scholarly journals The ATAL within the 2017 Asian Monsoon Anticyclone: Microphysical aerosol properties derived from aircraft-borne in situ measurements

2021 ◽  
Author(s):  
Christoph Mahnke ◽  
Ralf Weigel ◽  
Francesco Cairo ◽  
Jean-Paul Vernier ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Aerosol Particles ◽  
Potential Temperature ◽  
Particle Diameter ◽  
Aerosol Layer ◽  
Mixing Ratio ◽  
Detection Range ◽  
Particle Mixing

Abstract. The Asian summer monsoon is an effective pathway for aerosol particles and precursor substances from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA) has been observed by satellites, called the Asian Tropopause Aerosol Layer (ATAL). In this paper we discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the region of the Asian monsoon anticyclone. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (reached a maximum altitude of about 20.5 km) were conducted by a modified Ultra High Sensitivity Aerosol Spectrometer Airborne (UHSAS-A; particle diameter detection range from 65 nm to 1 µm), the COndensation PArticle counting System (COPAS, for detecting total aerosol densities of submicrometer sized particles), and the Cloud and Aerosol Spectrometer with Detection of POLarization (NIXE-CAS-DPOL). In the COPAS and UHSAS-A vertical particle mixing ratio profiles, the ATAL is evident as a distinct layer between 15 km (≈ 370 K) and 18.5 km altitude (≈ 420 K potential temperature). Within the ATAL, the maximum detected particle mixing ratios (from the median profiles) were 700 mg−1 for diameters between 65 nm to 1 µm (UHSAS-A) and higher than 2500 mg−1 for diameters larger than 10 nm (COPAS). These values are up to two times higher than previously found at similar altitudes in other tropical locations. The difference between the particle mixing ratio profiles measured by the UHSAS-A and the COPAS indicate that the region below the ATAL at potential temperatures from 350 to 370 K is influenced by the fresh nucleation of aerosol particles (diameter

scholarly journals In situ observation of new particle formation (NPF) in the tropical tropopause layer of the 2017 Asian monsoon anticyclone – Part 1: Summary of StratoClim results

2021 ◽  
Vol 21 (15) ◽  
pp. 11689-11722
Author(s):  
Ralf Weigel ◽  
Christoph Mahnke ◽  
Manuel Baumgartner ◽  
Antonis Dragoneas ◽  
Bärbel Vogel ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Particle Formation ◽  
In Situ Observation ◽  
Aerosol Layer ◽  
New Particle Formation ◽  
Tropical Tropopause Layer ◽  
Temperature Anomalies ◽  
Nucleation Mode ◽  
Tropical Tropopause

Abstract. During the monsoon season of the year 2017 the airborne StratoClim mission took place in Kathmandu, Nepal, with eight mission flights of the M-55 Geophysica in the upper troposphere–lower stratosphere (UTLS) of the Asian monsoon anticyclone (AMA) over northern India, Nepal, and Bangladesh. More than 100 events of new particle formation (NPF) were observed. In total, more than 2 h of flight time was spent under NPF conditions as indicated by the abundant presence of nucleation-mode aerosols, i.e. with particle diameters dp smaller than 15 nm, which were detected in situ by means of condensation nuclei counting techniques. Mixing ratios of nucleation-mode particles (nnm) of up to ∼ 50 000 mg−1 were measured at heights of 15–16 km (θ ≈ 370 K). NPF was most frequently observed at ∼ 12–16 km altitude (θ ≈ 355–380 K) and mainly below the tropopause. Resulting nnm remained elevated (∼ 300–2000 mg−1) up to altitudes of ∼ 17.5 km (θ ≈ 400 K), while under NPF conditions the fraction (f) of sub-micrometre-sized non-volatile residues (dp > 10 nm) remained below 50 %. At ∼ 12–14 km (θ ≈ 355–365 K) the minimum of f (< 15 %) was found, and underneath, the median f generally remains below 25 %. The persistence of particles at nucleation-mode sizes is limited to a few hours, mainly due to coagulation, as demonstrated by a numerical simulation. The frequency of NPF events observed during StratoClim 2017 underlines the importance of the AMA as a source region for UTLS aerosols and for the formation and maintenance of the Asian tropopause aerosol layer (ATAL). The observed abundance of NPF-produced nucleation-mode particles within the AMA is not unambiguously attributable to (a) specific source regions in the boundary layer (according to backward trajectory analyses), or (b) the direct supply with precursor material by convective updraught (from correlations of NPF with carbon monoxide), or (c) the recent release of NPF-capable material from the convective outflow (according to air mass transport times in the tropical tropopause layer, TTL). Temperature anomalies with ΔT of 2 K (peak-to-peak amplitude), as observed at a horizontal wavelength of ∼ 70–100 km during a level flight of several hours, match with NPF detections and represent an additional mechanism for local increases in supersaturation of the NPF precursors. Effective precursor supply and widely distributed temperature anomalies within the AMA can explain the higher frequency of intense NPF observed during StratoClim 2017 than all previous NPF detections with COPAS (COndensation PArticle counting System) at TTL levels over Brazil, northern Australia, or West Africa.

The ATAL and its aerosol microphysical properties in the Asian Monsoon Anticyclone

2020 ◽  
Author(s):  
Christoph Mahnke ◽  
Stephan Borrmann ◽  
Ralf Weigel ◽  
Francesco Cairo ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Particle Size ◽  
Asian Monsoon ◽  
Extreme Values ◽  
Monsoon Season ◽  
Measurement Techniques ◽  
Potential Temperature ◽  
Particle Diameter ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Microphysical Properties

&lt;p&gt;During the StratoClim 2017 measurement campaign in Nepal, within the Asian Monsoon Anticyclone (AMA), measurements of the aerosols&amp;#8217; microphysical properties up to UT/LS altitudes were successfully completed with a modified version of the commercially available (Droplet Measurement Technologies Inc.) aerosol spectrometer UHSAS-A. Technical rearrangements of parts of the UHSAS-A were developed and implemented, which improve the instrument&amp;#8217;s measuring performance and extend its airborne application range from around 12 km altitude to the extreme ambient conditions in the stratosphere at heights of 20 km. The measurement techniques used for this purpose were characterized by laboratory experiments.&lt;/p&gt;&lt;p&gt;Within the AMA region, extreme values of the particle mixing ratio (PMR) ranging between 6 mg&lt;sup&gt;-1&lt;/sup&gt; and about 10000 mg&lt;sup&gt;-1&lt;/sup&gt; were found with the UHSAS-A (particle diameter range: 65 nm to 1000 nm). The median of the PMR for all research flights was about 1300 mg&lt;sup&gt;-1&lt;/sup&gt; close to the ground. Within tropospheric altitudes, the PMR was highly variable and median values between 70 mg&lt;sup&gt;-1&lt;/sup&gt; and 400 mg&lt;sup&gt;-1&lt;/sup&gt; were observed. &amp;#160;At levels of 370 K potential temperature, the median PMR maximally reaches about 700 mg&lt;sup&gt;-1 &lt;/sup&gt;while the 1 Hz resolved measurements show values up to about 10000 mg&lt;sup&gt;-1&lt;/sup&gt;. Between 450 K and 475 K, median PMR between 40 mg&lt;sup&gt;-1&lt;/sup&gt; and 50 mg&lt;sup&gt;-1&lt;/sup&gt; were observed. The aerosol size distributions (measured by the UHSAS-A) were extended by an additional diameter size bin obtained from the 4-channel Condensation Particle counting System (COPAS), i.e. for aerosol diameter between 10&amp;#160;nm and 65&amp;#160;nm.&lt;/p&gt;&lt;p&gt;The UHSAS-A measured aerosol particle size distributions were compared with balloon-borne measurements (by T. Deshler et al., Dep. of Atmospheric Science, University of Wyoming, USA) at altitudes of up to 20 km. These show that the size distributions measured during the StratoClim 2017 campaign fit well within the range of the balloon-borne measurements during the Asian Monsoon season over India (Hyderabad) in 2015 and the USA (Laramie) in 2013. Further analyses of measured particle size distributions by means of backscatter ratio show remarkable consistency with CALIOP satellite observations of the ATAL during the StratoClim mission period.&lt;/p&gt;

scholarly journals Relationship between Asian monsoon strength and transport of surface aerosols to the Asian Tropopause Aerosol Layer (ATAL): Interannual variability and decadal changes

2018 ◽  
Author(s):  
Cheng Yuan ◽  
William K. M. Lau ◽  
Zhanqing Li ◽  
Maureen Cribb ◽  
Tijian Wang
Keyword(s):  
Interannual Variability ◽  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Deep Convection ◽  
Reanalysis Data ◽  
Aerosol Layer ◽  
Carbonaceous Aerosols ◽  
South Asian Summer Monsoon ◽  
Gangetic Plain ◽  
Monsoon Strength

Abstract. In this study, we have investigated the interannual variability and the decadal trend of carbon monoxide (CO), carbonaceous aerosols (CA), and mineral dust in the Asian Tropopause Aerosol Layer (ATAL) in relation to varying strengths of the South Asian summer monsoon (SASM) using MERRA2 reanalysis data (2001–2015). Results show that during this period, the aforementioned ATAL constituents exhibit strong interannual variability and rising trends connected to the variations of the strength of SASM. During strong monsoon years, the Asian Monsoon Anticyclone (AMA) is more expansive and shifted northward compared to weak years. In spite of effect of quenching of biomass burning emissions of CO and CA by increased precipitation, as well as the removal of CA and dust by increased washout from the surface to mid-troposphere in monsoon regions, all three constituents are found to be more abundant in an elongated accumulation zone at ATAL, on the southern flank of the expanded AMA. Enhanced transport to the ATAL by overshooting deep convection is found over preferred pathways along the foothills of the Himalayan-Gangetic Plain (HGP), and the Sichuan Basin (SB). The long-term positive trends of ATAL CO and CA are robust, while ATAL dust trend is weak due to its large interannual variability. The ATAL trends are associated with increasing strength of the AMA, with earlier and enhanced vertical transport of ATAT constituents by enhanced overshooting convection over the HGP and SB regions, out-weighing the strong reduction of CA and dust from surface to the mid-troposphere.

scholarly journals The Asian tropopause aerosol layer within the 2017 monsoon anticyclone: microphysical properties derived from aircraft-borne in situ measurements

2021 ◽  
Vol 21 (19) ◽  
pp. 15259-15282
Author(s):  
Christoph Mahnke ◽  
Ralf Weigel ◽  
Francesco Cairo ◽  
Jean-Paul Vernier ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Particle Size ◽  
Aerosol Particle ◽  
Aerosol Particles ◽  
Aerosol Layer ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Data Set ◽  
Microphysical Properties ◽  
Aerosol Particle Size

Abstract. The Asian summer monsoon is an effective pathway for aerosol particles and precursors from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA), called the Asian tropopause aerosol layer (ATAL), has been observed by satellites. We discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the AMA region. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (maximum altitude reached of ∼20.5 km) were conducted with a modified ultra-high-sensitivity aerosol spectrometer – airborne (UHSAS-A; particle diameter detection range of 65 nm to 1 µm), the COndensation PArticle counting System (COPAS, detecting total concentrations of submicrometer-sized particles), and the New Ice eXpEriment – Cloud and Aerosol Spectrometer with Detection of POLarization (NIXE-CAS-DPOL). In the COPAS and UHSAS-A vertical particle mixing ratio (PMR) profiles and the size distribution profiles (for number, surface area, and volume concentration), the ATAL is evident as a distinct layer between ∼370 and 420 K potential temperature (Θ). Within the ATAL, the maximum detected PMRs (from the median profiles) were ∼700 mg−1 for particle diameters between 65 nm and 1 µm (UHSAS-A) and higher than 2500 mg−1 for diameters larger than 10 nm (COPAS). These values are up to 2 times higher than those previously found at similar altitudes in other tropical locations. The difference between the PMR profiles measured by the UHSAS-A and the COPAS indicate that the region below the ATAL at Θ levels from 350 to 370 K is influenced by the nucleation of aerosol particles (diameter <65 nm). We provide detailed analyses of the vertical distribution of the aerosol particle size distributions and the PMR and compare these with previous tropical and extratropical measurements. The backscatter ratio (BR) was calculated based on the aerosol particle size distributions measured in situ. The resulting data set was compared with the vertical profiles of the BR detected by the multiwavelength aerosol scatterometer (MAS) and an airborne miniature aerosol lidar (MAL) aboard the M55 Geophysica and by the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The data of all four methods largely agree with one another, showing enhanced BR values in the altitude range of the ATAL (between ∼15 and 18.5 km) with a maximum at 17.5 km altitude. By means of the AMA-centered equivalent latitude calculated from meteorological reanalysis data, it is shown that such enhanced values of the BR larger than 1.1 could only be observed within the confinement of the AMA.

Chemical composition of the ATAL aerosol measured by in-situ particle mass spectrometry

2020 ◽  
Author(s):  
Oliver Appel ◽  
Andreas Hünig ◽  
Antonis Dragoneas ◽  
Sergej Molleker ◽  
Frank Drewnick ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Chemical Composition ◽  
Particle Diameter ◽  
Aerosol Layer ◽  
Aerosol Mass Spectrometer ◽  
High Particle ◽  
Aerosol Mass ◽  
Ionisation Mass Spectrometry

&lt;p&gt;The Asian Tropopause Aerosol Layer (ATAL) has been found to be an aerosol layer with exceptionally high particle number concentrations in the UT/LS altitude range. During the StratoClim 2017 field campaign in Nepal we deployed the novel in-situ aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols). It combines the methods of laser ablation mass spectrometry with flash vaporization/electron impact ionisation mass spectrometry in a single instrument to analyse the chemical composition of individual aerosol particles or small particle ensembles in the particle diameter range from 100 nm to 2 &amp;#181;m.&lt;/p&gt;&lt;p&gt;The quantitative analysis shows a strong contribution of ammonium nitrate (AN) to the ATAL aerosol concentration. In this layer, the AN concentrations can be as high as 1.5 &amp;#181;g per standard cubic meter. We present the vertical distribution of the mass concentrations of AN as well as other contributing species like sulphate and organics.&lt;/p&gt;&lt;p&gt;The single particle data from the laser ablation module of ERICA show a distinct particle type with nitrate and sulphate ions without the typical components of primary aerosol (soot, dust, metals) within the ATAL, indicating that a significant fraction of the ATAL aerosol consists of secondary particles formed in the upper troposphere.&lt;/p&gt;

scholarly journals A Lagrangian Objective Analysis Technique for Assimilating In Situ Observations with Multiple-Radar-Derived Airflow

2007 ◽  
Vol 135 (7) ◽  
pp. 2417-2442 ◽  
Author(s):  
Conrad L. Ziegler ◽  
Michael S. Buban ◽  
Erik N. Rasmussen
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Potential Temperature ◽  
Cloud Base ◽  
Mixing Ratio ◽  
Lagrangian Analysis ◽  
Analysis Technique ◽  
Virtual Potential Temperature ◽  
Water Vapor Mixing Ratio

Abstract A new Lagrangian analysis technique is developed to assimilate in situ boundary layer measurements using multi-Doppler-derived wind fields, providing output fields of water vapor mixing ratio, potential temperature, and virtual potential temperature from which the lifting condensation level (LCL) and relative humidity (RH) fields are derived. The Lagrangian analysis employs a continuity principle to bidirectionally distribute observed values of conservative variables with the 3D, evolving boundary layer airflow, followed by temporal and spatial interpolation to an analysis grid. Cloud is inferred at any grid point whose height z &gt; zLCL or equivalently where RH ≥ 100%. Lagrangian analysis of the cumulus field is placed in the context of gridded analyses of visible satellite imagery and photogrammetric cloud-base area analyses. Brief illustrative examples of boundary layer morphology derived with the Lagrangian analysis are presented based on data collected during the International H2O Project (IHOP): 1) a dryline on 22 May 2002; 2) a cold-frontal–dryline “triple point” intersection on 24 May 2002. The Lagrangian analysis preserves the sharp thermal gradients across the cold front and drylines and reveals the presence of undulations and plumes of water vapor mixing ratio and virtual potential temperature associated with deep penetrative updraft cells and convective roll circulations. Derived cloud fields are consistent with satellite-inferred cloud cover and cloud-base locations.

scholarly journals Concept for an electrostatic focusing device for continuous ambient pressure aerosol concentration

2019 ◽  
Vol 12 (6) ◽  
pp. 3395-3402
Author(s):  
Joseph L. Woo ◽  
Neha Sareen ◽  
Allison N. Schwier ◽  
V. Faye McNeill
Keyword(s):  
Continuous Flow ◽  
Ambient Pressure ◽  
Aerosol Particles ◽  
Particle Diameter ◽  
Aerosol Concentration ◽  
Submicron Particles ◽  
Virtual Impactors ◽  
Unipolar Charger ◽  
Prototype Design

Abstract. We present a concept for enhancing the concentration of charged submicron aerosol particles in a continuous-flow stream using in situ electrostatic focusing. It is proposed that electrostatic focusing can enable the continuous, isothermal concentration of aerosol particles at ambient pressure, without altering their chemical composition. We model this approach theoretically and demonstrate proof of concept via laboratory measurements using a prototype. The prototype design consists of a nozzle-probe flow system analogous to a virtual impactor. The device was tested in the laboratory using submicron, monodisperse stearic acid particles. Particles were charged using a unipolar charger then concentrated using a cylindrical electrostatic immersion lens to direct the charged submicron particles into the sample probe. Under applied lens voltages ranging from 0 V to 30 kV, aerosol concentration increased up to 15 %. Observed particle enrichment varied as a function of voltage and particle diameter. These results suggest that an imposed electric field can be used to increase aerosol concentration in a continuous flow. This approach shows promise in increasing the effective enriched size range of virtual impactors or other continuous-flow methods of collection.

scholarly journals Efficient transport of tropospheric aerosol into the stratosphere via the Asian summer monsoon anticyclone

2017 ◽  
Vol 114 (27) ◽  
pp. 6972-6977 ◽  
Author(s):  
Pengfei Yu ◽  
Karen H. Rosenlof ◽  
Shang Liu ◽  
Hagen Telg ◽  
Troy D. Thornberry ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Model Simulation ◽  
Asian Summer Monsoon ◽  
Volcanic Eruptions ◽  
Aerosol Layer ◽  
Upper Troposphere ◽  
Tropospheric Aerosol ◽  
Asian Summer

An enhanced aerosol layer near the tropopause over Asia during the June–September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.

scholarly journals Concept for an electrostatic focusing device for continuous ambient pressure aerosol concentration

2019 ◽  
Author(s):  
Joseph L. Woo ◽  
Neha Sareen ◽  
Allison N. Schwier ◽  
V. Faye McNeill
Keyword(s):  
Continuous Flow ◽  
Ambient Pressure ◽  
Aerosol Particles ◽  
Particle Diameter ◽  
Aerosol Concentration ◽  
Submicron Particles ◽  
Virtual Impactors ◽  
Unipolar Charger ◽  
Prototype Design

Abstract. We present a concept for enhancing the concentration of charged submicron aerosol particles in a continuous flow stream using in situ electrostatic focusing. It is proposed that electrostatic focusing can enable the continuous, isothermal concentration of aerosol particles at ambient pressure, without altering their chemical composition. We model this approach theoretically and demonstrate proof-of-concept via laboratory measurements using a prototype. The prototype design consists of a nozzle-probe flow system analogous to a virtual impactor. The device was tested in the laboratory using submicron, monodisperse stearic acid particles. Particles were charged using a unipolar charger, then concentrated using a cylindrical electrostatic immersion lens to direct the charged submicron particles into the sample probe. Under applied lens voltages ranging from 0 V to 30 kV, aerosol concentration increased up to 15 %. Observed particle enrichment varied as a function of voltage and particle diameter. These results suggest that an imposed electric field can be used to increase aerosol concentration in a continuous flow. This approach shows promise in increasing the effective enriched size range of virtual impactors or other continuous-flow methods of collection.

Numerical simulation of the dynamic formation process of fog-haze and smog in transport tunnels of a hot mine

2016 ◽  
Vol 26 (8) ◽  
pp. 1062-1069 ◽  
Author(s):  
Sheng-hua Zou ◽  
Kong-qing Li ◽  
Qiao-yun Han ◽  
Chuck Wah Yu
Keyword(s):  
Wind Speed ◽  
Numerical Modelling ◽  
Coal Mine ◽  
Aerosol Particles ◽  
Geometric Mean ◽  
Particle Diameter ◽  
Monte Carlo Algorithm ◽  
Hunan Province ◽  
Air Conditioner

Fog-haze and smog can be formed in transport tunnels during artificial cooling by air-conditioner, under hot and high humidity conditions inside a coal mine. The processes of coagulation, condensation, nucleation, crushing and evaporation, which can occur at the same time, can be simulated by a dynamic model. The relationship between the particle size distribution over time and environmental parameters such as wind speed, temperature and relative humidity, during smog formation in transport tunnels in a coal mine was characterised by our numerical modelling and in-situ study of a coal mine in Hunan Province, China. The development and dissipation of fog-haze and smog when under cooling inside a deep coal mine were modelled using multiple Monte Carlo algorithm method validated by our experiment using a 1 m3 wooden chamber. Our numerical modelling was confirmed by our in-situ measurement results, indicating that (1) the bigger the condensation coefficient would lead to a faster formation of aerosol particles giving larger number and sizes of particles; (2) faster wind speed would reduce the number of aerosol particles and increase the geometric mean of the particle diameter. (3) When cooling in the tunnels, 2 m/s would be the lowest wind speed that could disperse the haze in the transport tunnels in the mine. The findings of our research should provide the theoretical basis for artificial cooling and controlling of the formation of haze in transport tunnels for mining.

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