埼玉大学 研究機構テニュアトラック 第４回シンポジウム

埼玉大学 環境科学研究センター 後援

Climate Change and its Impacts on Coastal Environment and Water Resources

（気候変動と、その沿岸環境及び水資源への影響）

日時/ 201５年５月28日（木）、13：00～17：20

場所/ 埼玉大学理工学研究科 総合研究棟１F　シアター教室

概要：海岸は、古来より重要な生活・生産・レクリエーションの場です。沿岸地域は、海の幸に恵まれ、また交通・運輸の要衝でもあります。このように海岸は、社会生活の重要な拠点となり、人間社会を潤す環境保全にも重要な役目を担っていますが、また一方、冷酷なまでに、自然が猛威をふるう場でもあります。東日本大地震の津波被害は、生々しい記憶として今なお脳裏に焼き付いています。

地球温暖化現象は、ご存じの通り現代社会の抱える喫緊の問題ですが、産業革命以降の主に二酸化炭素の増加といった人的影響で引き起こされる地球規模での気候変動をいいます。この問題は、海岸環境科学・工学とも深く関わっています。

例えば、地球温暖化による海面水位の上昇は、人間生活の場に関わる問題の一つであり、特に、沿岸部に低湿地帯をもつ国々にとっては、国自体の存亡をも左右する深刻な問題です。サンゴ礁でできた島々からなります南太平洋上のツバルでは、海面上昇による島の水没・消滅が現実問題として危惧されていて、地球温暖化によるものではないかと懸念されています。

さらに温暖化は、気温や海面水位の上昇に加え、水循環の変化を通じて、人間社会にも甚大な影響を及ぼすことが考えられます。例えば、経済的発展に呼応した水需要は、益々増大の一途にあります。現在、世界各地で水不足が伝えられていますが、それが気候変動に伴っているとの確証はありません。しかし今後、地球温暖化による降水量の変化に呼応して、高緯度地域では水資源賦存量が増加するのに対し、亜熱帯乾燥帯のほぼ全域で減少すると推計されています。すでに水需給が逼迫している地域では、さらに深刻な事態に陥るのではないかと懸念されています。また、海面水位の上昇は、特に下流域の海岸沿いの低地帯にあっては、表流水や沿岸地下水への塩水遡上を誘起し、塩水浸入のポテンシャルを増大させるため、水資源利用の現状さえ維持できなくなる可能性が指摘されています。

以上の背景を踏まえ、本シンポジウムでは、地球温暖化に伴う海面水位の上昇の影響に関する科学・工学の知見を展望し、また、東南アジア（ベトナム）とアフリカ（エジプト）における水資源管理問題や現状が紹介されました。

参加者31名のこぢんまりとしたシンポジウムでしたが、討論も活発であり、今後の研究の連携・推進に繋がるものとして、当初の企画の趣旨をある程度実現できたものと考えられます。シンポジウムは、本学教授の田中規夫（レジリエント社会研究センター長）の歓迎の挨拶に始まり、以下の6件の研究発表がありました。

 

Regional relative sea-level rise and uncertainty

Han Soo Lee^{(1), (2)}

(1) Graduate School of Science and Engineering, Saitama University, Saitama 338-8571, Japan (Email: hslee@mail.saitama-u.ac.jp)

(2) International Institute for Resilient Society, Saitama University

Abstract：Future sea-level rise (SLR) in and around the Seto Inland Sea (SIS), Japan, is estimated in 2050 and 2100 using ensemble empirical mode decomposition (EEMD) and long-term sea-level records. Ensemble empirical mode decomposition, an adaptive data analysis method, can separate sea-level records into intrinsic mode functions (IMFs) from high to low frequencies and a residual. The residual is considered a non-linear trend in the sea-level records. The mean SLR trend at Tokuyama in the SIS from EEMD is 3.00 mm/yr from 1993 to 2010, which is slightly lower than the recent altimetry-based global rate of 3.3 ± 0.4 mm/yr during the same period. Uncertainty in SLR is estimated by considering inter-decadal variations in the sea levels. The resulting SLR in 2050 and 2100 for Tokuyama is 0.19 ± 0.06 m and 0.56 ± 0.18 m, respectively. The stations facing the Pacific illustrate a greater and more rapid SLR in 2100 compared with other stations in the SIS. The SLR is caused not only by mass and volume changes in the sea water but also by other factors, such as local subsidence, tectonic motion, and river discharge. The non-linear trend of SLR, which is the residual from EEMD, is interpreted as the sum of the local factors that contribute to the sea-level budget.

In this symposium, more enphasis will be made on the methodology for analysing the sea level records and uncertainty involved in SLR projection.

Keywords: sea-level rise; ensemble empirical mode decomposition; the Seto Inland Sea; trend and detrending; local subsidence

 

Detecting anthropogenic footprints in sea level rise

Sönke Dangendorf ⁽¹⁾, Marta Marcos ⁽²⁾, Alfred Müller ⁽³⁾, Eduardo Zorita ⁽⁴⁾,

Riccardo Riva ⁽⁵⁾, Erik Berk ⁽³⁾, and Jürgen Jensen ⁽¹⁾

Research Institute for Water and Environment (fwu), University of Siegen, Paul-Bonatz-Str. 9-11, 57076 Siegen, Germany, phone +49 (271) 740 2518, (Email: soenke.dangendorf@uni-siegen.de)

1. IMEDEA (UIB-CSIC), Miquel Marquès, 21,E-07190, Esporles, Mallorca, Spain
2. Department of Mathematics, University of Siegen, Germany
3. Helmholtz-Centre Geesthacht, Germany
4. Technical University Delft, Netherlands

Abstract：While there is scientific consensus that global mean sea level (MSL) is rising since the late 19^th century, it remains unclear how much of this rise is due to natural variability or anthropogenic forcing. Uncovering the anthropogenic contribution requires profound knowledge about the persistence of natural MSL variations. This is challenging, since observational time series represent the superposition of various processes with different spectral properties. Here we statistically estimate the upper bounds of naturally forced centennial MSL trends on the basis of two separate components: a slowly varying volumetric (mass and density changes) and a more rapidly changing atmospheric component. Resting on a combination of spectral analyses of tide gauge records, ocean reanalysis data and numerical Monte-Carlo experiments, we find that in records where transient atmospheric processes dominate, the persistence of natural volumetric changes is underestimated. If each component is assessed separately, natural centennial trends are locally up to 1 mm/yr larger than in case of an integrated assessment. This implies that external trends in regional MSL rise related to anthropogenic forcing might be generally overestimated. By applying our approach to a spatially homogeneous centennial ocean reanalysis (SODA) in combination with fingerprints of glacial and Greenland ice melt and hydrology changes, we estimate maximum natural trends in the order of 1 mm/yr for the global average. This value is larger than previous estimates, but consistent with recent paleo evidence from periods in which the anthropogenic contribution was absent. Comparing our estimate to the available reconstructions of 20th century global MSL rise of 1.3-2.0 mm/yr suggests a minimum external contribution of at least 0.3 mm/yr. We conclude that an accurate detection of anthropogenic footprints in global and regional MSL rise requires a more careful assessment of the persistence of intrinsic natural variability.

References:

Dangendorf, S., D. Rybski, C. Mudersbach, A. Müller, E. Kaufmann, E. Zorita, and J. Jensen (2014), Evidence for long-term memory in sea level, Geophys. Res. Lett., 41, 5564–5571, doi:10.1002/2014GL060538.

Dangendorf, S., M. Marcos, A. Müller, E. Zorita, R.E.M. Riva, E. Berk, and J. Jensen (revised), Detecting anthropogenic footprints in sea level rise, Nature Communications.

 

 Impacts of Climate Oscillation on Water Resources and Regional Disasters

 Takao Yamashita

Graduate School for International Development and Cooperation, Hiroshima University, Higashi-Hiroshima, Japan (Email: tkoyamashita@hiroshima-u.ac.jp)

Abstract：　Factors of climate change can be classified into three.

1) Factors by human activities: the use of fossil fuels, deforestation, land use and land cover change, GHG emission by peat land development, etc., aerosol emission

2) External factors of the climate system: changes in solar activity (solar wind, shortwave radiation, solar magnetic field) and large-scale volcanic eruption

3) Internal climate oscillation: the natural internal variability of the climate system. Weather disturbances such as meandering of westerlies jet stream, typhoons, Niño southern oscillation (ENSO), the Arctic Oscillation (AO) etc.

When we consider the impacts of climate change on local environment, disaster prevention measures, it is important to understand the both 1), 2) global climate change and 3) internal climate oscillation. Unfortunately the effects of climate oscillation are not well incorporated in GCM (General Circulation Model).

In this presentation, the following impacts of climate oscillation will be addressed.

・If you think about the medium- to long-term disaster prevention measures, it is important to understand the relationship between extreme weather and climate oscillations focusing on meandering of westerlies and Arctic Oscillation (AO) , which are related to the ocean oscillation and teleconnection.

・When AO is negative, weakened westerlies start meandering⇒ cold flows intrusion into the mid-latitude region⇒ weather becomes unstable⇒ occurrence of tornadoes increases, number of landing typhoon to Japan decrease. In this case, the global mean temperature will be colder.

・In the case of the positive AO, the westerlies become strongly stable⇒ chills is confined to the Arctic Ocean resulting in stable weather in the mid-latitude region⇒ increase of landing typhoon to Japan, the number of occurrence of tornadoe decreases, intensity of tornado and landing typhoon conversely become strong due to warming temperature (in this case, the global mean temperature will be warmer).

・How we can make use of the output of MIROC4h and CESM-BGC in CMIP5 (Coupled Model Intercomparison Program 5) to the near future prediction of changes in water resources and disasters with consideration of climate oscillation.

 

Hydro-Climate Projections in the CORDEX MENA Domain  with Focus on the Eastern Nile Basin

Mohammed Haggag

Department of Irrigation and Hydraulics, Faculty of Engineering, Cairo University, Giza, Egypt (Email: mohammed.abou-elhaggag@dargroup.com )

Abstract：The Nile Basin covers roughly 10% of the African continent, and is home to 18% of the African population. Several Nile Basin states are among the world’s poorest countries and struggle with multiple development challenges such as famine, unemployment, and frequent violent conflicts at a local or regional level. Nile’s waters flow across very different climatic regions, transboundary water management challenges with 224 million people and 11 countries sharing its water. Due to climate change and climate variability, the amount of water in the Nile Basin may fluctuate and it can be safely assumed that water availability will not increase.

In order to assess the future climate change impacts on the water resources in the Eastern Nile Basin, we contributed toward the development of a clear understanding of the current basin climate and the current hydrological behaviour and the interactions that take place between the two systems prior to future projections can be made. This is viable through carrying out simulation of the climate/hydrology systems in the basin using numerical modelling techniques.

In order to capture finer and more accurate details of the climate pattern it is necessary to downscale Global Circulation Models (GCMs) outputs using Regional Climate Models (RCMs). The RCM physics schemes shall be tuned so that it best reflects the dynamics and physics of the region of interest. The main objective of this study is to suggest a configuration of the regional climate model over the Eastern Nile Basin and to identify its skill in reproducing the historical/present climate patterns prior to being employed to study the impacts of future climate change scenarios. The climate version of the Weather, Research and Forecasting Model (WRF) model is selected for this study due to its increasing use with large community of modelers. However, the suggested framework which could be applied to any model and ideally in the future would be part of an ensemble of models focused on the region.

The study area covers a domain over the Middle East and North Africa region (MENA) with with high resolution nest centered on the Eastern Nile basin. This domain is selected such that we contribute to the ongoing Coordinated Regional Climate Downscaling Experiment in the MENA region as well (MENA-CORDEX). Basically, the RCM is forced with lateral boundary conditions based on the European Centre for Medium-range Weather Forecasting (ECMWF) gridded reanalyzes (ERA-Interim is available to us from 1979-present). The analysis of the model results is based on assessing the model performance in simulating the precipitation and air temperature over the high resolution domain over the Eastern Nile. The simulations are compared to available observational datasets. This includes the CRU and UDE, the GPCP dataset and the TRMM (Tropical Rainfall Measuring Mission.

The configured RCM is used to dynamically downscale the ERA-Interim historical reanalysis data (1979-2010) over the study area. Annual and seasonal climatology for precipitation and temperature showed reasonable accuracy compared to gridded observation datasets. The next step will be to employ the configured RCM to downscale the climate projections to assess the added value of regional climate modeling as well as the expected shift in precipitation and temperature patterns and their impacts on the basin hydrology.

 

A Proposed Framework for Integrated Water Management  in the Thua Thien-Hue Province, Central Vietnam

Cong V. Mai

THuy loi University (WAter resource university), 175 Tay Son, Dong Da, Hanoi, Vietnam (Email: maivancong@wru.vn)

Abstract：The Thua Thien-Hue province is located in the center of Vietnam. It is characterized by the short distance between the mountains in the west and the coast of the South China Sea in the east. Two large rivers flow through the province, fed by multiple smaller rivers from the mountains. The coastal zone of the Thua Thien-Hue province has a lot of water related problems. Tackling these problems requires an integrated approach that considers all problems, functions and stakeholders. This paper will aim to apply a Framework for Integrated Water Management to the Thua Thien-Hue province to minimize the water related problems in the future, with a primary concern towards flood protection.

This framework assigns different return periods for flooding per area. A map is created that indicates the desired chance on flooding throughout the coastal and flood prone area of the Thua Thien-Hue province. Using a SOBEK 2D model, the flooding can be simulated. The results from this model show that the amount of water that enters the area is too large to apply traditional protection by raising dikes. Also, most houses are built near the riverbanks, making the implementation of dikes problematic. Two possible solutions were considered. The first, consisting of two bypasses, showed unrealistic as the capacity of the second bypass was insufficient. The second scenario, called “Lake Hue”, uses a reservoir as a retention area during extreme events. A dam regulates the discharge towards Hue City while a spillway towards an area with a lower population density takes care of excess water.

Keywords: inundation map; flood protection; flood management; system design; SOBEK; Huong River;

 

Assessment of real-time Predictions and numerical simulation using WRF for Typhoon Neoguri (201408)

Kyeong Ok Kim^(1)*, Young Ho Kim⁽¹⁾, Kyung Tae Jung⁽¹⁾, and Sok Kuh Kang⁽¹⁾

(1) Marine Environments & Conservation Research Division, Korea Institute of Ocean Science & Technology, Ansan, 426-744, Korea. (*Email: kokim@kiost.ac)

Abstract： The real-time predictions for typhoon track and strength are distributed in variable agencies. The real-time prediction data from KMA, RSMC and JTWC were compared the accuracy with the adjusted best-track data from Digital Typhoon (RSMC). The prediction periods are also variable and irregular from 3 days to 5 days. The sequential prediction data are summarized with 6 hour interval from 4^th to 11^th July 2014 for the typhoon Neoguri (201408). The JTWC prediction of the typhoon track and the RSMC predictions of the maximum wind speed and the center pressure show the best predictions. Also the numerical simulation using WRF model forced NCEP GFS prediction data is compared. The errors on the track are shown similarly the differences of 100 km in 48 hour prediction and 200 km in 72 hour prediction. The better results on the track prediction are shown in WRF model. However the large errors on the maximum wind speed and the center pressure of WRF prediction near initial are shown. It is caused by instability in the numerical simulation, and can be improve by introducing the dynamic initialization (DI) method. The WRF prediction of the center pressure shows the best accuracy than the prediction agencies, and the WRF prediction of the maximum wind speed shows the similar accuracy of RSMC prediction.

■ シンポジウム｢Climate Change and its Impacts on Coastal Environment and Water Resources( 気候変動と、その沿岸環境及び水資源への影響 )｣の開催要項･概要については  こちら

■ シンポジウムの様子は  こちら