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Christopher Cantrell and Vincent Michoud

Abstract

ACROSS (Atmospheric ChemistRy Of the Suburban foreSt) is an integrative, innovative, multi-scale project within the “Make Our Planet Great Again” (MOPGA) initiative designed to advance understanding of the fate of urban and biogenic air mass mixtures in the Paris region. An ACROSS hypothesis is that the anthropogenic-biogenic air mass mixing leads to changes in the production of oxygenated volatile organic compounds (VOCs) whose properties alter their importance in incorporation into secondary organic aerosols (SOA) and their roles in the production of ozone and other relevant secondary species. A likely important factor is NOx transport to suburban biogenic environments and the resulting modification of key chemical processes.

A highlight of ACROSS is an intensive, multi-platform measurement campaign that will take place in the summer of 2022. The campaign will include a 40-meter tower and ground-based measurements in the Rambouillet suburban forest to the southwest of Paris, airborne regional observations across Paris and suburban forested areas, and several other multi-instrumented ground sites located in the urban, rural, and semi-rural Paris region. The data collected from this campaign will provide a unique snapshot of the properties and mixing of urban and biogenic air masses around one of the most populated and polluted European megacities. This new knowledge will advance our understanding at the process level and lead to the ability to represent such complex systems in numerical models, ultimately resulting in improved capability to predict the impacts on air quality, regional climate, and global climate change.

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Arianna Valmassoi, Jan D. Keller, Daryl T. Kleist, Stephen English, Bodo Ahrens, Ivan Bašták Ďurán, Elisabeth Bauernschubert, Michael G. Bosilovich, Masatomo Fujiwara, Hans Hersbach, Lili Lei, Ulrich Löhnert, Nabir Mamnun, Cory R. Martin, Andrew Moore, Deborah Niermann, Juan José Ruiz, and Leonhard Scheck
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Stefan Grab and Mark Williams

Abstract

We introduce the Dutch East India Company ‘day registers’ as one of the world’s longest known pre-19th Century corporate chronicles (1652-1791) containing near-continuous, systematic, non-instrumental daily weather information for Cape Town, southern Africa. This transcript provides the longest known continuous 17th/18th Century daily weather record for Africa and the southern hemisphere. An 18- year (1773-1791) climate chronology from this record is presented, thus providing unique insight to the late 18th Century climate of Cape Town. Extraction of daily weather information for basic statistical analysis includes precipitation, wind, sky conditions, and accounts of storms, drought and floods. From this, we provide monthly and annual number of rain days, a rain index (relative rainfall amount), hot and cold days, and occurrence of storm strength winds. Results show extreme weather and climate variability in Cape Town during the mid- to late 1780s.

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Juhyeong Han, Inyoung Jang, Daein Kang, Minju Baek, Hideki Kanamaru, and Kwang-Hyung Kim
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Callum Munday, Sebastian Engelstaedter, Gilbert Ouma, Geoffrey Ogutu, Daniel Olago, Dennis Ong’ech, Thomas Lees, Bonface Wanguba, Rose Nkatha, Clinton Ogalo, Roba Ali Gàlgalo, Abdi Jillo Dokata, Erick Kirui, Robert Hope, and Richard Washington

Abstract

The Turkana Low-level Jet (LLJ) is an intrinsic part of the African climate system. It is the principle conduit for water vapour transport to the African interior from the Indian Ocean, and droughts in East Africa tend to occur when the jet is strong. The only direct observations of the Turkana Jet come from manual tracking of pilot balloons in the 1980s. Now, modern reanalysis datasets disagree with one another over the strength of jet winds and underestimate the strength of the jet by 25-75% compared to the pilot balloon data. This article gives an overview of a month-long field campaign based in northwest Kenya - the Radiosonde Investigation For the Turkana Jet (RIFTJet) - which measured the Turkana Jet for the first time in forty years using modern technologies. Radiosonde data reveal a persistent low-level jet, which formed on every night of the campaign, with an average low-level maximum wind speed of 16.8 m.s-1 at 0300LT. One of the latest reanalysis datasets (ERA5) underestimates low-level wind speeds by an average of 24% (4.1 m.s-1) at 0300LT, and by 33% (3.6 m.s-1) at 1500LT. The measurements confirm the role of the Turkana LLJ in water vapor transport: mean water vapour transport at Marsabit is 172 kg.m.s-1. The dataset provides new opportunities to understand regional dynamics, and to evaluate models in one of the most data sparse regions in the world.

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Huiling Ouyang, Xu Tang, Rajesh Kumar, Renhe Zhang, Guy Brasseur, Ben Churchill, Mozaharul Alam, Haidong Kan, Hong Liao, Tong Zhu, Emily Ying Yang Chan, Ranjeet Sokhi, Jiacan Yuan, Alexander Baklanov, Jianmin Chen, and Maria Katherina Patdu

Abstract

Air pollution is estimated to contribute to approximately 7 million premature deaths, of which around 4.5 million deaths are linked to ambient (outdoor) air pollution (Murray et al. 2020). The deaths attributed to air pollution rank the highest in the Asian Region and thus the implementation of the stricter World Health Organization (WHO) Global Air Quality Guidelines (AQGs) released on 22 Sep 2021 will generate the greatest health benefits in the Asian region. Here we present some key messages and recommendations at national, regional, and global level to promote the strategies for implementation of the ambitious WHO 2021 AQGs in the Asian region.

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Chidong Zhang, John M. Wallace, Robert A. Houze, Edward J. Zipser, and Kerry A. Emanuel

Abstract

This article documents historically the planning of the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE), the largest atmospheric field program of all time. In its earliest planning, GATE was called the Tropical Meteorological Experiment (TROMEX) and designed to be in the tropical western Pacific. For reasons including concerns of the U.S. Department of Defense, the international project was relocated to the tropical Atlantic and renamed GATE.

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Nick Dunstone, Julia Lockwood, Balakrishnan Solaraju-Murali, Katja Reinhardt, Eirini E. Tsartsali, Panos J. Athanasiadis, Alessio Bellucci, Anca Brookshaw, Louis-Philippe Caron, Francisco J. Doblas-Reyes, Barbara Früh, Nube González-Reviriego, Silvio Gualdi, Leon Hermanson, Stefano Materia, Andria Nicodemou, Dario Nicolì, Klaus Pankatz, Andreas Paxian, Adam Scaife, Doug Smith, and Hazel E. Thornton

Abstract

The decadal timescale (˜1 –10 years) bridges the gap between seasonal predictions and longer-term climate projections. It is a key planning timescale for users in many sectors as they seek to adapt to our rapidly changing climate. Whilst significant advances in using initialized climate models to make skilful decadal predictions have been made in the last decades, including co-ordinated international experiments and multi-model forecast exchanges, few user-focussed decadal climate services have been developed. Here we highlight the potential of decadal climate services using four case studies from a project led by four institutions that produce real-time decadal climate predictions. Working in co-development with users in agriculture, energy, infrastructure and insurance sectors, four prototype climate service products were developed. This study describes the challenge of trying to match user needs with the current scientific capability. For example, the use of large ensembles (achieved via a multi-system approach) and skilfully predicted large-scale environmental conditions, are found to improve regional predictions, particularly in mid-latitudes. For each climate service, a two-page ‘product sheet’ template was developed that provides users with both a concise probabilistic forecast and information on retrospective performance. We describe the development cycle, where valuable feedback was obtained from a ‘showcase event’ where a wider group of sector users were engaged. We conclude that for society to take full and rapid advantage of useful decadal climate services, easier and more timely access to decadal climate prediction data is required, along with building wider community expertise in their use.

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Xiang Xiao, Yangyang Xu, Xiaorui Zhang, Fan Wang, Xiao Lu, Zongwei Cai, Guy Brasseur, and Meng Gao

Abstract

Climate change and air pollution are two intimately interlinked global concerns. The frequency, intensity, and duration of heat waves are projected to increase globally under future climate change. A growing body of evidence indicates that health risks associated with the joint exposure to heat waves and air pollution can be greater than that due to individual factors. However, the cooccurrences of heat and air pollution extremes in China remain less explored in the observational records. Here we investigate the spatial pattern and temporal trend of frequency, intensity, and duration of cooccurrences of heat and air pollution extremes using China’s nationwide observations of hourly PM2.5 and O3, and the ERA5 reanalysis dataset over 2013–20. We identify a significant increase in the frequency of cooccurrence of wet-bulb temperature (Tw) and O3 exceedances (beyond a certain predefined threshold), mainly in the Beijing–Tianjin–Hebei (BTH) region (up by 4.7 days decade−1) and the Yangtze River delta (YRD). In addition, we find that the increasing rate (compared to the average levels during the study period) of joint exceedance is larger than the rate of Tw and O3 itself. For example, Tw and O3 coextremes increased by 7.0% in BTH, higher than the percentage increase of each at 0.9% and 5.5%, respectively. We identify same amplification for YRD. This ongoing upward trend in the joint occurrence of heat and O3 extremes should be recognized as an emerging environmental issue in China, given the potentially larger compounding impact to public health.

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Lynn A. McMurdie, Gerald M. Heymsfield, John E. Yorks, Scott A. Braun, Gail Skofronick-Jackson, Robert M. Rauber, Sandra Yuter, Brian Colle, Greg M. McFarquhar, Michael Poellot, David R. Novak, Timothy J. Lang, Rachael Kroodsma, Matthew McLinden, Mariko Oue, Pavlos Kollias, Matthew R. Kumjian, Steven J. Greybush, Andrew J. Heymsfield, Joseph A. Finlon, Victoria L. McDonald, and Stephen Nicholls

Abstract

The Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) is a NASA-sponsored field campaign to study wintertime snowstorms focusing on East Coast cyclones. This large cooperative effort takes place during the winters of 2020–23 to study precipitation variability in winter cyclones to improve remote sensing and numerical forecasts of snowfall. Snowfall within these storms is frequently organized in banded structures on multiple scales. The causes for the occurrence and evolution of a wide spectrum of snowbands remain poorly understood. The goals of IMPACTS are to characterize the spatial and temporal scales and structures of snowbands, understand their dynamical, thermodynamical, and microphysical processes, and apply this understanding to improve remote sensing and modeling of snowfall. The first deployment took place in January–February 2020 with two aircraft that flew coordinated flight patterns and sampled a range of storms from the Midwest to the East Coast. The satellite-simulating ER-2 aircraft flew above the clouds and carried a suite of remote sensing instruments including cloud and precipitation radars, lidar, and passive microwave radiometers. The in situ P-3 aircraft flew within the clouds and sampled environmental and microphysical quantities. Ground-based radar measurements from the National Weather Service network and a suite of radars located on Long Island, New York, along with supplemental soundings and the New York State Mesonet ground network provided environmental context for the airborne observations. Future deployments will occur during the 2022 and 2023 winters. The coordination between remote sensing and in situ platforms makes this a unique publicly available dataset applicable to a wide variety of interests.

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