Aircraft measurements of sea surface conditions and their relationship to marine boundary-layer dynamics

Elevated sea-surface temperatures are a necessary but not sufficient requirement for the formation of hurricanes and typhoons. This paper suggests a way to exploit this. Twomey [1] showed that cloud reflectivity depends on the size-distribution of cloud drops, with a large number of small drops reflecting more than a smaller number of larger ones. Mid-ocean air is cleaner than over land. Latham [2-4] suggested that reflectivity of marine stratocumulus clouds could be increased by releasing a submicron spray of filtered sea water into the bottom of the marine boundary layer. The salt residues left after evaporation would be mixed by turbulence through the full depth of the marine boundary layer and would be ideal cloud condensation nuclei. Those that reached a height where the air had a super-saturation above 100% by enough to get over the peak of the Köhler curve would produce an increased number of cloud drops and so trigger the Twomey effect. The increase in reflection from cloud tops back out to space would cool sea-surface water. We are not trying to increase cloud cover; we just want to make existing cloud tops whiter. The spray could be produced by wind-driven vessels cruising chosen ocean regions. The engineering design of sea-going hardware is well advanced. This paper suggests a way to calculate spray quantities and the number and cost of spray vessels to achieve a hurricane reduction to a more acceptable intensity. It is intended to show the shape of a possible calculation with credible if not exact assumptions. Anyone with better assumptions should be able to follow the process.

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Exchange of sulfur between the free troposphere, marine boundary layer, and the sea surface

Journal of Geophysical Research Atmospheres ◽

10.1029/jc087ic11p08795 ◽

1982 ◽

Vol 87 (C11) ◽

pp. 8795 ◽

Cited By ~ 37

Author(s):

Mark A. Kritz

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Sea Surface ◽

Free Troposphere

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Effects of Large Eddies on the Structure of the Marine Boundary Layer under Strong Wind Conditions

Journal of the Atmospheric Sciences ◽

10.1175/jas-3342.1 ◽

2004 ◽

Vol 61 (24) ◽

pp. 3049-3064 ◽

Cited By ~ 28

Author(s):

Isaac Ginis ◽

Alexander P. Khain ◽

Elena Morozovsky

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Marine Boundary Layer ◽

Sea Surface ◽

Cloud Formation ◽

Strong Wind ◽

Latent Heat Release ◽

Air Humidity ◽

Near Surface ◽

Large Eddies

Abstract A model of the atmospheric boundary layer (BL) is presented that explicitly calculates a two-way interaction of the background flow and convective motions. The model is utilized for investigation of the formation of large eddies (roll vortices) and their effects on the structure of the marine boundary layer under conditions resembling those of tropical cyclones. It is shown that two main factors controlling the formation of large eddies are the magnitude of the background wind speed and air humidity, determining the cloud formation and latent heat release. When the wind speed is high enough, a strong vertical wind shear develops in the lower part of the BL, which triggers turbulent mixing and the formation of a mixed layer. As a result, the vertical profiles of velocity, potential temperature, and mixing ratio in the background flow are modified to allow for the development of large eddies via dynamic instability. Latent heat release in clouds was found to be the major energy source of large eddies. The cloud formation depends on the magnitude of air humidity. The most important manifestation of the effects of large eddies is a significant increase of the near-surface wind speed and evaporation from the sea surface. For strong wind conditions, the increase of the near-surface speed can exceed 10 m s−1 and evaporation from the sea surface can double. These results demonstrate an important role large eddies play in the formation of BL structure in high wind speeds. Inclusion of these effects in the BL parameterizations of tropical cyclone models may potentially lead to substantial improvements in the prediction of storm intensity.

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Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA-evolution

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-9331-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 9331-9375 ◽

Cited By ~ 2

Author(s):

R. H. H. Janssen ◽

J. Vilà-Guerau de Arellano ◽

L. N. Ganzeveld ◽

P. Kabat ◽

J. L. Jimenez ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Land Surface ◽

Large Scale ◽

Organic Aerosol ◽

Layer Growth ◽

Combined Effects ◽

Free Troposphere ◽

Surface Conditions ◽

Boundary Layer Dynamics

Abstract. We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the model for a case study in Hyytiälä, Finland, and find that it is able to well reproduce the observed dynamics and gas-phase chemistry. We show that the exchange of organic aerosol between the free troposphere and the boundary layer (entrainment) must be taken into account in order to explain the observed diurnal cycle in organic aerosol (OA) concentration. An examination of the budgets of organic aerosol and terpene concentration shows that the former is dominated by entrainment, while the latter is mainly driven by emission and chemical transformation. We systematically examine the role of the land surface, which governs both the surface energy balance partitioning and terpene-emissions, and the large-scale atmospheric process of vertical subsidence. Entrainment is especially important for the dilution of organic aerosol concentrations under conditions of dry soils and low terpene-emissions. Subsidence suppresses boundary layer growth while enhancing entrainment. Therefore it influences the relationship between organic aerosol and terpene-concentrations. Our findings indicate that the diurnal evolution of SOA in the boundary layer is the result of coupled effects of the land surface, dynamics of the atmospheric boundary layer, chemistry, and free troposphere conditions. This has potentially some consequences for the design of both field campaigns and large-scale modeling studies.

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A laboratory characterisation of inorganic iodine emissions from the sea surface: dependence on oceanic variables and parameterisation for global modelling

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-31445-2013 ◽

2013 ◽

Vol 13 (12) ◽

pp. 31445-31477 ◽

Cited By ~ 1

Author(s):

S. M. MacDonald ◽

J. C. Gómez Martín ◽

R. Chance ◽

S. Warriner ◽

A. Saiz-Lopez ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Chemistry ◽

Marine Boundary Layer ◽

Environmental Parameters ◽

Sea Surface ◽

Total Iodine ◽

Iodide Ions ◽

Iodine Compounds ◽

Halogen Chemistry ◽

Inorganic Iodine

Abstract. Reactive iodine compounds play a~significant role in the atmospheric chemistry of the oceanic boundary layer by influencing the oxidising capacity through catalytically removing O3 and altering the HOx and NOx balance. The sea-to-air flux of iodine over the open ocean is therefore an important quantity in assessing these impacts on a global scale. This paper examines the effect of a number of relevant environmental parameters, including water temperature, salinity and organic compounds, on the magnitude of the HOI and I2 fluxes produced from the uptake of O3 and its reaction with iodide ions in aqueous solution. The results of these laboratory experiments and those reported previously (Carpenter et al., 2013), along with sea surface iodide concentrations measured or inferred from measurements of dissolved total iodine and iodate reported in the literature, were then used to produce parameterised expressions for the HOI and I2 fluxes as a function of wind speed, sea-surface temperature and O3. These expressions were used in the Tropospheric HAlogen chemistry MOdel (THAMO) to compare with MAX-DOAS measurements of iodine monoxide (IO) performed during the HaloCAST-P cruise in the Eastern Pacific ocean (Mahajan et al., 2012). The modelled IO agrees reasonably with the field observations, although significant discrepancies are found during a period of low wind speeds (<3 m s−1), when the model overpredicts IO by up to a factor of three. The inorganic iodine flux contributions to IO are found to be comparable to, or even greater than, the contribution of organo-iodine compounds and therefore its inclusion in atmospheric models is important to improve predictions of the influence of halogen chemistry in the marine boundary layer.

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Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-17815-2010 ◽

2010 ◽

Vol 10 (7) ◽

pp. 17815-17851 ◽

Cited By ~ 1

Author(s):

N. A. Brunsell ◽

D. B. Mechem ◽

M. C. Anderson

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Latent Heat ◽

Latent Heat Flux ◽

Land Surface ◽

Surface Heterogeneity ◽

Length Scales ◽

Surface Conditions ◽

Boundary Layer Dynamics

Abstract. The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface – large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC) field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model. The simulations exhibit little variation in net radiation. Rather, a change in the partitioning of the surface energy between sensible and latent heat flux is responsible for differences in boundary layer dynamics. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to surface heterogeneity than water vapor, which implies that the role of surface heterogeneity in modifying the local temperature gradients in order to maximize convective heat fluxes. More homogeneous surface conditions, on the other hand, tend to maximize latent heat flux. Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w, T and q) and associated cospectra (w'T', w'q' and T'q'), however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the mean wind speed.

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Twenty-Four-Hour Observations of the Marine Boundary Layer Using Shipborne NOAA High-Resolution Doppler Lidar

Journal of Applied Meteorology ◽

10.1175/jam2296.1 ◽

2005 ◽

Vol 44 (11) ◽

pp. 1723-1744 ◽

Cited By ~ 27

Author(s):

Volker Wulfmeyer ◽

Tijana Janjić

Keyword(s):

Boundary Layer ◽

High Resolution ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Wind Shear ◽

Marine Boundary Layer ◽

Sea Surface ◽

Doppler Lidar ◽

Sensible Heat ◽

Wind Profiles

Abstract Shipborne observations obtained with the NOAA high-resolution Doppler lidar (HRDL) during the 1999 Nauru (Nauru99) campaign were used to study the structure of the marine boundary layer (MBL) in the tropical Pacific Ocean. During a day with weak mesoscale activity, diurnal variability of the height of the convective MBL was observed using HRDL backscatter data. The observed diurnal variation in the MBL height had an amplitude of about 250 m. Relations between the MBL height and in situ measurements of sea surface temperature as well as latent and sensible heat fluxes were examined. Good correlation was found with the sea surface temperature. The correlation with the latent heat flux was lower, and practically no correlation between the MBL height and the sensible heat and buoyancy fluxes could be detected. Horizontal wind profiles were measured using a velocity–azimuth display scan of HRDL velocity data. Strong wind shear at the top of the MBL was observed in most cases. Comparison of these results with GPS radiosonde data shows discrepancies in the wind intensity and direction, which may be due to different observation times and locations as well as due to multipath effects at the ship’s platform. Vertical wind profiles corrected for ship’s motion were used to derive vertical velocity variance and skewness profiles. Motion compensation had a significant effect on their shape. Normalized by the convective velocity scale and by the top of the mixed layer zi, the variance varied between 0.45 and 0.65 at 0.4z/zi and decreased to 0.2 at 1.0z/zi. The skewness ranged between 0.3 and 0.8 in the MBL and showed in almost all cases a maximum between 1.0z/zi and 1.1z/zi. These profiles revealed the existence of another turbulent layer above the MBL, which was probably driven by wind shear and cloud condensation processes.

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Iodine chemistry in the tropical and remote open ocean marine boundary layer

10.5194/egusphere-egu2020-990 ◽

2020 ◽

Author(s):

Swaleha Inamdar ◽

Liselotte Tinel ◽

Rosie Chance ◽

Lucy Jane Carpenter ◽

Sabu Prabhakaran ◽

...

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Kinetic Model ◽

Southern Ocean ◽

Tropospheric Ozone ◽

Marine Boundary Layer ◽

Sea Surface ◽

Iodine Species ◽

Ocean Region ◽

Inorganic Iodine

Iodine chemistry plays an essential role in controlling the radiation budget by changing various atmospheric parameters. Iodine in the atmosphere is known to cause depletion of ozone via catalytic reaction cycles. It alters the atmospheric oxidation capacity, and lead to ultrafine particle formation that acts as potential cloud condensation nuclei. The ocean is the primary source of iodine; it enters the atmosphere through fluxes of gaseous reactive iodine species. At the ocean surface, seawater iodide reacts with tropospheric ozone (gas) to form inorganic iodine species in gaseous form. These species namely, hypoiodous acid (HOI) and molecular iodine (I2) quickly photolyse to release reactive iodine (I) in the atmosphere. This process acts as a significant sink for tropospheric ozone contributing to ~16% ozone loss throughout the troposphere. Reactive iodine released in the atmosphere undergoes the formation of iodine monoxide (IO) or higher oxides of iodine (IxOx) via self-recombination reactions. It is known that inorganic iodine fluxes (HOI and I2) contribute to 75% of the detected IO over the Atlantic Ocean. However, we did not observe this from ship-based MAX-DOAS studies between 2014-2017. At present, there are no direct observations of inorganic iodine (HOI; few for I2) and are estimated via empirical methods derived from the interfacial kinetic model by Carpenter et al. in 2013. Based on the kinetic model, estimation of HOI and I2 fluxes depends on three parameters, namely, ozone concentration, surface iodide concentration, and the wind speed. This parameterisation for inorganic fluxes assumes a sea surface temperature (SST) of 293 K and has limiting wind speed conditions. Since the parameterisation conditions assumed SST of 293 K higher uncertainties due to errors in activation energy creeps in the estimation of HOI flux compared to I2 as the flux of HOI is ~20 times greater than that of I2. For three consecutive expeditions in the Indian and Southern Ocean, we detected ~1 pptv of IO in the marine boundary layer. These levels are not explained by the calculated inorganic fluxes by using observed and predicted sea surface iodide concentrations. This method of iodine flux estimation is currently used in all global models, along with the MacDonald et al. 2014 iodide estimation method. Model output using these parameterisations have not been able to match the observed IO levels in the Indian and Southern Ocean region. This discrepancy suggests that the process of efflux of iodine to the atmosphere may not be fully understood, and the current parametrisation does not do justice to the observations. It also highlights that the flux of organic iodine may also play a role in observed IO levels, especially in the Indian Ocean region. A correlation of 0.7 was achieved above the 99% confidence limit for chlorophyll-a with observed IO concentration in this region. There is a need to carry more observations to improve the estimation technique of iodine sea-air flux thus improving model predictions of IO in the atmosphere.

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