scholarly journals Impact of aerosol direct effect on East Asian air quality during the EAST-AIRE campaign

2016 ◽  
Vol 121 (11) ◽  
pp. 6534-6554 ◽  
Author(s):  
Jing Wang ◽  
Dale J. Allen ◽  
Kenneth E. Pickering ◽  
Zhanqing Li ◽  
Hao He
Keyword(s):  
Air Quality ◽  
Direct Effect ◽  
East Asian ◽  
Aerosol Direct Effect

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 A review of measurement-based assessment of aerosol direct radiative effect and forcing

2005 ◽  
Vol 5 (4) ◽  
pp. 7647-7768 ◽  
Author(s):  
H. Yu ◽  
Y. J. Kaufman ◽  
M. Chin ◽  
G. Feingold ◽  
L. A. Remer ◽  
...  
Keyword(s):  
Direct Effect ◽  
Global Ocean ◽  
Radiative Effect ◽  
Anthropogenic Aerosols ◽  
Annual Average ◽  
Model Simulations ◽  
Aerosol Forcing ◽  
Aerosol Direct Effect ◽  
Aerosol Absorption ◽  
Satellite Retrievals

Abstract. Aerosols affect the Earth's energy budget ''directly'' by scattering and absorbing radiation and ''indirectly'' by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Here we assess the aerosol optical depth, direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. The multi-spectral MODIS measures global distributions of aerosol optical thickness (τ) on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21% is contributed by human activities, as determined by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOT of 0.23 over global land with an uncertainty of ~20% or ± 0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global ocean. A number of measurement-based approaches estimate the clear-sky DRE (on solar radiation) at the top-of-atmosphere (TOA) to be about −5.5±0.2 Wm−2 (median ± standard error) over global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to −5.0 Wm−2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and at the ocean surface are currently realized through a combination of satellite retrievals, surface measurements, and model simulations, and are less constrained. Over the ocean surface, the DRE is estimated to be −8.8±0.4 Wm-2. Over land, an integration of satellite retrievals and model simulations derives a DRE of −4.9±0.7 Wm−2 and −11.8±1.9 Wm−2 at the TOA and surface, respectively. CTM simulations derive a wide range of DRE estimates that on average are smaller than the measurement-based DRE by about 30–40%, even after accounting for thin cirrus and cloud contamination. Despite these achievements, a number of issues remain open and more efforts are required to address them. Current estimates of the aerosol direct effect over land are poorly constrained. Uncertainties of DRE estimates are also larger on regional scales than on a global scale and large discrepancies exist between different approaches. The characterization of aerosol absorption and vertical distribution remains challenging. The aerosol direct effect in the thermal infrared range and under cloudy condition remains relatively unexplored and quite uncertain, because of a lack of global systematic aerosol vertical profile measurements. A coordinated research strategy needs to be developed for integration and assimilation of satellite measurements into models to constrain model simulations. Hopefully, enhanced measurement capabilities in the next few years and high-level scientific cooperation, will further advance our knowledge.

scholarly journals Comparison of PM2.5 Chemical Components over East Asia Simulated by the WRF-Chem and WRF/CMAQ Models: On the Models’ Prediction Inconsistency

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 618 ◽  
Author(s):  
Choi ◽  
Lee ◽  
Woo ◽  
Kim ◽  
Lee
Keyword(s):  
Air Quality ◽  
East Asia ◽  
East Asian ◽  
Temporal Distribution ◽  
Policy Support ◽  
Weather Research And Forecasting ◽  
Chemical Components ◽  
Atmospheric Concentration ◽  
Quality Models ◽  
Weather Research

High levels of atmospheric concentration of PM2.5 (particulate matters less than 2.5 μm in size) are one of the most urgent societal issues over the East Asian countries. Air quality models have been used as an essential tool to predict spatial and temporal distribution of the PM2.5 and to support relevant policy making. This study aims to investigate the performance of high-fidelity air quality models in simulating surface PM2.5 chemical composition over the East Asia region in terms of a prediction consistency, which is a prerequisite for accurate air quality forecasts and reliable policy decision. The WRF-Chem (Weather Research and Forecasting-Chemistry) and WRF/CMAQ (Weather Research and Forecasting/Community Multiscale Air Quality modeling system) models were selected and uniquely configured for a one-month simulation by controlling surface emissions and meteorological processes (model options) to investigate the prediction consistency focusing the analyses on the effects of meteorological and chemical processes. The results showed that the surface PM2.5 chemical components simulated by both the models had significant inconsistencies over East Asia ranging fractional differences of 53% ± 30% despite the differences in emissions and meteorological fields were minimal. The models’ large inconsistencies in the surface PM2.5 concentration were attributed to the significant differences in each model’s chemical responses to the meteorological variables, which were identified from the multiple linear regression analyses. Our findings suggest that the significant models’ prediction inconsistencies should be considered with a great caution in the PM2.5 forecasts and policy support over the East Asian region.

scholarly journals A review of measurement-based assessments of the aerosol direct radiative effect and forcing

2006 ◽  
Vol 6 (3) ◽  
pp. 613-666 ◽  
Author(s):  
H. Yu ◽  
Y. J. Kaufman ◽  
M. Chin ◽  
G. Feingold ◽  
L. A. Remer ◽  
...  
Keyword(s):  
Direct Effect ◽  
Global Ocean ◽  
Radiative Effect ◽  
Anthropogenic Aerosols ◽  
Annual Average ◽  
Model Simulations ◽  
Aerosol Forcing ◽  
Aerosol Direct Effect ◽  
Aerosol Absorption ◽  
Satellite Retrievals

Abstract. Aerosols affect the Earth's energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Our goal is to assess current observational capabilities and identify uncertainties in the aerosol direct forcing through comparisons of different methods with independent sources of uncertainties. Here we assess the aerosol optical depth (τ), direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. The multi-spectral MODIS measures global distributions of aerosol optical depth (τ) on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21%±7% is contributed by human activities, as estimated by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOD of 0.23 over global land with an uncertainty of ~20% or ±0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global the ocean. A number of measurement-based approaches estimate the clear-sky DRE (on solar radiation) at the top-of-atmosphere (TOA) to be about -5.5±0.2 Wm-2 (median ± standard error from various methods) over the global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to -5.0 Wm-2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and at the ocean surface are currently realized through a combination of satellite retrievals, surface measurements, and model simulations, and are less constrained. Over the oceans the surface DRE is estimated to be -8.8±0.7 Wm-2. Over land, an integration of satellite retrievals and model simulations derives a DRE of -4.9±0.7 Wm-2 and -11.8±1.9 Wm-2 at the TOA and surface, respectively. CTM simulations derive a wide range of DRE estimates that on average are smaller than the measurement-based DRE by about 30-40%, even after accounting for thin cirrus and cloud contamination. A number of issues remain. Current estimates of the aerosol direct effect over land are poorly constrained. Uncertainties of DRE estimates are also larger on regional scales than on a global scale and large discrepancies exist between different approaches. The characterization of aerosol absorption and vertical distribution remains challenging. The aerosol direct effect in the thermal infrared range and in cloudy conditions remains relatively unexplored and quite uncertain, because of a lack of global systematic aerosol vertical profile measurements. A coordinated research strategy needs to be developed for integration and assimilation of satellite measurements into models to constrain model simulations. Enhanced measurement capabilities in the next few years and high-level scientific cooperation will further advance our knowledge.

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