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The Ny-Alesund Aerosol Cloud Experiment (NASCENT): Overview and First Results

Wed, 08 Jun 2022 00:00:00 GMT

Title: The Ny-Alesund Aerosol Cloud Experiment (NASCENT): Overview and First Results Authors: Pasquier, J. T.; David, R. O.; Freitas, G.; Gierens, R.; Gramlich, Y.; Haslett, S.; Li, G.; Schafer, B.; Siegel, K.; Wieder, J.; Adachi, K.; Belosi, F.; Carlsen, T.; Decesari, S.; Ebell, K.; Gilardoni, S.; Gysel-Beer, M.; Henneberger, J.; Inoue, J.; Kanji, Z. A.; Koike, M.; Kondo, Y.; Krejci, R.; Lohmann, U.; Maturilli, M.; Mazzolla, M.; Modini, R.; Mohr, C.; Motos, G.; Nenes, A.; Nicosia, A.; Ohata, S.; Paglione, M.; Park, Sang-Jong; Pileci, R. E.; Ramelli, F.; Rinaldi, M.; Ritter, C.; Sato, K.; Storelvmo, T.; Tobo, Y.; Traversi, R.; Viola, A.; Zieger, P. Abstract: The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Alesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Alesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

Ubiquity of human-induced changes in climate variability

Thu, 09 Dec 2021 00:00:00 GMT

Title: Ubiquity of human-induced changes in climate variability Authors: Rodgers, Keith B.; Lee, Sun-Seon; Rosenbloom, Nan; Timmermann, Axel; Danabasoglu, Gokhan; Deser, Clara; Edwards, Jim; Kim, Ji-Eun; Simpson, Isla R.; Stein, Karl; Stuecker, Malte F.; Yamaguchi, Ryohei; Bodai, Tamas; Chung, Eui-Seok; Huang, Lei; Kim, Who M.; Lamarque, Jean-Francois; Lombardozzi, Danica L.; Wieder, William R.; Yeager, Stephen G. Abstract: While climate change mitigation targets necessarily concern maximum mean state changes, understanding impacts and developing adaptation strategies will be largely contingent on how climate variability responds to increasing anthropogenic perturbations. Thus far Earth system modeling efforts have primarily focused on projected mean state changes and the sensitivity of specific modes of climate variability, such as the El Nino-Southern Oscillation. However, our knowledge of forced changes in the overall spectrum of climate variability and higher order statistics is relatively limited. Here we present a new 100-member Large Ensemble of climate change projections conducted with the Community Earth System Model version 2 over 1850-2100 to examine the sensitivity of internal climate fluctuations to greenhouse warming. Our unprecedented simulations reveal that changes in variability, considered broadly in terms of probability, distribution, amplitude, frequency, phasing, and patterns, are ubiquitous and span a wide range of physical and ecosystem variables across many spatial and temporal scales. Greenhouse warming in the model in alters variance spectra of Earth system variables that are characterized by non-Gaussian probability distributions, such as rainfall, primary production, or fire occurrence. Our modeling results have important implications for climate adaptation efforts, resource management, seasonal predictions, and for assessing potentialstressors for terrestrial and marine ecosystems.

Impact of North Atlantic-East Asian teleconnections on extremely high January PM10 cases in Korea

Wed, 01 Dec 2021 00:00:00 GMT

Title: Impact of North Atlantic-East Asian teleconnections on extremely high January PM10 cases in Korea Authors: Kim, Jeong-Hun; Kim, Seong-Joong; Youn, Daeok; Kim, Maeng-Ki; Kim, Joo-Hong; Kim, Joowan; Noh, El Abstract: In this study, we investigated the daily variability of PM10 concentrations in January in Korea during the past 19 years (2001-2019), as well as the associated atmospheric circulation patterns. The daily PM10 concentrations were classified into three cases: low (L; < 50 mu g/m(3)), high (H; 50-100 mu g/m(3)), and extremely high (EH; >= 100 mu g/m(3)). We found that the strength of the East Asian winter monsoon influenced the PM10 variability in the L and H cases. However, the EH cases were strongly influenced by the rapid growth of barotropic warming (anticyclonic anomaly) over the eastern North Atlantic and Northern Europe (ENE), and the stationary Rossby waves grew rapidly over Eurasia within only four days. Analysis of the quasi-geostrophic geopotential tendency budget revealed that the anticyclonic anomaly over the ENE was enhanced by vorticity advection. Linear baroclinic model experiments confirmed that vorticity forcing over the ENE induces favorable atmospheric conditions for the occurrence of EH PM10 events in East Asia. As a result, the PM10 concentration sharply increased sharply by approximately three times over four days. This study suggests that understanding atmospheric teleconnections between the ENE and East Asia can effectively predict the occurrence of EH PM10 events in Korea, helping to reduce the human health risks from atmospheric pollution.

Role of polar vortex weakening in cold events in central Asia during late winter

Wed, 01 Dec 2021 00:00:00 GMT

Title: Role of polar vortex weakening in cold events in central Asia during late winter Authors: Kim, Seong-Joong; Choi, Hye-Sun Abstract: The cause of cold events over central Asia was investigated. Since 1958, surface air temperature (SAT) has gradually increased over central Asia, but SAT has shown very strong multidecadal fluctuations, with cooling dominant in the 1960s-1970s and recent decades but warming dominant in the 1990s. SAT in February in central Asia has decreased by more than 7 degrees C compared to that in normal years. Analysis indicates that cold events over central Asia are related to the weakening of the polar vortex, which is indicated by the increase in polar cap height (PCH) and weaker zonal-mean zonal winds. The increase in PCH begins in January in the stratosphere and propagates down to the troposphere in February; it is well reflected in the weakening of zonal-mean zonal winds in the stratosphere in January, which extends to the troposphere in February. The January increase in PCH anomaly is associated with surface conditions in the Arctic region, especially the Barents-Kara seas, where sea level pressure increases substantially in January; high pressure then expands to the southeastern (downstream) branch of the Siberian high in February, bringing cold eastern Siberian air to central Asia.