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  • 1
    Online Resource
    Online Resource
    Impacts of the Madden–Julian oscillation on precipitation extremes in Indonesia
    Wiley ; 2021
    In:  International Journal of Climatology Vol. 41, No. 3 ( 2021-03-15), p. 1970-1984
    Details
    In: International Journal of Climatology, Wiley, Vol. 41, No. 3 ( 2021-03-15), p. 1970-1984
    Abstract: The influence of the Madden–Julian oscillation (MJO) on the precipitation extremes in Indonesia during the rainy season (October to April) has been evaluated using the daily station rain gauge data from 1987 to 2017 and the gridded Asian Precipitation–Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE) from 1998 to 2015 for different phases of the MJO. The results show that MJO significantly modulates the frequency of extreme precipitation events in Indonesia, with the magnitude of the impact varying across regions. Specifically, the convectively active (suppressed) MJO increases (decreases) the probability of extreme precipitation events over the western and central parts of Indonesia by up to 70% (40%). In the eastern part of Indonesia, MJO increases (decreases) extreme precipitation probability by up to 50% (40%). We attribute the differences in the probability of extreme precipitation events to the changes in the horizontal moisture flux convergence induced by MJO. The results indicate that the MJO provides the source of predictability of daily extreme precipitation in Indonesia.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v41.3
    DOI: 10.1002/joc.6941
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Role of Finite-Amplitude Rossby Waves and Nonconservative Processes in Downward Migration of Extratropical Flow Anomalies
    American Meteorological Society ; 2018
    In:  Journal of the Atmospheric Sciences Vol. 75, No. 5 ( 2018-05), p. 1385-1401
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 75, No. 5 ( 2018-05), p. 1385-1401
    Abstract: There is growing evidence that stratospheric variability exerts a noticeable imprint on tropospheric weather and climate. Despite clear evidence of these impacts, the principal mechanism whereby stratospheric variability influences tropospheric circulation has remained elusive. Here, the authors introduce a novel approach, based on the theory of finite-amplitude wave activity, for quantifying the role of adiabatic and nonconservative effects on the mean flow that shape the downward coupling from the stratosphere to the troposphere during stratospheric vortex weakening (SVW) events. The advantage of using this theory is that eddy effects (at finite amplitude) on the mean flow can be more readily distinguished from nonconservative effects. The results show (in confirmation of previous work) that the downward migration of extratropical wind anomalies is largely attributable to dynamical adjustments induced by fluctuating finite-amplitude wave forcing. The nonconservative effects, on the other hand, contribute to maintaining the downward signals in the recovery stage within the stratosphere, hinting at the importance of mixing and diabatic heating. The analysis further indicates that variations in stratospheric finite-amplitude wave forcing are too weak to account for the attendant changes and shapes in the tropospheric flow. It is suggested that the indirect effect of tropospheric finite-amplitude wave activity through the residual displacements is needed to amplify and prolong the tropospheric wind responses over several weeks. The results also reveal that the local tropospheric wave activity over the North Pacific and North Atlantic sectors plays a significant role in shaping the high-latitude tropospheric wind response to SVW events.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    URL: Article
    DOI: 10.1175/JAS-D-17-0376.1
    DOI: 10.1175/JAS-D-17-0376.s1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 3
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    Online Resource
    Influence of the Quasi-Biennial Oscillation and Sea Surface Temperature Variability on Downward Wave Coupling in the Northern Hemisphere
    American Meteorological Society ; 2016
    In:  Journal of the Atmospheric Sciences Vol. 73, No. 5 ( 2016-05-01), p. 1943-1965
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 73, No. 5 ( 2016-05-01), p. 1943-1965
    Abstract: Downward wave coupling occurs when an upward-propagating planetary wave from the troposphere decelerates the flow in the upper stratosphere and forms a downward reflecting surface that redirects waves back to the troposphere. To test this mechanism and potential factors influencing the downward wave coupling, three 145-yr sensitivity simulations with NCAR’s Community Earth System Model [CESM1(WACCM)], a state-of-the-art high-top chemistry–climate model, are analyzed. The results show that the quasi-biennial oscillation (QBO) and SST variability significantly impact downward wave coupling. Without the QBO, the occurrence of downward wave coupling is significantly suppressed. In contrast, stronger and more persistent downward wave coupling occurs when SST variability is excluded. The above influence on the occurrence of downward wave coupling is mostly due to a direct influence of the QBO and SST variability on stratospheric planetary wave source and propagation. The strengths of the tropospheric circulation and surface responses to a given downward wave coupling event, however, behave differently. The surface anomaly is significantly weaker (stronger) in the experiment with fixed SSTs (without QBO), even though the statistical signal of downward wave coupling is strongest (weakest) in this experiment. This apparent mismatch is explained by the differences in the strength of the synoptic-scale eddy–mean flow feedback and the possible contribution of SST anomalies in the North Atlantic during the downward wave coupling event. The weaker synoptic-scale eddy–mean flow feedback and the absence of the positive NAO-related SST-tripole pattern in the fixed SST experiment are consistent with a weaker tropospheric response to downward wave coupling. The results highlight the importance of synoptic-scale eddies in setting the tropospheric response to downward wave coupling.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-15-0072.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 4
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    Online Resource
    Downward Wave Coupling between the Stratosphere and Troposphere under Future Anthropogenic Climate Change
    American Meteorological Society ; 2018
    In:  Journal of Climate Vol. 31, No. 10 ( 2018-05-15), p. 4135-4155
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 31, No. 10 ( 2018-05-15), p. 4135-4155
    Abstract: Downward wave coupling (DWC) is an important process that characterizes the dynamical coupling between the stratosphere and troposphere via planetary wave reflection. A recent modeling study has indicated that natural forcing factors, including sea surface temperature (SST) variability and the quasi-biennial oscillation (QBO), influence DWC and the associated surface impact in the Northern Hemisphere (NH). In light of this, the authors further investigate how DWC in the NH is affected by anthropogenic forcings, using a fully coupled chemistry–climate model CESM1(WACCM). The results indicate that the occurrence of DWC is significantly suppressed in the future, starting later in the seasonal cycle, with more events concentrated in late winter (February and March). The future decrease in DWC events is associated with enhanced wave absorption in the stratosphere due to increased greenhouse gases (GHGs), which is manifest as more absorbing types of stratospheric sudden warmings (SSWs) in early winter. This early winter condition leads to a delay in the development of the upper-stratospheric reflecting surface, resulting in a shift in the seasonal cycle of DWC toward late winter in the future. The tropospheric responses to DWC events in the future exhibit different spatial patterns, compared to those of the past. In the North Atlantic sector, DWC-induced circulation changes are characterized by a poleward shift and an eastward extension of the tropospheric jet, while in the North Pacific sector, the circulation changes are characterized by a weakening of the tropospheric jet. These responses are consistent with a change in the pattern of DWC-induced synoptic-scale eddy–mean flow interaction in the future.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-17-0382.1
    DOI: 10.1175/JCLI-D-17-0382.s1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 5
    Online Resource
    Online Resource
    Impact of the Antarctic Ozone Hole on the Vertical Coupling of the Stratosphere–Mesosphere–Lower Thermosphere System
    American Meteorological Society ; 2016
    In:  Journal of the Atmospheric Sciences Vol. 73, No. 6 ( 2016-06-01), p. 2509-2528
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 73, No. 6 ( 2016-06-01), p. 2509-2528
    Abstract: There is evidence that the strengthened stratospheric westerlies arising from the Antarctic ozone hole–induced cooling cause a polar mesospheric warming and a subsequent cooling in the lower thermosphere. While previous studies focus on the role of nonresolved (gravity) wave drag filtering, here the role of resolved (planetary) wave drag and radiative forcing on the Antarctic mesosphere and lower thermosphere (MLT) is explored in detail. Using simulations with NCAR’s Community Earth System Model, version 1 (Whole Atmosphere Community Climate Model) [CESM1(WACCM)], it is found that in late spring and early summer the anomalous polar mesospheric warming induced by easterly nonresolved wave drag is dampened by anomalous dynamical cooling induced by westerly resolved wave drag. This resolved wave drag is attributed to planetary-scale wave (k = 1–3) activity, which is generated in situ as a result of increased instability of the summer mesospheric easterly jet induced by the ozone hole. On the other hand, the anomalous cooling in the polar lower thermosphere induced by westerly nonresolved wave drag is enhanced by anomalous dynamical cooling due to westerly resolved wave drag. In addition, radiative effects from increased greenhouse gases during the ozone hole period contribute partially to the cooling in the polar lower thermosphere. The polar MLT temperature response to the Antarctic ozone hole is, through thermal wind balance, accompanied by the downward migration of anomalous zonal-mean wind from the lower thermosphere to the stratopause. The results highlight that a proper accounting of both dynamical and radiative effects is required in order to correctly attribute the causes of the polar MLT response to the Antarctic ozone hole.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    URL: Article
    DOI: 10.1175/JAS-D-15-0189.1
    DOI: 10.1175/JAS-D-15-0189.s1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 6
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    Corrigendum
    American Meteorological Society ; 2023
    In:  Journal of the Atmospheric Sciences Vol. 80, No. 4 ( 2023-04), p. 1211-
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 80, No. 4 ( 2023-04), p. 1211-
    Abstract: This corrigendum corrects a typo in Eq. (10) of Lubis and Hassanzadeh (2021) for calculating the cross-EOF feedbacks.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-23-0034.1
    RVK:
    UA 4800
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 7
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    How does downward planetary wave coupling affect polar stratospheric ozone in the Arctic winter stratosphere?
    Copernicus GmbH ; 2017
    In:  Atmospheric Chemistry and Physics Vol. 17, No. 3 ( 2017-02-15), p. 2437-2458
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 17, No. 3 ( 2017-02-15), p. 2437-2458
    Abstract: Abstract. It is well established that variable wintertime planetary wave forcing in the stratosphere controls the variability of Arctic stratospheric ozone through changes in the strength of the polar vortex and the residual circulation. While previous studies focused on the variations in upward wave flux entering the lower stratosphere, here the impact of downward planetary wave reflection on ozone is investigated for the first time. Utilizing the MERRA2 reanalysis and a fully coupled chemistry–climate simulation with the Community Earth System Model (CESM1(WACCM)) of the National Center for Atmospheric Research (NCAR), we find two downward wave reflection effects on ozone: (1) the direct effect in which the residual circulation is weakened during winter, reducing the typical increase of ozone due to upward planetary wave events and (2) the indirect effect in which the modification of polar temperature during winter affects the amount of ozone destruction in spring. Winter seasons dominated by downward wave reflection events (i.e., reflective winters) are characterized by lower Arctic ozone concentration, while seasons dominated by increased upward wave events (i.e., absorptive winters) are characterized by relatively higher ozone concentration. This behavior is consistent with the cumulative effects of downward and upward planetary wave events on polar stratospheric ozone via the residual circulation and the polar temperature in winter. The results establish a new perspective on dynamical processes controlling stratospheric ozone variability in the Arctic by highlighting the key role of wave reflection.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-17-2437-2017
    DOI: 10.5194/acp-17-2437-2017-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 8
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    Moisture Origin and Transport for Extreme Precipitation over Indonesia’s New Capital City, Nusantara in August 2021
    MDPI AG ; 2022
    In:  Atmosphere Vol. 13, No. 9 ( 2022-08-30), p. 1391-
    Details
    In: Atmosphere, MDPI AG, Vol. 13, No. 9 ( 2022-08-30), p. 1391-
    Abstract: Nusantara, Indonesia’s new capital city, experienced a rare extreme rainfall event on 27–28 August 2021. This heavy rainfall occurred in August, the driest month of the year based on the monthly climatology data, and caused severe flooding and landslides. To better understand the underlying mechanisms for such extreme precipitation events, we investigated the moisture sources and transport processes using the Lagrangian model HYSPLIT. Our findings revealed that moisture was mostly transported to Nusantara along three major routes: from Borneo Island (BRN, 53.73%), the Banda Sea and its surroundings (BSS, 32.03%), and Sulawesi Island (SUL, 9.05%). Overall, BRN and SUL were the main sources of terrestrial moisture, whereas the BSS was the main oceanic moisture source, having a lower contribution than its terrestrial counterpart. The terrestrial moisture transport from BRN was mainly driven by the large-scale high vortex flow, whereas the moisture transport from the SUL was driven by the circulation induced by boreal summer intraseasonal oscillation (BSISO) and low-frequency variability associated with La Niña. The near-surface oceanic moisture transport from BSS is primarily associated with prevailing winds due to the Australian monsoon system. These insights into moisture sources and pathways can potentially improve the accuracy of predictions of summer precipitation extremes in Indonesia’s new capital city, Nusantara, and benefit natural resource managers in the region.
    Type of Medium: Online Resource
    ISSN: 2073-4433
    URL: Article
    DOI: 10.3390/atmos13091391
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2605928-9
    SSG: 23
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  • 9
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    Characteristics of Kelvin waves and Mixed Rossby-Gravity waves in opposite QBO phases
    IOP Publishing ; 2017
    In:  IOP Conference Series: Earth and Environmental Science Vol. 54 ( 2017-01), p. 012032-
    Details
    In: IOP Conference Series: Earth and Environmental Science, IOP Publishing, Vol. 54 ( 2017-01), p. 012032-
    Type of Medium: Online Resource
    ISSN: 1755-1307 , 1755-1315
    URL: Article
    DOI: 10.1088/1755-1315/54/1/012032
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 2434538-6
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  • 10
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    Unprecedented Quasi-Biennial Oscillation (QBO) disruption in 2015-2016: Implications for tropical waves and ozone
    IOP Publishing ; 2019
    In:  IOP Conference Series: Earth and Environmental Science Vol. 284, No. 1 ( 2019-05-01), p. 012016-
    Details
    In: IOP Conference Series: Earth and Environmental Science, IOP Publishing, Vol. 284, No. 1 ( 2019-05-01), p. 012016-
    Abstract: During the Northern Hemisphere (NH) winter of 2015/16, quasi-biennial oscillation (QBO) exhibited a significant disruption that was unprecedented in the observational record. It was characterized by an upward displacement of the westerly wind anomalies. Since traveling wave activity induces the QBO and in turn affects the ozone distribution, it is worth understanding how this anomalous change affects tropical waves activity (including Kelvin and MRG waves) and ozone. This study used assimilated ozone product from the Modern-Era Retrospective Analysis version 2 (MERRA2). The results showed that Kelvin and MRG wave activities are appreciably strong during this period. The strengthening of Kelvin wave activity is consistent with a persistent westerly background flow, favoring upward propagation of Kelvin waves into the stratosphere. On the other hand, the significant strengthening of MRG wave activity may be associated with enhanced equatorward propagation of extratropical Rossby waves due to strong El-Nino event. Furthermore, the results also indicated that the anomalous change in the QBO leads to increasing temperature and ozone concentration in the tropical lower stratosphere. Based on ozone budget analysis, we showed that the increase in total ozone tendency is largely attributable to the increase in dynamical ozone transport, being consistent with the QBO-induced residual circulation between the mid and low latitude, in the lower stratosphere.
    Type of Medium: Online Resource
    ISSN: 1755-1307 , 1755-1315
    URL: Article
    DOI: 10.1088/1755-1315/284/1/012016
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 2434538-6
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