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Abstract. Our understanding of how rapid Arctic warming and permafrost thaw affect global climate dynamics is restricted by limited spatio-temporal data coverage due to logistical challenges and the complex landscape of Arctic regions. It is therefore crucial to make best use of the available observations, including the integrated data analysis across disciplines and observational platforms. To alleviate the data compilation process for syntheses, cross-scale analyses, earth system models, and remote sensing applications, we introduce ARGO, a new meta-dataset comprised of greenhouse gas observations from various observational platforms across the Arctic and boreal biomes within the polar region of the northern hemisphere. ARGO provides a centralised repository for metadata on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) measurements linked with an interactive online tool (https://www.bgc-jena.mpg.de/argo/). This tool offers prompt metadata visualisation for the research community. Here, we present the structure and features of ARGO, underscoring its role as a valuable resource for advancing Arctic climate research and guiding synthesis efforts in the face of rapid environmental change in northern regions. The ARGO meta-dataset is openly available for download at Zenodo (https://doi.org/10.5281/zenodo.13870390) (Vogt et al., 2024). 

Abstract Wind and turbulence effects on raindrop fall speeds were elucidated using field observations over a 2-yr time period. Motivations for this study include the recent observations of raindrop fall speed deviations from the terminal fall speed predictions ( V t ) based upon laboratory studies and the utilizations of these predictions in various important meteorological and hydrological applications. Fall speed ( V f ) and other characteristics of raindrops were observed using a high-speed optical disdrometer (HOD), and various rainfall and wind characteristics were observed using a 3D ultrasonic anemometer, a laser-type disdrometer, and rain gauges. A total of 26 951 raindrops were observed during 17 different rainfall events, and of these observed raindrops, 18.5% had a subterminal fall speed (i.e., 0.85 V t ≥ V f ) and 9.5% had a superterminal fall speed (i.e., 1.15 V t ≤ V f ). Our observations showed that distributions of sub- and superterminal raindrops in the raindrop size spectrum are distinct, and different physical processes are responsible for the occurrence of each. Vertical wind speed, wind shear, and turbulence were identified as the important factors, the latter two being the dominant ones, for the observed fall speed deviations. Turbulence and wind shear had competing effects on raindrop fall. Raindrops of different sizes showed different responses to turbulence, indicating multiscale interactions between raindrop fall and turbulence. With increasing turbulence levels, while the raindrops in the smaller end of the size spectrum showed fall speed enhancements, those in the larger end of the size spectrum showed fall speed reductions. The effect of wind shear was to enhance the raindrop fall speed toward a superterminal fall. 

Abstract Rainfall microphysical characteristics including raindrop fall speed, axis ratio, and canting angle were measured through field observations by using a high-speed optical disdrometer (HOD) during and after tornadic severe storm passage. High and low wind and turbulence characteristics were observed during and after passage, respectively, which provided an opportunity to compare the effects of the different wind and turbulence characteristics on raindrop characteristics. During passage, 9.4% of the raindrops larger than 1.0 mm in volume equivalent diameter ( D ) were identified as subterminal, whereas only 0.5% of the raindrops of the same size were detected as subterminal after passage. Contrary to findings in literature, we could not find any distinct superterminal fall speed behavior for raindrops with D < 1.0 mm during or after passage. For raindrops with D > 2.0 mm, deviations of the axis ratio distribution from the predicted distribution for the equilibrium raindrops were observed, and the deviations during passage were larger than those after passage. The deviations of the axis ratio distributions from the predicted distributions for the equilibrium raindrops were also observed for midsized (1.0 < D < 2.0 mm) raindrops; however, these deviations during and after passage were of similar magnitude. The canting angle distribution for raindrops with D > 2.0 mm was found to have the mean value of approximately 0° both during and after passage and the standard deviation values of 24.7° during passage and 13.6° after passage. This study shows the clear influence of wind on various rainfall microphysical characteristics and documents the observed value ranges of these characteristics under strong wind that are of importance for a number of rainfall applications, including radar rainfall retrievals and rainfall modeling.