Xue Yan

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Xue
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Yan
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  • Article
    The global ocean water cycle in atmospheric reanalysis, satellite, and ocean salinity
    (American Meteorological Society, 2017-05-02) Yu, Lisan ; Jin, Xiangze ; Josey, Simon A. ; Lee, Tong ; Kumar, Arun ; Wen, Caihong ; Xue, Yan
    This study provides an assessment of the uncertainty in ocean surface (OS) freshwater budgets and variability using evaporation E and precipitation P from 10 atmospheric reanalyses, two combined satellite-based E − P products, and two observation-based salinity products. Three issues are examined: the uncertainty level in the OS freshwater budget in atmospheric reanalyses, the uncertainty structure and association with the global ocean wet/dry zones, and the potential of salinity in ascribing the uncertainty in E − P. The products agree on the global mean pattern but differ considerably in magnitude. The OS freshwater budgets are 129 ± 10 (8%) cm yr−1 for E, 118 ± 11 (9%) cm yr−1 for P, and 11 ± 4 (36%) cm yr−1 for E − P, where the mean and error represent the ensemble mean and one standard deviation of the ensemble spread. The E − P uncertainty exceeds the uncertainty in E and P by a factor of 4 or more. The large uncertainty is attributed to P in the tropical wet zone. Most reanalyses tend to produce a wider tropical rainband when compared to satellite products, with the exception of two recent reanalyses that implement an observation-based correction for the model-generated P over land. The disparity in the width and the extent of seasonal migrations of the tropical wet zone causes a large spread in P, implying that the tropical moist physics and the realism of tropical rainfall remain a key challenge. Satellite salinity appears feasible to evaluate the fidelity of E − P variability in three tropical areas, where the uncertainty diagnosis has a global indication.
  • Article
    The tropical Atlantic observing system
    (Frontiers Media, 2019-05-10) Foltz, Gregory R. ; Brandt, Peter ; Richter, Ingo ; Rodriguez-fonseca, Belen ; Hernandez, Fabrice ; Dengler, Marcus ; Rodrigues, Regina ; Schmidt, Jörn Oliver ; Yu, Lisan ; Lefevre, Nathalie ; Cotrim Da Cunha, Leticia ; McPhaden, Michael J. ; Araujo, Moacyr ; Karstensen, Johannes ; Hahn, Johannes ; Martín-Rey, Marta ; Patricola, Christina ; Poli, Paul ; Zuidema, Paquita ; Hummels, Rebecca ; Perez, Renellys ; Hatje, Vanessa ; Luebbecke, Joke ; Polo, Irene ; Lumpkin, Rick ; Bourlès, Bernard ; Asuquo, Francis Emile ; Lehodey, Patrick ; Conchon, Anna ; Chang, Ping ; Dandin, Philippe ; Schmid, Claudia ; Sutton, Adrienne J. ; Giordani, Hervé ; Xue, Yan ; Illig, Serena ; Losada, Teresa ; Grodsky, Semyon A. ; Gasparin, Florent ; Lee, Tong ; Mohino, Elsa ; Nobre, Paulo ; Wanninkhof, Rik ; Keenlyside, Noel S. ; Garcon, Veronique Cameille ; Sanchez-Gomez, Emilia ; Nnamchi, Hyacinth ; Drevillon, Marie ; Storto, Andrea ; Remy, Elisabeth ; Lazar, Alban ; Speich, Sabrina ; Goes, Marlos Pereira ; Dorrington, Tarquin ; Johns, William E. ; Moum, James N. ; Robinson, Carol ; Perruche, Coralie ; de Souza, Ronald Buss ; Gaye, Amadou ; Lopez-Parages, Jorge ; Monerie, Paul-Arthur ; Castellanos, Paola ; Benson, Nsikak U. ; Hounkonnou, Mahouton Norbert ; Trotte Duha, Janice ; Laxenaire, Rémi ; Reul, Nicolas
    he tropical Atlantic is home to multiple coupled climate variations covering a wide range of timescales and impacting societally relevant phenomena such as continental rainfall, Atlantic hurricane activity, oceanic biological productivity, and atmospheric circulation in the equatorial Pacific. The tropical Atlantic also connects the southern and northern branches of the Atlantic meridional overturning circulation and receives freshwater input from some of the world’s largest rivers. To address these diverse, unique, and interconnected research challenges, a rich network of ocean observations has developed, building on the backbone of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). This network has evolved naturally over time and out of necessity in order to address the most important outstanding scientific questions and to improve predictions of tropical Atlantic severe weather and global climate variability and change. The tropical Atlantic observing system is motivated by goals to understand and better predict phenomena such as tropical Atlantic interannual to decadal variability and climate change; multidecadal variability and its links to the meridional overturning circulation; air-sea fluxes of CO2 and their implications for the fate of anthropogenic CO2; the Amazon River plume and its interactions with biogeochemistry, vertical mixing, and hurricanes; the highly productive eastern boundary and equatorial upwelling systems; and oceanic oxygen minimum zones, their impacts on biogeochemical cycles and marine ecosystems, and their feedbacks to climate. Past success of the tropical Atlantic observing system is the result of an international commitment to sustained observations and scientific cooperation, a willingness to evolve with changing research and monitoring needs, and a desire to share data openly with the scientific community and operational centers. The observing system must continue to evolve in order to meet an expanding set of research priorities and operational challenges. This paper discusses the tropical Atlantic observing system, including emerging scientific questions that demand sustained ocean observations, the potential for further integration of the observing system, and the requirements for sustaining and enhancing the tropical Atlantic observing system.
  • Article
    Understanding ENSO diversity
    (American Meteorological Society, 2015-06) Capotondi, Antonietta ; Wittenberg, Andrew T. ; Newman, Matthew ; Di Lorenzo, Emanuele ; Yu, Jin-Yi ; Braconnot, Pascale ; Cole, Julia ; Dewitte, Boris ; Giese, Benjamin ; Guilyardi, Eric ; Jin, Fei-Fei ; Karnauskas, Kristopher B. ; Kirtman, Benjamin ; Lee, Tong ; Schneider, Niklas ; Xue, Yan ; Yeh, Sang-Wook
    El Niño–Southern Oscillation (ENSO) is a naturally occurring mode of tropical Pacific variability, with global impacts on society and natural ecosystems. While it has long been known that El Niño events display a diverse range of amplitudes, triggers, spatial patterns, and life cycles, the realization that ENSO’s impacts can be highly sensitive to this event-to-event diversity is driving a renewed interest in the subject. This paper surveys our current state of knowledge of ENSO diversity, identifies key gaps in understanding, and outlines some promising future research directions.
  • Preprint
    How do uncertainties in NCEP R2 and CFSR surface fluxes impact tropical ocean simulations?
    ( 2016-12) Wen, Caihong ; Xue, Yan ; Kumar, Arun ; Behringer, David W. ; Yu, Lisan
    NCEP/DOE reanalysis (R2) and Climate Forecast System Reanalysis (CFSR) surface fluxes are widely used by the research community to understand surface flux climate variability, and to drive ocean models as surface forcings. However, large discrepancies exist between these two products, including (1) stronger trade winds in CFSR than in R2 over the tropical Pacific prior 2000; (2) excessive net surface heat fluxes into ocean in CFSR than in R2 with an increase in difference after 2000. The goals of this study are to examine the sensitivity of ocean simulations to discrepancies between CFSR and R2 surface fluxes, and to assess the fidelity of the two products. A set of experiments, where an ocean model was driven by a combination of surface flux component from R2 and CFSR, were carried out. The model simulations were contrasted to identify sensitivity to different component of the surface fluxes in R2 and CFSR. The accuracy of the model simulations was validated against the tropical moorings data, altimetry SSH and SST reanalysis products. Sensitivity of ocean simulations showed that temperature bias difference in the upper 100m is mostly sensitive to the differences in surface heat fluxes, while depth of 20°C (D20) bias difference is mainly determined by the discrepancies in momentum fluxes. D20 simulations with CFSR winds agree with observation well in the western equatorial Pacific prior 2000, but have large negative bias similar to those with R2 winds after 2000, partly because easterly winds over the central Pacific were underestimated in both CFSR and R2. On the other hand, the observed temperature variability is well reproduced in the tropical Pacific by simulations with both R2 and CFSR fluxes. Relative to the R2 fluxes, the CFSR fluxes improve simulation of interannual variability in all three tropical oceans to a varying degree. The improvement in the tropical Atlantic is most significant and is largely attributed to differences in surface winds.