scholarly journals Contribution of ammonium nitrate to aerosol optical depth and direct radiative forcing by aerosols over East Asia

2014 ◽  
Vol 14 (4) ◽  
pp. 2185-2201 ◽  
Author(s):  
R. S. Park ◽  
S. Lee ◽  
S.-K. Shin ◽  
C. H. Song
Keyword(s):  
East Asia ◽  
Ammonium Nitrate ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
East Asian ◽  
Annual Average ◽  
Clear Sky ◽  
Direct Radiative Forcing ◽  
Sky Conditions

Abstract. This study focused on the contribution of ammonium nitrate (NH4NO3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, chemistry-transport model (CTM)-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique, over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties, the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH4NO3 to AOD and DRF by aerosols (ΦAOD and ΦDRF) were estimated for the four seasons of 2006 over East Asia. Both ΦAOD and ΦDRF showed seasonal variations over East Asia within the ranges between 4.7% (summer) and 31.3% (winter) and between 4.7% (summer) and 30.7% (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6% and 15.3%. Under all-sky conditions, ΦDRF varied between 3.6% (summer) and 24.5% (winter), showing annual average contribution of 12.1% over East Asia. These annual average contributions of NH4NO3 to AOD and DRF are almost comparable to the annual average mass fractions of NH4NO3 in PM2.5 and PM10 (17.0% and 14.0%, respectively). ΦAOD and ΦDRF were even larger in the locations where NH3 and NOx emission rates are strong, such as the central East China (CEC) region and Sichuan Basin. For example, under clear-sky conditions, both ΦAOD and ΦDRF over the CEC region range between 6.9% (summer) and 47.9% (winter) and between 6.7% (summer) and 47.5% (winter), respectively. Based on this analysis, it was concluded that both ΦAOD and ΦDRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.

scholarly journals Contribution of ammonium nitrate to aerosol optical depth and direct radiative forcing by aerosols over East Asia

2013 ◽  
Vol 13 (7) ◽  
pp. 19193-19235
Author(s):  
R. S. Park ◽  
S. J. Lee ◽  
S.-K. Shin ◽  
C. H. Song
Keyword(s):  
East Asia ◽  
Ammonium Nitrate ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
East Asian ◽  
Annual Average ◽  
Clear Sky ◽  
Direct Radiative Forcing ◽  
Sky Conditions

Abstract. This study focused on the contribution of ammonium nitrate (NH4NO3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, CTM-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique, over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties, the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH4NO3 to AOD and DRF by aerosols (ΦAOD and ΦDRF) were estimated for four seasons of 2006 over East Asia. Both ΦAOD and ΦDRF showed seasonal variations over East Asia within the ranges between 4.7% (summer) and 31.3% (winter) and between 4.7% (summer) and 30.7% (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6% and 15.3%. Under all-sky conditions, ΦDRF varied between 3.6% (summer) and 24.5% (winter), showing annual average contribution of 12.1% over East Asia. These annual average contributions of NH4NO3 to AOD and DRF are almost comparable to the annual average mass fractions of NH4NO3 to PM2.5 and PM10 (17.0% and 14.0%, respectively). ΦAOD and ΦDRF were even larger in the locations where NH3 and NOx emission rates are strong like the Central East China (CEC) region and Sichuan basin. For example, under clear-sky conditions, both ΦAOD and ΦDRF over the CEC region range between 6.9% (summer) and 47.9% (winter) and between 6.7% (summer) and 47.5% (winter), respectively. Based on this analysis, it was concluded that both ΦDRF and ΦDRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.

scholarly journals Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations

2006 ◽  
Vol 6 (12) ◽  
pp. 5225-5246 ◽  
Author(s):  
M. Schulz ◽  
C. Textor ◽  
S. Kinne ◽  
Y. Balkanski ◽  
S. Bauer ◽  
...  
Keyword(s):  
Optical Depth ◽  
Mass Extinction ◽  
Radiative Forcing ◽  
Residence Times ◽  
Atmospheric Forcing ◽  
Annual Average ◽  
Extinction Coefficients ◽  
Clear Sky ◽  
Direct Radiative Forcing ◽  
The Difference

Abstract. Nine different global models with detailed aerosol modules have independently produced instantaneous direct radiative forcing due to anthropogenic aerosols. The anthropogenic impact is derived from the difference of two model simulations with prescribed aerosol emissions, one for present-day and one for pre-industrial conditions. The difference in the solar energy budget at the top of the atmosphere (ToA) yields a new harmonized estimate for the aerosol direct radiative forcing (RF) under all-sky conditions. On a global annual basis RF is −0.22 Wm−2, ranging from +0.04 to −0.41 Wm−2, with a standard deviation of ±0.16 Wm−2. Anthropogenic nitrate and dust are not included in this estimate. No model shows a significant positive all-sky RF. The corresponding clear-sky RF is −0.68 Wm−2. The cloud-sky RF was derived based on all-sky and clear-sky RF and modelled cloud cover. It was significantly different from zero and ranged between −0.16 and +0.34 Wm−2. A sensitivity analysis shows that the total aerosol RF is influenced by considerable diversity in simulated residence times, mass extinction coefficients and most importantly forcing efficiencies (forcing per unit optical depth). The clear-sky forcing efficiency (forcing per unit optical depth) has diversity comparable to that for the all-sky/ clear-sky forcing ratio. While the diversity in clear-sky forcing efficiency is impacted by factors such as aerosol absorption, size, and surface albedo, we can show that the all-sky/clear-sky forcing ratio is important because all-sky forcing estimates require proper representation of cloud fields and the correct relative altitude placement between absorbing aerosol and clouds. The analysis of the sulphate RF shows that long sulphate residence times are compensated by low mass extinction coefficients and vice versa. This is explained by more sulphate particle humidity growth and thus higher extinction in those models where short-lived sulphate is present at lower altitude and vice versa. Solar atmospheric forcing within the atmospheric column is estimated at +0.82±0.17 Wm−2. The local annual average maxima of atmospheric forcing exceed +5 Wm−2 confirming the regional character of aerosol impacts on climate. The annual average surface forcing is −1.02±0.23 Wm−2. With the current uncertainties in the modelling of the radiative forcing due to the direct aerosol effect we show here that an estimate from one model is not sufficient but a combination of several model estimates is necessary to provide a mean and to explore the uncertainty.

Development of RAMS-CMAQ to Simulate Aerosol Optical Depth and Aerosol Direct Radiative Forcing and Its Application to East Asia

2009 ◽  
Vol 2 (6) ◽  
pp. 368-375 ◽  
Author(s):  
Han Xiao ◽  
Zhange Mei-Gen ◽  
Liu Xiao-Hong ◽  
Steven Ghan ◽  
Xin Jin-Yuan ◽  
...  
Keyword(s):  
East Asia ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Direct Radiative Forcing

scholarly journals Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations

2006 ◽  
Vol 6 (3) ◽  
pp. 5095-5136 ◽  
Author(s):  
M. Schulz ◽  
C. Textor ◽  
S. Kinne ◽  
Y. Balkanski ◽  
S. Bauer ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Radiative Forcing ◽  
Residence Times ◽  
Anthropogenic Aerosols ◽  
Annual Average ◽  
Lower Altitude ◽  
Extinction Coefficients ◽  
Clear Sky ◽  
Direct Radiative Forcing ◽  
The Difference

Abstract. Nine different global models with detailed aerosol modules have independently produced instantaneous direct radiative forcing due to anthropogenic aerosols. The anthropogenic impact is derived from the difference of two model simulations with identically prescribed aerosol emissions, one for present-day and one for pre-industrial conditions. The difference in the energy budget at the top of the atmosphere (ToA) yields a new harmonized estimate for the aerosol direct radiative forcing (RF) under all-sky conditions. On a global annual basis RF is –0.2 Wm-2, with a standard deviation of ±0.2 Wm-2. Anthropogenic nitrate and dust are not included in this estimate. No model shows a significant positive all-sky RF. The corresponding clear-sky RF is –0.6 Wm-2. The cloud-sky RF was derived based on all-sky and clear-sky RF and modelled cloud cover. It was significantly different from zero and ranged between –0.16 and +0.34 Wm-2. A sensitivity analysis shows that the total aerosol RF is influenced by considerable diversity in simulated residence times, mass extinction coefficients and most importantly forcing efficiencies (forcing per unit optical depth). Forcing efficiency differences among models explain most of the variability, mainly because all-sky forcing estimates require proper representation of cloud fields and the correct relative altitude placement between absorbing aerosol and clouds. The analysis of the sulphate RF shows that differences in sulphate residence times are compensated by opposite mass extinction coefficients. This is explained by more sulphate particle humidity growth and thus higher extinction in models with short-lived sulphate present at lower altitude and vice versa. Solar absorption within the atmospheric column is estimated at +0.85 Wm-2. The local annual average maxima of atmospheric forcing exceed +5 Wm-2 confirming the regional character of aerosol impacts on climate. The annual average surface forcing is –1.03 Wm-2.

scholarly journals Analysis on the impact of aerosol optical depth on surface solar radiation in the Shanghai megacity, China

2011 ◽  
Vol 11 (7) ◽  
pp. 3281-3289 ◽  
Author(s):  
J. Xu ◽  
C. Li ◽  
H. Shi ◽  
Q. He ◽  
L. Pan
Keyword(s):  
Solar Radiation ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Decadal Variation ◽  
Surface Solar Radiation ◽  
Atmospheric Transparency ◽  
Clear Sky ◽  
Term Variation ◽  
Sky Conditions

Abstract. This study investigated the decadal variation of the direct surface solar radiation (DiSR) and the diffuse surface solar radiation (DfSR) during 1961–2008 in the Shanghai megacity as well as their relationships to Aerosol Optical Depth (AOD) under clear-sky conditions. Three successive periods with unique features of long term variation of DiSR were identified for both clear-sky and all-sky conditions: a "dimming" period from the late 1960s to the mid 1980s, a "stabilization"/"slight brightening" period from the mid 1980s to the mid 1990s, and a "renewed dimming" period thereafter. During the two dimming periods of DiSR, DfSR brightened significantly under clear-sky conditions, indicating that change in atmospheric transparency resulting from aerosol emission has an important role on decadal variation of surface solar radiation (SSR) over this area. The analysis on the relationship between the Moderate-resolution Imaging Spectroradiometer (MODIS) retrieved AOD and the corresponding hourly measurements of DiSR and DfSR under clear-sky conditions clearly revealed that AOD is significantly correlated and anti-correlated with DfSR and DiSR, respectively, both above 99% confidence in all seasons, indicating the great impact of aerosols on SSR through absorption and/or scattering in the atmosphere. In addition, both AOD and the corresponding DiSR and DfSR measured during the satellite passage over Shanghai show obvious weekly cycles. On weekends, AOD is lower than the weekly average, corresponding to higher DiSR and lower DfSR, while the opposite pattern was true for weekdays. Less AOD on weekends due to the reduction of transportation and industrial activities results in enhancement of atmospheric transparency under cloud free conditions so as to increase DiSR and decrease DfSR simultaneously. Results show that aerosol loading from the anthropogenic emissions is an important modulator for the long term variation of SSR in Shanghai.

scholarly journals Atmospheric effect on the ground-based measurements of broadband surface albedo

2012 ◽  
Vol 5 (11) ◽  
pp. 2675-2688 ◽  
Author(s):  
T. Manninen ◽  
A. Riihelä ◽  
G. de Leeuw
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Surface Albedo ◽  
Test Site ◽  
Empirical Method ◽  
Atmospheric Conditions ◽  
Atmospheric Effect ◽  
Clear Sky ◽  
Using Data ◽  
Sky Conditions

Abstract. Ground-based pyranometer measurements of the (clear-sky) broadband surface albedo are affected by the atmospheric conditions (mainly by aerosol particles, water vapour and ozone). A new semi-empirical method for estimating the magnitude of the effect of atmospheric conditions on surface albedo measurements in clear-sky conditions is presented. Global and reflected radiation and/or aerosol optical depth (AOD) at two wavelengths are needed to apply the method. Depending on the aerosol optical depth and the solar zenith angle values, the effect can be as large as 20%. For the cases we tested using data from the Cabauw atmospheric test site in the Netherlands, the atmosphere caused typically up to 5% overestimation of surface albedo with respect to corresponding black-sky surface albedo values.

scholarly journals Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth

2013 ◽  
Vol 13 (11) ◽  
pp. 5647-5654 ◽  
Author(s):  
A. di Sarra ◽  
D. Fuà ◽  
D. Meloni
Keyword(s):  
Water Vapour ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Spectral Range ◽  
Radiative Forcing ◽  
Oscillation Amplitude ◽  
Aerosol Layer ◽  
Surface Irradiance ◽  
Perturbation Versus ◽  
Direct Radiative Forcing

Abstract. Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi-periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer, as also confirmed by satellite images. The wave occurred during a Saharan dust event. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation of the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e., the radiative perturbation of the net surface irradiance produced by a unit of optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at about 60° solar zenith angle is −(181 ± 17) W m−2 in the shortwave, and −(83 ± 7) W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively.

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