Advancing Aerosol-Cloud-Meteorology Knowledge through ACTIVATE

Advancing Aerosol-Cloud-Meteorology Knowledge through ACTIVATE

Despite the crucial role of clouds in maintaining the Earth’s energy balance and water cycle, their formation and evolution processes still have large uncertainties among the international scientific research community. Expanding knowledge on the relationships between aerosols and clouds is key to understanding different cloud properties and their resulting impact on climate and weather. The Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) aims to provide a unique dataset of aerosol-cloud-meteorology interactions for international model intercomparison and improvement, in addition to process-based studies. In an innovative approach based upon the results of numerous previous field studies, ACTIVATE generates statistics of aerosols and clouds under a wide range of meteorological conditions to address its scientific objectives. ACTIVATE will quantify aerosol and cloud relationships, reduce model uncertainty, improve understanding of the factors governing cloud micro/macro-physical properties and their relationships to cloud effects on aerosol, and improve remote sensing capabilities. ACTIVATE’s approach more effectively exploits the airborne sampling advantages and mitigates the previous known limitations. To achieve the sampling objectives, ACTIVATE employs two aircraft, the King Air and the HU-25. The King Air aircraft is equipped with remote sensing instrumentation and dropsondes while the HU-25 is equipped with an extensive instrument payload for in-situ measurements of aerosol, cloud properties, and meteorological parameters, as well as several trace gas measurements. The dual aircraft approach allows more comprehensive characterization of aerosol and cloud properties in a single atmospheric column at the same time and enables a sampling strategy consisting of “statistical surveys” (Figure 1) and mechanistic process studies. This research will advance knowledge of atmospheric composition, the Earth’s water and energy cycle, climate variability and change, and weather.

ACTIVATE Nominal Profile Figure

Figure 1. Nominal profile of a single cloud ensemble conducted with ACTIVATE’s dual aircraft approach. The HU-25 Falcon conducts in situ measurements of gases, aerosols, clouds, and meteorological parameters in the lower troposphere where boundary layer clouds evolve, whereas the King Air flies higher, at ~9 km, in a coordinated fashion to provide remote sensing data in the same vertical column while launching dropsondes along the flight track. A single flight including multiple ensembles of this approach are called “statistical survey” flights, which amount to about 90% of all ACTIVATE flights with the rest being process study flights with different flight designs. Image Source: ACTIVATE Science Team

The Atmospheric Science Data Center (ASDC) at NASA Langley Research Center will archive ACTIVATE data throughout the campaign. At this time, all current publication-quality data from the first five deployments of ACTIVATE can be accessed via the Sub-Orbital Order Tool (SOOT) and the ASDC ACTIVATE project landing page. Additional publication-quality data will become available soon.


Image Source:


Spatial Coverage:

(25°–50°N, 60°–85°W)

Temporal Coverage:


Scientific Objectives

  1. Quantify relationships between number concentrations of aerosol (Na), cloud condensation nuclei (CCN), and cloud droplets (Nd) and reduce uncertainty in model cloud droplet activation parameterizations.
  2. Expand process-level understanding and model representation of factors controlling cloud properties and their relationships with cloud effects on aerosol.
  3. Improve remote sensing capabilities in the retrieval of aerosol and cloud properties that relate to aerosol-cloud interactions.

Instruments Used

Two aircraft, the HU-25 Falcon and the King Air, are used to collect data for ACTIVATE. Each aircraft is equipped with an extensive suite of instrumentation detailed in the table below.

Platform Type Platform Relevant Instrument Study Area

Airborne  Platform

HU-25 Falcon

1. TSI Condensation Particle Counters

TSI Scanning Mobility Particle Sizer (SMPS)

TSI Laser Aerosol Sizer (LAS)

TSI Nephelometer (TSI Neph)

f(RH) System: TSI 3563 Nephelometers and RH Controlled Humidifier

Particle Soot Absorption Photometer (PSAP)

Particle Into Liquid Sampler (PILS)

High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS)

2. DMT Cloud Condensation Nuclei Spectrometer (CCN)

DMT Cloud Droplet Probe (CDP) and Cloud and Aerosol Spectrometer (CAS)

DMT Cloud Imagery Probe (CIP)

Axial Cyclone Cloud water Collector and offline chemistry (AC3)

3. Turbulent Air Motion Measurement System (TAMMS)

Rosemount Total Temperature Sensor 102 (TTS)

IR Sensor for Sea Surface Temperature


Diode Laser Hygrometer (DLH)

Edgetech frostpoint Hygrometer (cryo)

4. PICARRO Cavity Ring-Down Spectrometer

2B Technologies Ozone Monitor

5. Applanix POS AV

1. Aerosol properties

2. Cloud properties

3. Meteorological state parameters

4. Trace gases

5. Aircraft geolocation and attitude parameters

Airborne  Platform

King Air

1. High Spectral Resolution Lidar 2 (HSRL-2)

Research Scanning Polarimeter (RSP)

2. Dropsondes

3. Applanix POS AV

1. Aerosols and cloud properties

2. Atmospheric profiling

3. Aircraft parameters

Access Data

The ASDC archives and distributes all currently available publication-quality data for ACTIVATE. Data from ACTIVATE can be accessed on the ASDC ACTIVATE landing page, SOOT, as well as on Earthdata Search.

Events of Interest

This section highlights events within the field campaign of particular scientific interest.


The first deployment of ACTIVATE was conducted in the winter of 2020 between February 14, 2020, and March 12, 2020. Several interesting events occurred during the first deployment, including a flight on February 29, 2020, in which forecasts suggested clear air sampling, but instead scientists encountered low clouds during the flight; this event demonstrated the importance of ACTIVATE in improving modeling of marine boundary layer clouds. The winter flights sampled cold air outbreak conditions, which are of special importance as climate models struggle to simulate the postfrontal clouds associated with these conditions. Flights in March included the first coordinated underflight with a satellite overpass that targeted the Advanced Spaceborne Thermal Emission and Reflected Radiometer (ASTER) aboard the Terra satellite.

The first deployment was cut short due to the evolving COVID-19 pandemic, and the second deployment had to be postponed to the August/September time frame rather than the May/June time frame originally planned. During the second deployment, ACTIVATE flights encountered the impacts of the western United States wildfires, particularly those in California. Several flights were conducted in coordination with satellites including the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite and ASTER. Forty flights were conducted during these two deployments, including 35 joint flights.

The third ACTIVATE deployment began in January 2021 and ended in April 2021. The first science flight of the deployment was on January 27 with the first joint flight conducted on February 3. This deployment primarily focused on taking advantage of a higher frequency of cold air outbreak events. The second of the two flights on March 12 was coordinated with a CALIPSO satellite overpass and the final science flight was on April 2, concluding the winter 2021 deployment.

The fourth deployment was conducted from May 13 to June 30, 2021. The first research flight for the summer deployment occurred on May 13. During the deployment, flights were coordinated with CALIPSO and ASTER overpasses, as well as overflights of Langley Research Center to intercompare with the Aerosol Robotics Network (AERONET) site and High-Altitude Lidar Observatory (HALO) HSRL/water vapor lidar. Research Flights 92 and 93 concluded the deployment on June 30.

From October 20-21, 2021, the ACTIVATE team hosted an open data workshop with 70+ participants. Day one focused on access and use of ACTIVATE campaign data, along with a case study on ACTIVATE Research Flight 12, a statistical survey flight. Day 2 highlighted a second case study on Research Flights 13 and 14, both of which were process study flights. Material from the workshop can be found at:

ACTIVATE’s fifth deployment was a two-phased deployment that occurred from November 30 to December 10, 2021, and January 11 to March 29, 2022. This deployment consisted of 53 joint research flights with minimal aircraft and instrument maintenance issues, making it one of the most successful ACTIVATE deployments. Consisting of two phases, deployment five was the equivalent of two winter campaigns to make up for the reduced payload capability on the Falcon in Deployment three. This deployment had one coordinated flight with a CALIPSO overpass and refueling stops in the New England area and Bermuda. The deployment also aimed to collect data on typical wintertime conditions.

The sixth and final deployment of ACTIVATE was conducted from May 3 to June 18, 2022. During this deployment, flights were based out of LaRC for the first few weeks of May before flying out to Bermuda to base operations for the second half of the deployment. The aircraft collected a diverse range of aerosol types including sea salt, marine biogenic, dust (African, Asian, US), smoke, and continental/urban. Thirty-one total research flights were completed, including three CALIPSO overpass flights and two ASTER overpass flights. Now that flights for ACTIVATE have concluded, the team will turn their focus to data archival, dissemination, and analysis.

Major Findings

Throughout ACTIVATE, intriguing information has resulted from the data collected. A wide array of conditions were encountered in the flights that may impact cloud formation and evolution including different aerosol sources, varying wind directions, wide-ranging cloud cover conditions, and different precipitation conditions. One example of ACTIVATE’s early findings is that cloud droplet concentration measured by the HU-25 appears to decrease moving away from the coast, confirming satellite observations. These cloud droplet concentrations cover a wide range in values, spanning several orders of magnitude. ACTIVATE studies have shown that reasons contributing to this offshore gradient include precipitation scavenging over the ocean and also the entrainment of air aloft in the free troposphere into the lower part of the atmosphere called the boundary layer, which reduces aerosol concentrations, consistent with satellite-observed trends in droplet number concentration upwind of CAO cloud-regime transitions over the northwest Atlantic. Additionally, in-situ cloud imaging data from early flights illustrates many different ice shapes such as column-like needle structures. Increasing cloud ice likely accelerates transitions from overcast cloud decks to broken cloud fields in cold air outbreaks (more information available in this publication by ACTIVATE scientists). Cold air outbreaks have been shown to promote new particle formation with most evidence observed directly above cloud tops. The HSRL-2 lidar has detected unusual aerosol particle properties for the marine boundary layer (more information available in this poster presentation from the American Geophysical Union Fall Meeting of 2020), which has major implications for satellite aerosol typing from the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) instrument aboard the (CALIPSO) satellite.

Members of the ACTIVATE team have delivered a number of presentations at conferences such as those of the American Geophysical Union (AGU), with some listed below.

Relevant Publications

The following is a sample of ACTIVATE publications, for the full list visit the ACTIVATE Publication Webpage:


Brunke, M., Cutler, L., Urzua, R. D., Corral, A., Crosbie, E., Hair, J., Hostetler, C., Kirschler, S., Larson, V., Li, X., Ma, P., Minke, A., Moore, R., Robinson, C., Scarino, A., Schlosser, J., Shook, M., Sorooshian, A., Thornhill, K., Voigt, C., Wan, H., Wang, H., Winstead, E., Zeng, X., Zhang, S., Ziemba, L.: Aircraft Observations of Turbulence in Cloudy and Cloud-Free Boundary Layers Over the Western North Atlantic Ocean From ACTIVATE and Implications for the Earth System Model Evaluation and Development, Journal of Geophysical Research: Atmospheres, 127, e2022JD036480,, 2022.

Corral, A., Choi, Y., Collister, B., Crosbie, E., Dadashazar, H., DiGangi, J., Diskin, G., Fenn, M., Kirschler, S., Moore, R., Nowak, J., Shook., M., Stahl, C., Shingler, T., Thornhill, K., Voigt, C., Ziemba, L., Sorooshian, A.: Dimethylamine in Cloud Water: A Case Study Over the Northwest Atlantic Ocean, Environmental Science: Atmospheres, Accepted.

Dadashazar, H., Crosbie, E., Choi, Y., Corral, A., DiGangi, J. P., Diskin, G., Dmitrovic, S., Kirschler, S., McCauley, K., Moore, R., Nowak, J., Robinson, C., Schlosser, J., Shook. M., Thornhill, K. L., Voigt, C., Winstead, E., Ziemba, L., Sooroshian, A., Analysis of MONARC and ACTIVATE Airborne Aerosol Data for Aerosol-Cloud Interaction Investigations: Efficacy of Stairstepping Flight Legs for Airborne In Situ Sampling, Atmosphere,

Dadashazar, H., Corral, A., Crosbie, E., Dmitrovic, S., Kirschler, S., McCauley, K., Moore, R., Robinson, C., Schlosser, J., Shook, M., Thornhill, K., Voigt, C., Winstead, E., Ziemba, L., and Sorooshian, A.: Organic Enrichment in Droplet Residual Particles Relative to Out of Cloud over the Northwest Atlantic: Analysis of Airborne ACTIVATE Data, Atmos. Chem. Phys.,

Chen, J., Wang, H., Li, X., Painemal, D., Sorooshian, S., Thornhill, K. L., Robinson, C., and Shingler, T., Impact of Meteorological Factors on the Mesoscale Morphology of Cloud Streets during a Cold Air Outbreak over the western North Atlantic, J of the Atmos. Sci.,

Christensen, M. W., Gettelman, A., Cermak, J., Dagan, G., Diamond, M., Douglas, A., Feingold, G., Glassmeier, F., Goren, T., Grosvenor, D. P., Gryspeerdt, E., Kahn, R., Li, Z., Ma, P.-L., Malavelle, F., McCoy, I. L., McCoy, D. T., McFarquhar, G., Mülmenstädt, J., Pal, S., Possner, A., Povey, A., Quaas, J., Rosenfeld, D., Schmidt, A., Schrödner, R., Sorooshian, A., Stier, P., Toll, V., Watson-Parris, D., Wood, R., Yang, M., and Yuan, T.: Opportunistic experiments to constrain aerosol effective radiative forcing, Atmos. Chem. Phys., 22, 641–674,, 2022.

Corral, A. F., Choi, Y., Crosbie, E., Dadashazar, H., DiGangi, J. P., Diskin, G. S., et al. (2022). Cold air outbreaks promote new particle formation off the U.S. East Coast. Geophysical Research Letters, 49, e2021GL096073.

Cutler, L., Brunke, M. A., and Zeng, X., Re-evaluation of Low Cloud Amount Relationships with Lower-Tropospheric Stability and Estimated Inversion Strength, Geophysical Research Letters,

Gonzalez, M., Corral, A., Crosbie, E., Dadashazar, H., Diskin, G., Edwards, E., Kirschler, S., Moore, R., Robinson, C., Schlosser, J., Shook, M., Stahl, C., Thornhill, K., Voigt, C., Winstead, E., Ziemba, L., Sorooshian, A., Relationships between supermicrometer particle concentrations and cloud water sea salt and dust concentrations: Analysis of MONARC and ACTIVATE data, Environmental Science: Atmospheres,

Gryspeerdt E., McCoy D. T., Crosbie, E., Moore, R. H., Nott, G. J., Painemal, D., Small-Griswold, J., Sorooshian, A., and Ziemba, L.: The impact of sampling strategies on the cloud droplet number concentration estimated from satellite data, Atmos. Meas. Tech., vol. 15, Issue12,

Kirschler, S., Voigt, C., Anderson, B., Braga, R. C., Chen, G., Corral, A. F., Crosbie, E., Dadashazar, H., Ferrare, R. F., Hahn, V., Hendricks, J., Kaufmann, S., Moore, R., Pöhlker, M. L., Robinson, C., Scarino, A. J., Schollmayer, D., Shook, M. A., Thornhill, K. L., Winstead, E., Ziemba, L. D., and Sorooshian, A., Seasonal updraft speeds change cloud droplet number concentrations in low level clouds over the Western North Atlantic, Atmos. Chem. Phys., 22, 8299-8319,

Schlosser, J. S., Stamnes, S., Burton, S. P. , Cairns, B., Crosbie, E., Van Diedenhoven, B., Diskin, G., Dmitrovic, S., Ferrare, R., Hair, J. W., Hostetler, C. A., Hu, Y., Liu, X., Moore, R. H., Shingler, T., Shook, M. A., Thornhill, K. L., Winstead, E., Ziemba, L., Sorooshian, A.: Polarimeter + Lidar – Derived Aerosol Particle Number Concentration, Frontiers in Remote Sensing,

Tornow, F., Ackerman, A. S., Fridlind, A. M., Cairns, B., Crosbie, E. C. , Kirschler, S., Moore, R. H., Painemal, D., Robinson, C. E., Seethala, C., Shook, M. A., Voigt, C., Winstead, E. L., Ziemba, L. D., Zuidema, P., Sorooshian, A., Dilution of boundary layer cloud condensation nucleus concentrations by free tropospheric entrainment during marine cold air outbreaks, Geophysical Research Letters,

Xu, Y., Alejandro, J., Hernandez, A. O., Zeng, X., Precipitation over the US Coastal Land/Water Using Gauge-Corrected Multi-Radar Multi-Sensor System and Three Satellite Products, Remote Sensing,


Aldhaif, A. M., Lopez, D. H., Dadashazar, H., Painemal, D., Peters, A. J., and Sorooshian, A.: An Aerosol Climatology and Implications for Clouds at a Remote Marine Site: Case Study Over Bermuda, Journal of Geophysical Research: Atmospheres, 126, e2020JD034038,, 2021.

Braun, R. A., McComiskey, A., Tselioudis, G., Tropf, D., and Sorooshian, A.: Cloud, Aerosol, and Radiative Properties Over the Western North Atlantic Ocean, Journal of Geophysical Research: Atmospheres, 126, e2020JD034113,, 2021.

Corral, A. F., Braun, R. A., Cairns, B., Gorooh, V. A., Liu, H., Ma, L., Mardi, A. H., Painemal, D., Stamnes, S., van Diedenhoven, B., Wang, H., Yang, Y., Zhang, B., and Sorooshian, A.: An Overview of Atmospheric Features Over the Western North Atlantic Ocean and North American East Coast – Part 1: Analysis of Aerosols, Gases, and Wet Deposition Chemistry, Journal of Geophysical Research: Atmospheres, 126, e2020JD032592,, 2021.

Dadashazar, H., Alipanah, M., Hilario, M. R. A., Crosbie, E., Kirschler, S., Liu, H., Moore, R. H., Peters, A. J., Scarino, A. J., Shook, M., Thornhill, K. L., Voigt, C., Wang, H., Winstead, E., Zhang, B., Ziemba, L., and Sorooshian, A.: Aerosol Responses to Precipitation Along North American Air Trajectories Arriving at Bermuda, Atmos. Chem. Phys., 21, 16121-16141,, 2021.

Dadashazar, H., Painemal, D., Alipanah, M., Brunke, M., Chellappan, S., Corral, A. F., Crosbie, E., Kirschler, S., Liu, H., Moore, R. H., Robinson, C., Scarino, A. J., Shook, M., Sinclair, K., Thornhill, K. L., Voigt, C., Wang, H., Winstead, E., Zeng, X., Ziemba, L., Zuidema, P., and Sorooshian, A.: Cloud drop number concentrations over the western North Atlantic Ocean: seasonal cycle, aerosol interrelationships, and other influential factors, Atmos. Chem. Phys., 21, 10499-10526, 10.5194/acp-21-10499-2021, 2021.

Edwards, E.-L., Corral, A. F., Dadashazar, H., Barkley, A. E., Gaston, C. J., Zuidema, P., and Sorooshian, A.: Impact of various air mass types on cloud condensation nuclei concentrations along coastal southeast Florida, Atmospheric Environment, 254, 118371,, 2021.

Hilario, M., Crosbie, E., Bañaga, P., Betito, G., Braun, R., Cambaliza, M., Corral, A., Cruz, M., Dibb, J., Lorenzo, G., MacDonald, A., Robinson, C., Shook, M., Simpas, J., Stahl, C., Winstead, E., Ziemba, L., Sorooshian, A., Particulate Oxalate-to-Sulfate Ratio as an Aqueous Processing Marker: Similarity Across Field Campaigns and Limitations, Geophysical Research Letters, doi: 10.1029/2021GL096520, 2021.

Li, X, Wang, H., Chen, J., Endo, S., George, G., Cairns, B., Chellappan, S., Zeng, X., Kirschlerg, S., Voigt, C., Sorooshian, A., Crosbie, E., Chen, G., Ferrare, R. A., Gustafson, W. I., Hair, J. W., Kleb, M. M., Liu, H., Moore, R., Painemal, D., Robinson, C., Scarino, A. J., Shook, M., Shingler, T. J., Thornhill, K. L., Tornow, F., Xiao, H., Ziemba, L. D., and Zuidema, P., Large-eddy simulations of marine boundary-layer clouds associated with cold air outbreaks during the ACTIVATE campaign- part 1: Case setup and sensitivities to large-scale forcings, J of the Atmos. Sci.,, 2021.

Ma, L., Dadashazar, H., Hilario, M. R. A., Cambaliza, M. O., Lorenzo, G. R., Simpas, J. B., Nguyen, P., and Sorooshian, A.: Contrasting wet deposition composition between three diverse islands and coastal North American sites, Atmospheric Environment, 244, 117919,, 2021.

Mardi, A., Dadashazar, H., Painemal, D., Shingler, T., Seaman, S., Fenn, M., Hostetler, C., Sorooshian, A., Biomass Burning Over the United States East Coast and Western North Atlantic Ocean: Implications for Clouds and Air Quality, Journal of Geophysical Research – Atmospheres, 126, e2021JD034916,, 2021.

Ouyed, A., Zeng, X., Wu, L., Posselt, D. and Su, H., Two Stage Artificial Intelligence Algorithm for Calculating Moisture-Tracking Atmospheric Motion Vectors, Journal of Applied Meteorology and Climatology,, 2021.

Painemal, D., Corral, A. F., Sorooshian, A., Brunke, M. A., Chellappan, S., Afzali Gorooh, V., Ham, S.-H., O’Neill, L., Smith Jr., W. L., Tselioudis, G., Wang, H., Zeng, X., and Zuidema, P.: An Overview of Atmospheric Features Over the Western North Atlantic Ocean and North American East Coast—Part 2: Circulation, Boundary Layer, and Clouds, Journal of Geophysical Research: Atmospheres, 126, e2020JD033423,, 2021.

Seethala, C., P. Zuidema, J. Edson, M. Brunke, G. Chen, X.-Y Li, D. Painemal, C. Robinson, T. Shingler, M. Shook, A. Sorooshian, L. Thornhill, F. Tornow, H. Wang, X. Zeng, L. Ziemba, 2021: On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream. Geophys. Res. Lett., 48, doi:10.1029/2021GL094364, 2021.

Tornow, F., Ackerman, A. S., and Fridland, A. M.: Preconditioning of overcast-to-broken cloud transitions by riming in marine cold air outbreaks, Atmos. Chem. Phys., 21, 12049-12067, 10.5194/acp-21-12049-2021, 2021.