Projected changes in the characteristics of the East Asian summer monsoonal front and their impacts on the regional precipitation     

Li  Yana  Lau  Ngar-Cheung  Tam  Chi-Yung  Cheung  Ho-Nam  Deng  Yi  Zhang  Henian 《Climate Dynamics》2021,56(11):4013-4026

Summer monsoonal rainfall over East Asia is dominated by precipitation associated with the East Asian summer monsoonal front (EASMF). A Community Atmospheric Model (CAM5.1) with a high horizontal resolution of 50 km is employed in this study to investigate the interannual variability as well as projected future trends in the EASMF under the Representative Concentration Pathway 8.5 scenario. Seasonal march of the EASMF is reproduced reasonably well in the model’s present-day simulation despite a northward shift of the simulated front from its observed position. Based upon a suite of objectively-defined daily indices of the EASMF, we show that the EASMF in the late twenty-first century will be more intense and displaced eastward and southward from its present-day mean location. Moreover, EASMF events will exhibit a wider meridional expansion and a longer duration. Monsoonal precipitation over East Asia is particularly sensitive to the meridional displacements of EASMF. In conjunction with the projected southward shift of EASMF, an enhanced rain band is seen to extend northeastward from southern China to the northwestern Pacific south of Japan. This precipitation feature is associated with strengthened and southward-shifted westerly jet streams at 250 and 700 hPa, which are respectively linked to tropical warming in the upper troposphere and warming over the South China Sea in the lower troposphere during the twenty-first century. Within the latitudinal “gap” south of the upper-level jet and north of the lower-level jet, the local vorticity tendencies are maintained by upper-level divergence and lower-level convergence, thus accompanied by enhanced upward motion and precipitation. The site at which this “jet stream-precipitation” relationship prevails is notably modulated by long-term trends in the temperature and circulation patterns associated with climate change.

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Giant palaeotsunami in Kiribati: Converging evidence from geology and oral history     

James P. Terry  Robert Karoro  Gennady A. Gienko  Marta Wieczorek  A. Y. Annie Lau 《Island Arc》2021,30(1):e12417

For tsunami science within Oceania, the vast Central and Western Pacific (CEWEP) is an anomalous region because of the scarcity of historical tsunami observations and the complete absence of dated palaeotsunami evidence. This paper therefore records the first dated high-magnitude palaeotsunami event within the CEWEP region. A combination of both geological data and oral history is provided for a palaeotsunami that struck remote Makin island, northernmost of the Gilbert Islands in Kiribati, toward the end of the 16th century. A previously undocumented oral tradition of giant waves is well known to the people of Makin. Narration of this legend by the Wiin te Maneaba, traditional storyteller on Makin, provided important details supporting a tsunami hypothesis. The legend preserves credible information surrounding the giant-wave origin of Rebua and Tokia, two prominent subaerial megaclasts of blade and block geometry that were transported 80–130 m shorewards from the reef-edge source and deposited in sideways and inverted orientations. From available hydrodynamic flow transport equations, minimum flow velocities of 7.3–16.3 m s⁻¹ were generated, depending on whether the reefblocks were rotated or lifted onto the reef platform. The youngest U-Th age-dates for fossil corals retrieved from the reefblocks give a maximum age for the palaeotsunami of circa AD 1576. Several far-field Pacific Rim and regional possibilities exist for tsunamigenesis. These include subduction-zone seismicity and catastrophic volcanic eruption, both of which have been linked to earlier (late 15th century) palaeotsunami events recorded elsewhere in the Pacific Islands. However, the available evidence here suggests that the ~AD 1576 Makin palaeotsunami was more likely to have been locally generated by tsunamigenic offshore submarine slope failure close to Makin's western reef, associated with the giant arcuate bight structure that characterizes the northern rim of Butaritari atoll.  相似文献   

Critical shear stress approach for self-cleansing design of a rectangular channel     

Charles Hin Joo Bong  San Chuin Liew  Fang Yenn Teo  Tze Liang Lau  Aminuddin Ab Ghani 《国际泥沙研究》2021,36(5):678-685

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Carbon-rich extremely metal poor stars: signatures of Population III asymptotic giant branch stars in binary systems     

Herbert H. B. Lau  Richard J. Stancliffe  Christopher A. Tout 《Monthly notices of the Royal Astronomical Society》2007,378(2):563-568

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Competing influences of greenhouse warming and aerosols on Asian summer monsoon circulation and rainfall     

William Ka-Ming Lau  Kyu-Myong Kim 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(2):181-194

In this paper, we have compared and contrasted competing influences of greenhouse gases (GHG) warming and aerosol forcing on Asian summer monsoon circulation and rainfall based on CMIP5 historical simulations. Under GHG-only forcing, the land warms much faster than the ocean, magnifying the pre-industrial climatological land-ocean thermal contrast and hemispheric asymmetry, i.e., warmer northern than southern hemisphere. A steady increasing warm-ocean-warmer-land (WOWL) trend has been in effect since the 1950’s substantially increasing moisture transport from adjacent oceans, and enhancing rainfall over the Asian monsoon regions. However, under GHG warming, increased atmospheric stability due to strong reduction in mid-tropospheric and near surface relative humidity coupled to an expanding subsidence areas, associated with the Deep Tropical Squeeze (DTS, Lau and Kim, 2015b) strongly suppress monsoon convection and rainfall over subtropical and extratropical land, leading to a weakening of the Asian monsoon meridional circulation. Increased anthropogenic aerosol emission strongly masks WOWL, by over 60% over the northern hemisphere, negating to a large extent the rainfall increase due to GHG warming, and leading to a further weakening of the monsoon circulation, through increasing atmospheric stability, most likely associated with aerosol solar dimming and semi-direct effects. Overall, we find that GHG exerts stronger positive rainfall sensitivity, but less negative circulation sensitivity in SASM compared to EASM. In contrast, aerosols exert stronger negative impacts on rainfall, but less negative impacts on circulation in EASM compared to SASM.  相似文献   

Selection of ground motion attenuation model for Peninsular Malaysia due to far-field Sumatra earthquakes     

Tze Che Van  Tze Liang Lau  Chai Fung Mok 《Natural Hazards》2016,80(3):1865-1889

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Influence of aerosol-radiative forcings on the diurnal and seasonal cycles of rainfall over West Africa and Eastern Atlantic Ocean using GCM simulations     

Kyu-Myong Kim  William K.-M. Lau  Yogesh C. Sud  Gregory K. Walker 《Climate Dynamics》2010,35(1):115-126

Effects of aerosol radiative forcing on the diurnal and seasonal cycles of precipitation over West Africa and eastern Atlantic Ocean are investigated for the boreal summer season: June–July–August. An eight year (2000–2007) average of GCM simulated rainfall data is compared with the corresponding TRMM rainfall data. The comparison shows that the amplitude of the diurnal cycles of rainfall over land and ocean are reasonably well simulated. Over land, the phase of the simulated diurnal cycle of precipitation peaks several hours earlier than that of the TRMM data. Corresponding differences over the ocean(s) are relatively smaller. Some of the key features of the aerosol induced model simulated field anomalies are: (a) aerosol direct radiative forcing which increases the atmospheric stability and reduces the daytime moist convection and convective precipitation; (b) the aerosol induced changes in the diurnal cycle of precipitation are out of phase with those of the TRMM data over land, but are in-phase over the ocean; (c) aerosols reduce the amplitude of the diurnal cycle of precipitation over land and enhance it over ocean. However, the phase of the diurnal cycle is not affected much by the aerosol radiative forcing both over land and ocean. During the boreal summer, aerosol radiative forcing and induced circulation and precipitation cool the Sahel and the southern part of Sahara desert more than the adjacent areas to the north and south, thereby shifting the peak meridional temperature gradient northward. Consequently, an anomalous easterly jet is found north of its climatological location. This anomalous jet is associated with increased cyclonic circulation to the south of its axis, resulting in an anomalous monsoon rain belt in the Sahel.  相似文献   

Addressing human vulnerability to climate change: Toward a ‘no-regrets’ approach   总被引：1，自引：0，他引：1  

Rasmus Heltberg  Paul Bennett Siegel  Steen Lau Jorgensen 《Global Environmental Change》2009,19(1):89-99

This paper presents and applies a conceptual framework to address human vulnerability to climate change. Drawing upon social risk management and asset-based approaches, the conceptual framework provides a unifying lens to examine links between risks, adaptation, and vulnerability. The result is an integrated approach to increase the capacity of society to manage climate risks with a view to reduce the vulnerability of households and maintain or increase the opportunities for sustainable development. We identify ‘no-regrets’ adaptation interventions, meaning actions that generate net social benefits under all future scenarios of climate change and impacts. We also make the case for greater support for community-based adaptation and social protection and propose a research agenda.  相似文献   

The CLIVAR C20C project: skill of simulating Indian monsoon rainfall on interannual to decadal timescales. Does GHG forcing play a role?     

F. Kucharski  A. A. Scaife  J. H. Yoo  C. K. Folland  J. Kinter  J. Knight  D. Fereday  A. M. Fischer  E. K. Jin  J. Kröger  N.-C. Lau  T. Nakaegawa  M. J. Nath  P. Pegion  E. Rozanov  S. Schubert  P. V. Sporyshev  J. Syktus  A. Voldoire  J. H. Yoon  N. Zeng  T. Zhou 《Climate Dynamics》2009,33(5):615-627

The ability of atmospheric general circulation models (AGCMs), that are forced with observed sea surface temperatures (SSTs), to simulate the Indian monsoon rainfall (IMR) variability on interannual to decadal timescales is analyzed in a multimodel intercomparison. The multimodel ensemble has been performed within the CLIVAR International “Climate of the 20th Century” (C20C) Project. This paper is part of a C20C intercomparison of key climate time series. Whereas on the interannual timescale there is modest skill in reproducing the observed IMR variability, on decadal timescale the skill is much larger. It is shown that the decadal IMR variability is largely forced, most likely by tropical sea surface temperatures (SSTs), but as well by extratropical and especially Atlantic Multidecadal Oscillation (AMO) related SSTs. In particular there has been a decrease from the late 1950s to the 1990s that corresponds to a general warming of tropical SSTs. Using a selection of control integrations from the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3), it is shown that the increase of greenhouse gases (GHG) in the twentieth century has not significantly contributed to the observed decadal IMR variability.  相似文献   

Ground-Water Model for a Thick Fresh-Water Lens   总被引：2，自引：0，他引：2  

Clark C. K. Liu  L. Stephen Lau  John F. Mink 《Ground water》1983,21(3):293-300

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