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This work introduces CAECENET, a new system capable of automatically retrieving columnar and vertically-resolved aerosol properties running the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm using sun-sky photometer (aerosol optical depth, AOD; and sky radiance measurements) and ceilometer (range corrected signal; RCS) data as input. This method, so called GRASPpac, is implemented in CAECENET, which assimilates sun-sky photometers data from CÆLIS database and ceilometer data from ICENET database (Iberian Ceilometer Network). CAECENET allows for continuous and near-real-time monitoring of both vertical and columnar aerosol properties. The main characteristics and workflow of CAECENET are explained in detail. This work also explores the potential of CAECENET to monitor and analyze the evolution of transported aerosol events on a regional scale by means of the distribution of CAECENET stations across the Iberian Peninsula. As an example, this paper analyzes, using the CAECENET products, the case of a Saharan dust outbreak that occurred between the 3rd and 5th of October 2022. This was an intense event, with AOD at 440 nm values around 0.5 in Madrid and Valladolid, and reaching 1.55 in Granada. Transport from the Canadian wildfires at the end of June 2023 is also studied. Despite the long-range transport of the smoke particles in this event, measured volume concentrations reached and surpassed 80 μ m3/ μ m2 in some stations. The results obtained point to the utility of this CAECENET tool for analyzing changes in the height and speed of the event propagation, in the aerosol concentration, and how this affects the optical properties. [ABSTRACT FROM AUTHOR]

Carbonyl sulfide (OCS) is used to quantify the carbon capture potential of the biosphere because of its direct correlation with CO2 uptake during photosynthesis. However, to constrain the urban biosphere signal, it is necessary to evaluate potential anthropogenic sources. We conducted two sampling campaigns in the Metropolitan Area of Barcelona (AMB), Spain, during May (full COVID lockdown) and October 2020 to measure the spatial distribution and variability of OCS in four urban land uses as follows: built, urban forest, urban park, and peri‐urban agriculture. The OCS background levels determined at Tibidabo (442 m asl) were approximately 484 ± 20 ppt and 407 ± 8 ppt for May and October 2020, respectively, and agreed with other seasonal surveys conducted in Europe during that same period. Averaged emissions were in the range of +Δ12 ± 40 ppt for the city and were +Δ9.4 ± 40.9 ppt for urban +Δ22.1 ± 48 ppt for urban green +Δ20.7 ± 42.9 ppt for agricultural and −Δ4.8 ± 19.6 ppt for forest. The urban values ranged from neutral to above background, suggesting nearby anthropogenic and marine emissions such as +Δ150 ppt in Montjuic, which is downwind of Barcelona's harbor. During the crop‐growing season in May, the agricultural areas consistently showed values below the background (up to −Δ76 ppt in Gavà, uptake) at 7:00 UTC when the land breezes were dominant, while later in the morning, when the sea breeze are developed, the plant sink is masked by the transport of marine emissions. Urban forests located north of Tibidabo showed OCS values up to −Δ70 ppt, suggesting significant uptake by urban forests. We conclude that determining the urban biosphere signal using OCS as a tracer is more complex than expected because the marine and anthropogenic emissions from the port strongly impact the spatial‐temporal distribution of OCS. Plain Language Summary: Carbonyl sulfide (OCS) is a gas used to quantify the carbon capture potential of the biosphere. However, cities have potential anthropogenic OCS sources that can impede a clear constraint of the urban biosphere signal. We conducted two sampling campaigns in the Metropolitan Area of Barcelona (AMB), Spain, during May (full COVID lockdown) and October 2020 to measure the variability of OCS in four urban land uses: built, urban forest, urban park, and peri‐urban agriculture. The OCS background levels determined at Tibidabo (were approximately 484 ± 20 ppt and 407 ± 8 ppt for May and October 2020, respectively). The urban built sites were typically above background, suggesting nearby anthropogenic and marine emissions. During the crop‐growing season, the agricultural areas consistently showed values below the background suggesting plant OCS uptake when the land breezes were dominant, while later in the morning, when the sea breezes developed, the influence of marine emission resulted in values above the background. Urban forests showed significant OCS uptake. We conclude that determining the urban biosphere signal using OCS as a tracer is more complex than expected because the marine and anthropogenic emissions from the port strongly impact the spatial‐temporal distribution of OCS. Key Points: The urban built sites were typically above background, suggesting nearby anthropogenic and marine emissionsAgricultural areas consistently showed values below the background suggesting plant Carbonyl sulfide (OCS) uptake when the land breezes were dominantDetermining urban biosphere signal using OCS is complex because marine and anthropogenic emissions impact its spatial‐temporal distribution [ABSTRACT FROM AUTHOR]