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Principal Investigator (PI): Armin Sorooshian, U. of Arizona (UA)
Deputy PI: Xubin Zeng, UA
Project Scientist: Johnathan Hair, NASA LaRC
Partnering Institutions: UA, NASA LaRC, NASA GISS, SSAI, NIA, PNNL, U of Miami, NOAA ESRL

Mission Overview and Platforms: ACTIVATE will deploy two complementary aircraft over the western North Atlantic Ocean – the NASA LaRC HU-25 Falcon and B-200 King Air. The HU-25 acquires in situ measurements below, in, and above clouds. The B-200 flies above clouds to remotely measure aerosols and clouds using the High Spectral Resolution Lidar-2 (HSRL‑2), the Research Scanning Polarimeter (RSP), and deploys dropsondes to measure the atmospheric state. Since both aircraft and the majority of in situ and remote sensing instruments are based at LaRC adjacent to the western Atlantic study region, ACTIVATE will acquire a statistically robust dataset through an extensive series of flights (~50 joint airplane missions per year) in each of three years (~600 hours and ~150 flights over three years for each airplane). We will sample a wide range of aerosol and cloud conditions by planning February–June flights.

Mission Schedule

How will it work?

  1. Location
    1. The western North Atlantic Ocean is selected for ACTIVATE for three reasons:
      1. it includes a wide range of MBL cloud types, from stratiform to cumulus clouds;
      2. it is affected by pollution transport;
      3. its close proximity to LaRC increases both flight time and flight plan flexibility.
  2. Aircraft Coordination
    1. The ACTIVATE suite of instruments is divided between two aircraft; the low-flying HU-25 (with a minimum altitude of 0.15 km) and the higher-flying B-200.
      1. Based on consultation with LaRC pilots, these two aircraft will be flown at altitudes that are ideally matched in terms of ground speeds and flight endurance to provide close spatially and temporally coordinated flights.
  3. Schedule
    1. Briefly, the schedule includes two campaigns (February–March and May–June) in each of three years during 2020–2022 (total of six), thereby sampling part of the annual cycle (late winter to early summer) in cloud and aerosol properties.
      1. We plan for 150 joint flights with two coordinated aircraft, which is the  maximum that can be conducted under the budgetary and logistical constraints. These flights would provide an order of magnitude more ‘cloud events’ than previous airborne projects (see §3.1) and hence will offer unprecedented statistics to build robust aerosol-cloud interactive model parameterizations. This can best be achieved between February-March and May-June over three years by executing 100 flight hours during 25 flights for each aircraft in each of the six campaigns (for a combined aircraft total of 1200 hours and 300 flights over the project lifetime). After each upload, 1–2 test flights (2 hrs) are planned for each platform consistent with previous projects. Each campaign year consists of a single instrument upload and download period. Given that multiple flights can be conducted on the same day, the 25 joint flights for each campaign over a two month duration results in a reasonable pace of operations to target specific cloud scenes. A month long hiatus, also used for schedule reserve, between the two campaigns allows for an early period of preliminary data analysis and instrument and aircraft maintenance. By leveraging recent, similar implementation approaches with proven instruments and experienced teams, ACTIVATE is well-positioned to execute a comprehensive, yet low-risk, series of campaigns.
The ACTIVATE strategy efficiently captures the data needed for ‘cloud events’. The B-200 and HU-25 flight altitudes are overlaid on an image showing aerosol and cloud backscatter measured by HSRL-2 over the southwest Atlantic Ocean on 23 May 2007. The B-200 has a constant nominal flight altitude of 9 km while the HU-25 conducts boundary layer and cloud sampling between 0.15–3 km. Coordination of both aircraft are within about 1–2 km (between aircraft tracks) and 10 min.

July 1, 2021

We finished our summer campaign this past week with four more ACTIVATE flights (Research Flights 90-93) between June 28 and 30. These flights focused on extensive data collection in typical summertime shallow cumulus clouds. A notable feature in these flights was sampling behind ship vessels near the coast that yielded especially large enhancements in particle concentration parameters.

June 28, 2021

Four flights were conducted last week, with two single flight days on June 22 and 24, and a double flight day on June 26. Saturday’s conditions (June 26) were in particular very good for ACTIVATE with a scattered shallow cumulus cloud scene throughout the day that both planes were able to jointly characterize. The past week also was linked to high variability in aerosol conditions with the northward advancement of African dust into our study region.

June 21, 2021

This past week included three single-flight days on Tuesday-Thursday (June 15-17). The first flight of this week (June 15) was a statistical cloud survey but proved to be a challenging flight to execute as the King Air encountered pervasive cirrus along the track and the Falcon dealt with low clouds at varying altitude ranges. The June 16 flight targeted mostly clear skies with observations of moderate aerosol loading. This flight also included an overflight of Langley Research Center at the end to intercompare with the AERONET site and the High Altitude Lidar Observatory (HALO) HSRL/water vapor lidar that was conducting upward looking ground tests. The last flight of the week (June 17) included a coordinated run along the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite overpass and then two reverse headings to capture in cloud data in vicinity of the ASTER overpass for additional contextual data. The flights on June 16-17 both saw non-spherical particles near the coast and drizzle over the ocean was observed on June 17.

June 14, 2021

This past week included two double-flight days on Monday-Tuesday (June 7-8). June 7 was notable in that the second flight (RF 80) was a “process study” flight, which accounts for approximately 10% of ACTIVATE flights. We targeted an area with a cluster of clouds and conducted a total of 10 Falcon legs in cloud at different altitudes ranging from ~2 to ~13 kft. These legs and a subsequent downward spiral resulted in 10 cloud water samples for a single cloud system. Simultaneously, the King Air conducted a ‘wheel and spoke” pattern far above to allow the remote sensors to characterize the environment and cloud that the Falcon was directly sampling. A total of 14 dropsondes were launched by the King Air in the ~3 hr flight. This flight and the other “process study” flight in this summer campaign (RF77 on June 2) will provide a remarkable dataset to investigate aerosol-cloud-meteorology interactions with very detailed measurements for single evolving cloud systems.

June 7, 2021

Four successful joint flights occurred last week. The double flight day on Wednesday June 2 was particularly noteworthy. Our morning flight conducted our typical statistical survey flight plan to an area south of the Virginia coast where there was a cumulus cloud field, with some regions evolving into deeper, more organized, convection. Based on that flight and satellite imagery, we set up the second flight to execute a “process study” pattern where the Falcon conducted a series of transects through a selected cloud cluster to characterize the vertical microphysical properties of the developing cluster immediately followed by an environmental profile in the surrounding cloud-free region. Simultaneously, the King Air conducted a “wheel and spoke” pattern centered around the cloud system, with multiple dropsondes launched above, and on the periphery of the cloud cluster alongside remote sensing transects to characterize the cloud and aerosol system underneath. Data from both planes will be used to characterize the range of cloud types observed on that day, with a focus on understanding the processes that drive shallow cumulus organization.

June 1, 2021

The last two weeks were busy with 9 joint flights, including three separate double-sortie days. The May 21 morning flight in particular was intriguing with a mixture of different conditions offshore with the two aircraft flying mostly straight to the east and then returning on the same track to NASA LaRC. Closer to shore, the aircraft observed a stratus deck with a prominent aerosol layer just above cloud as observed by the HSRL-2. These clouds then transitioned progressively into a more scattered cumulus cloud field to the east. At the far eastern end of the track there was a cold pool that we sampled within and just outside. Throughout this and the other flights this past week, there was evidence both either (or both) smoke and dust in the free troposphere. Measurement data will help unravel how these various aerosol types interact with the different types of clouds such as in the May 21 flights. On May 19, we also coordinated the flight along the CALIPSO satellite track where both aircraft and the satellite had successful made measurements.

May 17, 2021

After a short break after the Winter 2021 campaign, ACTIVATE took back to the skies this past week to start the Summer 2021 campaign. We conducted 4 successful joint flights between May 13-15 with interesting cloud conditions in each flight. The lower-flying Falcon characterized multiple layers of clouds and observed both warm and mixed-phase precipitation. Remote sensing observations on the higher-flying King Air detected aerosol layers aloft in the free troposphere potentially from dust and smoke on separate flights.

April 5, 2021

ACTIVATE wrapped up its winter 2021 flight campaign with five joint research flights this past week (RF 57-61) capped off by a double-flight day on Friday (4/2) to capitalize on another cold air outbreak event. Those two flights included an increased number of dropsondes (~10 per flight) to get extensive temporal and spatial characterization of the vertical atmospheric structure as the cold air outbreak cloud field evolved during the day. Notable in the other flights last week was successful coordination with ASTER and CALIPSO overpasses in our flight region.

March 29, 2021

We executed a joint flight (RF 56) on Tuesday March 23rd on a day marked by fairly ‘clean’ conditions in terms of very low aerosol and cloud drop number concentrations in the marine boundary layer. Cloud fraction on this day was markedly lower than a typical cold air outbreak type of day, which is helpful for ACTIVATE which is aiming to generate statistics in a wide range of conditions associated with aerosols, clouds, and meteorology.

March 22, 2021

The previous week posed significant weather challenges but Saturday (March 20, 2020) did finally provide low clouds evolving in a cold air outbreak. Interesting features in that joint flight (Research Flight 55) were Asian dust residing aloft above the boundary layer clouds, in addition to an interesting layer of depolarizing aerosol right above clouds near the end of flight as observed by the HSRL-2; it is unclear what the source of that layer was, but data analysis with the Falcon data will help unravel those details.

March 15, 2021

ACTIVATE conducted four more successful joint flights (Research Flights 51-54) this past week. We characterized a variety of cloud conditions including post-frontal clouds associated with another cold air outbreak on Monday (March 8) in contrast to the following day (Tuesday March 9) where there was a sharp inversion with uniform cloud top heights and generally thin clouds. Flights this past week were marked by influence from local and regional burning emissions. The second of two flights on Friday (March 12) was coordinated with a CALIPSO overpass.

March 8, 2021

ACTIVATE executed three successful joint flights (Research Flights 48-50) this past week. On Thursday March 4th we coordinated our flight with a NASA A-Train overpass over an area with some scattered marine boundary layer clouds. The back-to-back flights on Friday March 5th served two objectives to capitalize on an excellent cold air outbreak event: (i) characterize the aerosol and meteorological characteristics upwind of the cloud field farther downwind; and (ii) characterize the evolution of the cloud field with the desire to capture the transition from overcast cloudy conditions to open cell structure. Noteworthy features in these flights were dust layers from long-range transport and significant new particle formation.

Febraury 5, 2021

ACTIVATE’s had its first joint flight of the winter 2021 campaign on February 3. We were successful to sample a transition from overcast stratocumulus clouds to broken cumulus clouds near our farthest southeast point of the flight track. There was extensive mixed-phase precipitation in areas closer to shore but pure liquid clouds farther offshore coinciding with the open cell cloud field. Although at low optical depth, an interesting aerosol layer was observed above 6 km that most likely was dust due to its depolarizing nature.

January 30, 2020

This past week ACTIVATE took to the skies again to begin our 2021 winter campaign. In contrast to last year, we started a bit earlier in the month of January to capitalize on a higher frequency of cold air outbreak events. Friday’s flights (January 29) were particularly ideal with both aircraft sampling along cloud streets aligned with the predominant wind direction coming from the north/northwest. We observed a transition from supercooled droplets to mixed phase precipitation with distance away from shore.