standards for two organosulfates, glycolic acid sulfate and lactic acid sulfate, in order to measure their aerosol-state concentration from five distinct locations via filter samples. The water-extracted filter samples were analyzed by LC-MS. Lactic acid sulfate and glycolic acid sulfate were detected in urban locations in the United States, Mexico City, and Pakistan with varied concentrations, indicating their potential as tracers. We studied the aqueous processing reaction between glyoxal and nitrogen-containing species such as ammonium and amines exclusively by NMR spectrometry. The reaction products formic acid and several imidazoles along with the quantified kinetics were reported. The brown carbon generated from these reactions were quantified optically by UV-Vis spectroscopy. The organic-phase reaction between oxygen molecule and alkenes photosensitized by alpha-dicarbonyls were studied in the same manner. We observed the fast kinetics transferring alkenes to epoxides under simulated sunlight. Statistical estimations indicate a very effective conversion of aerosol-phase alkenes to epoxides, potentially forming organosulfates in a deliquescence event and increasing aerosol mass. Finally, we built a containerless apparatus to study aqueous processing reactions using an acoustic levitator paired with a mass spectrometer. The levitator is capable of trapping droplets with the size of 80-500 mum in diameter for over eight hours. The apparatus is also capable of drying and wetting the droplet in a controllable manner. We performed am example reaction between glyoxal and ammonium sulfate using this instrument, and showed that it could qualitatively monitor aqueous processing reactions.

PSC and volcanic aerosol routine observations in Antarctica by UV-visible ground-based spectrometry

NASA Technical Reports Server (NTRS)

Sarkissian, A.; Pommereau, J. P.; Goutail, F.

1994-01-01

Polar statospheric clouds (PSC) and stratospheric aerosol can be observed by ground-based UV-visible spectrometry by looking at the variation of the color of the sky during twilight. A radiative transfer model shows that reddenings are caused by high altitude (22-28 km) thin layers of scatterers, while low altitude (12-20 km) thick ones result in blueings. The color index method applied on 4 years of observations at Dumont d'Urville (67 deg S), from 1988 to 1991, shows that probably because the station is located at the edge of the vortex, dense PSC are uncommon. More unexpected is the existence of a systematic seasonal variation of the color of the twilight sky - bluer at spring - which reveals the formation of a dense scattering layer at or just above the tropopause at the end of the winter. Large scattering layers are reported above the station in 1991, first in August around 12-14 km, later in September at 22-24 km. They are attributed to volcanic aerosol from Mt Hudson and Mt Pinatubo respectively, which erupted in 1991. Inspection of the data shows that the lowest entered rapidly into the polar vortex but not the highest which remained outside, demonstrating that the vortex was isolated at 22-26 km.

Altitude Registration of Limb-Scattered Radiation

NASA Technical Reports Server (NTRS)

Moy, Leslie; Bhartia, Pawan K.; Jaross, Glen; Loughman, Robert; Kramarova, Natalya; Chen, Zhong; Taha, Ghassan; Chen, Grace; Xu, Philippe

2017-01-01

One of the largest constraints to the retrieval of accurate ozone profiles from UV backscatter limb sounding sensors is altitude registration. Two methods, the Rayleigh scattering attitude sensing (RSAS) and absolute radiance residual method (ARRM), are able to determine altitude registration to the accuracy necessary for long-term ozone monitoring. The methods compare model calculations of radiances to measured radiances and are independent of onboard tracking devices. RSAS determines absolute altitude errors, but, because the method is susceptible to aerosol interference, it is limited to latitudes and time periods with minimal aerosol contamination. ARRM, a new technique introduced in this paper, can be applied across all seasons and altitudes. However, it is only appropriate for relative altitude error estimates. The application of RSAS to Limb Profiler (LP) measurements from the Ozone Mapping and Profiler Suite (OMPS) on board the Suomi NPP (SNPP) satellite indicates tangent height (TH) errors greater than 1 km with an absolute accuracy of +/-200 m. Results using ARRM indicate a approx. 300 to 400m intra-orbital TH change varying seasonally +/-100 m, likely due to either errors in the spacecraft pointing or in the geopotential height (GPH) data that we use in our analysis. ARRM shows a change of approx. 200m over 5 years with a relative accuracy (a long-term accuracy) of 100m outside the polar regions.

The assessment of UV resources over Northern Eurasia

NASA Astrophysics Data System (ADS)

Chubarova, Natalia; Zhdanova, Yekaterina

2013-05-01

The spatial and temporal distribution of UV resources was assessed over Northern Eurasia by using RT modeling (8 stream DISORT RT code) with 1×1 degree grid and month resolution. For this purpose a special dataset of main input geophysical parameters (total ozone content, aerosol characteristics, surface UV albedo, and UV cloud modification factor) has been developed. To define the UV resources both erythemally-weighted and vitamin D irradiances were used. In order to better quantify vitamin D irradiance threshold we accounted for a body exposure fraction S as a function of surface effective temperature. The UV resources are defined by using several classes and subclasses: UV deficiency, UV optimum, and UV excess. They were evaluated for clear and typical cloudy conditions for different skin types. We show that for typical cloudy conditions in winter (January) there are only few regions in Europe at the south of Spain (southward 43°N) with conditions of UV optimum for people with skin type 2 and no such conditions for people with skin type 4. In summer (July) UV optimum for skin 2 is observed northward 63°N with a boundary biased towards higher latitudes at the east, while for skin type 4 these conditions are observed over the most territory of Northern Eurasia.

Highlights from 40 Years of Satellite UV Measurements

NASA Technical Reports Server (NTRS)

Bhartia, Pawan K.

2010-01-01

This year we are celebrating the 40th anniversary of the launch of the Backscatter Ultraviolet (BUV) instrument on NASA's Nimbus-4 satellite. The purpose of this instrument was to demonstrate the capability to measure total column ozone and its vertical distribution from space. The success of this instrument led to about a dozen instruments of this type on various NASA and NOAA satellites. These instruments used a single photomultiplier tube (PMT) that restricted the measurements to 6-12 discrete wavelengths in the 250-380 nm range. With the availability of solid-state detector arrays in the past decade it has been possible to make similar measurements but with hyperspectral (contiguous in wavelength) sampling and enhanced spectral resolution. This has allowed global mapping of several weakly-absorbing trace gases including S0 2, NO2, BrO, HCHO, and CIIOCHO. Since these measurements are affected by clouds and aerosols, a great deal of effort has gone into understanding their effect on ultraviolet radiation- both upwelling and downwelling. The downwelling UV radiation is chemically and biologically active and has both negative (genetic damage, air pollution) and positive (production of vitamin D and OH radical) environmental effects. I will discuss how the interaction of Rayleigh-scattered UV radiation with clouds and aerosols produce a variety of interesting effects that are leading to new methods of remote sensing of their properties. The UV measurements can greatly enhance the information that one derives from more traditional methods that use infrared and visible part of the solar spectrum.

Dynamic light absorption of biomass burning organic carbon photochemically aged under natural sunlight

NASA Astrophysics Data System (ADS)

Zhong, M.; Jang, M.

2013-08-01

Wood burning aerosol produced under smoldering conditions was photochemically aged with different relative humidity (RH) and NOx conditions using a 104 m3 dual outdoor chamber under natural sunlight. Light absorption of organic carbon (OC) was measured over the course of photooxidation using a UV-visible spectrometer connected to an integrating sphere. At high RH, the color decayed rapidly. NOx slightly prolonged the color of wood smoke, suggesting that NOx promotes the formation of chromophores via secondary processes. Overall, the mass absorption cross-section (integrated between 280 nm and 600 nm) of OC increased by 11-54% (except high RH) in the morning and then gradually decreased by 19-68% in the afternoon. This dynamic change in light absorption of wood burning OC can be explained by two mechanisms: chromophore formation and sunlight bleaching. To investigate the effect of chemical transformation on light absorption, wood smoke particles were characterized using various spectrometers. The intensity of fluorescence, which is mainly related to polycyclic aromatic hydrocarbons (PAHs), rapidly decreased with time indicating the potential bleaching of PAHs. A decline of levoglucosan concentrations evinced the change of POA with time. The aerosol water content measured by Fourier transform infrared spectroscopy showed that wood burning aerosol became less hygroscopic as photooxidation proceeded. A similar trend in light absorption changes has been observed in ambient smoke aerosol originating from the 2012 County Line Wildfire in Florida. We conclude that the biomass burning OC becomes less light absorbing after 8-9 h sunlight exposure compared to fresh wood burning OC.

Photochemistry of iron citrates initiated by UV-VIS light

NASA Astrophysics Data System (ADS)

Corral Arroyo, Pablo; Dou, Jing; Alpert, Peter; Krieger, Ulrich; Ammann, Markus

2017-04-01

Aerosol aging refers to the multitude of physical and chemical transformation atmospheric particles undergo, which play an important role in the impact of aerosols on climate, air quality and health. Aging processes may be started by chromophores, which act as photocatalysts that induce the oxidation of non-absorbing molecules [1]. Iron (Fe(III)) carboxylate complexes absorb light below about 500 nm, which is followed by ligand to metal charge transfer (LMCT) resulting in the reduction of iron to Fe(II) and oxidation of the carboxylate ligands, a process that represents an important sink of organic acids in the troposphere [2]. Our goal is to investigate how these photochemical processes contribute to the change of chemical and physical properties of the aerosol particles. To achieve this scope, we carry out coated wall flow tube experiments, exposing films with iron citrate to UV light, which will give information about the radical and LVOC production (connecting the CWFT to a Chemiluminescent Detector or PTR-TOF-MS respectively). From extracting and analyzing the films after irradiation with UV light, we obtain a profile of low-volatility products evolving from the photochemistry of iron citrates. By Scanning Transmission X-Ray Microspectroscopy (STXM) we analyze changes in the C K-edge and Fe L-edge in particles loaded with iron citrate upon exposure to light and follow their chemical and structural evolution upon photochemical oxidation in situ to investigate the degradation kinetics under varying environmental conditions. [1] George G., Ammann M., D'Anna B., Donaldson D. J., Nizkorodov S. A., Heterogeneous photochemistry in the Atmosphere, Chem. Rev., 2015, 115 (10), pp 4218-4258 [2] Weller, C., Horn, S., and Herrmann, H.: Photolysis of Fe(III) carboxylate complexes: Fe(II) quantum yields and reaction mechanisms, Photochemistry and Photobiology A: Chemistry, 268, 24-36, 2013.

Validation of SO2 Retrievals from the Ozone Monitoring Instrument over NE China

NASA Technical Reports Server (NTRS)

Krotkov, Nickolay A.; McClure, Brittany; Dickerson, Russell R.; Carn, Simon A.; Li, Can; Bhartia, Pawan K.; Yang, Kai; Krueger, Arlin J.; Li, Zhanqing; Levelt, Pieternel F.;

Long-term solar UV radiation reconstructed by ANN modelling with emphasis on spatial characteristics of input data

NASA Astrophysics Data System (ADS)

Feister, U.; Junk, J.; Woldt, M.; Bais, A.; Helbig, A.; Janouch, M.; Josefsson, W.; Kazantzidis, A.; Lindfors, A.; den Outer, P. N.; Slaper, H.

2008-06-01

Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Special emphasis will be given to the discussion of small-scale characteristics of input data to the ANN model. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980/1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.

Wet Removal of Organic and Black Carbon Aerosols

NASA Astrophysics Data System (ADS)

Torres, A.; Bond, T. C.; Lehmann, C.

2012-12-01

Organic carbon (OC) and black carbon (BC) aerosols derived from the combustion of fossil fuels and biomass are significant atmospheric pollutants that alter the Earth's radiation balance and affect human health. Carbonaceous aerosol lifetime and extent of its effects are mainly controlled by its wet removal, especially by rain. Limited work has been done to measure both BC and OC from rain events even though these aerosols are co-emitted and exist together in the atmosphere. The choices of analytical techniques for measuring OC and BC in water are limited, and researchers often employ the same techniques used for measuring atmospheric carbon particles. There is no agreement in the methods employed for monitoring carbon concentration in precipitation. As part of the method development, the Single Particle Soot Photometer (SP2), Thermal-Optical Analysis (TOA), Ultraviolet/Visible (UV/VIS) Spectrophotometer, and the Total Organic Carbon (TOC) Analyzer were evaluated for measuring BC suspended in water, water insoluble OC (WIOC) and dissolved OC (DOC). The study also monitored the concentration of BC, WIOC, and DOC in rainwater collected at Bondville (Illinois) for 18 months. Results indicated that 34% (±3%) of the BC mass was lost in the SP2 analysis, most probably during the nebulization process. Filtration required for TOA also had large losses (>75%) because quartz fiber filters were ineffective for capturing BC particles from water. Addition of NH4H2PO4 as a coagulant improved (>95%) the capture efficiency of the filters. UV/VIS spectrophotometry had good linearity, but the sensitivity for detecting BC particles (±20 μg/L) suspended in water was inadequate. TOC analysis was a robust technique for measuring both DOC and total carbon (BC + OC). The chosen techniques were TOC analysis for DOC, and TOA with an optimized filtration procedure for BC and WIOC. The mean concentrations in rainwater were 8.72 (±9.84) μg/L of BC, 88.97 (±62.64) μg/L of WIOC, and 1,320 (1,380) μg/L of DOC. DOC contributed, mostly with anions, to the ion balance of rain samples. The total carbon concentration (BC+WIOC+DOC) decreased with increasing precipitation volume and directly correlated with the concentrations of SO42-, NO3-, Ca2+, NH4+, Mg2+, and K+ in rainwater.

A Compact Mobile Ozone Lidar for Atmospheric Ozone and Aerosol Profiling

NASA Technical Reports Server (NTRS)

De Young, Russell; Carrion, William; Pliutau, Denis

2014-01-01

A compact mobile differential absorption lidar (DIAL) system has been developed at NASA Langley Research Center to provide ozone, aerosol and cloud atmospheric measurements in a mobile trailer for ground-based atmospheric ozone air quality campaigns. This lidar is integrated into the Tropospheric Ozone Lidar Network (TOLNet) currently made up of four other ozone lidars across the country. The lidar system consists of a UV and green laser transmitter, a telescope and an optical signal receiver with associated Licel photon counting and analog channels. The laser transmitter consist of a Q-switched Nd:YLF inter-cavity doubled laser pumping a Ce:LiCAF tunable UV laser with all the associated power and lidar control support units on a single system rack. The system has been configured to enable mobile operation from a trailer and was deployed to Denver, CO July 15-August 15, 2014 supporting the DISCOVER-AQ campaign. Ozone curtain plots and the resulting science are presented.

The Application of TOMS Ozone, Aerosol and UV-B Data to Madagascar Air Quality Determination

NASA Technical Reports Server (NTRS)

Aikin, A.C.; Einaudi, Franco (Technical Monitor)

2000-01-01

Total Ozone Mapping Spectrometer (TOMS) data products for the area of Madagascar are presented. In addition to total ozone, aerosols and UV-B tropospheric ozone results are shown from 1979 to the present. Tropospheric ozone over Africa and Madagascar is enhanced by 10 to 15 DU in October. This maximum coincides with the time of maximum biomass area burning in Africa and Madagascar. Ozone observations were made from 1979 to 1999 using the TOMS tropospheric ozone convective cloud differential method. As a result of easterly trade winds, ozone originating on Madagascar is transported to the west over the Mozambique Channel. In El Nino years higher level westerly winds descend to transport low level ozone easterly. This results in African continental ozone being transported east of Madagascar. Long range transport of African ozone is observed during El Nino periods. The potential of TOMS and other space data for use in public education and research on Madagascar air quality is demonstrated.

Molecular-level spectroscopic investigations of the complexation and photodegradation of catechol to/by iron(III)

NASA Astrophysics Data System (ADS)

Al-Abadleh, Hind; Tofan-Lazar, Julia; Situm, Arthur; Slikboer, Samantha

2014-05-01

Surface water plays a crucial role in facilitating or inhibiting surface reactions in atmospheric aerosols. Little is known about the role of surface water in the complexation of organic molecules to transition metals in multicomponent aerosol systems. We will show results from real time diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments for the in situ complexation of catechol to Fe(III) and its photosensitized degradation under dry and humid conditions. Catechol was chosen as a simple model for humic-like substances (HULIS) in aerosols and aged polyaromatic hydrocarbons (PAH). It has also been detected in secondary organic aerosols (SOA) formed from the reaction of hydroxyl radicals with benzene. Given the importance of the iron content in aerosols and its biogeochemistry, our studies were conducted using FeCl3. For comparison, these surface-sensitive studies were complemented with bulk aqueous ATR-FTIR, UV-vis, and HPLC measurements for structural, quantitative and qualitative information about complexes in the bulk, and potential degradation products. The implications of our studies on understanding interfacial and condensed phase chemistry relevant to multicomponent aerosols, water thin islands on buildings, and ocean surfaces containing transition metals will be discussed.

Several thoughts for using new satellite remote sensing and global modeling for aerosol and cloud climate studies

NASA Astrophysics Data System (ADS)

Nakajima, Teruyuki; Hashimoto, Makiko; Takenaka, Hideaki; Goto, Daisuke; Oikawa, Eiji; Suzuki, Kentaroh; Uchida, Junya; Dai, Tie; Shi, Chong

2017-04-01

The rapid growth of satellite remote sensing technologies in the last two decades widened the utility of satellite data for understanding climate impacts of aerosols and clouds. The climate modeling community also has received the benefit of the earth observation and nowadays closed-collaboration of the two communities make us possible to challenge various applications for societal problems, such as for global warming and global-scale air pollution and others. I like to give several thoughts of new algorithm developments, model use of satellite data for climate impact studies and societal applications related with aerosols and clouds. Important issues are 1) Better aerosol detection and solar energy application using expanded observation ability of the third generation geostationary satellites, i.e. Himawari-8, GOES-R and future MTG, 2) Various observation functions by directional, polarimetric, and high resolution near-UV band by MISR, POLDER&PARASOL, GOSAT/CAI and future GOSAT2/CAI2, 3) Various applications of general purpose-imagers, MODIS, VIIRS and future GCOM-C/SGLI, and 4) Climate studies of aerosol and cloud stratification and convection with active and passive sensors, especially climate impact of BC aerosols using CLOUDSAT&CALIPSO and future Earth Explorer/EarthCARE.

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

NASA Astrophysics Data System (ADS)

Waxman, E.; Slowik, J. G.; Kampf, C. J.; Timkovsky, J.; Noziere, B.; Praplan, A. P.; Pfaffenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A. S.; Baltensperger, U.; Volkamer, R.

2011-12-01

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

NASA Astrophysics Data System (ADS)

Waxman, E.; Slowik, J.; Kampf, C.; Timkovsky, J.; Noziere, B.; Praplan, A.; Pffafenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A.; Baltensperger, U.; Volkamer, R.

2012-04-01

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Spectral Aerosol Extinction (SpEx): A New Instrument for In situ Ambient Aerosol Extinction Measurements Across the UV/Visible Wavelength Range

NASA Technical Reports Server (NTRS)

Jordan, C. E.; Anderson, B. E.; Beyersdorf, A. J.; Corr, C. A.; Dibb, J. E.; Greenslade, M. E.; Martin, R. F.; Moore, R. H.; Scheuer, E.; Shook, M. A.;

Impact of OH Heterogenous Oxidation on the Evolution of Brown Carbon Aerosol Optical Properties

NASA Astrophysics Data System (ADS)

Schnitzler, E.; Abbatt, J.

2017-12-01

The effects of varying relative humidity (RH) on the evolution of brown carbon (BrC) optical properties induced by heterogeneous OH oxidation were investigated in a series of photooxidation chamber experiments. A BrC surrogate was generated from aqueous 1,3-dihydroxybenzene (10 mM) and H2O2 (10 mM) exposed to >300 nm radiation, atomized, passed through a series of trace gas denuders, and injected into the chamber, which was conditioned to about 10 or 60% RH. Following aerosol injection, H2O2 was continuously bubbled into the chamber; an hour later, the chamber was irradiated with black-lights (UV-B) to produce OH. Before irradiation, aerosol absorption and scattering at 405 nm, measured using a photoacoustic spectrometer, decreased due only to deposition and dilution, and single scattering albedo (SSA) was relatively steady. In the presence of gas-phase OH, absorption first increased, despite continued particle losses, and SSA decreased. Subsequently, absorption decreased faster than scattering, and SSA increased uniformly. At 60% RH, colour enhancement, likely associated with functionalization, was greatest after only minutes of reaction. In contrast, at 10% RH, peak colour enhancement occurred after about two hours of reaction, indicating that the decrease in RH and the attendant increase in particle viscosity significantly impeded heterogeneous OH oxidation of the BrC surrogate.

Monitoring Time-Dependent Formation of Oligomers and Brown Carbon in Reactions of Glycolaldehyde, Methylglyoxal, and Amines

NASA Astrophysics Data System (ADS)

Espelien, B.; Galloway, M. M.; De Haan, D. O.

2012-12-01

Authors: Brenna Espelien, Melissa Galloway, and David De Haan The brown carbon components of atmospheric aerosol exhibit strong UV absorbance with a featureless 'tail' that extends into the visible range. Recent work has shown that brown carbon (or HULIS) is formed at least in part by aqueous-phase chemical reactions in the atmosphere. Reactions between aldehydes (such as glycolaldehyde and methylglyoxal) and amines create brown products that have similar light-absorbing spectra as HULIS extracted from atmospheric aerosol. However, the structures of these products have not been well-characterized. Bulk-phase reactions were monitored using LCMS and UV-Vis spectroscopy over a period of 2-3 weeks to see what products formed, whether oligomerization is occurring, and how this correlates with the development of absorbance peaks in the visible range. UV-Vis data shows that these reactions generally take several days to reach maximum absorbance in the visible range. For the glycolaldehyde/glycine reaction, the appearance of a strong absorber at about 400 nm correlated with the appearance of high-mass products at m/z 227, 363, 393, and 431. Additional reactions between aldehydes and amines that quickly produce brown products are being studied. We suggest that imine oligomers are major products of these reactions.

Aqueous Chemistry in the Clouds of Venus: A Possible Source for the UV Absorber

NASA Astrophysics Data System (ADS)

Baines, Kevin H.; Delitsky, M. L.

2013-10-01

The identity and cause of the UV absorber near the Venusian cloudtops 62-70 km altitude) has been an enduring mystery. Given the role of sulfur in Venus’s atmosphere, where, somewhat analogous to water on Earth, it cycles through gas, liquid, and (possibly) solid phases in the atmosphere, it has been a prime suspect as at least a key component, perhaps as long-lived solid poly-sulfur aerosols, Sn, where n > 4. However, the narrow range of altitudes inhabited by the UV absorber (thought to form and reside primarily above 62 km altitude) seems incompatible with Sn, which should vertically disperse after formation. Here, we point to another process that could lead to somewhat more exotic chemistries that favor formation and sequestration at high altitudes: Aqueous chemistry within H2SO4-nH2O cloud particles. Due to (1) the decrease of temperature and (2) the increase in the fraction of water (“n” in the previous formula) of each cloud droplet with altitude, high-altitude particles near the cloudtops are - via the “heterogeneous uptake” process - significantly more capable of capturing and concentrating trace gases, in particular HCl. For example, the heterogeneous uptake of HCl in H2SO4 droplets near the 65-km cloudtops is at least three times greater than that found in the middle of the clouds near 55 km altitude. Other factors such as local mixing ratios and the concentration of other solvents in the droplet also modify the uptake. Within the cloud droplets, solution chemistry between HCl and H2SO4 may lead to the formation of chlorosulfonic acid, ClSO3H, which is a weak acid that readily breaks down into other species, such as SO2Cl2 (sulfuryl chloride) and SOCl2 (thionyl chloride). Together, these three materials have UV-blue absorptions at 0.21, 0.29, 0.39 and 0.47 micron. Thus, H2SO4 aerosols at high altitudes may take on lasting UV absorption characteristics, dependent on temperature (altitude) and other conditions, Balloons floating at benign Earth-surface-like temperature/pressure conditions near 56-km altitude may be able to sample such aerosols and their complex contents as measured in periodic downdrafts of materials from higher altitudes.

Aerosol Chemistry of Furfural and Sugars

NASA Astrophysics Data System (ADS)

Srithawirat, T.; Brimblecombe, P.

2008-12-01

Furfural and sugars (as levoglucosan equivalent) are derived from biomass burning and contribute to aerosol composition. This study examined the potential of furfural and levoglucosan to be tracers of biomass burning. Furfural is likely to be oxidized quickly so comparison with levoglucosan may give a sense of the age of the aerosols in forest fire smoke. However, few furfural emissions are available for biomass combustion. Furfural and sugars were determined in coarse aerosols (>2.4μm aerodynamic diameter) and fine aerosols (<2.4μm aerodynamic diameter) collected in 24 hour periods during different seasons in the United Kingdom and PM10 collected from Thailand and Malaysia including haze episodes. Also total suspended particulate matter (TSP) samples were collected from Taiwan. Furfural and sugars dominated in fine fractions, especially in the UK autumn. Sugars were found at 5.96-18.37 nmol m-3 in fine mode and 1.36-5.75 nmol m-3 in coarse mode aerosols in the UK. Furfural was found at 0.18-0.91 nmol m-3 and 0.05-0.51 nmol m-3 respectively in the same aerosols. Sugars were a dominant contributor to aerosol derived from biomass burning. Sugars and furfural were about 10 and 20 times higher during haze episodes in Malaysia. Laboratory experimental simulation suggested furfural is more rapid destroyed by UV and sunlight than levoglucosan.

Characterization of particle hygroscopicity by Raman lidar: Selected case studies from the convective and orographically-induced precipitation study

NASA Astrophysics Data System (ADS)

Stelitano, Dario; Di Girolamo, Paolo; Summa, Donato

2013-05-01

The characterization of particle hygroscopicity has primary importance for climate monitoring and prediction. Model studies have demonstrated that relative humidity (RH) has a critical influence on aerosol climate forcing. Hygroscopic properties of aerosols influence particle size distribution and refractive index and hence their radiative effects. Aerosol particles tend to grow at large relative humidity values as a result of their hygroscopicity. Raman lidars with aerosol, water vapor and temperature measurement capability are potentially attractive tools for studying aerosol hygroscopicity as in fact they can provide continuous altitude-resolved measurements of particle optical, size and microphysical properties, as well as relative humidity, without perturbing the aerosols or their environment. Specifically, the University of Basilicata Raman lidar system (BASIL) considered for the present study, has the capability to perform all-lidar measurements of relative humidity based on the application of both the rotational and the vibrational Raman lidar techniques in the UV. BASIL was operational in Achern (Black Forest, Lat: 48.64° N, Long: 8.06° E, Elev.: 140 m) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). The present analysis is focused on selected case studies characterized by the presence of different aerosol types with different hygroscopic behavior. The observed behavior, dependent upon aerosol composition, may range from hygrophobic to strongly hygroscopic.

Compact Ozone Lidar for Atmospheric Ozone and Aerosol Measurements

NASA Technical Reports Server (NTRS)

Marcia, Joel; DeYoung, Russell J.

2007-01-01

A small compact ozone differential absorption lidar capable of being deployed on a small aircraft or unpiloted atmospheric vehicle (UAV) has been tested. The Ce:LiCAF tunable UV laser is pumped by a quadrupled Nd:YLF laser. Test results on the laser transmitter demonstrated 1.4 W in the IR and 240 mW in the green at 1000 Hz. The receiver consists of three photon-counting channels, which are a far field PMT, a near field UV PMT, and a green PMT. Each channel was tested for their saturation characteristics.

Validation of OMI erythemal doses with multi-sensor ground-based measurements in Thessaloniki, Greece

NASA Astrophysics Data System (ADS)

Zempila, Melina Maria; Fountoulakis, Ilias; Taylor, Michael; Kazadzis, Stelios; Arola, Antti; Koukouli, Maria Elissavet; Bais, Alkiviadis; Meleti, Chariklia; Balis, Dimitrios

2018-06-01

The aim of this study is to validate the Ozone Monitoring Instrument (OMI) erythemal dose rates using ground-based measurements in Thessaloniki, Greece. In the Laboratory of Atmospheric Physics of the Aristotle University of Thessaloniki, a Yankee Environmental System UVB-1 radiometer measures the erythemal dose rates every minute, and a Norsk Institutt for Luftforskning (NILU) multi-filter radiometer provides multi-filter based irradiances that were used to derive erythemal dose rates for the period 2005-2014. Both these datasets were independently validated against collocated UV irradiance spectra from a Brewer MkIII spectrophotometer. Cloud detection was performed based on measurements of the global horizontal radiation from a Kipp & Zonen pyranometer and from NILU measurements in the visible range. The satellite versus ground observation validation was performed taking into account the effect of temporal averaging, limitations related to OMI quality control criteria, cloud conditions, the solar zenith angle and atmospheric aerosol loading. Aerosol optical depth was also retrieved using a collocated CIMEL sunphotometer in order to assess its impact on the comparisons. The effect of total ozone columns satellite versus ground-based differences on the erythemal dose comparisons was also investigated. Since most of the public awareness alerts are based on UV Index (UVI) classifications, an analysis and assessment of OMI capability for retrieving UVIs was also performed. An overestimation of the OMI erythemal product by 3-6% and 4-8% with respect to ground measurements is observed when examining overpass and noontime estimates respectively. The comparisons revealed a relatively small solar zenith angle dependence, with the OMI data showing a slight dependence on aerosol load, especially at high aerosol optical depth values. A mean underestimation of 2% in OMI total ozone columns under cloud-free conditions was found to lead to an overestimation in OMI erythemal doses of 1-5%.While OMI overestimated the erythemal dose rates over the range of cloudiness conditions examined, its UVIs were found to be reliable for the purpose of characterizing the ambient UV radiation impact.

Characterization Of Industrial And Background Aerosols In The RhÔne-alpes Region Using Laser Remote Sensing Device.

NASA Astrophysics Data System (ADS)

Geffroy, S.; Rairoux, P.; Mondelain, D.; Boutou, V.; Wolf, J.-P.; Frejafon, E.

Lack of reliable database on aerosol emission and dispersion is one of the main rea- sons for the incertitude of the impact of aerosol on the climate change. International statements and policies requested improvement on the global and on the regional scale. This new project is related to the characterisation of the spatial and time distribution of the aerosols in the Rhône-Alpes region. Actually, aerosols monitoring is mainly performed at ground level in this region and only few studies have been performed on the 3D distribution of urban aerosols (soot) using remote sensing laser device. The Rhône-Alpes region is representative for the regional impact of industry and traffic emission and also for the long-range transport of pollution over the East part of the Alps. The environmental situation of the region in term of sources and localization is especially dominated by: heavy traffic with several motorways (A6 from Paris, A7 to Marseille - both downtown - and A43 to the Alps and Italy) and industrial pollu- tion in particular for Lyon (refinery and several chemistry plants) and Saint Etienne agglomerations, which have a direct impact on the local air quality and also on the regional and national scale. Characterization of the aerosol load and dispersion in this region will be achieved applying two schemes. The first one will be related to the 3D quantitative characterization of diffuse aerosol emission in the industrial areas. Mon- itoring will be performed using a UV-infrared lidar remote sensing device. Emission cadastre elaboration and microphysical characterisation of the emission will be estab- lished. Direct access to several aerosol distribution modes will be used to describe the aerosol population dynamic: sedimentation, transport and aggregation. Studies on the direct impact of the emission on the region will be achieved coupling the 3D and ground level monitoring with dispersion model. The second scheme will be related to the long term remote sensing of the atmospheric background aerosols. Monitoring of the vertical and time distribution of their optical properties will be performed and this at 6 channels laying from the UV to the infrared spectral region. A high priority will be set on the data quality control and assurance in order to elaborate a reliable database. Several analyses will be performed with this dataset: the characterization of the microphysical properties of the aerosols. The regional and continental impact of the aerosols coupling the data with back-trajectories calculation and the validation of radiative model. By achieving a sufficient data quality, a proposition will be made to integrate the data into the European network Earlinet, which establishes a quantita- tive comprehensive statistical data base of both horizontal and vertical distributions of aerosols on a continental scale using a network of advanced laser remote sensing stations distributed all over Europe. This project will begin in summer 2002 and it will be taking place in cooperation with the national office INERIS.

Direct radiative effect due to brownness in organic carbon aerosols generated from biomass combustion

NASA Astrophysics Data System (ADS)

Rathod, T. D.; Sahu, S. K.; Tiwari, M.; Pandit, G. G.

2016-12-01

We report the enhancement in the direct radiative effect due the presence of Brown carbon (BrC) as a part of organic carbon aerosols. The optical properties of organic carbon aerosols generated from pyrolytic combustion of mango tree wood (Magnifera Indica) and dung cake at different temperatures were considered. Mie codes were used to calculate absorption and scattering coefficients coupled with experimentally derived imaginary complex refractive index. The direct radiative effect (DRE) for sampled organic carbon aerosols was estimated using a wavelength dependent radiative transfer equation. The BrC DRE was estimated taking virtually non absorbing organic aerosols as reference. The BrC DRE from wood and dung cake was compared at different combustion temperatures and conditions. The BrC contributed positively to the direct top of the atmosphere radiative effect. Dung cake generated BrC aerosols were found to be strongly light absorbing as compared to BrC from wood combustion. It was noted that radiative effects of BrC from wood depended on its generation temperature and conditions. For BrC aerosols from dung cake such strong dependence was not observed. The average BrC aerosol DRE values were 1.53±0.76 W g-1 and 17.84±6.45 W g-1 for wood and dung cake respectively. The DRE contribution of BrC aerosols came mainly (67-90%) from visible light absorption though they exhibited strong absorption in shorter wavelengths of the UV-visible spectrum.

The study of the martian atmosphere from top to bottom with SPICAM light on mars express

NASA Astrophysics Data System (ADS)

Bertaux, Jean-Loup; Fonteyn, D.; Korablev, O.; Chassefière, E.; Dimarellis, E.; Dubois, J. P.; Hauchecorne, A.; Cabane, M.; Rannou, P.; Levasseur-Regourd, A. C.; Cernogora, G.; Quemerais, E.; Hermans, C.; Kockarts, G.; Lippens, C.; de Maziere, M.; Moreau, D.; Muller, C.; Neefs, B.; Simon, P. C.; Forget, F.; Hourdin, F.; Talagrand, O.; Moroz, V. I.; Rodin, A.; Sandel, B.; Stern, A.

2000-10-01

SPICAM Light is a small UV-IR instrument selected for Mars Express to recover most of the science that was lost with the demise of Mars 96, where the SPICAM set of sensors was dedicated to the study of the atmosphere of Mars (Spectroscopy for the investigation of the characteristics of the atmosphere of mars). The new configuration of SPICAM Light includes optical sensors and an electronics block. A UV spectrometer (118-320 nm, resolution 0.8 nm) is dedicated to Nadir viewing, limb viewing and vertical profiling by stellar occultation (3.8 kg). It addresses key issues about ozone, its coupling with H 2O, aerosols, atmospheric vertical temperature structure and ionospheric studies. An IR spectrometer (1.2- 4.8 μm, resolution 0.4-1 nm) is dedicated to vertical profiling during solar occultation of H 2O, CO 2, CO, aerosols and exploration of carbon compounds (3.5 kg). A nadir looking sensor for H 2O abundances (1.0- 1.7 μm, resolution 0.8 nm) is recently included in the package (0.8 kg). A simple data processing unit (DPU, 0.9 kg) provides the interface of these sensors with the spacecraft. In nadir orientation, SPICAM UV is essentially an ozone detector, measuring the strongest O 3 absorption band at 250 nm in the spectrum of the solar light scattered back from the ground. In the stellar occultation mode the UV Sensor will measure the vertical profiles of CO 2, temperature, O 3, clouds and aerosols. The density/temperature profiles obtained with SPICAM Light will constrain and aid in the development of the meteorological and dynamical atmospheric models, from the surface to 160 km in the atmosphere. This is essential for future missions that will rely on aerocapture and aerobraking. UV observations of the upper atmosphere will allow study of the ionosphere through the emissions of CO, CO +, and CO 2+, and its direct interaction with the solar wind. Also, it will allow a better understanding of escape mechanisms and estimates of their magnitude, crucial for insight into the long-term evolution of the atmosphere. The SPICAM Light IR sensor is inherited from the IR solar part of the SPICAM solar occultation instrument of Mars 96. Its main scientific objective is the global mapping of the vertical structure of H 2O, CO 2, CO, HDO, aerosols, atmospheric density, and temperature by the solar occultation. The wide spectral range of the IR spectrometer and its high spectral resolution allow an exploratory investigation addressing fundamental question of the possible presence of carbon compounds in the Martian atmosphere. Because of severe mass constraints this channel is still optional. An additional nadir near IR channel that employs a pioneering technology acousto-optical tuneable filter (AOTF) is dedicated to the measurement of water vapour column abundance in the IR simultaneously with ozone measured in the UV. It will be done at much lower telemetry budget compared to the other instrument of the mission, planetary fourier spectrometer (PFS).

SAGE 3: A visible wavelength limb sounder

NASA Technical Reports Server (NTRS)

Chu, W. P.; Mccormick, M. P.; Zawodny, J.; Mcmaster, L. R.

1990-01-01

A brief description is presented for the SAGE 3 (Stratospheric Aerosol and Gas Experiment 3) instrument that has been selected to fly onboard the National Polar Platform 1 (NPOP 1) for the Earth Observational System (Eos) in 1996. The SAGE 3 instrument will perform earth limb sounding with the solar occultation technique measuring the ultraviolet (UV), the visible, and the near infrared (IR) wavelength solar radiation. The instrument will produce atmospheric data for the vertical distribution of aerosol, ozone, nitrogen dioxide, water vapor, and oxygen. The details of the instrument design, data flow, and processing requirements are discussed.

Retrieval and molecule sensitivity studies for the global ozone monitoring experiment and the scanning imaging absorption spectrometer for atmospheric chartography

NASA Technical Reports Server (NTRS)

Chance, Kelly V.; Burrows, John P.; Schneider, Wolfgang

1991-01-01

The Global Ozone Monitoring Experiment (GOME) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) are diode based spectrometers that will make atmospheric constituent and aerosol measurements from European satellite platforms beginning in the mid 1990's. GOME measures the atmosphere in the UV and visible in nadir scanning, while SCIAMACHY performs a combination of nadir, limb, and occultation measurements in the UV, visible, and infrared. A summary is presented of the sensitivity studies that were performed for SCIAMACHY measurements. As the GOME measurement capability is a subset of the SCIAMACHY measurement capability, the nadir, UV, and visible portion of the studies is shown to apply to GOME as well.

Urban UV environment in a sub-tropical megacity - A measurement and modelling study

NASA Astrophysics Data System (ADS)

Wai, Ka-Ming; Yu, Peter K. N.; Chan, Pok-Man

The variations of solar total UV (UVA + UVB) exposure rates in a megacity featured with high-rise buildings during summer months were measured and relevant model predictions were evaluated. The maximum pedestrian-level total solar UV exposure rate was less than the un-obstructed exposure rate at any time, attributing to the prevailing reduction in the diffuse solar radiation due to the obstruction effects of distant buildings. Comparing with the measurements, our coupled model well captured the spatial and temporal variations of the reduction of UV exposure rates. By measurements, large reduction in the solar total UV exposure rate down to 12% of un-obstructed exposure rate due to the building obstruction effects was found, agreeing with our previous simulation results and results from an Australian megacity. On the other hand, building reflection from reflective curtain walls could reach 23% of the un-obstructed solar total UV exposure rate at the ground level. This implied improper building design creating additional harmful effects of solar UV radiation on the environment. The coupled model was also applied to predict the urban UV exposure rates during a tropical-cyclone induced aerosol episode. A well-evaluated urban solar UV model is an important tool for sustainable urban design.

In Situ Formation of Humic-like Substances In Model Cloud Water

NASA Astrophysics Data System (ADS)

Gelencsér, A.; Hoffer, A.; Kiss, G.; Tombácz, E.; Blazsó, M.; Bencze, L.

It is now widely established that humic-like substances (HULIS) are ubiquitous con- stituents in continental fine aerosol. Several studies have confirmed that HULIS are abundant organic species in the aqueous extract of rural, urban and biomass burn- ing aerosol. We have recently suggested that such compounds may be secondary (ternary?) aerosol constituents which are formed in the condensed phase from a vast array of low volatility organic precursors of primary or secondary origin. However, no experimental evidence has ever confirmed that such polymerisation reactions can indeed take place within the limited residence time of the accumulation mode aerosol. Normally, humification processes are generally assumed to take years and require spe- cial microbial environment which is barely available aloft. We studied polymerisation reactions of aromatic hydroxy-acids in the laboratory in solutions modelling the condi- tions prevalent in cloud water. In the solutions OH radicals were generated in Fenton- type reactions. The course of the reaction was monitored by UV-VIS spectrophotom- etry and liquid chromatography. The reaction products were characterised by fluo- rescence spectrometry, liquid chromatography-mass spectrometry and pyrolysis- gas chromatography-mass spectrometry. By monitoring the absorbance of the simulated cloud solution we demonstrated that chemical reactions took place in the solution pro- ducing measurable concentrations of chromophoric substances within the order of a few hours. The recorded UV-VIS spectra of the reaction products were very similar to those which had been observed in aqueous extracts of rural fine aerosol as well as in aqueous solutions of terrestrial humic and fulvic acids. Electrospray-mass spectra of the reaction products revealed that they consisted of an array of molecular species with a continuous molecular weight distribution peaking at a few hundred Dalton. Such spectra were also found to be typical of terrestrial humic and fulvic acids. Such similarities were also observed in the fluorescence and pyrolysis measurements. We hypothesized that free radical polymerisation proceeded via phenoxy radical interme- diates to yield dimeric and trimeric products, ill-defined humic-like substances. We therefore suggest that in hydrometeors similar reactions of polar aromatic compounds with hydroxyl radicals yield humic-like substances as secondary aerosol constituents.

The atmospheric transparency of Telescope Array experiment from LIDAR

NASA Astrophysics Data System (ADS)

Tomida, T.

2011-09-01

UV fluorescence light generated by an air shower is scattered and lost along the path of transmission to the telescope. The main scattering processes are Rayleigh scattering by molecules and scattering by aerosols in an atmosphere. In the Telescope Array Experiment, we make use of LIDAR (LIght Detection And Ranging), which observes the back-scattered light of laser. The LIDAR system is operated before the beginning and after the end of an FD observation, twice a night. The typical transparency of aerosols on clear night is obtained two years observation from September, 2007. The extinction coefficient of aerosols (αAS) at ground level are 0.040-0.013+0.036 km-1. The dependence of typical aerosols on height above ground level (1450 m a.s.l.) can be express by two exponential components as following: αAS(h) = 0.021 exp(-h/0.2)+0.019 exp(-h/1.9). The atmospheric transparency measured with the LIDAR system in TA site is discussed in this paper.

Light absorption of organic aerosol from pyrolysis of corn stalk

NASA Astrophysics Data System (ADS)

Li, Xinghua; Chen, Yanju; Bond, Tami C.

2016-11-01

Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

Spacecraft instrument calibration and stability

NASA Technical Reports Server (NTRS)

Gille, J. C.; Feldman, P.; Hudson, R.; Lean, J.; Madden, R.; Mcmaster, L.; Mount, G.; Rottman, G.; Simon, P. C.

1989-01-01

The following topics are covered: instrument degradation; the Solar Backscatter Ultraviolet (SBUV) Experiment; the Total Ozone Mapping Spectrometer (TOMS); the Stratospheric Aerosol and Gas Experiment 1 (SAGE-1) and SAGE-2 instruments; the Solar Mesosphere Explorer (SME) UV ozone and near infrared airglow instruments; and the Limb Infrared Monitor of the Stratosphere (LIMS).

Climatology of Ultra Violet(UV) Irradiance at the Surface of the Earth as Measured by the Belgian UV Radiation Monitoring Network

NASA Astrophysics Data System (ADS)

Pandey, Praveen; Gillotay, Didier; Depiesse, Cedric

2016-08-01

In this paper we describe the network of ground-based ultraviolet (UV) radiation monitoring stations in Belgium. The evolution of the entire network, together with the details of measuring instruments is given. The observed cumulative irradiations -UVB, UVA and total solar irradiation (TSI)- over the course of measurement for three stations -a northern (Ostende), central (Uccle) and a southern (Redu)- are shown. The longest series of measurement shown in this study is at Uccle, Brussels, from 1995 till 2014. Thus, the variation of the UV index, together with the variation of irradiations during summer and winter months at Uccle are shown as a part of this climatological study. The trend of UVB irradiance over the above mentioned three stations is shown. This UVB trend is studied in conjunction with the long-term satellite-based total column ozone value over Belgium, which shows two distinct trends marked by a change point. The total column ozone trend following the change point is positive. It is also seen that the UVB trend is positive for the urban/sub-urban sites: Uccle and Redu. Whereas the UVB trend at Ostende, which is a coastal site, is not positive. A possible explanation of this relation between total column ozone and UVB trend could be associated with aerosols, which is shown in this paper by means of a radiative transfer model based study -as a part of a preliminary investigation. It is seen that the UVI is influenced by the type of aerosols.

Environmental and biological monitoring of occupational exposure to polynuclear aromatic hydrocarbons during highway pavement construction in Italy.

PubMed

Fostinelli, Jacopo; Madeo, Egidio; Toraldo, Emanuele; Sarnico, Michela; Luzzana, Giorgio; Tomasi, Cesare; De Palma, Giuseppe

2018-06-09

We performed a cross-sectional study with the main aim of evaluating occupational exposure to polycyclic aromatic hydrocarbons (PAHs) in workers involved in the pavement construction of a new highway in Northern Italy, where modified bitumen was used as binder for Hot Mix Asphalt. We applied a combined approach of air and biological monitoring. Both the aerosol and vapour phases of bitumen were collected applying the NIOSH 5506 method. The 16 PAHs listed as high priority by EPA were determined by HPLC-UV. End-of-shift urine samples were collected from 144 workers to determine 1-hydroxypyrene (1-OHP) and 2-naphthol (2-NAP) concentrations after enzyme digestion and HPLC-UV analysis. Socio-demographic and lifestyle information was collected by a questionnaire. Paving workers were actually exposed to PAHs, including carcinogenic compounds, that were measurable only in the aerosol phase. Higher exposure as well as dose levels were measured for the paver group. Biological monitoring confirmed that 1-OHP was less affected by smoking habits as compared to 2-NAP and showed a higher association with occupational exposure. Carcinogenic PAH compounds were detectable only in the aerosol phase and this must be taken into account in the adoption of preventive measures. Biomonitoring supported the superiority of 1-OHP as compared to 2-NAP in assessing the internal dose in such workers. Copyright © 2018. Published by Elsevier B.V.

Effect of Wildfire Aerosols on NO2 Photolysis and Ozone Production at the Mt. Bachelor Observatory

NASA Astrophysics Data System (ADS)

Baylon, P.; Jaffe, D. A.; Hall, S. R.; Ullmann, K.; Lefer, B. L.

2015-12-01

In this study, we have two goals: to quantify the effect of biomass burning aerosols on jNO2 photolysis and to look at O3 formation in biomass burning plumes as it relates to jNO2 photolysis. Wildfire plumes were observed during the summer of 2015 at the Mt. Bachelor Observatory, a high-elevation (2.8 km a.s.l.) mountaintop site located in central Oregon. These plumes were identified using the following criteria: (1) 5-minute ambient aerosol scattering σsp ≥ 20 Mm-1 for at least two hours, (2) 5-minute CO ≥ 150 ppbv for at least two hours, (3) strong correlation (r2 ≥ 0.70) between σsp and CO, and (4) consistent air mass back trajectories indicating transport over known fire locations. We measure nitrogen oxides using a chemiluminescence detector and jNO2 photolysis using a diode array actinic flux spectroradiometer. We also measure O3 using two techniques: (a) UV method with a cavity ring-down spectrometer and (b) chemiluminescence method with a custom-made instrument. We compare fire event observations between these two procedures to prove consistency. Based on these measurements, we quantify a lower bound for the HO2 and RO2 radical concentrations in wildfire plumes. We then look at plume and non-plume data and examine deviations from the photostationary state. Finally, we use the TUV model v5.2 to simulate clear-sky conditions and therefore quantify the reduction/enhancement in jNO2 values and O3 production due to wildfire aerosols. This gives us insight into the photochemical environment in biomass burning plumes, which until now, remains poorly understood.

Aerosols optical properties in Titan's detached haze layer before the equinox

NASA Astrophysics Data System (ADS)

Seignovert, Benoît; Rannou, Pascal; Lavvas, Panayotis; Cours, Thibaud; West, Robert A.

2017-08-01

UV observations with Cassini ISS Narrow Angle Camera of Titan's detached haze is an excellent tool to probe its aerosols content without being affected by the gas or the multiple scattering. Unfortunately, its low extent in altitude requires a high resolution calibration and limits the number of images available in the Cassini dataset. However, we show that it is possible to extract on each profile the local maximum of intensity of this layer and confirm its stability at 500 ± 8 km during the 2005-2007 period for all latitudes lower than 45°N. Using the fractal aggregate scattering model of Tomasko et al. (2008) and a single scattering radiative transfer model, it is possible to derive the optical properties required to explain the observations made at different phase angles. Our results indicates that the aerosols have at least ten monomers of 60 nm radius, while the typical tangential column number density is about 2 · 1010 agg m-2. Moreover, we demonstrate that these properties are constant within the error bars in the southern hemisphere of Titan over the observed time period. In the northern hemisphere, the size of the aerosols tends to decrease relatively to the southern hemisphere and is associated with a higher tangential opacity. However, the lower number of observations available in this region due to the orbital constraints is a limiting factor in the accuracy of these results. Assuming a fixed homogeneous content we notice that the tangential opacity can fluctuate up to a factor 3 among the observations at the equator. These variations could be linked with short scale temporal and/or longitudinal events changing the local density of the layer.

Photochemical aging of light-absorbing secondary organic aerosol material.

PubMed

Sareen, Neha; Moussa, Samar G; McNeill, V Faye

2013-04-11

Dark reactions of methylglyoxal with NH4(+) in aqueous aerosols yield light-absorbing and surface-active products that can influence the physical properties of the particles. Little is known about how the product mixture and its optical properties will change due to photolysis as well as oxidative aging by O3 and OH in the atmosphere. Here, we report the results of kinetics and product studies of the photochemical aging of aerosols formed by atomizing aqueous solutions of methylglyoxal and ammonium sulfate. Experiments were performed using aerosol flow tube reactors coupled with an aerosol chemical ionization mass spectrometer (Aerosol-CIMS) for monitoring gas- and particle-phase compositions. Particles were also impacted onto quartz windows in order to assess changes in their UV-visible absorption upon oxidation. Photooxidation of the aerosols leads to the formation of small, volatile organic acids including formic acid, acetic acid, and glyoxylic acid. The atmospheric lifetime of these species during the daytime is predicted to be on the order of minutes, with photolysis being an important mechanism of degradation. The lifetime with respect to O3 oxidation was observed to be on the order of hours. O3 oxidation also leads to a net increase in light absorption by the particles due to the formation of additional carbonyl compounds. Our results are consistent with field observations of high brown carbon absorption in the early morning.

Monitoring O3 and Aerosols with the NASA LaRC Mobile Ozone Lidar System

NASA Technical Reports Server (NTRS)

Ganoe, Rene; Gronoff, Guillaume; Berkoff, Timothy; DeYoung, Russell; Carrion, William

2016-01-01

The NASA's Langley Mobile Ozone Lidar (LMOL) system routinely measures tropospheric ozone and aerosol profiles, and is part of the Tropospheric Lidar Network (TOLNet). Recent upgrades to the system include a new pump laser that has tripled the transmission output power extending measurements up to 8 km in altitude during the day. In addition, software and algorithm developments have improved data output quality and enabled a real-time ozone display capability. In 2016, a number of ozone features were captured by LMOL, including the dynamics of an early-season ozone exceedance that impacted the Hampton Roads region. In this presentation, we will review current LMOL capabilities, recent air quality events observed by the system, and show a comparison of aerosol retrieval through the UV channel and the green line channel.

Estimated SAGE II ozone mixing ratios in early 1993 and comparisons with Stratospheric Photochemistry, Aerosols and Dynamic Expedition measurements

NASA Technical Reports Server (NTRS)

Yue, G. K.; Veiga, R. E.; Poole, L. R.; Zawodny, J. M.; Proffitt, M. H.

1994-01-01

An empirical time-series model for estimating ozone mixing ratios based on Stratospheric Aerosols and Gas Experiment II (SAGE II) monthly mean ozone data for the period October 1984 through June 1991 has been developed. The modeling results for ozone mixing ratios in the 10- to 30- km region in early months of 1993 are presented. In situ ozone profiles obtained by a dual-beam UV-absorption ozone photometer during the Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE) campaign, May 1-14, 1993, are compared with the model results. With the exception of two profiles at altitudes below 16 km, ozone mixing ratios derived by the model and measured by the ozone photometer are in relatively good agreement within their individual uncertainties. The identified discrepancies in the two profiles are discussed.

Vegetation fires and air pollution in Vietnam.

PubMed

Le, Thanh Ha; Thanh Nguyen, Thi Nhat; Lasko, Kristofer; Ilavajhala, Shriram; Vadrevu, Krishna Prasad; Justice, Chris

2014-12-01

Forest fires are a significant source of air pollution in Asia. In this study, we integrate satellite remote sensing data and ground-based measurements to infer fire-air pollution relationships in selected regions of Vietnam. We first characterized the active fires and burnt areas at a regional scale from MODIS satellite data. We then used satellite-derived active fire data to correlate the resulting atmospheric pollution. Further, we analyzed the relationship between satellite atmospheric variables and ground-based air pollutant parameters. Our results show peak fire activity during March in Vietnam, with hotspots in the Northwest and Central Highlands. Active fires were significantly correlated with UV Aerosol Index (UVAI), aerosol extinction absorption optical depth (AAOD), and Carbon Monoxide. The use of satellite aerosol optical thickness improved the prediction of Particulate Matter (PM) concentration significantly. Copyright © 2014 Elsevier Ltd. All rights reserved.

Tiny Ultraviolet Polarimeter for Earth Stratosphere from Space Investigation

NASA Astrophysics Data System (ADS)

Nevodovskyi, P. V.; Morozhenko, O. V.; Vidmachenko, A. P.; Ivakhiv, O.; Geraimchuk, M.; Zbrutskyi, O.

2015-09-01

One of the reasons for climate change (i.e., stratospheric ozone concentrations) is connected with the variations in optical thickness of aerosols in the upper sphere of the atmosphere (at altitudes over 30 km). Therefore, aerosol and gas components of the atmosphere are crucial in the study of the ultraviolet (UV) radiation passing upon the Earth. Moreover, a scrupulous study of aerosol components of the Earth atmosphere at an altitude of 30 km (i.e., stratospheric aerosol), such as the size of particles, the real part of refractive index, optical thickness and its horizontal structure, concentration of ozone or the upper border of the stratospheric ozone layer is an important task in the research of the Earth climate change. At present, the Main Astronomical Observatory of the National Academy of Sciences (NAS) of Ukraine, the National Technical University of Ukraine "KPI"and the Lviv Polytechnic National University are engaged in the development of methodologies for the study of stratospheric aerosol by means of ultraviolet polarimeter using a microsatellite. So fare, there has been created a sample of a tiny ultraviolet polarimeter (UVP) which is considered to be a basic model for carrying out space experiments regarding the impact of the changes in stratospheric aerosols on both global and local climate.

Follow the Carbon: Isotopic Labeling Studies of Early Earth Aerosol.

PubMed

Hicks, Raea K; Day, Douglas A; Jimenez, Jose L; Tolbert, Margaret A

2016-11-01

Despite the faint young Sun, early Earth might have been kept warm by an atmosphere containing the greenhouse gases CH 4 and CO 2 in mixing ratios higher than those found on Earth today. Laboratory and modeling studies suggest that an atmosphere containing these trace gases could lead to the formation of organic aerosol haze due to UV photochemistry. Chemical mechanisms proposed to explain haze formation rely on CH 4 as the source of carbon and treat CO 2 as a source of oxygen only, but this has not previously been verified experimentally. In the present work, we use isotopically labeled precursor gases and unit-mass resolution (UMR) and high-resolution (HR) aerosol mass spectrometry to examine the sources of carbon and oxygen to photochemical aerosol formed in a CH 4 /CO 2 /N 2 atmosphere. UMR results suggest that CH 4 contributes 70-100% of carbon in the aerosol, while HR results constrain the value from 94% to 100%. We also confirm that CO 2 contributes approximately 10% of the total mass to the aerosol as oxygen. These results have implications for the geochemical interpretations of inclusions found in Archean rocks on Earth and for the astrobiological potential of other planetary atmospheres. Key Words: Atmosphere-Early Earth-Planetary atmospheres-Carbon dioxide-Methane. Astrobiology 16, 822-830.

Design of an environmentally controlled rotating chamber for bioaerosol aging studies

PubMed Central

Verreault, Daniel; Duchaine, Caroline; Marcoux-Voiselle, Melissa; Turgeon, Nathalie; Roy, Chad J.

2015-01-01

A chamber was designed and built to study the long-term effects of environmental conditions on air-borne microorganisms. The system consists of a 55.5-L cylindrical chamber, which can rotate at variable speeds on its axis. The chamber is placed within an insulated temperature controlled enclosure which can be either cooled or heated with piezoelectric units. A germicidal light located at the chamber center irradiates at a 360° angle. Access ports are located on the stationary sections on both ends of the chamber. Relative humidity (RH) is controlled by passing the aerosol through meshed tubes surrounded by desiccant. Validation assay indicates that the interior temperature is stable with less than 0.5 °C in variation when set between 18 and 30 °C with the UV light having no effect of temperature during operation. RH levels set at 20%, 50% and 80% varied by 2.2%, 3.3% and 3.3%, respectively, over a 14-h period. The remaining fraction of particles after 18 h of suspension was 8.8% at 1 rotation per minute (rpm) and 2.6% at 0 rpm with the mass median aerodynamic diameter (MMAD) changing from 1.21 ± 0.04 μm to 1.30 ± 0.02 μm at 1 rpm and from 1.21 ± 0.04 μm to 0.91 ± 0.01 μm at 0 rpm within the same time period. This chamber can be used to increase the time of particle suspension in an aerosol cloud and control the temperature, RH and UV exposure; the design facilitates stationary sampling to be performed while the chamber is rotating. PMID:25055842

Altitude registration of limb-scattered radiation

NASA Astrophysics Data System (ADS)

Moy, Leslie; Bhartia, Pawan K.; Jaross, Glen; Loughman, Robert; Kramarova, Natalya; Chen, Zhong; Taha, Ghassan; Chen, Grace; Xu, Philippe

2017-01-01

One of the largest constraints to the retrieval of accurate ozone profiles from UV backscatter limb sounding sensors is altitude registration. Two methods, the Rayleigh scattering attitude sensing (RSAS) and absolute radiance residual method (ARRM), are able to determine altitude registration to the accuracy necessary for long-term ozone monitoring. The methods compare model calculations of radiances to measured radiances and are independent of onboard tracking devices. RSAS determines absolute altitude errors, but, because the method is susceptible to aerosol interference, it is limited to latitudes and time periods with minimal aerosol contamination. ARRM, a new technique introduced in this paper, can be applied across all seasons and altitudes. However, it is only appropriate for relative altitude error estimates. The application of RSAS to Limb Profiler (LP) measurements from the Ozone Mapping and Profiler Suite (OMPS) on board the Suomi NPP (SNPP) satellite indicates tangent height (TH) errors greater than 1 km with an absolute accuracy of ±200 m. Results using ARRM indicate a ˜ 300 to 400 m intra-orbital TH change varying seasonally ±100 m, likely due to either errors in the spacecraft pointing or in the geopotential height (GPH) data that we use in our analysis. ARRM shows a change of ˜ 200 m over ˜ 5 years with a relative accuracy (a long-term accuracy) of ±100 m outside the polar regions.

Secondary Organic Aerosol and Brown Carbon Formation in the Sunlit Aqueous Phase: Aldehyde Photooxidation in the Presence of Ammonium Salts and Amines

NASA Astrophysics Data System (ADS)

De Haan, D. O.; Galloway, M. M.; Sharp, K. D.; Jiménez, N. G.

2014-12-01

The chemistry of water-soluble carbonyl compounds in clouds is now acknowledged as an important source of secondary organic aerosol. These reactive carbonyl compounds are oxidized to carboxylic acids and form oligomers by radical-radical reactions and by "dark reactions" with ammonium salts (AS) and/or amines. The latter class of reactions also produces light-absorbing brown carbon compounds, especially reactions involving methylglyoxal or glyoxal and amines. However, recent work has found that UV light fades the color of glyoxal + AS and methylgyloxal + AS reaction mixtures. We recently studied aldehyde-AS-amine reactions in sunlight and in control vessels at the same temperature to determine the effects of solar radiation on the aqueous-phase production of brown carbon. In sunlight, methylglyoxal reaction mixtures lost their initial color and failed to brown, indicating the photolytic loss of reactants and/or pre-brown intermediates. In many other reactions, brown products are lost to photolysis, reducing the overall browning of solutions exposed to sunlight. In other experiments, hydrogen peroxide was added to generate OH radicals by photolysis. In the presence of OH radicals, some carbonyl compound mixtures (e.g. those containing hydroxyacetone or glycolaldehyde) browned more rapidly when exposed to sunlight. This indicates the existence of uncharacterized photooxidative browning pathways involving aqueous-phase OH radicals, carbonyls, ammonium salts, and/or amine compounds.

Towards PACE Atmospheric Correction, Aerosol and Cloud Products: Making Use of Expanded Spectral, Angular and Polarimetric Information.

NASA Astrophysics Data System (ADS)

Remer, L. A.; Boss, E.; Ahmad, Z.; Cairns, B.; Chowdhary, J.; Coddington, O.; Davis, A. B.; Dierssen, H. M.; Diner, D. J.; Franz, B. A.; Frouin, R.; Gao, B. C.; Garay, M. J.; Heidinger, A.; Ibrahim, A.; Kalashnikova, O. V.; Knobelspiesse, K. D.; Levy, R. C.; Omar, A. H.; Meyer, K.; Platnick, S. E.; Seidel, F. C.; van Diedenhoven, B.; Werdell, J.; Xu, F.; Zhai, P.; Zhang, Z.

2017-12-01

NASA's Science Team for the Plankton, Aerosol, Clouds, ocean Ecosystem (PACE) mission is concluding three years of study exploring the science potential of expanded spectral, angular and polarization capability for space-based retrievals of water leaving radiance, aerosols and clouds. The work anticipates future development of retrievals to be applied to the PACE Ocean Color Instrument (OCI) and/or possibly a PACE Multi-Angle Polarimeter (MAP). In this presentation we will report on the Science Team's accomplishments associated with the atmosphere (significant efforts are also directed by the ST towards the ocean). Included in the presentation will be sensitivity studies that explore new OCI capabilities for aerosol and cloud layer height, aerosol absorption characterization, cloud property retrievals, and how we intend to move from heritage atmospheric correction algorithms to make use of and adjust to OCI's hyperspectral and UV wavelengths. We will then address how capabilities will improve with the PACE MAP, how these capabilities from both OCI and MAP correspond to specific societal benefits from the PACE mission, and what is still needed to close the gaps in our understanding before the PACE mission can realize its full potential.

Glyoxal-methylglyoxal cross-reactions in secondary organic aerosol formation.

PubMed

Schwier, Allison N; Sareen, Neha; Mitroo, Dhruv; Shapiro, Erica L; McNeill, V Faye

2010-08-15

Glyoxal (G) and methylglyoxal (MG) are potentially important secondary organic aerosol (SOA) precursors. Previous studies of SOA formation by G and MG have focused on either species separately; however, G and MG typically coexist in the atmosphere. We studied the formation of secondary organic material in aqueous aerosol mimic mixtures containing G and MG with ammonium sulfate. We characterized the formation of light-absorbing products using UV-vis spectrophotometry. We found that absorption at 280 nm can be described well using models for the formation of light-absorbing products by G and MG in parallel. Pendant drop tensiometry measurements showed that surface tension depression by G and MG in these solutions can be modeled as a linear combination of the effects of G and MG alone. Product species were identified using chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol CIMS). Peaks consistent with G-MG cross-reaction products were observed, accounting for a significant fraction of detected product mass, but most peaks could be attributed to self-reaction. We conclude that cross-reactions contribute to SOA mass from uptake of G and MG, but they are not required to accurately model the effects of this process on aerosol surface tension or light absorption.

Long-term records of trace metal content of western Mediterranean seagrass (Posidonia oceanica) meadows: Natural and anthropogenic contributions

NASA Astrophysics Data System (ADS)

Tovar-SáNchez, Antonio; Serón, Juan; Marbã, Núria; Arrieta, Jesús M.; Duarte, Carlos M.

2010-06-01

We discuss Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents in seagrass Posidonia oceanica rhizomes from the Balearic Archipelago for the last 3 decades. Time series of metal concentration in P. oceanica were measured by dating rhizomes using retrospective procedures. The highest concentrations of Al (174.73 μg g-1), Cd (3.56 μg g-1), Cr (1.34 μg g-1), Cu (32.15 μg g-1), Pb (8.51 μg g-1), and Zn (107.14 μg g-1) were measured in meadows located around the largest and most densely populated island (Mallorca Island). There was a general tendency for Ag concentration to decrease with time (up to 80% from 1990 to 2005 in sample from Mallorca Island), which could be attributed to a reduction of the anthropogenic sources. Nickel and Zn concentrations were the unique elements that showed a consistent temporal trend in all samples, increasing their concentrations since year 1996 at all studied stations; this trend matched with the time series of UV-absorbing aerosols particles in the air (i.e., aerosols index) over the Mediterranean region (r2: 0.78, p < 0.001 for Cabrera Island), suggesting that P. oceanica could be an efficient recorder of dust events. A comparison of enrichment factors in rhizomes relative to average crustal material indicates that suspended aerosol is also the most likely source for Cr and Fe to P. oceanica.

COMPENSATIONAL THREE-WAVELENGTH DIFFERENTIAL-ABSORPTION LIDAR TECHNIQUE FOR REDUCING THE INFLUENCE OF DIFFERENTIAL SCATTERING ON OZONE-CONCENTRATION MEASUREMENTS.

EPA Science Inventory

A three-wavelength differential-absorption lidar (DIAL) technique for the UV spectral region is presented that reduces the influence of aerosol differential scattering on measured O3-concentration profiles. The principal advantage of this approach is that, to a good first approxi...

Reconstruction of daily solar UV irradiation from 1893 to 2002 in Potsdam, Germany

NASA Astrophysics Data System (ADS)

Junk, Jürgen; Feister, Uwe; Helbig, Alfred

2007-08-01

Long-term records of solar UV radiation reaching the Earth’s surface are scarce. Radiative transfer calculations and statistical models are two options used to reconstruct decadal changes in solar UV radiation from long-term records of measured atmospheric parameters that contain information on the effect of clouds, atmospheric aerosols and ground albedo on UV radiation. Based on earlier studies, where the long-term variation of daily solar UV irradiation was derived from measured global and diffuse irradiation as well as atmospheric ozone by a non-linear regression method [Feister et al. (2002) Photochem Photobiol 76:281 293], we present another approach for the reconstruction of time series of solar UV radiation. An artificial neural network (ANN) was trained with measurements of solar UV irradiation taken at the Meteorological Observatory in Potsdam, Germany, as well as measured parameters with long-term records such as global and diffuse radiation, sunshine duration, horizontal visibility and column ozone. This study is focussed on the reconstruction of daily broad-band UV-B (280 315 nm), UV-A (315 400 nm) and erythemal UV irradiation (ER). Due to the rapid changes in cloudiness at mid-latitude sites, solar UV irradiance exhibits appreciable short-term variability. One of the main advantages of the statistical method is that it uses doses of highly variable input parameters calculated from individual spot measurements taken at short time intervals, which thus do represent the short-term variability of solar irradiance.

Photoconductive ZnO Films Printed on Flexible Substrates by Inkjet and Aerosol Jet Techniques

NASA Astrophysics Data System (ADS)

Winarski, D. J.; Kreit, E.; Heckman, E. M.; Flesburg, E.; Haseman, M.; Aga, R. S.; Selim, F. A.

2018-02-01

Zinc oxide (ZnO) thin films have remarkable versatility in sensor applications. Here, we report simple ink synthesis and printing methods to deposit ZnO photodetectors on a variety of flexible and transparent substrates, including polyimide (Kapton), polyethylene terephthalate, cyclic olefin copolymer (TOPAS), and quartz. X-ray diffraction analysis revealed the dependence of the film orientation on the substrate type and sintering method, and ultraviolet-visible (UV-Vis) absorption measurements revealed a band edge near 380 nm. van der Pauw technique was used to measure the resistivity of undoped ZnO and indium/gallium-codoped ZnO (IGZO) films. IGZO films showed lower resistivity and larger average grain size compared with undoped ZnO films due to addition of In3+ and Ga3+, which act as donors. A 365-nm light-emitting diode was used to photoirradiate the films to study their photoconductive response as a function of light intensity at 300 K. The results revealed that ZnO films printed by aerosol jet and inkjet techniques exhibited five orders of magnitude photoconductivity, indicating that such films are viable options for use in flexible photodetectors.

Molecular Characterization of Brown Carbon (BrC) Chromophores in Secondary Organic Aerosol Generated From Photo-Oxidation of Toluene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Peng; Liu, Jiumeng; Shilling, John E.

Atmospheric Brown carbon (BrC) is a significant contributor to light absorption and climate forcing. However, little is known about a fundamental relationship between the chemical composition of BrC and its optical properties. In this work, light-absorbing secondary organic aerosol (SOA) was generated in the PNNL chamber from toluene photo-oxidation in the presence of NOx (Tol-SOA). Molecular structures of BrC components were examined using nanospray desorption electrospray ionization (nano-DESI) and liquid chromatography (LC) combined with UV/Vis spectroscopy and electrospray ionization (ESI) high-resolution mass spectrometry (HRMS). The chemical composition of BrC chromophores and the light absorption properties of toluene SOA (Tol-SOA) dependmore » strongly on the initial NOx concentration. Specifically, Tol-SOA generated under high-NOx conditions (defined here as initial NOx/toluene of 5/1) appears yellow and mass absorption coefficient of the bulk sample (MACbulk@365nm = 0.78 m2 g-1) is nearly 80 fold higher than that measured for the Tol-SOA sample generated under low-NOx conditions (NOx/toluene < 1/300). Fifteen compounds, most of which are nitrophenols, are identified as major BrC chromophores responsible for the enhanced light absorption of Tol-SOA material produced in the presence of NOx. The integrated absorbance of these fifteen chromophores accounts for 40-60% of the total light absorbance by Tol-SOA at wavelengths between 300 nm and 500 nm. The combination of tandem LC-UV/Vis-ESI/HRMS measurements provides an analytical platform for predictive understanding of light absorption properties by BrC and their relationship to the structure of individual chromophores. General trends in the UV/vis absorption by plausible isomers of the BrC chromophores were evaluated using theoretical chemistry calculations. The molecular-level understanding of BrC chemistry is helpful for better understanding the evolution and behavior of light absorbing aerosols in the atmosphere.« less

PM2.5 soluble brown-carbon measured in contrasting urban and rural environments

NASA Astrophysics Data System (ADS)

Weber, R.; Zhang, X.

2011-12-01

An instrument was developed to continuously measure the light absorption spectra and carbon mass of soluble PM2.5 components by coupling a particle-into-liquid sampler (PILS), UV-VIS (200-800nm) spectrophotometer with long-path absorption cell and total organic carbon (TOC) analyzer. The analytical system has also been used to measure brown carbon in aqueous extracts from integrated filters. Measurements have been conducted at a number of locations, including urban sites in Los Angeles, Atlanta and smaller urban and rural locations in the southeastern US. At all locations a characteristic brown carbon absorption spectra was observed, where soluble chromophores produce an increasing absorption with decreasing wavelength, starting from mid-visible and extending into the near UV. Incomplete combustion from biomass and fossil fuel burning and secondary processes have been identified as sources of soluble brown carbon. During summer when biomass burning impacts were minimal, mass absorption efficiencies calculated relative to ambient particle water-soluble organic carbon (WSOC) were highest in Los Angeles and correlated with the daily production of secondary organic aerosol. Nitro-aromatics were identified as a component of the brown carbon. In contrast, the Atlanta secondary aerosol was significantly less light-absorbing, and unlike Los Angeles the diurnal trend in brown carbon largely tracked primary sources. Absorption Angstrom exponents varied between 3 and 7 with fresh Los Angeles secondary organic aerosol associated with smaller exponents, indicting greater absorption into the visible spectrum. The southeastern US regional/rural brown carbon was the least absorbing per WSOC mass in the UV and with largest Angstrom exponents (7) the least absorbing at higher wavelengths. A correlation between the regional brown carbon and fine particle oxalate suggested an aqueous phase heterogeneous source for these chromophores. Compared to pure black carbon, brown carbon was optically significant at low wavelengths (365 nm) and most important in rural regions due to low black carbon concentrations.

Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

NASA Astrophysics Data System (ADS)

Savage, Nicole J.; Krentz, Christine E.; Könemann, Tobias; Han, Taewon T.; Mainelis, Gediminas; Pöhlker, Christopher; Huffman, J. Alex

2017-11-01

Atmospheric particles of biological origin, also referred to as bioaerosols or primary biological aerosol particles (PBAP), are important to various human health and environmental systems. There has been a recent steep increase in the frequency of published studies utilizing commercial instrumentation based on ultraviolet laser/light-induced fluorescence (UV-LIF), such as the WIBS (wideband integrated bioaerosol sensor) or UV-APS (ultraviolet aerodynamic particle sizer), for bioaerosol detection both outdoors and in the built environment. Significant work over several decades supported the development of the general technologies, but efforts to systematically characterize the operation of new commercial sensors have remained lacking. Specifically, there have been gaps in the understanding of how different classes of biological and non-biological particles can influence the detection ability of LIF instrumentation. Here we present a systematic characterization of the WIBS-4A instrument using 69 types of aerosol materials, including a representative list of pollen, fungal spores, and bacteria as well as the most important groups of non-biological materials reported to exhibit interfering fluorescent properties. Broad separation can be seen between the biological and non-biological particles directly using the five WIBS output parameters and by taking advantage of the particle classification analysis introduced by Perring et al. (2015). We highlight the importance that particle size plays on observed fluorescence properties and thus in the Perring-style particle classification. We also discuss several particle analysis strategies, including the commonly used fluorescence threshold defined as the mean instrument background (forced trigger; FT) plus 3 standard deviations (σ) of the measurement. Changing the particle fluorescence threshold was shown to have a significant impact on fluorescence fraction and particle type classification. We conclude that raising the fluorescence threshold from FT + 3σ to FT + 9σ does little to reduce the relative fraction of biological material considered fluorescent but can significantly reduce the interference from mineral dust and other non-biological aerosols. We discuss examples of highly fluorescent interfering particles, such as brown carbon, diesel soot, and cotton fibers, and how these may impact WIBS analysis and data interpretation in various indoor and outdoor environments. The performance of the particle asymmetry factor (AF) reported by the instrument was assessed across particle types as a function of particle size, and comments on the reliability of this parameter are given. A comprehensive online supplement is provided, which includes size distributions broken down by fluorescent particle type for all 69 aerosol materials and comparing threshold strategies. Lastly, the study was designed to propose analysis strategies that may be useful to the broader community of UV-LIF instrumentation users in order to promote deeper discussions about how best to continue improving UV-LIF instrumentation and results.

Long-term variability of UV irradiance over Northern Eurasia according to satellite measurements, ERA-INTERIM dataset and INM-RSHU chemical climate model

NASA Astrophysics Data System (ADS)

Chubarova, Nataly; Pastukhova, Anna; Zhdanova, Ekaterina; Khlestova, Julia; Poliukhov, Alexei; Smyshlyaev, Sergei; Galin, Vener

2017-04-01

We present the results of long-term erythemal UV irradiance (ERY) changes over the territory of Northern Eurasia according to the ERA-INTERIM reanalysis dataset, INM-RSHU chemical climate model (CCM), and TOMS and OMI satellite data with the correction on absorbing aerosol based on the new Macv2 climatology updated from Kinne et al. (2013) over the 1979-2015 period. We show the existence of the pronounced positive ERY trend due to ozone in spring and summer over Europe and over the central areas of Siberia (up 3% over the decade). The changes in cloud cover provide even more significant ERY increase (up to 6-8% per decade). However, over Arctic region there is a pronounced negative ERY trend probably due to the effects of melting ice on global circulation processes. The combination of ozone and cloud effects provides the enhanced increase of the overall ERY trend: up to 6-9% in spring and summer over Eastern Europe, some regions of Siberia and the Far East. In addition, based on the method described in (Chubarova, Zhdanova, 2013) we estimated changes in UV resources over Northern Eurasia since 1979. We show that for the first skin type there is a significant geographical shift of UV categories: the increase in the UV optimum area in winter, where the vitamin D generation is possible without risk of getting sunburn, and its reducing in other months due to decrease in ozone and clouds. We also analyze the long-term UV changes simulated according to different scenarios using the INM-RSHU CCM. There is a general agreement between CCM and observational datasets, however, ERY trends due to cloudiness do not correspond sometimes in space and are smaller. We show that the positive ERY trend due to ozone is determined by the anthropogenic emissions of halogens. The variations in natural factors (solar activity and ocean surface temperature, stratospheric aerosol) only provide the increase in ERY dispersion. References: Kinne, S., O'Donnel D., Stier P., et al., J. Adv. Model. Earth Syst., 5, 704-740, 2013. Chubarova N., Zhdanova Ye. Photochemistry and Photobiology. - 2013. - Vol. 127. - P. 38-51.

Overview of the O3M SAF GOME-2 operational atmospheric composition and UV radiation data products and data availability

NASA Astrophysics Data System (ADS)

Hassinen, S.; Balis, D.; Bauer, H.; Begoin, M.; Delcloo, A.; Eleftheratos, K.; Gimeno Garcia, S.; Granville, J.; Grossi, M.; Hao, N.; Hedelt, P.; Hendrick, F.; Hess, M.; Heue, K.-P.; Hovila, J.; Jønch-Sørensen, H.; Kalakoski, N.; Kiemle, S.; Kins, L.; Koukouli, M. E.; Kujanpää, J.; Lambert, J.-C.; Lerot, C.; Loyola, D.; Määttä, A.; Pedergnana, M.; Pinardi, G.; Romahn, F.; van Roozendael, M.; Lutz, R.; De Smedt, I.; Stammes, P.; Steinbrecht, W.; Tamminen, J.; Theys, N.; Tilstra, L. G.; Tuinder, O. N. E.; Valks, P.; Zerefos, C.; Zimmer, W.; Zyrichidou, I.

2015-07-01

The three GOME-2 instruments will provide unique and long data sets for atmospheric research and applications. The complete time period will be 2007-2022, including the period of ozone depletion as well as the beginning of ozone layer recovery. Besides ozone chemistry, the GOME-2 products are important e.g. for air quality studies, climate modeling, policy monitoring and hazard warnings. The heritage for GOME-2 is in the ERS/GOME and Envisat/SCIAMACHY instruments. The current Level 2 (L2) data cover a wide range of products such as trace gas columns (NO2, BrO, H2CO, H2O, SO2), tropospheric columns of NO2, total ozone columns and vertical ozone profiles in high and low spatial resolution, absorbing aerosol indices from the main science channels as well as from the polarization channels (AAI, AAI-PMD), Lambertian-equivalent reflectivity database, clear-sky and cloud-corrected UV indices and surface UV fields with different weightings and photolysis rates. The Ozone Monitoring and Atmospheric Composition Satellite Application Facility (O3M SAF) processing and data dissemination is operational and running 24/7. Data quality is quarantined by the detailed review processes for the algorithms, validation of the products as well as by a continuous quality monitoring of the products and processing. This is an overview paper providing the O3M SAF project background, current status and future plans to utilization of the GOME-2 data. An important focus is the provision of summaries of the GOME-2 products including product principles and validation examples together with the product sample images. Furthermore, this paper collects the references to the detailed product algorithm and validation papers.

Incorporation of multiple cloud layers for ultraviolet radiation modeling studies

NASA Technical Reports Server (NTRS)

Charache, Darryl H.; Abreu, Vincent J.; Kuhn, William R.; Skinner, Wilbert R.

1994-01-01

Cloud data sets compiled from surface observations were used to develop an algorithm for incorporating multiple cloud layers into a multiple-scattering radiative transfer model. Aerosol extinction and ozone data sets were also incorporated to estimate the seasonally averaged ultraviolet (UV) flux reaching the surface of the Earth in the Detroit, Michigan, region for the years 1979-1991, corresponding to Total Ozone Mapping Spectrometer (TOMS) version 6 ozone observations. The calculated UV spectrum was convolved with an erythema action spectrum to estimate the effective biological exposure for erythema. Calculations show that decreasing the total column density of ozone by 1% leads to an increase in erythemal exposure by approximately 1.1-1.3%, in good agreement with previous studies. A comparison of the UV radiation budget at the surface between a single cloud layer method and a multiple cloud layer method presented here is discussed, along with limitations of each technique. With improved parameterization of cloud properties, and as knowledge of biological effects of UV exposure increase, inclusion of multiple cloud layers may be important in accurately determining the biologically effective UV budget at the surface of the Earth.

Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.;

A Fast Hyperspectral Vector Radiative Transfer Model in UV to IR spectral bands

NASA Astrophysics Data System (ADS)

Ding, J.; Yang, P.; Sun, B.; Kattawar, G. W.; Platnick, S. E.; Meyer, K.; Wang, C.

2016-12-01

We develop a fast hyperspectral vector radiative transfer model with a spectral range from UV to IR with 5 nm resolutions. This model can simulate top of the atmosphere (TOA) diffuse radiance and polarized reflectance by considering gas absorption, Rayleigh scattering, and aerosol and cloud scattering. The absorption component considers several major atmospheric absorbers such as water vapor, CO2, O3, and O2 including both line and continuum absorptions. A regression-based method is used to parameterize the layer effective optical thickness for each gas, which substantially increases the computation efficiency for absorption while maintaining high accuracy. This method is over 500 times faster than the existing line-by-line method. The scattering component uses the successive order of scattering (SOS) method. For Rayleigh scattering, convergence is fast due to the small optical thickness of atmospheric gases. For cloud and aerosol layers, a small-angle approximation method is used in SOS calculations. The scattering process is divided into two parts, a forward part and a diffuse part. The scattering in the small-angle range in the forward direction is approximated as forward scattering. A cloud or aerosol layer is divided into thin layers. As the ray propagates through each thin layer, a portion diverges as diffuse radiation, while the remainder continues propagating in forward direction. The computed diffuse radiance is the sum of all of the diffuse parts. The small-angle approximation makes the SOS calculation converge rapidly even in a thick cloud layer.

MIRA: review of inputs from updated results of the phobos mission

NASA Astrophysics Data System (ADS)

Moroz, V. I.; Korablev, O. I.; Rodin, A. V.; Titov, D. V.

1999-01-01

The future Mars International Reference Atmosphere (MIRA) is intended to replace the present COSPAR Mars Reference Model compiled in 1979 on the basis of Mariner 9 and Viking 1,2 missions results. At the moment, several sources of the post-Viking data potentially useful for MIRA are available. Among them is a data set obtained during Phobos mission in 1989. The interpretation of these data has undergone thorough refinement, so final recommendations for MIRA can be made. The principal points are: 1) vertical profile of water vapor with a ``knee'' at the height about 25 km retrieved in the spring equinox season near equator; 2) variations of water vapor column density including peculiarities on the slopes of high mountains; 3) vertical profiles of ozone; 4) new estimates of CO abundance; 5) surface pressure/height mapping (CO2 altimetry) in selected regions; 6) optical depths of aerosols; 7) vertical profiles of aerosol between surface and 40 km; 8) properties of high altitude ice layers and clouds above mountains; 9) microphysical properties of aerosol particles (size, composition, and number density estimates). The data have been obtained by means of instruments AUGUSTE (UV and NIR spectrometers for limb sounding of the atmosphere using solar occultations), ISM (NIR scanning spectrometer), TERMOSKAN (thermal IR scanning radiometer), KRFM (near-UV and visible multi-band photometer). The observations were performed in equatorial regions during northern spring (solar aerocentric longitudes 8° < Ls < 18°).

Direct fluorescent labeling for efficient biological assessment of inhalable particles.

PubMed

Poudel, Bijay Kumar; Park, Jae Hong; Lim, Jiseok; Byeon, Jeong Hoon

2017-10-01

Labeling of aerosol particles with a radioactive, magnetic, or optical tracer has been employed to confirm particle localization in cell compartments, which has provided useful evidence for correlating toxic effects of inhaled particles. However, labeling requires several physicochemical steps to identify functionalities of the inner or outer surfaces of particles, and moreover, these steps can cause changes in size, surface charge, and bioactivity of the particles, resulting in misinterpretations regarding their toxic effects. This study addresses this challenging issue with a goal of introducing an efficient strategy for constantly supplying labeled aerosol particles in a single-pass configuration without any pre- or post-physicochemical batch treatments of aerosol particles. Carbon black (CB, simulating combustion-generated soot) or calcium carbonate (CC, simulating brake-wear fragments) particles were constantly produced via spark ablation or bubble bursting, respectively. These minute particles were incorporated with fluorescein isothiocyanate-poly(ethylene glycol) 2-aminoethyl ether acetic acid solution at the orifice of a collison atomizer to fabricate hybrid droplets. The droplets successively entered a diffusion dryer containing 254-nm UV irradiation; therefore, the droplets were dynamically stiffened by UV to form fluorescent probes on particles during solvent extraction in the dryer. Particle size distributions, morphologies, and surface charges before and after labeling were measured to confirm fluorescence labeling without significant changes in the properties. In vitro assays, including confocal imaging, were conducted to confirm the feasibility of the labeling approach without inducing significant differences in bioactivity compared with untreated CB or CC particles.

13C and 15N fractionation of CH4/N2 mixtures during photochemical aerosol formation: Relevance to Titan

NASA Astrophysics Data System (ADS)

Sebree, Joshua A.; Stern, Jennifer C.; Mandt, Kathleen E.; Domagal-Goldman, Shawn D.; Trainer, Melissa G.

2016-05-01

The ratios of the stable isotopes that comprise each chemical species in Titan's atmosphere provide critical information towards understanding the processes taking place within its modern and ancient atmosphere. Several stable isotope pairs, including 12C/13C and 14N/15N, have been measured in situ or probed spectroscopically by Cassini-borne instruments, space telescopes, or through ground-based observations. Current attempts to model the observed isotope ratios incorporate fractionation resulting from atmospheric diffusion, hydrodynamic escape, and primary photochemical processes. However, the effect of a potentially critical pathway for isotopic fractionation - organic aerosol formation and subsequent deposition onto the surface of Titan - has not been considered due to insufficient data regarding fractionation during aerosol formation. To better understand the nature of this process, we have conducted a laboratory study to measure the isotopic fractionation associated with the formation of Titan aerosol analogs, commonly referred to as 'tholins', via far-UV irradiation of several methane (CH4) and dinitrogen (N2) mixtures. Analysis of the δ13C and δ15N isotopic signatures of the photochemical aerosol products using an isotope ratio mass spectrometer (IRMS) show that fractionation direction and magnitude are dependent on the initial bulk composition of the gas mixture. In general, the aerosols showed enrichment in 13C and 14N, and the observed fractionation trends can provide insight into the chemical mechanisms controlling photochemical aerosol formation.

Ozone and Aerosol Retrieval from Backscattered Ultraviolet Radiation

NASA Technical Reports Server (NTRS)

Bhartia, Pawan K.

2012-01-01

In this presentation we will discuss the techniques to estimate total column ozone and aerosol absorption optical depth from the measurements of back scattered ultraviolet (buv) radiation. The total ozone algorithm has been used to create a unique record of the ozone layer, spanning more than 3 decades, from a series of instruments (BUV, SBUV, TOMS, SBUV/2) flown on NASA, NOAA, Japanese and Russian satellites. We will discuss how this algorithm can be considered a generalization of the well-known Dobson/Brewer technique that has been used to process data from ground-based instruments for many decades, and how it differs from the DOAS techniques that have been used to estimate vertical column densities of a host of trace gases from data collected by GOME and SCIAMACHY instruments. The buv aerosol algorithm is most suitable for the detection of UV absorbing aerosols (smoke, desert dust, volcanic ash) and is the only technique that can detect aerosols embedded in clouds. This algorithm has been used to create a quarter century record of aerosol absorption optical depth using the buv data collected by a series of TOMS instruments. We will also discuss how the data from the OMI instrument launched on July 15, 2004 will be combined with data from MODIS and CALIPSO lidar data to enhance the accuracy and information content of satellite-derived aerosol measurements. The OMI and MODIS instruments are currently flying on EOS Aura and EOS Aqua satellites respectively, part of a constellation of satellites called the "A-train".

Investigation of the CCN Activity, BC and UVBC Mass Concentrations of Biomass Burning Aerosols during the 2013 BASELInE Campaign

NASA Technical Reports Server (NTRS)

Hsiao, Ta-Chih; Ye, Wei-Cheng; Wang, Sheng-Hsiang; Tsay, Si-Chee; Chen, Wei-Nai; Lin, Neng-Huei; Lee, Chung-Te; Hung, Hui-Ming; Chuang, Ming-Tung; Chantara, Somporn

2015-01-01

Biomass-burning (BB) aerosols, acting as cloud condensation nuclei (CCN), can influence cloud microphysical and radiative properties. In this study, we present CCN measured near the BB source regions over northern Southeast Asia (Doi Ang Khang, Thailand) and at downwind receptor areas (Lulin Atmospheric Background Station, Taiwan), focusing exclusively on 13-20 March 2013 as part of 2013 spring campaign of the Seven SouthEast Asian Studies (7-SEAS) intensive observation. One of the campaigns objectives is to characterize BB aerosols serving as CCN in SouthEast Asia (SEA). CCN concentrations were measured by a CCN counter at 5 supersaturation (SS) levels: 0.15%, 0.30%, 0.45%, 0.60%, and 0.75%. In addition, PM2.5 and black carbon mass concentrations were analyzed by using a tapered element oscillating microbalance and an aethalometer. It was found the number-size distributions and the characteristics of hygroscopicity (e.g., activation ratio and k) of BB aerosols in SEA have a strong diurnal pattern, and different behaviors of patterns were characterized under two distinct weather systems. The overall average value was low (0.05-0.1) but comparable with previous CCN studies in other BB source regions. Furthermore, a large fraction of UV-absorbing organic material (UVBC) and high Delta-C among BB aerosols were also observed, which suggest the existence of substantial particulate organic matter in fresh BB aerosols. These data provide the most extensive characterization of BB aerosols in SEA until now.

Calculation of Brown Carbon Optical Properties in the Fifth version Community Atmospheric Model (CAM5) and Validation with a Case Study in Kanpur, India

NASA Astrophysics Data System (ADS)

Xu, L.; Peng, Y.; Ram, K.

2017-12-01

The presence of absorbing component of organic carbon in atmospheric aerosols (Brown Carbon, BrC) has recently received much attention to the scientific community because of its absorbing nature, especially in the UV and Visible region. Attempts to account for BrC in radiative forcing calculations in climate model are rather scarce, primarily due to observational constrain as well as its incorporation in the model-based studies. Due to non-treatment of BrC in the off-line models, there exists a large discrepancy between model- and observational- based estimate of direct radiative effect of carbonaceous aerosols. In this study, we have included BrC absorption and optical characteristics in the fifth version of Community Atmospheric Model (CAM5) for the better understanding of radiative impact of BrC over northern India, also for improving the performance of aerosol radiative calculation in climate model. We have used the inputs of aerosol chemical composition measurements conducted at an urban site, Kanpur, in the Indo-Gangetic Plain (IGP) during 2007-2008 to construct the optical properties of BrC in CAM5 model. Model radiative simulations of sensitive tests showed good agreement with observations. Effects of varying imaginary part of BrC refractive index, relative mass ratio of BrC to organic aerosol in combination with core-shell mixing style of BrC with other anthropogenic aerosols are also analyzed for understanding BrC impact on simulated aerosol absorption in model.

Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols.

PubMed

Thomas, Daniel A; Coggon, Matthew M; Lignell, Hanna; Schilling, Katherine A; Zhang, Xuan; Schwantes, Rebecca H; Flagan, Richard C; Seinfeld, John H; Beauchamp, J L

2016-11-15

The complexation of iron(III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron(II) and the carbon dioxide anion radical. Importantly, iron(III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown. This study utilizes glycolaldehyde as a model organic species to examine the oxidation pathways and evolution of organic aerosol initiated by the photodissociation of aqueous iron(III) oxalate complexes. Hanging droplets (radius 1 mm) containing iron(III), oxalic acid, glycolaldehyde, and ammonium sulfate (pH ∼3) are exposed to irradiation at 365 nm and sampled at discrete time points utilizing field-induced droplet ionization mass spectrometry (FIDI-MS). Glycolaldehyde is found to undergo rapid oxidation to form glyoxal, glycolic acid, and glyoxylic acid, but the formation of high molecular weight oligomers is not observed. For comparison, particle-phase experiments conducted in a laboratory chamber explore the reactive uptake of gas-phase glycolaldehyde onto aqueous seed aerosol containing iron and oxalic acid. The presence of iron oxalate in seed aerosol is found to inhibit aerosol growth. These results suggest that photodissociation of iron(III) oxalate can lead to the formation of volatile oxidation products in tropospheric aqueous aerosols.

Evaluation of spatio-temporal variability of Hamburg Aerosol Climatology against aerosol datasets from MODIS and CALIOP

NASA Astrophysics Data System (ADS)

Pappas, V.; Hatzianastassiou, N.; Papadimas, C.; Matsoukas, C.; Kinne, S.; Vardavas, I.

2013-02-01

The new global aerosol climatology named HAC (Hamburg Aerosol Climatology) is compared against MODIS (MODerate resolution Imaging Spectroradiometer, Collection 5, 2000-2007) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization, Level 2-Version 3, 2006-2011) retrievals. The HAC aerosol optical depth (AOD) values are larger than MODIS in heavy aerosol load conditions (over land) and lower over oceans. Agreement between HAC and MODIS is better over land and for low AOD. Hemispherically, HAC has 16-17% smaller AOD values than MODIS. The discrepancy is slightly larger for the Southern Hemisphere (SH) than for the Northern Hemisphere (NH). Seasonally, the largest absolute differences are from March to August for NH and from September to February for SH. The spectral variability of HAC AOD is also evaluated against AERONET (1998-2007) data for sites representative of main aerosol types (pollutants, sea-salt, biomass and dust). The HAC has a stronger spectral dependence of AOD in the UV wavelengths, compared to AERONET and MODIS. For visible and near-infrared wavelengths, the spectral dependence is similar to AERONET. For specific sites, HAC AOD vertical distribution is compared to CALIOP data by looking at the fraction of columnar AOD at each altitude. The comparison suggests that HAC exhibits a smaller fraction of columnar AOD in the lowest 2-3 km than CALIOP, especially for sites with biomass burning smoke, desert dust and sea salt spray. For the region of the greater Mediterranean basin, the mean profile of HAC AOD is in very good agreement with CALIOP. The HAC AOD is very useful for distinguishing between natural and anthropogenic aerosols and provides high spectral resolution and vertically resolved information.

African aerosols and Atlantic tropical cyclone activities

NASA Astrophysics Data System (ADS)

Kafatos, M.; Sun, D.; Sahoo, A.

2006-12-01

Previous studies have shown that the Atlantic basin major hurricane (MH) activity is associated with western Sahelian monsoon rainfall, while rainfall in the Sahel is found to be highly anti-correlated with the African dust storms. So if the Atlantic basin MH activity may be anti-correlated with the African dust aerosols? In order to investigate the relationship between the African dust and the tropical cyclone (including both tropical storms and hurricanes) activities in the Atlantic basin, we explore how the African dust may link to Atlantic TC activity by using the long-term (1982-2005) NCEP Reynolds sea surface temperature (SST) product, and tropical cyclone (TC) data from the National Hurricane Center Best Track Files, and the TOMS aerosol index (AI) data, because the TOMS AI positive values are associated with UV-absorbing aerosols, like dust and smoke. Although no significant negative correlation between the TOMS AI and the Atlantic TC or MH frequency and duration is found, the initial locations of the Atlantic tropical cyclones did occur over the ocean where the aerosol loading was low. Our analysis shows that SST over the north tropical Atlantic ocean is anti-correlated with the TOMS aerosol index. This may be due to the radiative forcing of the aerosols. The effects of the dust aerosols carried across the West African region led to a lowering of SST and therefore inhibited tropical cyclogenesis. During 2005, the aerosol loading along the western African coast was unusually low, while the SST over the main development region (MDR) was abnormally high, and the Atlantic TC/hurricane activities became record strong. We propose future observations to test these results.

Raman lidar observations of particle hygroscopicity during COPS

NASA Astrophysics Data System (ADS)

Stelitano, D.; Di Girolamo, P.; Summa, D.

2012-04-01

The characterization of particle hygroscopicity has primary importance for climate monitoring and prediction. Model studies have demonstrated that relative humidity (RH) has a critical influence on aerosol climate forcing. The relationship between aerosol backscattering and relative humidity has been investigated in numerous studies (among others, Pahlow et al., 2006; Wulfmeyer and Feingold, 2000; Veselovskii et al., 2009). Hygroscopic properties of aerosols influence particle size distribution and refractive index and hence their radiative effects. Aerosol particles tend to grow at large relative humidity values as a result of their hygroscopicity. Raman lidars with aerosol, water vapour and temperature measurement capability are potentially attractive tools for studying aerosol hygroscopicity as in fact they can provide continuous altitude-resolved measurements of particle optical, size and microphysical properties, as well as relative humidity, without perturbing the aerosols or their environment. Specifically, the University of Basilicata Raman lidar system (BASIL) considered for the present study, has the capability to perform all-lidar measurements of relative humidity based on the application of both the rotational and the vibrational Raman lidar techniques in the UV. BASIL was operational in Achern (Black Forest, Lat: 48.64 ° N, Long: 8.06 ° E, Elev.: 140 m) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). During COPS, BASIL collected more than 500 hours of measurements, distributed over 58 measurement days and 34 intensive observation periods (IOPs). The present analysis is focused on selected case studies characterized by the presence of different aerosol types with different hygroscopic behaviour. The observed behaviour, dependent upon aerosol composition, may range from hygrophobic to strongly hygroscopic. Results from the different case studies will be illustrated and discussed at the Conference.

Lidar measurements of polar stratospheric clouds during the 1989 airborne Arctic stratospheric expedition

NASA Technical Reports Server (NTRS)

Ismail, Syed; Browell, Edward V.

1991-01-01

The Airborne Arctic Stratospheric Expedition (AASE) was conducted during January to February 1989 from the Sola Air Station, Norway. As part of this expedition, the NASA Langley Research Center's multiwavelength airborne lidar system was flown on the NASA Ames Research Center's DC-8 aircraft to measure ozone (O3) and aerosol profiles in the region of the polar vortex. The lidar system simultaneously transmitted laser beams at 1064, 603, 311, and 301.5 nm to measure atmospheric scattering, polarization and O3 profiles. Long range flights were made between Stavanger, Norway, and the North Pole, and between 40 deg W and 20 deg E meridians. Eleven flights were made, each flight lasting an average of 10 hours covering about 8000 km. Atmospheric scattering ratios, aerosol polarizations, and aerosol scattering ratio wavelength dependences were derived from the lidar measurements to altitudes above 27 km. The details of the aerosol scattering properties of lidar observations in the IR, VIS, and UV regions are presented along with correlations with the national meteorological Center's temperature profiles.

ATLID, the atmospheric lidar on board the Earthcare Satellite

NASA Astrophysics Data System (ADS)

Hélière, Arnaud; Gelsthorpe, Robert; Le Hors, Lénaïc.; Toulemont, Yves

2017-11-01

The EarthCARE mission is the sixth Earth Explorer Mission of the ESA Living Planet Programme, with a launch date planned in 2015. It addresses the interaction and impact of clouds and aerosols on the Earth's radiative budget. ATLID (ATmospheric LIDar), one of the four instruments of EarthCARE, shall determine vertical profiles of cloud and aerosol physical parameters (altitude, optical depth, backscatter ratio and depolarisation ratio) in synergy with other instruments. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes with a vertical resolution of about 100 m from ground to an altitude of 40 km. As a result of high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. The purpose of the paper is to present the progress in the instrument and subsystem design. The instrument is currently in phase C where the detailed design of all sub-systems is being performed. Emphasis will be put on the major technological developments, in particular the laser Transmitter, the optical units and detector developments.

Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.

2000-01-01

The largest uncertainty in estimates of the effects of atmospheric aerosols on climate stems from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction, which in turn determines their optical properties. A novel technique is used to estimate the aerosol complex index of refraction in distinct vertical layers from a combination of aerosol in situ size distribution and remote sensing measurements during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). In particular, aerosol backscatter measurements using the NASA Langley LASE (Lidar Atmospheric Sensing Experiment) instrument and in situ aerosol size distribution data are utilized to derive vertical profiles of the 'effective' aerosol complex index of refraction at 815 nm (i.e., the refractive index that would provide the same backscatter signal in a forward calculation on the basis of the measured in situ particle size distributions for homogeneous, spherical aerosols). A sensitivity study shows that this method yields small errors in the retrieved aerosol refractive indices, provided the errors in the lidar derived aerosol backscatter are less than 30% and random in nature. Absolute errors in the estimated aerosol refractive indices are generally less than 0.04 for the real part and can be as much as 0.042 for the imaginary part in the case of a 30% error in the lidar-derived aerosol backscatter. The measurements of aerosol optical depth from the NASA Ames Airborne Tracking Sunphotometer (AATS-6) are successfully incorporated into the new technique and help constrain the retrieved aerosol refractive indices. An application of the technique to two TARFOX case studies yields the occurrence of vertical layers of distinct aerosol refractive indices. Values of the estimated complex aerosol refractive index range from 1.33 to 1.45 for the real part and 0.001 to 0.008 for the imaginary part. The methodology devised in this study provides, for the first time a complete set of vertically resolved aerosol size distribution and refractive index data, yielding the vertical distribution of aerosol optical properties required for the determination of aersol-induced radiative flux changes

Transformation of logwood combustion emissions in a smog chamber: formation of secondary organic aerosol and changes in the primary organic aerosol upon daytime and nighttime aging

NASA Astrophysics Data System (ADS)

Tiitta, Petri; Leskinen, Ari; Hao, Liqing; Yli-Pirilä, Pasi; Kortelainen, Miika; Grigonyte, Julija; Tissari, Jarkko; Lamberg, Heikki; Hartikainen, Anni; Kuuspalo, Kari; Kortelainen, Aki-Matti; Virtanen, Annele; Lehtinen, Kari E. J.; Komppula, Mika; Pieber, Simone; Prévôt, André S. H.; Onasch, Timothy B.; Worsnop, Douglas R.; Czech, Hendryk; Zimmermann, Ralf; Jokiniemi, Jorma; Sippula, Olli

2016-10-01

Organic aerosols (OA) derived from small-scale wood combustion emissions are not well represented by current emissions inventories and models, although they contribute substantially to the atmospheric particulate matter (PM) levels. In this work, a 29 m3 smog chamber in the ILMARI facility of the University of Eastern Finland was utilized to investigate the formation of secondary organic aerosol (SOA) from a small-scale modern masonry heater commonly used in northern Europe. Emissions were oxidatively aged in the smog chamber for a variety of dark (i.e., O3 and NO3) and UV (i.e., OH) conditions, with OH concentration levels of (0.5-5) × 106 molecules cm-3, achieving equivalent atmospheric aging of up to 18 h. An aerosol mass spectrometer characterized the direct OA emissions and the SOA formed from the combustion of three wood species (birch, beech and spruce) using two ignition processes (fast ignition with a VOC-to-NOx ratio of 3 and slow ignition with a ratio of 5).Dark and UV aging increased the SOA mass fraction with average SOA productions 2.0 times the initial OA mass loadings. SOA enhancement was found to be higher for the slow ignition compared with fast ignition conditions. Positive matrix factorization (PMF) was used to separate SOA, primary organic aerosol (POA) and their subgroups from the total OA mass spectra. PMF analysis identified two POA and three SOA factors that correlated with the three major oxidizers: ozone, the nitrate radical and the OH radical. Organonitrates (ONs) were observed to be emitted directly from the wood combustion and additionally formed during oxidation via NO3 radicals (dark aging), suggesting small-scale wood combustion may be a significant ON source. POA was oxidized after the ozone addition, forming aged POA, and after 7 h of aging more than 75 % of the original POA was transformed. This process may involve evaporation and homogeneous gas-phase oxidation as well as heterogeneous oxidation of particulate organic matter. The results generally prove that logwood burning emissions are the subject of intensive chemical processing in the atmosphere, and the timescale for these transformations is relatively short, i.e., hours.

Measurement of Aerosol and Cloud Particles with PACS and HARP Hyperangular Imaging Polarimeters

NASA Astrophysics Data System (ADS)

Martins, J.; Fernandez-Borda, R.; Remer, L. A.; Sparr, L.; Buczkowski, S.; Munchak, L. A.

2013-12-01

PACS is new hyper-angular imaging polarimeter for aeorosol and cloud measurerents designed to meet the requirements of the proposed ACE decadal survey mission. The full PACS system consists of three wide field of view (110deg cross track) telescopes covering the UV, VNIR, and SWIR spectral ranges with angular coverage between +55 deg forward to -55deg backwards. The angular density can be selected to cover up to 100 different viewing angles at selected wavelengths. PACS_VNIR is a prototype airborne instrument designed to demonstrate PACS capability by deploying just one of the three wavelength modules of the full PACS. With wavelengths at 470, 550, 675, 760 and 875nm, PACS_VNIR flew for the first time during the PODEX experiment in January/February 2013 aboard the NASA ER-2 aircraft. PACS SWIR (1.64, 1.88, 2.1, and 2.25um) is currently under construction and should be operational in the lab by Fall/2013. PACS_ UV has been fully designed, but is not yet under construction. During the PODEX flights PACS_VNIR collected data for aerosol and clouds over variable surface types including, water, vegetation, urban areas, and snow. The data is currently being calibrated, geolocated and prepared for the inversion of geophysical parameters including water cloud size distribution and aerosol microphysical parameters. The large density of angles in PACS allows for the characterization of cloudbow features in relatively high spatial resolution in a pixel to pixel basis. This avoids the need for assumptions of cloud homogeneity over any distance. The hyperangle capability also allows detailed observation of cloud ice particles, surface characterization, and optimum selection of the number of angles desired for aerosol retrievals. The aerosol and cloud retrieval algorithms under development for the retrieval of particle microphysical properties from the PACS data will be discussed in this presentation. As an extension of the PACS concept we are currently developing the HARP (Hyper-Angular Rainbow Polarimeter) Cubesat satellite funded by the NASA/ESTO/InVEST program. HARP will demonstrate the PACS concept from space and will allow for high resolution angular measurements of polarized radiances over different aerosol and cloud scenarios. The HARP concept and strategy will be presented and discussed as part of the general PACS measurement strategy.

LIVAS: a 3-D multi-wavelength aerosol/cloud database based on CALIPSO and EARLINET

NASA Astrophysics Data System (ADS)

Amiridis, V.; Marinou, E.; Tsekeri, A.; Wandinger, U.; Schwarz, A.; Giannakaki, E.; Mamouri, R.; Kokkalis, P.; Binietoglou, I.; Solomos, S.; Herekakis, T.; Kazadzis, S.; Gerasopoulos, E.; Proestakis, E.; Kottas, M.; Balis, D.; Papayannis, A.; Kontoes, C.; Kourtidis, K.; Papagiannopoulos, N.; Mona, L.; Pappalardo, G.; Le Rille, O.; Ansmann, A.

2015-07-01

We present LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), a 3-D multi-wavelength global aerosol and cloud optical database, optimized to be used for future space-based lidar end-to-end simulations of realistic atmospheric scenarios as well as retrieval algorithm testing activities. The LIVAS database provides averaged profiles of aerosol optical properties for the potential spaceborne laser operating wavelengths of 355, 532, 1064, 1570 and 2050 nm and of cloud optical properties at the wavelength of 532 nm. The global database is based on CALIPSO observations at 532 and 1064 nm and on aerosol-type-dependent backscatter- and extinction-related Ångström exponents, derived from EARLINET (European Aerosol Research Lidar Network) ground-based measurements for the UV and scattering calculations for the IR wavelengths, using a combination of input data from AERONET, suitable aerosol models and recent literature. The required spectral conversions are calculated for each of the CALIPSO aerosol types and are applied to CALIPSO backscatter and extinction data corresponding to the aerosol type retrieved by the CALIPSO aerosol classification scheme. A cloud optical database based on CALIPSO measurements at 532 nm is also provided, neglecting wavelength conversion due to approximately neutral scattering behavior of clouds along the spectral range of LIVAS. Averages of particle linear depolarization ratio profiles at 532 nm are provided as well. Finally, vertical distributions for a set of selected scenes of specific atmospheric phenomena (e.g., dust outbreaks, volcanic eruptions, wild fires, polar stratospheric clouds) are analyzed and spectrally converted so as to be used as case studies for spaceborne lidar performance assessments. The final global data set includes 4-year (1 January 2008-31 December 2011) time-averaged CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) data on a uniform grid of 1° × 1° with the original high vertical resolution of CALIPSO in order to ensure realistic simulations of the atmospheric variability in lidar end-to-end simulations.

Evolution of wavelength-dependent mass absorption cross sections of carbonaceous aerosols during the 2010 DOE CARES campaign

NASA Astrophysics Data System (ADS)

Flowers, B. A.; Dubey, M. K.; Subramanian, R.; Sedlacek, A. J.; Kelley, P.; Luke, W. T.; Jobson, B. T.; Zaveri, R. A.

2011-12-01

Predictions of aerosol radiative forcing require process level optical property models that are built on precise and accurate field observations. Evolution of aerosol optical properties for urban influenced carbonaceous aerosol undergoing transport and mixing with rural air masses was a focal point of the DOE Carbonaceous Aerosol and Radiative Effects (CARES) campaign near Sacramento, CA in summer 2010. Urban aerosol was transported from Sacramento, CA (T0) to the foothills of the Sierra Nevada Mountains to a rural site located near Cool, CA (T1). Aerosol absorption and scattering coefficients were measured at the T0 and T1 sites using integrated photoacoustic acoustic/nephelometer instruments (PASS-3 and PASS-UV) at 781, 532, 405, and 375 nm. Single particle soot photometry (SP2) instrumentation was used to monitor black carbon (BC) mass at both sites. Combining data from these sensors allows estimate of the wavelength-dependent mass absorption coefficient (MAC(λ)) and partitioning of MAC(λ) into contributions from the BC core and from enhancements from coating of BC cores. MAC(λ) measured in this way is free of artifacts associated with filter-based aerosol absorption measurements and takes advantage of the single particle sensitivity of the SP2 instrument, allowing observation of MAC(λ) on 10 minute and faster time scales. Coating was observed to enhance MAC(λ) by 20 - 30 % and different wavelength dependence for MAC(λ) was observed for urban and biomass burning aerosol. Further, T0 - T1 evolution of MAC(λ) was correlated with separately measured NO/NOy ratios and CO/CO2 ratios to understand the effects of aging & transport on MAC(λ) and the implications of aerosol processing that links air quality to radiative forcing on a regional scale. Aircraft observations made from the Gulfstream-1 during CARES are also analyzed to enhance process level understanding of the optical properties of fresh and aged carbonaceous aerosol in the urban-rural interface.

Deposition of amorphous carbon thin films by aerosol-assisted CVD method

NASA Astrophysics Data System (ADS)

Fadzilah, A. N.; Dayana, K.; Rusop, M.

2018-05-01

This paper reports on the deposition of amorphous carbon (a-C) by Aerosol-assisted Chemical Vapor Deposition (AACVD) using natural source of camphor oil as the precursor material. 4 samples were deposited at 4 different deposition flow rate from 15 sccm to 20 sccm, with 5 sccm interval for each sample. The analysis includes the electrical, optical and structural analysis of the data. The a-C structure which came from the manipulation of synthesis parameter was characterized by the solar simulator system, UV-VIS-NIR, Raman spectroscope and AFM. The properties of a-C are highly dependent on the deposition techniques and deposition parameters; hence the influences of gas flow rate were studied.

Aerosol optical properties in ultraviolet ranges and respiratory diseases in Thailand

NASA Astrophysics Data System (ADS)

Kumharn, Wilawan; Hanprasert, Kasarin

2016-10-01

This study investigated the values of Angstrom parameters (α,β) in ultraviolet (UV) ranges by using AERONET Aerosol Optical Depth (AOD) data. A second-order polynomial was applied to the AERONET data in order to extrapolate to 320 nm from 2003 to 2013 at seven sites in Thailand. The α,β were derived by applying the Volz Method (VM) and Linear Method (LM) at 320-380 nm at seven monitoring sites in Thailand. Aerosol particles were categorized in both coarse and fine modes, depending on regions. Aerosol loadings were related to dry weather, forest fires, sea salt and most importantly, biomass burning in the North, and South of Thailand. Aerosol particles in the Central region contain coarse and fine modes, mainly emitted from vehicles. The β values obtained were associated with turbid and very turbid skies in Northern and Central regions except Bangkok, while β results are associated with clean skies in South. Higher values of the β at all sites were found in the winter and summer compared with the rainy season, in contrast to South where the highest AOD was observed in June. The β values were likely to increase during 2003-2013. These values correlate with worsening health situations as evident from increasing respiratory diseases reported.

Study on Dicarboxylic Acids in Aerosol Samples with Capillary Electrophoresis

PubMed Central

Adler, Heidi; Sirén, Heli

2014-01-01

The research was performed to study the simultaneous detection of a homologous series of α, ω-dicarboxylic acids (C2–C10), oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, and sebacic acids, with capillary electrophoresis using indirect UV detection. Good separation efficiency in 2,6-pyridinedicarboxylic acid as background electrolyte modified with myristyl trimethyl ammonium bromide was obtained. The dicarboxylic acids were ionised and separated within five minutes. For the study, authentic samples were collected onto dry cellulose membrane filters of a cascade impactor (12 stages) from outdoor spring aerosols in an urban area. Hot water and ultrasonication extraction methods were used to isolate the acids from membrane filters. Due to the low concentrations of acids in the aerosols, the extracts were concentrated with solid-phase extraction (SPE) before determination. The enrichment of the carboxylic acids was between 86 and 134% with sample pretreatment followed by 100-time increase by preparation of the sample to 50 μL. Inaccuracy was optimised for all the sample processing steps. The aerosols contained dicarboxylic acids C2–C10. Then, mostly they contained C2, C5, and C10. Only one sample contained succinic acid. In the study, the concentrations of the acids in aerosols were lower than 10 ng/m3. PMID:24729915

Chemical evolution of Titan’s aerosol analogues under VUV irradiation

NASA Astrophysics Data System (ADS)

Carrasco, Nathalie; Gavilan, Lisseth; Tigrine, Sarah; Vettier, Ludovic; Nahon, Laurent; Pernot, Pascal

2017-10-01

Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan’s ionosphere [1].After production in the ionosphere, Titan’s aerosols evolve through microphysics during their sedimentation down to Titan’s surface [2]. Starting with a few nanomers size in the upper atmosphere, they reach a fractal structure of a few hundreds nanometers close to the surface [3]. During sedimentation, aerosols are also submitted to solar irradiation. As laboratory analogs of Titan’s atmospheric aerosols (tholins) show a strong UV absorption [4], we suspect that VUV irradiation could also induce a chemical evolution of Titan’s aerosols during their descent in Titan’s atmosphere.The aim of this work ist to simulate the irradiation process occuring on the aerosols in Titan’s atmosphere and to address whether this irradiation impacts the chemical composition of the organic solids. First aerosol analogues were produced in a N2-CH4 plasma discharge as thin organic films of a few hundreds of nanometers thick [5]. Then those were irradiated at Lyman-α wavelength, the strongest VUV line in the solar spectrum, with a high photon flux on a synchrotron VUV beamline. We will present and discuss the significant chemical evolutions observed on the analogues after VUV irradiation by mid-IR absorption spectroscopy.[1] Waite et al. (2009) Science , 316, p. 870[2] Lavvas et al. (2011) Astrophysical Journal, 728:80[3] Tomasko et al. (2008) Planetary and Space Science, 56, p. 669[4] Mahjoub et al. (2012) Icarus 221, P. 670[5] Carrasco et al. (2016) Planetary and Space Science, 128, p. 52

Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiumeng; Lin, Peng; Laskin, Alexander

2016-10-14

The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the lightmore » absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

Lidar Remote Sensing for Industry and Environment Monitoring

NASA Technical Reports Server (NTRS)

Singh, Upendra N. (Editor); Itabe, Toshikazu (Editor); Sugimoto, Nobuo (Editor)

2000-01-01

Contents include the following: 1. Keynote paper: Overview of lidar technology for industrial and environmental monitoring in Japan. 2. lidar technology I: NASA's future active remote sensing mission for earth science. Geometrical detector consideration s in laser sensing application (invited paper). 3. Lidar technology II: High-power femtosecond light strings as novel atmospheric probes (invited paper). Design of a compact high-sensitivity aerosol profiling lidar. 4. Lasers for lidars: High-energy 2 microns laser for multiple lidar applications. New submount requirement of conductively cooled laser diodes for lidar applications. 5. Tropospheric aerosols and clouds I: Lidar monitoring of clouds and aerosols at the facility for atmospheric remote sensing (invited paper). Measurement of asian dust by using multiwavelength lidar. Global monitoring of clouds and aerosols using a network of micropulse lidar systems. 6. Troposphere aerosols and clouds II: Scanning lidar measurements of marine aerosol fields at a coastal site in Hawaii. 7. Tropospheric aerosols and clouds III: Formation of ice cloud from asian dust particles in the upper troposphere. Atmospheric boundary layer observation by ground-based lidar at KMITL, Thailand (13 deg N, 100 deg. E). 8. Boundary layer, urban pollution: Studies of the spatial correlation between urban aerosols and local traffic congestion using a slant angle scanning on the research vessel Mirai. 9. Middle atmosphere: Lidar-observed arctic PSC's over Svalbard (invited paper). Sodium temperature lidar measurements of the mesopause region over Syowa Station. 10. Differential absorption lidar (dIAL) and DOAS: Airborne UV DIAL measurements of ozone and aerosols (invited paper). Measurement of water vapor, surface ozone, and ethylene using differential absorption lidar. 12. Space lidar I: Lightweight lidar telescopes for space applications (invited paper). Coherent lidar development for Doppler wind measurement from the International Space Station. 13. Space lidar II: Using coherent Doppler lidar to estimate river discharge. 14. Poster session: Lidar technology, optics for lidar. Laser for lidar. Middle atmosphere observations. Tropospheric observations (aerosols, clouds). Boundary layer, urban pollution. Differential absorption lidar. Doppler lidar. and Space lidar.

Effects of ceiling-mounted HEPA-UV air filters on airborne bacteria concentrations in an indoor therapy pool building.

PubMed

Kujundzic, Elmira; Zander, David A; Hernandez, Mark; Angenent, Largus T; Henderson, David E; Miller, Shelly L

2005-02-01

The purpose of this study was to assess the effectiveness of a new generation of high-volume, ceiling-mounted high-efficiency particulate air (HEPA)-ultraviolet (UV) air filters (HUVAFs) for their ability to remove or inactivate bacterial aerosol. In an environmentally controlled full-scale laboratory chamber (87 m3), and an indoor therapy pool building, the mitigation ability of air filters was assessed by comparing concentrations of total bacteria, culturable bacteria, and airborne endotoxin with and without the air filters operating under otherwise similar conditions. Controlled chamber tests with pure cultures of aerosolized Mycobacterium parafortuitum cells showed that the HUVAF unit tested provided an equivalent air-exchange rate of 11 hr(-1). Using this equivalent air-exchange rate as a design basis, three HUVAFs were installed in an indoor therapy pool building for bioaerosol mitigation, and their effectiveness was studied over a 2-year period. The HUVAFs reduced concentrations of culturable bacteria by 69 and 80% during monitoring periods executed in respective years. The HUVAFs reduced concentrations of total bacteria by 12 and 76% during the same monitoring period, respectively. Airborne endotoxin concentrations were not affected by the HUVAF operation.

Quantitative assessment of drivers of recent global temperature variability: an information theoretic approach

NASA Astrophysics Data System (ADS)

Bhaskar, Ankush; Ramesh, Durbha Sai; Vichare, Geeta; Koganti, Triven; Gurubaran, S.

2017-12-01

Identification and quantification of possible drivers of recent global temperature variability remains a challenging task. This important issue is addressed adopting a non-parametric information theory technique, the Transfer Entropy and its normalized variant. It distinctly quantifies actual information exchanged along with the directional flow of information between any two variables with no bearing on their common history or inputs, unlike correlation, mutual information etc. Measurements of greenhouse gases: CO2, CH4 and N2O; volcanic aerosols; solar activity: UV radiation, total solar irradiance ( TSI) and cosmic ray flux ( CR); El Niño Southern Oscillation ( ENSO) and Global Mean Temperature Anomaly ( GMTA) made during 1984-2005 are utilized to distinguish driving and responding signals of global temperature variability. Estimates of their relative contributions reveal that CO2 ({˜ } 24 %), CH4 ({˜ } 19 %) and volcanic aerosols ({˜ }23 %) are the primary contributors to the observed variations in GMTA. While, UV ({˜ } 9 %) and ENSO ({˜ } 12 %) act as secondary drivers of variations in the GMTA, the remaining play a marginal role in the observed recent global temperature variability. Interestingly, ENSO and GMTA mutually drive each other at varied time lags. This study assists future modelling efforts in climate science.

Broadband optical properties of biomass-burning aerosol and identification of brown carbon chromophores: OPTICAL AND CHEMICAL PROPERTIES OF BROWN CARBON AEROSOLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bluvshtein, Nir; Lin, Peng; Flores, J. Michel

The radiative effects of biomass burning aerosols on regional and global scale is substantial. Accurate modeling of the radiative effects of smoke aerosols require wavelength-dependent measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue, we used a recently developed approach to retrieve the time- and spectral-dependent optical properties of ambient biomass burning aerosols between 300 and 650 nm wavelength during a regional bonfire festival in Israel. During the biomass burning event, the overall absorption at 400 nm increased by about two orders ofmore » magnitude, changing the size-weighted single scattering albedo from a background level of 0.95 to 0.7. Based on the new retrieval method, we provide parameterizations of the wavelength-dependent effective complex refractive index from 350 to 650 nm for freshly emitted and aged biomass burning aerosols. In addition, PM2.5 filter samples were collected for detailed off-line chemical analysis of the water soluble organics that contribute to light absorption. Nitrophenols were identified as the main organic species responsible for the increased absorption at 400-500 nm. These include species such as 4- nitrocatechol, 4-nitrophenol, nitro-syringol and nitro-guaiacol; oxidation-nitration products of methoxyphenols, known products of lignin pyrolysis. Our findings emphasize the importance of both primary and secondary organic aerosol from biomass burning in absorption of solar radiation and in effective radiative forcing.« less

Ozone and Aerosol Retrieval from Backscattered Ultraviolet Radiation

NASA Technical Reports Server (NTRS)

Bhartia, Pawan K.

2004-01-01

In this presentation we will discuss the techniques to estimate total column ozone and aerosol absorption optical depth from the measurements of backscattered ultraviolet (buv) radiation. The total ozone algorithm has been used to create a unique record of the ozone layer, spanning more than 3 decades, from a series of instruments (BUV, SBUV, TOMS, SBUV/2) flown on NASA, NOAA, Japanese and Russian satellites. We will discuss how this algorithm can be considered a generalization of the well-known Dobson/Brewer technique that has been used to process data from ground-based instruments for many decades, and how it differs from the DOAS techniques that have been used to estimate vertical column densities of a host of trace gases from data collected by GOME and SCIAMACHY instruments. The BUV aerosol algorithm is most suitable for the detection of UV absorbing aerosols (smoke, desert dust, volcanic ash) and is the only technique that can detect aerosols embedded in clouds. This algorithm has been used to create a quarter century record of aerosol absorption optical depth using the BUV data collected by a series of TOMS instruments. We will also discuss how the data from the OM1 instrument launched on July 15,2004 will be combined with data from MODIS and CALIPSO lidar data to enhance the accuracy and information content of satellite-derived aerosol measurements. The OM1 and MODIS instruments are currently flying on EOS Aura and EOS Aqua satellites respectively, part of a constellation of satellites called the "A-train". The CALIPSO satellite is expected to join this constellation in mid 2005.

A new paradigm for constraining PM2.5 speciation by combining multiangular and polarimetric remote sensing with chemical transport model information

NASA Astrophysics Data System (ADS)

Kalashnikova, O.; Xu, F.; Ge, C.; Wang, J.; Garay, M. J.; Diner, D. J.

2014-12-01

Exposure to ambient particulate matter (PM) has been consistently linked to cardiovascular and respiratory health effects. Although PM is currently monitored by a network of surface stations, these are too sparsely distributed to provide the level of spatial detail needed to link different aerosol species to given health effects, and expansion to denser coverage is impractical and cost prohibitive. We present a methodology for combining Chemical Transport Model (CTM) aerosol type information and multiangular spectropolarimetric data to establish the signature of specific aerosol types in top-of-atmosphere measurements, and relate it to speciated surface PM2.5 loadings. In particular, we employ the WRF-Chem model run at the University of Nebraska, and remote sensing data from the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) to explore the feasibility of this approach. We demonstrate that the CTM does well in predicting the types of aerosols present at a given location and time, however large uncertainties currently exist in CTM estimates of the concentration of the various aerosol species (e.g., black carbon, sulfate, dust, etc.) leading to large uncertainties to model-derived speciated PM 2.5. In order to constrain CTM aerosol surface concentrations we use AirMSPI UV-VIS-NIR observations of intensity, and blue, red, and NIR observations of the Q and U Stokes parameters. We select specific scenes observed by AirMSPI and use WRF-Chem to generate an initial distribution of aerosol composition. The relevant optical properties for each aerosol species are used to calculate aerosol light scattering information. This is then used in a vector (polarized) 1-D radiative transfer model to determine at-instrument Stokes parameters for the specific AirMSPI viewing geometries. As a first step, a match is sought between the CTM-predicted radiances and the AirMSPI observations. Then, the total aerosol optical depth and fractions of various aerosol species are modified via optimization to produce a better match to the observations, and converted to PM2.5 speciated loadings using CTM aerosol vertical profiles. Finally, the results are compared to available ground-based and in situ data to validate this approach.

Integrated photocatalytic filtration array for indoor air quality control.

PubMed

Denny, Frans; Permana, Eric; Scott, Jason; Wang, Jing; Pui, David Y H; Amal, Rose

2010-07-15

Photocatalytic and filtration technologies were integrated to develop a hybrid system capable of removing and oxidizing organic pollutants from an air stream. A fluidized bed aerosol generator (FBAG) was adapted to prepare TiO(2)-loaded ventilation filters for the photodegradation of gas phase ethanol. Compared to a manually loaded filter, the ethanol photodegradation rate constant for the FBAG coated filter increased by 361%. Additionally, the presence of the photogenerated intermediate product, acetaldehyde, was reduced and the time for mineralization to CO(2) was accelerated. These improvements were attributed to the FBAG system providing a more uniform distribution of TiO(2) particles across the filter surface leading to greater accessibility by the UV light. A dual-UV-lamp system, as opposed to a single-lamp system, enhanced photocatalytic filter performance demonstrating the importance of high light irradiance and light distribution across the filter surface. Substituting the blacklight blue lamps with a UV-light-emitting-diode (UV-LED) array led to further improvement as well as suppressed the electrical energy per order (EE/O) by a factor of 6. These improvements derived from the more uniform distribution of light irradiance as well as the higher efficiency of UV-LEDs in converting electrical energy to photons.

Determination of UV-visible-NIR absorption coefficient of graphite bulk using direct and indirect methods

NASA Astrophysics Data System (ADS)

Smausz, T.; Kondász, B.; Gera, T.; Ajtai, T.; Utry, N.; Pintér, M.; Kiss-Albert, G.; Budai, J.; Bozóki, Z.; Szabó, G.; Hopp, B.

2017-10-01

Absorption coefficient of graphite bulk pressed from 1 to 5 μm-sized crystalline grains was measured in UV-Vis-NIR range with three different methods: (i) determination of pulsed laser ablation rate as the function of laser fluence for different wavelengths (248, 337, 532, and 1064 nm, respectively); (ii) production of aerosol particles by UV laser ablation of the bulk graphite in inert atmosphere and determination of the mass-specific absorption coefficient with a four-wavelength (266, 355, 532, and 1064 nm, respectively) photoacoustic spectrometer, and (iii) spectroscopic ellipsometry in 250-1000 nm range. Taking into account the wide range of the absorption coefficients of different carbon structures, an overall relatively good agreement was observed for the three methods. The ellipsometric results fit well with the ablation rate measurement, and the data obtained with photoacoustic method are also similar in the UV and NIR region; however, the values were somewhat higher in visible and near-UV range. Taking into account the limitations of the methods, they can be promising candidates for the determination of absorption coefficient when the samples are strongly scattering and there is no possibility to perform transmissivity measurements.

Long-Term Variability of UV Irradiance in the Moscow Region according to Measurement and Modeling Data

NASA Astrophysics Data System (ADS)

Chubarova, N. E.; Pastukhova, A. S.; Galin, V. Ya.; Smyshlyaev, S. P.

2018-03-01

We have found distinct long-period changes in erythemal UV radiation ( Q er) characterized by a pronounced decrease at the end of the 1970s and a statistically significant positive trend of more than 5%/10 years since 1979 over the territory of the Moscow region according to the measurements and reconstruction model. The positive Q er trend is shown to be associated mainly with a decrease in the effective cloud amount and total ozone content (TOC). Due to these variations, UV resources have significantly changed in spring for the population with the most vulnerable skin type I, which means a transition from the UV optimum to UV moderate excess conditions. The simulation experiments using the INM-RSHU chemistry climate model (CCM) for several scenarios with and without anthropogenic factors have revealed that the variations in the anthropogenic emissions of halogens have the most significant impact on the variability of TOC and Q er. Among natural factors, noticeable effects are observed due to volcanic aerosol. The calculations of the cloud transmittance of Q er are generally consistent with the measurements; however, they do not reproduce the observed value of the positive trend.

Broadband optical properties of biomass-burning aerosol and identification of brown carbon chromophores

NASA Astrophysics Data System (ADS)

Bluvshtein, Nir; Lin, Peng; Flores, J. Michel; Segev, Lior; Mazar, Yinon; Tas, Eran; Snider, Graydon; Weagle, Crystal; Brown, Steven S.; Laskin, Alexander; Rudich, Yinon

2017-05-01

The radiative effects of biomass-burning aerosols on regional and global scales can be substantial. Accurate modeling of the radiative effects of smoke aerosols requires wavelength-dependent measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue, we used a recently developed approach to retrieve the time- and spectral-dependent optical properties of ambient biomass-burning aerosols from 300 to 650 nm wavelengths during a regional nighttime bonfire festival in Israel. During the biomass burning event, the overall absorption at 400 nm increased by about 2 orders of magnitude, changing the single scattering albedo from a background level of 0.95 to 0.7. Based on the new retrieval method, we provide parameterizations of the wavelength-dependent effective complex refractive index from 350 to 650 nm for freshly emitted and slightly aged biomass-burning aerosols. In addition, PM2.5 filter samples were collected for detailed offline chemical analysis of the water-soluble organics that contribute to light absorption. Nitroaromatics were identified as major organic species responsible for the increased absorption at 400 to 500 nm. Typical chromophores include 4-nitrocatechol, 4-nitrophenol, nitrosyringol, and nitroguaiacol; oxidation-nitration products of methoxyphenols; and known products of lignin pyrolysis. Our findings emphasize the importance of both primary and secondary organic aerosols from biomass burning in absorption of solar radiation and in effective radiative forcing.

Imaginary refractive index and other microphysical properties of volcanic ash, Sarahan dust, and other mineral aerosols

NASA Astrophysics Data System (ADS)

Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Artaxo, P.; Todd, M.; Ben Ami, Y.; Dolgos, G.; Espinosa, R.

2013-12-01

Aerosol properties are essential to support remote sensing measurements, atmospheric circulation and climate models. This research aims to improve the understanding of the optical and microphysical properties of different types of aerosols particles. Samples of volcanic ash, Saharan dust and other mineral aerosols particles were analyzed by different techniques. Ground samples were sieved down to 45um, de-agglomerated and resuspended in the laboratory using a Fluidized Bed Aerosol Generator (FBAG). Particles were collected on Nuclepore filters into PM10, PM2.5, or PM1.0. and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index from the UV to the short wave infrared (SWIR) wavelength was derived empirically from the measurements of the spectral mass absorption coefficient, size distribution and density of the material. Some selected samples were also analyzed with the Polarized Imaging Nephelometer (PI-Neph) instrument for the characterization of the aerosol polarized phase function. This work compares results of the spectral refractive index of different materials obtained by our methodology with those available in the literature. In some cases there are significant differences both in magnitude and spectral dependence of the imaginary refractive index. These differences are evaluated and discussed in this work.

Stratospheric minor species vertical distributions during polar winter by balloon borne UV-Vis spectrometry

NASA Technical Reports Server (NTRS)

Pommereau, J. P.; Piquard, J.

1994-01-01

A light, relatively cheap and easy to operate balloonborne UV-visible spectrometer was designed for investigating ozone photochemistry in the Arctic winter. The instrument was flown 11 times during the European Arctic Stratospheric Ozone Experiment (EASOE) in winter 1991-92 in Northern Scandinavia. The first simultaneous measurements of vertical distributions of aerosols, PSC's, O3, NO2 and OClO inside the vortex during flight no. 6 on 16 January, in cold conditions are reported, which show that nitrogen oxides were almost absent (lower than 100 ppt) in the stratosphere below 22 km, while a layer of relatively large OClO concentration (15 ppt) was present at the altitude of the minimum temperature.

Photochemical Formation of Aerosol in Planetary Atmospheres: Photon and Water Mediated Chemistry of SO_2

NASA Astrophysics Data System (ADS)

Kroll, Jay A.; Donaldson, D. J.; Vaida, Veronica

2016-06-01

Sulfur compounds have been observed in a number of planetary atmospheres throughout our solar system. Our current understanding of sulfur chemistry explains much of what we observe in Earth's atmosphere. However, several discrepancies between modeling and observations of the Venusian atmosphere show there are still problems in our fundamental understanding of sulfur chemistry. This is of particular concern due to the important role sulfur compounds play in the formation of aerosols, which have a direct impact on planetary climates, including Earth's. We investigate the role of water complexes in the hydration of sulfur oxides and dehydration of sulfur acids and will present spectroscopic studies to document such effects. I will present recent work investigating mixtures of SO_2 and water that generate large quantities of aerosol when irradiated with solar UV light, even in the absence of traditional OH chemistry. I will discuss a proposed mechanism for the formation of sulfurous acid (H_2SO_3) and present recent experimental work that supports this proposed mechanism. Additionally, the implications that photon-induced hydration of SO_2 has for aerosol formation in the atmosphere of earth as well as other planetary atmospheres will be discussed.

Preventing Airborne Disease Transmission: Review of Methods for Ventilation Design in Health Care Facilities

PubMed Central

Aliabadi, Amir A.; Rogak, Steven N.; Bartlett, Karen H.; Green, Sheldon I.

2011-01-01

Health care facility ventilation design greatly affects disease transmission by aerosols. The desire to control infection in hospitals and at the same time to reduce their carbon footprint motivates the use of unconventional solutions for building design and associated control measures. This paper considers indoor sources and types of infectious aerosols, and pathogen viability and infectivity behaviors in response to environmental conditions. Aerosol dispersion, heat and mass transfer, deposition in the respiratory tract, and infection mechanisms are discussed, with an emphasis on experimental and modeling approaches. Key building design parameters are described that include types of ventilation systems (mixing, displacement, natural and hybrid), air exchange rate, temperature and relative humidity, air flow distribution structure, occupancy, engineered disinfection of air (filtration and UV radiation), and architectural programming (source and activity management) for health care facilities. The paper describes major findings and suggests future research needs in methods for ventilation design of health care facilities to prevent airborne infection risk. PMID:22162813

Using CATS Near-Real-time Lidar Observations to Monitor and Constrain Volcanic Sulfur Dioxide (SO2) Forecasts

NASA Technical Reports Server (NTRS)

Hughes, E. J.; Yorks, J.; Krotkov, N. A.; da Silva, A. M.; Mcgill, M.

2016-01-01

An eruption of Italian volcano Mount Etna on 3 December 2015 produced fast-moving sulfur dioxide (SO2) and sulfate aerosol clouds that traveled across Asia and the Pacific Ocean, reaching North America in just 5 days. The Ozone Profiler and Mapping Suite's Nadir Mapping UV spectrometer aboard the U.S. National Polar-orbiting Partnership satellite observed the horizontal transport of the SO2 cloud. Vertical profiles of the colocated volcanic sulfate aerosols were observed between 11.5 and 13.5 km by the new Cloud Aerosol Transport System (CATS) space-based lidar aboard the International Space Station. Backward trajectory analysis estimates the SO2 cloud altitude at 7-12 km. Eulerian model simulations of the SO2 cloud constrained by CATS measurements produced more accurate dispersion patterns compared to those initialized with the back trajectory height estimate. The near-real-time data processing capabilities of CATS are unique, and this work demonstrates the use of these observations to monitor and model volcanic clouds.

Using CATS Near-Real-Time Lidar Observations to Monitor and Constrain Volcanic Sulfur Dioxide (SO2) Forecasts

NASA Technical Reports Server (NTRS)

Hughes, E. J.; Yorks, J.; Krotkov, N. A.; Da Silva, A. M.; McGill, M.

2016-01-01

An eruption of Italian volcano Mount Etna on 3 December 2015 produced fast-moving sulfur dioxide (SO2) and sulfate aerosol clouds that traveled across Asia and the Pacific Ocean, reaching North America in just 5days. The Ozone Profiler and Mapping Suite's Nadir Mapping UV spectrometer aboard the U.S. National Polar-orbiting Partnership satellite observed the horizontal transport of the SO2 cloud. Vertical profiles of the colocated volcanic sulfate aerosols were observed between 11.5 and 13.5 km by the new Cloud Aerosol Transport System (CATS) space-based lidar aboard the International Space Station. Backward trajectory analysis estimates the SO2 cloud altitude at 7-12 km. Eulerian model simulations of the SO2 cloud constrained by CATS measurements produced more accurate dispersion patterns compared to those initialized with the back trajectory height estimate. The near-real-time data processing capabilities of CATS are unique, and this work demonstrates the use of these observations to monitor and model volcanic clouds.

Actinic Flux Calculations: A Model Sensitivity Study

NASA Technical Reports Server (NTRS)

Krotkov, Nickolay A.; Flittner, D.; Ahmad, Z.; Herman, J. R.; Einaudi, Franco (Technical Monitor)

2000-01-01

calculate direct and diffuse surface irradiance and actinic flux (downwelling (2p) and total (4p)) for the reference model. Sensitivity analysis has shown that the accuracy of the radiative transfer flux calculations for a unit ETS (i.e. atmospheric transmittance) together with a numerical interpolation technique for the constituents' vertical profiles is better than 1% for SZA less than 70(sub o) and wavelengths longer than 310 nm. The differences increase for shorter wavelengths and larger SZA, due to the differences in pseudo-spherical correction techniques and vertical discretetization among the codes. Our sensitivity study includes variation of ozone cross-sections, ETS spectra and the effects of wavelength shifts between vacuum and air scales. We also investigate the effects of aerosols on the spectral flux components in the UV and visible spectral regions. The "aerosol correction factors" (ACFs) were calculated at discrete wavelengths and different SZAs for each flux component (direct, diffuse, reflected) and prescribed IPMMI aerosol parameters. Finally, the sensitivity study was extended to calculation of selected photolysis rates coefficients.

The versatility of limb scattered sunlight measurements

NASA Astrophysics Data System (ADS)

Bourassa, A. E.; Degenstein, D. A.; Sioris, C.; Rieger, L. A.; Zawada, D.

2017-12-01

Vertically resolved measurements of limb scattered sunlight spectra in the UV-Vis-NIR spectral range have been made from several satellite instruments in low earth orbit for many years, and there has been much success in using these measurements for retrievals of trace gas and aerosol from the upper troposphere to the mesosphere. Due in a large part to improvements in radiative transfer modelling, the versatility of the limb scatter measurement has continued to grow over the last several years. Using OSIRIS and OMPS instruments as primary examples, this talk will review the current capability of limb scatter measurements, and highlight recent results on ozone variability and trends in the UTLS, the continuation of the aerosol extinction record, NO2 distributions in the upper troposphere, and a new tomographic retrieval of ozone from the OMPS measurements. The future of limb scatter observations will also be discussed, including the development of two new Canadian suborbital instrument concepts that are targeted at high spatial resolution UTLS water vapor and cloud/aerosol measurements.

Preventing airborne disease transmission: review of methods for ventilation design in health care facilities.

PubMed

Aliabadi, Amir A; Rogak, Steven N; Bartlett, Karen H; Green, Sheldon I

2011-01-01

Health care facility ventilation design greatly affects disease transmission by aerosols. The desire to control infection in hospitals and at the same time to reduce their carbon footprint motivates the use of unconventional solutions for building design and associated control measures. This paper considers indoor sources and types of infectious aerosols, and pathogen viability and infectivity behaviors in response to environmental conditions. Aerosol dispersion, heat and mass transfer, deposition in the respiratory tract, and infection mechanisms are discussed, with an emphasis on experimental and modeling approaches. Key building design parameters are described that include types of ventilation systems (mixing, displacement, natural and hybrid), air exchange rate, temperature and relative humidity, air flow distribution structure, occupancy, engineered disinfection of air (filtration and UV radiation), and architectural programming (source and activity management) for health care facilities. The paper describes major findings and suggests future research needs in methods for ventilation design of health care facilities to prevent airborne infection risk.

Does the Madden-Julian Oscillation influence aerosol variability?

NASA Astrophysics Data System (ADS)

Tian, Baijun; Waliser, Duane E.; Kahn, Ralph A.; Li, Qinbin; Yung, Yuk L.; Tyranowski, Tomasz; Geogdzhayev, Igor V.; Mishchenko, Michael I.; Torres, Omar; Smirnov, Alexander

2008-06-01

We investigate the modulation of aerosols by the Madden-Julian Oscillation (MJO) using multiple, global satellite aerosol products: aerosol index (AI) from the Total Ozone Mapping Spectrometer (TOMS) on Nimbus-7, and aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Advanced Very High Resolution Radiometer (AVHRR) on NOAA satellites. A composite MJO analysis indicates that large variations in the TOMS AI and MODIS/AVHRR AOT are found over the equatorial Indian and western Pacific Oceans where MJO convection is active, as well as the tropical Africa and Atlantic Ocean where MJO convection is weak but the background aerosol level is high. A strong inverse linear relationship between the TOMS AI and rainfall anomalies, but a weaker, less coherent positive correlation between the MODIS/AVHRR AOT and rainfall anomalies, were found. The MODIS/AVHRR pattern is consistent with ground-based Aerosol Robotic Network data. These results indicate that the MJO and its associated cloudiness, rainfall, and circulation variability systematically influence the variability in remote sensing aerosol retrieval results. Several physical and retrieval algorithmic factors that may contribute to the observed aerosol-rainfall relationships are discussed. Preliminary analysis indicates that cloud contamination in the aerosol retrievals is likely to be a major contributor to the observed relationships, although we cannot exclude possible contributions from other physical mechanisms. Future research is needed to fully understand these complex aerosol-rainfall relationships.

Satellite global monitoring of environmental quality

NASA Technical Reports Server (NTRS)

Schiffer, R. A.

1975-01-01

The missions of two NASA satellites for the monitoring of environmental quality are described: Nimbus G, the Air Pollution and Oceanographic Observing Satellite, and the Applications Explorer Mission (AEM) satellite to be used in the Stratospheric Aerosol and Gas Experiment (SAGE). The scientific payload of Nimbus G is described in detail with a discussion of limb infrared monitoring of the stratosphere, the stratospheric and mesospheric sounder, stratospheric aerosol measurement, the solar and backscatter UV spectrometer for ozone mapping, the earth radiation budget experiment, the scanning multichannel microwave radiometer, the coastal zone color scanner and the temperature-humidity infrared radiometer. A brief description is given of the SAGE program and future NASA plans relating to the global monitoring of environmental quality are outlined.

Cumulus cloud venting of mixed layer ozone

NASA Technical Reports Server (NTRS)

Ching, J. K. S.; Shipley, S. T.; Browell, E. V.; Brewer, D. A.

1985-01-01

Observations are presented which substantiate the hypothesis that significant vertical exchange of ozone and aerosols occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments utilized the airborne Ultra-Violet Differential Absorption Lidar (UV-DIAL) system. This system provides simultaneous range resolved ozone concentration and aerosol backscatter profiles with high spatial resolution. Evening transects were obtained in the downwind area where the air mass had been advected. Space-height analyses for the evening flight show the cloud debris as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approximately the value of the concentration difference between the mixed layer and free troposphere determined from independent vertical soundings made by another aircraft in the afternoon.

Long-term variations of the UV-B radiation over Central Europe since early 1960s, as revealed from the UV observations and reconstructed data

NASA Astrophysics Data System (ADS)

Krzyscin, J. W.

2003-04-01

A method of reconstruction of the UV variations for periods when UV-B measurements were not carried out is proposed. The reconstruction is based on observations of total (Sun+sky) radiation by a pyranometer, Dobson total ozone, sunshine duriation from the Campbel Stokes heliograph, and atmospheric column water content taken from NCEP/NOAA reanalysis. Modeled all-sky erythemaly weighted daily dose is calculated as a product of the cloud reduction factor (CRF) over UV range and clear-sky dose from a radiative transfer model. CRF over UV range is estimated from measured CRF for total solar radiation and the statistical dependence relating CRF over UV with that over whole solar spectrum. The measured daily UV doses and daily sum of total radiation taken at Belsk, Poland (52N, 21E) for the period 1976-2001 have been used to construct the regressions for various solar zenith angles. The time series of monthly means from the modeled daily UV doses follows the observed monthly means supporting the possibility of reconstruction of the UV time series for other periods. An inspection of the long-term stability of total radiation measurements is necessary to discuss trends in the reconstructed time series. We examine the data homogeneity analyzing the ratio of the observed to modeled total radiation for fully clear sky days that are selected from the daily values of sunshine duration measured by the Campbel-Stokes heliograph. Combining reconstructed and observed monthly means of the UV doses we found a positive trend in the UV radiation in the period 1980-1995 and almost constant UV level for other periods (early 60s up to 1980, and 1995-2001). The trend pattern suggests dominating role of the long-term total ozone forcing on the UV level with a small impact of the long-term changes in the cloud/aerosol properties.

A Novel Technique to Calculate UV Opacity at Gale Crater from MSL/REMS Measurements

NASA Astrophysics Data System (ADS)

Vicente-Retortillo, Álvaro; Martínez, Germán M.; Renno, Nilton O.; Lemmon, Mark T.; Mason, Emily L.; de la Torre-Juárez, Manuel

2016-04-01

The Rover Environmental Monitoring Station (REMS) on board the Mars Science Laboratory (MSL) mission carries a UV sensor that for the first time is measuring the solar radiation at the surface of Mars in six bands between 200 and 380 nm [1]. Here we present a novel methodology to calculate the atmospheric opacity by using the UV photodiode output currents measured by this sensor (TELRDR products) and ancillary (ADR) data. We estimate the diffuse and total radiation signals by analyzing the events in which the direct solar beam was temporarily blocked by the masthead or by the mast of the rover. Then we use a radiative transfer model with updated radiative properties of the Martian aerosols ([2], [3]) based on the Monte-Carlo method to retrieve the UV opacity from those measurements. Therefore, this methodology is not sensitive to the degradation of the sensor due to the deposition of dust on it. In addition, by using TELRDR and ADR data, inconsistencies in the processed reduced data (ENVRDR and MODRDR products, in units of W/m2) found when the solar zenith angle relative to REMS rover frame is above 30° are avoided. In order to validate our technique, we compare the UV opacities with those derived from Mastcam observations at 880 nm. We find that both opacities show a good agreement and follow a similar seasonal trend, with the UV opacity showing values generally lower than at 880 nm. The difference between both opacities varies over the year, with the minimum difference occurring during the first half of the winter, when both opacities show their annual lowest values. The temporal variation of this difference may be used to analyze changes in the dust size distribution. [1] Gómez-Elvira, J., Armiens, C., Castañer, L., Domínguez, M., Genzer, M. et al. REMS: the environmental sensor suite for the Mars Science Laboratory rover. Space Sci. Rev., 170 (1-4), 583-640, 2012. [2] Vicente-Retortillo, A., Valero, F., Vázquez, L. and Martínez, G. M. A model to calculate solar radiation fluxes on the Martian surface. J. Space Weather Space Clim., 5, A33, 2015. [3] Wolff, M. J., Clancy, R. T., Goguen, J. D., Malin, M. C., and Cantor, B. A. Ultraviolet dust aerosol properties as observed by MARCI. Icarus, 208 (1), 143-155, 2010.

Determination of the UV solar risk in Argentina with high-resolution maps calculated using TOMS ozone climatology

NASA Astrophysics Data System (ADS)

Piacentini, Rubén D.; Cede, Alexander; Luccini, Eduardo; Stengel, Fernando

2004-01-01

The connection between ultraviolet (UV) radiation and various skin diseases is well known. In this work, we present the computer program "UVARG", developed in order to prevent the risk of getting sunburn for persons exposed to solar UV radiation in Argentina, a country that extends from low (tropical) to high southern hemisphere latitudes. The software calculates the so-called "erythemal irradiance", i.e., the spectral irradiance weighted by the McKinlay and Diffey action spectrum for erythema and integrated in wavelength. The erythemal irradiance depends mainly on the following geophysical parameters: solar elevation, total ozone column, surface altitude, surface albedo, total aerosol optical depth and Sun-Earth distance. Minor corrections are due to the variability in the vertical ozone, aerosol, pressure, humidity and temperature profiles and the extraterrestrial spectral solar UV irradiance. Key parameter in the software is a total ozone column climatology incorporating monthly averages, standard deviations and tendencies for the particular geographical situation of Argentina that was obtained from TOMS/NASA satellite data from 1978 to 2000. Different skin types are considered in order to determine the sunburn risk at any time of the day and any day of the year, with and without sunscreen protection. We present examples of the software for three different regions: the high altitude tropical Puna of Atacama desert in the North-West, Tierra del Fuego in the South when the ozone hole event overpasses and low summertime ozone conditions over Buenos Aires, the largest populated city in the country. In particular, we analyzed the maximum time for persons having different skin types during representative days of the year (southern hemisphere equinoxes and solstices). This work was made possible by the collaboration between the Argentine Skin Cancer Foundation, the Institute of Physics Rosario (CONICET-National University of Rosario, Argentina) and the Institute of Medical Physics, University of Innsbruck, Austria. With the teamwork of physicians and physicists, a scientifically reliable and easy-to-handle tool was developed to predict the risk of solar exposure in Argentina. It can be used by dermatologists as well as health authorities and educators in order to prevent health problems induced by solar UV radiation.

Real-time detection of airborne fluorescent bioparticles in Antarctica

NASA Astrophysics Data System (ADS)

Crawford, Ian; Gallagher, Martin W.; Bower, Keith N.; Choularton, Thomas W.; Flynn, Michael J.; Ruske, Simon; Listowski, Constantino; Brough, Neil; Lachlan-Cope, Thomas; Fleming, Zoë L.; Foot, Virginia E.; Stanley, Warren R.

2017-12-01

We demonstrate, for the first time, continuous real-time observations of airborne bio-fluorescent aerosols recorded at the British Antarctic Survey's Halley VI Research Station, located on the Brunt Ice Shelf close to the Weddell Sea coast (lat 75°34'59'' S, long 26°10'0'' W) during Antarctic summer, 2015. As part of the NERC MAC (Microphysics of Antarctic Clouds) aircraft aerosol cloud interaction project, observations with a real-time ultraviolet-light-induced fluorescence (UV-LIF) spectrometer were conducted to quantify airborne biological containing particle concentrations along with dust particles as a function of wind speed and direction over a 3-week period. Significant, intermittent enhancements of both non- and bio-fluorescent particles were observed to varying degrees in very specific wind directions and during strong wind events. Analysis of the particle UV-induced emission spectra, particle sizes and shapes recorded during these events suggest the majority of particles were likely a subset of dust with weak fluorescence emission responses. A minor fraction, however, were likely primary biological particles that were very strongly fluorescent, with a subset identified as likely being pollen based on comparison with laboratory data obtained using the same instrument. A strong correlation of bio-fluorescent particles with wind speed was observed in some, but not all, periods. Interestingly, the fraction of fluorescent particles to total particle concentration also increased significantly with wind speed during these events. The enhancement in concentrations of these particles could be interpreted as due to resuspension from the local ice surface but more likely due to emissions from distal sources within Antarctica as well as intercontinental transport. Likely distal sources identified by back trajectory analyses and dispersion modelling were the coastal ice margin zones in Halley Bay consisting of bird colonies with likely associated high bacterial activity together with contributions from exposed ice margin bacterial colonies but also long-range transport from the southern coasts of Argentina and Chile. Dispersion modelling also demonstrated emissions from shipping lanes, and therefore marine anthropogenic sources cannot be ruled out. Average total concentrations of total fluorescent aerosols were found to be 1.9 ± 2.6 L-1 over a 3-week period crossing over from November into December, but peak concentrations during intermittent enhancement events could be up to several tens per litre. While this short pilot study is not intended to be generally representative of Antarctic aerosol, it demonstrates the usefulness of the UV-LIF measurement technique for quantification of airborne bioaerosol concentrations and to understand their dispersion. The potential importance for microbial colonisation of Antarctica is highlighted.

Fluorescent biological aerosol particles measured with the Waveband Integrated Bioaerosol Sensor WIBS-4: laboratory tests combined with a one year field study

NASA Astrophysics Data System (ADS)

Toprak, E.; Schnaiter, M.

2013-01-01

In this paper bioaerosol measurements conducted with the Waveband Integrated Bioaerosol Sensor mark 4 (WIBS-4) are presented. The measurements comprise aerosol chamber characterization experiments and a one-year ambient measurement period at a semi-rural site in South Western Germany. This study aims to investigate the sensitivity of WIBS-4 to biological and non-biological aerosols and detection of biological particles in the ambient aerosol. Several types of biological and non-biological aerosol samples, including fungal spores, bacteria, mineral dust, ammonium sulphate, combustion soot, and fluorescent polystyrene spheres, were analyzed by WIBS-4 in the laboratory. The results confirm the sensitivity of the ultraviolet light-induced fluorescence (UV-LIF) method to biological fluorophores and show the good discrimination capabilities of the two excitation wavelengths/detection wavebands method applied in WIBS-4. However, a weak cross-sensitivity to non-biological fluorescent interferers remains and is discussed in this paper. All the laboratory studies have been undertaken in order to prepare WIBS-4 for ambient aerosol measurements. According to the one-year ambient aerosol study, number concentration of fluorescent biological aerosol particles (FBAP) show strong seasonal and diurnal variability. The highest number concentration of FBAP was measured during the summer term and decreased towards the winter period when colder and drier conditions prevail. Diurnal FBAP concentrations start to increase after sunset and reach maximum values during the late night and early morning hours. On the other hand, the total aerosol number concentration was almost always higher during daytime than during nighttime and a sharp decrease after sunset was observed. There was no correlation observed between the FBAP concentration and the meteorological parameters temperature, precipitation, wind direction and wind speed. However, a clear correlation was identified between the FBAP number concentration and the relative humidity. Humidity-controlled release mechanisms of some fungal spore species are discussed as a possible explanation.

Climatology of Ultra Violet (UV) irradiance as measured through the Belgian ground-based monitoring network during the time period of 1995-2014

NASA Astrophysics Data System (ADS)

Pandey, Praveen; Gillotay, Didier; Depiesse, Cedric

2016-04-01

In this study we describe the network of ground-based ultraviolet (UV) radiation monitoring stations in Belgium. The evolution of the entire network, together with the details of measuring instruments is given. The observed cumulative irradiances -UVB, UVA and total solar irradiance (TSI)- over the course of measurement for three stations -a northern (Ostende), central (Uccle) and a southern (Redu)- are shown. The longest series of measurement shown in this study is at Uccle, Brussels, from 1995 till 2014. Thus, the variation of the UV index (UVI), together with the variation of irradiances during summer and winter months at Uccle are shown as a part of this climatological study. The trend of UVB irradiance over the above mentioned three stations is shown. This UVB trend is studied in conjunction with the long-term satellite-based total column ozone value over Belgium, which shows two distinct trends marked by a change point. The total column ozone trend following the change point is positive. It is also seen that the UVB trend is positive for the urban/sub-urban sites: Uccle and Redu. Whereas the UVB trend at Ostende, which is a coastal site, is not positive. A possible explanation of this relation between total column ozone and UVB trend could be associated with aerosols, which is shown in this paper by means of a radiative transfer model based study -as a part of a preliminary investigation. It is seen that the UVI is influenced by the type of aerosols.

Development of a Bioaerosol single particle detector (BIO IN) for the Fast Ice Nucleus CHamber FINCH

NASA Astrophysics Data System (ADS)

Bundke, U.; Reimann, B.; Nillius, B.; Jaenicke, R.; Bingemer, H.

2010-02-01

In this work we present the setup and first tests of our new BIO IN detector. This detector was constructed to classify atmospheric ice nuclei (IN) for their biological content. It is designed to be coupled to the Fast Ice Nucleus CHamber FINCH. If one particle acts as an ice nucleus, it will be at least partly covered with ice at the end of the development section of the FINCH chamber. The device combines an auto-fluorescence detector and a circular depolarization detector for simultaneous detection of biological material and discrimination between water droplets, ice crystals and non activated large aerosol particles. The excitation of biological material with UV light and analysis of auto-fluorescence is a common principle used for flow cytometry, fluorescence microscopy, spectroscopy and imaging. The detection of auto-fluorescence of airborne single particles demands some more experimental effort. However, expensive commercial sensors are available for special purposes, e.g. size distribution measurements. But these sensors will not fit the specifications needed for the FINCH IN counter (e.g. high sample flow of up 10 LPM). The newly developed -low cost- BIO IN sensor uses a single high-power UV LED for the electronic excitation instead of much more expensive UV lasers. Other key advantages of the new sensor are the low weight, compact size, and the little effect on the aerosol sample, which allows it to be coupled with other instruments for further analysis. The instrument will be flown on one of the first missions of the new German research aircraft "HALO" (High Altitude and LOng range).

Solar UV radiation exposure of seamen - Measurements, calibration and model calculations of erythemal irradiance along ship routes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feister, Uwe; Meyer, Gabriele; Kirst, Ulrich

2013-05-10

Seamen working on vessels that go along tropical and subtropical routes are at risk to receive high doses of solar erythemal radiation. Due to small solar zenith angles and low ozone values, UV index and erythemal dose are much higher than at mid-and high latitudes. UV index values at tropical and subtropical Oceans can exceed UVI = 20, which is more than double of typical mid-latitude UV index values. Daily erythemal dose can exceed the 30-fold of typical midlatitude winter values. Measurements of erythemal exposure of different body parts on seamen have been performed along 4 routes of merchant vessels.more » The data base has been extended by two years of continuous solar irradiance measurements taken on the mast top of RV METEOR. Radiative transfer model calculations for clear sky along the ship routes have been performed that use satellite-based input for ozone and aerosols to provide maximum erythemal irradiance and dose. The whole data base is intended to be used to derive individual erythemal exposure of seamen during work-time.« less

DETAILED ANALYSIS OF SOA ORIGINATING FROM THE PHOTOOXIDATION OF D-LIMONENE IN THE PRESENCE OF NO X AND UV LIGHT AND ITS IMPLICATION TO AMBIENT PM 2.5

EPA Science Inventory

A detailed analysis was carried out of the aerosol phase originated from the photooxidation of d-limonene in the presence of NO_x and artificial light with the analytical emphasis on the identification of oxygenated organic compounds. The major components included six ...

Validating Above-cloud Aerosol Optical Depth Retrieved from MODIS using NASA Ames Airborne Sun-Tracking Photometric and Spectrometric (AATS and 4STAR) Measurements

NASA Astrophysics Data System (ADS)

Jethva, H. T.; Torres, O.; Remer, L. A.; Redemann, J.; Dunagan, S. E.; Livingston, J. M.; Shinozuka, Y.; Kacenelenbogen, M. S.; Segal-Rosenhaimer, M.

2014-12-01

Absorbing aerosols produced from biomass burning and dust outbreaks are often found to overlay the lower level cloud decks as evident in the satellite images. In contrast to the cloud-free atmosphere, in which aerosols generally tend to cool the atmosphere, the presence of absorbing aerosols above cloud poses greater potential of exerting positive radiative effects (warming) whose magnitude directly depends on the aerosol loading above cloud, optical properties of clouds and aerosols, and cloud fraction. In recent years, development of algorithms that exploit satellite-based passive measurements of ultraviolet (UV), visible, and polarized light as well as lidar-based active measurements constitute a major breakthrough in the field of remote sensing of aerosols. While the unprecedented quantitative information on aerosol loading above cloud is now available from NASA's A-train sensors, a greater question remains ahead: How to validate the satellite retrievals of above-cloud aerosols (ACA)? Direct measurements of ACA such as carried out by the NASA Ames Airborne Tracking Sunphotometer (AATS) and Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) can be of immense help in validating ACA retrievals. In this study, we validate the ACA optical depth retrieved using the 'color ratio' (CR) method applied to the MODIS cloudy-sky reflectance by using the airborne AATS and 4STAR measurements. A thorough search of the historic AATS-4STAR database collected during different field campaigns revealed five events where biomass burning, dust, and wildfire-emitted aerosols were found to overlay lower level cloud decks observed during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS-2013, respectively. The co-located satellite-airborne measurements revealed a good agreement (root-mean-square-error<0.1 for Aerosol Optical Depth (AOD) at 500 nm) with most matchups falling within the estimated uncertainties in the MODIS retrievals (-10% to +50%). An extensive validation of satellite-based ACA retrievals requires equivalent field measurements particularly over the regions where ACA are often observed from satellites, i.e., south-eastern Atlantic Ocean, tropical Atlantic Ocean, northern Arabian Sea, South-East and North-East Asia.

Aerosol optical properties and radiative effects: Assessment of urban aerosols in central China using 10-year observations

NASA Astrophysics Data System (ADS)

Zhang, Ming; Ma, Yingying; Gong, Wei; Liu, Boming; Shi, Yifan; Chen, ZhongYong

2018-06-01

Poor air quality episodes are common in central China. Here, based on 10 years of ground-based sun-photometric observations, aerosol optical and radiative forcing characteristics were analyzed in Wuhan, the biggest metropolis in central China. Aerosol optical depth (AOD) in the last decade declined significantly, while the Ångström exponent (AE) showed slight growth. Single scattering albedo (SSA) at 440 nm reached the lowest value (0.87) in winter and highest value (0.93) in summer. Aerosol parameters derived from sun-photometric observations were used as input in a radiative transfer model to calculate aerosol radiative forcing (ARF) on the surface in ultraviolet (UV), visible (VIS), near-infrared (NIR), and shortwave (SW) spectra. ARFSW sustained decreases (the absolute values) over the last 10 years. In terms of seasonal variability, due to the increases in multiple scattering effects and attenuation of the transmitted radiation as AOD increased, ARF in summer displayed the largest value (-73.94 W/m2). After eliminating the influence of aerosol loading, the maximum aerosol radiative forcing efficiency in SW range (ARFESW) achieved a value of -64.5 W/m2/AOD in April. The ARFE change in each sub-interval spectrum was related to the change in SSA and effective radius of fine mode particles (Refff), that is, ARFE increased with the decreases in SSA and Refff. The smallest contribution of ARFENIR to ARFESW was 34.11% under strong absorbing and fine particle conditions, and opposite results were found for the VIS range, whose values were always over 51.82%. Finally, due to the serious air pollution and frequency of haze day, aerosol characteristics in haze and clear days were analyzed. The percentage of ARFENIR increased from 35.71% on clear-air days to 37.63% during haze periods, while both the percentage of ARFEUV and ARFENIR in ARFESW kept decreasing. The results of this paper should help us to better understand the effect of aerosols on solar spectral radiation and to develop improved the aerosol models over central China.

UV-VIS backscattering measurements on atmospheric particles mixture using polarization lidar coupled with numerical simulations and laboratory experiments

NASA Astrophysics Data System (ADS)

Miffre, Alain; Francis, Mirvatte; Anselmo, Christophe; Rairoux, Patrick

2015-04-01

As underlined by the latest IPCC report [1], tropospheric aerosols are nowadays recognized as one of the main uncertainties affecting the Earth's climate and human health. This issue is not straightforward due to the complexity of these nanoparticles, which present a wide range of sizes, shapes and chemical composition, which vary as a function of altitude, especially in the troposphere, where strong temperature variations are encountered under different water vapour content (from 10 to 100 % relative humidity). During this oral presentation, I will first present the scientific context of this research. Then, the UV-VIS polarimeter instrument and the subsequent calibration procedure [2] will be presented, allowing quantitative evaluation of particles backscattering coefficients in the atmosphere. In this way, up to three-component particles external mixtures can be partitioned into their spherical and non-spherical components, by coupling UV-VIS depolarization lidar measurements with numerical simulations of backscattering properties specific to non-spherical particles, such as desert dust or sea-salt particles [3], by applying the T-matrix numerical code [4]. This combined methodology is new, as opposed to the traditional approach using the lidar and T-matrix methodologies separately. In complement, recent laboratory findings [5] and field applications [6] will be presented, enhancing the sensitivity of the UV-VIS polarimeter. References [1] IPCC report, Intergovernmental Panel on Climate Change, IPCC, (2013). [2] G. David, A. Miffre, B. Thomas, and P. Rairoux: "Sensitive and accurate dual-wavelength UV-VIS polarization detector for optical remote sensing of tropospheric aerosols," Appl. Phys. B 108, 197-216 (2012). [3] G. David, B. Thomas, T. Nousiainen, A. Miffre and P. Rairoux: "Retrieving simulated volcanic, desert dust, and sea-salt particle properties from two / three-component particle mixtures using UV-VIS polarization Lidar and T-matrix," Atmos. Chem Phys. 13, 6757-6776 (2013). [4] M.I. Mishchenko, L.D. Travis and A.A. Lacis: "Scattering, absorption and emission of Light by small particles," 3rd edition, Cambridge University Press UK, (2002). [5] G. David, B. Thomas, E. Coillet, A. Miffre, and P. Rairoux, Polarization-resolved exact light backscattering by an ensemble of particles in air, Opt. Exp., 21, No. 16, 18624-18639, (2013). [6] G. David, B. Thomas, Y. Dupart, B. D'Anna, C. George, A. Miffre and P. Rairoux, UV polarization lidar for remote sensing new particles formation in the atmosphere, Opt. Exp., 22, A1009-A1022, (2014).

On an improvement of UV index forecast: UV index diagnosis and forecast for Belsk, Poland, in Spring/Summer 1999

NASA Astrophysics Data System (ADS)

Krzyścin, J. W.; Jaroslawski, J.; Sobolewski, P.

2001-10-01

A forecast of the UV index for the following day is presented. The standard approach to the UV index modelling is applied, i.e., the clear-sky UV index is multiplied by the UV cloud transmission factor. The input to the clear-sky model (tropospheric ultraviolet and visible-TUV model, Madronich, in: M. Tevini (Ed.), Environmental Effects of Ultraviolet Radiation, Lewis Publisher, Boca Raton, /1993, p. 17) consists of the total ozone forecast (by a regression model using the observed and forecasted meteorological variables taken as the initial values of aviation (AVN) global model and their 24-hour forecasts, respectively) and aerosols optical depth (AOD) forecast (assumed persistence). The cloud transmission factor forecast is inferred from the 24-h AVN model run for the total (Sun/+sky) solar irradiance at noon. The model is validated comparing the UV index forecasts with the observed values, which are derived from the daily pattern of the UV erythemal irradiance taken at Belsk (52°N,21°E), Poland, by means of the UV Biometer Solar model 501A for the period May-September 1999. Eighty-one percent and 92% of all forecasts fall into /+/-1 and /+/-2 index unit range, respectively. Underestimation of UV index occurs only in 15%. Thus, the model gives a high security in Sun protection for the public. It is found that in /~35% of all cases a more accurate forecast of AOD is needed to estimate the daily maximum of clear-sky irradiance with the error not exceeding 5%. The assumption of the persistence of the cloud characteristics appears as an alternative to the 24-h forecast of the cloud transmission factor in the case when the AVN prognoses are not available.

Photochemistry of aqueous pyruvic acid

PubMed Central

Griffith, Elizabeth C.; Carpenter, Barry K.; Shoemaker, Richard K.; Vaida, Veronica

2013-01-01

The study of organic chemistry in atmospheric aerosols and cloud formation is of interest in predictions of air quality and climate change. It is now known that aqueous phase chemistry is important in the formation of secondary organic aerosols. Here, the photoreactivity of pyruvic acid (PA; CH3COCOOH) is investigated in aqueous environments characteristic of atmospheric aerosols. PA is currently used as a proxy for α-dicarbonyls in atmospheric models and is abundant in both the gas phase and the aqueous phase (atmospheric aerosols, fog, and clouds) in the atmosphere. The photoreactivity of PA in these phases, however, is very different, thus prompting the need for a mechanistic understanding of its reactivity in different environments. Although the decarboxylation of aqueous phase PA through UV excitation has been studied for many years, its mechanism and products remain controversial. In this work, photolysis of aqueous PA is shown to produce acetoin (CH3CHOHCOCH3), lactic acid (CH3CHOHCOOH), acetic acid (CH3COOH), and oligomers, illustrating the progression from a three-carbon molecule to four-carbon and even six-carbon molecules through direct photolysis. These products are detected using vibrational and electronic spectroscopy, NMR, and MS, and a reaction mechanism is presented accounting for all products detected. The relevance of sunlight-initiated PA chemistry in aqueous environments is then discussed in the context of processes occurring on atmospheric aerosols. PMID:23821751

Changes in tropospheric composition and air quality due to stratospheric ozone depletion.

PubMed

Solomon, Keith R; Tang, Xiaoyan; Wilson, Stephen R; Zanis, Prodromos; Bais, Alkiviadis F

2003-01-01

Increased UV-B through stratospheric ozone depletion leads to an increased chemical activity in the lower atmosphere (the troposphere). The effect of stratospheric ozone depletion on tropospheric ozone is small (though significant) compared to the ozone generated anthropogenically in areas already experiencing air pollution. Modeling and experimental studies suggest that the impacts of stratospheric ozone depletion on tropospheric ozone are different at different altitudes and for different chemical regimes. As a result the increase in ozone due to stratospheric ozone depletion may be greater in polluted regions. Attributable effects on concentrations are expected only in regions where local emissions make minor contributions. The vertical distribution of NOx (NO + NO2), the emission of volatile organic compounds and the abundance of water vapor, are important influencing factors. The long-term nature of stratospheric ozone depletion means that even a small increase in tropospheric ozone concentration can have a significant impact on human health and the environment. Trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA) are produced by the atmospheric degradation of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). TFA has been measured in rain, rivers, lakes, and oceans, the ultimate sink for these and related compounds. Significant anthropogenic sources of TFA other than degradation HCFCs and HFCs have been identified. Toxicity tests under field conditions indicate that the concentrations of TFA and CDFA currently produced by the atmospheric degradation of HFCs and HCFCs do not present a risk to human health and the environment. The impact of the interaction between ozone depletion and future climate change is complex and a significant area of current research. For air quality and tropospheric composition, a range of physical parameters such as temperature, cloudiness and atmospheric transport will modify the impact of UV-B. Changes in the chemical composition of the atmosphere including aerosols will also have an impact. For example, tropospheric OH is the 'cleaning' agent of the troposphere. While increased UV-B increases the OH concentration, increases in concentration of gases like methane, carbon monoxide and volatile organic compounds will act as sinks for OH in troposphere and hence change air quality and chemical composition in the troposphere. Also, changes in the aerosol content of the atmosphere resulting from global climate change may affect ozone photolysis rate coefficients and hence reduce or increase tropospheric ozone concentrations.

Progress in Near Real-Time Volcanic Cloud Observations Using Satellite UV Instruments

NASA Astrophysics Data System (ADS)

Krotkov, N. A.; Yang, K.; Vicente, G.; Hughes, E. J.; Carn, S. A.; Krueger, A. J.

2011-12-01

Volcanic clouds from explosive eruptions can wreak havoc in many parts of the world, as exemplified by the 2010 eruption at the Eyjafjöll volcano in Iceland, which caused widespread disruption to air traffic and resulted in economic impacts across the globe. A suite of satellite-based systems offer the most effective means to monitor active volcanoes and to track the movement of volcanic clouds globally, providing critical information for aviation hazard mitigation. Satellite UV sensors, as part of this suite, have a long history of making unique near-real time (NRT) measurements of sulfur dioxide (SO2) and ash (aerosol Index) in volcanic clouds to supplement operational volcanic ash monitoring. Recently a NASA application project has shown that the use of near real-time (NRT,i.e., not older than 3 h) Aura/OMI satellite data produces a marked improvement in volcanic cloud detection using SO2 combined with Aerosol Index (AI) as a marker for ash. An operational online NRT OMI AI and SO2 image and data product distribution system was developed in collaboration with the NOAA Office of Satellite Data Processing and Distribution. Automated volcanic eruption alarms, and the production of volcanic cloud subsets for multiple regions are provided through the NOAA website. The data provide valuable information in support of the U.S. Federal Aviation Administration goal of a safe and efficient National Air Space. In this presentation, we will highlight the advantages of UV techniques and describe the advances in volcanic SO2 plume height estimation and enhanced volcanic ash detection using hyper-spectral UV measurements, illustrated with Aura/OMI observations of recent eruptions. We will share our plan to provide near-real-time volcanic cloud monitoring service using the Ozone Mapping and Profiler Suite (OMPS) on the Joint Polar Satellite System (JPSS).

Nanominerals, fullerene aggregates, and hazardous elements in coal and coal combustion-generated aerosols: An environmental and toxicological assessment.

PubMed

Saikia, Jyotilima; Narzary, Bardwi; Roy, Sonali; Bordoloi, Manobjyoti; Saikia, Prasenjit; Saikia, Binoy K

2016-12-01

Studies on coal-derived nanoparticles as well as nano-minerals are important in the context of the human health and the environment. The coal combustion-generated aerosols also affect human health and environmental quality aspects in any coal-fired station. In this study, the feed coals and their combustion-generated aerosols from coal-fired boilers of two tea industry facilities were investigated for the presence of nanoparticles/nano minerals, fullerene aggregates, and potentially hazardous elements (PHEs). The samples were characterized by using X-ray diffraction (XRD), Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), High resolution-transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) and Ultra Violet-visible spectroscopy (UV-Vis) to know their extent of environmental risks to the human health when present in coals and aerosols. The feed coals contain mainly clay minerals, whilst glass fragments, spinel, quartz, and other minerals occur in lesser quantities. The PM samples contain potentially hazardous elements (PHEs) like As, Pb, Cd and Hg. Enrichment factor of the trace elements in particulate matters (PMs) was calculated to determine their sources. The aerosol samples were also found to contain nanomaterials and ultrafine particles. The fullerene aggregates along with potentially hazardous elements were also detected in the aerosol samples. The cytotoxicity studies on the coal combustion-generated PM samples show their potential risk to the human health. This detailed investigation on the inter-relationship between the feed coals and their aerosol chemistry will be useful for understanding the extent of environmental hazards and related human health risk. Copyright © 2016 Elsevier Ltd. All rights reserved.

The application of chemical and isotopic tracers to characterize aerosol sources and processing in marine air

NASA Astrophysics Data System (ADS)

Turekian, Vaughan Charles

2000-12-01

Aerosol production, transport, chemical and physical evolution and deposition impact the environment by influencing radiation budgets, altering the composition of the atmosphere, and delivering nutrients to marine and terrestrial ecosystems. The objective of this research was to combine high-resolution chemical measurements with stable isotopic analysis in order to characterize the sources and processing of carbon, nitrogen and sulfur bearing compounds, associated with sized aerosols on Bermuda, during spring. Chemical tracers combined with forward and backward trajectories demonstrated the transport of biomass burning products from North America to Bermuda. The size distributions of NH4+ from 1998 differed from those during spring, 1997, a year without the large-scale burning. These results suggest that transport of biomass burning products altered the pH of the aerosols. Marine and continentally derived carbon was associated with all aerosol size fractions. Supermicron radius sea- salt aerosol was enriched in marine derived carbon by 2 orders of magnitude compared to bulk surface seawater. Enrichments of oxalate relative to methanesulfonic acid (MSA) in supermicron radius aerosol suggested in situ formation of oxalate within the sea-salt solution, or direct injection from the organic rich surface microlayer. Compound specific isotope analysis of oxalic acid, indicated a marine source for all aerosol size fractions, indicating formation from in the gas phase for the submicron radius aerosol. Stable sulfur isotopes indicated that the biogenic non- sea-salt (nss) SO42-/MSA ratio varied with aerosol size indicating that MSA may not be a conservative tracer of biogenic nss SO4 2- in bulk aerosol sampling. The calculated biogenic nss SO 42-/MSA based on stable isotopes and sized aerosol sampling, was 3 times lower than previous estimates for Bermuda. Stable nitrogen isotope values for submicron and supermicron aerosol where significantly different, consistent with their different chemical compositions. Results suggested that HNO3 incorporation into supermicron aerosol was essentially unidirectional whereas submicron aerosol was both a source and a sink for NH3(g). Variable aerosol liquid water content over the relatively longer atmospheric lifetimes of submicron aerosol may lead to multiple NH3 phase changes. This study was the first to combine sized aerosol sampling, high-resolution chemical analysis and multiple stable isotopes to characterize both the sources and the processing of aerosols in marine air. The results of this study, therefore, provide crucial information for source apportionment of environmentally important atmospheric species in continentally impacted, marine air.

Study of the anticorrelations between ozone and UV-B radiation using linear and exponential fits in Southern Brazil

NASA Astrophysics Data System (ADS)

Guarnieri, R.; Padilha, L.; Guarnieri, F.; Echer, E.; Makita, K.; Pinheiro, D.; Schuch, A.; Boeira, L.; Schuch, N.

Ultraviolet radiation type B (UV-B 280-315nm) is well known by its damage to life on Earth, including the possibility of causing skin cancer in humans. However, the atmo- spheric ozone has absorption bands in this spectral radiation, reducing its incidence on Earth's surface. Therefore, the ozone amount is one of the parameters, besides clouds, aerosols, solar zenith angles, altitude, albedo, that determine the UV-B radia- tion intensity reaching the Earth's surface. The total ozone column, in Dobson Units, determined by TOMS spectrometer on board of a NASA satellite, and UV-B radiation measurements obtained by a UV-B radiometer model MS-210W (Eko Instruments) were correlated. The measurements were obtained at the Observatório Espacial do Sul - Instituto Nacional de Pesquisas Espaciais (OES/CRSPE/INPE-MCT) coordinates: Lat. 29.44oS, Long. 53.82oW. The correlations were made using UV-B measurements in fixed solar zenith angles and only days with clear sky were selected in a period from July 1999 to December 2001. Moreover, the mathematic behavior of correlation in dif- ferent angles was observed, and correlation coefficients were determined by linear and first order exponential fits. In both fits, high correlation coefficients values were ob- tained, and the difference between linear and exponential fit can be considered small.

Estimations of the Global Distribution and Time Series of UV Noontime Irradiance (305, 310, 324, 380 nm, and Erythemal) from TOMS and SeaWiFS Data

NASA Technical Reports Server (NTRS)

Herman, J.

2004-01-01

The amount of UV irradiance reaching the Earth's surface is estimated from the measured cloud reflectivity, ozone, aerosol amounts, and surface reflectivity time series from 1980 to 1992 and 1997 to 2000 to estimate changes that have occurred over a 21-year period. Recent analysis of the TOMS data shows that there has been an apparent increase in reflectivity (decrease in W) in the Southern Hemisphere that is related to a calibration error in EP-TOMS. Data from the well-calibrated SeaWiFS satellite instrument have been used to correct the EP-TOMS reflectivity and UV time series. After correction, some of the local trend features seen in the N7 time series (1980 to 1992) have been continued in the combined time series, but the overall zonal average and global trends have changed. In addition to correcting the EP-TOMS radiance calibration, the use of SeaWiFS cloud data permits estimation of UV irradiance at higher spatial resolution (1 to 4 km) than is available from TOMS (100 km) under the assumption that ozone is slowly varying over a scale of 100 km. The key results include a continuing decrease in cloud cover over Europe and North America with a corresponding increase in UV and a decrease in UV irradiance near Antarctica.

A new method for estimating UV fluxes at ground level in cloud-free conditions

NASA Astrophysics Data System (ADS)

Wandji Nyamsi, William; Pitkänen, Mikko R. A.; Aoun, Youva; Blanc, Philippe; Heikkilä, Anu; Lakkala, Kaisa; Bernhard, Germar; Koskela, Tapani; Lindfors, Anders V.; Arola, Antti; Wald, Lucien

2017-12-01

A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties and total column ozone that are produced by the Copernicus Atmosphere Monitoring Service (CAMS). The estimates from this new method have been compared to instantaneous measurements of global UV irradiances made in cloud-free conditions at five stations at high latitudes in various climates. For the UV-A irradiance, the bias ranges between -0.8 W m-2 (-3 % of the mean of all data) and -0.2 W m-2 (-1 %). The root mean square error (RMSE) ranges from 1.1 W m-2 (6 %) to 1.9 W m-2 (9 %). The coefficient of determination R2 is greater than 0.98. The bias for UV-B is between -0.04 W m-2 (-4 %) and 0.08 W m-2 (+13 %) and the RMSE is 0.1 W m-2 (between 12 and 18 %). R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products. Improvements, especially in the modeling of the reflectivity of the Earth's surface in the UV region, are necessary prior to its inclusion into an operational tool.

Characterization of fresh and aged organic aerosol emissions from meat charbroiling

NASA Astrophysics Data System (ADS)

Kaltsonoudis, Christos; Kostenidou, Evangelia; Louvaris, Evangelos; Psichoudaki, Magda; Tsiligiannis, Epameinondas; Florou, Kalliopi; Liangou, Aikaterini; Pandis, Spyros N.

2017-06-01

Cooking emissions can be a significant source of fine particulate matter in urban areas. In this study the aerosol- and gas-phase emissions from meat charbroiling were characterized. Greek souvlakia with pork were cooked using a commercial charbroiler and a fraction of the emissions were introduced into a smog chamber where after a characterization phase they were exposed to UV illumination and oxidants. The particulate and gas phases were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a proton-transfer-reaction mass spectrometer (PTR-MS) correspondingly. More than 99 % of the aerosol emitted was composed of organic compounds, while black carbon (BC) contributed 0.3 % and the inorganic species less than 0.5 % of the total aerosol mass. The initial O : C ratio was approximately 0.09 and increased up to 0.30 after a few hours of chemical aging (exposures of 1010 molecules cm-3 s for OH and 100 ppb h for ozone). The initial and aged AMS spectra differed considerably (θ = 27°). Ambient measurements were also conducted during Fat Thursday in Patras, Greece, when traditionally meat is charbroiled everywhere in the city. Positive matrix factorization (PMF) revealed that cooking organic aerosol (COA) reached up to 85 % of the total OA from 10:00 to 12:00 LST that day. The ambient COA factor in two major Greek cities had a mass spectrum during spring and summer similar to the aged meat charbroiling emissions. In contrast, the ambient COA factor during winter resembled strongly the fresh laboratory meat charbroiling emissions.

Earth cloud, aerosol, and radiation explorer optical payload development status

NASA Astrophysics Data System (ADS)

Hélière, A.; Wallace, K.; Pereira do Carmo, J.; Lefebvre, A.

2017-09-01

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop as part of ESA's Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the ojective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth's atmosphere. EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. MSI is a compact instrument with a 150 km swath providing 500 m pixel data in seven channels, whose retrieved data will give context to the active instrument measurements, as well as providing cloud and aerosol information. BBR measures reflected solar and emitted thermal radiation from the scene. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes from ground to an altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol and molecular scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised components of the Mie scattering contribution are measured on dedicated channels. This paper will provide a description of the optical payload implementation, the design and characterisation of the instruments.

Formation kinetics and abundance of organic nitrates in α-pinene ozonolysis

NASA Astrophysics Data System (ADS)

Berkemeier, Thomas; Ammann, Markus; Pöschl, Ulrich; Shiraiwa, Manabu

2016-04-01

Formation of organic nitrates affects the total atmospheric budget of oxidized nitrogen (NOy) and alters the total aerosol mass yield from secondary sources. We investigated the formation of organic nitrate species during ozonolysis of α-pinene and subsequent formation of secondary organic aerosols (SOA) using the short-lived radioactive tracer 13N inside an aerosol flow reactor (Ammann et al., 2001). The results represent direct measurements of the organic nitrate content of α-pinene secondary aerosol and give insight into the kinetics of organic nitrate formation. Organic nitrates constituted up to 40 % of aerosol mass with a pronounced influence during the initial period of particle growth. Kinetic modelling, as well as additional experiments using OH scavengers and UV irradiation, suggests that organic peroxy radicals (RO2) from the reaction of α-pinene with secondarily produced OH are important intermediates in the organic nitrate formation process. Direct oxidation of α-pinene by NO3 was found to be a less efficient pathway for formation of particle phase nitrate. The organic nitrate content decreased very slightly with an increase of relative humidity on the experimental time scale. The experiments show a tight correlation between organic nitrate content and SOA number concentrations, implying that organic nitrates play an important role in nucleation and growth of nanoparticles. Since present in large amounts in organic aerosol, organic nitrates deposited in the lung might have implications for human health as they release nitric acid upon hydrolysis, especially in regions influenced by urban pollution and large sources of monoterpene SOA precursors. References Ammann et al. (2001) Radiochimica Acta 89, 831.

ISSARS Aerosol Database : an Incorporation of Atmospheric Particles into a Universal Tool to Simulate Remote Sensing Instruments

NASA Technical Reports Server (NTRS)

Goetz, Michael B.

2011-01-01

The Instrument Simulator Suite for Atmospheric Remote Sensing (ISSARS) entered its third and final year of development with an overall goal of providing a unified tool to simulate active and passive space borne atmospheric remote sensing instruments. These simulations focus on the atmosphere ranging from UV to microwaves. ISSARS handles all assumptions and uses various models on scattering and microphysics to fill the gaps left unspecified by the atmospheric models to create each instrument's measurements. This will help benefit mission design and reduce mission cost, create efficient implementation of multi-instrument/platform Observing System Simulation Experiments (OSSE), and improve existing models as well as new advanced models in development. In this effort, various aerosol particles are incorporated into the system, and a simulation of input wavelength and spectral refractive indices related to each spherical test particle(s) generate its scattering properties and phase functions. These atmospheric particles being integrated into the system comprise the ones observed by the Multi-angle Imaging SpectroRadiometer(MISR) and by the Multiangle SpectroPolarimetric Imager(MSPI). In addition, a complex scattering database generated by Prof. Ping Yang (Texas A&M) is also incorporated into this aerosol database. Future development with a radiative transfer code will generate a series of results that can be validated with results obtained by the MISR and MSPI instruments; nevertheless, test cases are simulated to determine the validity of various plugin libraries used to determine or gather the scattering properties of particles studied by MISR and MSPI, or within the Single-scattering properties of tri-axial ellipsoidal mineral dust particles database created by Prof. Ping Yang.

Optical properties and aging of light-absorbing secondary organic aerosol

DOE PAGES

Liu, Jiumeng; Lin, Peng; Laskin, Alexander; ...

2016-10-14

The light-absorbing organic aerosol (OA) commonly referred to as “brown carbon” (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NO x concentrations, photolysis time, and relative humidity (RH) on the lightmore » absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NO x concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NO x conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

DOE PAGES

Yu, L.; Smith, J.; Laskin, A.; ...

2014-08-19

Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl ( 3C*) and hydroxyl radical (·OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenated molecules aremore » identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85–1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than ·OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.« less

Characterization and testing of a new environmental chamber

NASA Astrophysics Data System (ADS)

Leskinen, A.; Yli-Pirilä, P.; Kuuspalo, K.; Sippula, O.; Jalava, P.; Hirvonen, M.-R.; Jokiniemi, J.; Virtanen, A.; Komppula, M.; Lehtinen, K. E. J.

2015-06-01

A 29 m3 Teflon chamber, designed for studies on the aging of combustion aerosols, at the University of Eastern Finland is described and characterized. The chamber is part of a research facility, called Ilmari, where small-scale combustion devices, a dynamometer for vehicle exhaust studies, dilution systems, the chamber, and cell and animal exposure devices are located side by side under the same roof. The small surface-to-volume ratio of the chamber enables reasonably long experiment times, with particle wall loss rate constants of 0.088, 0.080, 0.045, and 0.040 h-1 for polydisperse, 50, 100, and 200 nm monodisperse aerosols, respectively. The NO2 photolysis rate can be adjusted from 0 to 0.62 min-1. The irradiance spectrum is centered at either 350 or 365 nm, and the maximum irradiance, produced by up to 160 blacklight lamps, is 29.7 W m-2, which corresponds to the ultraviolet (UV) irradiance in Central Finland at noon on a sunny day in the midsummer. The temperature inside the chamber is uniform and can be kept at 25±1 °C. The chamber is kept in an overpressure with a moving top frame, which reduces sample dilution and entrance of contamination during an experiment. The functionality of the chamber was tested with oxidation experiments of toluene, resulting in secondary organic aerosol (SOA) yields of 12-42%, depending on the initial conditions, such as NOx concentration and UV irradiation. The highest gaseous oxidation product yields of 12.4-19.5% and 5.8-19.5% were detected with ions corresponding to methyl glyoxal (m/z 73.029) and 4-oxo-2-pentenal (m/z 99.044), respectively. Overall, reasonable yields of SOA and gaseous reaction products, comparable to those obtained in other laboratories, were obtained.

AERONET derived (BC) aerosol absorption

NASA Astrophysics Data System (ADS)

Kinne, S.

2015-12-01

AERONET is a ground-based sun-/sky-photometer network with good annual statistics at more than 400 sites worldwide. Inversion methods applied to these data define all relevant column aerosol optical properties and reveal even microphysical detail. The extracted data include estimates for aerosol size-distributions and for aerosol refractive indices at four different solar wavelengths. Hereby, the imaginary parts of the refractive indices define the aerosol column absorption. For regional and global averages and radiative impact assessment with off-line radiative transfer, these local data have been extended with distribution patterns offered by AeroCom modeling experiments. Annual and seasonal absorption distributions for total aerosol and estimates for component contributions (such as BC) are presented and associated direct forcing impacts are quantified.

Apparatus to collect, classify, concentrate, and characterize gas-borne particles

DOEpatents

Rader, Daniel J.; Torczynski, John R.; Wally, Karl; Brockmann, John E.

2003-12-16

An aerosol lab-on-a-chip (ALOC) integrates one or more of a variety of particle collection, classification, concentration (enrichment), an characterization processes onto a single substrate or layered stack of such substrates. By mounting a UV laser diode laser light source on the substrate, or substrates tack, so that it is located down-stream of the sample inlet port and at right angle the sample particle stream, the UV light source can illuminate individual particles in the stream to induce a fluorescence response in those particles having a fluorescent signature such as biological particles, some of said particles. An illuminated particle having a fluorescent signal above a threshold signal would trigger a sorter module that would separate that particle from the particle stream.

Evaluation of the health impact of aerosols emitted from different combustion sources: Comprehensive characterization of the aerosol physicochemical properties as well as the molecular biological and toxicological effects of the aerosols on human lung cells and macrophages.

NASA Astrophysics Data System (ADS)

Zimmermann, R.; Dittmar, G.; Kanashova, T.; Buters, J.; Öder, S.; Paur, H. R.; Mülhopt, S.; Dilger, M.; Weiss, C.; Harndorf, H.; Stengel, B.; Hirvonen, M. R.; Jokiniemi, J.; Hiller, K.; Sapcariu, S.; Sippula, O.; Streibel, T.; Karg, E.; Weggler, B.; Schnelle-Kreis, J.; Lintelmann, J.; Sklorz, M.; Orasche, J.; Müller, L.; Passig, J.; Gröger, T.; Jalava, P. I.; Happo, M.; Uski, O.

2016-12-01

A novel approach to evaluate the health effects of anthropogenic combustion emissions is the detailed comparison of comprehensive physicochemical data on the combustion aerosol properties with the biological response of aerosol-exposed lung cells. In this context the "HICE-Aerosol and Health" project consortium studies the properties as well as the biological and toxicological effects on lung cells induced by different combustion aerosol emissions (e.g. ship diesel exhaust, wood combustion effluents or automobile aerosol). Human alveolar epithelial cells (e.g. A549 cells) as well as murine macrophages were exposed to diluted emissions, using field deployable ALI-exposition systems in a mobile S2-biological laboratory. This allows a realistic lung-cell exposure by simulation of the lung situation. The cellular effects were then comprehensively characterized (cytotoxicology, transcriptomics, proteomics etc.) effects monitoring and put in context with the chemical and physical aerosol data. Emissions of wood combustion, a ship engine as well as diesel and gasoline engines were investigated. Furthermore for some experiments the atmospheric aging of the emission was simulated in a flow tube reactor using UV-light and ozone. Briefly the following order of cellular response-strength was observed: A relatively mild cellular effect is observed for the diluted wood combustion emissions, regardless if log-wood and pellet burner emissions are investigated. Similarly mild biological effects are observed for gasoline car emissions. The ship diesel engine emissions and construction machine diesel engine induced much more intense biological responses. A surprising result in this context is, that heavy fuel oil (HFO)-emissions show lower biological effect strengths than the supposedly cleaner diesel fuel emissions (DF). The HFO-emissions contain high concentrations of known toxicants (metals, polycyclic aromatics). This result was confirmed by experiments with murine macrophages. Detailed analyses suggest a large difference in relative toxicity for different combustion sources. Recently the cell experiments were successively evaluated and verified by animal exposure tests. This is important to develop a reliable animal-test free-monitoring method for aerosol-induced health effects.

Evaluation of the health impact of aerosols emitted from different combustion sources: Comprehensive characterization of the aerosol physicochemical properties as well as the molecular biological and toxicological effects of the aerosols on human lung cells and macrophages.

NASA Astrophysics Data System (ADS)

Zimmermann, R.; Dittmar, G.; Kanashova, T.; Buters, J.; Öder, S.; Paur, H. R.; Mülhopt, S.; Dilger, M.; Weiss, C.; Harndorf, H.; Stengel, B.; Hirvonen, M. R.; Jokiniemi, J.; Hiller, K.; Sapcariu, S.; Sippula, O.; Streibel, T.; Karg, E.; Weggler, B.; Schnelle-Kreis, J.; Lintelmann, J.; Sklorz, M.; Orasche, J.; Müller, L.; Passig, J.; Gröger, T.; Jalava, P. I.; Happo, M.; Uski, O.

2017-12-01

A novel approach to evaluate the health effects of anthropogenic combustion emissions is the detailed comparison of comprehensive physicochemical data on the combustion aerosol properties with the biological response of aerosol-exposed lung cells. In this context the "HICE-Aerosol and Health" project consortium studies the properties as well as the biological and toxicological effects on lung cells induced by different combustion aerosol emissions (e.g. ship diesel exhaust, wood combustion effluents or automobile aerosol). Human alveolar epithelial cells (e.g. A549 cells) as well as murine macrophages were exposed to diluted emissions, using field deployable ALI-exposition systems in a mobile S2-biological laboratory. This allows a realistic lung-cell exposure by simulation of the lung situation. The cellular effects were then comprehensively characterized (cytotoxicology, transcriptomics, proteomics etc.) effects monitoring and put in context with the chemical and physical aerosol data. Emissions of wood combustion, a ship engine as well as diesel and gasoline engines were investigated. Furthermore for some experiments the atmospheric aging of the emission was simulated in a flow tube reactor using UV-light and ozone. Briefly the following order of cellular response-strength was observed: A relatively mild cellular effect is observed for the diluted wood combustion emissions, regardless if log-wood and pellet burner emissions are investigated. Similarly mild biological effects are observed for gasoline car emissions. The ship diesel engine emissions and construction machine diesel engine induced much more intense biological responses. A surprising result in this context is, that heavy fuel oil (HFO)-emissions show lower biological effect strengths than the supposedly cleaner diesel fuel emissions (DF). The HFO-emissions contain high concentrations of known toxicants (metals, polycyclic aromatics). This result was confirmed by experiments with murine macrophages. Detailed analyses suggest a large difference in relative toxicity for different combustion sources. Recently the cell experiments were successively evaluated and verified by animal exposure tests. This is important to develop a reliable animal-test free-monitoring method for aerosol-induced health effects.

Fluorescent biological aerosol particles (FBAPs) measured with the Waveband Integrated Bioaerosol Sensor WIBS-4: laboratory tests combined with a one year field study

NASA Astrophysics Data System (ADS)

Toprak, E.; Schnaiter, M.

2012-07-01

In this paper bioaerosol measurements conducted with the Waveband Integrated Bioaerosol Sensor mark 4 (WIBS-4) are presented. The measurements comprise aerosol chamber characterization experiments and a one-year ambient measurement period at a semi-rural site in South Western Germany. This study aims to investigate the sensitivity of WIBS-4 to biological and non-biological aerosols, performance of WIBS-4 for discrimination of several types of aerosols, and the detection and identification of biological particles in the ambient aerosol. Several types of biological and non-biological aerosol samples including spores, bacteria, pollen, mineral dust, ammonium sulphate, combustion soot, and fluorescent polystyrene spheres were analysed by WIBS-4 in the laboratory. The results confirm the sensitivity of the Ultra Violet Light Induced Fluorescence (UV-LIF) method to biological fluorophores and show the good discrimination capabilities of the two wavelengths excitation/two wavebands detection method applied in WIBS-4. However, a weak cross-sensitivity to non-biological fluorescent interferers remains and is discussed in this paper. All the laboratory studies have been undertaken in order to prepare WIBS-4 for ambient aerosol measurements. According to the one year ambient aerosol study, number concentration of fluorescent biological aerosol particles (FBAP) show strong seasonal and diurnal variability. The highest number concentration of FBAP was measured during the summer term and it decreases towards the winter period when colder and drier conditions are prevailing. Diurnal FBAP concentrations start to increase after sunset and reach maximum values during the late night and early morning hours. On the other hand the total aerosol number concentration was always higher during day time than during night time and a sharp decrease after sunset was observed. There was no correlation observed between the FBAP concentration and the meteorological parameters temperature, precipitation, wind direction and wind speed. However a clear correlation was identified between the FBAP number concentration and the relative humidity. Humidity controlled release mechanisms of some fungal spore species are discussed as a possible explanation.

Biocompatible and Biomimetic Self-Assembly of Functional

DTIC Science & Technology

2007-10-03

rearrangement of the lipid/silica matrix to create a bio/nano interface quite similar to that formed by direct CDA. This approach has several advantages over CDA...precursors with a biologically compatible surfactant, glycerol monooleate ( GMO ) via dip-coating, spin-coating, drop-casting, or aerosol deposition...with water and remains in a semi-solid state. Upon exposure to UV/ozone, the GMO begins to photodecompose and the silanol precursors become more

Perturbation by UV Light for Rapid Classification of Biological Particles by Fluorescence

DTIC Science & Technology

2007-01-01

thuringiensis (israeliensis) 47,51 Bacillus cereus (T) 37 Clostridium perfringens 59 Gram Negative (GN) Bacteria Species (all vegetative) Escherichia coli (B...non-biological particles in aerosols.1 2𔃽 Almost all strains of species belonging to the bacterial genera Bacillus and Clostridium produce...endospores, the situation should be similar for all spores of Bacillus or Clostridium species. As a matter of fact, the results from other endospores

Disinfection of Airborne Organisms by Ultraviolet-C Radiation and Sunlight

DTIC Science & Technology

2012-07-01

organisms deposited on surfaces, suspended in water , and contaminating food, all of which have been discussed elsewhere (Block, 2001). In contrast, the... water . Therefore, the primary means for organism inactivation in aerosols is ultraviolet (UV) radiation. Radiation from the sunlight is used as a...cortex is essential for reduction of the water content in the spore core and formation of a dormant spore. The cortex is degraded in spore

Ultraviolet irradiation: An effective inactivation method of Aspergillus spp. in water for the control of waterborne nosocomial aspergillosis.

PubMed

Nourmoradi, H; Nikaeen, M; Stensvold, C R; Mirhendi, H

2012-11-15

Invasive aspergillosis is the second most common cause of nosocomial fungal infections and occurring mainly by Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger. There is evidence that nosocomial aspergillosis may be waterborne. This study was conducted to evaluate the ultraviolet (UV) irradiation efficiency in terms of inactivating the most important Aspergillus species in water since these are potential sources for nosocomial aspergillosis. A continuous flow UV reactor which could be used as a point-of-use (POU) system was used to survey Aspergillus inactivation by UV irradiation. The inactivation efficiency of UV fluence (4.15-25 mJ/cm(2)) was measured by determination of fungal density in water before and after radiation. Because turbidity and iron concentration are two major water quality factors impacting UV disinfection effectiveness, the potential influence of these factors on UV inactivation of Aspergillus spp. was also measured. The 4 log inactivation for A. fumigatus, A. niger and A. flavus at a density of 1000 cfu/ml was achieved at UV fluences of 12.45 mJ/cm(2), 16.6 mJ/cm(2) and 20.75 mJ/cm(2), respectively. The inactivation efficiency for lower density (100 cfu/ml) was the same as for the higher density except for A. flavus. The removal efficiency of Aspergillus spp. was decreased by increasing the turbidity and iron concentration. UV disinfection could effectively inactivate Aspergillus spores from water and eliminate potential exposure of high-risk patients to fungal aerosols by installation of POU UV systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Retrieval of Surface Ozone from UV-MFRSR Irradiances using Deep Learning

NASA Astrophysics Data System (ADS)

Chen, M.; Sun, Z.; Davis, J.; Zempila, M.; Liu, C.; Gao, W.

2017-12-01

High concentration of surface ozone is harmful to humans and plants. USDA UV-B Monitoring and Research Program (UVMRP) uses Ultraviolet (UV) version of Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR) to measure direct, diffuse, and total irradiances every three minutes at seven UV channels (i.e. 300, 305, 311, 317, 325, 332, and 368 nm channels with 2 nm full width at half maximum). Based on the wavelength dependency of aerosol optical depths, there have been plenty of literatures exploring retrieval methods of total column ozone from UV-MFRSR measurements. However, few has explored the retrieval of surface ozone. The total column ozone is the integral of the multiplication of ozone concentration (varying by height and time) and cross section (varying by wavelength and temperature) over height. Because of the distinctive values of ozone cross section in the UV region, the irradiances at seven UV channels have the potential to resolve the ozone concentration at multiple vertical layers. If the UV irradiances at multiple time points are considered together, the uncertainty or the vertical resolution of ozone concentrations can be further improved. In this study, the surface ozone amounts at the UVMRP station located at Billings, Oklahoma are estimated from the adjacent (i.e. within 200 miles) US Environmental Protection Agency (EPA) surface ozone observations using the spatial analysis technique. Then, the (direct normal) irradiances of UVMRP at one or more time points as inputs and the corresponding estimated surface ozone from EPA as outputs are fed into a pre-trained (dense) deep neural network (DNN) to explore the hidden non-linear relationship between them. This process could improve our understanding of their physical/mathematical relationship. Finally, the optimized DNN is tested with the preserved 5% of the dataset, which are not used during training, to verify the relationship.

Earth's UV Reflectivity Data from the Ozone Monitoring Instrument on EOS-Aura

NASA Astrophysics Data System (ADS)

Larko, D. E.; Mao, J.; Herman, J. R.; Huang, L.; Qin, W.; Labow, G. J.; Lloyd, S. A.; DeLand, M. T.

2011-12-01

The Lambert Equivalent Reflectivity (LER), derived from satellite ultraviolet (UV) radiance measurements, represents the equivalent scene reflectivity of the Earth's surface and atmosphere without Rayleigh scattering. It provides a better opportunity to quantify variations of the planetary reflectance and albedo associated with snow/ice, atmospheric aerosols and clouds, since UV reflectance is very low over most land surfaces and water. LER values at 340 nm from the Ozone Monitoring Instrument (OMI) on EOS-Aura have been generated as a new product from the OMI TO3 ozone retrieval algorithm and provided to users in HDF format. The wide field of view of OMI (~2200 km) provides complete global coverage every day with 13 km x 24 km resolution at nadir. These data are then mapped to 1 degree x 1 degree latitude-longitude grid as daily and monthly means for weather and climate studies. The OMI LER data set has been used to validate other UV LER data sets from NOAA and NASA polar orbiting satellites, and has been combined with these data sets to construct a continuous long-term data record of terrestrial UV reflectivity. This paper will present details about the data processing and format of the OMI LER product. Applications of this data set in global climate studies will be demonstrated and discussed in this presentation.

Impacts of Brown Carbon from Biomass Burning on Surface UV and Ozone Photochemistry in the Amazon Basin

NASA Technical Reports Server (NTRS)

Mok, Jungbin; Krotkov, Nickolay A.; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F.; Li, Zhangqing; Dickerson, Russell R.;

Impacts of brown carbon from biomass burning on surface UV and ozone photochemistry in the Amazon Basin.

PubMed

Mok, Jungbin; Krotkov, Nickolay A; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F; Li, Zhanqing; Dickerson, Russell R; Stenchikov, Georgiy L; Osipov, Sergey; Ren, Xinrong

2016-11-11

The spectral dependence of light absorption by atmospheric particulate matter has major implications for air quality and climate forcing, but remains uncertain especially in tropical areas with extensive biomass burning. In the September-October 2007 biomass-burning season in Santa Cruz, Bolivia, we studied light absorbing (chromophoric) organic or "brown" carbon (BrC) with surface and space-based remote sensing. We found that BrC has negligible absorption at visible wavelengths, but significant absorption and strong spectral dependence at UV wavelengths. Using the ground-based inversion of column effective imaginary refractive index in the range 305-368 nm, we quantified a strong spectral dependence of absorption by BrC in the UV and diminished ultraviolet B (UV-B) radiation reaching the surface. Reduced UV-B means less erythema, plant damage, and slower photolysis rates. We use a photochemical box model to show that relative to black carbon (BC) alone, the combined optical properties of BrC and BC slow the net rate of production of ozone by up to 18% and lead to reduced concentrations of radicals OH, HO 2 , and RO 2 by up to 17%, 15%, and 14%, respectively. The optical properties of BrC aerosol change in subtle ways the generally adverse effects of smoke from biomass burning.

A first summary of the Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign in the remote southeast Atlantic

NASA Astrophysics Data System (ADS)

Zuidema, P.; Adebiyi, A. A.; Aiken, A. C.; Blanchard, Y.; Castro, V.; Chiu, C.; Cunha, B.; Delgadillo, R.; Flynn, C. J.; Hardin, J. C.; Isom, B. M.; Muradyan, P.; Nitschke, K. L.; Ramajiguru, L.; Ryczek, M. R.; Sedlacek, A. J., III; Springston, S. R.; Viagas, J.; Uin, J.; Zhang, J.

2017-12-01

From June 1, 2016 through October 31, 2017, a DOE ARM Mobile Facility characterized the aerosol and cloud structure during two biomass-burning aerosol seasons to unprecedented detail over Ascension Island (14W, 8S), in the remote southeast Atlantic. The site is subject to the outflow of biomass-burning aerosol from continental Africa, over 1500 km away, from approximately July to November and is located within warm ocean waters that encourage deep boundary layers. Early findings indicate that smoke reaches the surface more often than not, at times reaching black carbon mass concentrations similar to those near fire sources on land, alternating occasionally with very clean surface conditions. The surface aerosol loading is not necessarily well-correlated with that in the free-troposphere, indicating distinct aerosol transport pathways. Aerosol layering is apparent in micropulse lidar data, with free-tropospheric aerosol, when present, typically in contact with the uppermost cloud layer. First estimates of the single-scattering-albedo, of approximately 0.85, appear to be remarkably consistent with estimates from airborne campaigns made elsewhere in the southeast Atlantic. The boundary layer is deeper when smoke is present near the surface and more well-mixed, with a stronger diurnal cycle in potential temperature indicating shortwave absorption. Cloudiness near the trade-wind inversion increases when smoke is present, while cloudiness changes at the lifting condensation level may reflect coincident meteorological changes. In summary the new observations indicate an aerosol-cloud regime that is extensive and with the potential to demonstrate unanticipated aerosol-cloud interactions.

A comparison of Solar Mesosphere Explorer and Stratosphere Aerosol and Gas Experiment II ozone densities near the stratopause

NASA Technical Reports Server (NTRS)

Rusch, D. W.; Clancy, R. T.; Mccormick, M. P.; Zawodny, J. M.

1990-01-01

Ozone measurements made by the SME UV Spectrometer and the Stratosphere Aerosol and Gas Experiment II (SAGE II) spectometer are compared at 1.0 mbar for the time period from October 1984 to December 1986, using a model of the diurnal variation of ozone to correct for the difference in local times of the two measurements. The absolute values of the ozone mixing ratio measured by the two spectrometers were found to agree to better than 5 percent, with no significant divergence between the instruments. It is concluded that, since the SAGE II data are not dependent on the absolute calibration of the instrument, these data can be used as time-dependent 'ground truth' measurements for comparisons with other instruments.

Characterization of Florida red tide aerosol and the temporal profile of aerosol concentration.

PubMed

Cheng, Yung Sung; Zhou, Yue; Pierce, Richard H; Henry, Mike; Baden, Daniel G

2010-05-01

Red tide aerosols containing aerosolized brevetoxins are produced during the red tide bloom and transported by wind to coastal areas of Florida. This study reports the characterization of Florida red tide aerosols in human volunteer studies, in which an asthma cohort spent 1h on Siesta Beach (Sarasota, Florida) during aerosolized red tide events and non-exposure periods. Aerosol concentrations, brevetoxin levels, and particle size distribution were measured. Hourly filter samples were taken and analyzed for brevetoxin and NaCl concentrations. In addition, the aerosol mass concentration was monitored in real time. The results indicated that during a non-exposure period in October 2004, no brevetoxin was detected in the water, resulting in non-detectable levels of brevetoxin in the aerosol. In March 2005, the time-averaged concentrations of brevetoxins in water samples were moderate, in the range of 5-10 microg/L, and the corresponding brevetoxin level of Florida red tide aerosol ranged between 21 and 39 ng/m(3). The temporal profiles of red tide aerosol concentration in terms of mass, NaCl, and brevetoxin were in good agreement, indicating that NaCl and brevetoxins are components of the red tide aerosol. By continuously monitoring the marine aerosol and wind direction at Siesta Beach, we observed that the marine aerosol concentration varied as the wind direction changed. The temporal profile of the Florida red tide aerosol during a sampling period could be explained generally with the variation of wind direction. Copyright 2009 Elsevier Ltd. All rights reserved.

Simulation of the Ozone Monitoring Instrument aerosol index using the NASA Goddard Earth Observing System aerosol reanalysis products

NASA Astrophysics Data System (ADS)

Colarco, Peter R.; Gassó, Santiago; Ahn, Changwoo; Buchard, Virginie; da Silva, Arlindo M.; Torres, Omar

2017-11-01

We provide an analysis of the commonly used Ozone Monitoring Instrument (OMI) aerosol index (AI) product for qualitative detection of the presence and loading of absorbing aerosols. In our analysis, simulated top-of-atmosphere (TOA) radiances are produced at the OMI footprints from a model atmosphere and aerosol profile provided by the NASA Goddard Earth Observing System (GEOS-5) Modern-Era Retrospective Analysis for Research and Applications aerosol reanalysis (MERRAero). Having established the credibility of the MERRAero simulation of the OMI AI in a previous paper we describe updates in the approach and aerosol optical property assumptions. The OMI TOA radiances are computed in cloud-free conditions from the MERRAero atmospheric state, and the AI is calculated. The simulated TOA radiances are fed to the OMI near-UV aerosol retrieval algorithms (known as OMAERUV) is compared to the MERRAero calculated AI. Two main sources of discrepancy are discussed: one pertaining to the OMI algorithm assumptions of the surface pressure, which are generally different from what the actual surface pressure of an observation is, and the other related to simplifying assumptions in the molecular atmosphere radiative transfer used in the OMI algorithms. Surface pressure assumptions lead to systematic biases in the OMAERUV AI, particularly over the oceans. Simplifications in the molecular radiative transfer lead to biases particularly in regions of topography intermediate to surface pressures of 600 and 1013.25 hPa. Generally, the errors in the OMI AI due to these considerations are less than 0.2 in magnitude, though larger errors are possible, particularly over land. We recommend that future versions of the OMI algorithms use surface pressures from readily available atmospheric analyses combined with high-spatial-resolution topographic maps and include more surface pressure nodal points in their radiative transfer lookup tables.

Quality assurance and quality control methodologies used within the Austrian UV monitoring network.

PubMed

Mario, Blumthaler

2004-01-01

The Austrian UVB monitoring network is operational since 1997. Nine detectors for measuring erythemally weighted solar UV irradiance are distributed over Austria in order to cover the main populated areas as well as different levels of altitude. The detectors are calibrated to indicate the UV-Index, the internationally agreed unit for erythemally weighted solar UV irradiance. Calibration is carried out in the laboratory for determination of spectral sensitivity of each detector, and under the sun for absolute comparison with a well-calibrated, double-monochromator spectroradiometer. For the conversion from detector-weighted units to erythemally weighted units a lookup table is used, which is calculated using a radiative transfer model and which reflects the dependence of the conversion on the solar zenith angle and total ozone content of the atmosphere. The uncertainty of the calibration is about +/-7%, dominated by the uncertainty of the calibration lamp for the spectroradiometer (+/-4%). The long-term stability of this type of detectors has been found to be not satisfactory. Therefore, routinely every year all detectors are completely recalibrated. Variations of the calibration factors up to +/-10% are found. Thus, during routine operation, several measures take place for quality control. The measured data are compared to results of model calculations with a radiative transfer model, where clear sky and an aerosol-free atmosphere are assumed. At each site, the UV data are also compared with data from a co-located pyranometer measuring total solar irradiance. These two radiation quantities are well correlated, especially on clear days and when the ozone content is taken into account. If suspicious measurements are found for one detector in the network, a well-calibrated travelling reference detector of the same type is set up side-by-side, allowing the identification of relative differences of approximately 3%. If necessary, a recalibration is carried out. As the main aim for the Austrian UV monitoring network is the information of the public about the actual levels of UVB irradiance, the measurement results are published on-line in the Internet (http://www.uibk.ac.at/projects/uv-index). For the previous day and backwards approximately 2 years, the distribution of maximal UVB levels over Austria is shown on a regional map. Additionally, near real-time data of most of the measurement stations are presented with a delay of usually less than half-an-hour. Together with these actually measured data there is also shown the diurnal variation of the maximal expected value of the UV-Index under ideal clear conditions.

Characterization of Atmospheric Organic Nitrates in Particles

NASA Astrophysics Data System (ADS)

Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

2008-12-01

Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

Aerosol optical properties over the Svalbard region of Arctic: ground-based measurements and satellite remote sensing

NASA Astrophysics Data System (ADS)

Gogoi, Mukunda M.; Babu, S. Suresh

2016-05-01

In view of the increasing anthropogenic presence and influence of aerosols in the northern polar regions, long-term continuous measurements of aerosol optical parameters have been investigated over the Svalbard region of Norwegian Arctic (Ny-Ålesund, 79°N, 12°E, 8 m ASL). This study has shown a consistent enhancement in the aerosol scattering and absorption coefficients during spring. The relative dominance of absorbing aerosols is more near the surface (lower single scattering albedo), compared to that at the higher altitude. This is indicative of the presence of local anthropogenic activities. In addition, long-range transported biomass burning aerosols (inferred from the spectral variation of absorption coefficient) also contribute significantly to the higher aerosol absorption in the Arctic spring. Aerosol optical depth (AOD) estimates from ground based Microtop sun-photometer measurements reveals that the columnar abundance of aerosols reaches the peak during spring season. Comparison of AODs between ground based and satellite remote sensing indicates that deep blue algorithm of Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals over Arctic snow surfaces overestimate the columnar AOD.

Analysis of satellite data to deduce stratospheric constituents and UV spectroscopic properties of the atmosphere

NASA Technical Reports Server (NTRS)

Mcpeters, Richard D.

1990-01-01

The objective is to better understand the stratosphere, its constituents, and its ultraviolet optical properties, through detailed analysis of data from the SBUV instrument on Nimbus 7 and comparison with data from other instruments, including the NOAA 9 SBUV 2, SAGE, SME, and SMM. One conclusion to be drawn from the Ozone Trends Panel report is that there are unresolved differences in the ozone profiles measured by different instruments. While the purpose of the work is more to understand the details of the UV radiation field in the stratosphere than it is to assess the accuracy of the SBUV ozone measurement itself, improved understanding of specific problems in the UV will lead to more accurate ozone retrievals. Areas of study include the effect of aerosols on the backscattered albedo, the shape of the ozone profile near the stratopause, the effect of possible polar mesospheric clouds, and the measureability of nitric oxide and sulfur dioxide.

Development of an Operational Multi-sensor and Multi-channel Aerosol Assimilation Package

DTIC Science & Technology

2011-08-18

2010, EGU General Assembly 2010. Shi, Y., J. Zhang, J. S. Reid, E. Hyer, Evaluation of MISR Aerosol Optical Depth Product for Aerosol Data...empirical correction procedures for generating data-assimilation-friendly over-water MODIS aerosol products. This study has been published (Shi et al...type as large r\\ values are generally related to fine mode aerosols, such as sulfate and smoke aerosols, and small r\\ values typically indicate sea

Aerosol Absorption and Radiative Forcing

NASA Technical Reports Server (NTRS)

Stier, Philip; Seinfeld, J. H.; Kinne, Stefan; Boucher, Olivier

2007-01-01

We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006) significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the shortwave anthropogenic aerosol top-of-atmosphere (TOA) radiative forcing clear-sky from -0.79 to -0.53 W m(sup -2) (33%) and all-sky from -0.47 to -0.13W m(sup -2 (72%). Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19W m(sup -2) (36%) clear-sky and of 0.12W m(sup -2) (92%) all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05W m(sup -2) and a positive TOA forcing perturbation of 0.02W m(sup -2). The long-wave aerosol radiative effects are small for anthropogenic aerosols but become of relevance for the larger natural dust and sea-salt aerosols.

Aerosol Lidar and MODIS Satellite Comparisons for Future Aerosol Loading Forecast

NASA Technical Reports Server (NTRS)

DeYoung, Russell; Szykman, James; Severance, Kurt; Chu, D. Allen; Rosen, Rebecca; Al-Saadi, Jassim

2006-01-01

Knowledge of the concentration and distribution of atmospheric aerosols using both airborne lidar and satellite instruments is a field of active research. An aircraft based aerosol lidar has been used to study the distribution of atmospheric aerosols in the California Central Valley and eastern US coast. Concurrently, satellite aerosol retrievals, from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument aboard the Terra and Aqua satellites, were take over the Central Valley. The MODIS Level 2 aerosol data product provides retrieved ambient aerosol optical properties (e.g., optical depth (AOD) and size distribution) globally over ocean and land at a spatial resolution of 10 km. The Central Valley topography was overlaid with MODIS AOD (5x5 sq km resolution) and the aerosol scattering vertical profiles from a lidar flight. Backward air parcel trajectories for the lidar data show that air from the Pacific and northern part of the Central Valley converge confining the aerosols to the lower valley region and below the mixed layer. Below an altitude of 1 km, the lidar aerosol and MODIS AOD exhibit good agreement. Both data sets indicate a high presence of aerosols near Bakersfield and the Tehachapi Mountains. These and other results to be presented indicate that the majority of the aerosols are below the mixed layer such that the MODIS AOD should correspond well with surface measurements. Lidar measurements will help interpret satellite AOD retrievals so that one day they can be used on a routine basis for prediction of boundary layer aerosol pollution events.

Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors

NASA Astrophysics Data System (ADS)

Updyke, Katelyn M.; Nguyen, Tran B.; Nizkorodov, Sergey A.

2012-12-01

Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, α-pinene, limonene, α-cedrene, α-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3 resulted in production of light-absorbing "brown carbon" compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3 oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4+ + SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3 or ammonium sulfate and high photochemical activity.

Assessment of aerosol indirect effects over Indian subcontinent using long term MODIS aerosol and cloud data

NASA Astrophysics Data System (ADS)

Das, Saurabh; Maitra, Animesh; Saha, Upal; De, Arijit

Aerosols have direct consequences on climate research and in climate change study due to its role in radiative forcing. The modulation of cloud properties due to the presence of aerosol is another important factor in understanding of the climate change scenario. However, the relationship between these two is mostly indirect as the meteorological conditions have a strong impact on the relationship. Cloud effective radius and decreases in precipitation efficiency are interlinked with the increase of aerosols. The net effect is that the cloud liquid water path and cloud lifetime increase with AOD. Though these facts are included in the global climate models (GCM), the quantitative estimation of aerosol indirect efficiency (AIE) varied widely. Some recent studies indicate an increasing trend of the aerosol optical depth over the Indian landmass. The anthropogenic activities are linked with this increase in aerosols. In general, aerosol increase can affect the cloud radius and leads to formation of non-precipitating cloud. However, the chemical composition of aerosols may also be an important factor. It is therefore necessary to have better understanding of the relationship for predicting the future climate which may be affected by such human activities. In this paper, the relation of aerosol optical depth (AOD) with cloud effective radius (CER) has been investigated over the Indian subcontinent using the long term MODIS observations. MODIS can able to provide reliable AOD information over the land surface. It also able to provide information of the cloud effective radius of the same observation point. A grid-wise correlation analysis can thus be performed to estimate the relation between AOD and CER. Result indicates both positive and negative AIE of AOD on CER. To identify the possible reason for such variability in the AIE, the role of anthropogenic aerosols and water vapor is investigated. The study on the efficiency of aerosol indirect effect indicates that a large number of grids with positive efficiency correspond to the water vapor amount of less than 2 mm whereas most of the grids have negative efficiency for water vapor amounts greater than 2 mm. Consequently, humidification of aerosols has also been examined for Indian region, which indicates that the variability in this relation may not be fully explained only by the contribution of water vapor. The role of aerosol sizes on this relation is also estimated by differentiating between fine mode and coarse mode aerosol. The presence of fine mode aerosols as estimated by model simulation and satellite observations show that the combined effect of water vapor and aerosol size can explain the observed positive and negative AIE more effectively. The results have important consequences on the GCM by incorporating the AIE more precisely.

Development, evaluation and comparison of two independent sampling and analytical methods for ortho-phthalaldehyde vapors and condensation aerosols in air† ‡

PubMed Central

2015-01-01

Two independent sampling and analytical methods for ortho-phthalaldehyde (OPA) in air have been developed, evaluated and compared (1) a reagent-coated solid sorbent HPLC-UV method and (2) an impinger-fluorescence method. In the first method, air sampling is conducted at 1.0 L min−1 with a sampler containing 350 mg of silica gel coated with 1 mg of acidified 2,4-dinitrophenylhydrazine (DNPH). After sampling, excess DNPH in ethyl acetate is added to the sampler prior to storage for 68 hours. The OPA-DNPH derivative is eluted with 4.0 mL of dimethyl sulfoxide (DMSO) for measurement by HPLC with a UV detector set at 3S5 nm. The estimated detection limit is 0.016 µg per sample or 0.067 µg m−3 (0.012 ppb) for a 240 L air sample. Recoveries of vapor spikes at levels of 1.2 to 6.2 µg were 96 to 101%. Recoveries of spikes as mixtures of vapor and condensation aerosols were 97 to 100%. In the second method, air sampling is conducted at 1.0 L mm−1 with a midget impinger containing 10 mL of DMSO solution containing N-acetyl-l-cysteine and ethylenediamine. The fluorescence reading is taken 80 min after the completion of air sampling. Since the time of taking the fluorescence reading is critical, the reading is taken with a portable fluorometer. The estimated detection limit is 0.024 µg per sample or 0.1 µg m−3 (0.018 ppb) for a 240 L air sample. Recoveries of OPA vapor spikes at levels of 1.4 to 5.0 µg per sample were 97 to 105%. Recoveries of spikes as mixtures of vapors and condensation aerosols were 95 to 99%. The collection efficiency for a mixture of vapor and condensation aerosol was 99.4%. The two methods were compared side-by-side in a generation system constructed for producing controlled atmospheres of OPA vapor in air. Average air concentrations of OPA vapor found by both methods agreed within ±10%. PMID:26346658

Interannual Variability of Water Ice Clouds at Gale Crater

NASA Astrophysics Data System (ADS)

Martinez, G.; Giuranna, M.; McConnochie, T. H.; Tamppari, L.; Smith, M. D.; Vicente-Retortillo, Á.; Renno, N. O.; Kloos, J. L.; Moores, J. E.; Guzewich, S.

2017-12-01

The Aphelion Cloud Belt (ACB) is a water ice cloud band that encircles the planet longitudinally at latitudes ranging from about 10°S to 30°N during the northern spring and summer (aphelion season). The ACB has been studied extensively using satellite observations over the last two decades [1], showing little interannual variability from MY 24 to 34. The Mars Science Laboratory (MSL) mission has completed more than 1750 sols of measurements at Gale crater (4.5°S), from Ls 155° in MY 31 to Ls 33° in MY 34. Interestingly, MSL results from various instruments indicate that the ACB produces significant interannual variability at Gale crater during the aphelion season. In particular, near-noon retrievals of water ice opacity by the ChemCam instrument indicate an increase in water ice opacity up to 50% from MY 32 to 33 [2], further supported by analysis of UV [3] and ground temperature [4] data taken by the Rover Environmental Monitoring Station during MY 32 and 33. A weaker ( 5%) increase in water ice opacity in MY 33 relative to MY 32 was also observed from images taken during afternoon hours by the rover's Navigation Cameras [5]. We are analyzing simultaneous and noncontemporary satellite observations at the location of Gale made by the Planetary Fourier Spectrometer [6], Mars Climate Sounder, Thermal Emission Imaging System and Thermal Emission Spectrometer to shed light on the nature of the interannual variability of the ACB at Gale, and to locally understand the relation between the ACB and the water cycle. References:[1] Smith, M.D. (2008), Spacecraft observations of the martian atmosphere, Annu. Rev. Earth Planet. Sci. 36. [2] McConnochie, T. H., et al. (2017), Retrieval of Water Vapor Column Abundance and Aerosol Properties from ChemCam Passive Sky Spectroscopy, Icarus (submitted). [3] Vicente-Retortillo, Á., et al. (2017), Determination of dust aerosol particle size at Gale Crater using REMS UVS and Mastcam measurements, GRL, 44. [4] Vasavada, A.R. et al. (2017), Thermophysical properties along Curiosity's traverse in Gale crater, Mars, Icarus 284. [5] Kloos, J. L., and J. E. Moores (2017), Inter-Annual and Diurnal Variability in Clouds Observed from MSL Over Two Martian Years, LPSC, 48. [6] Giuranna, M. et al. (2016), 12 years of atmospheric monitoring by the Planetary Fourier Spectrometer onboard Mars Express, EGU.

UV lifetime laser demonstrator for space-based applications

NASA Astrophysics Data System (ADS)

Albert, Michael; Puffenburger, Kent; Schum, Tom; Fitzpatrick, Fran; Litvinovitch, Slava; Jones, Darrell; Rudd, Joseph; Hovis, Floyd

2015-09-01

A long-lived UV laser is an enabling technology for a number of high-priority, space-based lidar instruments. These include next generation cloud and aerosol lidars that incorporates a UV channel, direct detection 3-D wind lidars, and ozone DIAL (differential absorption lidar) system. In previous SBIR funded work we developed techniques for increasing the survivability of components in high power UV lasers and demonstrated improved operational lifetimes. In this Phase III ESTO funded effort we are designing and building a TRL (Technology Readiness Level) 6 demonstrator that will have increased output power and a space-qualifiable package that is mechanically robust and thermally-stable. For full space compatibility, thermal control will be through pure conductive cooling. Contamination control processes and optical coatings will be chosen that are compatible with lifetimes in excess of 1 billion shots. The 1064nm output will be frequency tripled to provide greater than 100mJ pulses of 355nm light at 150 Hz. After completing the laser module build in the third quarter of 2015 we will initiate lifetime testing, followed by thermal/vacuum (TVAC) and vibration testing to demonstrate that the design is at TRL 6.

Sensitivity of erythemal UV/global irradiance ratios to atmospheric parameters: application for estimating erythemal radiation at four sites in Thailand

NASA Astrophysics Data System (ADS)

Buntoung, Sumaman; Janjai, Serm; Nunez, Manuel; Choosri, Pranomkorn; Pratummasoot, Noppamas; Chiwpreecha, Kulanist

2014-11-01

Factors affecting the ratio of erythemal UV (UVER) to broadband (G) irradiance were investigated in this study. Data from four solar monitoring sites in Thailand, namely Chiang Mai, Ubon Ratchathani, Nakhon Pathom and Songkhla were used to investigate the UVER/G ratio in response to geometric and atmospheric parameters. These comprised solar zenith angle, aerosol load, total ozone column, precipitable water and clearness index. A modeling scheme was developed to isolate and examine the effect of each individual environmental parameter on the ratio. Results showed that all parameters with the exception of solar zenith angle and clearness index influenced the ratios in a linear manner. These results were also used to develop a semi-empirical model for estimating hourly erythemal UV irradiance. Data from 2009 to 2010 were used to construct the ratio model while validation was performed using erythemal UV irradiance at the above four sites in 2011. The validation results showed reasonable agreement with a root mean square difference of 13.5% and mean bias difference of - 0.5%, under all sky conditions and 10.9% and - 0.3%, respectively, under cloudless conditions.

Interaction between morin and AOT reversed micelles--studies with UV-vis at 25 °C.

PubMed

Bhattarai, Ajaya; Wilczura-Wachnik, H

2014-01-30

The precise measurements of morin absorbance in presence of surfactant/solvent/water systems at 25 °C by UV-vis technique are reported. The surfactant used in presented study was sodium bis(2-ethylhexyl) sulfosuccinate called Aerosol-OT or AOT. The solvents selected were: ethanol, ethylene glycol, and n-decanol. The concentrations of AOT were varied between 0.001 and 0.4 mol/kg. Morin concentration in quvette during UV-vis registration was not equals in all solvent because of its different solubility and absorption intensity depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=[H2O]/[AOT] and was equal 0, 30 and 40 in ethanol; 0, 10, 20 and 30 in ethylene glycol and 0, 10, 20, 30, and 40 in n-decanol. In presented work a Nernstian distribution of morin between the organic and micellar phases was assumed. The intensity of morin absorbance as a function of AOT concentration was analyzed. Using Non-linear Regression Procedure (NLREG) morin binding constant (K' [mol/kg]), and morin distribution constant (K) between organic phase and AOT micellar phase have been calculated. The experimental results have shown a significant influence of solvent, surfactant and water presence on morin UV-vis spectrum. Calculated data pointed out on different transfer of morin molecules from the organic to micellar phase depending on the solvent. Moreover, results of calculations indicate on competition between morin and water molecules interacting with AOT polar heads. Morin molecules privileged location in AOT reversed micelles strongly depends on the solvent. In case of systems with ethylene glycol as solvent is possible morin molecules location in polar cores of AOT reversed micelles as results of strong interaction between AOT polar heads and morin hydroxyl groups, whereas in case of ethanol and n-decanol morin molecules are located in palisade layer. Copyright © 2013 Elsevier B.V. All rights reserved.

Atmospheric aerosols size distribution properties in winter and pre-monsoon over western Indian Thar Desert location

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panwar, Chhagan, E-mail: chhaganpanwar@gmail.com; Vyas, B. M.

The first ever experimental results over Indian Thar Desert region concerning to height integrated aerosols size distribution function in particles size ranging between 0.09 to 2 µm such as, aerosols columnar size distribution (CSD), effective radius (R{sub eff}), integrated content of total aerosols (N{sub t}), columnar content of accumulation and coarse size aerosols particles concentration (N{sub a}) (size < 0.5 µm) and (N{sub c}) (size between 0.5 to 2 µm) have been described specifically during winter (a stable weather condition and intense anthropogenic pollution activity period) and pre-monsoon (intense dust storms of natural mineral aerosols as well as unstable atmospheric weather condition period)more » at Jaisalmer (26.90°N, 69.90°E, 220 m above surface level (asl)) located in central Thar desert vicinity of western Indian site. The CSD and various derived other aerosols size parameters are retrieved from their average spectral characteristics of Aerosol Optical Thickness (AOT) from UV to Infrared wavelength spectrum measured from Multi-Wavelength solar Radiometer (MWR). The natures of CSD are, in general, bio-modal character, instead of uniformly distributed character and power law distributions. The observed primary peaks in CSD plots are seen around about 10{sup 13} m{sup 2} μm{sup −1} at radius range 0.09-0.20 µm during both the seasons. But, in winter months, secondary peaks of relatively lower CSD values of 10{sup 10} to 10{sup 11} m{sup 2}/μm{sup −1} occur within a lower radius size range 0.4 to 0.6 µm. In contrast to this, while in dust dominated and hot season, the dominated secondary maxima of the higher CSD of about 10{sup 12} m{sup 2}μm{sup −3} is found of bigger aerosols size particles in a rage of 0.6 to 1.0 µm which is clearly demonstrating the characteristics of higher aerosols laden of bigger size aerosols in summer months relative to their prevailed lower aerosols loading of smaller size aerosols particles (0.4 to 0.6 µm) in cold months. Several other interesting features of changing nature of monthly spectral AOT, R{sub eff}, N{sub t}, N{sub a} and N{sub C} (particles/m{sup 2}) have been discussed in detail in this paper.« less

Global and Seasonal Aerosol Optical Depths Derived From Ultraviolet Observations by Satellites (TOMS)

NASA Technical Reports Server (NTRS)

Herman, J. R.; Torres, O.

1999-01-01

It has been shown that absorbing aerosols (dust, smoke, volcanic ash) can be detected in the ultraviolet wavelengths (331 nm to 380 nm) from satellite observations (TOMS, Total Ozone Mapping Spectrometer) over both land and water. The theoretical basis for these observations and their conversions to optical depths is discussed in terms of an aerosol index AI or N-value residue (assigned positive for absorbing aerosols). The theoretical considerations show that negative values of the AI frequently represent the presence of non-absorbing aerosols (NA) in the troposphere (mostly pollution in the form of sulfates, hydrocarbons, etc., and some natural sulfate aerosols) with particle sizes near 0.1 to 0.2 microns or less. The detection of small-particle non-absorbing aerosols from the measured backscattered radiances is based on the observed wavelength dependence from Mie scattering after the background Rayleigh scattering is subtracted. The Mie scattering from larger particles, 1 micron or more (e.g., cloud water droplets) has too small a wavelength dependence to be detected by this method. In regions that are mostly cloud free, aerosols of all sizes can be seen in the single channel 380 nm or 360 nm radiance data. The most prominent Al feature observed is the strong asymmetry in aerosol amount between the Northern and Southern Hemispheres, with the large majority of NA occurring above 20degN latitude. The maximum values of non-absorbing aerosols are observed over the eastern U.S. and most of western Europe corresponding to the areas of highest industrial pollution. Annual cycles in the amount of NA are observed over Europe and North America with maxima occurring in the summer corresponding to times of minimum wind transport. Similarly, the maxima in the winter over the Atlantic Ocean occurs because of wind borne transport from the land. Most regions of the world have the maximum amount of non-absorbing aerosol in the December to January period except for the eastern North America and Europe. Comparisons of the estimated TOMS aerosol optical depths show good agreement in magnitude and seasonal dependence with sun-photometer optical depths obtained at Goddard Space Flight Center (39degN 76.88degW) in the U.S. and in Lille (50.63degN 3.07degE) in France. The study of these aerosols is important for detecting the sources of industrial pollution and its redistribution by winds on a global basis, as well as its effect on reducing the UV irradiance at the Earth's surface.

Modeling Optical and Radiative Properties of Clouds Constrained with CARDEX Observations

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Praveen, P. S.; Ramanathan, V.

2013-12-01

Carbonaceous aerosols (CA) have important effects on climate by directly absorbing solar radiation and indirectly changing cloud properties. These particles tend to be a complex mixture of graphitic carbon and organic compounds. The graphitic component, called as elemental carbon (EC), is characterized by significant absorption of solar radiation. Recent studies showed that organic carbon (OC) aerosols absorb strongly near UV region, and this faction is known as Brown Carbon (BrC). The indirect effect of CA can occur in two ways, first by changing the thermal structure of the atmosphere which further affects dynamical processes governing cloud life cycle; secondly, by acting as cloud condensation nuclei (CCN) that can change cloud radiative properties. In this work, cloud optical properties have been numerically estimated by accounting for CAEDEX (Cloud Aerosol Radiative Forcing Dynamics Experiment) observed cloud parameters and the physico-chemical and optical properties of aerosols. The aerosol inclusions in the cloud drop have been considered as core shell structure with core as EC and shell comprising of ammonium sulfate, ammonium nitrate, sea salt and organic carbon (organic acids, OA and brown carbon, BrC). The EC/OC ratio of the inclusion particles have been constrained based on observations. Moderate and heavy pollution events have been decided based on the aerosol number and BC concentration. Cloud drop's co-albedo at 550nm was found nearly identical for pure EC sphere inclusions and core-shell inclusions with all non-absorbing organics in the shell. However, co-albedo was found to increase for the drop having all BrC in the shell. The co-albedo of a cloud drop was found to be the maximum for all aerosol present as interstitial compare to 50% and 0% inclusions existing as interstitial aerosols. The co-albedo was found to be ~ 9.87e-4 for the drop with 100% inclusions existing as interstitial aerosols externally mixed with micron size mineral dust with 2% hematite content. The cloud spectral optical properties and the radiative properties for the aforesaid cases during CARDEX observations will be discussed in detail.

Measurements of Primary Biogenic Aerosol Particles with an Ultraviolet Aerodynamic Particle Sizer (UVAPS) During AMAZE-08

NASA Astrophysics Data System (ADS)

Wollny, A. G.; Garland, R.; Pöschl, U.

2008-12-01

Biogenic aerosols are ubiquitous in the Earth's atmosphere and they influence atmospheric chemistry and physics, the biosphere, climate, and public health. They play an important role in the spread of biological organisms and reproductive materials, and they can cause or enhance human, animal, and plant diseases. Moreover, they influence the Earth's energy budget by scattering and absorbing radiation, and they can initiate the formation of clouds and precipitation as cloud condensation and ice nuclei. The composition, abundance, and origin of biogenic aerosol particles and components are, however, still not well understood and poorly quantified. Prominent examples of primary biogenic aerosol particles, which are directly emitted from the biosphere to the atmosphere, are pollen, bacteria, fungal spores, viruses, and fragments of animals and plants. During the AMazonian Aerosol CharacteriZation Experiment (AMAZE-08) a large number of aerosol and gas-phase measurements were taken on a remote site close to Manaus, Brazil, during a period of five weeks in February and March 2008. The presented study is focused on data from an ultraviolet aerodynamic particle sizer (UVAPS, TSI inc.) that has been deployed for the first time in Amazonia. In this instrument, particle counting and aerodynamic sizing over the range of 0.5-20 μm are complemented by the measurement of UV fluorescence at 355 nm (excitation) and 420-575 nm (emission), respectively. Fluorescence at these wavelengths is characteristic for reduced pyridine nucleotides (e.g., NAD(P)H) and for riboflavin, which are specific for living cells. Thus particles exhibiting fluorescence signals can be regarded as 'viable aerosols' or 'fluorescent bioparticles' (FBAP), and their concentration can be considered as lower limit for the actual abundance of primary biogenic aerosol particles. First data analyses show a pronounced peak of FBAP at diameters around 2-3 μm. In this size range the biogenic particle fraction was generally higher than 50 %. Additionally, bursts of FBAP have been observed nearly every day just before sunrise. During these periods the coarse (super-micron) aerosol consisted almost completely of fluorescent bioparticles.

Time Resolved Measurements of Primary Biogenic Aerosol Particles in Amazonia

NASA Astrophysics Data System (ADS)

Wollny, A. G.; Garland, R.; Pöschl, U.

2009-04-01

Biogenic aerosols are ubiquitous in the Earth's atmosphere and they influence atmospheric chemistry and physics, the biosphere, climate, and public health. They play an important role in the spread of biological organisms and reproductive materials, and they can cause or enhance human, animal, and plant diseases. Moreover, they influence the Earth's energy budget by scattering and absorbing radiation, and they can initiate the formation of clouds and precipitation as cloud condensation and ice nuclei. The composition, abundance, and origin of biogenic aerosol particles and components are, however, still not well understood and poorly quantified. Prominent examples of primary biogenic aerosol particles, which are directly emitted from the biosphere to the atmosphere, are pollen, bacteria, fungal spores, viruses, and fragments of animals and plants. During the Amazonian Aerosol Characterization Experiment (AMAZE-08) a large number of aerosol and gas-phase measurements were taken on a remote site close to Manaus, Brazil, during a period of five weeks in February and March 2008. This presented study is focused on data from an ultraviolet aerodynamic particle sizer (UVAPS, TSI inc.) that has been deployed for the first time in Amazonia. In this instrument, particle counting and aerodynamic sizing over the range of 0.5-20 µm are complemented by the measurement of UV fluorescence at 355 nm (excitation) and 420-575 nm (emission), respectively. Fluorescence at these wavelengths is characteristic for reduced pyridine nucleotides (e.g., NAD(P)H) and for riboflavin, which are specific for living cells. Thus particles exhibiting fluorescence signals can be regarded as "viable aerosols" or "fluorescent bioparticles" (FBAP), and their concentration can be considered as lower limit for the actual abundance of primary biogenic aerosol particles. Data from the UVAPS were averaged over 5 minute time intervals. The presence of bioparticles in the observed size range has been confirmed by filter samples. First data analyses show a pronounced peak of FBAP at diameters around 2-3 µm. In this size range the biogenic particle fraction was generally higher than 50%. Additionally, bursts of FBAP have been observed nearly every day just before sunrise. During these periods the coarse (super-micron) aerosol consisted almost completely out of fluorescent bioparticles.

Carbonaceous Aerosol Characterization during 2016 KOR-US 2016

NASA Astrophysics Data System (ADS)

Rodriguez, B.; Santos, G. M.; Sanchez, D.; Jeong, D.; Czimczik, C. I.; Kim, S.

2017-12-01

Atmospheric carbonaceous aerosols are a major component of fine particulate matter and assume important roles in Earth's climate and human health. Because atmospheric carbonaceous aerosols exist as a continuum ranging from small, light-scattering organic carbon (OC), to highly-condensed, light-absorbing elemental carbon (EC) they have contrasting effects on interaction with incoming and outgoing radiation, cloud formation, and snow/ice albedo. By strengthening our understanding of the relative contribution and sources of OC and EC we will be able to further describe aerosol formation and mixing at the regional level. To understand the relative anthropogenic and biogenic contributions to carbonaceous aerosol, 12 PM10 aerosols samples were collected on quartz fiber filters at the Mt. Taewha Research Forest in South Korea during the KORUS-AQ 2016 campaign over periods of 24-48 hours with a high-volume air sampler. Analysis of bulk C and N concentrations and absorption properties of filter extracts interspersed with HYSPLIT model results indicated that continental outflow across the Yellow Sea in enriched in bulk nitrogen loading and enhanced bulk absorptive properties of the aerosols. Bulk radiocarbon analysis also indicated enriched values in all samples indicating contamination from a nuclear power plant or the combustion of biomedical waste nearby. Here, we aim to investigate further the chemical characterization of VOCs adsorbed unto the aerosol through TD-GC-TOFMS. With this dataset we aim to determine the relative contribution of anthropogenic and biogenic aerosols by utilizing specific chemical tracers for source apportionment.

The Angstrom Exponent and Bimodal Aerosol Size Distributions

NASA Technical Reports Server (NTRS)

Schuster, Gregory L.; Dubovik, Oleg; Holben, Brent H.

2005-01-01

Powerlaws have long been used to describe the spectral dependence of aerosol extinction, and the wavelength exponent of the aerosol extinction powerlaw is commonly referred to as the Angstrom exponent. The Angstrom exponent is often used as a qualitative indicator of aerosol particle size, with values greater than two indicating small particles associated with combustion byproducts, and values less than one indicating large particles like sea salt and dust. In this study, we investigate the relationship between the Angstrom exponent and the mode parameters of bimodal aerosol size distributions using Mie theory calculations and Aerosol Robotic Network (AERONET) retrievals. We find that Angstrom exponents based upon seven wavelengths (0.34, 0.38, 0.44, 0.5, 0.67, 0.87, and 1.02 micrometers) are sensitive to the volume fraction of aerosols with radii less then 0.6 micrometers, but not to the fine mode effective radius. The Angstrom exponent is also known to vary with wavelength, which is commonly referred to as curvature; we show how the spectral curvature can provide additional information about aerosol size distributions for intermediate values of the Angstrom exponent. Curvature also has a significant effect on the conclusions that can be drawn about two-wavelength Angstrom exponents; long wavelengths (0.67, 0.87 micrometers) are sensitive to fine mode volume fraction of aerosols but not fine mode effective radius, while short wavelengths (0.38, 0.44 micrometers) are sensitive to the fine mode effective radius but not the fine mode volume fraction.

Quantifying VOC-Reaction Tracers, Ozone Production, and Continuing Aerosol Production Rates in Urban and Far-Downwind Atmospheres

NASA Technical Reports Server (NTRS)

Chatfield, Robert; Ren, X.; Brune, W.; Fried, A.; Schwab, J.

2008-01-01

We have found a surprisingly informative decomposition of the complex question of smoggy ozone production (basically, [HO2] in a more locally determined field of [NO]) in the process of linked investigations of modestly smoggy Eastern North America (by NASA aircraft, July 2004) and rather polluted Flushing, NYC (Queens College, July, 2001). In both rural and very polluted situations, we find that a simple contour graph parameterization of the local principal ozone production rate can be estimated using only the variables [NO] and j(sub rads) [HCHO]: Po(O3) = c (j(sub rads) [HCHO])(sup a) [HCHO](sup b). Here j(sub rads) is the photolysis of HCHO to radicals, presumably capturing many harder-UV photolytic processes and the principle ozone production is that due to HO2; mechanisms suggest that ozone production due to RO2 is closely correlated, often suggesting a limited range of different proportionality factors. The method immediately suggests a local interpretation for concepts of VOC limitation and NOx limitation. We believe that the product j(sub rads) [HCHO] guages the oxidation rate of observed VOC mixtures in a way that also provides [HO2] useful for the principle ozone production rate k [HO2] [NO], and indeed, all ozone chemical production. The success of the method suggests that dominant urban primary-HCHO sources may transition to secondary plume-HCHO sources in a convenient way. Are there other, simple, near-terminal oxidized VOC's which help guage ozone production and aerosol particle formation? Regarding particles, we report on, to the extent NASA Research resources allow, on appealing relationships between far-downwind (Atlantic PBL) HCHO and very fine aerosol (including sulfate. Since j(sub rads) [HCHO] provides a time-scale, we may understand distant-plume particle production in a more quantitative manner. Additionally we report on a statistical search in the nearer field for relationships between glyoxals (important near-terminal aromatic and isoprene reaction products) and aerosol production, looking for VOC's that might be most implicated. All three variables j(sub rads), [HCHO], and [NO] are relatively easily measured in widespread air pollution monitoring networks, and all are deducible form space-borne observations, though estimation of [NO] from [NO2] (the species observable from space) may require care. We report also on airborne and surface observations of HCHO, suggesting that concentrated (urban) and more diffuse (forest) sources may be distinguishable from space. The use of the 3.58 micron microwindow for HCHO remote sensing should allow much sharper resolution of HCHO than the UV. UV sensing requires large and expensive instruments, but even these seem justified since formaldehyde is so informative.

Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

NASA Astrophysics Data System (ADS)

Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

2015-01-01

To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic aerosols (BA), for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2) and malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment, except for ω-oxooctanoic acid (ωC8) that showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids dominates their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

NASA Astrophysics Data System (ADS)

Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

2015-07-01

To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic (BA) aerosols, for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2), malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols, whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment except for ω-oxooctanoic acid (ωC8), which showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids controls their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

Chemical composition and characteristics of ambient aerosols and rainwater residues during Indian summer monsoon: Insight from aerosol mass spectrometry

NASA Astrophysics Data System (ADS)

Chakraborty, Abhishek; Gupta, Tarun; Tripathi, Sachchida N.

2016-07-01

Real time composition of non-refractory submicron aerosol (NR-PM1) is measured via Aerosol mass spectrometer (AMS) for the first time during Indian summer monsoon at Kanpur, a polluted urban location located at the heart of Indo Gangetic Plain (IGP). Submicron aerosols are found to be dominated by organics followed by nitrate. Source apportionment of organic aerosols (OA) via positive matrix factorization (PMF) revealed several types of secondary/oxidized and primary organic aerosols. On average, OA are completely dominated by oxidized OA with a very little contribution from biomass burning OA. During rain events, PM1 concentration is decreased almost by 60%, but its composition remains nearly the same. Oxidized OA showed slightly more decrease than primary OAs, probably due to their higher hygroscopicity. The presence of organo nitrates (ON) is also detected in ambient aerosols. Apart from real-time sampling, collected fog and rainwater samples were also analyzed via AMS in offline mode and in the ICP-OES (Inductively coupled plasma - Optical emission spectrometry) for elements. The presence of sea salt, organo nitrates and sulfates has been observed. Rainwater residues are also dominated by organics but their O/C ratios are 15-20% lower than the observed values for ambient OA. Alkali metals such as Ca, Na, K are found to be most abundant in the rainwater followed by Zn. Rainwater residues are also found to be much less oxidized than the aerosols present inside the fog water, indicating presence of less oxidized organics. These findings indicate that rain can act as an effective scavenger of different types of pollutants even for submicron particle range. Rainwater residues also contain organo sulfates which indicate that some portion of the dissolved aerosols has undergone aqueous processing, possibly inside the cloud. Highly oxidized and possibly hygroscopic OA during monsoon period compared to other seasons (winter, post monsoon), indicates that they can act more efficiently as cloud condensation nuclei.

UV lifetime demonstrator for space-based applications

NASA Astrophysics Data System (ADS)

Albert, Michael; Puffenburger, Kent; Schum, Tom; Fitzpatrick, Fran; Litvinovitch, Slava; Jones, Darrell; Rudd, Joseph; Hovis, Floyd

2016-05-01

A long-lived UV laser is an enabling technology for a number of high-priority, space-based lidar instruments. These include next generation cloud and aerosol lidars that incorporates a UV channel, direct detection 3-D wind lidars, and ozone DIAL (differential absorption lidar) systems. In previous SBIR funded work we developed techniques for increasing the survivability of components in high power UV lasers and demonstrated improved operational lifetimes. In this Phase III ESTO funded effort we are designing and building a TRL (Technology Readiness Level) 6 demonstrator that will have increased output power and a space-qualifiable package that is mechanically robust and thermally-stable. For full space compatibility, thermal control will be through pure conductive cooling. Contamination control processes and optical coatings will be chosen that are compatible with lifetimes in excess of 1 billion shots. The 1064nm output will be frequency tripled to provide greater than 100 mJ pulses of 355 nm light at 150 Hz. The laser module build was completed in the third quarter of 2015 at which time a series of life tests were initiated. The first phase of the lifetime testing is a 532 nm only test that is expected to complete in April 2016. The 532 nm lifetest will be followed by a 4 month half power UV life test and then a four month full power UV life test. The lifetime tests will be followed by thermal/vacuum (TVAC) and vibration testing to demonstrate that the laser optics module design is at TRL 6.

Response of Cloud Condensation Nuclei (> 50 nm) to changes in ion-nucleation

NASA Astrophysics Data System (ADS)

Pedersen, J. O.; Enghoff, M. B.; Svensmark, H.

2012-12-01

The role of ionization in the formation of clouds and aerosols has been debated for many years. A body of evidence exists that correlates cloud properties to galactic cosmic ray ionization; however these results are still contested. In recent years experimental evidence has also been produced showing that ionization can promote the nucleation of small aerosols at atmospheric conditions. The experiments showed that an increase in ionization leads to an increase in the formation of ultrafine aerosols (~3 nm), but in the real atmosphere such small particles have to grow by coagulation and condensation to become cloud condensation nuclei (CCN) in order to have an effect on clouds. However, numerical studies predict that variations in the count of ultra-fine aerosols will lead only to an insignificant change in the count of CCN. This is due to 1) the competition between the additional ultra-fine aerosols for the limited supply of condensable gases leading to a slower growth and 2) the increased loss rates of the additional particles during the longer growth-time. We investigated the growth of aerosols to CCN sizes using an 8 m3 reaction chamber made from electro-polished stainless steel. One side was fitted with a Teflon foil to allow ultraviolet light to illuminate the chamber, which was continuously flushed with dry purified air. Variable concentrations of water vapor, ozone, and sulfur dioxide could be added to the chamber. UV-lamps initiated photochemistry producing sulfuric acid. Ionization could be enhanced with two Cs-137 gamma sources (30 MBq), mounted on each side of the chamber. Figure 1 shows the evolution of the aerosols, following a nucleation event induced by the gamma sources. Previous to the event the aerosols were in steady state. Each curve represents a size bin: 3-10 nm (dark purple), 10-20 nm (purple), 20-30 nm (blue), 30-40 nm (light blue), 40-50 nm (green), 50-60 nm (yellow), and 60-68 nm (red). Black curves show a ~1 hour smoothing. The initial increase in small aerosols persists all the way to the largest size bin. Similar experiments where the aerosol burst was produced with either the ionization source or an aerosol generator (neutralized aerosols) were made and compared with each other and model runs. The runs using neutral aerosol bursts agree with the model predictions, where the initial burst is dampened such that there is little or no change in the largest sizes. Thus there seems to be a fundamental difference between the bursts produced by ionization and those produced by the aerosol generator. Growth of aerosols, nucleated by ionization.

Multiphoton tomography to detect chemo- and biohazards

NASA Astrophysics Data System (ADS)

König, Karsten

2015-03-01

In vivo high-resolution multiphoton/CARS tomography provides optical biopsies with 300 nm lateral resolution with chemical fingerprints. Thousands of volunteers and patients have been investigated for early cancer diagnosis, evaluation of anti-ageing cosmetic products, and changes of cellular metabolism by UV exposure and decreased oxygen supply. The skin as the outermost and largest organ is also the major target of CB agents. Current UV-based sensors are useful for bio-aerosol sensing but not for evaluating exposed in vivo skin. Here we evaluate the use of 4D multiphoton/CARS tomographs based on near infrared femtosecond laser radiation, time-correlated single photon counting (FLIM) and white light generation by photonic crystal fibers to detect bio- and chemohazards in human in vivo skin using twophoton fluorescence, SHG, and Raman signals.

Isolation and characterization of ultraviolet light-sensitive mutants of the blue-green alga Anacystis nidulans.

NASA Technical Reports Server (NTRS)

Asato, Y.

1972-01-01

Three independently isolated ultraviolet light sensitive (uvs) mutants of Anacystis nidulans were characterized. Strain uvs-1 showed the highest sensitivity to UV by its greatly reduced photoreactivation capacity following irradiation. Pretreatment with caffeine suppressed the dark-survival curve of strain uvs-1, thus indicating the presence of excision enzymes involved in dark repair. Under 'black' and 'white' illumination, strain uvs-1 shows photorecovery properties comparable with wild-type cultures. Results indicate that strains uvs-1, uvs-35, and uvs-88 are probably genetically distinct UV-sensitive mutants.

Synergism of Saturn, Enceladus and Titan and Formation of HCNO Prebiotic Molecules

NASA Technical Reports Server (NTRS)

Sittler, Edward C.; Cooper, John F.

2011-01-01

Saturn as a system has two very exotic moons Titan and Enceladus. Titan, taking in energy from Saturn's magnetosphere, solar UV irradiation, and cosmic rays, can make HCN based molecules as discussed in earlier paper by Raulin and Owen. Space radiation effects at both moons, and as coupled by the Saturn magnetosphere, could cause an unexpected series of events potentially leading to prebiotic chemical evolution at Titan with HCNO from magnetospheric oxygen as the new ingredient. The "Old Faithful" model suggests that Enceladus, highly irradiated by Saturn magnetospheric electrons and thus having a source of chemical energy from radiolytic gas production, has episodic ejections of water vapor, carbon dioxide, and various hydrocarbons into Saturn's magnetosphere. The hydrocarbons do not survive transport through the plasma environment, but oxygen ions from Enceladus water molecules become the dominant ion species in the outer magnetosphere. At Titan, Cassini discovered that 1) keV oxygen ions, evidently from Enceladus, are bombarding Titan's upper atmosphere and 2) heavy positive and negative ions exist in significant abundances within Titan's upper atmosphere. Initial models of heavy ion formation in Titan's upper atmosphere invoked polymerization of aromatics such as benzenes and their radicals to make polycyclic aromatic hydrocarbons (PAH) , while a more recent model by Sittler et al., has raised the possibility of carbon chains forming from the polymerization of acetylene and its radicals to make fullerenes. Laboratory measurements indicate that fullerenes, which are hollow carbon shells, can trap keV oxygen ions. Clustering of the fullerenes with aerosol mixtures from PAHs and the dominant nitrogen molecules could form larger aerosols enriched in trapped oxygen. Aerosol precipitation could then convey these chemically complex structures deeper into the atmosphere and to the moon surface. Ionizing solar UV, magnetospheric electron, and galactic cosmic ray irradiation would provide further energy for processing into more complex organic forms. Further ionizing irradiation from cosmic rays deep in the atmosphere "tho lin" molecules are produced with all the molecular components present from which prebiotic organic molecules can form. This synergy of Saturn system, exogenic irradiation, and molecular processes provides a potential pathway for accumulation of prebiotic chemistry on the surface of Titan. Since fullerenes are also thought to exist in interstellar space, similar processes may also occur there to seed molecular clouds with prebiotic chemical species. We will also discuss possible future laboratory experiments that could be done to investigate fullerene formation at Titan and the trapping of oxygen in fullerenes.

Sensitivity of atmospheric aerosol scavenging to precipitation intensity and frequency in the context of global climate change

NASA Astrophysics Data System (ADS)

Hou, Pei; Wu, Shiliang; McCarty, Jessica L.; Gao, Yang

2018-06-01

Wet deposition driven by precipitation is an important sink for atmospheric aerosols and soluble gases. We investigate the sensitivity of atmospheric aerosol lifetimes to precipitation intensity and frequency in the context of global climate change. Our sensitivity model simulations, through some simplified perturbations to precipitation in the GEOS-Chem model, show that the removal efficiency and hence the atmospheric lifetime of aerosols have significantly higher sensitivities to precipitation frequencies than to precipitation intensities, indicating that the same amount of precipitation may lead to different removal efficiencies of atmospheric aerosols. Combining the long-term trends of precipitation patterns for various regions with the sensitivities of atmospheric aerosol lifetimes to various precipitation characteristics allows us to examine the potential impacts of precipitation changes on atmospheric aerosols. Analyses based on an observational dataset show that precipitation frequencies in some regions have decreased in the past 14 years, which might increase the atmospheric aerosol lifetimes in those regions. Similar analyses based on multiple reanalysis meteorological datasets indicate that the changes of precipitation intensity and frequency over the past 30 years can lead to perturbations in the atmospheric aerosol lifetimes by 10 % or higher at the regional scale.

The Cretaceous-Tertiary extinction: A lethal mechanism involving anhydrite target rocks

USGS Publications Warehouse

Brett, R.

1992-01-01

The Chicxulub Crater, Yucatan, Mexico, is a leading contender as the site for the impact event that caused the Cretaceous-Tertiary (K-T) extinctions. A considerable thickness of anhydrite (CaSO4) forms part of the target rock. High temperatures resulting from impact would drive SO2 off from the anhydrite. Hundreds of billions of tonnes of sulfuric acid aerosol would thus enter the stratosphere and cause considerable cooling of the Earth's surface, decrease photosynthesis by orders of magnitude, deplete the ozone layer, and permit increased UV radiation to reach the Earth's surface. Finally, the aerosol would fall back to Earth as acid rain and devastate land and some lacustrine biota and near-surface marine creatures. The presence of anhydrite in the Chicxulub target rock may thus help explain the many extinctions observed at the K-T boundary. ?? 1992.

Chemical, physical, and optical evolution of biomass burning aerosols: a case study

NASA Astrophysics Data System (ADS)

Adler, G.; Flores, J. M.; Abo Riziq, A.; Borrmann, S.; Rudich, Y.

2011-02-01

In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB) event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS) was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI) was derived using a white light optical particle counter (WELAS). The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03) + 0.07i(±0.03), during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01) + 0.04i(±0.01) compared to m = 1.49(±0.01) + 0.02i(±0.01) of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs) were detected during the entire event, which suggest possible implications for human health during such extensive event.

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, Fred G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2012-12-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at higher and lower sun elevation, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as sun elevation increases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, F. G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2013-03-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Impacts of brown carbon from biomass burning on surface UV and ozone photochemistry in the Amazon Basin

PubMed Central

Mok, Jungbin; Krotkov, Nickolay A.; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F.; Li, Zhanqing; Dickerson, Russell R.; Stenchikov, Georgiy L.; Osipov, Sergey; Ren, Xinrong

2016-01-01

The spectral dependence of light absorption by atmospheric particulate matter has major implications for air quality and climate forcing, but remains uncertain especially in tropical areas with extensive biomass burning. In the September-October 2007 biomass-burning season in Santa Cruz, Bolivia, we studied light absorbing (chromophoric) organic or “brown” carbon (BrC) with surface and space-based remote sensing. We found that BrC has negligible absorption at visible wavelengths, but significant absorption and strong spectral dependence at UV wavelengths. Using the ground-based inversion of column effective imaginary refractive index in the range 305–368 nm, we quantified a strong spectral dependence of absorption by BrC in the UV and diminished ultraviolet B (UV-B) radiation reaching the surface. Reduced UV-B means less erythema, plant damage, and slower photolysis rates. We use a photochemical box model to show that relative to black carbon (BC) alone, the combined optical properties of BrC and BC slow the net rate of production of ozone by up to 18% and lead to reduced concentrations of radicals OH, HO2, and RO2 by up to 17%, 15%, and 14%, respectively. The optical properties of BrC aerosol change in subtle ways the generally adverse effects of smoke from biomass burning. PMID:27833145

Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate

ERIC Educational Resources Information Center

Science, 1971

1971-01-01

Mathematical models indicate increasing atmospheric carbon dioxide causes an increase in surface temperature at a decreasing rate, and the rate of temperature decrease caused by increasing aerosols increases with aerosol concentration. (AL)

Stratospheric Ozone Response in Experiments G3 and G4 of the Geoengineering Model Intercomparison Project (GeoMIP)

NASA Technical Reports Server (NTRS)

Pitari, Giovanni; Aquila, Valentina; Kravitz, Ben; Watanabe, Shingo; Tilmes, Simone; Mancini, Eva; DeLuca, Natalia; DiGenova, Glauco

2013-01-01

Geoengineering with stratospheric sulfate aerosols has been proposed as a means of temporarily cooling the planet, alleviating some of the side effects of anthropogenic CO2 emissions. However, one of the known side effects of stratospheric injections of sulfate aerosols is a decrease in stratospheric ozone. Here we show results from two general circulation models and two coupled chemistry climate models that have simulated stratospheric sulfate aerosol geoengineering as part of the Geoengineering Model Intercomparison Project (GeoMIP). Changes in photolysis rates and upwelling of ozone-poor air in the tropics reduce stratospheric ozone, suppression of the NOx cycle increases stratospheric ozone, and an increase in available surfaces for heterogeneous chemistry modulates reductions in ozone. On average, the models show a factor 20-40 increase of the sulfate aerosol surface area density (SAD) at 50 hPa in the tropics with respect to unperturbed background conditions and a factor 3-10 increase at mid-high latitudes. The net effect for a tropical injection rate of 5 Tg SO2 per year is a decrease in globally averaged ozone by 1.1-2.1 DU in the years 2040-2050 for three models which include heterogeneous chemistry on the sulfate aerosol surfaces. GISS-E2-R, a fully coupled general circulation model, performed simulations with no heterogeneous chemistry and a smaller aerosol size; it showed a decrease in ozone by 9.7 DU. After the year 2050, suppression of the NOx cycle becomes more important than destruction of ozone by ClOx, causing an increase in total stratospheric ozone. Contribution of ozone changes in this experiment to radiative forcing is 0.23 W m-2 in GISS-E2-R and less than 0.1 W m-2 in the other three models. Polar ozone depletion, due to enhanced formation of both sulfate aerosol SAD and polar stratospheric clouds, results in an average 5 percent increase in calculated surface UV-B.

Products and Mechanism of Aerosol Formation from the Reaction of β-Pinene with NO3 Radicals: Role of Oligomer Formation

NASA Astrophysics Data System (ADS)

Claflin, M. S.; Ziemann, P. J.

2017-12-01

Large amounts of organic nitrates have been reported in aerosol analyzed during field studies conducted around the world. Although organic nitrates can be formed in daytime from the oxidation of volatile organic compounds in the presence of NOx, it has recently been proposed that the nighttime reaction of monoterpenes with NO3 radicals may account for a substantial fraction of these compounds. While past studies have made progress quantifying the aerosol forming potential of these reactions, relatively little is known about the gas-phase oxidation mechanism, the identities of stable products, and their fate after they partition into aerosol. In an effort to better understand these reactions, we conducted environmental chamber experiments in which β-pinene was reacted with NO3 radicals and the secondary organic aerosol (SOA) that formed was analyzed online using a thermal desorption particle beam mass spectrometer and offline using a variety of methods. SOA was collected on filters, extracted, and analyzed using derivatization-spectrophotometric methods to quantify carbonyl, hydroxyl, carboxyl, nitrate, peroxide, and ester functional groups; and molecular products were identified and quantified by coupling high performance liquid chromatography with UV-Vis detection and mass spectrometry with electrospray ionization, electron ionization, and chemical ionization. We identified and quantified >98% of the products in the SOA and found that 95% were oligomers formed through hemiacetal and acetal reactions. This information was used to determine the yields of monomer building blocks, which in turn were combined with modeling to estimate branching ratios in the gas-phase oxidation reaction and timescales of oligomer formation within the aerosol. The results of this study highlight several key processes in the formation of SOA from reactions of monoterpenes with NO3 radicals: (1) alkoxy radical chemistry, including the role of ring opening through decomposition (2) particle-phase reactions and (3) formation of separate organic and aqueous phases within aerosol.

VUV photodynamics of free tholins nanoparticles investigated by imaging Angle-Resolved Photoemission with the Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Tigrine, Sarah; Nahon, Laurent; Carrasco, Nathalie; Garcia-Macias, Gustavo

2016-06-01

Thanks to the Cassini Huygens mission, it is now established that the aerosols appear from an altitude of 1,000 km in Titan's atmosphere. Once they are formed and through their descent towards the surface, those grains will still interact with persistent UV/VUV radiations, at different energies, that can reach lower atmospheric layers. This interaction has some impact, for example on the radiative transfer or on the ionization yield of the atmospheric compounds. Models are a good way to study those processes, but the lack of data on the refractive index or the absolute absorption/ionization cross subsections of the aerosols can be an obstacle. In order to shed some light and quantify those processes, we ionize analogs of aerosols produced with the PAMPRE experiment (LATMOS) on the SAPHIRS platform from the DESIRS VUV beamline at the synchrotron SOLEIL, equipped with an aerodynamic lens. The aerosols are injected directly under vacuum as isolated free nanoparticles and do not need to take the form of a film deposited on a substrate. The generated photoelectrons are then collected with a Velocity Map Imaging detector and their energetic and angular signatures are analyzed using the ARPES method (Angle-Resolved PhotoElectron Spectroscopy). Both the nanoparticles size distribution and the incident wavelength determine the parameters governing the photoemission process (intra-particles electron mean free path, photon penetration depth) as revealed by the angular distribution of the photoelectron showing in same cases a marked forward/backward asymmetry with respect to the photon axis. Those parameters may provide us with information on the optical behavior of the aerosols. In addition we can extract the ionization potential in direct connection with the absorption cross subsections of the aerosol, from which altitude dependent photodynamics can be unraveled. We will present here the experiments performed, at different VUV energies, on Titan's aerosol analogs with the ARPES method and show how the first results can have implications regarding Titan's atmosphere overall optical characteristics.

Remote sensing and in-situ measurements of tropospheric aerosol, a PAMARCMiP case study

NASA Astrophysics Data System (ADS)

Hoffmann, Anne; Osterloh, Lukas; Stone, Robert; Lampert, Astrid; Ritter, Christoph; Stock, Maria; Tunved, Peter; Hennig, Tabea; Böckmann, Christine; Li, Shao-Meng; Eleftheriadis, Kostas; Maturilli, Marion; Orgis, Thomas; Herber, Andreas; Neuber, Roland; Dethloff, Klaus

2012-06-01

In this work, a closure experiment for tropospheric aerosol is presented. Aerosol size distributions and single scattering albedo from remote sensing data are compared to those measured in-situ. An aerosol pollution event on 4 April 2009 was observed by ground based and airborne lidar and photometer in and around Ny-Ålesund, Spitsbergen, as well as by DMPS, nephelometer and particle soot absorption photometer at the nearby Zeppelin Mountain Research Station. The presented measurements were conducted in an area of 40 × 20 km around Ny-Ålesund as part of the 2009 Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP). Aerosol mainly in the accumulation mode was found in the lower troposphere, however, enhanced backscattering was observed up to the tropopause altitude. A comparison of meteorological data available at different locations reveals a stable multi-layer-structure of the lower troposphere. It is followed by the retrieval of optical and microphysical aerosol parameters. Extinction values have been derived using two different methods, and it was found that extinction (especially in the UV) derived from Raman lidar data significantly surpasses the extinction derived from photometer AOD profiles. Airborne lidar data shows volume depolarization values to be less than 2.5% between 500 m and 2.5 km altitude, hence, particles in this range can be assumed to be of spherical shape. In-situ particle number concentrations measured at the Zeppelin Mountain Research Station at 474 m altitude peak at about 0.18 μm diameter, which was also found for the microphysical inversion calculations performed at 850 m and 1500 m altitude. Number concentrations depend on the assumed extinction values, and slightly decrease with altitude as well as the effective particle diameter. A low imaginary part in the derived refractive index suggests weakly absorbing aerosols, which is confirmed by low black carbon concentrations, measured at the Zeppelin Mountain as well as on board the Polar 5 aircraft.

Particulate-Phase Carbonyls: Laboratory and Pacific 2001 Field Measurements

NASA Astrophysics Data System (ADS)

Liggio, J.; McLaren, R.

2002-12-01

Atmospheric aldehydes and ketones are important constituents of the gas phase. They are emitted from athropogenic and biogenic sources directly, but are also formed as secondary oxidation products of a variety of saturated and unsaturated hydrocarbons. Although their gas phase occurrence and chemistry is well known, the presence of these compounds in the particulate phase is not completely understood. A method has been developed to measure particulate phase carbonyls. Analysis was performed by a simultaneous extraction and derivatization of carbonyls by 2,4-dinitrophenylhydrazine. The subsequent derivatives are pre-concentrated and injected onto an HPLC and detected by UV absorption. Laboratory studies of the extraction kinetics, suggest that partitioning of even highly volatile carbonyls may be possible. Also, experiments performed to determine the extent of positive artifacts on Teflon coated filters, indicate that measurements of these volatile carbonyls are likely not a result of gas-phase adsorption to the filter. These studies also indicate that sampling on quartz fiber filters may introduce significantly more uncertainty with respect to positive artifacts. The analytical method was used to analyze filters sampled during the Pacific 2001 field campaign. Particulate samples were collected on Teflon coated glass-fiber filters. Samples were collected at an urban site (Slocan Park,Vancouver), a rural site (Langley) and an elevated rural mountain site (Eagle Ridge, Sumas). Preliminary results show several carbonyls present in aerosols, at pg/m3 to ng/m3 levels. Detected carbonyls of possible anthropogenic origin include formaldehyde, acetaldehyde, acetone, propanal, glyoxal and methylglyoxal. Detected carbonyls of biogenic origin include pinonaldehyde and nopinone, known oxidation products of the biogenically emitted a-pinene and b-pinene. Possible mechanisms for carbonyl partitioning and implications for their contribution to aerosols in the Lower Fraser Valley will be presented.

Multicomponent aerosol particle deposition in a realistic cast of the human upper respiratory tract.

PubMed

Nordlund, Markus; Belka, Miloslav; Kuczaj, Arkadiusz K; Lizal, Frantisek; Jedelsky, Jan; Elcner, Jakub; Jicha, Miroslav; Sauser, Youri; Le Bouhellec, Soazig; Cosandey, Stephane; Majeed, Shoaib; Vuillaume, Grégory; Peitsch, Manuel C; Hoeng, Julia

2017-02-01

Inhalation of aerosols generated by electronic cigarettes leads to deposition of multiple chemical compounds in the human airways. In this work, an experimental method to determine regional deposition of multicomponent aerosols in an in vitro segmented, realistic human lung geometry was developed and applied to two aerosols, i.e. a monodisperse glycerol aerosol and a multicomponent aerosol. The method comprised the following steps: (1) lung cast model preparation, (2) aerosol generation and exposure, (3) extraction of deposited mass, (4) chemical quantification and (5) data processing. The method showed good agreement with literature data for the deposition efficiency when using a monodisperse glycerol aerosol, with a mass median aerodynamic diameter (MMAD) of 2.3 μm and a constant flow rate of 15 L/min. The highest deposition surface density rate was observed in the bifurcation segments, indicating inertial impaction deposition. The experimental method was also applied to the deposition of a nebulized multicomponent aerosol with a MMAD of 0.50 μm and a constant flow rate of 15 L/min. The deposited amounts of glycerol, propylene glycol and nicotine were quantified. The three analyzed compounds showed similar deposition patterns and fractions as for the monodisperse glycerol aerosol, indicating that the compounds most likely deposited as parts of the same droplets. The developed method can be used to determine regional deposition for multicomponent aerosols, provided that the compounds are of low volatility. The generated data can be used to validate aerosol deposition simulations and to gain insight in deposition of electronic cigarette aerosols in human airways.

Optimal Aerosol Parameterization for Remote Sensing Retrievals

NASA Technical Reports Server (NTRS)

Newchurch, Michael J.

2004-01-01

We have developed a new algorithm for the retrieval of aerosol and gases from SAGE It1 solar transmission measurements. This algorithm improves upon the NASA operational algorithm in several key aspects, including solving the problem non-linearly and incorporating a new methodology for separating the contribution of aerosols and gases. In order to extract aerosol information we have built a huge database of aerosol models for both stratospheric and tropospheric aerosols, and polar stratospheric cloud particles. This set of models allows us to calculate a vast range of possible extinction spectra for aerosols. and from these, derive a set of eigenvectors which then provide the basis set used in our inversion algorithm. Our aerosol algorithm and retrievals are described in several articles (listed in References Section) published under this grant. In particular they allow us to analyze the spectral properties of aerosols and PSCs and ultimately derive their microphysical properties. We have found some considerable differences between our spectra and the ones derived from the SAGE III operational algorithm. These are interesting as they provide an independent check on the validity of published aerosol data and, in particular, on their associated uncertainties. In order to understand these differences, we are assembling independent aerosol data from other sources with which to make comparisons. We have carried out extensive comparisons of our ozone retrievals with both SAGE III and independent lidar, ozonesonde, and satellite measurements (Polyakov et al., 2004). These show very good agreement throughout the stratosphere and help to quantify differences which can be attributed to natural variation in ozone versus that produced by algorithmic differences. In the mid - upper stratosphere, agreement with independent data was generally within 5 - 20%. but in the lower stratosphere the differences were considerably larger. We believe that a large proportion of this discrepancy in the lower stratosphere is attributable to natural variation, and is also seen in comparisons between lidar and ozonesonde measurements. NO2 profiles obtained with our algorithm were compared to those obtained through the SAGE III operational algorithm and exhibited differences of 20 - 40%. Our retrieved profiles agree with the HALOE NO2 measurements significantly better than those of the operational retrieval. In other work (described below), we are extending our aerosol retrievals into the infrared regime and plan to perform retrievals from combined uv-visible-infrared spectra. This work will allow us to use the spectra to derive the size and composition of aerosols, and we plan to employ our algorithms in the analysis of PSC spectra. We are presently also developing a limb-scattering algorithm to retrieve aerosol data from limb measurements of solar scattered radiation.

Optical Trapping-Cavity Ringdown Spectroscopy System for Single Aerosol Particle Measurements

DTIC Science & Technology

2015-02-17

ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Final Report REPORT DOCUMENTATION PAGE 11. SPONSOR...focused 532 nm laser ( Bermuda grass smut spores, horizontal illumination at power of 4.5 mW, focus length = 10 mm, UV quartz cuvette is from Starna...Cells, Inc.) (b) Single bioaerosol particles trapped using a focused 405 nm laser ( Bermuda grass smut spores, upward illumination at power of 2.0

A flash-lamp based device for fluorescence detection and identification of individual pollen grains.

PubMed

Kiselev, Denis; Bonacina, Luigi; Wolf, Jean-Pierre

2013-03-01

We present a novel optical aerosol particle detector based on Xe flash lamp excitation and spectrally resolved fluorescence acquisition. We demonstrate its performances on three natural pollens acquiring in real-time scattering intensity at two wavelengths, sub-microsecond time-resolved scattering traces of the particles' passage in the focus, and UV-excited fluorescence spectra. We show that the device gives access to a rather specific detection of the bioaerosol particles.

The uk Lidar-sunphotometer operational volcanic ash monitoring network

NASA Astrophysics Data System (ADS)

Adam, Mariana; Buxmann, Joelle; Freeman, Nigel; Horseman, Andrew; Salmon, Christopher; Sugier, Jacqueline; Bennett, Richard

2018-04-01

The Met Office completed the deployment of ten lidars (UV Raman and depolarization), each accompanied by a sunphotometer (polarized model), to provide quantitative monitoring of volcanic ash over UK for VAAC London. The lidars provide range corrected signal and volume depolarization ratio in near-real time. The sunphotometers deliver aerosol optical depth, Ångstrom exponent and degree of linear polarization. Case study analyses of Saharan dust events (as a proxy for volcanic ash) are presented.

Evaluating Satellite Retrievals of Smoke Aerosol above Clouds using Airborne High Spectral Resolution Lidar Measurements during ORACLES

NASA Astrophysics Data System (ADS)

Ferrare, R. A.; Burton, S. P.; Cook, A. L.; Harper, D. B.; Hostetler, C. A.; Hair, J. W.; Vaughan, M.; Hu, Y.; Fenn, M. A.; Clayton, M.; Scarino, A. J.; Jethva, H. T.; Sayer, A. M.; Meyer, K.; Torres, O.; Josset, D. B.; Redemann, J.

2017-12-01

The NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-2) provided extensive measurements of smoke above shallow marine clouds while deployed from the NASA ER-2 aircraft during the NASA EV-S Observations of Aerosols above Clouds and their Interactions (ORACLES) mission. During the first ORACLES field campaign in September 2016, the ER-2 was deployed from Walvis Bay, Namibia and conducted flights over the southeastern Atlantic Ocean. HSRL-2 measured profiles of aerosol backscattering, extinction and aerosol optical depth (AOD) at 355 and 532 nm and aerosol backscattering and depolarization at 1064 nm and so provided an excellent characterization of the widespread smoke layers above shallow marine clouds. OMI, MODIS, and CALIOP satellite retrievals of above cloud AOD (ACAOD) are compared to the HSRL-2 measurements. The OMI above-cloud aerosols data product (OMACA) ACAOD product relies on the spectral contrast produced by aerosol absorption in two near-UV measurements (354 and 388 nm) to derive ACAOD. Two MODIS ACAOD products are examined; the first ("multichannel') relies on the spectral contrast in aerosol absorption derived from reflectance measurements at six MODIS channels from the visible to the shortwave infrared (swIR). The second method is an extension of the "Deep Blue" method and differs from the multichannel method in that it does not use swIR channels. The CALIOP V4 operational and "depolarization ratio (DR)" methods of retrieving ACAOD are also examined. The MODIS and OMI ACAOD values were well correlated (r2>0.6) with the HSRL-2 ACAOD values; bias differences were generally less than about 0.1 at 532 nm (10-30%). The CALIOP operational retrievals missed a significant amount of aerosol and so were biased low by 50-75% compared to HSRL-2. In contrast, the CALIOP DR method produced ACAOD values in excellent agreement (bias differences less than 0.03 (5%)) with HSRL-2. Aerosol extinction profiles computed for the smoke layer using the CALIOP attenuated backscatter profiles and constrained by the CALIOP DR ACAOD retrievals are also found to agree well on average with coincident HSRL-2 extinction profiles. These constrained CALIOP extinction profiles are used to characterize the smoke distribution over this region.

Host Model Uncertainty in Aerosol Radiative Forcing Estimates - The AeroCom Prescribed Experiment

NASA Astrophysics Data System (ADS)

Stier, P.; Kinne, S.; Bellouin, N.; Myhre, G.; Takemura, T.; Yu, H.; Randles, C.; Chung, C. E.

2012-04-01

Anthropogenic and natural aerosol radiative effects are recognized to affect global and regional climate. However, even for the case of identical aerosol emissions, the simulated direct aerosol radiative forcings show significant diversity among the AeroCom models (Schulz et al., 2006). Our analysis of aerosol absorption in the AeroCom models indicates a larger diversity in the translation from given aerosol radiative properties (absorption optical depth) to actual atmospheric absorption than in the translation of a given atmospheric burden of black carbon to the radiative properties (absorption optical depth). The large diversity is caused by differences in the simulated cloud fields, radiative transfer, the relative vertical distribution of aerosols and clouds, and the effective surface albedo. This indicates that differences in host model (GCM or CTM hosting the aerosol module) parameterizations contribute significantly to the simulated diversity of aerosol radiative forcing. The magnitude of these host model effects in global aerosol model and satellites retrieved aerosol radiative forcing estimates cannot be estimated from the diagnostics of the "standard" AeroCom forcing experiments. To quantify the contribution of differences in the host models to the simulated aerosol radiative forcing and absorption we conduct the AeroCom Prescribed experiment, a simple aerosol model and satellite retrieval intercomparison with prescribed highly idealised aerosol fields. Quality checks, such as diagnostic output of the 3D aerosol fields as implemented in each model, ensure the comparability of the aerosol implementation in the participating models. The simulated forcing variability among the models and retrievals is a direct measure of the contribution of host model assumptions to the uncertainty in the assessment of the aerosol radiative effects. We will present the results from the AeroCom prescribed experiment with focus on the attribution to the simulated variability to parametric and structural model uncertainties. This work will help to prioritise areas for future model improvements and ultimately lead to uncertainty reduction.

Seasonal dependence of aerosol processing in urban Philadelphia

NASA Astrophysics Data System (ADS)

Avery, A. M.; Waring, M. S.; DeCarlo, P. F.

2017-12-01

Urban aerosols pose an important threat to human health due to the conflation of emissions and concentrated population exposed. Winter and summer aerosol and trace gas measurements were taken in downtown Philadelphia in 2016. Measurements included aerosol composition and size with an Aerodyne Aerosol Mass Spectrometer (AMS), particle size distributions with an SMPS, and an aethalometer. Trace gas measurements of O3, NO, CH4, CO, and CO2 were taken concurrently. Sampling in seasonal extremes provided contrast in aerosol and trace gas composition, aerosol processing, and emission factors. Inorganic aerosol components contributed approximately 60% of the submicron aerosol mass, while summertime aerosol composition was roughly 70% organic matter. Positive Matrix Factorization (PMF) on the organic aerosol (OA) matrix revealed three factors in common in each season, including an oxygenated organic aerosol (OOA) factor with different temporal behavior in each season. In summertime, OOA varied diurnally with ozone and daytime temperature, but in the wintertime, it was anti-correlated with ozone and temperature, and instead trended with calculated liquid water, indicating a seasonally-dependent processing of organic aerosol in Philadelphia's urban environment. Due to the inorganic dominant winter aerosol, liquid water much higher (2.65 μg/m3) in winter than in summer (1.54 μg/m3). Diurnally varying concentrations of background gas phase species (CH4, CO2) were higher in winter and varied less as a result of boundary layer conditions; ozone was also higher in background in winter than summer. Winter stagnation events with low windspeed showed large buildup of trace gases CH4, CO, CO2, and NO. Traffic related aerosol was also elevated with black carbon and hydrocarbon-like OA (HOA) plumes of each at 3-5 times higher than the winter the average value for each. Winter ratios of HOA to black carbon were significantly higher in the winter than the summer due to lower temperatures. Aerosol compositional differences in winter and summer indicate Philadelphia resident's aerosol exposures vary significantly with season.

Aerosols

Atmospheric Science Data Center

2013-04-17

... depth. A color scale is used to represent this quantity, and high aerosol amount is indicated by yellow or green pixels, and clearer skies ... out most clearly, whereas MISR's oblique cameras enhance sensitivity to even thin layers of aerosols. In the March image, the only ...

A multivariate auto-regressive combined-harmonics analysis and its application to ozone time series data

NASA Astrophysics Data System (ADS)

Yang, Eun-Su

2001-07-01

A new statistical approach is used to analyze Dobson Umkehr layer-ozone measurements at Arosa for 1979-1996 and Total Ozone Mapping Spectrometer (TOMS) Version 7 zonal mean ozone for 1979-1993, accounting for stratospheric aerosol optical depth (SAOD), quasi-biennial oscillation (QBO), and solar flux effects. A stepwise regression scheme selects statistically significant periodicities caused by season, SAOD, QBO, and solar variations and filters them out. Auto-regressive (AR) terms are included in ozone residuals and time lags are assumed for the residuals of exogenous variables. Then, the magnitudes of responses of ozone to the SAOD, QBO, and solar index (SI) series are derived from the stationary time series of the residuals. These Multivariate Auto-Regressive Combined Harmonics (MARCH) processes possess the following significant advantages: (1)the ozone trends are estimated more precisely than the previous methods; (2)the influences of the exogenous SAOD, QBO, and solar variations are clearly separated at various time lags; (3)the collinearity of the exogenous variables in the regression is significantly reduced; and (4)the probability of obtaining misleading correlations between ozone and exogenous times series is reduced. The MARCH results indicate that the Umkehr ozone response to SAOD (not a real ozone response but rather an optical interference effect), QBO, and solar effects is driven by combined dynamical radiative-chemical processes. These results are independently confirmed using the revised Standard models that include aerosol and solar forcing mechanisms with all possible time lags but not by the Standard model when restricted to a zero time lag in aerosol and solar ozone forcings. As for Dobson Umkehr ozone measurements at Arosa, the aerosol effects are most significant in layers 8, 7, and 6 with no time lag, as is to be expected due to the optical contamination of Umkehr measurements by SAOD. The QBO and solar UV effects appear in all layers 4-8, and in total ozone. In order to account for annual modulation of the equatorial winds that affects ozone at midlatitudes, a new QBO proxy is selected and applied to the Dobson Umkehr measurements at Arosa. The QBO proxy turns out to be more effective to filter the modulated ozone signals at midlatitudes than the mostly used QBO proxy, the Singapore winds at 30 mb. A statistically significant negative phase relationship is found between solar UV variation and ozone response, especially in layer 4, implying dynamical effects of solar variations on ozone at midlatitudes. Linear negative trends in ozone of -7.8 +/- 1.1 and -5.2 +/- 1.4 [%/decade +/- 2σ] are calculated in layers 7 (~35 km) and 8 (~40 km), respectively, for the period of 1979-1996, with smaller trends of -2.2 +/- 1.0, 1.8 +/- 0.9, and -1.4 +/- 1.1 in layers 6 (~30 km), 5 (~25 km), and 4 (~20 km), respectively. A trend in total ozone (layers 1 through 10) of -2.9 +/- 1.2 [%/decade +/- 2σ] is found over this same period. The aerosol effects obtained from the TOMS zonal means become significant at midlatitudes. QBO ozone contributes to the TOMS zonal means by +/-2 to 4% of their means. The negative solar ozone responses are also found at midlatitudes from the TOMS measurements. The most negative trends from TOMS zonal means are about -6.3 +/- 0.6%/decade at 40-50°N.

Organic haze on Titan and the early Earth

PubMed Central

Trainer, Melissa G.; Pavlov, Alexander A.; DeWitt, H. Langley; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A.

2006-01-01

Recent exploration by the Cassini/Huygens mission has stimulated a great deal of interest in Saturn's moon, Titan. One of Titan's most captivating features is the thick organic haze layer surrounding the moon, believed to be formed from photochemistry high in the CH4/N2 atmosphere. It has been suggested that a similar haze layer may have formed on the early Earth. Here we report laboratory experiments that demonstrate the properties of haze likely to form through photochemistry on Titan and early Earth. We have used a deuterium lamp to initiate particle production in these simulated atmospheres from UV photolysis. Using a unique analysis technique, the aerosol mass spectrometer, we have studied the chemical composition, size, and shape of the particles produced as a function of initial trace gas composition. Our results show that the aerosols produced in the laboratory can serve as analogs for the observed haze in Titan's atmosphere. Experiments performed under possible conditions for early Earth suggest a significant optical depth of haze may have dominated the early Earth's atmosphere. Aerosol size measurements are presented, and implications for the haze layer properties are discussed. We estimate that aerosol production on the early Earth may have been on the order of 1014 g·year−1 and thus could have served as a primary source of organic material to the surface. PMID:17101962

[Research progress and direction of atmospheric brown carbon].

PubMed

Yan, Cai-Qing; Zheng, Mei; Zhang, Yuan-Hang

2014-11-01

Organic aerosol is one of the most important components of atmospheric aerosols. In recent years, organic aerosol has been found and proved to be light absorbing in UV-Visible region. Light absorbing organic carbon (also named as brown carbon) has been one of the forefronts in the field of atmospheric research. Its light absorption contributions to radiative forcing, regional air quality, and global climate change have drawn much attention. Regional air pollution is complex in China. Frequent visibility decline and severe regional haze episodes occurred since January 2013. Previous studies showed high amount of estimated columnar light-absorbing organic carbon in China, and according to current research findings, major sources of fine particulate matter in China (e. g. biomass burning and fossil fuel combustion) were also recognized as the main sources for brown carbon. Considering the high abundance of brown carbon in atmosphere, there is a great need to reconsider and reevaluate contributions of organic aerosol to light absorption, especially its role in haze formation and radiative forcing. However, up to now, basic researches on light absorbing organic carbon are still limited in China. This study aimed to elucidate the need for basic research on brown carbon, summarize previous studies and research progress from different aspects such as sources, composition, measurement, mass concentration distribution, optical property, radiative forcing of brown carbon, point out the existing problems and deficiencies, and put forward suggestions for future study.

Modification of spectral ultraviolet doses by different types of overcast cloudiness and atmospheric aerosol.

PubMed

Aun, Margit; Eerme, Kalju; Ansko, Ilmar; Veismann, Uno; Lätt, Silver

2011-01-01

Wavelength-dependent attenuation of ground-level ultraviolet (UV) dose by different cloud and aerosol situations at the Tartu Observatory site (58°15' N, 26°28' E, 70 m a.s.l) is under scrutiny. The spectra at wavelengths ranging below 400 nm have been recorded by the simple Avantes, Inc. array spectrometer AvaSpec-256 in 2004-2009. The spectral information was supported by the conventional broadband solar irradiance and by the necessary meteorological data. The average cloud modification factor (CMF) on overcast days from May to August has been quite low, 0.36 in UVA and 0.35 in UVB. In the UVA range, the reduction of the daily dose with increasing noon solar zenith angle (SZA) from 35-50° to 65-80° in overcast days has been about 20% more than in clear days, while in the UVB range it was 45% larger. No clear difference in the influence of SZA on CMF between low level (St, Ns) and medium level (As, Ac) overcast cloudiness has been found. The aerosol attenuation during large aerosol optical depth (AOD) episode has been comparable with that of medium level clouds with the wavelength dependency in the UVA range different from that of clouds. © 2011 The Authors. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

Laboratory Studies of Planetary Hazes: composition of cool exoplanet atmospheric aerosols with very high resolution mass spectrometry

NASA Astrophysics Data System (ADS)

Moran, Sarah E.; Horst, Sarah; He, Chao; Flandinet, Laurene; Moses, Julianne I.; Orthous-Daunay, Francois-Regis; Vuitton, Veronique; Wolters, Cedric; Lewis, Nikole

2017-10-01

We present first results of the composition of laboratory-produced exoplanet haze analogues. With the Planetary HAZE Research (PHAZER) Laboratory, we simulated nine exoplanet atmospheres of varying initial gas phase compositions representing increasing metallicities (100x, 1000x, and 10000x solar) and exposed them to three different temperature regimes (600, 400, and 300 K) with two different “instellation” sources (a plasma source and a UV lamp). The PHAZER exoplanet experiments simulate a temperature and atmospheric composition phase space relevant to the expected planetary yield of the Transiting Exoplanet Survey Satellite (TESS) mission as well as recently discovered potentially habitable zone exoplanets in the TRAPPIST-1, LHS-1140, and Proxima Centauri systems. Upon exposure to the energy sources, all of these experiments produced aerosol particles, which were collected in a dry nitrogen glove box and then analyzed with an LTQ Orbitrap XL™ Hybrid Ion Trap-Orbitrap Mass Spectrometer utilizing m/z ranging from 50 to 1000. The collected aerosol samples were found to contain complex organics. Constraining the composition of these aerosols allows us to better understand the photochemical and dynamical processes ongoing in exoplanet atmospheres. Moreover, these data can inform our telescope observations of exoplanets, which is of critical importance as we enter a new era of exoplanet atmosphere observation science with the upcoming launch of the James Webb Space Telescope. The molecular makeup of these haze particles provides key information for understanding exoplanet atmospheric spectra, and constraining the structure and behavior of clouds, hazes, and other aerosols is at the forefront of exoplanet atmosphere science.

Mars hemispherical albedo map: absolute value and interannual variability inferred from OMEGA data.

NASA Astrophysics Data System (ADS)

Vincendon, M.; Audouard, J.; Langevin, Y.; Poulet, F.; Bellucci, G.; Bibring, J.-P.; Gondet, B.

2012-04-01

The surface reflectance integrated over all directions and solar wavelengths ("hemispherical albedo") controls the radiative budget at the surface of Mars, and hence its climate. Reference albedo maps are usually derived from nadir observation of surface reflectance through clear atmospheric conditions. However, the atmosphere of Mars is permanently loaded with a significant amount of aerosols (typical visible optical depths of 0.5 under clear atmospheric conditions), which impacts the evaluation of "aerosol free" surface reflectances from remote sensing data. Moreover, the Martian surface is usually assumed to be Lambertian, both for simplicity and due to the lack of robust constraints about its bidirectional properties. We used OMEGA visible and near-IR measurements, with an appropriate UV extrapolation, to calculate as a function of space and time the hemispherical surface albedo of Mars. The contribution of aerosols is removed using a radiative transfer model and recent aerosols properties. Uncertainties associated with this procedure are calculated. The aerosols correction increases the bright/dark surfaces contrast. Typical, mean bidirectional reflectance properties of the martian surface are estimated using MER surface measurements and CRISM remote "EPF" observations. From these constraints, we have derived a typical relationship that makes it possible to convert single nadir measurements of the reflectance into hemispherical albedo. Accounting for the BRDF of the martian surface typically modify by ± 15% the derived albedo, depending on solar zenith angles. We will present our methods and preliminary results regarding seasonal and interannual variations of the surface albedo of Mars during years 2004-2011.

Impact of Biomass Burning Plumes on Photolysis Rates and Ozone Formation at the Mount Bachelor Observatory

NASA Astrophysics Data System (ADS)

Baylon, P.; Jaffe, D. A.; Hall, S. R.; Ullmann, K.; Alvarado, M. J.; Lefer, B. L.

2018-02-01

In this paper, we examine biomass burning (BB) events at the Mt. Bachelor Observatory (MBO) during the summer of 2015. We explored the photochemical environment in these BB plumes, which remains poorly understood. Because we are interested in understanding the effect of aerosols only (as opposed to the combined effect of aerosols and clouds), we carefully selected three cloud-free days in August and investigate the photochemistry in these plumes. At local midday (solar zenith angle (SZA) = 35°), j(NO2) values were slightly higher (0.2-1.8%) in the smoky days compared to the smoke-free day, presumably due to enhanced scattering by the smoke aerosols. At higher SZA (70°), BB aerosols decrease j(NO2) by 14-21%. We also observe a greater decrease in the actinic flux at 310-350 nm, compared to 360-420 nm, presumably due to absorption in the UV by brown carbon. We compare our measurements with results from the Tropospheric Ultraviolet-Visible v.5.2 model. As expected, we find a good agreement (to within 6%) during cloud-free conditions. Finally, we use the extended Leighton relationship and a photochemical model (Aerosol Simulation Program v.2.1) to estimate midday HO2 and RO2 concentrations and ozone production rates (P(O3)) in the fire plumes. We observe that Leighton-derived HO2 and RO2 values (49-185 pptv) and instantaneous P(O3) (2.0-3.6 ppbv/h) are higher than the results from the photochemical model.

An instrument for the simultaneous acquisition of size, shape, and spectral fluorescence data from single aerosol particles

NASA Astrophysics Data System (ADS)

Hirst, Edwin; Kaye, Paul H.; Foot, Virginia E.; Clark, James M.; Withers, Philip B.

2004-12-01

We describe the construction of a bio-aerosol monitor designed to capture and record intrinsic fluorescence spectra from individual aerosol particles carried in a sample airflow and to simultaneously capture data relating to the spatial distribution of elastically scattered light from each particle. The spectral fluorescence data recorded by this PFAS (Particle Fluorescence and Shape) monitor contains information relating to the particle material content and specifically to possible biological fluorophores. The spatial scattering data from PFAS yields information relating to particle size and shape. The combination of these data can provide a means of aiding the discrimination of bio-aerosols from background or interferent aerosol particles which may have similar fluorescence properties but exhibit shapes and/or sizes not normally associated with biological particles. The radiation used both to excite particle fluorescence and generate the necessary spatially scattered light flux is provided by a novel compact UV fiber laser operating at 266nm wavelength. Particles drawn from the ambient environment traverse the laser beam in single file. Intrinsic particle fluorescence in the range 300-570nm is collected via an ellipsoidal concentrator into a concave grating spectrometer, the spectral data being recorded using a 16-anode linear array photomultiplier detector. Simultaneously, the spatial radiation pattern scattered by the particle over 5°-30° scattering angle and 360° of azimuth is recorded using a custom designed 31-pixel radial hybrid photodiode array. Data from up to ~5,000 particles per second may be acquired for analysis, usually performed by artificial neural network classification.

Aerosols in coastal and inland areas in the equatorial African belt.

PubMed

Ssenyonga, Taddeo; Muyimbwa, Dennis; Okullo, Willy; Chen, Yi-Chun; Frette, Øvyind; Hamre, Børge; Steigen, Andreas; Dahlback, Arne; Stamnes, Jakob J

2014-05-10

Aerosols affect the climate directly through absorption and reflection of sunlight back to space and indirectly by acting as cloud condensation nuclei. This paper is based on more than three decades of satellite data (1979-1994 and 1996-2012) from total ozone mapping spectrometer (TOMS) and ozone monitoring instrument (OMI), which have provided measurements of backscattered radiances in the wavelength range from 331 to 380 nm. These data have been used to determine the aerosol climatology and to investigate the influence of the aerosol index (AI) on the ultraviolet index (UVI) in coastal land areas in Serrekunda (13.28°N, 16.34°W), The Gambia, and Dar-es-Salaam (6.8°S, 39.26°E), Tanzania, as well as in inland areas in Kampala (0.19°N, 32.34°E), Uganda. Heavy aerosol loadings were found to occur in the dry seasons at all three locations. To reduce the influence of clouds, we disregarded TOMS and OMI data for days during which the UV reflectivity was larger than 9% and investigated the correlation of the AI with the UVI for the remaining days at the three locations. We found a high correlation coefficient of 0.82 for Serrekunda, but poor correlation for Kampala and Dar-es-Salaam. The average AI for Serrekunda was found to be about three times higher than that for Kampala or Dar-es-Salaam, and a positive trend was found for the AI in Kampala and Dar-es-Salaam, whereas a negative trend was found for the AI in Serrekunda.

Nonlinear optical studies of aqueous interfaces, polymers, and nanowires

NASA Astrophysics Data System (ADS)

Onorato, Robert Michael

Understanding the structure and composition of aqueous interfaces is one of the most important current problems in modern science. Aqueous interfaces are ubiquitous in Nature, ranging from aerosols to cellular structures. Aerosol chemistry is presently the most significant unknown factor in predicting climate change, and an understanding of the chemistry that occurs at aerosol interfaces would significantly improve climate models. Similarly, the nature of aqueous biological interfaces has a profound effect on the structure and function of proteins and other biological structures. Despite the importance of these problems, aqueous interfaces remain incompletely understood due to the challenges of experimentally probing them. Recent experimental and theoretical results have firmly established the existence of enhanced concentrations of selected ions at the air/water interface. In this dissertation, I use an interface-specific technique, UV second harmonic generation (SHG), to further investigate the adsorption of ions to the air/water interface and to extend the study of ion adsorption towards more biologically relevant systems, alcohol/water interfaces. In Chapter 2, I describe resonant UV-SHG studies of the strongly chaotropic thiocyanate ion adsorbed to the interface formed by water and a monolayer of dodecanol, wherein the Gibbs free energy of adsorption was determined to be -6.7 +/- 1.1 and -6.3 +/- 1.8 kJ/mol for sodium and potassium thiocyanate, respectively, coincident with the value determined for thiocyanate at the air/water interface. Interestingly, at concentrations near and above 4 M, the resonant SHG signal increases discontinuously, indicating a structural change in the interfacial region. Recent experimental and theoretical work has demonstrated that the adsorption of bromide is particularly important for chemical reactions on atmospheric aerosols, including the depletion of ozone. In Chapter 3, UV-SHG resonant with the bromide charge-transfer-to-solvent band and a Langmuir adsorption model are used to determine the affinity of bromide for both the air/water and dodecanol/water interfaces in the molar concentration regime. The Gibbs free energy of adsorption for the former is determined to be -1.4 kJ/mol with a lower 90% confidence limit of -4.1 kJ/mol. For the dodecanol/water interface the data are best fit with a Gibbs free energy of +8 kJ/mol with an estimated a lower limit of -4 kJ/mol. Adsorption of ions to the air/water interface in the millimolar regime is a particularly interesting phenomenon. In Chapter 4, the affinity of sodium chloride and sodium bromide to the air/water interface is probed by UV-SHG. Both salts exhibit a strong adsorption, with free energies greater than -20 kJ/mol. Interestingly, sodium chloride exhibits a stronger affinity for the interface than does sodium iodide, which was previously studied by Poul Peterson. This is counter to both experimental and theoretical results for higher concentrations. It has been predicted that ion adsorption is dictated by strong and opposing electrostatic and entropic forces. The change in order of ion interfacial affinity can be explained by relatively small changes in these forces at different concentrations and ionic strengths. In Chapters 5 and 6, other work using nonlinear optical techniques is described. Coherent anti-Stokes Raman scattering microscopy is a promising tool for chemically selective imaging based on molecular vibrations. While CARS is currently used as a biological imaging tool, many variations are still being developed, perhaps the most important being multiplex CARS microscopy. Multiplex CARS has the advantage of comparing images based on different molecular vibrations without changing the excitation wavelengths. In Chapter 5, I demonstrate both high spectral and spatial resolution multiplex CARS imaging of polymer films using a simple scheme for chirped CARS with a spectral bandwidth of 300 cm-1. In Chapter 6, the nonlinear optical properties of KNbO3 nanowires are studied. Using SHG and sum frequency generation, efficient nonlinear optical frequency conversion is demonstrated in single KNbO3 nanowires that act as optical waveguides, yielding a coherent tunable subwavelength light source.

Aerosol reductions could dominate regional climate responses in low GHG emission scenarios

NASA Astrophysics Data System (ADS)

Samset, B. H.; Sand, M.; Smith, C. J.; Bauer, S.; Forster, P.; Fuglestvedt, J. S.; Osprey, S. M.; Schleussner, C. F.

2017-12-01

Limiting global warming to current political goals requires strong, rapid mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline sharply, due to co-emission with greenhouse gases, and future measures to improve air quality. As the net climate effect of GHG and aerosol emissions over the industrial era is poorly constrained, predicting the impact of strong aerosol emission reductions remains challenging. Here we investigate the isolated and compound climate impacts from removing present day anthropogenic emissions of black carbon (BC), organic carbon (OC) and SO2, and moderate, near term GHG dominated global warming, using four coupled climate models. As the dominating effect of aerosol emission reduction is a removal of cooling from sulphur, the resulting climate impacts amplify those of GHG induced warming. BC emissions contribute little to reducing surface warming, but have stronger regional impacts. For the major aerosol emission regions, extreme weather indices are more sensitive to aerosol removal than to GHG increases, per degree of surface warming. East Asia in particular stands out, mainly due to the high present regional aerosol emissions. We show how present climate models indicate that future regional climate change will depend strongly on changes in loading and distribution of aerosols in the atmosphere, in addition to surface temperature change.

Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests

NASA Astrophysics Data System (ADS)

Slowik, J. G.; Stroud, C.; Bottenheim, J. W.; Brickell, P. C.; Chang, R. Y.-W.; Liggio, J.; Makar, P. A.; Martin, R. V.; Moran, M. D.; Shantz, N. C.; Sjostedt, S. J.; van Donkelaar, A.; Vlasenko, A.; Wiebe, H. A.; Xia, A. G.; Zhang, J.; Leaitch, W. R.; Abbatt, J. P. D.

2010-03-01

Measurements of aerosol composition, volatile organic compounds, and CO are used to determine biogenic secondary organic aerosol (SOA) concentrations at a rural site 70 km north of Toronto. These biogenic SOA levels are many times higher than past observations and occur during a period of increasing temperatures and outflow from Northern Ontario and Quebec forests in early summer. A regional chemical transport model approximately predicts the event timing and accurately predicts the aerosol loading, identifying the precursors as monoterpene emissions from the coniferous forest. The agreement between the measured and modeled biogenic aerosol concentrations contrasts with model underpredictions for polluted regions. Correlations of the oxygenated organic aerosol mass with tracers such as CO support a secondary aerosol source and distinguish biogenic, pollution, and biomass burning periods during the field campaign. Using the Master Chemical Mechanism, it is shown that the levels of CO observed during the biogenic event are consistent with a photochemical source arising from monoterpene oxidation. The biogenic aerosol mass correlates with satellite measurements of regional aerosol optical depth, indicating that the event extends across the eastern Canadian forest. This regional event correlates with increased temperatures, indicating that temperature-dependent forest emissions can significantly affect climate through enhanced direct optical scattering and higher cloud condensation nuclei numbers.

Determination of aerosol content in the atmosphere from ERTS-1 data. [San Diego, California and Salton Sea

NASA Technical Reports Server (NTRS)

Griggs, M.; Ludwig, C. B.; Malkmus, W. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Significant results, relating the radiance over water surfaces to the atmospheric aerosol content, have been obtained. The results indicate that the MSS channels 4, 5, and 6 centered at 0.55, 0.65, and 0.75 microns have comparable sensitivity, and that the aerosol content can be determined within + or - 10% with the assumed measurement errors of the MSS. The fourth channel, MSS 7, is not useful for aerosol determination due to the water radiance values from this channel generally being less than the instrument noise. The accuracy of the aerosol content measurement could be increased by using an instrument specifically designed for this purpose. This radiance-aerosol content relationship can possibly provide a basis for monitoring the atmospheric aerosol content on a global basis, allowing a base-line value of aerosols to be established. The contrast-aerosol content investigation shows useful linear relationships in MSS channels 4 and 5, allowing the aerosol content to be determined within + or - 10%. MSS 7 is not useful due to the low accuracy in the water radiance, and MSS 6 is found to be too insensitive. These results rely on several assumptions due to the lack of ground truth data, but do serve to indicate which channels are most useful.

Long-term visibility data in the UK - how does visibility vary with meteorological and pollutant parameters?

NASA Astrophysics Data System (ADS)

Singh, Ajit; Bloss, William J.; Pope, Francis D.

2016-04-01

Poor visibility can be an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to accidents particularly during winter when fogs are prevalent. The present quantitative analysis attempts to explain the influence of aerosol concentration and composition, and meteorology on long-term UK visibility. We use visibility data from eight UK meteorological stations which have been running since the 1950s. The site locations include urban, rural and marine environments. Overall, most stations show a long term trend of visibility increase, which is indicative of reductions in aerosol pollution, especially in urban areas. Additionally, results at all sites show a very clear dependence on relative humidity, indicating the importance of aerosol hygroscopicity on the ability of aerosols to scatter radiation and hence impact upon visibility. The dependence of visibility on other meteorological parameters (e.g. relative humidity, air temperature, wind speed & direction) is also investigated. To explain the long term visibility trends and their dependence on meteorological conditions, a light extinction model was constructed incorporating the concentrations and composition of historic aerosol. The lack of historic aerosol size distributions and aerosol composition data, which determine hygroscopicity and refractive index, leads to an under-constrained model. Aerosol measurements from the last 10 years are used to constrain these model parameters, and hence their historical variation can be estimated; sensitivity analyses are used to estimate errors for the time period before regular aerosol measurements are available. A good agreement is observed between modelled and measured visibility. This work has generated a unique 60 year data set with which to understand how aerosol concentration and composition has varied over the UK. The model is applicable and easily transferrable to other data sets worldwide. Hence, different clean air legislation can be assessed for its effectiveness in reducing aerosol pollution. The implications for the UK will be discussed.

60 years of visibility data in the UK - how does visibility vary with meteorological and pollutant parameters?

NASA Astrophysics Data System (ADS)

Singh, A.; Bloss, W.; Pope, F.

2015-12-01

Reduced visibility can be an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to accidents particularly during the winter season when fogs are prevalent. Here, we explore the combined influence of aerosol characteristics and meteorology on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. Most stations show a long term trend of visibility increase, which is indicative of reductions in aerosol pollution, especially in urban areas. Additionally, results at all sites show a very clear dependence on relative humidity, indicating the importance of aerosol hygroscopicity on the ability of aerosols to scatter radiation and hence impact upon visibility. The dependence of visibility on other meteorological parameters (e.g. wind speed, wind direction) is also investigated. To explain the long term visibility trends and their dependence on meteorological conditions, a light extinction model was constructed incorporating the concentrations and composition of historic aerosol. The lack of historic aerosol size distributions and aerosol composition data, which determine hygroscopicity and refractive index, leads to an under-constrained model. Aerosol measurements from the last 10 years are used to constrain these model parameters, and hence their historical variation can be estimated; sensitivity analyses are used to estimate errors for the time period before regular aerosol measurements are available. This work has generated a unique 60 year data set with which to understand how aerosol concentration and composition has varied over the UK. The model is applicable and easily transferrable to other data sets worldwide. Hence, different clean air legislation can be assessed for its effectiveness in reducing aerosol pollution. The implications for the UK will be discussed.