scholarly journals Solar radiometer sensing of multi-year aerosol features over a tropical urban station: Direct Sun and inversion products

2019 ◽  
Author(s):  
Katta Vijayakumar ◽  
Panuganti C. S. Devara ◽  
Sunil M. Sonbawne ◽  
David M. Giles ◽  
Brent N. Holben ◽  
...  
Keyword(s):  
Significant Role ◽  
Radiative Forcing ◽  
Single Scattering ◽  
Aerosol Size Distribution ◽  
Data Sets ◽  
Spectral Variation ◽  
Study Region ◽  
Aerosol Radiative Forcing ◽  
And Inversion

Abstract. The AErosol RObotic NETwork (AERONET) is the most developed ground-based network for aerosol remote-sensing and has been playing a significant role not only in monitoring air quality for protecting human health but also in assessing the radiative budget of our planet Earth. In this paper, we report the direct sun and inversion products, comprising of spectral variation of Aerosol Optical Depth (AOD), associated Ångström Exponent (AE), fine- and coarse-mode aerosol fractions, Aerosol Size Distribution (ASD), Refractive Index (RI), Asymmetry Parameter (AP), Single Scattering Albedo (SSA), Aerosol Radiative Forcing (ARF), and columnar concentration of gas constituents such as water vapor, ozone and nitrogen peroxide, obtained from a Cimel sun-sky radiometer, functioning at Pune, India, under the AERONET program since October 2004. These long-term measurements carried out from 2005 to 2015 could serve as an urban aerosol optical long-term average or climatology The AOD long-term variations at all wavelengths, considered in the study, exhibited increasing trend, implying year-to-year enhancement in aerosol loading. The mean seasonal variations in AOD from cloud-free days indicated greater values during monsoon, revealing dominance of hygroscopic aerosol particles over the station. Contribution by different aerosol types to AOD has also been deduced, discussed and found dominance of mixed type of aerosols (43.79 %), followed by combination of biomass burning and urban industrial aerosols (22.03 %) compared to other types of aerosols during the study period. The long-term data sets, derived aerosol and trace gas products play a significant role in understanding aerosol climate forcing, trends, and evaluation of regional air pollution and validation of aerosol transport models over the study region.

scholarly journals Solar radiometer sensing of multi-year aerosol features over a tropical urban station: direct-Sun and inversion products

2020 ◽  
Vol 13 (10) ◽  
pp. 5569-5593
Author(s):  
Katta Vijayakumar ◽  
Panuganti C. S. Devara ◽  
Sunil M. Sonbawne ◽  
David M. Giles ◽  
Brent N. Holben ◽  
...  
Keyword(s):  
Significant Role ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Single Scattering ◽  
Aerosol Size Distribution ◽  
Spectral Variation ◽  
Study Region ◽  
Aerosol Radiative Forcing ◽  
And Inversion

Abstract. The AErosol RObotic NETwork (AERONET) is the most developed ground-based network for aerosol remote sensing and has been playing a significant role not only in monitoring air quality for protecting human health but also in assessing the radiative budget of our planet Earth. In this paper, we report the direct-Sun and inversion products, comprising of spectral variation of aerosol optical depth (AOD), associated Ångström exponent (AE), fine- and coarse-mode aerosol fractions, aerosol size distribution (ASD), refractive index (RI), asymmetry parameter (AP), single scattering albedo (SSA), aerosol radiative forcing (ARF) and columnar concentration of gas constituents such as water vapor (H2O), obtained from a Cimel Sun–sky radiometer, functioning in Pune, India, under the AERONET program since October 2004. These long-term measurements carried out from 2005 to 2015 could serve as an urban aerosol optical long-term average or climatology. The AOD long-term variations at all wavelengths, considered in the study, exhibited an increasing trend, implying year-to-year enhancement in aerosol loading. The mean seasonal variations in AOD from cloud-free days indicated greater values during the monsoon season, revealing dominance of hygroscopic aerosol particles over the station. Contribution by different aerosol types to AOD has also been deduced and discussed, and dominance of a mixed type of aerosols (44.85 %) found, followed by combination of biomass burning and urban industrial aerosols (22.57 %) compared to other types of aerosols during the study period. The long-term datasets, derived aerosol and trace gas products play a significant role in understanding aerosol climate forcing, trends and evaluation of regional air pollution and validation of aerosol transport models over the study region.

scholarly journals Diurnal aerosol variations do affect daily averaged radiative forcing under heavy aerosol loading observed in Hefei, China

2015 ◽  
Vol 8 (7) ◽  
pp. 2901-2907 ◽  
Author(s):  
Z. Wang ◽  
D. Liu ◽  
Y. Wang ◽  
Z. Wang ◽  
G. Shi
Keyword(s):  
Temporal Resolution ◽  
Radiative Forcing ◽  
Single Scattering ◽  
High Temporal Resolution ◽  
Diurnal Changes ◽  
Data Set ◽  
Time Resolved ◽  
Aerosol Radiative Forcing ◽  
Aerosol Loading

Abstract. A strong diurnal variation of aerosol has been observed in many heavily polluted regions in China. This variation could affect the direct aerosol radiative forcing (DARF) evaluation if the daily averaged value is used as normal rather than the time-resolved values. To quantify the effect of using the daily averaged DARF, 196 days of high temporal resolution ground-based data collected in SKYNET Hefei site during the period from 2007 to 2013 is used to perform an assessment. We demonstrate that strong diurnal changes of heavy aerosol loading have an impact on the 24-h averaged DARF when daily averaged optical properties are used to retrieve this quantity. The DARF errors varying from −7.6 to 15.6 W m−2 absolutely and from 0.1 to 28.5 % relatively were found between the calculations using daily average aerosol properties, and those using time-resolved aerosol observations. These errors increase with increasing daily aerosol optical depth (AOD) and decreasing daily single-scattering albedo (SSA), indicating that the high temporal resolution DARF data set should be used in the model instead of the normal daily-averaged one, especially under heavy aerosol loading conditions for regional campaign studies. We also found that statistical errors (0.3 W m−2 absolutely and 11.8 % relatively) will be less, which means that the effect of using the daily averaged DARF can be weakened by using a long-term observational data set.

scholarly journals A new approach for retrieving the UV–vis optical properties of ambient aerosols

2016 ◽  
Vol 9 (8) ◽  
pp. 3477-3490 ◽  
Author(s):  
Nir Bluvshtein ◽  
J. Michel Flores ◽  
Lior Segev ◽  
Yinon Rudich
Keyword(s):  
Optical Properties ◽  
Atmospheric Aerosols ◽  
Radiative Forcing ◽  
Complex Refractive Index ◽  
Single Scattering ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Ambient Aerosols ◽  
New Approach ◽  
Effective Radiative Forcing

Abstract. Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol–radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

scholarly journals Contrasting variation in aerosol optical properties during dust episodes in the Middle East and Southwest Asia: Model results and ground measurement

2019 ◽  
Vol 99 ◽  
pp. 04006
Author(s):  
Khan Alam ◽  
Maqbool Ahmad
Keyword(s):  
Middle East ◽  
Radiative Forcing ◽  
Single Scattering ◽  
Dust Storms ◽  
Radiative Properties ◽  
Southwest Asia ◽  
Gulf Region ◽  
Aerosol Radiative Forcing ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Using Data

Dust storms deteriorated air quality over the Gulf Region, Iraq, Iran, and Pakistan during the last decade. The purpose of this study is to investigate the changes in aerosol optical and radiative properties during a dust episode over the various locations in the Middle East and Southwest Asia using data from the MODerate resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic Network (AERONET) during March, 2012. Maximum aerosol optical depth (AOD) values were found to be 2.18, 1.30, 4.33 and 1.80 over Lahore, Kanpur, Kaust, and Mezaira, respectively. The Volume Size Distributions, Single Scattering Albedo, Refractive Index, and Asymmetry parameter indicated that coarse mode aerosols were predominant relative to fine mode aerosols during the dust event. The average shortwave aerosol radiative forcing (ARF) values at the earth’s surface were found to be -96±45 W m-2, -86±22 W m-2, -77±51 W m-2, and -75±40 W m-2, over Lahore, Kanpur, Kaust and Mezaira, respectively. Likewise, the averaged ARF values over Lahore, Kanpur, Kaust and Mezaira at the top of the atmosphere (TOA) were found to be -45±25 W m-2, -27±9 W m-2, -41±29 W m-2, and -75±40 W m-2, respectively. The large differences between surface and TOA forcing produced significant heating within the atmosphere.

scholarly journals Direct Aerosol Radiative Forcing Uncertainty Based on a Radiative Perturbation Analysis

2010 ◽  
Vol 23 (19) ◽  
pp. 5288-5293 ◽  
Author(s):  
Norman G. Loeb ◽  
Wenying Su
Keyword(s):  
Radiative Forcing ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Radiative Forcing ◽  
Clear Sky ◽  
Radiative Perturbation ◽  
Sky Conditions ◽  
Global Mean ◽  
Aerosol Properties ◽  
Aerosol Radiative

Abstract To provide a lower bound for the uncertainty in measurement-based clear- and all-sky direct aerosol radiative forcing (DARF), a radiative perturbation analysis is performed for the ideal case in which the perturbations in global mean aerosol properties are given by published values of systematic uncertainty in Aerosol Robotic Network (AERONET) aerosol measurements. DARF calculations for base-state climatological cloud and aerosol properties over ocean and land are performed, and then repeated after perturbing individual aerosol optical properties (aerosol optical depth, single-scattering albedo, asymmetry parameter, scale height, and anthropogenic fraction) from their base values, keeping all other parameters fixed. The total DARF uncertainty from all aerosol parameters combined is 0.5–1.0 W m−2, a factor of 2–4 greater than the value cited in the Intergovernmental Panel on Climate Change’s (IPCC’s) Fourth Assessment Report. Most of the total DARF uncertainty in this analysis is associated with single-scattering albedo uncertainty. Owing to the greater sensitivity to single-scattering albedo in cloudy columns, DARF uncertainty in all-sky conditions is greater than in clear-sky conditions, even though the global mean clear-sky DARF is more than twice as large as the all-sky DARF.

scholarly journals Retrieval of Key Aerosol Optical Parameters from Spectral Direct and Diffuse Irradiances Observed by a Radiometer with Nonideal Cosine Response Characteristic

2012 ◽  
Vol 29 (5) ◽  
pp. 683-696 ◽  
Author(s):  
Pradeep Khatri ◽  
Tamio Takamura ◽  
Akihiro Yamazaki ◽  
Yutaka Kondo
Keyword(s):  
Direct Effect ◽  
Radiative Forcing ◽  
Response Characteristic ◽  
Single Scattering ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Aerosol Direct Effect ◽  
Diffuse Irradiance ◽  
Isotropic Distribution ◽  
Sky Radiance

Abstract The spectral direct and diffuse irradiances observed by a radiometer with a horizontal surface detector have been frequently used to study aerosol optical parameters, such as aerosol optical thickness (τaer) and single scattering albedo (ω). Such radiometers more or less lack an ideal cosine response. Generally, either the cosine error of observed diffuse irradiance was corrected by assuming an isotropic distribution of sky radiance or it was neglected in the past studies. This study presents an algorithm to retrieve τaer and ω from direct and diffuse irradiances observed by a radiometer with a nonideal cosine response characteristic by taking into account the cosine errors of observed irradiances in detail. The proposed algorithm considers the anisotropic distribution of sky radiance while correcting the cosine error of observed diffuse irradiance. This algorithm can also be used to calculate the cosine error correction factor of diffuse irradiance. The results show that the aerosol optical parameters and the aerosol direct effect (aerosol radiative forcing and the heating rate) can be heavily affected by the cosine errors of observed direct and diffuse irradiances. The study further shows that assuming the isotropic distribution of sky radiance while correcting the cosine error of observed diffuse irradiance can affect the retrieved ω at small and large solar zenith angles; thus, the estimated aerosol direct effect can be quantitatively affected. Because of the cosine errors, this study found the actual values of diffuse irradiances at different wavelengths were underestimated by around 5%–11%.

scholarly journals Observations and Modeling of the Surface Aerosol Radiative Forcing during UAE2

2008 ◽  
Vol 65 (9) ◽  
pp. 2877-2891 ◽  
Author(s):  
K. M. Markowicz ◽  
P. J. Flatau ◽  
J. Remiszewska ◽  
M. Witek ◽  
E. A. Reid ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
Radiative Forcing ◽  
Sea Breeze ◽  
Single Scattering ◽  
Land Breeze ◽  
Gulf Region ◽  
Diurnal Variability ◽  
Aerosol Radiative Forcing ◽  
Aerosol Forcing ◽  
Aerosol Radiative

Abstract Aerosol radiative forcing in the Persian Gulf region is derived from data collected during the United Arab Emirates (UAE) Unified Aerosol Experiment (UAE2). This campaign took place in August and September of 2004. The land–sea-breeze circulation modulates the diurnal variability of the aerosol properties and aerosol radiative forcing at the surface. Larger aerosol radiative forcing is observed during the land breeze in comparison to the sea breeze. The aerosol optical properties change as the onshore wind brings slightly cleaner air. The mean diurnal value of the surface aerosol forcing during the UAE2 campaign is about −20 W m−2, which corresponds to large aerosol optical thickness (0.45 at 500 nm). The aerosol forcing efficiency [i.e., broadband shortwave forcing per unit optical depth at 550 nm, W m−2 (τ500)−1] is −53 W m−2 (τ500)−1 and the average single scattering albedo is 0.93 at 550 nm.

scholarly journals An exploration of ozone changes and their radiative forcing prior to the chlorofluorocarbon era

2002 ◽  
Vol 2 (5) ◽  
pp. 363-374 ◽  
Author(s):  
D. T. Shindell ◽  
G. Faluvegi
Keyword(s):  
Ozone Depletion ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Stratospheric Ozone ◽  
Data Sets ◽  
Independent Data ◽  
Spatial Coverage ◽  
Ozone Trends ◽  
Ozone Trend

Abstract. Using historical observations and model simulations, we investigate ozone trends prior to the mid-1970s onset of halogen-induced ozone depletion. Though measurements are quite limited, an analysis based on multiple, independent data sets (direct and indirect) provides better constraints than any individual set of observations. We find that three data sets support an apparent long-term stratospheric ozone trend of -7.2 ± 2.3 DU during 1957-1975, which modeling attributes primarily to water vapor increases. The results suggest that 20th century stratospheric ozone depletion may have been roughly 50% more than is generally supposed. Similarly, three data sets support tropospheric ozone increases over polluted Northern Hemisphere continental regions of 8.2 ± 2.1 DU during this period, which are mutually consistent with the stratospheric trends. As with paleoclimate data, which is also based on indirect proxies and/or limited spatial coverage, these results must be interpreted with caution. However, they provide the most thorough estimates presently available of ozone changes prior to the coincident onset of satellite data and halogen dominated ozone changes. If these apparent trends were real, the radiative forcing by stratospheric ozone since the 1950s would then have been -0.15 ± 0.05 W/m2, and -0.2 W/m2 since the preindustrial. For tropospheric ozone, it would have been 0.38 ± 0.10 W/m2 since the late 1950s. Combined with even a very conservative estimate of tropospheric ozone forcing prior to that time, this would be larger than current estimates since 1850 which are derived from models that are even less well constrained. These calculations demonstrate the importance of gaining a better understanding of historical ozone changes.

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