Balloon borne aerosol-cloud interaction studies (BACIS): New observational techniques to understand and quantify aerosol effects on clouds

Abstract. Better understanding of aerosol-cloud interaction processes is an important aspect to quantify the role of clouds and aerosols in the climate system. There have been significant efforts to explain the ways aerosols modulate cloud properties. However, from the observational point of view, it is indeed challenging to observe and/or verify some of these processes because no single instrument or platform is proven sufficient. With this motivation, a unique set of observational field campaigns named Balloon borne Aerosol Cloud Interaction Studies (BACIS) is proposed and conducted using balloon borne in-situ measurements in addition to the ground-based (Lidars, MST radar, LAWP, MWR, Ceilometer) and space borne (CALIPSO) remote sensing instruments from Gadanki (13.45° N, 79.2° E). So far, 15 campaigns have been conducted as a part of BACIS campaigns from 2017 to 2020. This paper presents the concept of observational approach, lists the major objectives of the campaigns, describes the instruments deployed, and discusses results from selected campaigns. Consistency in balloon borne measurements is assessed using the data from simultaneous observations of ground-based, space borne remote sensing instruments. A good agreement is found among multi-instrumental observations. Balloon borne in-situ profiling is found to complement the information provided by ground-based and/or space borne measurements. A combination of the Compact Optical Backscatter AerosoL Detector (COBALD) and Cloud Particle Sensor (CPS) sonde is employed for the first time to discriminate cloud and aerosol in an in-situ profile. A threshold value of COBALD color index (CI) for ice clouds is found to be between 18 and 20 and CI values for coarse mode aerosol particle range between 11 and 15. Using the data from balloon measurements, the relationship between cloud and aerosol is quantified for the liquid clouds. A statistically significant slope (aerosol-cloud interaction index) of 0.77 (0.86) found between aerosol back scatter from 300 m (400 m) below the cloud base and cloud particle count within the cloud indicates the role of aerosol in the cloud activation process. In a nutshell, the results presented here demonstrate the observational approach to quantify aerosol-cloud interactions and paves the way for further investigations using the approach.

Download Full-text

Improvement of airborne retrievals of cloud droplet number concentration of trade wind cumulus using a synergetic approach

Atmospheric Measurement Techniques ◽

10.5194/amt-12-1635-2019 ◽

2019 ◽

Vol 12 (3) ◽

pp. 1635-1658 ◽

Cited By ~ 3

Author(s):

Kevin Wolf ◽

André Ehrlich ◽

Marek Jacob ◽

Susanne Crewell ◽

Martin Wirth ◽

...

Keyword(s):

Remote Sensing ◽

Cloud Droplet ◽

Number Concentration ◽

Cloud Base ◽

Trade Wind ◽

Liquid Water Path ◽

Cloud Properties ◽

Research Aircraft ◽

Cloud Droplet Number Concentration

Abstract. In situ measurements of cloud droplet number concentration N are limited by the sampled cloud volume. Satellite retrievals of N suffer from inherent uncertainties, spatial averaging, and retrieval problems arising from the commonly assumed strictly adiabatic vertical profiles of cloud properties. To improve retrievals of N it is suggested in this paper to use a synergetic combination of passive and active airborne remote sensing measurement, to reduce the uncertainty of N retrievals, and to bridge the gap between in situ cloud sampling and global averaging. For this purpose, spectral solar radiation measurements above shallow trade wind cumulus were combined with passive microwave and active radar and lidar observations carried out during the second Next Generation Remote Sensing for Validation Studies (NARVAL-II) campaign with the High Altitude and Long Range Research Aircraft (HALO) in August 2016. The common technique to retrieve N is refined by including combined measurements and retrievals of cloud optical thickness τ, liquid water path (LWP), cloud droplet effective radius reff, and cloud base and top altitude. Three approaches are tested and applied to synthetic measurements and two cloud scenarios observed during NARVAL-II. Using the new combined retrieval technique, errors in N due to the adiabatic assumption have been reduced significantly.

Download Full-text

Threshold Value of Particle Concentration in EPD: Experimental Evidence with TiO2 Organic Suspensions

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.412.51 ◽

2009 ◽

Vol 412 ◽

pp. 51-56 ◽

Cited By ~ 3

Author(s):

Simona Radice ◽

Stefano Mischler ◽

Johann Michler

Keyword(s):

Particle Concentration ◽

Deposition Time ◽

Threshold Value ◽

Deposition Process ◽

Suspension Systems ◽

Limit Value ◽

Coating Formation ◽

Concentration Threshold

This study was triggered by our experience on electrophoretic deposition (EPD) with different suspension systems showing evidence of a particle concentration threshold, below which no deposit was formed. In this study, the role of particle concentration in the mechanism of EPD was investigated with a model system, consisting of isopropanol suspensions with TiO2 nanosized particles (d50 = 130 nm). The investigated concentration range was 0.01 - 0.4 vol% TiO2. Constant voltage EPD tests with variable particle concentration were performed for 1 min under different applied voltages (25 - 300 V corresponding to 62.5 - 750 V/cm). A longer deposition time (30 min) was tested for a lower concentration value (0.003 vol% TiO2). The deposition process was evaluated in situ by means of the current measured during EPD. The deposits obtained were characterized by weight and profile measurements and scanning electron microscope (SEM). The results confirmed the finding of a lower limit value of particle concentration, determining a threshold in the formation of an EPD coating. Above this threshold, proportionality between deposited mass and particle concentration was observed, in agreement with the equation of Hamaker. Below this threshold, the proportionality was lost with evidence of a lack of coating formation. A possible interpretation for this experimental finding was provided.

Download Full-text

On the imprint of the mesoscale organization of tradewind clouds at cloud base and below

10.5194/egusphere-egu21-14901 ◽

2021 ◽

Author(s):

Sandrine Bony ◽

Pierre-Etienne Brilouet ◽

Patrick Chazette ◽

Pierre Coutris ◽

Julien Delanoë ◽

...

Keyword(s):

Large Scale ◽

Lower Troposphere ◽

Cloud Base ◽

Trade Wind ◽

Tropical Atlantic ◽

Lidar Measurements ◽

Research Aircraft ◽

Cloud Patterns

Trade-wind clouds can exhibit different patterns of mesoscale organization. These patterns were observed during the EUREC4A (Elucidating the role of cloud-circulation coupling in climate) field campaign that took place in Jan-Feb 2020 over the western tropical Atlantic near Barbados: while the HALO aircraft was observing clouds from above and was characterizing the large-scale environment with dropsondes, the ATR-42 research aircraft was flying in the lower troposphere, characterizing clouds and turbulence with horizontal radar-lidar measurements and in-situ probes and sensors. By analyzing these data for different cloud patterns, we investigate the extent to which the cloud organization is imprinted in cloud-base properties and subcloud-layer heterogeneities. The implications of our findings for understanding the roots of the mesoscale organization of tradewind clouds will be discussed.

Download Full-text

The challenge of simulating the sensitivity of the Amazonian clouds microstructure to cloud condensation nuclei number concentrations

10.5194/acp-2019-474 ◽

2019 ◽

Author(s):

Pascal Polonik ◽

Christoph Knote ◽

Tobias Zinner ◽

Florian Ewald ◽

Tobias Kölling ◽

...

Keyword(s):

Cloud Condensation Nuclei ◽

Regional Scale ◽

Cloud Droplet ◽

Number Concentration ◽

Effective Radius ◽

Cloud Base ◽

Condensation Nuclei ◽

Aerosol Cloud ◽

Microphysical Properties

Abstract. The realistic representation of cloud-aerosol interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon area has been one of the motivations for several field observations, including the airborne Aerosol, Cloud, Precipitation, and Radiation Interactions and DynamIcs of CONvective cloud systems – Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA) campaign based in Manaus, Brazil in September 2014. In this work we combine in situ and remotely sensed aerosol, cloud, and atmospheric radiation data collected during ACRIDICON-CHUVA with regional, online-coupled chemistry-transport simulations to evaluate the model’s ability to represent the indirect effects of biomass burning aerosol on cloud microphysical properties (droplet number concentration and effective radius). We found agreement between modeled and observed median cloud droplet number concentrations (CDNC) for low values of CDNC, i.e., low levels of pollution. In general, a linear relationship between modeled and observed CDNC with a slope of two was found, which means a systematic underestimation of modeled CDNC as compared to measurements. Variability in cloud condensation nuclei (CCN) number concentrations and cloud droplet effective radii (reff) was also underestimated by the model. Modeled effective radius profiles began to saturate around 500 CCN per cm3 at cloud base, indicating an upper limit for the model sensitivity well below CCN concentrations reached during the burning season in the Amazon Basin. Regional background aerosol concentrations were sufficiently high such that the additional CCN emitted from local fires did not cause a notable change in modelled cloud microphysical properties. In addition, we evaluate a parameterization of CDNC at cloud base using more readily available cloud microphysical properties, aimed at in situ observations and satellite retrievals. Our study casts doubt on the validity of regional scale modeling studies of the cloud albedo effect in convective situations for polluted situations where the number concentration of CCN is greater than 500 cm−3.

Download Full-text

Improving our fundamental understanding of the role of aerosol−cloud interactions in the climate system

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1514043113 ◽

2016 ◽

Vol 113 (21) ◽

pp. 5781-5790 ◽

Cited By ~ 199

Author(s):

John H. Seinfeld ◽

Christopher Bretherton ◽

Kenneth S. Carslaw ◽

Hugh Coe ◽

Paul J. DeMott ◽

...

Keyword(s):

Remote Sensing ◽

Radiative Forcing ◽

General Circulation ◽

Climate Models ◽

Large Range ◽

General Circulation Models ◽

Radiative Properties ◽

Aerosol Cloud ◽

Aerosol Cloud Interactions

The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth’s clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol−cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol−cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol−cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.

Download Full-text

Role of Satellite Technology in Oceanic Study

Sustainable Development and India ◽

10.1093/oso/9780199474622.003.0006 ◽

2018 ◽

pp. 80-103

Author(s):

Thomas Mathew

Keyword(s):

Remote Sensing ◽

Electromagnetic Radiation ◽

Crucial Role ◽

Near Infrared ◽

Thermal Infrared ◽

Microwave Region ◽

Satellite Technology ◽

The Earth

The three-fourth surface of the earth is covered with ocean. The study of the ocean is important for sustainable overall development of a nation and world at large in view of it being rich in resources and playing a crucial role in the climate of the region and changes associated with it. The space-based observations assume significance, as it provides synoptic and repetitive coverage of the ocean in contrast to the sparse and isolated in-situ buoy or ship observations. The remote sensing of the ocean with the help of satellite or satellite oceanography has many other applications also. The electromagnetic radiation in the visible, near infrared, thermal infrared, and microwave regions are used by the sensors on-board space platforms to measure the diverse physical, biological, and geological parameters of the ocean. Amongst the various electromagnetic regions, the microwave region plays an important role in the study of the ocean.

Download Full-text

Ground-Based Remote Sensing of Cloud Particle Sizes during the 26 November 1991 FIRE II Cirrus Case: Comparisons with In Situ Data

Journal of the Atmospheric Sciences ◽

10.1175/1520-0469(1995)052<4128:gbrsoc>2.0.co;2 ◽

1995 ◽

Vol 52 (23) ◽

pp. 4128-4142 ◽

Cited By ~ 8

Author(s):

S. Y. Matrosov ◽

A. J. Heymsfield ◽

J. M. Intrieri ◽

B. W. Orr ◽

J. B. Snider

Keyword(s):

Remote Sensing ◽

Particle Sizes ◽

Cloud Particle ◽

In Situ Data

Download Full-text

Airborne observations of a subvisible midlevel Arctic ice cloud: microphysical and radiative characterization

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-595-2009 ◽

2009 ◽

Vol 9 (1) ◽

pp. 595-634

Author(s):

A. Lampert ◽

A. Ehrlich ◽

A. Dörnbrack ◽

O. Jourdan ◽

J.-F. Gayet ◽

...

Keyword(s):

Remote Sensing ◽

Thermal Infrared ◽

Airborne Lidar ◽

Radiative Properties ◽

The Arctic ◽

Cloud Base ◽

Effective Diameter ◽

Ice Cloud ◽

Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed at around 3 km altitude south of Svalbard. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in-situ instruments. Collocated airborne lidar remote-sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in-situ sensors roughly 30 min later. From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, we retrieved the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population. Furthermore, a lidar ratio of 21 (±6) sr was deduced by two independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared) radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range).

Download Full-text

CALIPSO (IIR–CALIOP) retrievals of cirrus cloud ice-particle concentrations

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-17325-2018 ◽

2018 ◽

Vol 18 (23) ◽

pp. 17325-17354 ◽

Cited By ~ 9

Author(s):

David L. Mitchell ◽

Anne Garnier ◽

Jacques Pelon ◽

Ehsan Erfani

Keyword(s):

Remote Sensing ◽

Satellite Remote Sensing ◽

Ice Crystals ◽

Cloud Base ◽

Effective Diameter ◽

Cirrus Cloud ◽

Base Temperature ◽

High Latitudes ◽

Cloud Ice

Abstract. A new satellite remote sensing method is described whereby the sensitivity of thermal infrared wave resonance absorption to small ice crystals is exploited to estimate cirrus cloud ice-particle number concentration N, effective diameter De and ice water content IWC. This method uses co-located observations from the Infrared Imaging Radiometer (IIR) and from the CALIOP (Cloud and Aerosol Lidar with Orthogonal Polarization) lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) polar orbiting satellite, employing IIR channels at 10.6 and 12.05 µm. Using particle size distributions measured over many flights of the TC4 (Tropical Composition, Cloud and Climate Coupling) and the mid-latitude SPARTICUS (Small Particles in Cirrus) field campaigns, we show for the first time that N∕IWC is tightly related to βeff; the ratio of effective absorption optical depths at 12.05 and 10.6 µm. Relationships developed from in situ aircraft measurements are applied to βeff derived from IIR measurements to retrieve N. This satellite remote sensing method is constrained by measurements of βeff from the IIR and is by essence sensitive to the smallest ice crystals. Retrieval uncertainties are discussed, including uncertainties related to in situ measurement of small ice crystals (D<15 µm), which are studied through comparisons with IIR βeff. The method is applied here to single-layered semi-transparent clouds having a visible optical depth between about 0.3 and 3, where cloud base temperature is ≤235 K. CALIPSO data taken over 2 years have been analyzed for the years 2008 and 2013, with the dependence of cirrus cloud N and De on altitude, temperature, latitude, season (winter vs. summer) and topography (land vs. ocean) described. The results for the mid-latitudes show a considerable dependence on season. In the high latitudes, N tends to be highest and De smallest, whereas the opposite is true for the tropics. The frequency of occurrence of these relatively thick cirrus clouds exhibited a strong seasonal dependence in the high latitudes, with the occurrence frequency during Arctic winter being at least twice that of any other season. Processes that could potentially explain some of these micro- and macroscopic cloud phenomena are discussed.

Download Full-text

Bulk Scattering Properties for the Remote Sensing of Ice Clouds. Part I: Microphysical Data and Models

Journal of Applied Meteorology ◽

10.1175/jam2308.1 ◽

2005 ◽

Vol 44 (12) ◽

pp. 1885-1895 ◽

Cited By ~ 196

Author(s):

Bryan A. Baum ◽

Andrew J. Heymsfield ◽

Ping Yang ◽

Sarah T. Bedka

Keyword(s):

Remote Sensing ◽

Particle Size ◽

In Situ Measurements ◽

Two Dimensional ◽

Cloud Particle ◽

Ice Clouds ◽

Sensing Applications ◽

Airborne Sampling ◽

Bulk Scattering

Abstract This study reports on the use of in situ data obtained in midlatitude and tropical ice clouds from airborne sampling probes and balloon-borne replicators as the basis for the development of bulk scattering models for use in satellite remote sensing applications. Airborne sampling instrumentation includes the two-dimensional cloud (2D-C), two-dimensional precipitation (2D-P), high-volume precipitation spectrometer (HVPS), cloud particle imager (CPI), and NCAR video ice particle sampler (VIPS) probes. Herein the development of a comprehensive set of microphysical models based on in situ measurements of particle size distributions (PSDs) is discussed. Two parameters are developed and examined: ice water content (IWC) and median mass diameter Dm. Comparisons are provided between the IWC and Dm values derived from in situ measurements obtained during a series of field campaigns held in the midlatitude and tropical regions and those calculated from a set of modeled ice particles used for light-scattering calculations. The ice particle types considered in this study include droxtals, hexagonal plates, solid columns, hollow columns, aggregates, and 3D bullet rosettes. It is shown that no single habit accurately replicates the derived IWC and Dm values, but a mixture of habits can significantly improve the comparison of these bulk microphysical properties. In addition, the relationship between Dm and the effective particle size Deff, defined as 1.5 times the ratio of ice particle volume to projected area for a given PSD, is investigated. Based on these results, a subset of microphysical models is chosen as the basis for the development of ice cloud bulk scattering models in Part II of this study.

Download Full-text