Sea spray aerosol as a unique source of ice nucleating particles

Ice nucleating particles (INPs) are vital for ice initiation in, and precipitation from, mixed-phase clouds. A source of INPs from oceans within sea spray aerosol (SSA) emissions has been suggested in previous studies but remained unconfirmed. Here, we show that INPs are emitted using real wave breaking in a laboratory flume to produce SSA. The number concentrations of INPs from laboratory-generated SSA, when normalized to typical total aerosol number concentrations in the marine boundary layer, agree well with measurements from diverse regions over the oceans. Data in the present study are also in accord with previously published INP measurements made over remote ocean regions. INP number concentrations active within liquid water droplets increase exponentially in number with a decrease in temperature below 0 °C, averaging an order of magnitude increase per 5 °C interval. The plausibility of a strong increase in SSA INP emissions in association with phytoplankton blooms is also shown in laboratory simulations. Nevertheless, INP number concentrations, or active site densities approximated using “dry” geometric SSA surface areas, are a few orders of magnitude lower than corresponding concentrations or site densities in the surface boundary layer over continental regions. These findings have important implications for cloud radiative forcing and precipitation within low-level and midlevel marine clouds unaffected by continental INP sources, such as may occur over the Southern Ocean.

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Relative humidity dependence of aerosol optical properties and direct radiative forcing in the surface boundary layer at Xinken in Pearl River Delta of China: An observation based numerical study

Atmospheric Environment ◽

10.1016/j.atmosenv.2008.04.009 ◽

2008 ◽

Vol 42 (25) ◽

pp. 6373-6397 ◽

Cited By ~ 111

Author(s):

Y.F. Cheng ◽

A. Wiedensohler ◽

H. Eichler ◽

J. Heintzenberg ◽

M. Tesche ◽

...

Keyword(s):

Boundary Layer ◽

Radiative Forcing ◽

Pearl River Delta ◽

Numerical Study ◽

Pearl River ◽

Surface Boundary ◽

Aerosol Optical Properties ◽

Surface Boundary Layer ◽

Direct Radiative Forcing ◽

Humidity Dependence

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Ice nucleating particles in the marine boundary layer in the Canadian Arctic during summer 2014

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-1027-2019 ◽

2019 ◽

Vol 19 (2) ◽

pp. 1027-1039 ◽

Cited By ~ 19

Author(s):

Victoria E. Irish ◽

Sarah J. Hanna ◽

Megan D. Willis ◽

Swarup China ◽

Jennie L. Thomas ◽

...

Keyword(s):

Boundary Layer ◽

Surface Area ◽

Marine Boundary Layer ◽

Mineral Dust ◽

Canadian Arctic ◽

Particle Dispersion ◽

Sea Spray ◽

Dispersion Modelling ◽

Air Mass ◽

Sea Spray Aerosol

Abstract. Ice nucleating particles (INPs) in the Arctic can influence climate and precipitation in the region; yet our understanding of the concentrations and sources of INPs in this region remain uncertain. In the following, we (1) measured concentrations of INPs in the immersion mode in the Canadian Arctic marine boundary layer during summer 2014 on board the CCGS Amundsen, (2) determined ratios of surface areas of mineral dust aerosol to sea spray aerosol, and (3) investigated the source region of the INPs using particle dispersion modelling. Average concentrations of INPs at −15, −20, and −25 ∘C were 0.005, 0.044, and 0.154 L−1, respectively. These concentrations fall within the range of INP concentrations measured in other marine environments. For the samples investigated the ratio of mineral dust surface area to sea spray surface area ranged from 0.03 to 0.09. Based on these ratios and the ice active surface site densities of mineral dust and sea spray aerosol determined in previous laboratory studies, our results suggest that mineral dust is a more important contributor to the INP population than sea spray aerosol for the samples analysed. Based on particle dispersion modelling, the highest concentrations of INPs were often associated with lower-latitude source regions such as the Hudson Bay area, eastern Greenland, or north-western continental Canada. On the other hand, the lowest concentrations were often associated with regions further north of the sampling sites and over Baffin Bay. A weak correlation was observed between INP concentrations and the time the air mass spent over bare land, and a weak negative correlation was observed between INP concentrations and the time the air mass spent over ice and open water. These combined results suggest that mineral dust from local sources is an important contributor to the INP population in the Canadian Arctic marine boundary layer during summer 2014.

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Measurements of Enhanced Near-Surface Turbulence under Windrows

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0265.1 ◽

2020 ◽

Vol 50 (1) ◽

pp. 197-215

Author(s):

Seth F. Zippel ◽

Ted Maksym ◽

Malcolm Scully ◽

Peter Sutherland ◽

Dany Dumont

Keyword(s):

Boundary Layer ◽

Surface Flux ◽

Breaking Waves ◽

Surface Boundary ◽

Surface Boundary Layer ◽

Near Surface ◽

Surface Turbulence ◽

Order Of Magnitude ◽

Convergence Zones ◽

Shallow Bay

AbstractObservations of waves, winds, turbulence, and the geometry and circulation of windrows were made in a shallow bay in the winter of 2018 outside of Rimouski, Québec. Water velocities measured from a forward-looking pulse-coherent ADCP mounted on a small zodiac show spanwise (cross-windrow) convergence, streamwise (downwind) velocity enhancement, and downwelling in the windrows, consistent with the view that windrows are the result of counterrotating pairs of wind-aligned vortices. The spacing of windrows, measured with acoustic backscatter and with surface imagery, was measured to be approximately twice the water depth, which suggests an aspect ratio of 1. The magnitude and vertical distribution of turbulence measured from the ADCP are consistent with a previous scaling and observations of near-surface turbulence under breaking waves, with dissipation rates larger and decaying faster vertically than what is expected from a shear-driven boundary layer. Measurements of dissipation rate are partitioned to within, and outside of the windrow convergence zones, and measurements inside the convergence zones are found to be nearly an order of magnitude larger than those outside with similar vertical structure. A ratio of time scales suggests that turbulence likely dissipates before it can be advected horizontally into convergences, but the advection of wave energy into convergences may elevate the surface flux of TKE and could explain the elevated turbulence in the windrows. These results add to a limited number of conflicting observations of turbulence variability due to windrows, which may modify gas flux, and heat and momentum transport in the surface boundary layer.

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An assessment of hygroscopic growth factors for aerosols in the surface boundary layer for computing direct radiative forcing

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jd000152 ◽

2001 ◽

Vol 106 (D17) ◽

pp. 20213-20224 ◽

Cited By ~ 45

Author(s):

Jung-Sun Im ◽

Vinod K. Saxena ◽

Brian N. Wenny

Keyword(s):

Boundary Layer ◽

Growth Factors ◽

Radiative Forcing ◽

Surface Boundary ◽

Hygroscopic Growth ◽

Surface Boundary Layer ◽

Direct Radiative Forcing

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Relative Humidity Dependence of Aerosol Optical Properties and Direct Radiative Forcing in the Surface Boundary Layer of Southeastern China

Nucleation and Atmospheric Aerosols ◽

10.1007/978-1-4020-6475-3_96 ◽

2007 ◽

pp. 489-493

Author(s):

Y. F. Cheng ◽

Alfred Wiedensohler ◽

H. Eichler ◽

Y. H. Zhang ◽

W. Birmili ◽

...

Keyword(s):

Boundary Layer ◽

Optical Properties ◽

Relative Humidity ◽

Radiative Forcing ◽

Surface Boundary ◽

Aerosol Optical Properties ◽

Southeastern China ◽

Surface Boundary Layer ◽

Direct Radiative Forcing ◽

Humidity Dependence

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Ice nucleating particles in the marine boundary layer in the Canadian Arctic during summer 2014

10.5194/acp-2018-735 ◽

2018 ◽

Author(s):

Victoria E. Irish ◽

Sarah J. Hanna ◽

Megan D. Willis ◽

Swarup China ◽

Jennie L. Thomas ◽

...

Keyword(s):

Boundary Layer ◽

Surface Area ◽

Marine Boundary Layer ◽

Mineral Dust ◽

Canadian Arctic ◽

Particle Dispersion ◽

Sea Spray ◽

Dispersion Modelling ◽

Air Mass ◽

Sea Spray Aerosol

Abstract. Ice nucleating particles (INPs) in the Arctic can influence climate and precipitation in the region; yet our understanding of the concentrations and sources of INPs in this region remain uncertain. In the following we (1) measured concentrations of INPs in the Canadian Arctic marine boundary layer during summer 2014 on board the CCGS Amundsen, (2) determined ratios of surface areas of mineral dust aerosol to sea spray aerosol, and (3) investigated the source region of the INPs using particle dispersion modelling. Average concentrations of INPs at −15, −20 and −25 °C were 0.005, 0.044, and 0.154 L−1, respectively. These concentrations fall within the range of INP concentrations measured in other marine environments. For the samples investigated the ratio of mineral dust surface area to sea spray surface area ranged from 0.03 to 0.09. Based on these ratios and the ice active surface site densities of mineral dust and sea spray aerosol determined in previous laboratory studies, our results suggest that mineral dust is a more important contributor to the INP population than sea spray aerosol for the samples analysed. Based on particle dispersion modelling, the highest concentrations of INPs were often associated with lower latitude source regions such as the Hudson Bay area, eastern Greenland, or northwestern continental Canada. On the other hand, the lowest concentrations were often associated with regions further north of the sampling sites and over Baffin Bay. A weak correlation was observed between INP concentrations and the time the air mass spent over bare land, and a weak negative correlation was observed between INP concentrations and the time the air mass spent over ice and open water. These combined results suggest that mineral dust from local sources is an important contributor to the INP population in the Canadian Arctic marine boundary layer during summer 2014.

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Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

Revista Brasileira de Meteorologia ◽

10.1590/0102-77863540083 ◽

2020 ◽

Author(s):

Yagya Dutta Dwivedi ◽

Vasishta Bhargava Nukala ◽

Satya Prasad Maddula ◽

Kiran Nair

Keyword(s):

Boundary Layer ◽

Time Series ◽

Surface Roughness ◽

Wind Speed ◽

Atmospheric Turbulence ◽

Surface Boundary ◽

Low Frequencies ◽

Surface Boundary Layer ◽

Power Spectral ◽

Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

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