scholarly journals Long-Term Trends in Marine Boundary Layer Properties over the Atlantic Ocean

2019 ◽  
Vol 32 (10) ◽  
pp. 2991-3004 ◽  
Author(s):  
Juan P. Díaz ◽  
Francisco J. Expósito ◽  
Juan C. Pérez ◽  
Albano González ◽  
Yuqing Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
Marine Boundary Layer ◽  
Inversion Layer ◽  
Precipitable Water ◽  
Cloud Formation ◽  
Climate Projections ◽  
Free Troposphere ◽  
Long Term Trends

Abstract The marine boundary layer (MBL) is a key component of Earth’s climate system, and its main characteristics (height, entrainment efficiency, energy and mass fluxes, cloud formation processes, etc.) are closely linked to the properties of the inversion layer, which generally determines its height. Furthermore, cloud response to a warmer climate, one of the main sources of uncertainty in future climate projections, is highly dependent on changes in the MBL and in the inversion-layer properties. Long-term trends of the time series of MBL parameters at 32 stations in the Atlantic Ocean have been analyzed using conveniently homogenized radiosonde profiles from 1981 to 2010. In general, decreasing trends are found in the strength and thickness of the inversion layer and in the difference between the precipitable water vapor (PWV) in the free troposphere and the MBL. In contrast, positive trends are found in the height of the bottom of the inversion layer, the lapse rates of virtual and equivalent potential temperatures, the PWV within the boundary layer, and the sea surface temperature (SST). The weakening trend of the inversion layer and the increasing desiccation of the free troposphere relative to the MBL could have important consequences for both the evolution of low cloud cover in a greenhouse-warming climate and the fragile local ecosystems, such as “cloud forests.”

scholarly journals Oxidation photochemistry in the Southern Atlantic boundary layer: unexpected deviations of photochemical steady state

2011 ◽  
Vol 11 (3) ◽  
pp. 7045-7093 ◽  
Author(s):  
Z. Hosaynali Beygi ◽  
H. Fischer ◽  
H. D. Harder ◽  
M. Martinez ◽  
R. Sander ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Atlantic Ocean ◽  
Atmospheric Chemistry ◽  
Marine Boundary Layer ◽  
Air Pollutant ◽  
Photochemical Oxidant ◽  
Important Region ◽  
Atmospheric Observations ◽  
Oxidation Efficiency

Abstract. Ozone (O3) is a photochemical oxidant, an air pollutant and a greenhouse gas. As the main precursor of the hydroxyl radical (OH) it strongly affects the oxidation power of the atmosphere. The remote marine boundary layer (MBL) is considered an important region in terms of chemical O3 loss; however surface-based atmospheric observations are sparse and the photochemical processes are not well understood. To investigate the photochemistry under the clean background conditions of the Southern Atlantic Ocean, ship measurements of NO, NO2, O3, JNO2, J(O1D), HO2, OH, ROx and a range of meteorological parameters were carried out. The concentrations of NO and NO2 measured on board the French research vessel Marion-Dufresne (28° S–57° S, 46° W–34° E) in March 2007, are among the lowest yet observed. The data is evaluated for consistency with photochemical steady state (PSS) conditions, and the calculations indicate substantial deviations from PSS (Φ>1). The deviations observed under low NOx conditions (5–25 pptv) demonstrate a remarkable upward tendency in the Leighton ratio (used to characterize PSS) with increasing NOx mixing ratio and JNO2 intensity. It is a paradigm in atmospheric chemistry that OH largely controls the oxidation efficiency of the atmosphere. However, evidence is growing that for unpolluted low-NOx (NO + NO2) conditions the atmospheric oxidant budget is poorly understood. Nevertheless, for the very cleanest conditions, typical for the remote marine boundary layer, good model agreement with measured OH and HO2 radicals has been interpreted as accurate understanding of baseline photochemistry. Here we show that such agreement can be deceptive and that a yet unidentified oxidant is needed to explain the photochemical conditions observed at 40°–60° S over the Atlantic Ocean.

Two months of measurements with an autonomous thermodynamic Raman lidar in Lindenberg

2021 ◽  
Author(s):  
Diego Lange Vega ◽  
Andreas Behrendt ◽  
Volker Wulfmeyer
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Inversion Layer ◽  
Measurement Range ◽  
High Accuracy ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Backscatter Coefficient ◽  
Geophysical Research ◽  
Turbulence Scale

<p>Between 15 July 2020 and 19 September 2021, the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) collected data at the Lindenberg Observatory of the Deutscher Wetterdienst (DWD), including temperature and water vapor mixing ratio with a high temporal and range resolution.</p> <p>During the operation period, very stable 24/7 operation was achieved, and ARTHUS demonstrated that is capable to observe the atmospheric boundary layer and lower free troposphere during both daytime and nighttime up to the turbulence scale, with high accuracy and precision, and very short latency. During nighttime, the measurement range increases even up to the tropopause and lower stratosphere.</p> <p>ARTHUS measurements resolve the strength of the inversion layer at the planetary boundary layer top, elevated lids in the free troposphere, and turbulent fluctuations in water vapor and temperature, simultaneously (Lange et al., 2019, Wulfmeyer et al., 2015). In addition to thermodynamic variables, ARTHUS provides also independent profiles of the particle backscatter coefficient and the particle extinction coefficient from the rotational Raman signals at 355 nm with much better resolution than a conventional vibrational Raman lidar.</p> <p>At the conference, highlights of the measurements will be presented. Furthermore, the statistics of more than 150 comparisons with local radiosondes will be presented which confirm the high accuracy of the temperature and moisture measurements of ARTHUS.</p> <p><strong><em>Acknowledgements</em></strong></p> <p>The development of ARTHUS was supported by the Helmholtz Association of German Research Centers within the project Modular Observation Solutions for Earth Systems (MOSES). The measurements in Lindenberg were funded by DWD.</p> <p><strong><em>References </em></strong></p> <p>Lange, D., Behrendt, A., and Wulfmeyer, V. (2019). Compact operational tropospheric water vapor and temperature Raman lidar with turbulence resolution. <em>Geophysical Research Letters</em>, 46. https://doi.org/10.1029/2019GL085774</p> <p>Wulfmeyer, V., R. M. Hardesty, D. D. Turner, A. Behrendt, M. P. Cadeddu, P. Di Girolamo, P. Schlüssel, J. Van Baelen, and F. Zus (2015), A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles, <em>Rev. Geophys.</em>, 53,819–895, doi:10.1002/2014RG000476</p>

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

2004 ◽  
Vol 61 (24) ◽  
pp. 3049-3064 ◽  
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.

Aerosol size distributions and optical properties found in the marine boundary layer over the Atlantic Ocean

1990 ◽  
Vol 95 (D4) ◽  
pp. 3659 ◽  
Author(s):  
W. A. Hoppel ◽  
J. W. Fitzgerald ◽  
G. M. Frick ◽  
R. E. Larson ◽  
E. J. Mack
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Atlantic Ocean ◽  
Marine Boundary Layer ◽  
Size Distributions

Long-term trends in fog and boundary layer characteristics in Tianjin, China

Particuology ◽  
2015 ◽  
Vol 20 ◽  
pp. 61-68 ◽  
Author(s):  
Suqin Han ◽  
Ziying Cai ◽  
Yufen Zhang ◽  
Jiao Wang ◽  
Qing Yao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Term Trends

scholarly journals Impact of nucleation on global CCN

2009 ◽  
Vol 9 (3) ◽  
pp. 12999-13037 ◽  
Author(s):  
J. Merikanto ◽  
D. V. Spracklen ◽  
G. W. Mann ◽  
S. J. Pickering ◽  
K. S. Carslaw
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Environmental Changes ◽  
Control Strategies ◽  
Cloud Condensation Nuclei ◽  
Free Troposphere ◽  
Carbonaceous Particles ◽  
Upper Troposphere ◽  
Low Level ◽  
Primary Emissions

Abstract. Cloud condensation nuclei (CCN) are derived from particles emitted directly into the atmosphere (primary emissions) or from the growth of nanometer-sized particles nucleated in the atmosphere. It is important to separate these two sources because they respond in different ways to gas and particle emission control strategies and environmental changes. Here, we use a global aerosol microphysics model to quantify the contribution of primary and nucleated particles to global CCN. The model considers primary emissions of sea spray, sulfate and carbonaceous particles, and nucleation processes appropriate for the free troposphere and boundary layer. We estimate that 45% of global low-level cloud CCN at 0.2% supersaturation are secondary aerosol derived from nucleation (ranging between 31–49% taking into account uncertainties primary emissions and nucleation rates), the remainder being directly emitted as primary aerosol. The model suggests that 35% of CCN (0.2%) in low-level clouds were created in the free and upper troposphere. In the marine boundary layer 55% of CCN (0.2%) are from nucleation, 45% being entrained from the free troposphere. Both in global and marine boundary layer 10% of CCN (0.2%) is nucleated in the boundary layer. Combinations of model runs show that primary and nucleated CCN are non-linearly coupled. In particular, boundary layer nucleated CCN are strongly suppressed by both primary emissions and entrainment of particles nucleated in the free troposphere. Elimination of all primary emissions reduces global CCN (0.2%) by only 20% and elimination of upper tropospheric nucleation reduces CCN (0.2%) by only 12% because of increased impact of boundary layer nucleation on CCN.

scholarly journals Time-dependent entrainment of smoke presents an observational challenge for assessing aerosol–cloud interactions over the southeast Atlantic Ocean

2018 ◽  
Vol 18 (19) ◽  
pp. 14623-14636 ◽  
Author(s):  
Michael S. Diamond ◽  
Amie Dobracki ◽  
Steffen Freitag ◽  
Jennifer D. Small Griswold ◽  
Ashley Heikkila ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
Marine Boundary Layer ◽  
Climate Modeling ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Cloud Properties ◽  
History Of ◽  
Cloud Droplet Number Concentration ◽  
The Relationship

Abstract. The colocation of clouds and smoke over the southeast Atlantic Ocean during the southern African biomass burning season has numerous radiative implications, including microphysical modulation of the clouds if smoke is entrained into the marine boundary layer. NASA's ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign is studying this system with aircraft in three field deployments between 2016 and 2018. Results from ORACLES-2016 show that the relationship between cloud droplet number concentration and smoke below cloud is consistent with previously reported values, whereas cloud droplet number concentration is only weakly associated with smoke immediately above cloud at the time of observation. By combining field observations, regional chemistry–climate modeling, and theoretical boundary layer aerosol budget equations, we show that the history of smoke entrainment (which has a characteristic mixing timescale on the order of days) helps explain variations in cloud properties for similar instantaneous above-cloud smoke environments. Precipitation processes can obscure the relationship between above-cloud smoke and cloud properties in parts of the southeast Atlantic, but marine boundary layer carbon monoxide concentrations for two case study flights suggest that smoke entrainment history drove the observed differences in cloud properties for those days. A Lagrangian framework following the clouds and accounting for the history of smoke entrainment and precipitation is likely necessary for quantitatively studying this system; an Eulerian framework (e.g., instantaneous correlation of A-train satellite observations) is unlikely to capture the true extent of smoke–cloud interaction in the southeast Atlantic.

Sign in / Sign up

Export Citation Format

Share Document