scholarly journals The distribution of sea-salt aerosol in the global troposphere

2019 ◽  
Vol 19 (6) ◽  
pp. 4093-4104 ◽  
Author(s):  
Daniel M. Murphy ◽  
Karl D. Froyd ◽  
Huisheng Bian ◽  
Charles A. Brock ◽  
Jack E. Dibb ◽  
...  
Keyword(s):  
Dominant Role ◽  
Open Water ◽  
Sea Salt ◽  
Transport Models ◽  
Upper Troposphere ◽  
Sea Salt Aerosol ◽  
Pack Ice ◽  
Wide Range ◽  
Wet Scavenging ◽  
The Tropics

Abstract. We present the first data on the concentration of sea-salt aerosol throughout most of the depth of the troposphere and over a wide range of latitudes, which were obtained during the Atmospheric Tomography (ATom) mission. Sea-salt concentrations in the upper troposphere are very small, usually less than 10 ng per standard m3 (about 10 parts per trillion by mass) and often less than 1 ng m−3. This puts stringent limits on the contribution of sea-salt aerosol to halogen and nitric acid chemistry in the upper troposphere. Within broad regions the concentration of sea-salt aerosol is roughly proportional to water vapor, supporting a dominant role for wet scavenging in removing sea-salt aerosol from the atmosphere. Concentrations of sea-salt aerosol in the winter upper troposphere are not as low as in the summer and the tropics. This is mostly a consequence of less wet scavenging in the drier, colder winter atmosphere. There is also a source of sea-salt aerosol over pack ice that is distinct from that over open water. With a well-studied and widely distributed source, sea-salt aerosol provides an excellent test of wet scavenging and vertical transport of aerosols in chemical transport models.

scholarly journals The distribution of sea-salt aerosol in the global troposphere

2018 ◽  
Author(s):  
Daniel M. Murphy ◽  
Karl D. Froyd ◽  
Huisheng Bian ◽  
Charles A. Brock ◽  
Jack E. Dibb ◽  
...  
Keyword(s):  
Dominant Role ◽  
Open Water ◽  
Sea Salt ◽  
Transport Models ◽  
Upper Troposphere ◽  
Sea Salt Aerosol ◽  
Pack Ice ◽  
Wide Range ◽  
Wet Scavenging ◽  
The Tropics

Abstract. We present the first data on the concentration of sea-salt aerosol throughout most of the depth of the troposphere and over a wide range of latitudes. Sea salt concentrations in the upper troposphere are very small, usually less than 10 ng per standard m3 (about 10 parts per trillion by mass) and often less than 1 ng m−3. This puts stringent limits on the contribution of sea-salt aerosol to halogen and nitric acid chemistry in the upper troposphere. Within broad regions the concentration of sea-salt aerosol is roughly proportional to water vapor, supporting a dominant role for wet scavenging in removing sea-salt aerosol from the atmosphere. Concentrations of sea-salt aerosol in the winter upper troposphere are not as low as in the summer and the tropics. This is mostly a consequence of less wet scavenging in the drier, colder winter atmosphere. There is also a source of sea-salt aerosol over pack ice that is distinct from that over open water. With a well-studied and widely distributed source, sea-salt aerosol provides an excellent test of wet scavenging and vertical transport of aerosols in chemical transport models.

scholarly journals A statistical analysis of the influence of deep convection on water vapor variability in the tropical upper troposphere

2009 ◽  
Vol 9 (15) ◽  
pp. 5847-5864 ◽  
Author(s):  
J. S. Wright ◽  
R. Fu ◽  
A. J. Heymsfield
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Upper Troposphere ◽  
Ambient Relative Humidity ◽  
Wide Range ◽  
Ice Water Content ◽  
The Tropics ◽  
Ice Water ◽  
Tropical Upper Troposphere

Abstract. The factors that control the influence of deep convective detrainment on water vapor in the tropical upper troposphere are examined using observations from multiple satellites in conjunction with a trajectory model. Deep convection is confirmed to act primarily as a moisture source to the upper troposphere, modulated by the ambient relative humidity (RH). Convective detrainment provides strong moistening at low RH and offsets drying due to subsidence across a wide range of RH. Strong day-to-day moistening and drying takes place most frequently in relatively dry transition zones, where between 0.01% and 0.1% of Tropical Rainfall Measuring Mission Precipitation Radar observations indicate active convection. Many of these strong moistening events in the tropics can be directly attributed to detrainment from recent tropical convection, while others in the subtropics appear to be related to stratosphere-troposphere exchange. The temporal and spatial limits of the convective source are estimated to be about 36–48 h and 600–1500 km, respectively, consistent with the lifetimes of detrainment cirrus clouds. Larger amounts of detrained ice are associated with enhanced upper tropospheric moistening in both absolute and relative terms. In particular, an increase in ice water content of approximately 400% corresponds to a 10–90% increase in the likelihood of moistening and a 30–50% increase in the magnitude of moistening.

scholarly journals A reinterpretation of sea-salt records in Greenland and Antarctic ice cores?

2004 ◽  
Vol 39 ◽  
pp. 276-282 ◽  
Author(s):  
Andrew M. Rankin ◽  
Eric W. Wolff ◽  
Robert Mulvaney
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Open Water ◽  
Weddell Sea ◽  
Sea Salt ◽  
Sea Salt Aerosol ◽  
Ice Surface ◽  
Frost Flowers ◽  
Ice Production ◽  
Ice Core Records

AbstractIt has recently been shown that much sea-salt aerosol around the coast of Antarctica is generated not from open water, but from the surface of newly formed sea ice. Previous interpretations of ice-core records have disregarded the sea-ice surface as a source of sea salt. The majority of sea-salt aerosol at Halley research station originates from frost flowers rather than open water, and the seasonal cycle of sea salt in aerosol at Halley appears to be controlled by ice production in the Weddell Sea, as well as variations in wind speed. Frost flowers are also an important source of aerosol at Siple Dome, suggesting that variations in sea-salt concentrations in the core, and other cores drilled in similar locations, may be reflecting changes in sea-ice production rather than changes in transportation patterns. For Greenland cores, and those from low-accumulation inland sites in Antarctica, it is not simple to calculate the proportion of sea salt originating from frost flowers rather than open water. However, modelling studies suggest that a sea-ice surface source contributed much of the flux of sea salt to these sites in glacial periods, suggesting that interpretations of ice-core records from these locations should also be revisited.

Evaluation and Computation of Potential Evaporation in the Tropics

1968 ◽  
Vol 4 (4) ◽  
pp. 351-357 ◽  
Author(s):  
D. A. Rijks ◽  
J. T. Walker
Keyword(s):  
Open Water ◽  
Reflection Coefficients ◽  
Tropical Agriculture ◽  
Computer Programme ◽  
Data Validation ◽  
Potential Evaporation ◽  
Wide Range ◽  
The World ◽  
Validation Procedure ◽  
The Tropics

SUMMARYThe problems involved in the estimation of potential evaporation in the tropics are discussed, and available methods for calculating potential evaporation are assessed. A computer programme is described which evaluates Penman's formula, accommodating data from the very wide range of conditions experienced in tropical agriculture. The programme conforms with recent W.M.O. recommendations and is written for computers available in many parts of the world. An important component of the programme is a strict data validation procedure. The output includes daily and mean ten-day estimates of E, using the reflection coefficients for open water and for a crop as well as both calculated and, where available, measured values of radiation.

scholarly journals Effect of sea salt aerosol on tropospheric bromine chemistry

2019 ◽  
Vol 19 (9) ◽  
pp. 6497-6507 ◽  
Author(s):  
Lei Zhu ◽  
Daniel J. Jacob ◽  
Sebastian D. Eastham ◽  
Melissa P. Sulprizio ◽  
Xuan Wang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Sea Salt ◽  
Heterogeneous Reactions ◽  
Tropospheric Chemistry ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
The Tropics ◽  
Outstanding Issue

Abstract. Bromine radicals influence global tropospheric chemistry by depleting ozone and by oxidizing elemental mercury and reduced sulfur species. Observations typically indicate a 50 % depletion of sea salt aerosol (SSA) bromide relative to seawater composition, implying that SSA debromination could be the dominant global source of tropospheric bromine. However, it has been difficult to reconcile this large source with the relatively low bromine monoxide (BrO) mixing ratios observed in the marine boundary layer (MBL). Here we present a new mechanistic description of SSA debromination in the GEOS-Chem global atmospheric chemistry model with a detailed representation of halogen (Cl, Br, and I) chemistry. We show that observed levels of SSA debromination can be reproduced in a manner consistent with observed BrO mixing ratios. Bromine radical sinks from the HOBr + S(IV) heterogeneous reactions and from ocean emission of acetaldehyde are critical in moderating tropospheric BrO levels. The resulting HBr is rapidly taken up by SSA and also deposited. Observations of SSA debromination at southern midlatitudes in summer suggest that model uptake of HBr by SSA may be too fast. The model provides a successful simulation of free-tropospheric BrO in the tropics and midlatitudes in summer, where the bromine radical sink from the HOBr + S(IV) reactions is compensated for by more efficient HOBr-driven recycling in clouds compared to previous GEOS-Chem versions. Simulated BrO in the MBL is generally much higher in winter than in summer due to a combination of greater SSA emission and slower conversion of bromine radicals to HBr. An outstanding issue in the model is the overestimate of free-tropospheric BrO in extratropical winter–spring, possibly reflecting an overestimate of the HOBr∕HBr ratio under these conditions where the dominant HOBr source is hydrolysis of BrNO3.

scholarly journals Modeling and evaluation of the global sea-salt aerosol distribution: sensitivity to emission schemes and resolution effects at coastal/orographic sites

2013 ◽  
Vol 13 (5) ◽  
pp. 11597-11657 ◽  
Author(s):  
M. Spada ◽  
O. Jorba ◽  
C. Perez ◽  
Z. Janjic ◽  
J. M. Baldasano
Keyword(s):  
High Resolution ◽  
Transport Model ◽  
Scale Effects ◽  
Surface Concentration ◽  
Sea Salt ◽  
Complex Topography ◽  
Chemical Transport Model ◽  
Sea Salt Aerosol ◽  
Mass Load ◽  
Wide Range

Abstract. We investigate two of the major sources of uncertainty in the model estimation of the global distribution of sea-salt aerosol, i.e. the sensitivity to the emission parameterization and the influence of model resolution in coastal regions characterized by complex topography and/or steep orographic barriers where some observation sites are located. We evaluate a new sea-salt aerosol lifecycle module implemented within the online chemical transport model NMMB/BSC-CTM. Because of its multiscale core, the model is able to cover a wide range of scales. Global simulations using four state-of-the-art sea-salt emission schemes are evaluated against monthly-averaged aerosol optical depth (AOD) from selected AERONET Sun photometers, surface concentration measurements from the University of Miami's Ocean Aerosol Network and measurements from two NOAA/PMEL cruises (AEROINDOEX and ACE1). The model results are highly sensitive to the introduction of SST-dependent emissions and to the accounting of spume particles production. Depending on emission scheme, annual emissions range from 4312.9 Tg to 8979.7 Tg in the 2006. Sea-salt lifetime varies between 7.7 h and 12.0 h and the annual mean column mass load is between 5.9 Tg and 7.9 Tg. Observed coarse AOD monthly averages are reproduced with an overall correlation around 0.8 (a correlation of 0.6 is produced when applying the SST dependent scheme). Although monthly-averaged surface concentrations are overall in good agreement with the observations, there is a subset of coastal sites surrounded by complex topography where the global model overestimates by a factor of 2 or more. Using regional high-resolution simulations, we show that these large errors are mostly due to the global model's inability to capture local scale effects. In New Zeland, the increase in resolution produces a significant decrease of surface concentrations (up to 40%) – due to changes in the wind circulation and precipitation driven by the orographic barrier – which is in close agreement with surface concentration monthly climatologies measured by University of Miami stations in the region (Baring Head, Chatam Island and Inverncargill). The observed climatological precipitation in this area is well reproduced by the model at high resolution, while it is strongly underestimated when employing coarser scales. Our results outline that caution may be taken when evaluating and/or constraining coarse global sea-salt simulations with observations around coastal/orographic sites.

scholarly journals Hygroscopic properties of NaCl and NaNO<sub>3</sub> mixture particles as reacted inorganic sea-salt aerosol surrogates

2014 ◽  
Vol 14 (23) ◽  
pp. 33143-33183
Author(s):  
D. Gupta ◽  
H. Kim ◽  
G. Park ◽  
X. Li ◽  
H.-J. Eom ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Aerosol Particles ◽  
Sea Salt ◽  
Droplet Growth ◽  
Dehydration Process ◽  
Two Stage ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Wide Range

Abstract. NaCl in fresh sea-salt aerosol (SSA) particles can partially or fully react with atmospheric NOx / HNO3, so internally mixed NaCl and NaNO3 aerosol particles can co-exist over a wide range of mixing ratios. Laboratory-generated, micrometer-sized NaCl and NaNO3 mixture particles at ten mixing ratios (mole fractions of NaCl (XNaCl) = 0.1 to 0.9) were examined systematically to observe their hygroscopic behavior, derive experimental phase diagrams for deliquescence and efflorescence, and understand the efflorescence mechanism. During the humidifying process, aerosol particles with the eutonic composition (XNaCl = 0.38) showed only one phase transition at their mutual deliquescence relative humidity (MDRH) of 67.9(± 0.5)%. On the other hand, particles with other mixing ratios showed two distinct deliquescence transitions, i.e., the eutonic component dissolved at MDRH and the remainder in the solid phase dissolved completely at their DRHs depending on the mixing ratios, resulting in a phase diagram composed of four different phases, as predicted thermodynamically. During the dehydration process, NaCl-rich particles (XNaCl > 0.38) showed two-stage efflorescence transitions: the first stage was purely driven by the homogeneous nucleation of NaCl and the second stage at the mutual efflorescence RH (MERH) of the eutonic components, with values in the range of 30.0–35.5%. Interestingly, aerosol particles with the eutonic composition (XNaCl = 0.38) also showed two-stage efflorescence with NaCl crystallizing first followed by heterogeneous nucleation of the remaining NaNO3 on the NaCl seeds. NaNO3-rich particles XNaCl ≤ 0.3) underwent single-stage efflorescence transitions at ERHs progressively lower than the MERH, because of the homogeneous nucleation of NaCl and the almost simultaneous heterogeneous nucleation of NaNO3 on the NaCl seeds. SEM/EDX elemental mapping indicated that the effloresced NaCl-NaNO3 particles at all mixing ratios were composed of a homogeneously crystallized NaCl moiety in the center, surrounded either by the eutonic component (for XNaCl > 0.38) or NaNO3 (for XNaCl ≤ 0.38). During the humidifying or dehydration process, the amount of eutonic composed part drives particle/droplet growth or shrinkage at the MDRH or MERH (second ERH), respectively, and the amount of remnant pure salts (NaCl or NaNO3 in NaCl- or NaNO3-rich particles, respectively) drives the second DRHs or first ERHs, respectively. Therefore, their behavior can be a precursor to the optical properties and direct radiative forcing for these atmospherically relevant mixture particles representing the coarse, reacted inorganic SSAs. In addition, the NaCl-NaNO3 mixture aerosol particles can maintain an aqueous phase over a wider RH range than the genuine SSA surrogate (i.e., pure NaCl particles), making their heterogeneous chemistry more probable.

scholarly journals Comparison of two different sea-salt aerosol schemes as implemented in air quality models applied to the Mediterranean Basin

2011 ◽  
Vol 11 (10) ◽  
pp. 4833-4850 ◽  
Author(s):  
P. Jiménez-Guerrero ◽  
O. Jorba ◽  
M. T. Pay ◽  
J. P. Montávez ◽  
S. Jerez ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Mediterranean Basin ◽  
Mediterranean Area ◽  
Sea Salt ◽  
Target Area ◽  
Transport Models ◽  
Sea Salt Aerosol ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. A number of attempts have been made to incorporate sea-salt aerosol (SSA) source functions in chemistry transport models with varying results according to the complexity of the scheme considered. This contribution compares the inclusion of two different SSA algorithms in two chemistry transport models: CMAQ and CHIMERE. The main goal is to examine the differences in average SSA mass and composition and to study the seasonality of the prediction of SSA when applied to the Mediterranean area with high resolution for a reference year. Dry and wet deposition schemes are also analyzed to better understand the differences observed between both models in the target area. The applied emission algorithm in CHIMERE uses a semi-empirical formulation which obtains the surface emission rate of SSA as a function of the particle size and the surface wind speed raised to the power 3.41. The emission parameterization included within CMAQ is somehow more sophisticated, since fluxes of SSA are corrected with relative humidity. In order to evaluate their strengths and weaknesses, the participating algorithms as implemented in the chemistry transport models were evaluated against AOD measurements from Aeronet and available surface measurements in Southern Europe and the Mediterranean area, showing biases around −0.002 and −1.2 μg m−3, respectively. The results indicate that both models represent accurately the patterns and dynamics of SSA and its non-uniform behavior in the Mediterranean basin, showing a strong seasonality. The levels of SSA strongly vary across the Western and the Eastern Mediterranean, reproducing CHIMERE higher annual levels in the Aegean Sea (12 μg m−3) and CMAQ in the Gulf of Lion (9 μg m−3). The large difference found for the ratio PM2.5/total SSA in CMAQ and CHIMERE is also investigated. The dry and wet removal rates are very similar for both models despite the different schemes implemented. Dry deposition essentially follows the surface drag stress patterns, meanwhile wet deposition is more scattered over the continent. CMAQ tends to provide larger amounts of SSA dry deposition over the Northern Mediterranean (0.7–1.0 g m−2 yr−1), meanwhile the Southeastern Mediterranean accounts for the maximum annual dry deposition in the CHIMERE model (0.9–1.5 g m−2 yr−1). The wet deposition is dominated by the accumulation mode and is strongly correlated to the precipitation patterns, showing CMAQ a higher wet deposition/total deposition ratio over coastal mountain chains. The results of both models constitute a step towards increasing the understanding of the SSA dynamics in a complex area as the Mediterranean.

scholarly journals Hygroscopic properties of NaCl and NaNO<sub>3</sub> mixture particles as reacted inorganic sea-salt aerosol surrogates

2015 ◽  
Vol 15 (6) ◽  
pp. 3379-3393 ◽  
Author(s):  
D. Gupta ◽  
H. Kim ◽  
G. Park ◽  
X. Li ◽  
H.-J. Eom ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Aerosol Particles ◽  
Sea Salt ◽  
Droplet Growth ◽  
Dehydration Process ◽  
Two Stage ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Wide Range

Abstract. NaCl in fresh sea-salt aerosol (SSA) particles can partially or fully react with atmospheric NOx/HNO3, so internally mixed NaCl and NaNO3 aerosol particles can co-exist over a wide range of mixing ratios. Laboratory-generated, micrometer-sized NaCl and NaNO3 mixture particles at 10 mixing ratios (mole fractions of NaCl (XNaCl) = 0.1 to 0.9) were examined systematically to observe their hygroscopic behavior, derive experimental phase diagrams for deliquescence and efflorescence, and understand the efflorescence mechanism. During the humidifying process, aerosol particles with the eutonic composition (XNaCl = 0.38) showed only one phase transition at their mutual deliquescence relative humidity (MDRH) of 67.9 (±0.5)% On the other hand, particles with other mixing ratios showed two distinct deliquescence transitions; i.e., the eutonic component dissolved at MDRH, and the remainder in the solid phase dissolved completely at their DRHs depending on the mixing ratios, resulting in a phase diagram composed of four different phases, as predicted thermodynamically. During the dehydration process, NaCl-rich particles (XNaCl > 0.38) showed a two stage efflorescence transition: the first stage was purely driven by the homogeneous nucleation of NaCl and the second stage at the mutual efflorescence RH (MERH) of the eutonic components, with values in the range of 30.0–35.5%. Interestingly, aerosol particles with the eutonic composition (XNaCl = 0.38) also showed two-stage efflorescence, with NaCl crystallizing first followed by heterogeneous nucleation of the remaining NaNO3 on the NaCl seeds. NaNO3-rich particles (XNaCl ≤ 0.3) underwent single-stage efflorescence transitions at ERHs progressively lower than the MERH because of the homogeneous nucleation of NaCl and the almost simultaneous heterogeneous nucleation of NaNO3 on the NaCl seeds. SEM/EDX elemental mapping indicated that the effloresced NaCl–NaNO3 particles at all mixing ratios were composed of a homogeneously crystallized NaCl moiety in the center, surrounded either by the eutonic component (for XNaCl > 0.38) or NaNO3 (for XNaCl ≤ 0.38). During the humidifying or dehydration process, the amount of eutonic composed part drives particle/droplet growth or shrinkage at the MDRH or MERH (second ERH), respectively, and the amount of pure salts (NaCl or NaNO3 in NaCl- or NaNO3-rich particles, respectively) drives the second DRHs or first ERHs, respectively. Therefore, their behavior can be a precursor to the optical properties and direct radiative forcing for these atmospherically relevant mixture particles representing the coarse, reacted inorganic SSAs. In addition, the NaCl–NaNO3 mixture aerosol particles can maintain an aqueous phase over a wider RH range than pure NaCl particles as SSA surrogate, making their heterogeneous chemistry more probable.

Sign in / Sign up

Export Citation Format

Share Document