Supplementary material to "The Arctic Radiation-Cloud-Aerosol-Surface Interaction Experiment (ARCSIX) airborne campaign dataset"

Patrick C. Taylor, Armin Sorooshian, Rei Ueyama, K. Sebastian Schmidt, Ihab Abboud, Quincy Allison, Kevin R. Barry, Sebastian Becker, Holly A. Bender, Joseph R. Bennett, James B. Blair, Niklas Bohn, Linette Boisvert, Matthew D. Brown, Roelof Bruintjes, Anthony Bucholtz, Megan Buzanowicz, Brian Cairns, Filippo Calì Quaglia, Eduard Chemyakin, Bo Chen, Gao Chen, Hong Chen, Yu‐Wen Chen, Zezhen Cheng, Swarup China, Dan Chirica, Yonghoon Choi, Peter R. Colarco, Brian Collister, Ewan Crosbie, Maurice J. Cross, Janet Daniels, Paul J. DeMott, Joshua P. DiGangi, Alcide Giorgio di Sarra, Glenn S. Diskin, Erica K. Dolinar, Eva-Lou Edwards, Samuel Ephraim, Nikolaos Evangeliou, Romanos Foskinis, Francesca Gallo, Lan Gao, José Luís Gómez-Amo, Daisy Gonzalez, Christine Groot Zwaaftink, Pawan Gupta, Ivan Heckman, Michael Hendrickson, Miguel Ricardo A. Hilario, Ken Hirata, Michelle Hofton, Andrew L. Holen, Ulaş İm, Alia L. Khan, Ralph A. Kahn, Alexei Korolev, Sonia M. Kreidenweis, Thomas Krumpen, Nathan Kurtz, Leslie R. Lait, Bradley Lamkin, Jack Landy, Nurun Nahar Lata, R. Paul Lawson, Samuel LeBlanc, Sean Leavor, Jing Li, Thorsten Markus, Hal Maring, Andreas Massling, Camille Mavis, Flynn McGinnity, Kerry Meyer, Gabriel Mojica, Richard H. Moore, Parker Morris, Giovanni Muscari, Vikas Nataraja, Amin R. Nehrir, Athanasios Nenes, E. P. Nowottnick, Matteo Ottaviani, Chelsea Parker, Ryan Patnaude, Michael Perez, Russell Perkins, Colten Peterson, Alek Petty, Stevie Phothisane, Chris Polashenski, Kerri A. Pratt, Kayla M. Preisler (23809917), John Prytherch, David Rabine, Jens Redemann, Ju‐Mee Ryoo, Joseph S. Schlosser, Vanessa Selimovic

The spring deployment began with a focus on capturing the initial sea ice conditions.On 28 May, the passage of an Arctic cyclone across the Lincoln Sea on 27 May resulted in a thinning of the cloud layer, relatively low predicted AODs (< 0.1) from the NASA Goddard Earth Observing System forward processing (GEOS-FP, see Section 7d) model, and decreasing relative humidity at mid-levels (500-700 hPa) over the buoy region, which was covered with fresh snow.Strong northerly winds persisted over the Canadian Archipelago and contributed to the cold air advection toward Ellesmere Island and across the Lincoln Sea.The northerly wind combined with a developing cyclone over northern Baffin Bay, and together with a strong northeasterly flow at the surface through the Nares Strait, effectively transported the surface air mass from the Lincoln Sea into Baffin Bay.These factors produced cloud-free conditions over the Lincoln Sea, supporting the SIMB survey flight (RF1, P-3B only, Table S1).After a high-altitude transit from Pituffik, the SIMB survey consisted of a mix of high-altitude and low-altitude legs and a square spiral over Buoy O on 28 May.The aircraft returned at low altitude (< 250m) via the Nares Strait, where high winds at flight level (15 to 25 m s -1 ), blowing snow over sea ice, and sea spray over the polynya, were observed, as well as a gradient in aerosol size distribution and hygroscopicity.On this and many subsequent flights, the aircraft also passed near the long-term ground aerosol sampling station at Alert, Canada (82.50°N, 62.35°W) (Sturges and Barrie, 1989; Sharma et al., 2019), as it transited between Pituffik and the Lincoln Sea, enabling comparisons of ARCSIX data to the long-term aerosol record.In the spring, at least one of the ARCSIX aircraft transited near Alert on all flight days.A weak Arctic cyclone was centered over the buoy region in the Lincoln Sea on 30 May.Behind the westward moving cyclone was an area of single-layered, low-level clouds (i.e., no mid or high clouds) that was sampled using two cloud walls (RF2).This cloud system developed in part due to the northward transport of dry continental air across the northern Greenland coast into the Lincoln Sea at mid-levels that merged with the strong northward advection of a warm air mass through the Fram Strait.GEOS-FP and the FLEXPART (FLEXible PARTicle) Lagrangian particle dispersion model (see Section 7e) predicted aged, elevated smoke over the buoys, that FLEXPART footprint emission sensitivities suggest originated from fires in boreal North America.The NASA High-Altitude Lidar Observatory (HALO; Section 4b) also indicated elevated smoke, some of which was in contact with the sampled clouds.Nearsurface easterlies (westerlies) were found on the northern (southern) end of the two cloud walls.The P-3B aircraft also overflew the Thule High Arctic Atmospheric Observatory (THAAO) station (see Section 6b) during this flight.31 May marked the first occurrence of severe clear-sky conditions in the domain, prompting a BRDF module focused on Buoy Q, north of Ellesmere Island (RF3).The weak Arctic cyclone over the Lincoln Sea moved westward and was replaced by a developing high-pressure system providing relatively quiescent conditions.Cloud-free skies and light, variable surface winds were observed north of Ellesmere Island.Although the strong warm air advection through the Fram Strait no longer extended to the North Pole, forward trajectories of Fram Strait parcels suggested that the low-level air mass sampled near Buoy Q may have originated from the Fram Strait approximately two days prior.The GEOS-FP and FLEXPART models did not predict appreciable dust, anthropogenic, or biomass burning aerosols near the surface in this region.Week 2 (June 3-June 7, 2024) Week two of the spring deployment focused on cloud lifecycle and aerosol objectives.Four flights were flown with three cloud-focused flights that included multi-day quasi-Lagrangian sampling and one BRDF flight.The week began with a broad high-pressure system developing over Greenland, extending northward, and generating light