Observations of Ice Nucleating Particles Over Southern Ocean Waters

McCluskey, Christina S.; Hill, Thomas C. J.; Humphries, Ruhi S.; Rauker, Anne Marie; Moreau, Sébastien; Strutton, Peter G.; Chambers, Scott D.; Williams, Alastair G.; McRobert, Ian M.; Ward, Jason; Keywood, Melita; Harnwell, James; Ponsonby, Will A.; Loh, Zoë; Krummel, P. B.; Protat, Alain; Kreidenweis, Sonia M.; DeMott, Paul J.

doi:10.1029/2018gl079981

Cited by 149 publications

(244 citation statements)

References 49 publications

(100 reference statements)

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“…PDFs of rainfall rate and DSD parameters (N o * , D m , μ 0 , σ m , and σ' m ) were then analyzed in different latitude bands to identify differences in rainfall properties within the high-latitude bands. The S-highlat and N-polar bands clearly stood out as regions with systematically higher (lower) frequency of occurrence of rainfall rates below (above) 1 mm h −1 , and much lower normalized concentrations N o * , which is consistent with (and therefore possibly linked to) much lower cloud condensation nuclei and ice nucleating particles concentrations observed within pristine high-latitude air masses (e.g., McCluskey et al, 2018). Major differences were also found between latitudes for the μ 0 shape parameter, with high-latitude and midlatitude μ 0 ranging from −1 to +1 and polar and tropical μ 0 ranging from 2 to 5.…”

Section: Discussionmentioning

confidence: 99%

The Latitudinal Variability of Oceanic Rainfall Properties and Its Implication for Satellite Retrievals: 1. Drop Size Distribution Properties

et al. 2019

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In this study, we analyze an in situ shipboard global ocean drop size distribution (DSD) 8‐year database to understand the underpinning microphysical reasons for discrepancies between satellite oceanic rainfall products at high latitudes reported in the literature. The natural, latitudinal, and convective‐stratiform variability of the DSD is found to be large, with a substantially lower drop concentration with diameter smaller than 3 mm in the Southern hemisphere high latitude (S‐highlat, south of 45°S) and Northern Hemisphere polar latitude (N‐polar, north of 67.5°S) bands, which is where satellite rainfall products most disagree. In contrast, the latitudinal variability of the normalized oceanic DSD is small, implying that the functional form of the normalized DSD can be assumed constant and accurately parameterized using proposed fits. The S‐highlat and N‐polar latitude bands stand out as regions with oceanic rainfall properties different from other latitudes, highlighting fundamental differences in rainfall processes at different latitudes and associated specific challenges for satellite rainfall retrieval techniques. The most salient differences in DSD properties between these two regions and the other latitude bands are: (1) a systematically higher (lower) frequency of occurrence of rainfall rates below (above) 1 mm h‐1, (2) much lower drop concentrations, (3) very different values of the DSD shape parameter (μ0) from what is currently assumed in satellite radar rainfall algorithms, and (4) very different DSD properties in both the convective and stratiform rainfall regimes. Overall, this study provides insights into how DSD assumptions in satellite radar rainfall retrieval techniques could be refined.

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Section: Discussionmentioning

confidence: 99%

The Latitudinal Variability of Oceanic Rainfall Properties and Its Implication for Satellite Retrievals: 1. Drop Size Distribution Properties

et al. 2019

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“…Both field studies included measurements of n INPs active at temperatures from 0 to −27 °C using an ice spectrometer (Hiranuma et al, ), which is an off‐line sampling method using collection on open‐faced filters intended to capture the full aerosol size distribution. During the MHD and CAPRICORN study, 27 and 12 samples were collected, respectively, with air sampling durations ranging from 6 to 63 hr (see McCluskey, Ovadnevaite, Rinaldi, et al, and McCluskey, Hill, Humphries, et al, ).…”

Section: Methodsmentioning

confidence: 99%

Numerical Representations of Marine Ice‐Nucleating Particles in Remote Marine Environments Evaluated Against Observations

McCluskey

DeMott

et al. 2019

Geophysical Research Letters

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The abundance and sources of ice‐nucleating particles, particles required for heterogeneous ice nucleation, are long‐standing sources of uncertainty in quantifying aerosol‐cloud interactions. In this study, we demonstrate near closure between immersion freezing ice‐nucleating particle number concentration (nINPs) observations and nINPs calculated from simulated sea spray aerosol and dust. The Community Atmospheric Model with constrained meteorology was used to simulate aerosol concentrations at the Mace Head Research Station (North Atlantic) and over the Southern Ocean to the south of Tasmania (Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign). Model‐predicted nINPs were within a factor of 10 of nINPs observed with an off‐line ice spectrometer at Mace Head Research Station and Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign, for 93% and 69% of observations, respectively. Simulated vertical profiles of nINPs reveal that transported dust may be critical to nINPs in remote regions and that sea spray aerosol may be the dominate contributor to primary ice nucleation in Southern Ocean low‐level mixed‐phase clouds.

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“…As we show throughout this study, sea spray has a highly nonlinear relationship with wind speed. Given their large contribution to the CCN population (10-65%; Quinn et al, 2017), AOD (Murphy et al, 1998;Revell et al, 2019), and cloud phase (McCluskey et al, 2018) over the Southern Ocean, these particles can have a significant buffering effect on the local climate. We would therefore encourage future studies interested in Journal of Geophysical Research: Atmospheres 10.1029/2019JD032026 climate projections for the Southern Ocean to make use of equation (11) when predicting the surface flux of SSPs.…”

Section: The Direct Radiative Effectmentioning

confidence: 99%

“…Recent studies have also shown that SSPs can act as ice nucleating particles (INPs), which encourage the phase transition of cloud droplets to ice (DeMott et al, ; McCluskey et al, ). Since the Southern Ocean is far removed from continental sources of INPs (e.g., dust), SSPs may be the only source of INPs in the region.…”

Section: Introductionmentioning

confidence: 99%

“…Ice nucleation sites within the droplets are likely a result of suspended amounts of organic material within the sea surface microlayer which became entrained within the droplets during formation (DeMott et al, ). However, organic materials form very little of the mass composition of the resulting SSPs (Murphy et al, ); hence, the ice‐nucleating potential of sea spray is very weak relative to continental sources such as mineral dusts (McCluskey et al, ). Still, the capacity for SSPs to modulate cloud phase represents an additional mechanism through which they can affect the local radiation balance.…”

Section: Introductionmentioning

confidence: 99%

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Constraining the Surface Flux of Sea Spray Particles From the Southern Ocean

et al. 2020

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Modeling the shortwave radiation balance over the Southern Ocean region remains a challenge for Earth system models. To investigate whether this is related to the representation of aerosol‐cloud interactions, we compared measurements of the total number concentration of sea spray‐generated particles within the Southern Ocean region to model predictions thereof. Measurements were conducted from a container laboratory aboard the R/V Tangaroa throughout an austral summer voyage to the Ross Sea. We used source‐receptor modeling to calculate the sensitivity of our measurements to upwind surface fluxes. From this approach, we could constrain empirical parameterizations of sea spray surface flux based on surface wind speed and sea surface temperature. A newly tuned parameterization for the flux of sea spray particles based on the near‐surface wind speed is presented. Comparisons to existing model parameterizations revealed that present model parameterizations led to overestimations of sea spray concentrations. In contrast to previous studies, we found that including sea surface temperature as an explanatory variable did not substantially improve model‐measurement agreement. To test whether or not the parameterization may be applicable globally, we conducted a regression analysis using a database of in situ whitecap measurements. We found that the key fitting parameter within this regression agreed well with the parameterization of sea spray flux. Finally, we compared calculations from the best model of surface flux to boundary layer measurements collected onboard an aircraft throughout the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), finding good agreement overall.

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Observations of Ice Nucleating Particles Over Southern Ocean Waters

Cited by 149 publications

References 49 publications

The Latitudinal Variability of Oceanic Rainfall Properties and Its Implication for Satellite Retrievals: 1. Drop Size Distribution Properties

The Latitudinal Variability of Oceanic Rainfall Properties and Its Implication for Satellite Retrievals: 1. Drop Size Distribution Properties

Numerical Representations of Marine Ice‐Nucleating Particles in Remote Marine Environments Evaluated Against Observations

Constraining the Surface Flux of Sea Spray Particles From the Southern Ocean

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