Aerosol radiative forcing during dust events over New Delhi, India

Impact of dust storms on the aerosol characteristics and radiative forcing over Patiala, northwestern India has been studied during April-June of 2010 using satellite observations and ground-based measurements. Six dust events (DE) have been identified during the study period with average values of Aqua-MODIS AOD550and Microtops-II AOD500over Patiala as1.00±0.51and0.84±0.41, respectively while Aura-OMI AI exhibits high values ranging from 2.01 to 6.74. The Ångström coefficients α380–870and β range from 0.12 to 0.31 and 0.95 to 1.40, respectively. The measured spectral AODs, the OPAC-derived aerosol properties and the surface albedo obtained from MODIS were used as main inputs in SBDART model for the calculation of aerosol radiative forcing (ARF) over Patiala. The ARF at surface (SRF) and top of atmosphere (TOA) ranges from ∼−50 to −100 Wm−2and from ∼−10 to −25 Wm−2, respectively during the maximum of dust storms. The radiative forcing efficiency was found to be −66 Wm−2AOD−1at SRF and −14 Wm−2AOD−1at TOA. High values of ARF in the atmosphere (ATM), ranging between ∼+40 Wm−2and +80.0 Wm−2during the DE days, might have significant effect on the warming of the lower and middle atmosphere and, hence, on climate over northwestern India.

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Aerosol radiative forcing during African desert dust events (2005–2010) over South-Eastern Spain

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-6593-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 6593-6622 ◽

Cited By ~ 4

Author(s):

A. Valenzuela ◽

F. J. Olmo ◽

H. Lyamani ◽

M. Antón ◽

A. Quirantes ◽

...

Keyword(s):

Radiative Transfer ◽

Radiative Forcing ◽

Single Scattering ◽

Radiative Transfer Model ◽

Transfer Model ◽

Aerosol Radiative Forcing ◽

Desert Dust ◽

Aerosol Parameter ◽

Dust Events ◽

Aerosol Radiative

Abstract. The instantaneous values of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated during desert dust events occurred at Granada (Southeastern Spain) from 2005 to 2010. For that, the SBDART radiative transfer model was utilized to simulate the global irradiance values (0.3–2.8 μm) at the surface and TOA using as input the aerosol properties derived from a CIMEL sun-photometer measurements and an inversion methodology that uses the sky radiance measurements in principal plane configuration and non-spherical particle shapes approximation. The SBDART modeled global irradiances at surface have been successfully validated against experimental measurements obtained by CM-11 pyranometer, indicating the reliability of the radiative transfer model used in this work for the ARF calculations. The monthly ARF values at surface ranged from −32 W m−2 to −46 W m−2, being larger in April and July than in the rest of months. The seasonal ARF evolution was inconsistent with seasonal aerosol optical depth (AOD) variation due to the effects induced by other aerosol parameter such as the single scattering albedo. The ARF at TOA changed from −9 W m−2 to −29 W m−2. Thus, the atmospheric ARF values (ARF at TOA minus ARF at surface) ranged from +15 to +35 W m−2. These results suggest that the African dust caused local atmospheric heating over the study location. The instantaneous aerosol radiative forcing efficiency (ARFE), aerosol radiative forcing per unit of AOD (440 nm), at surface and TOA during African desert dust events was evaluated according to the desert dust source origins. The ARFE values at surface were relatively high (in absolute term) and were −157 ± 20 (Sector A), −154 ± 23 (Sector B), and −147 ± 23 (Sector C) W m−2. These values were larger than many of the values found in literature which could be due to the presence of more absorbing atmospheric particles during African desert dust intrusions over our study area. Finally, our ARF computations showed good agreement with the corresponding ARF calculated by AERONET network.

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Aerosol radiative forcing during African desert dust events (2005–2010) over Southeastern Spain

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-10331-2012 ◽

2012 ◽

Vol 12 (21) ◽

pp. 10331-10351 ◽

Cited By ~ 72

Author(s):

A. Valenzuela ◽

F. J. Olmo ◽

H. Lyamani ◽

M. Antón ◽

A. Quirantes ◽

...

Keyword(s):

Radiative Forcing ◽

Radiative Transfer Model ◽

Transfer Model ◽

Aerosol Optical Properties ◽

Aerosol Radiative Forcing ◽

Desert Dust ◽

The Mean ◽

Dust Events ◽

Aerosol Properties ◽

Aerosol Radiative

Abstract. The daily (24 h) averages of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated during desert dust events over Granada (southeastern Spain) from 2005 to 2010. A radiative transfer model (SBDART) was utilized to simulate the solar irradiance values (0.31–2.8 μm) at the surface and TOA, using as input aerosol properties retrieved from CIMEL sun photometer measurements via an inversion methodology that uses the sky radiance measurements in principal plane configuration and a spheroid particle shape approximation. This inversion methodology was checked by means of simulated data from aerosol models, and the derived aerosol properties were satisfactorily compared against well-known AERONET products. Good agreement was found over a common spectral interval (0.2–4.0 μm) between the simulated SBDART global irradiances at surface and those provided by AERONET. In addition, simulated SBDART solar global irradiances at the surface have been successfully validated against CM-11 pyranometer measurements. The comparison indicates that the radiative transfer model slightly overestimates (mean bias of 3%) the experimental solar global irradiance. These results show that the aerosol optical properties used to estimate ARF represent appropriately the aerosol properties observed during desert dust outbreak over the study area. The ARF mean monthly values computed during desert dust events ranged from −13 ± 8 W m−2 to −34 ± 15 W m−2 at surface, from −4 ± 3 W m−2 to −13 ± 7 W m−2 at TOA and from +6 ± 4 to +21 ± 12 W m−2 in the atmosphere. We have checked if the differences found in aerosol optical properties among desert dust sectors translate to differences in ARF. The mean ARF at surface (TOA) were −20 ± 12 (−5 ± 5) W m−2, −21 ± 9 (−7 ± 5) W m−2 and −18 ± 9 (−6 ± 5) W m−2 for sector A (northern Morocco; northwestern Algeria), sector B (western Sahara, northwestern Mauritania and southwestern Algeria), and sector C (eastern Algeria, Tunisia), respectively. The Kolmogorov-Smirnov statistical test revealed that daily {ARF} values at TOA for sector A were significantly different from the other two sectors, likely as a result of the lower values of single scattering albedo obtained for sector A. The mean values of aerosol radiative forcing efficiency at surface (TOA) were −74 ± 12 W m−2 (−17 ± 7 W m−2) for sector A, −70 ± 14 W m−2 (−20 ± 9 W m−2) for sector B, and −65 ± 16 W m−2 (−22 ± 10 W m−2) for sector C, and thus comparable between the three sectors in all seasons.

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