Article
Meteorology & Atmospheric Sciences
Jae-Heung Park, Mi-Kyung Sung, Young-Min Yang, Jiuwei Zhao, Soon-Il An, Jong-Seong Kug
Summary: The North Pacific Oscillation (NPO) plays a role in triggering El Nino-Southern Oscillation (ENSO) through the seasonal footprinting mechanism (SFM). The efficiency of SFM varies among models and depends on the background mean state of the model. Greater intensification of the northern branch of the Pacific intertropical convergence zone (ITCZ) leads to stronger SFM efficiency and better triggers ENSO events.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Fiaz Ahmed, J. David Neelin, Spencer A. Hill, Kathleen A. Schiro, Hui Su
Summary: Tropical areas with mean upward motion, known as the intertropical convergence zone (ITCZ), are expected to contract due to global warming. A simple model based on dry static energy and moisture equations is introduced to understand this process. The model reveals that uniform warming leads to contraction of the ascent area and intensification of precipitation, similar to observations and climate models. Parameters related to water vapor feedbacks, cloud-radiative feedbacks, convection-circulation feedbacks, and moisture export play important roles in the model's results.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Huaxia Liao, Zhichao Cai, Jingsong Guo, Zhenya Song
Summary: ENSO is the most influential interannual climate variability, with a tendency for the mature phase to occur during the boreal winter. In this study, we evaluated the simulation performance of ENSO phase-locking in 50 models of CMIP6 and found that models with an intertropical convergence zone (ITCZ) poleward bias tended to simulate more ENSO events peaking outside the winter season. The ITCZ poleward bias induces a dry bias over the equatorial Pacific, which restrains equatorial precipitation and convection anomalies during ENSO events, leading to a weaker eastern tropical Pacific thermocline anomaly and a peak in ENSO events outside the winter season.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Hirohiko Masunaga
Summary: In this study, the behavior of ITCZ convection near the eastern Pacific was investigated through analysis of satellite observations and reanalysis data. The study found that when precipitation peaks at the ITCZ center, there is a prominent positive peak in diabatic forcing, while when convection develops at the ITCZ edges, there is only a weak diabatic forcing but an import of moist static energy.
JOURNAL OF CLIMATE
(2023)
Article
Geology
Julie Loisel, Kristen Sarna, Zhengyu Xia, Yongsong Huang, Zicheng Yu
Summary: The southern westerly winds have significant impacts on weather patterns and water resources in the southern high-latitude regions. The strengthening and movement of these winds since the late 20th century also contribute to environmental changes such as drought, wildfire, and sea-ice loss. However, identifying the natural variability of the westerlies and predicting their future behavior is challenging due to anthropogenic influences.
Article
Multidisciplinary Sciences
Byron A. Steinman, Nathan D. Stansell, Michael E. Mann, Colin A. Cooke, Mark B. Abbott, Mathias Vuille, Broxton W. Bird, Matthew S. Lachniet, Alejandro Fernandez
Summary: Uncertainty about the influence of anthropogenic radiative forcing on the position and strength of convective rainfall in the Intertropical Convergence Zone (ITCZ) inhibits our ability to project future tropical hydroclimate change in a warmer world. Paleoclimatic and modeling data inform on the timescales and mechanisms of ITCZ variability, yet a comprehensive, long-term perspective remains elusive. The study quantifies the evolution of neotropical hydroclimate over the past millennium and shows an interhemispheric pattern of precipitation antiphasing occurred on multicentury timescales in response to changes in natural radiative forcing. This reinforces the idea that ITCZ responses to external forcing are region specific, complicating projections of the tropical precipitation response to global warming.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Meteorology & Atmospheric Sciences
Gabriel M. P. Perez, Pier Luigi Vidale, Helen Dacre, Jorge L. Garcia-Franco
Summary: This study investigates the relationship between synoptic-scale mixing and precipitation variability. It finds that organized filaments of moisture, known as attracting Lagrangian coherent structures (LCSs), play a key role in precipitation events. The results also show that these LCSs are closely related to circulation mechanisms such as the intertropical convergence zone and monsoon systems.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Laura Paccini, Cathy Hohenegger, Bjorn Stevens
Summary: This study investigates the impact of explicit and parameterized convection representations on the response to the Atlantic meridional mode (AMM), focusing on precipitation responses. Results indicate a linear precipitation response to positive and negative AMM in simulations with explicit convection, compared to parameterized convection. Further analysis suggests that wind-driven enthalpy flux anomalies are generally stronger in simulations with explicit convection, potentially leading to amplified SST anomalies in coupled simulations.
JOURNAL OF CLIMATE
(2021)
Article
Geography, Physical
Patricia Piacsek, Hermann Behling, Fang Gu, Igor Martins Venancio, Douglas V. O. Lessa, Andre Belem, Ana Luiza S. Albuquerque
Summary: Scientific projections suggest that the increase in greenhouse gas levels in the atmosphere will lead to warmer oceans and a thicker upper layer of the thermohaline circulation, restricting productivity areas and favoring oligotrophic conditions. Using organic-walled dinoflagellate cysts, this study reconstructed changes in sea surface hydrography and productivity in the western equatorial Atlantic over the past 130,000 years, revealing glacial-interglacial and millennial-scale variations in dinocyst assemblages.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2021)
Article
Geosciences, Multidisciplinary
Zhikuo Sun, Jianhua Lu
Summary: The study highlights the crucial role of the North Equatorial Countercurrent (NECC) in maintaining the zonality of the Intertropical Convergence Zone (ITCZ) precipitation, emphasizing the impact of NECC on the zonal distribution of ITCZ precipitation.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geosciences, Multidisciplinary
Alexandra Lima Tavares, Renato Oliveira Da Silva Jr, Alexandre Melo Casseb Do Carmo, Gabriel Caixeta Martins, Wilson Da Rocha Nascimento Jr, Douglas Batista Da Silva Ferreira, Marcio Sousa Da Silva, Carlos Eduardo Aguiar De Souza Costa, Paulo Rogenes Pontes, Renata Goncalves Tedeschi
Summary: This study analyzes hourly wind direction and speed data from six subregions along the Itacaiunas River watershed (IRW), Eastern Amazon, over a period of one year. The data is collected from six hydrometeorological stations located in different land use and plant cover areas within the IRW. The study identifies different wind patterns based on prevailing wind directions and speeds at different stations, as well as the influence of environmental factors such as plant cover, land use, and topography. Additionally, the study observes the presence of breeze and mesoscale circulation systems during daytime and nighttime wind cycles.
FRONTIERS IN EARTH SCIENCE
(2023)
Article
Meteorology & Atmospheric Sciences
Alex O. Gonzalez, Indrani Ganguly, Marie C. McGraw, James G. Larson
Summary: This study focuses on the dynamics of the east Pacific Ocean intertropical convergence zone (ITCZ) events, finding a rapid daily evolution and a slower weekly evolution leading up to nITCZ and dITCZ events. Anomalous cross-equatorial flow and off-equatorial convergence intensify rapidly before these events, followed by a peak in near-equatorial zonal wind anomalies. Prior to nITCZ events, there is a wide region north of the southeast Pacific subtropical high where anomalous northwesterlies strengthen, while prior to dITCZ events, anomalous southeasterlies strengthen. Momentum budget analysis reveals the importance of Ekman balance terms before nITCZ events and the meridional momentum advective terms before dITCZ events in promoting variations in cross-equatorial flow.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Jae-Heung Park, Jong-Seong Kug, Young-Min Yang, Hyoeun Oh, Jiuwei Zhao, Yikai Wu
Summary: This study examined the impact of anomalous sea surface temperature in the north tropical Atlantic (NTA) on El Nino-Southern Oscillation (ENSO) and the diversity of this impact in climate models. The analysis found that the strength of NTA's effect on ENSO in the climate models was proportional to the intensity of the climatological subtropical North Pacific high system in boreal spring. The observed NTA effect on ENSO also became stronger during periods when the climatological subtropical North Pacific high intensified, indicating the importance of climatology in the NTA-ENSO connection.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Xiaoqing Liao, Christophere. H. Olloway, Xiangbo Feng, Chunlei Liu, Xinyu Lyu, Yufeng Xue, Ruijuan Bao, Jiandong Li, Fangli Qiao
Summary: There is a lack of well-accepted mechanisms to explain the annual frequency of tropical cyclones (TCs) globally and in individual ocean basins. Recent studies using idealized models have shown that the frequency of TC genesis (TCG) climatology is proportional to the Coriolis parameter associated with the position of the intertropical convergence zone (ITCZ). This study investigates the impact of the ITCZ position on TCG on an interannual time scale, using observations from 1979 to 2020.
JOURNAL OF CLIMATE
(2023)
Article
Geography, Physical
Allana Queiroz de Azevedo, Francisco J. Jimenez-Espejo, Marlon Carlos Franca, Antonio Garcia-Alix, Fernando A. Borges da Silva, Luiz C. R. Pessenda, Marcelo C. L. Cohen, Neuza A. Fontes, Vanessa C. Pinheiro, Kita Macario, Joao C. F. Jr Melo Jr, Marisa de C. Piccolo, Jose A. Bendassolli
Summary: The study found that the late Holocene mangroves near Babitonga Bay in Santa Catarina State, Brazil, were established around 500 years B.C.E. following an increase in humidity, and were sensitive to precipitation patterns.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2021)
Article
Meteorology & Atmospheric Sciences
Alison Ming, V. Holly L. Winton, James Keeble, Nathan L. Abraham, Mohit C. Dalvi, Paul Griffiths, Nicolas Caillon, Anna E. Jones, Robert Mulvaney, Joel Savarino, Markus M. Frey, Xin Yang
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2020)
Article
Environmental Sciences
Olivier Favez, Samuel Weber, Jean-Eudes Petit, Laurent Y. Alleman, Alexandre Albinet, Veronique Riffault, Benjamin Chazeau, Tanguy Amodeo, Dalia Salameh, Yunjiang Zhang, Deepchandra Srivastava, Abdoulaye Samake, Robin Aujay-Plouzeau, Arnaud Papin, Nicolas Bonnaire, Carole Boullanger, Melodie Chatain, Florie Chevrier, Anais Detournay, Marta Dominik-Segue, Raphaele Falhun, Celine Garbin, Veronique Ghersi, Guillaume Grignion, Gilles Levigoureux, Sabrina Pontet, Jerome Rangognio, Shouwen Zhang, Jean-Luc Besombes, Sebastien Conil, Gaelle Uzu, Joel Savarino, Nicolas Marchand, Valerie Gros, Caroline Marchand, Jean-Luc Jaffrezo, Eva Leoz-Garziandia
Summary: The CARA program, led by the French reference laboratory for air quality monitoring and regional monitoring networks since 2008, aims to enhance the national level understanding of particulate matter chemistry and origins in urban environments. The program has resulted in strong collaborations with international academic partners to produce state-of-the-art results and methodologies for air quality stakeholders and decision makers. Studies have highlighted the major influences of residential wood burning, road transport emissions, mineral dust, and primary biogenic particles on air quality, as well as long-range transport phenomena such as the advection of aerosols from European continental sectors and Saharan dust into French West Indies. Additionally, stable isotope measurements and organic molecular markers have been used for a better understanding of the origins of ammonium and organic aerosol fractions.
Article
Meteorology & Atmospheric Sciences
S. Ishino, S. Hattori, M. Legrand, Q. Chen, B. Alexander, J. Shao, J. Huang, L. Jaegle, B. Jourdain, S. Preunkert, A. Yamada, N. Yoshida, J. Savarino
Summary: The study compared Delta O-17 of non-sea-salt sulfate in aerosols between inland and coastal sites in East Antarctica throughout 2011. Results showed consistent seasonality with summer minima and winter maxima, but significant intersite differences were observed in spring-summer and autumn.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Multidisciplinary Sciences
Shohei Hattori, Yoshinori Iizuka, Becky Alexander, Sakiko Ishino, Koji Fujita, Shuting Zhai, Tomas Sherwen, Naga Oshima, Ryu Uemura, Akinori Yamada, Nozomi Suzuki, Sumito Matoba, Asuka Tsuruta, Joel Savarino, Naohiro Yoshida
Summary: Since the 1980s, there has been a slower reduction in atmospheric sulfate compared to dramatic decreases in sulfur dioxide emissions. However, recent observations from a Greenland ice core show an increase in the oxygen isotopic composition of sulfate, indicating that acidity-dependent in-cloud oxidation by ozone has played a larger role in sulfate production since the 1960s. Global chemical transport models confirm an increase in conversion efficiency from SO2 to sulfate in Eastern North America and Western Europe, suggesting a continuing feedback mechanism that may hinder future air quality improvements.
Article
Environmental Sciences
Fanny Larue, Ghislain Picard, Jeremie Aublanc, Laurent Arnaud, Alvaro Robledano-Perez, Emmanuel Le Meur, Vincent Favier, Bruno Jourdain, Joel Savarino, Pierre Thibaut
Summary: This study introduces an extended Snow Model Radiative Transfer (SMRT) to compute radar waveforms and conducts simulations on the Antarctic ice sheet. The research reveals differences in radar wave penetration depth and waveform characteristics at the same locations in different frequency bands.
REMOTE SENSING OF ENVIRONMENT
(2021)
Article
Meteorology & Atmospheric Sciences
A. Barbero, J. Savarino, R. Grilli, C. Blouzon, G. Picard, M. M. Frey, Y. Huang, N. Caillon
Summary: This study introduces a method for measuring NOx flux produced from nitrate photolysis in Antarctica, using dynamic flux chamber measurements. Contrary to expectations, the photolysis rate of nitrate in snow samples of different ages showed no significant variation, suggesting a common photochemical behavior. The results provide insight for improving future atmospheric chemistry models with a new parameterization of nitrate photolysis.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Multidisciplinary Sciences
Pete D. Akers, Joel Savarino, Nicolas Caillon, Aymeric P. M. Servettaz, Emmanuel Le Meur, Olivier Magand, Jean Martins, Cecile Agosta, Peter Crockford, Kanon Kobayashi, Shohei Hattori, Mark Curran, Tas van Ommen, Lenneke Jong, Jason L. Roberts
Summary: This article introduces an alternative proxy for surface mass balance (SMB) in Antarctic ice cores based on photolytic fractionation of nitrogen isotopes in nitrate. By applying this proxy approach to nitrate observed at 114 sites in East Antarctica, the authors reconstruct 700 years of SMB changes and provide SMB values that reflect the immediate local environment independently.
NATURE COMMUNICATIONS
(2022)
Article
Environmental Sciences
G. Celli, W. R. L. Cairns, C. Scarchilli, C. A. Cuevas, A. Saiz-Lopez, J. Savarino, B. Stenni, M. Frezzotti, S. Becagli, B. Delmonte, H. Angot, R. P. Fernandez, A. Spolaor
Summary: In an unexplored part of the East Antarctic Plateau, snow samples were collected during the Eaiist expedition in December 2019. The study focused on the latitudinal variability of iodine, bromine, and sodium, as well as their relation to emission processes and photochemical activation. The results showed that there was no significant latitudinal trend for bromine and sodium, while iodine concentrations decreased moving southward. The study also highlighted the impact of the seasonal ozone hole cycle on the surface snow photoactivation of iodine.
ENVIRONMENTAL RESEARCH
(2023)
Article
Environmental Sciences
Pete D. Akers, Joel Savarino, Nicolas Caillon, Olivier Magand, Emmanuel Le Meur
Summary: Nitrate isotopes in Antarctic snow are modified by photolysis after deposition, but an imprint of the original atmospheric cycles can still be found in the ice, which is valuable for studying past atmospheric chemistry changes.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)
Article
Environmental Sciences
Yanzhi Cao, Zhuang Jiang, Becky Alexander, Jihong Cole-Dai, Joel Savarino, Joseph Erbland, Lei Geng
Summary: Ice-core nitrate isotopes can reflect column ozone variability, but are more sensitive to snow accumulation rate.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)
Article
Multidisciplinary Sciences
Sanjeev Dasari, Guillaume Paris, Julien Charreau, Joel Savarino
Summary: Changes in the cosmic-ray background can affect the Earth's ozone layer, leading to increased penetration of harmful UV radiation. By studying ice-core ΔS-33 records, we have confirmed the link between UV-induced atmospheric photochemical imprints and past ozone-layer depletion events.
Article
Geography, Physical
Zhuang Jiang, Joel Savarino, Becky Alexander, Joseph Erbland, Jean-Luc Jaffrezo, Lei Geng
Summary: The effect of post-depositional processing on the preservation of snow nitrate isotopes at Summit, Greenland, is investigated, with a focus on the impact on δN-15(NO3-). The study emphasizes the importance of understanding the effects of post-depositional processing before interpreting ice-core nitrate isotopes.
Article
Geosciences, Multidisciplinary
G. Picard, H. Lowe, F. Domine, L. Arnaud, F. Larue, V. Favier, E. Le Meur, E. Lefebvre, J. Savarino, A. Royer
Summary: This study improves the snow scattering model by introducing a new microstructural parameter that accurately predicts microwave scattering. It demonstrates the relationship between microwave grain size, optical grain size, and polydispersity, and retrieves the value of polydispersity for different types of snow grains. The findings enable more accurate uses of satellite observations in snow hydrological and meteorological applications.
Article
Geosciences, Multidisciplinary
Laura Crick, Andrea Burke, William Hutchison, Mika Kohno, Kathryn A. Moore, Joel Savarino, Emily A. Doyle, Sue Mahony, Sepp Kipfstuhl, James W. B. Rae, Robert C. J. Steele, R. Stephen J. Sparks, Eric W. Wolff
Summary: Researchers analyzed sulfur isotope compositions in Antarctic ice cores and identified several potential Toba sulfate peaks, with one peak at 73.67 ka showing the largest ever reported magnitude of S-MIF in volcanic sulfate. This peak may be a likely candidate for the Toba super-eruption, with a plume top height in excess of 45 km. Although these candidate eruptions occurred during the transition into Greenland Stadial 20, the relative timing suggests that Toba was not the trigger for the large Northern Hemisphere cooling at this time, although an amplifying effect cannot be ruled out.
CLIMATE OF THE PAST
(2021)
Article
Geography, Physical
Zhuang Jiang, Becky Alexander, Joel Savarino, Joseph Erbland, Lei Geng
Summary: The study suggests that post-depositional processing of snow nitrate can cause significant redistribution of nitrate in the upper snow-pack, with up to 21% loss and/or redistribution after deposition. However, at the annual scale, the net effect of post-depositional processing on atmospheric signals is relatively small under current Summit conditions. Nevertheless, at longer timescales where snow accumulation rates change significantly, post-depositional processing could become a major driver of delta N-15 variability in ice-core nitrate.