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Organic carbon (OC) is a highly diverse class of compounds that represents a small but critical fraction of the atmosphere’s chemical composition. Volatile organic compounds (VOCs), when combined with nitrogen oxides (NOx), can produce tropospheric ozone (O3), a regulated air pollutant. OC also represents a large and growing fraction of aerosol mass, either through direct emissions from sources like fossil combustion and biomass burning, or through secondary chemistry by the oxidation and subsequent reduction of vapor pressure of VOCs leading to condensational growth. Clouds droplets and precipitation can contain additional OC due to the dissolution of soluble organic gases to the aqueous phase. OC has abundantly been found in aqueous samples of clouds, fog, and precipitation, exposing these compounds to unique aqueous chemical reactions and wet deposition. However, the concentrations and controlling factors of atmospheric aqueous organic carbon remain highly unconstrained. Cloud water measurements at Whiteface Mountain in the Adirondack Mountains in upstate New York have revealed an increasing trend of Total Organic Carbon (TOC), with annual median concentrations doubling in 14 years, possibly signaling a growing trend in atmospheric OC. However, the causes and potential consequences of this trend remain unclear. Another question that has yet to be explored is if this trend in OC extends beyond WFM. To answer this question, this work explores the trends of WFM cloud water and 4 additional long-term cloud water and wet deposition datasets that have measured TOC or dissolved OC (DOC) throughout the Northeast US. These sites include Mt Washington, NH, Hubbard Brook NH, Thompson Farm NH, and Sleepers River Vermont. This work will also discuss potential hypotheses driving this increasing trend including increased biomass burning influence and increased biogenic emissions in the region. 

Abstract Meteoroids of sub‐milligram sizes burn up high in the Earth's atmosphere and cause streaks of plasma trails detectable by meteor radars. The altitude at which these trails, or meteors, form depends on a number of factors including atmospheric density and the astronomical source populations from which these meteoroids originate. A previous study has shown that the altitude of these meteors is affected by long‐term linear trends and the 11‐year solar cycle related to changes in our atmosphere. In this work, we examine how shorter diurnal and seasonal variations in the altitude distribution of meteors are dependent on the geographical location at which the measurements are performed. We use meteoroid altitude data from 18 independent meteor radar stations at a broad range of latitudes and investigate whether there are local time (LT) and seasonal variations in the altitude of the peak meteor height, defined as the majority detection altitude of all meteors within a certain period, which differ from those expected purely from the variation in the visibility of their astronomical source. We find a consistent LT and seasonal response for the Northern Hemisphere locations regardless of latitude. However, the Southern Hemisphere locations exhibit much greater LT and seasonal variation. In particular, we find a complex response in the four stations located within the Southern Andes region, which indicates that the strong dynamical atmospheric activity, such as the gravity waves prevalent here, disrupts, and masks the seasonality and dependence on the astronomical sources. 

Scientific argumentation and modeling are both core practices in learning and doing science. However, they are challenging for students. Although there is considerable literature about scientific argumentation or modeling practice in K-12 science, there are limited studies on how engaging students in modeling and scientific argumentation might be mutually supportive. This study aims to explore how 5th graders can be supported by our designed mediators as they engage in argumentation and modeling, in particular, model revision. We implemented a virtual afterschool science club to examine how our modeling tool – MEME (Model and Evidence Mapping Environment), provided evidence, peer comments, and other mediators influenced students in learning about aquatic ecosystems through developing a model. While both groups that we examined constructed strong arguments and developed good models, we show how the mediators played different roles in helping them be successful. 

Gaia16aye was a binary microlensing event discovered in the direction towards the northern Galactic disc and was one of the first microlensing events detected and alerted to by the Gaia space mission. Its light curve exhibited five distinct brightening episodes, reaching up to I  = 12 mag, and it was covered in great detail with almost 25 000 data points gathered by a network of telescopes. We present the photometric and spectroscopic follow-up covering 500 days of the event evolution. We employed a full Keplerian binary orbit microlensing model combined with the motion of Earth and Gaia around the Sun to reproduce the complex light curve. The photometric data allowed us to solve the microlensing event entirely and to derive the complete and unique set of orbital parameters of the binary lensing system. We also report on the detection of the first-ever microlensing space-parallax between the Earth and Gaia located at L2. The properties of the binary system were derived from microlensing parameters, and we found that the system is composed of two main-sequence stars with masses 0.57 ± 0.05 M ⊙ and 0.36 ± 0.03 M ⊙ at 780 pc, with an orbital period of 2.88 years and an eccentricity of 0.30. We also predict the astrometric microlensing signal for this binary lens as it will be seen by Gaia as well as the radial velocity curve for the binary system. Events such as Gaia16aye indicate the potential for the microlensing method of probing the mass function of dark objects, including black holes, in directions other than that of the Galactic bulge. This case also emphasises the importance of long-term time-domain coordinated observations that can be made with a network of heterogeneous telescopes.