Arctic spring and summertime aerosol optical depth baseline from long-term observations and model reanalyses, with implications for the impact of regional biomass burning processes

Xian, Peng; Zhang, Jianglong; Toth, Travis D.; Sorenson, Blake; Colarco, Peter R.; Kipling, Zak; O’Neill, N. T.; Hyer, E. J.; Campell, James R.; Reid, Jeffrey S.; Ranjbar, Keyvan

doi:10.5194/acp-2021-805

Cited by 3 publications

(6 citation statements)

References 92 publications

(142 reference statements)

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“…For instance, measurements of aerosol optical properties in the Arctic provide high spatial and long-term climatological information important for model simulations, however remain mainly site-specific and do not often extend fully to the central Arctic Ocean [21][22][23] . Additionally, while land-based observatories, provide climatological information about Arctic particle size distribution and mass composition that is highly valuable for understanding Arctic aerosol processes and for modeling their climate effects [24][25][26] , they are not necessarily representative for aerosol characteristics and impacts over the remote central Arctic Ocean.…”

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confidence: 99%

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

et al. 2022

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Frequency and intensity of warm and moist air-mass intrusions into the Arctic have increased over the past decades and have been related to sea ice melt. During our year-long expedition in the remote central Arctic Ocean, a record-breaking increase in temperature, moisture and downwelling-longwave radiation was observed in mid-April 2020, during an air-mass intrusion carrying air pollutants from northern Eurasia. The two-day intrusion, caused drastic changes in the aerosol size distribution, chemical composition and particle hygroscopicity. Here we show how the intrusion transformed the Arctic from a remote low-particle environment to an area comparable to a central-European urban setting. Additionally, the intrusion resulted in an explosive increase in cloud condensation nuclei, which can have direct effects on Arctic clouds’ radiation, their precipitation patterns, and their lifetime. Thus, unless prompt actions to significantly reduce emissions in the source regions are taken, such intrusion events are expected to continue to affect the Arctic climate.

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confidence: 99%

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

et al. 2022

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“…As models and remote sensing products are gradually being combined in research [27,28], it is anticipated that coupled analyses will become a tool that is increasingly used in the community. This paper provides a comparative analysis of 550 nm AOD 550 , η 550, and corresponding FAOD 550 and CAOD 550 , from the perspectives of the two global operational products: (1) the Moderate Resolution Imaging Spectroradiometer (MODIS) Version 6.1 dark target (DT) aerosol retrievals (henceforth MODIS DT provided within Level 2 product known as MOD04/MYD04; [29]); (2) the corresponding consensus speciated AOD products drawn from International Cooperative for Aerosol Prediction Multi Model ensemble (ICAP-MME; [30,31]) with members that utilize MODIS total AOD in assimilation (i.e., generating the so-called "core four consensus" or C4C of the ICAP-MME).…”

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confidence: 99%

A Coupled Evaluation of Operational MODIS and Model Aerosol Products for Maritime Environments Using Sun Photometry: Evaluation of the Fine and Coarse Mode

et al. 2022

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Although satellite retrievals and data assimilation have progressed to where there is a good skill for monitoring maritime Aerosol Optical Depth (AOD), there remains uncertainty in achieving further degrees of freedom, such as distinguishing fine and coarse mode dominated species in maritime environments (e.g., coarse mode sea salt and dust versus fine mode terrestrial anthropogenic emissions, biomass burning, and maritime secondary production). For the years 2016 through 2019, we performed an analysis of 550 nm total AOD550, fine mode AOD (FAOD550; also known as FM AOD in the literature), coarse mode AOD (CAOD550), and fine mode fraction (η550) between Moderate Resolution Spectral Imaging Radiometer (MODIS) V6.1 MOD/MYD04 dark target aerosol retrievals and the International Cooperative for Aerosol Prediction (ICAP) core four multi-model consensus (C4C) of analyses/short term forecasts that assimilate total MODIS AOD550. Differences were adjudicated by the global shipboard Maritime Aerosol Network (MAN) and selected island AERONET sun photometer observations with the application of the spectral deconvolution algorithm (SDA). Through a series of conditional and regional analyses, we found divergence included regions of terrestrial influence and latitudinal dependencies in the remote oceans. Notably, MODIS and the C4C and its members, while having good correlations overall, have a persistent +0.04 to +0.02 biases relative to MAN and AERONET for typical AOD550 values (84th% < 0.28), with the C4C underestimating significant events thereafter. Second, high biases in AOD550 are largely associated with the attribution of the fine mode in satellites and models alike. Thus, both MODIS and C4C members are systematically overestimating AOD550 and FAOD550 but perform better in characterizing the CAOD550. Third, for MODIS, findings are consistent with previous reports of a high bias in the retrieved Ångström Exponent, and we diagnosed both the optical model and cloud masking as likely causal factors for the AOD550 and FAOD550 high bias, whereas for the C4C, it is likely from secondary overproduction and perhaps numerical diffusion. Fourth, while there is no wind-speed-dependent bias for surface winds <12 m s−1, the C4C and MODIS AOD550s also overestimate CAOD550 and FAOD550, respectively, for wind speeds above 12 m/s. Finally, sampling bias inherent in MAN, as well as other circumstantial evidence, suggests biases in MODIS are likely even larger than what was diagnosed here. We conclude with a discussion on how MODIS and the C4C products have their own strengths and challenges for a given climate application and discuss needed research.

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“…land and ocean. A few recent studies have used such AOD products (e.g., (Glantz et al, 2014;Wu et al, 2016;Sand et al, 2017;Xian et al, 2021)) over open ocean and snow-and ice free surfaces, and make a valuable contribution to closing the data gap mentioned above. However, these AOD products are not suitable over the cryosphere due to an inadequate parameterization of the surface reflectance over residual snow-and ice-covered areas (Mei et al, 2020a) and Arctic cloud cover (Jafariserajehlou et al, 2019).…”

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confidence: 99%

“…Thus far, there have been no attempts to apply these algorithms systematically in the Arctic cryosphere to fill the data gap, identified above. Studies using active satellite remote sensing such as Sand et al (2017) and Xian et al (2021) are valuable, but the observational data are limited over the Arctic cryosphere.…”

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confidence: 99%

“…Recently, Toth et al (2018) and Xian et al (2021) reported that the active satellite sensor, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP/CALIPSO) (Winker et al, 2004) has a significant fraction of aerosol profile data consisting of retrieval fill values (-9999s, or RFVs), due in part to the lidar's minimum detection limits. Indeed, in some areas in the Arctic, over 80% of CALIOP profiles consist solely of RFVs.…”

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confidence: 99%

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Spring and summertime aerosol optical depth retrieval over the Arctic cryosphere by using satellite observations

Swain

Vountas

Deroubaix

et al. 2023

Preprint

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Abstract. The Arctic climate has changed significantly over the past two to three decades. Aerosols play various roles in the radiative forcing in the Arctic, both directly and indirectly, depending on the changes in loading and composition. However, their observation from the ground or with airborne instruments is challenging and thus measurements are sparse. In this study, total Aerosol Optical Depth (AOD) is determined from top-of-atmosphere reflectance measurements by the Advanced Along-Track Scanning Radiometer (AATSR) aboard ENVISAT over snow and ice in the Arctic using a retrieval called AEROSNOW for the period 2003 to 2011. We use the dual-viewing capability of the AATSR instrument to reduce the impact of surface reflectance on the accuracy of AOD. The AOD is retrieved assuming that the surface reflectance observed by the satellite can be well-parametrized by a bidirectional snow reflectance distribution function, BRDF. The spatial distribution of AODs shows that high values in spring (March, April, May) and lower AOD values in summer (June, July, August) are well captured. Spaceborne AOD values are consistent with colocated AERONET measurements, with no systematic bias as a function of time. The AEROSNOW AOD in the high Arctic ( ≥ 72° N) was validated by comparison with ground-based measurements at the PEARL, OPAL, Hornsund, and Thule stations. The AEROSNOW AOD value is less than 0.15 on average and the regression to AERONET yields a slope of 0.98, a Pearson correlation coefficient of R = 0.86, and an RMSE = 0.01 at a monthly scale, both in spring and summer. These AOD results provide, for the first time, observational insights into the central Arctic with significant spatial and temporal coverage.

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Arctic spring and summertime aerosol optical depth baseline from long-term observations and model reanalyses, with implications for the impact of regional biomass burning processes

Cited by 3 publications

References 92 publications

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

A Coupled Evaluation of Operational MODIS and Model Aerosol Products for Maritime Environments Using Sun Photometry: Evaluation of the Fine and Coarse Mode

Spring and summertime aerosol optical depth retrieval over the Arctic cryosphere by using satellite observations

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