scholarly journals Evidence of tropospheric layering: interleaved stratospheric and planetary boundary layer intrusions

2007 ◽  
Vol 7 (1) ◽  
pp. 1119-1142 ◽  
Author(s):  
J. Brioude ◽  
J.-P. Cammas ◽  
R. M. Zbinden ◽  
V. Thouret
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Residence Time ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Particle Dispersion ◽  
Lagrangian Model ◽  
Residence Times ◽  
Free Troposphere

Abstract. We present a case study of interleaving in the free troposphere of 4 layers of non-tropospheric origin, with emphasis on their residence time in the troposphere. Two layers are stratospheric intrusions at 4.7 and 2.2 km altitude with residence times of about 2 and 6.5 days, respectively. The two other layers at 7 and 3 km altitude were extracted from the maritime planetary boundary layer by warm conveyor belts associated with two extratropical lows and have residence times of about 2 and 5.75 days, respectively. The event took place over Frankfurt (Germany) in February 2002 and was observed by a commercial airliner from the MOZAIC programme with measurements of ozone, carbon monoxide and water vapour. Origins and residence times in the troposphere of these layers are documented with a trajectory and particle dispersion model. The combination of forward and backward simulations of the Lagrangian model allows the period of time during which the residence time can be assessed to be longer, as shown by the capture of the stratospheric-origin signature of the lowest tropopause fold just about to be completely mixed above the planetary boundary layer. This case study is of interest for atmospheric chemistry because it emphasizes the importance of coherent airstreams that produce laminae in the free troposphere and that contribute to the average tropospheric ozone. The interleaving of these 4 layers also provides the conditions for a valuable case study for the validation of global chemistry transport models used to perform tropospheric ozone budgets.

scholarly journals Global distribution of the effective aerosol hygroscopicity parameter for CCN activation

2010 ◽  
Vol 10 (3) ◽  
pp. 6301-6339 ◽  
Author(s):  
K. J. Pringle ◽  
H. Tost ◽  
A. Pozzer ◽  
U. Pöschl ◽  
J. Lelieveld
Keyword(s):  
Boundary Layer ◽  
Standard Deviation ◽  
Planetary Boundary Layer ◽  
Atmospheric Chemistry ◽  
Regional Distribution ◽  
Cloud Condensation Nucleus ◽  
Cloud Formation ◽  
Sea Spray ◽  
Mean Values ◽  
Aerosol Hygroscopicity

Abstract. In this study we use the ECHAM/MESSy Atmospheric Chemistry (EMAC) model to simulate global fields of the effective hygroscopicity parameter κ which approximately describes the influence of chemical composition on the cloud condensation nucleus (CCN) activity of aerosol particles. The obtained global mean values of κ at the Earth's surface are 0.27±0.21 for continental and 0.72±0.24 for marine regions (arithmetic mean ± standard deviation). The mean κ values are in good agreement with previous estimates based on observational data, but the model standard deviation for continental regions is higher. Over the continents, the regional distribution appears fairly uniform, with κ values mostly in the range of 0.1–0.4. Lower values over large arid regions and regions of high organic loading lead to reduced continental average values for Africa and South America (0.15–0.17) compared to the other continents (0.21–0.36). Marine regions show greater variability with κ values ranging from 0.9–1.0 in remote regions to 0.4–0.6 in continental outflow regions where the highly hygroscopic sea spray aerosol mixes with less hygroscopic continental aerosol. Marine κ values as low as 0.2–0.3 are simulated in the outflow from the Sahara desert. At the top of the planetary boundary layer the κ values can deviate substantially from those at the surface (up to 30%) – especially in marine and coastal regions. In moving from the surface to the height of the planetary boundary layer, the global average marine κ value reduces by 20%. Thus, surface observations may not always be representative for the altitudes where cloud formation mostly occurs. In a pre-industrial model scenario, the κ values tend to be higher over marine regions and lower over the continents, because the anthropogenic particulate matter is on average less hygroscopic than sea-spray but more hygroscopic than the natural continental background aerosol (dust and organic matter). The influence of industrialisation on aerosol hygroscopicity appears to be less pronounced than the influence on the atmospheric aerosol burden. However, in regions influenced by desert dust the particle hygroscopicity has increased strongly as the mixing of air pollutants with mineral particles typically enhances the Kappa values by a factor of 2–3.

The Growth of the Planetary Boundary Layer at a Coastal Site: a Case Study

2011 ◽  
Vol 139 (3) ◽  
pp. 521-541 ◽  
Author(s):  
Ferdinando De Tomasi ◽  
M. Marcello Miglietta ◽  
M. Rita Perrone
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Coastal Site

scholarly journals On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

2016 ◽  
Vol 16 (21) ◽  
pp. 14025-14039 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis ◽  
Evangelos Tyrlis ◽  
Bojan Škerlak ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Free Troposphere ◽  
Near Surface ◽  
Grid Points ◽  
High Concentrations

Abstract. We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

scholarly journals Lower-free tropospheric ozone dial measurements over Athens, Greece

2018 ◽  
Vol 176 ◽  
pp. 05025 ◽  
Author(s):  
Michail Mytilinaios ◽  
Alexandros Papayannis ◽  
Georgios Tsaknakis
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Tropospheric Ozone ◽  
Vertical Profile ◽  
Stimulated Raman Scattering ◽  
Laser Wavelength ◽  
Free Troposphere ◽  
Differential Absorption ◽  
Raman Cell ◽  
Laser Remote Sensing

A compact ozone differential absorption lidar (DIAL) was implemented at the Laboratory of Laser Remote Sensing of the National Technical University of Athens (NTUA), in Athens, Greece. The DIAL system is based on a Nd:YAG laser emitting at 266 nm. A high-pressure Raman cell, filled with D2, was used to generate the λON and λOFF laser wavelength pairs (i.e., 266-289 nm and 289-316 nm, respectively) based on the Stimulated Raman Scattering (SRS) effect. The system was run during daytime and nighttime conditions to obtain the vertical profile of tropospheric ozone in the Planetary Boundary Layer (PBL) and the adjacent free troposphere.

scholarly journals Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

2016 ◽  
Vol 16 (6) ◽  
pp. 3743-3760 ◽  
Author(s):  
Sean Coburn ◽  
Barbara Dix ◽  
Eric Edgerton ◽  
Christopher D. Holmes ◽  
Douglas Kinnison ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Column Density ◽  
Atmospheric Mercury ◽  
Water Soluble ◽  
Reference Spectrum ◽  
Free Troposphere ◽  
Mercury Oxidation ◽  
Oxidation Rates ◽  
Southeastern Us

Abstract. The elevated deposition of atmospheric mercury over the southeastern United States is currently not well understood. Here we measure partial columns and vertical profiles of bromine monoxide (BrO) radicals, a key component of mercury oxidation chemistry, to better understand the processes and altitudes at which mercury is being oxidized in the atmosphere. We use data from a ground-based MAX-DOAS instrument located at a coastal site ∼  1 km from the Gulf of Mexico in Gulf Breeze, FL, where we had previously detected tropospheric BrO (Coburn et al., 2011). Our profile retrieval assimilates information about stratospheric BrO from the WACCM chemical transport model (CTM), and uses only measurements at moderately low solar zenith angles (SZAs) to estimate the BrO slant column density contained in the reference spectrum (SCDRef). The approach has 2.6 degrees of freedom, and avoids spectroscopic complications that arise at high SZA; knowledge about SCDRef further helps to maximize sensitivity in the free troposphere (FT). A cloud-free case study day with low aerosol load (9 April 2010) provided optimal conditions for distinguishing marine boundary layer (MBL: 0–1 km) and free-tropospheric (FT: 1–15 km) BrO from the ground. The average daytime tropospheric BrO vertical column density (VCD) of ∼  2.3  ×  1013 molec cm−2 (SZA  <  70°) is consistent with our earlier reports on other days. The vertical profile locates essentially all tropospheric BrO above 4 km, and shows no evidence for BrO inside the MBL (detection limit  <  0.5 pptv). BrO increases to  ∼  3.5 pptv at 10–15 km altitude, consistent with recent aircraft observations. Our case study day is consistent with recent aircraft studies, in that the oxidation of gaseous elemental mercury (GEM) by bromine radicals to form gaseous oxidized mercury (GOM) is the dominant pathway for GEM oxidation throughout the troposphere above Gulf Breeze. The column integral oxidation rates are about 3.6  × 105 molec cm−2 s−1 for bromine, while the contribution from ozone (O3) is 0.8  ×  105 molec cm−2 s−1. Chlorine-induced oxidation is estimated to add  <  5 % to these mercury oxidation rates. The GOM formation rate is sensitive to recently proposed atmospheric scavenging reactions of the HgBr adduct by nitrogen dioxide (NO2), and to a lesser extent also HO2 radicals. Using a 3-D CTM, we find that surface GOM variations are also typical of other days, and are mainly derived from the FT. Bromine chemistry is active in the FT over Gulf Breeze, where it forms water-soluble GOM that is subsequently available for wet scavenging by thunderstorms or transport to the boundary layer.

scholarly journals Employing Spectral Analysis to Obtain Dispersion Parameters in an Atmospheric Environment Driven by a Mesoscale Downslope Windstorm

2021 ◽  
Vol 18 (24) ◽  
pp. 13027
Author(s):  
Cinara Ewerling da Rosa ◽  
Michel Stefanello ◽  
Silvana Maldaner ◽  
Douglas Stefanello Facco ◽  
Débora Regina Roberti ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Diffusion Theory ◽  
Dispersion Model ◽  
Atmospheric Dispersion ◽  
Particle Dispersion ◽  
Atmospheric Environment ◽  
Dispersion Parameters ◽  
Simulated Concentration ◽  
Four Levels

Considering the influence of the downslope windstorm called “Vento Norte” (VNOR; Portuguese for “North Wind”) in planetary boundary layer turbulent features, a new set of turbulent parameterizations, which are to be used in atmospheric dispersion models, has been derived. Taylor’s statistical diffusion theory, velocity spectra obtained at four levels (3, 6, 14, and 30 m) in a micrometeorological tower, and the energy-containing eddy scales are used to calculate neutral planetary boundary layer turbulent parameters. Vertical profile formulations of the wind velocity variances and Lagrangian decorrelation time scales are proposed, and to validate this new parameterization, it is applied in a Lagrangian Stochastic Particle Dispersion Model to simulate the Prairie Grass concentration experiments. The simulated concentration results were shown to agree with those observed.

scholarly journals Ceilometers as planetary boundary layer height detectors and a corrective tool for COSMO and IFS models

2020 ◽  
Vol 20 (20) ◽  
pp. 12177-12192
Author(s):  
Leenes Uzan ◽  
Smadar Egert ◽  
Pavel Khain ◽  
Yoav Levi ◽  
Elyakom Vadislavsky ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Small Scale ◽  
Transform Method ◽  
Pollution Dispersion ◽  
Boundary Layer Height ◽  
Scale Modeling ◽  
Richardson Method ◽  
Parcel Method

Abstract. The significance of planetary boundary layer (PBL) height detection is apparent in various fields, especially in air pollution dispersion assessments. Numerical weather models produce a high spatial and temporal resolution of PBL heights; however, their performance requires validation. This necessity is addressed here by an array of eight ceilometers; a radiosonde; and two models – the Integrated Forecast System (IFS) global model and COnsortium for Small-scale MOdeling (COSMO) regional model. The ceilometers were analyzed with the wavelet covariance transform method, and the radiosonde and models with the parcel method and the bulk Richardson method. Good agreement for PBL height was found between the ceilometer and the adjacent Bet Dagan radiosonde (33 m a.s.l.) at 11:00 UTC launching time (N=91 d, ME =4 m, RMSE =143 m, R=0.83). The models' estimations were then compared to the ceilometers' results in an additional five diverse regions where only ceilometers operate. A correction tool was established based on the altitude (h) and distance from shoreline (d) of eight ceilometer sites in various climate regions, from the shoreline of Tel Aviv (h=5 m a.s.l., d=0.05 km) to eastern elevated Jerusalem (h=830 m a.s.l., d=53 km) and southern arid Hazerim (h=200 m a.s.l., d=44 km). The tool examined the COSMO PBL height approximations based on the parcel method. Results from a 14 August 2015 case study, between 09:00 and 14:00 UTC, showed the tool decreased the PBL height at the shoreline and in the inner strip of Israel by ∼100 m and increased the elevated sites of Jerusalem and Hazerim up to ∼400 m, and ∼600 m, respectively. Cross-validation revealed good results without Bet Dagan. However, without measurements from Jerusalem, the tool underestimated Jerusalem's PBL height by up to ∼600 m.

scholarly journals Microbial Ecology of the Planetary Boundary Layer

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1296
Author(s):  
Romie Tignat-Perrier ◽  
Aurélien Dommergue ◽  
Timothy M. Vogel ◽  
Catherine Larose
Keyword(s):  
Boundary Layer ◽  
Microbial Communities ◽  
Planetary Boundary Layer ◽  
Atmospheric Chemistry ◽  
Microbial Community Composition ◽  
Health Concern ◽  
Local Source ◽  
Microbial Composition ◽  
Biological Origin ◽  
Microbial Survival

Aerobiology is a growing research area that covers the study of aerosols with a biological origin from the air that surrounds us to space through the different atmospheric layers. Bioaerosols have captured a growing importance in atmospheric process-related fields such as meteorology and atmospheric chemistry. The potential dissemination of pathogens and allergens through the air has raised public health concern and has highlighted the need for a better prediction of airborne microbial composition and dynamics. In this review, we focused on the sources and processes that most likely determine microbial community composition and dynamics in the air that directly surrounds us, the planetary boundary layer. Planetary boundary layer microbial communities are a mix of microbial cells that likely originate mainly from local source ecosystems (as opposed to distant sources). The adverse atmospheric conditions (i.e., UV radiation, desiccation, presence of radicals, etc.) might influence microbial survival and lead to the physical selection of the most resistant cells during aerosolization and/or aerial transport. Future work should further investigate how atmospheric chemicals and physics influence microbial survival and adaptation in order to be able to model the composition of planetary boundary layer microbial communities based on the surrounding landscapes and meteorology.

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