Observations of aerosol‐induced convective invigoration in the tropical east Atlantic

Storer, R. L.; Heever, Susan C. van den; L’Ecuyer, Tristan

doi:10.1002/2013jd020272

Cited by 59 publications

(64 citation statements)

References 51 publications

(124 reference statements)

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“…Deep convective cloud invigoration by aerosols has been shown in observational (Andreae et al, 2004;Koren et al, 2005;Storer et al, 2014) and modeling Lee et al, 2008) studies. Special attention has been given to the mixed and cold processes, for which smaller supercooled droplets are likely to freeze at lower temperatures (Rosenfeld and Woodley, 2000).…”

Section: Q Chen Et Al: How Do Changes In Warm-phase Microphysics Afmentioning

confidence: 94%

“…Therefore, the freezing latent heat will be released higher in the atmosphere, further enhancing convection (Han et al, 2012;Koren et al, 2008;Lynn et al, 2007;Rosenfeld et al, 2008;Tao et al, 2007). The intensified convection in the polluted environment increases cloud top height and enlarges the cloud cover in the upper troposphere due to a larger number of small-size ice crystals at those altitudes that settle slowly (Fan et al, 2013;Koren et al, 2010;Lee and Feingold, 2013;Morrison and Grabowski, 2011;Storer et al, 2014). The larger amount of supercooled droplets has been suggested as one of the critical elements in the cloud invigoration chain of events, and it depends on the upward transport of liquid mass across the zero temperature level (ZTL).…”

Section: Q Chen Et Al: How Do Changes In Warm-phase Microphysics Afmentioning

confidence: 99%

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How do changes in warm-phase microphysics affect deep convective clouds?

et al. 2017

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Abstract. Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: "How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems?" To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility.These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.

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Section: Q Chen Et Al: How Do Changes In Warm-phase Microphysics Afmentioning

confidence: 94%

Section: Q Chen Et Al: How Do Changes In Warm-phase Microphysics Afmentioning

confidence: 99%

How do changes in warm-phase microphysics affect deep convective clouds?

et al. 2017

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“…Freezing releases latent heat aloft and invigorates these cloud systems [47], but also in the lower levels of the cloud more latent heat is released by enhanced condensational growth [88,93]. This is partly counteracted by the reduced buoyancy due to increased water loading.…”

Section: Aerosol Effects On Deep Convective Cloudsmentioning

confidence: 99%

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Lohmann

2017

Curr Clim Change Rep

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Aerosol effects on mixed-phase clouds (MPCs) are more complex than in warm clouds because aerosol particles can act both as cloud condensation nuclei and as ice nucleating particles and more microphysical pathways exist. Stratiform MPCs are most prevalent in the Arctic where cloud top cooling enables heterogeneous ice formation and in orographic terrain where large updrafts prevail. Recently, aerosol effects on stratiform MPCs have also been considered in global climate models. The estimated effective aerosol radiative forcing due to aerosol-cloud and aerosol-radiation interactions (ERFaci+ari) at the top-ofthe-atmosphere (TOA) in stratiform warm and MPCs, which is an update of the estimate given in the fifth assessment report (AR5) of the Intergovernmental Panel of Climate Change, is −1.2 W m −2 with a 5-95 % range between −0.8 and −2.0 W m −2 . Since AR5, only one new estimate of ERFaci+ari including aerosol effects on both stratiform and convective clouds of −1.4 W m −2 has been published. In all cases, ERFaci+ari is dominated by changes in the shortwave TOA radiation with changes in the longwave TOA radiation amounting to 0.15 W m −2 .

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“…Satellite measurements have also been used to quantify the AIV over the Amazon basin (Lin et al, 2006), over the Atlantic Ocean (Koren et al, 2005;Storer et al, 2014), and over the entire global tropics (Niu and Li, 2012). The AIV occurs only under certain microphysical, dynamic and thermodynamic conditions Khain et al, , 2005Khain et al, , 2008Wang, 2005;Seifert and Beheng, 2006;van den Heever et al, 2006;Fan et al, 2007Fan et al, , 2009).…”

Section: Introductionmentioning

confidence: 99%

Long-term aerosol-mediated changes in cloud radiative forcing of deep clouds at the top and bottom of the atmosphere over the Southern Great Plains

Yan

Huang

et al. 2014

Atmos. Chem. Phys.

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Abstract. Aerosols can alter the macro-and micro-physical properties of deep convective clouds (DCCs) and their radiative forcing (CRF). This study presents what is arguably the first long-term estimate of the aerosol-mediated changes in CRF (AMCRF) for deep cloud systems derived from decade-long continuous ground-based and satellite observations, model simulations, and reanalysis data. Measurements were made at the US Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Satellite retrievals are from the Geostationary Operational Environmental Satellite. Increases in aerosol loading were accompanied by the thickening of DCC cores and the expansion and thinning of anvils, due presumably to the aerosol invigoration effect (AIV) and the aerosol microphysical effect. Meteorological variables dictating these cloud processes were investigated. Consistent with previous findings, the AIV is most significant when the atmosphere is moist and unstable with weak wind shear. Such aerosol-mediated systematic changes in DCC core thickness and anvil size alter CRF at the top of atmosphere (TOA) and at the surface. Using extensive observations, ∼ 300 DCC systems were identified over a 10 years period at the SGP site (2000-2011) and analyzed. Daily mean AMCRF at the TOA and at the surface are 29.3 W m −2 and 22.2 W m −2 , respectively. This net warming effect due to changes in DCC microphysics offsets the cooling resulting from the first aerosol indirect effect.

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Observations of aerosol‐induced convective invigoration in the tropical east Atlantic

Cited by 59 publications

References 51 publications

How do changes in warm-phase microphysics affect deep convective clouds?

How do changes in warm-phase microphysics affect deep convective clouds?

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Long-term aerosol-mediated changes in cloud radiative forcing of deep clouds at the top and bottom of the atmosphere over the Southern Great Plains

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