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J. Brant Dodson, Marilé Colón Robles, Jessica E. Taylor, Cayley C. DeFontes, and Kristen L. Weaver


On 21 August 2017, North America witnessed a total solar eclipse, with the path of totality passing across the United States from coast to coast. The major public interest in the event inspired the Global Learning and Observations to Benefit the Environment (GLOBE) Observer to organize a citizen science observing campaign to record the meteorological effects of the eclipse. Participants at 17 585 observing sites collected 68 620 temperature observations and 15 978 cloud observations. With 7194 sites positioned in the path of totality, participants provide a nearly unbroken record of the cloud and temperature effects of the eclipse across the contiguous United States. The collection of both temperature and cloud observations provides an opportunity to quantify the cloud–temperature relationship. The unique character of citizen science, which provides data from a large number of observations with limited quality control, requires a method that leverages the large number of observations. By grouping observing sites along the path of totality by 1° longitude bins, the errors from individual sites are averaged out and the meteorological effects of the eclipse can be determined robustly. The data reveal a distinct relationship between prevailing cloud cover and the eclipse-induced temperature depression, in which overcast conditions reduces the temperature depression by about one-half of the value from clear conditions. A comparison of the GLOBE results with mesonet data allows a test of the robustness of the citizen science results. The results also show the great benefit that research using citizen science data receives from increased numbers of participants and observations.

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Robert M. Rauber, Guangyu Zhao, Larry Di Girolamo, and Marilé Colón-Robles


This paper examines the effect of trade wind cumulus clouds on aerosol properties in the near-cloud environment using data from the Rain in Cumulus over the Ocean (RICO) campaign. Aerosol size distributions, particle concentrations, and optical properties are examined as a function of altitude and distance from cloud, at ambient relative humidity (RH) and adjusted to a constant RH to isolate effects of humidification from other processes.

The cloud humidity halo extended about 1500–2000 m from the cloud edge, with no clear altitude dependence on horizontal extent over an altitude range of 600–1700 m. The combined effects of vertical transport of aerosol by clouds and cloud processing contributed to the modification of aerosol size distributions within the clouds' humidity halos, particularly close to the cloud boundaries. Backscatter at 532 nm, calculated from the aerosol properties, exhibited no distinguishable trend with altitude within 400 m of cloud edges, increased toward lower altitudes beyond 400 m, and decreased away from cloud boundaries at all altitudes. The mean aerosol diameter was found to rapidly decline from 0.8 to 0.4 μm from near the cloud boundary to the boundary of the humidity halo. Aerosol optical depth at 532 nm within the layer between 600 and 1700 m increased near exponentially from 0.02 to 0.2 toward the cloud boundaries within the humidity halo. These trends agreed qualitatively with past space-based lidar measurements of trade wind cloud margins, although quantitative differences were noted that likely arose from different sampling strategies and other factors.

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Jørgen B. Jensen, Stuart P. Beaton, Jeffrey L. Stith, Karl Schwenz, Marilé Colón-Robles, Robert M. Rauber, and John Gras


Size distributions of giant aerosol particles (dry radius larger than 0.5 μm, sometimes referred to as coarse-mode aerosol particles) are not well characterized in the atmosphere. Measurements are problematic for these particles because they (i) occur in low concentrations, (ii) have difficulty in passing through air inlets, (iii) may be dry or deliquesced particles, and (iv) if sampled by impaction, typically require labor-intensive methods. In this study, a simple, high-volume impaction system called the Giant Nucleus Impactor (GNI), based on free-stream exposure of polycarbonate slides from aircraft, is described along with an automated optical microscope–based system for analysis of the impacted particles. The impaction slides are analyzed in a humidity-controlled chamber (typically 90% relative humidity) that ensures deliquescence of soluble (typically sea salt) particles. A computer-controlled optical microscope with two digital cameras is used to acquire and analyze images of the aerosol particles. At relative humidities above deliquescence (74% RH for sea salt), such particles will form near-spherical cap solution drops on the polycarbonate slides. The sea-salt mass in each giant aerosol particle is then calculated using simple geometry and published water activity measurements. The system has a sample volume of about 10 L s−1 at aircraft speeds of 105 m s−1. For salt particles, the measurement range is from about 0.7 μm dry radius to at least 16 μm dry radius, with a size-bin resolution of 0.2 μm dry radius. The sizing accuracy was tested using polystyrene latex (PSL) beads of known size.

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Marilé Colón Robles, Helen M. Amos, J. Brant Dodson, Jeffrey Bouwman, Tina Rogerson, Annette Bombosch, Lauren Farmer, Autumn Burdick, Jessica Taylor, and Lin H. Chambers


Citizen science is often recognized for its potential to directly engage the public in science, and is uniquely positioned to support and extend participants’ learning in science. In March 2018, the Global Learning and Observations to Benefit the Environment (GLOBE) Program, NASA’s largest and longest-lasting citizen science program about Earth, organized a month-long event that asked people around the world to contribute daily cloud observations and photographs of the sky (15 March–15 April 2018). What was considered a simple engagement activity turned into an unprecedented worldwide event that garnered major public interest and media recognition, collecting over 55,000 observations from 99 different countries, in more than 15,000 locations, on every continent including Antarctica. The event was called the “Spring Cloud Challenge” and was created to 1) engage the general public in the scientific process and promote the use of the GLOBE Observer app, 2) collect ground-based visual observations of varying cloud types during boreal spring, and 3) increase the number and locations of ground-based visual cloud observations collocated with cloud-observing satellites. The event resulted in roughly 3 times more observations than during the historic and highly publicized 2017 North American total solar eclipse. The dataset also includes observations over the Drake Passage in Antarctica and reports from intense Saharan dust events. This article describes how the challenge was crafted, outreach to volunteer scientists around the world, details of the data collected, and impact of the data.

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Robert M. Rauber, Bjorn Stevens, Jennifer Davison, Sabine Goke, Olga L. Mayol-Bracero, David Rogers, Paquita Zuidema, Harry T. Ochs III, Charles Knight, Jorgen Jensen, Sarah Bereznicki, Simona Bordoni, Humberto Caro-Gautier, Marilé Colón-Robles, Maylissa Deliz, Shaunna Donaher, Virendra Ghate, Ela Grzeszczak, Colleen Henry, Anne Marie Hertel, Ieng Jo, Michael Kruk, Jason Lowenstein, Judith Malley, Brian Medeiros, Yarilis Méndez-Lopez, Subhashree Mishra, Flavia Morales-García, Louise A. Nuijens, Dennis O'Donnell, Diana L. Ortiz-Montalvo, Kristen Rasmussen, Erin Riepe, Sarah Scalia, Efthymios Serpetzoglou, Haiwei Shen, Michael Siedsma, Jennifer Small, Eric Snodgrass, Panu Trivej, and Jonathan Zawislak

The Rain in Cumulus over the Ocean (RICO) field campaign carried out a wide array of educational activities, including a major first in a field project—a complete mission, including research flights, planned and executed entirely by students. This article describes the educational opportunities provided to the 24 graduate and 9 undergraduate students who participated in RICO.

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