研究等業績 - その他 - 河合 隆行
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An integrated modeling approach for estimating monthly global rainfall erosivity
Fenta A.A.
Scientific Reports ( Scientific Reports ) 14 ( 1 ) 2024年12月
Modeling monthly rainfall erosivity is vital to the optimization of measures to control soil erosion. Rain gauge data combined with satellite observations can aid in enhancing rainfall erosivity estimations. Here, we presented a framework which utilized Geographically Weighted Regression approach to model global monthly rainfall erosivity. The framework integrates long-term (2001–2020) mean annual rainfall erosivity estimates from IMERG (Global Precipitation Measurement (GPM) mission’s Integrated Multi-satellitE Retrievals for GPM) with station data from GloREDa (Global Rainfall Erosivity Database, n = 3,286 stations). The merged mean annual rainfall erosivity was disaggregated into mean monthly values based on monthly rainfall erosivity fractions derived from the original IMERG data. Global mean monthly rainfall erosivity was distinctly seasonal; erosivity peaked at ~ 200 MJ mm ha−1 h−1 month−1 in June–August over the Northern Hemisphere and ~ 700 MJ mm ha−1 h−1 month−1 in December–February over the Southern Hemisphere, contributing to over 60% of the annual rainfall erosivity over large areas in each hemisphere. Rainfall erosivity was ~ 4 times higher during the most erosive months than the least erosive months (December–February and June–August in the Northern and Southern Hemisphere, respectively). The latitudinal distributions of monthly and seasonal rainfall erosivity were highly heterogeneous, with the tropics showing the greatest erosivity. The intra-annual variability of monthly rainfall erosivity was particularly high within 10–30° latitude in both hemispheres. The monthly rainfall erosivity maps can be used for improving spatiotemporal modeling of soil erosion and planning of soil conservation measures.
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半乾燥草原地帯における植生を指標とした井戸掘削地点絞り込み手法の開発
尾留川 侑里, 河合 隆行, 坂中 伸也, 土屋 竜太, 高槻 成紀, ツェレンプレブ バトユン, 森永 由紀
日本地理学会発表要旨集 ( 公益社団法人 日本地理学会 ) 2024a ( 0 ) 180 2024年
<p>半乾燥草原地帯で遊牧民が日常的に利用する水資源は地下水である。その地下水資源の現状を把握することは，資源管理の観点から重要である。しかし，現状の地下水探査技術には大型機器が必要であり，経済的にも作業的にも困難である。本研究では植生を指標として， 広大な半乾燥草原地帯の中から浅層地下水や土壌水分の状態を簡易かつ包括的に確認することを目的とする。</p><p> モンゴル国ブルガン県モゴド郡は，亜寒帯湿潤気候と半乾燥草原地帯の両気候帯の中間地域に位置し，植生豊かな地域である。モゴドの中で明らかに地下水が存在する地点に2400 m測線を設けた。測線内には湿潤平地，乾燥平地，ガレ場斜面が含まれており，これらの地形にはそれぞれ特徴的な植生が自生している。</p><p> 調査地には計72種が出現した。バイオマス指数を用いたクラスター分析の結果により28地点を3群に分類した。クラスターA群は乾燥した平坦地が，クラスターB群には湿潤の平坦地が，クラスターC群には斜面が該当する。CART法によって作成した分類樹木では，B群の特徴となる種は<i>Potentilla anserina,</i> <i>Poa attenuata</i>の2種であることが分かった。また，これらの種はA群とC群では出現しない。</p><p> 電気探査の解析結果とクラスター分類を照らし合わせると，湿潤平坦地のB群では，地下水面が地表面付近の浅層に到達している。A群では地表面は乾燥し高比抵抗であるが，深度約10mで連続した地下水面が存在している。これらの結果から，地下水資源へのアクセスを考慮する場合，周囲にB群が確認できるA群を最も優先的に掘削するべき植生指標と判断出来る。</p><p> 以上の結果から，植生を用いて地中の水文環境を推察することに成功した。今後は観測事例を増やし，さらなる推定精度の向上を目指す。</p>
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An integrated framework for improving watershed management planning
Fenta A.A.
Environmental Research ( Environmental Research ) 236 2023年11月
Proper land use and management (LUM) planning is pivotal to curbing land degradation and ensuring sustainable use of limited watershed resources. Despite decades of research and development efforts, land degradation remains a serious environmental problem in many parts of the world. Issues regarding the sustainability of current LUM initiatives are due to poor linkages between the ecological and socio-economic dimensions of LUM decisions, and an integrated framework allowing LUM interventions to be properly planned and implemented is lacking. In this study, we developed an integrated framework to identify, evaluate, and propose LUM alternatives with ecological and socio-economic benefits. The framework comprises six components: (i) identification of land use problems and setting of objectives, (ii) identification of the best-performing land use-based integrated solutions, (iii) formulation of LUM alternatives and modeling of key indicators, (iv) cost-benefit analysis, (v) evaluation of the LUM alternatives with stakeholders engagement, and (vi) communication of the LUM alternatives to relevant stakeholders to obtain institutional and financial support for implementation. To demonstrate the use of this framework, we conducted a case study in the Aba Gerima watershed of the Upper Blue Nile basin in Ethiopia. This study used extensive plot- and watershed-scale observations (2015–2019) obtained under both conventional and improved sustainable land management practices. We analyzed changes in runoff, soil loss, soil organic carbon (SOC) stock, and land productivity of five LUM alternatives as compared to a baseline scenario (existing farming practices). The results showed that the LUM alternatives reduced runoff by 11–71% and soil loss by 66–95%, and SOC stock and watershed-scale land productivity were improved by 36–104% and 48–134%, respectively. Evaluation of LUM alternatives by stakeholders, including land users, policy makers, and researchers, produced divergent results. In particular, land users prioritized implementation of sustainable land management practices without altering existing land uses. The integrated framework developed in this study can serve as a valuable tool for identifying, evaluating, and proposing LUM alternatives and facilitating decision-making in planning and implementation of LUM practices in watersheds experiencing land degradation.
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2021年に鳥取市河原町で一斉開花したクロチクの観察記録
前田 雄一, 小林 幹夫, 一澤 麻子, 河合 隆行, 土屋 竜太, 矢部 浩, 小山 敢
樹木医学研究 ( 樹木医学会 ) 27 ( 2 ) 113 - 114 2023年04月
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Construction of Virtual Reality Space of the Tottori Sand Dunes using UAVs
SAITO Tadaomi, KAWAI Takayuki, OKASHITA Kisumi, INOSAKO Koji
沙漠研究 ( 日本沙漠学会 ) 32 ( S ) 187 - 191 2022年12月
<p>The Tottori Sand Dunes, located along Japan’s Sanin Coast, are a UNESCO Global Geopark and a popular tourist attraction with millions of annual visitors. However, the tourism opportunities offered by them are hampered by such problems as severe meteorological conditions and vast, undulating landscapes. Constructing a virtual reality (VR) space might be one solution to these problems. Recently, a technique that combined unmanned aerial vehicles (UAVs or drones) and structure from motion (SfM) photogrammetry has been attracting attention for generating 3D models. The main objective of this paper is to construct a VR space of the Tottori Sand Dunes using 3D models generated from UAVs. Another objective is to examine optimal photography conditions and model generation conditions to create beautiful but small 3D models for the construction of a VR space. Two types of UAVs were used to acquire the image data. Metashape (Agisoft) was used as the SfM software for data processing. A cross-platform game engine called Unity (Unity Software Inc.) was used to construct the VR spaces. VIVE Cosmos (HTC) was employed as a head-mounted display (HMD) with controllers for the VR system. As the results, the VR space was successfully constructed in Unity using a 3D model generated by a combination of UAV techniques and SfM photogrammetry. The optimal photography and model generation conditions were determined and used to generate beautiful 3D models for the construction of a VR space.</p>
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Yasuda H.
Geofizika ( Geofizika ) 39 ( 1 ) 1 - 20 2022年
In the central dry zone of Myanmar, the mean annual rainfall is less than 1000 mm. Although rainfed agriculture is commonly practiced there, the feasibi?? lity of rainfed farming is compromised by the large fluctuations of rainfall and the frequent occurrence of dry years. The monthly distribution of rainfall follows a bimodal pattern. The intensity of the monsoonal rainfall from May to October is characterized by two peaks, an early peak (May???June) and a late peak ( August??? October), separated by the inter ??monsoon (July). The return times of dry and wet years make management of rainfed agriculture problematic. There is very little correlation between the early and late monsoonal rainfall (r = ???0.257). However, monsoonal rainfall is teleconnected to sea surface temperatures (SSTs) in certain areas of the Pacific Ocean in real time. Furthermore, at lag times of 6???9 months, there are teleconnections between the early monsoonal, inter ??monsoonal, and late monsoonal rainfall and SSTs in certain areas of the Indian Ocean and Atlantic Ocean. We used an Elman artificial neural network model to predict early monsoonal, inter ??monsoonal, and late monsoonal rainfall based on teleconnections with SSTs in the Indian and Atlantic oceans 6???9 months before the rainfall occurred. The correlation coefficient between the predicted and observed rainfall exceeded 0.7 in all three cases.
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UAVを用いた鳥取砂丘のバーチャルリアリティ空間の構築【JST・京大機械翻訳】
SAITO Tadaomi, KAWAI Takayuki, OKASHITA Kisumi, INOSAKO Koji
沙漠研究 32 ( S ) 2022年
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日本の鳥取砂丘の地形変化を監視するためのUAV写真測量の利用
LIU Jiaqi, KIMURA Reiji, WU Jing, KAWAI Takayuki
日本砂丘学会誌 69 ( 1 ) 2022年
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Agroecology-based soil erosion assessment for better conservation planning in Ethiopian river basins
Ayele Almaw Fenta, Atsushi Tsunekawa, Nigussie Haregeweyn, Mitsuru Tsubo, Hiroshi Yasuda, Takayuki Kawai, Kindiye Ebabu, Mulatu Liyew Berihun, Ashebir Sewale Belay, Dagnenet Sultan
ENVIRONMENTAL RESEARCH ( ACADEMIC PRESS INC ELSEVIER SCIENCE ) 195 2021年04月
Soil erosion by water is one of the main environmental concerns in Ethiopia. Several studies have examined this at plot and watershed scales, but no systematic study of soil erosion severity and management solutions at national scale is available. This study investigated soil erosion and the potential of land-cover- and agroecology-specific land management practices in reducing soil loss through employing the Revised Universal Soil Loss Equation and the best available datasets. The mean rate of soil loss by water erosion in Ethiopia was estimated as 16.5 t ha(-1) yr(-1), with an annual gross soil loss of ca. 1.9 x 10(9) t, of which the net soil loss was estimated as ca. 410 x 10(6) t (22% of the gross soil loss). Soil loss varied across land cover types, 15 agroecological zones, and 10 river basins, with the main contributors in the respective analyses being cropland (ca. 23% of Ethiopia; 50% of the soil loss; mean soil loss rate of 36.5 t ha(-1) yr(-1)), Moist Weyna Dega (ca. 10%; 20%; 33.3 t ha(-1) yr(-1)), and the Abay basin (ca. 15%; 30%; 32.8 t ha(-1) yr(-1)). Our results show that ca. 25% of Ethiopia (28 x 10(6) ha) has soil loss rates above 10 t ha(-1) yr(-1), which is higher than the tolerable soil loss limits estimated for Ethiopia. Ex-ante analysis revealed that implementation of land-cover- and agroecology-specific land management practices (level bunds, graded bunds, trenches, and exclosures combined with trenches and/or bunds) in such areas could reduce the mean soil loss rate from 16.5 t ha(-1) yr(-1) to 5.3 t ha(-1) yr(-1) (mean, by ca. 68%; range, 65-70%). Suitable land management practices in the Abay and Tekeze basins and Dega and Weyna Dega agroecologies, which experience particularly severe erosion, would account for ca. 50 and 70% of the estimated soil loss reduction, respectively. This study can help raise awareness among policy makers and land managers of the extent and severity of soil loss by water erosion for better conservation planning in river basins to support sustainable use of land and water resources.
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Ground penetrating radar for soil-water measurement in a semi-arid climate in the Orkhon River basin, central Mongolia
Amarsaikhan Tsogtbaatar, Takayuki Kawai, Motoyuki Sato
EXPLORATION GEOPHYSICS ( TAYLOR & FRANCIS LTD ) 53 ( 2 ) 229 - 236 2021年04月
In this paper, we present a velocity analysis technique using ground-penetrating radar (GPR) data to estimate near-surface soil-water content affected by topography and solar radiation on a mountain peak, mountain mid-slope, and alluvial plain sites in a semi-arid climate area in central Asia. By making precise measurements of reflected EM wave velocity, the water content in the near-surface soil was determined. The GPR experiments at several frequencies were carried out in two sequential phases (comprising common-offset and multi-offset methods) to obtain the soil-water content and illustrate the subsurface structure. We then tried to determine the relationship between near-surface moisture content and permafrost thawing. Therefore, we used several different methods including time-domain reflectometry and a resistivity survey. We also confirmed via the GPR data that vegetation cover indicates soil-water content in the near-surface soil. The results evaluated in this study provide meaningful information about soil water as well as subsurface structures. The GPR data acquired at the survey sites indicated a large range of near-surface water content due to the topography of the survey lines.
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Soil Structure Stability under Different Land Uses in Association with Polyacrylamide Effects
Amrakh I. Mamedov, Atsushi Tsunekawa, Nigussie Haregeweyn, Mitsuru Tsubo, Haruyuki Fujimaki, Takayuki Kawai, Birhanu Kebede, Temesgen Mulualem, Getu Abebe, Anteneh Wubet, Guy J. Levy
SUSTAINABILITY ( MDPI ) 13 ( 3 ) 2021年02月
Soil structural stability is a vital aspect of soil quality and functions, and of maintaining sustainable land management. The objective of this study was to compare the contribution of four long-term land-use systems (crop, bush, grass, and forest) coupled with anionic polyacrylamide (PAM = 0, 25, and 200 mg L-1) application on the structural stability of soils in three watersheds of Ethiopia varying in elevation. Effect of treatments on soil structural stability indices were assessed using the high energy moisture characteristic (HEMC, 0-50 hPa) method, which provides (i) water retention model parameters alpha and n, and (ii) soil structure index (SI). Soil (watershed), land use and PAM treatments had significant effects on the shape of the water retention curves (alpha, n) and SI, with diverse changes in the macropore sizes (60-250; >250 mu m). Soil organic carbon (SOC) content and SI were strongly related to soil pH, CaCO3 soil type-clay mineralogy, exchangeable Ca2+, and Na+ (negatively). The order of soil SI (0.013-0.064 hPa(-1)) and SOC (1.4-8.1%) by land use was similar (forest > grass > bush > cropland). PAM effect on increasing soil SI (1.2-2.0 times), was inversely related to SOC content, being also pronounced in soils from watersheds of low (Vertisol) and medium (Luvisol) elevation, and the cropland soil from high (Acrisol) elevation. Treating cropland soils with a high PAM rate yielded greater SI (0.028-0.042 hPa(-1)) than untreated bush- and grassland soils (0.021-0.033 hPa(-1)). For sustainable management and faster improvement in soil physical quality, soil properties, and land-use history should be considered together with PAM application.
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GNSS受信機を利用した広域土壌水分測定の可能性検討
門田直哉, 齊藤忠臣, 河合隆行, 藤巻晴行, 猪迫耕二, 登尾浩助, 森也寸志
農業農村工学会中国四国支部講演会講演要旨集 75th 2021年
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Cropland expansion outweighs the monetary effect of declining natural vegetation on ecosystem services in sub-Saharan Africa
Ayele Almaw Fenta, Atsushi Tsunekawa, Nigussie Haregeweyn, Mitsuru Tsubo, Hiroshi Yasuda, Katsuyuki Shimizu, Takayuki Kawai, Kindiye Ebabu, Mulatu Liyew Berihun, Dagnenet Sultan, Ashebir Sewale Belay, Jian Sun
ECOSYSTEM SERVICES ( ELSEVIER ) 45 2020年10月
Changes in land cover and land degradation alter natural ecosystems, thereby affecting the services these ecosystems provide. However, there have been few attempts to estimate the effects of land cover change and land degradation on ecosystem services at large spatial scales and under the strong influence of human activities. Here, we used the European Space Agency Climate Change Initiative land cover maps (1992-2015) and the value transfer valuation method to estimate the changes in ecosystem services value (ESV) in response to land cover change in sub-Saharan Africa (SSA). Moreover, we estimated the loss of ESV due to land degradation by using the long-term (1992-2015) trend in the annual normalized difference vegetation index as a proxy for longterm biomass productivity decline. Our results revealed that, between 1992 and 2015, cropland increased by about 20 million ha, largely at the expense of forest and shrubland. The total estimated ESV of SSA was about US $9 trillion year(-1), of which 55% was derived from cropland and deciduous forest, with comparable contributions. Land cover change resulted in a net increase in the total ESV by US$125 billion year(-1) (1992-2015), albeit with an ESV loss of US$60 billion year -1 from the conversion of evergreen forest and shrubland. Overall, cropland expansion accounted for about 60% of the increase in the total ESV (US$125 billion year(-1)), thereby outweighing the decrease in ESV due to the decline in natural vegetation. Land degradation hotspots covered about 5% of SSA, resulting in a total ESV loss of about US$56 billion year(-1), of which nearly 65% was due to the degradation of forests and croplands. Changes in ESV varied across sub-regions, climate zones, and countries, depending on the dominant land cover change and the extent of land degradation. Our results provide useful insights for making informed decisions towards sustainable use and management of ecosystems.
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Electrical Conductivity, pH, Minerals, and Sensory Evaluation of Airag (Fermented Mare's Milk)
Ryouta Tsuchiya, Takayuki Kawai, Tserenpurev Bat-Oyun, Masato Shinoda, Yuki Morinaga
FOODS ( MDPI ) 9 ( 3 ) 2020年03月
Traditional airag (fermented mare's milk) is a sour, slightly alcoholic drink handmade by Mongolian nomads. As airag is not heated after production, the fermentation continues to proceed and the taste changes rapidly. The objective of this study was to investigate the association of the sensory taste evaluation of airag with some properties-electrical conductivity (EC), pH and concentrations of macro minerals (calcium (Ca), phosphorous (P), sulfur (S), magnesium (Mg), potassium (K), and sodium (Na))-of airag. We held an airag contest in Mogod county, one of the most famous airag production areas, in order to collect samples of airag for the analysis of airag properties and to conduct an airag taste evaluation by Mongolian people. The results of the statistical analysis indicated that the EC-value was related to the evaluation score of airag. Except for EC, no statistically significant relationship between the taste score and the other properties was found in this study. It was concluded that the EC-value would be a simple measurement indicator for evaluating the quality of airag on site.
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Land susceptibility to water and wind erosion risks in the East Africa region
Fenta A. A, Tsunekawa A, Haregeweyn N, Poesen J, Tsubo M, Borrelli P, Panagos P, Vanmaercke M, Broeckx J, Yasuda H, Kawai T, Kurosaki Y
Science of The Total Environment ( ELSEVIER ) 703 135016 2020年02月
Land degradation by water and wind erosion is a serious problem worldwide. Despite the significant amount of research on this topic, quantifying these processes at large- or regional-scale remains difficult. Furthermore, very few studies provide integrated assessments of land susceptibility to both water and wind erosion. Therefore, this study investigated the spatial patterns of water and wind erosion risks, first separately and then combined, in the drought-prone region of East Africa using the best available datasets. As to water erosion, we adopted the spatially distributed version of the Revised Universal Soil Loss Equation and compared our estimates with plot-scale measurements and watershed sediment yield (SY) data. The order of magnitude of our soil loss estimates by water erosion is within the range of measured plot-scale data. Moreover, despite the fact that SY integrates different soil erosion and sediment deposition processes within watersheds, we observed a strong correlation of SY with our estimated soil loss rates (r(2) = 0.4). For wind erosion, we developed a wind erosion index by integrating five relevant factors using fuzzy logic technique. We compared this index with estimates of the frequency of dust storms, derived from long-term Sea-Viewing Wide Field-of-View Sensor Level-3 daily data. This comparison revealed an overall accuracy of 70%. According to our estimates, mean annual gross soil loss by water erosion amounts to 4 billion t, with a mean soil loss rate of 6.3 t ha(-1) yr(-1), of which ca. 50% was found to originate in Ethiopia. In terms of land cover, ca. 50% of the soil loss by water erosion originates from crop-land (with a mean soil loss rate of 18.4 t ha(-1) yr(-1)), which covers ca. 15% of the total area in the study region. Model results showed that nearly 10% of the East Africa region is subject to moderate or elevated water erosion risks (>10 t ha(-1) yr(-1)). With respect to wind erosion, we estimated that around 25% of the study area is experiencing moderate or elevated wind erosion risks (equivalent to a frequency of dust storms >45 days yr(-1)), of which Sudan and Somalia (which are dominated by bare/sparse vegetation cover) have the largest share (ca. 90%). In total, an estimated 8 million ha is exposed to moderate or elevated risks of soil erosion by both water and wind. The results of this study provide new insights on the spatial patterns of water and wind erosion risks in East Africa and can be used to prioritize areas where further investigations are needed and where remedial actions should be implemented. (C) 2019 The Author(s). Published by Elsevier B.V.
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GPSのマルチパス信号を利用した土壌水分推定の可能性検討
齊藤忠臣, 足立望, 河合隆行, 藤巻晴行, 猪迫耕二, 登尾浩助, 森也寸志
農業農村工学会大会講演会講演要旨集(CD-ROM) 2020 2020年
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Prediction of summer rainfall over the source region of the Blue Nile by using teleconnections based on sea surface temperatures
Alhamshry Asmaa, Fenta Ayele Almaw, Yasuda Hiroshi, Shimizu Katsuyuki, Kawai Takayuki
THEORETICAL AND APPLIED CLIMATOLOGY 137 ( 3-4 ) 3077 - 3087 2019年08月
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鳥取県におけるモミの分布
前田雄一, 河合隆行, 矢部 浩, 小山 敢, 土屋竜太
樹木医学研究 23 ( 1 ) 40 - 41 2019年01月
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強度の枝打ち後に発生したヒノキ林の立ち枯れ被害
前田雄一, 河合隆行, 土屋竜太, 中村徳和, 小山 敢, 矢部 浩
樹木医学研究 23 ( 1 ) 14 - 21 2019年
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Evaluation of satellite rainfall estimates over the Lake Tana basin at the source region of the Blue Nile River
Ayele Almaw Fenta, Hiroshi Yasuda, Katsuyuki Shimizu, Yasuomi Ibaraki, Nigussie Haregeweyn, Takayuki Kawai, Ashebir Sewale Belay, Dagnenet Sultan, Kindiye Ebabu
Atmospheric Research ( Elsevier Ltd ) 212 43 - 53 2018年11月
Satellite rainfall estimates (SREs) have become alternative sources of rainfall data for several applications. However, the accuracy of the SREs is likely to vary from region to region and must be evaluated on a local basis. This study evaluated the accuracy of three SREs for the Lake Tana basin in northwestern Ethiopia. This basin is characterized by complex topography comprising both lowlands and highlands. The three SREs were the Tropical Applications of Meteorology using SATellite data and ground-based observations (TAMSAT), the Climate Hazard Infrared Precipitation with Stations (CHIRPS), and the Africa Rainfall Climatology (ARC). The SREs were compared with gauge measurements in lowland and highland regions during the period 1995–2010 on a point-to-pixel basis at daily, dekadal (10 days), monthly, and seasonal periodicities. The results show that the three SREs underestimated rainy events, but TAMSAT captured rainfall occurrence relatively well in both regions. ARC better estimated light rain rates (1–5 mm d−1) than did TAMSAT and CHIRPS
however, all the SREs markedly underestimated moderate and heavier rain rates (≥10 mm d−1). TAMSAT and CHIRPS estimated the amount of rainfall reasonably well (high efficiency, low random errors, and bias <
10%) at daily, dekadal, and monthly time scales, whereas ARC did not perform satisfactorily (high random errors, low efficiency, and bias >
20%) at any time scale. On a seasonal scale, CHIRPS estimated the secondary rainy season (March–May) rainfall better than did ARC and TAMSAT, whereas TAMSAT outperformed both CHIRPS and ARC during the primary rainy season (June–September). Overall, the rainfall detection capabilities and rainfall amount estimates of the SREs were better over the lowlands, and the cumulative rainfall estimates tended to improve with increasing integration time (i.e., from daily to seasonal totals). -
Teleconnection of rainfall time series in the central Nile Basin with sea surface temperature
Yasuda H, S. N, Pandaa, Mohamed, A. M. Abd Elbasitc, T. Kawai, T. Elgamrie, A. A. Fenta, H. Nawata
Paddy and Water Environment 16 805 - 821 2018年08月
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都市部の人を森林へ誘うための試み
前田雄一, 矢部 浩, 小山 敢, 中村徳和, 河合隆行, 土屋竜太
樹木医学研究 22 ( 2 ) 113 - 114 2018年04月
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Spatial distribution and temporal trends of rainfall and erosivity in the Eastern Africa region
Ayele Almaw Fenta, Hiroshi Yasuda, Katsuyuki Shimizu, Nigussie Haregeweyn, Takayuki Kawai, Dagnenet Sultan, Kindiye Ebabu, Ashebir Sewale Belay
HYDROLOGICAL PROCESSES ( WILEY ) 31 ( 25 ) 4555 - 4567 2017年12月
Soil erosion by water is one of the main environmental concerns in the drought-prone Eastern Africa region. Understanding factors such as rainfall and erosivity is therefore of utmost importance for soil erosion risk assessment and soil and water conservation planning. In this study, we evaluated the spatial distribution and temporal trends of rainfall and erosivity for the Eastern Africa region during the period 1981-2016. The precipitation concentration index, seasonality index, and modified Fournier index have been analysed using 5x5-km resolution multisource rainfall product (Climate Hazards Group InfraRed Precipitation with Stations). The mean annual rainfall of the region was 810mm ranging from less than 300mm in the lowland areas to over 1,200mm in the highlands being influenced by orography of the Eastern Africa region. The precipitation concentration index and seasonality index revealed a spatial pattern of rainfall seasonality dependent on latitude, with a more pronounced seasonality as we go far from the equator. The modified Fournier index showed high spatial variability with about 55% of the region subject to high to very high rainfall erosivity. The mean annual R-factor in the study region was calculated at 3,246 +/- 1,895MJ mm ha(-1)h(-1)yr(-1), implying a potentially high water erosion risk in the region. Moreover, both increasing and decreasing trends of annual rainfall and erosivity were observed but spatial variability of these trends was high. This study offers useful information for better soil erosion prediction as well as can support policy development to achieve sustainable regional environmental planning and management of soil and water resources.
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強度の枝打ち後に発生したヒノキ林の立ち枯れ被害_速報
前田雄一, 河合隆行, 土屋竜太, 中村徳和, 矢部 浩, 小山 敢
樹木医学研究 21 ( 1 ) 20 - 21 2017年04月
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広葉樹緑化木に発生していた日焼け被害
前田雄一, 河合隆行, 土屋竜太, 小山 敢, 矢部 浩
樹木医学研究 20 ( 3 ) 138 2017年01月
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The effects of ocean SST dipole on Mongolian summer rainfall
Hiroshi Yasuda, Banzragch Nandintsetseg, Ronny Berndtsson, Ganbat Amgalan, Masato Shinoda, Takayuki Kawai
GEOFIZIKA ( UNIV ZAGREB , ANDRIJA MOHOROVICIC GEOPHYS INST ) 34 ( 1 ) 199 - 218 2017年
Cross-correlations between inter-annual summer rainfall time series (June to August: JJA) for arid Mongolia and global sea surface temperatures (GSST) were calculated for prediction purposes. Prediction of summer rainfall for four vegetation zones, Desert Steppe (DS), Steppe (ST), Forest Steppe (FS), and High Mountain (HM) using GSSTs for time lags of 5, 6, and 7 months prior to JJA rainfall was evaluated. Mongolian summer rainfall is correlated with global SSTs. In particular, the summer rainfall of FS and HM displayed high and statistically significant correlations with SST in specific parts of the oceans. SST dipoles (pairs of positively and negatively correlated areas) were identified, and correlation for time series of the SST differences between SST dipoles (positive - negative) with the summer rainfall time series was larger than the original correlations. To predict the summer rainfall from SST, an artificial neural network (ANN) model was used. Time series of the SST difference that represents the strength of the dipole were used as input to the ANN model, and Mongolian summer rainfall was predicted 5, 6, and 7 months ahead in time. The predicted summer rainfall compared reasonably well with the observed rainfall in the four different vegetation zones. This implies that the model can be used to predict summer rainfall for the four main Mongolian vegetation zones with good accuracy.