Estimating the direct radiative effect of absorbing aerosols overlying marine boundary layer clouds in the southeast Atlantic using MODIS and CALIOP

Meyer, Kerry; Platnick, S.; Oreopoulos, Lazaros; Lee, Dongmin

doi:10.1002/jgrd.50449

Cited by 108 publications

(215 citation statements)

References 51 publications

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“…The corresponding maximum DREs for the SDD and MSD are higher by up to 3.6 W m −2 and lower by up to 1.1 W m −2 , respectively. Dust aerosols act like greenhouse gases (Miller and Tegen, 1998), trapping the outgoing terrestrial radiation while at the same time emitting radiation at longer wavelengths back to the ground and thus explaining the positive LW DREs for TOA (planetary warming) and NETSURF (surface warming). In addition, the aforementioned LW DREs (TOA and NET-SURF) covary with time, revealing that the sign and the magnitude of the LW DRE TOA are determined by the perturbation of the surface radiation budget (LW DRE NETSURF ) since the LW DRE ATM values are almost constant throughout the simulation period.…”

Section: Regional Mean Resultsmentioning

confidence: 99%

“…As a response to these disturbances, the surface heat fluxes, both sensible (SH) and latent (LE), associated with the transfer of energy (heat) and moisture between surface and atmosphere, also change in order to balance the gain or the loss of energy at the ground level (Miller and Tegen, 1998). Subsequently, variations of SH and LE have an impact on the components of the hydrological cycle (Miller et al, 2004b) as well as on the turbulent kinetic energy and momentum transfer which in turn affect near-surface winds and dust emission (Pérez et al, 2006).…”

Section: Impact On Sensible and Latent Heat Fluxesmentioning

confidence: 99%

“…Under clear skies, apart from mineral particles' optical properties, the shape (Wang et al, 2013a), the emitted dust size distribution (Mahowald et al, 2014), the surface albedo (Tegen et al, 2010) and the vertical distribution of dust aerosols (Mishra et al, 2015) have been recognized as determinant factors for the DRE calculation. On the contrary, when clouds are present, the position of dust layers with regards to clouds defines the sign and the magnitude of DREs at TOA (Yorks et al, 2009;Meyer et al, 2013;Choobari et al, 2014;Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Direct radiative effects during intense Mediterranean desert dust outbreaks

et al. 2018

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Abstract. The direct radiative effect (DRE) during 20 intense and widespread dust outbreaks, which affected the broader Mediterranean basin over the period March 2000-February 2013, has been calculated with the NMMB-MONARCH model at regional (Sahara and European continent) and shortterm temporal (84 h) scales. According to model simulations, the maximum dust aerosol optical depths (AODs) range from ∼ 2.5 to ∼ 5.5 among the identified cases. At midday, dust outbreaks locally induce a NET (shortwave plus longwave) strong atmospheric warming (DRE ATM values up to 285 W m −2 ; Niger-Chad; dust AODs up to ∼ 5.5) and a strong surface cooling (DRE NETSURF values down to −337 W m −2 ), whereas they strongly reduce the downward radiation at the ground level (DRE SURF values down to −589 W m −2 over the Eastern Mediterranean, for extremely high dust AODs, 4.5-5). During night-time, reverse effects of smaller magnitude are found. At the top of the atmosphere (TOA), positive (planetary warming) DREs up to 85 W m −2 are found over highly reflective surfaces (Niger-Chad; dust AODs up to ∼ 5.5) while negative (planetary cooling) DREs down to −184 W m −2 (Eastern Mediterranean; dust AODs 4.5-5) are computed over dark surfaces at noon. Dust outbreaks significantly affect the mean regional radiation budget, with NET DREs ranging from −8.5 to 0.5 W m −2 , from −31.6 to 2.1 W m −2 , from −22.2 to 2.2 W m −2 and from −1.7 to 20.4 W m −2 for TOA, SURF, NETSURF and ATM, respectively. Although the shortwave DREs are larger than the longwave ones, the latter are comparable or even larger at TOA, particularly over the Sahara at midday. As a response to the strong surface day-time cooling, dust outbreaks cause a reduction in the regional sensible and latent heat fluxes by up to 45 and 4 W m −2 , respectively, averaged over land areas of the simulation domain. Dust outbreaks reduce the temperature at 2 m by up to 4 K during day-time, whereas a reverse tendency of similar magnitude is found during nighttime. Depending on the vertical distribution of dust loads and time, mineral particles heat (cool) the atmosphere by up to 0.9 K (0.8 K) during day-time (night-time) within atmospheric dust layers. Beneath and above the dust clouds, mineral particles cool (warm) the atmosphere by up to 1.3 K (1.2 K) at noon (night-time). On a regional mean basis, negative feedbacks on the total emitted dust (reduced by 19.5 %) and dust AOD (reduced by 6.9 %) are found when dust interacts with the radiation. Through the consideration of dust radiative effects in numerical simulations, the model positive and negative biases for the downward surface SW or LW radiation, respectively, with respect to Baseline Surface Radiation Network (BSRN) measurements, are reduced. In addition, they also reduce the model near-surface (at 2 m) nocturnal cold biases by up to 0.5 K (regional averages), as well as the model warm biases at 950 and 700 hPa, where the dust concentration is maximized, by up to 0.4 K. However, improvements are relatively small and do not happen in all ...

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Section: Regional Mean Resultsmentioning

confidence: 99%

Section: Impact On Sensible and Latent Heat Fluxesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct radiative effects during intense Mediterranean desert dust outbreaks

et al. 2018

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“…On the one hand, the evaporation of cloud droplets caused by locally absorbing aerosol makes clouds thinner, which is a radiative effect. On the other hand, the presence of absorbing aerosol may influence the satellite-retrieved COT because it can absorb radiation and thus reduce the cloud reflectance measured by the sensors on the satellite (Meyer et al, 2013(Meyer et al, , 2015Ten Hoeve et al, 2011). Meyer et al (2013) reported that adjusting for above-cloud aerosol attenuation can increase the retrieved regional mean COT by roughly 18 % for polluted marine boundary layer clouds.…”

Section: Difference Between Separated and Mixed Conditionsmentioning

confidence: 99%

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

et al. 2017

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Abstract. Aerosol effects on low warm clouds over the Yangtze River Delta (YRD, eastern China) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA-Interim reanalysis data. This study shows that the relation between cloud properties and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD < 0.35 and AOD > 0.35). This applies to cloud droplet effective radius (CDR) and cloud fraction (CF), but not to cloud optical thickness (COT) and cloud top pressure (CTP). COT is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, CTP tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. It also shows that the COT-CDR and CWP (cloud liquid water path)-CDR relationships are not unique, but affected by atmospheric aerosol loading. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that aerosol-cloud interaction (ACI) is stronger for clouds mixed with smoke aerosol than for clouds mixed with dust, which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for various relative humidity and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity favours larger cloud droplet particles and increases cloud formation, irrespective of vertical or horizontal level. Stable atmospheric conditions enhance cloud cover horizontally. However, unstable atmospheric conditions favour thicker and higher clouds. Dynamically, upward motion of air parcels can also facilitate the formation of thicker and higher clouds. Overall, the present study provides an understanding of the impact of aerosols on cloud properties over the YRD. In addition to the amount of aerosol particles (or AOD), evidence is provided that aerosol types and ambient environmental conditions need to be considered to understand the observed relationships between cloud properties and AOD.

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“…Still, those parameters need to be used with caution. A thin layer of absorbing aerosol above clouds can trigger very high AI values especially for regions with optically thick clouds (Meyer et al, 2013;Yu et al, 2012;Alfaro-Contreras et al, 2014;Torres et al, 2012). Also, erroneously high MODIS AOD can be found over 20 cloud edges due to inaccurate cloud screening or cloud 3-D effects (Zhang et al, 2006;Shi et al, 2010).…”

Section: An Aerosol Algorithm For Heavy Smokementioning

confidence: 99%

Characterizing the 2015 Indonesia Fire Event Using Modified MODIS Aerosol Retrievals

Shi¹,

Levy²,

Eck³

et al. 2018

Preprint

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Abstract. The Indonesian fire and smoke event of 2015 was an extreme episode that affected public health and caused severe economic and environmental damage. The MODIS Dark Target (DT) aerosol algorithm, developed for global applications, significantly underestimated regional aerosol optical depth (AOD) during this episode. The larger-than-globalaveraged uncertainties in DT product over this event were due to both an overly zealous set of masks that mistook heavy smoke plumes for clouds and/or inland water, and also an aerosol model developed for generic global aerosol conditions. 15Using Aerosol Robotic Network (AERONET) Version 3 sky inversions of local AERONET stations, we created a specific aerosol model for the extreme event. Thus, using this new less-absorbing aerosol model, cloud masking based on results of the MODIS cloud optical properties algorithm, and relaxed thresholds on both inland water tests and upper limits of the AOD retrieval we created a research algorithm, and applied it to 80 appropriate MODIS granules during the event.Collocating and comparing with AERONET AOD shows that the research algorithm doubles the number of MODIS 20 retrievals greater than 1.0, while also significantly improving agreement with AERONET. The final results show that the operational DT algorithm had missed approximately 0.22 of the regional mean AOD, but as much as AOD = 3.0 for individual 0.5° grid boxes. This amount of missing AOD can skew the perception of the severity of the event, affect estimates of regional aerosol forcing, and alter aerosol modeling and forecasting that assimilate MODIS aerosol data products. These results will influence the future development of the global DT aerosol algorithm. 25

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Estimating the direct radiative effect of absorbing aerosols overlying marine boundary layer clouds in the southeast Atlantic using MODIS and CALIOP

Cited by 108 publications

References 51 publications

Direct radiative effects during intense Mediterranean desert dust outbreaks

Direct radiative effects during intense Mediterranean desert dust outbreaks

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

Characterizing the 2015 Indonesia Fire Event Using Modified MODIS Aerosol Retrievals

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