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  • 1
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    Online Resource
    Drivers and physical processes of drought events over the State of São Paulo, Brazil
    Springer Science and Business Media LLC ; 2022
    In:  Climate Dynamics Vol. 58, No. 11-12 ( 2022-06), p. 3105-3119
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 58, No. 11-12 ( 2022-06), p. 3105-3119
    Abstract: The State of São Paulo, Brazil (SSP) was impacted by severe water shortages during the intense austral summer drought of 2013/2014 and 2014/2015 (1415SD). This study seeks to understand the features and physical processes associated with these summer droughts in the context of other droughts over the region during 1961–2010. Thus, this study examines the spatio-temporal characteristics of anomalously low precipitation over SSP and the associated large-scale dynamics at seasonal timescales, using an observation-based dataset from the Climatic Research Unit (CRU) and model simulation outputs from the Met Office Hadley Centre Global Environment Model (HadGEM3-GA6 at N216 resolution). The study analyzes Historical and Natural simulations from the model to examine the role of human-induced climate forcing on droughts over SSP. Composites of large-scale fields associated with droughts are derived from ERA-20C and ERA-Interim reanalysis and the model simulations. HadGEM3-GA6 simulations capture the observed interannual variability of normalized precipitation anomalies over SSP, but with biases. Drought events over SSP are related to subsidence over the region. This is associated with reduced atmospheric moisture over the region as indicated by the analysis of the vertically integrated moisture flux convergence, which is dominated by reduced moisture flux convergence. The Historical simulations simulate the subsidence associated with droughts, but there are magnitude and location biases. The similarities between the circulation features of the severe 1415SD and other drought events over the region show that understanding of the dynamics of the past drought events over SSP could guide assessment of changes in risk of future droughts and improvements of model performance. The study highlights the merits and limitations of the HadGEM3-GA6 simulations. The model possesses the skills in simulating the large-scale atmospheric circulations modulating precipitation variability, leading to drought conditions over SSP.
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-021-06091-2
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Effect of the Atlantic Multidecadal Variability on the Global Monsoon
    American Geophysical Union (AGU) ; 2019
    In:  Geophysical Research Letters Vol. 46, No. 3 ( 2019-02-16), p. 1765-1775
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 46, No. 3 ( 2019-02-16), p. 1765-1775
    Abstract: Changes in atmospheric circulation dominate the AMV effect on monsoons, while thermodynamic changes are moderate The tropical North Atlantic largely forces AMV effects, by strengthening interhemispheric thermal gradients and the Walker circulation The effects of AMV are not linearly related to the magnitude of warming
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2018GL080903
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    The Driving Processes of Concurrent Hot and Dry Extreme Events in China
    American Meteorological Society ; 2021
    In:  Journal of Climate Vol. 34, No. 5 ( 2021-03), p. 1809-1824
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 34, No. 5 ( 2021-03), p. 1809-1824
    Abstract: Subseasonal heatwave-driven concurrent hot and dry extreme events (HDEs) can cause substantial damage to crops, and hence to lives and livelihoods. However, the physical processes that lead to these devastating events are not well understood. Based on observations and reanalysis data for 1979–2016 over China, we show that HDEs occur preferentially over central and eastern China (CEC) and southern China (SC), with a maximum of three events per year along the Yangtze Valley. The probability of longer-lived and potentially more damaging HDEs is larger in SC than in CEC. Over SC the key factors of HDEs—positive anomalies of surface air temperature and evapotranspiration, and negative anomalies of soil moisture—begin two pentads before maximizing at the peak of the HDEs. These anomalies occur south of a positive height anomaly at 200 hPa, associated with a large-scale subsidence anomaly. The processes over CEC are similar to those for SC, but the anomalies begin one pentad before the peak. HDE frequency is strongly related to the Silk Road pattern and the boreal summer intraseasonal oscillation. Positive phases of the Silk Road pattern and suppressed phases of the boreal summer intraseasonal oscillation are associated with positive height anomalies over CEC and SC, increasing HDE frequency by about 35%–54% relative to the climatological mean. Understanding the effects of subseasonal and seasonal atmospheric circulation variability, such as the Silk Road pattern and boreal summer intraseasonal oscillation, on HDEs is important to improve HDE predictions over China.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-19-0760.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 4
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    Online Resource
    Physical processes of summer extreme rainfall interannual variability in eastern China: Part I—observational analysis
    Springer Science and Business Media LLC ; 2022
    In:  Climate Dynamics Vol. 59, No. 1-2 ( 2022-07), p. 201-217
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 59, No. 1-2 ( 2022-07), p. 201-217
    Abstract: Extreme precipitation can have catastrophic effects in China by triggering floods, landslides, and other natural disasters. We measure extreme precipitation over eastern China by the maximum of five-day precipitation amount (Rx5day) in June, July, and August (JJA), which contributes more than 20% of the climate mean of JJA regional total precipitation. Based on the empirical orthogonal teleconnection (EOT) method, this work identifies four dominant regions of observed Rx5day interannual variability in eastern China: north-eastern China (EOT1), the southern lower reaches of the Yangtze valley (EOT2), southern China (EOT3) and the northern lower reaches of the Yangtze valley (EOT4). EOT1 extreme precipitation is related to a strong East Asian Summer Monsoon (EASM), a weak monsoon front and a northward displaced upper-tropospheric westerly jet. EOT2 and EOT4 extreme precipitation are related to an enhanced and stable monsoon front and a strong western North Pacific subtropical high (WNPSH). The WNPSH associated with EOT4 is stronger than that associated with EOT2, which pushes the monsoon front further north. EOT3 represents extreme precipitation that is related to anomalous southerlies around the western ridge of the WNPSH. The southerlies transport warm and moist air to southern China and increase precipitation there. The four key regions and the related mechanisms are not sensitive to the EOT technique, as the EOT-based extreme precipitation patterns and circulation anomalies are confirmed using Self-Organising Maps (SOMs).
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-021-06123-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Attribution of Forced Decadal Climate Change in Coupled and Uncoupled Ocean–Atmosphere Model Experiments
    American Meteorological Society ; 2017
    In:  Journal of Climate Vol. 30, No. 16 ( 2017-08), p. 6203-6223
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 30, No. 16 ( 2017-08), p. 6203-6223
    Abstract: There is still no consensus about the best methodology for attributing observed changes in climate or climate events. One widely used approach relies on experiments in which the time periods of interest are simulated using an atmospheric general circulation model (AGCM) forced by prescribed sea surface temperatures (SSTs), with and without estimated anthropogenic influences. A potential limitation of such experiments is the lack of explicit atmosphere–ocean coupling; therefore a key question is whether the attribution statements derived from such studies are in fact robust. In this research the authors have carried out climate model experiments to test attribution conclusions in a situation where the answer is known—a so-called perfect model approach. The study involves comparing attribution conclusions for decadal changes derived from experiments with a coupled climate model (specifically an AGCM coupled to an ocean mixed-layer model) with conclusions derived from parallel experiments with the same AGCM forced by SSTs derived from the coupled model simulations. Results indicate that attribution conclusions for surface air temperature changes derived from AGCM experiments are generally robust and not sensitive to air–sea coupling. However, changes in seasonal mean and extreme precipitations, and circulation in some regions, show large sensitivity to air–sea coupling, notably in the summer monsoons over East Asia and Australia. Comparison with observed changes indicates that the coupled simulations generally agree better with observations. These results demonstrate that the AGCM-based attribution method has limitations and may lead to erroneous attribution conclusions in some regions for local circulation and mean and extreme precipitation. The coupled mixed-layer model used in this study offers an alternative and, in some respects, superior tool for attribution studies.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-16-0578.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 6
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    Online Resource
    Anthropogenic Influence on Decadal Changes in Concurrent Hot and Dry Events over China around the Mid-1990s
    Springer Science and Business Media LLC ; 2024
    In:  Advances in Atmospheric Sciences Vol. 41, No. 2 ( 2024-02), p. 233-246
    Details
    In: Advances in Atmospheric Sciences, Springer Science and Business Media LLC, Vol. 41, No. 2 ( 2024-02), p. 233-246
    Abstract: 高温干旱事件是高温和干旱同时发生的天气事件。20世纪90年代中期,中国4至9月(生长季节)高温干旱事件的频率和持续时间呈现出显著的年代际变化,这主要表现在中国大部分地区的高温干旱事件频率和持续时间显著增加。其中中国东南部、中国北部和中国东北部的增加幅度相对较大。近期(1994–2011)中国平均高温干旱事件的频率是早期(1964–1981)的2倍,持续时间较早期增加了60%。 本文利用英国气象局数值模式(MetUM-GOML2)的气候试验估算了人类活动强迫对中国高温干旱事件年代际变化的贡献。试验结果表明,人类活动强迫的变化可以解释观测中60%-70%的高温干旱事件的年代际变化。这表明20世纪90年代中期中国高温干旱的年代际变化主要受到人类活动的影响。独立强迫试验表明,温室气体浓度的增加是导致试验中高温干旱事件年代际变化的主要因素,主要表现在中国高温干旱事件频率和持续时间的增加。人为排放气溶胶的变化则显著减少了中国东南部和北部地区高温干旱事件发生的频率和持续时间,但减少的幅度远小于温室气体所导致的增加幅度。人类活动强迫引起的高温干旱事件年代际变化主要由人类活动强迫影响的季节平均地表气温年代际变化导致。土壤水分和蒸散发的变率变化和季节平均变化贡献相对较小。本文也揭示了中国高温干旱事件响应温室气体浓度和人为排放气溶胶的变化的物理过程。
    Type of Medium: Online Resource
    ISSN: 0256-1530 , 1861-9533
    URL: Article
    DOI: 10.1007/s00376-023-2319-z
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2024
    detail.hit.zdb_id: 2228064-9
    SSG: 6,25
    SSG: 16,13
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