Data processing and case study analysis of thunderstorm studies

A case study analysis of the anvil top structure of a May 19,1984, thunderstorm was performed. Wind data were both listed and plotted as time series of direction, horizontal velocity, and vertical velocity. A two-dimensional display of the horizontal winds along the flight track was also provided. The microphysical, dynamic, and thermodynamic characteristics of the overshooting tops and the downwind cirrus anvil top were studied. This included spatial and temporal distributions of cloud particle types and concentrations, horizontal and vertical wind in the cloud and its vinicity, and profiles of thermodynamic parameters

Chemical characteristics of ice residual nuclei in anvil cirrus clouds: evidence for homogeneous and heterogeneous ice formation

International audienceA counterflow virtual impactor was used to collect and analyze residual particles from anvil cirrus clouds generated over the state of Florida in the southern United States. A wide variety of particle types were found, including salts, crustal material, industrial metals, carbonaceous particles, and sulfates. Ambient aerosol particles near the anvils were found to have similar compositions, indicating that anvils act to redistribute particles over large regions of the atmosphere. Sampling occurred at a range of altitudes spanning temperatures from ?21 to ?56°C. More insoluble (crustal and metallic) particles typical of heterogeneous ice nuclei were found in ice crystals at warmer temperatures, while more soluble salts and sulfates were present at cold temperatures. At temperatures below about ?35 to ?40°C, soluble nuclei outnumbered insoluble nuclei, reflecting the transition from primarily heterogeneous to primarily homogeneous freezing as a source of anvil ice

Chemical characteristics of ice residual nuclei in anvil cirrus clouds: evidence for homogeneous and heterogeneous ice formation

A counterflow virtual impactor was used to collect residual particles larger than about 0.1 μm diameter from anvil cirrus clouds generated over Florida in the southern United States. A wide variety of particle types were found. About one-third of the nuclei were salts, with varying amounts of crustal material, industrial metals, carbonaceous particles, and sulfates. Ambient aerosol particles near the anvils were found to have similar compositions, indicating that anvils act to redistribute particles over large regions of the atmosphere. Sampling occurred at a range of altitudes spanning temperatures from −21 to −56°C. More insoluble (crustal and metallic) particles typical of heterogeneous ice nuclei were found in ice crystals at warmer temperatures, while more soluble salts and sulfates were present at cold temperatures. At temperatures below about −35 to −40°C, soluble nuclei outnumbered insoluble nuclei, evidently reflecting the transition from primarily heterogeneous to primarily homogeneous freezing as a source of anvil ice

Cirrus microphysics observations made during FIRE 2: Small particles, high concentrations, and probe comparisons

Aircraft observations of cirrus cloud microphysics were made near Coffeyville, Kansas during Nov. and Dec. 1991. Cloud microphysics measurements were made using both a PMS 2DC probe and an ice particle replicator, both were mounted on the UND Citation aircraft. Intercomparison is made of the size, area, and ice mass spectra determined from these probes. The PMS 2DC undercounts particles for D less than 70 microns and the replicator oversizes particles for D greater than 150 microns, at least when column rosettes are encountered. High concentrations of particles with D less than 50 microns are noted in selected portions of the 22 Nov. 91 replicator data set. Relations between the maximum dimension of a crystal and its shadow area (known as area dimensional relationships) are computed from the PMS data. Area and mass dimensional relationships are used to give a simple analytical expression for computing the wavelength dependent absorption coefficient averaged over a size bin. Calculations based upon the replicator data show that crystals with D less than 50 microns contribute significantly to the solar extinction and infrared absorption coefficients during some time intervals

Evidence for the Predominance of Mid-Tropospheric Aerosols as Subtropical Anvil Cloud Nuclei

NASA's recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment focused on anvil cirrus clouds, an important but poorly understood element of our climate system. The data obtained included the first comprehensive measurements of aerosols and cloud particles throughout the atmospheric column during the evolution of multiple deep convective storm systems. Coupling these new measurements with detailed cloud simulations that resolve the size distributions of aerosols and cloud particles, we found several lines of evidence indicating that most anvil crystals form on mid-tropospheric rather than boundary-layer aerosols. This result defies conventional wisdom and suggests that distant pollution sources may have a greater effect on anvil clouds than do local sources

An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin

This is the final version. Available on open access from the European Geosciences Union via the DOI in this recordData availability: All ORACLES data are accessible via the digital object identifiers (DOIs) provided under ORACLES Science Team (2020a–d) references: https://doi.org/10.5067/Suborbital/ORACLES/P3/2018_V2 (ORACLES Science Team, 2020a), https://doi.org/10.5067/Suborbital/ORACLES/P3/2017_V2 (ORACLES Science Team, 2020b), https://doi.org/10.5067/Suborbital/ORACLES/P3/2016_V2 (ORACLES Science Team, 2020c), and https://doi.org/10.5067/Suborbital/ORACLES/ER2/2016_V2 (ORACLES Science Team, 2020d). The only exceptions are noted as footnotes to Table B2.Southern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ∼350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ∼100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.NAS

Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments

This is the final version. Available on open access from the European Geosciences Union via the DOI in this recordCode availability: Processing code for the FAAM core measurements suite is available from GitHub (Sproson et al., 2020).Data availability Airborne data for the CLARIFY campaign are available from the Centre for Environmental Data Analysis (Facility for Airborne Atmospheric Measurements et al., 2017) and for the ORACLES campaign from NASA Earth Science Project Office (ORACLES Science Team, 2020). The LASIC ground-based data sets are publicly available from the Atmospheric Radiation Measurement Climate Research Facility (Zuidema et al., 2017) with specialist data sets available for the following: SP2 – https://iop.archive.arm.gov/arm-iop/2016/ (last access: 25 October 2022, Sedlacek, 2017), CO – https://doi.org/10.5439/1046183 (Springston, 2018b), CAPS PMSSA – https://adc.arm.gov/discovery/#/results/s::caps-ssa (Onasch et al., 2015), ACSM – https://doi.org/10.5439/1763029 (Zawadowicz and Howie, 2021).Data are presented from intercomparisons between two research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between the BAe-146 and the surface-based DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) Mobile Facility at Ascension Island (8∘ S, 14.5∘ W; a remote island in the mid-Atlantic). These took place from 17 August to 5 September 2017, during the African biomass burning (BB) season. The primary motivation was to give confidence in the use of data from multiple platforms with which to evaluate numerical climate models. The three platforms were involved in the CLouds–Aerosol–Radiation Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons from flight segments on 6 d where the BAe-146 flew alongside the ARM facility on Ascension Island are presented, along with comparisons from the wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017. The intercomparison flight sampled a relatively clean atmosphere overlying a moderately polluted boundary layer, while the six fly-bys of the ARM site sampled both clean and polluted conditions 2–4 km upwind. We compare and validate characterisations of aerosol physical, chemical and optical properties as well as atmospheric radiation and cloud microphysics between platforms. We assess the performance of measurement instrumentation in the field, under conditions where sampling conditions are not as tightly controlled as in laboratory measurements where calibrations are performed. Solar radiation measurements compared well enough to permit radiative closure studies. Optical absorption coefficient measurements from all three platforms were within uncertainty limits, although absolute magnitudes were too low (<10 Mm−1) to fully support a comparison of the absorption Ångström exponents. Aerosol optical absorption measurements from airborne platforms were more comparable than aircraft-to-ground observations. Scattering coefficient observations compared adequately between airborne platforms, but agreement with ground-based measurements was worse, potentially caused by small differences in sampling conditions or actual aerosol population differences over land. Chemical composition measurements followed a similar pattern, with better comparisons between the airborne platforms. Thermodynamics, aerosol and cloud microphysical properties generally agreed given uncertainties.Natural Environment Research Council (NERC)NERC/Met Office Industrial Case studentshipResearch Council of NorwayUS Department of Energy, Office of ScienceNASAUS Department of Energy Atmospheric Systems Research (ASR) programm