A Three-Year Climatology of Cloud-Top Phase over the Southern Ocean and North Pacific

Morrison, Anthony Edward; Siems, Steven T.; Manton, M. J.

doi:10.1175/2010jcli3842.1

Cited by 82 publications

(82 citation statements)

References 26 publications

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“…In situ observations and surface remote sensing suggest that clouds in the mixedphase temperature range in mid-latitudes tend to consist almost entirely of ice or of liquid water [10,11,48]. This agrees with satellite observations over the Southern Ocean and North Pacific, which have shown that the most common cloud types are clouds with supercooled droplets at their tops [6,65]. Glaciated cloud tops at temperatures warmer than −20 • C are rare.…”

Section: Aerosol Effects On Stratiform and Shallow Convective Mpcssupporting

confidence: 85%

“…Glaciated cloud tops at temperatures warmer than −20 • C are rare. A large portion of cloud tops remains ambiguous from the MODIS satellite, which means they could be MPCs or have signals from multiple cloud layers [65]. On a global scale, the fraction of supercooled water in MPCs at various temperatures from the ECHAM6 and different versions of the CAM GCM has been compared to CALIOP satellite estimates.…”

Section: Aerosol Effects On Stratiform and Shallow Convective Mpcsmentioning

confidence: 99%

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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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Section: Aerosol Effects On Stratiform and Shallow Convective Mpcssupporting

confidence: 85%

Section: Aerosol Effects On Stratiform and Shallow Convective Mpcsmentioning

confidence: 99%

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Lohmann

2017

Curr Clim Change Rep

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“…4 illustrates the difference in CRE when the results of the Baseline simulation are subtracted from the NoMeyers + VapDep/100 simulation and extended out over the Southern Ocean. Effects are large over the Southern Ocean storm tracks, where in situ observations show there are significant regions of supercooled liquid (29,30). This is a different regime from the Antarctic because of the warmer temperatures (−20°C to −30 for shallow cloud tops) and the different aerosol populations [sea salt and biogenic aerosols (31)].…”

Section: Significancementioning

confidence: 99%

Impact of Antarctic mixed-phase clouds on climate

Lawson

Gettelman

2014

Proc. Natl. Acad. Sci. U.S.A.

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Precious little is known about the composition of low-level clouds over the Antarctic Plateau and their effect on climate. In situ measurements at the South Pole using a unique tethered balloon system and ground-based lidar reveal a much higher than anticipated incidence of low-level, mixed-phase clouds (i.e., consisting of supercooled liquid water drops and ice crystals). The high incidence of mixed-phase clouds is currently poorly represented in global climate models (GCMs). As a result, the effects that mixed-phase clouds have on climate predictions are highly uncertain. We modify the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) GCM to align with the new observations and evaluate the radiative effects on a continental scale. The net cloud radiative effects (CREs) over Antarctica are increased by +7.4 Wm , and although this is a significant change, a much larger effect occurs when the modified model physics are extended beyond the Antarctic continent. The simulations show significant net CRE over the Southern Ocean storm tracks, where recent measurements also indicate substantial regions of supercooled liquid. These sensitivity tests confirm that Southern Ocean CREs are strongly sensitive to mixed-phase clouds colder than −20°C.Antarctica | climate | mixed-phase | clouds C louds have a major impact on the Earth's radiative budget and climate change (1, 2), yet a dearth of microphysical data have been collected within clouds over the Antarctic Plateau. This lack of microphysical data is associated with challenges deploying and operating instrumentation in the world's harshest, most remote atmospheric environment (3). Clouds have a critical influence on the Antarctic ice sheet's radiation budget and surface mass balance and appear to affect synoptic-scale effects over the Southern Ocean (3-6). Early (1986) airborne lidar measurements of cloud properties over the Antarctic Plateau indicated that the clouds consisted entirely of ice crystals (7). Because supercooled water drops are more likely to freeze as the temperature approaches the homogenous freezing point, about −37°C in clouds (8), low-level Antarctic clouds, which are the coldest on Earth, have generally been treated as being all ice in numerical models. However, measurements reported in this article show that supercooled water drops can exist in low-level clouds at −32°C.Model sensitivity simulations demonstrate that uncertainties in the particle phase of Antarctic clouds can have a significant impact on the Antarctic continent, as well as even more farreaching effects. In the late 1990s, the National Center for Atmospheric Research (NCAR) Community Climate Model version 2 was run with the standard 10-μm water drop clouds and compared with the output when the particles were changed to ice. The results showed that changing from water drops to 10-μm ice crystals produced 1°-2°C temperature increases throughout the Antarctic troposphere (4). The microphysical properties of cloud particles can have a major impact on the...

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“…The third possible problem is that the cloud phases may be incorrect over the Southern Ocean. Analysis of observations from satellites (Morrison et al 2011) has shown the extensive presence of supercooled liquid water over the Southern Ocean region, particularly during summer, but the models may fail to predict large enough quantities of such supercooled liquid water in this Biases (W m -2 ) in LCRE (left column) and zonal mean distribution of LCRE (right) from three ACCESS model runs. The LCRE determined by ISCCP-FD is used as a benchmark.…”

Section: Wind Stressmentioning

confidence: 99%

Modifications to atmospheric physical parameterisations aimed at improving SST simulations in the ACCESS coupled model

Sun¹,

Franklin²,

Zhou³

et al. 2013

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The Australian Community Climate and Earth System Simulator (ACCESS) has been developed at the Centre for Australian Weather and Climate Research. It is a coupled modeling system consisting of ocean, atmosphere and land surface. The ACCESS atmospheric component is the UK Met Office Unified Model (UM). The initial results from the ACCESS coupled model had significant errors in the sea surface temperature (SST). It has been identified that the SST bias is largely due to errors in the representation of clouds. We have found that the use of the homogenous cloud distribution within model grid-boxes produced an underestimation of solar radiation reaching the surface, causing a cooling effect. The model cloud scheme PC2 does not produce enough high cloud cover, which also led to a cooling effect. These two deficiencies have been largely remedied by the implementation of the triple-cloud scheme and a modification to the ice cloud fraction parameterisation in the PC2 cloud scheme. We have also modified the air-sea flux exchange scheme to improve the simulation of ocean currents. These modifications have led to significant improvements in the simulation of SST in ACCESS.

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A Three-Year Climatology of Cloud-Top Phase over the Southern Ocean and North Pacific

Cited by 82 publications

References 26 publications

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Impact of Antarctic mixed-phase clouds on climate

Modifications to atmospheric physical parameterisations aimed at improving SST simulations in the ACCESS coupled model

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