Faculty Profiles - FUJITA, Koji

Papers - FUJITA, Koji

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Estimated impact of black carbon deposition during pre-monsoon season from Nepal Climate Observatory - Pyramid data and snow albedo changes over Himalayan glaciers. Reviewed

Yasunari TJ, Bonasoni P, Laj P, Fujita K, Vuillermoz E, Marinoni A, Cristofanelli P, Duchi R, Tartari G, Lau KM

Atmospheric Chemistry and Physics Vol. 10 page： 6603-6615 2010.7

Language：English Publishing type：Research paper (scientific journal)

The possible minimal range of reduction in snow surface albedo due to dry deposition of black carbon (BC) in the pre-monsoon period (March–May) was estimated as a lower bound together with the estimation of its accuracy, based on atmospheric observations at the Nepal Climate Observatory – Pyramid (NCO-P) sited at 5079 m a.s.l. in the Himalayan region. A total BC deposition rate was estimated as 2.89 μg m-2 day-1 providing a total deposition of 266 μg m-2 for March–May at the site, based on a calculation with a minimal deposition velocity of 1.0×10-4 m s-1 with atmospheric data of equivalent BC concentration. Main BC size at NCO-P site was determined as 103.1–669.8 nm by correlation analyses between equivalent BC concentration and particulate size distributions in the atmosphere. The BC deposition from the size distribution data was also estimated. It was found that 8.7% of the estimated dry deposition corresponds to the estimated BC deposition from equivalent BC concentration data. If all the BC is deposited uniformly on the top 2-cm pure snow, the corresponding BC concentration is 26.0–68.2 μg kg-1, assuming snow density variations of 195–512 kg m-3 of Yala Glacier close to NCO-P site. Such a concentration of BC in snow could result in 2.0–5.2% albedo reductions. By assuming these albedo reductions continue throughout the year, and then applying simple numerical experiments with a glacier mass balance model, we estimated reductions would lead to runoff increases of 70–204 mm of water. This runoff is the equivalent of 11.6–33.9% of the annual discharge of a typical Tibetan glacier. Our estimates of BC concentration in snow surface for pre-monsoon season is comparable to those at similar altitudes in the Himalayan region, where glaciers and perpetual snow regions begin, in the vicinity of NCO-P. Our estimates from only BC are likely to represent a lower bound for snow albedo reductions, because we used

Formation conditions of supraglacial lakes on debris-covered glaciers in the Himalayas. Reviewed

Sakai A, Fujita K

Journal of Glaciology Vol. 56 ( 195 ) page： 177-181 2010.4

Multi-decadal ice-velocity and elevation changes of a monsoonal maritime glacier: Hailuogou glacier, China. Reviewed

Zhang Y, Fujita K, Liu SY, Liu Q, Wang X

Journal of Glaciology Vol. 56 ( 195 ) page： 65-74 2010.4

Language：English Publishing type：Research paper (scientific journal)

Digital elevation models (DEMs) of the ablation area of Hailuogou glacier, China, produced from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data obtained in 2009, differential GPS (DGPS) data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long- and short-term glacier surface elevation change (dh/dt). The mean dh/dt of the ablation area over 43 years (1966-2009) is -1.1 ± 0.4 m a-1. Since 1989 the thinning has accelerated significantly. Ice velocities measured by DGPS at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus, ranging from 41.0 m a-1 approaching the glacier terminus to a maximum of 205.0 m a-1 at the base of an icefall. Our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades. Changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics, which are driven by different factors for different regions and periods.

A shallow ice core re-drilled on the Dunde Ice Cap, western China: recent changes in the Asian high mountains. Reviewed

Takeuchi N, Miyake T, Nakazawa F, Narita H, Fujita K, Sakai A, Nakawo M, Fujii Y, Duan KQ, Yao TD

Environmental Research Letters Vol. 4 page： 045207 2009.12

Language：English Publishing type：Research paper (scientific journal)

A 51 m deep ice core was re-drilled on the Dunde Ice Cap of western China in 2002, 15 years after the previous ice core drilling in 1987. Dating by seasonal variations in δ18O and particle concentration showed that this 51 m deep ice core covered approximately the last 150 years. The stratigraphy and density showed that more than 90% of the ice core was refrozen ice layers, which comprised less than 5% of the annual accumulation in the older core. This indicates that the ice cap had experienced a more intense melting since 1987, possibly due to climate warming in this region. Mean net accumulation since the last drilling (2002–1987) was 176 mm a-1, which was considerably smaller than that obtained from the 1987 core (390 mm a-1, 1987–1963), indicating a significant decrease of net accumulation on the ice cap in the more recent period. The δ18O record showed an increasing trend in the late 19th century and the highest in the 1950s, which is consistent with the previous core findings. However, there has been no significant increase in δ18O during the last two decades, in contrast to the warming trends suggested by the melt features and other climate records. This discrepancy may be due to the modification of δ18O records by melt water runoff, percolation, and refreezing on the ice cap. Results strongly suggest recent significant mass loss of glaciers in the Asian high mountains and serious shortage of water supply for local people in this arid region in the near future.

http://www.iop.org/EJ/abstract/1748-9326/4/4/045207

A snow algal community on the surface and in an ice core of Rikha-Samba Glacier in Western Nepali Himalayas. Reviewed

Takeuchi N, Fujita K, Nakazawa F, Matoba S, Nakawo M, Rana B

Bulletin of Glaciological Research Vol. 27 page： 25-35 2009.12

Recent changes in Imja Glacial Lake and its damming moraine in the Nepal Himalaya revealed by in-situ surveys and multi-temporal ASTER imagery. Reviewed

Fujita K, Sakai A, Nuimura T, Yamaguchi S, Sharma RR

Environmental Research Letters Vol. 4 page： 045205 2009.11

Total solar eclipse over Antarctica on 23 November 2003 and its effects on the atmosphere and snow near the ice sheet surface at Dome Fuji. Reviewed

Kameda T, Fujita K, Sugita O, Hirasawa N, Takahashi S

Journal of Geophysical Research - Atmospheres Vol. 114 page： D18115 2009.9

Language：English Publishing type：Research paper (scientific journal)

The Moon cast a long shadow over Antarctica on 23 November 2003 in a total solar eclipse. The eclipse was observed at Dome Fuji Station, located at the highest point of East Dronning Maud Land, Antarctica, and lasted 1 h 41 min 37 s in a cloudless condition, during which the Sun was completely obscured for 1 min 43 s. This was the first total solar eclipse to be observed in the Antarctic ice sheet. During the eclipse at Dome Fuji, the air temperature at 1.5 m above the snow surface and the subsurface snow temperature decreased by 3.0 K and 1.8 K, respectively. Estimated surface snow temperatures decreased by 4.6 K. Atmospheric pressure and wind direction did not change, but the wind speed possibly decreased by 0.3 m/s with decreasing air temperature; natural variations in wind speed before and after the eclipse made it difficult to identify a true effect of the solar eclipse. Variations of energy components (net shortwave and longwave radiations, sensible and latent heat fluxes, and geothermal heat) during the eclipse were investigated. The total loss of global solar radiation during the eclipse was 0.60 MJ m-2, equaling 1.6% of the total daily global solar radiation. Regional effects of the eclipse due to a reduction of global solar radiation for air temperature and snow temperature ranged from 0.015 to 0.020 K (W m-2)-1. We additionally examined the relation between eclipse obscuration (the fraction of the Sun's surface area occulted by the Moon) and the reduction of global solar radiation from the first to second contacts. The eclipse was also observed from space by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard NASA's Terra and Aqua satellites. The observational results of this study will contribute to detailed model calculations for clarifying the meteorological effects of eclipses.

http://www.agu.org/pubs/crossref/2009/2009JD011886.shtml

Simplification of heat balance calculation and its application to the glacier runoff from the July 1st Glacier in northwest China since the 1930s. Reviewed

Sakai A, Fujita K, Nakawo M, Yao T

Hydrological Processes Vol. 23 ( 4 ) page： 585-596 2009.2

Language：English Publishing type：Research paper (scientific journal)

Since ancient times meltwater from glaciers in mountain zones has been an important water resource in the arid region of northwest China. Meteorological elements for heat balance calculations at the glacier surface were simplified with the aim of simulating discharge fluctuations from the July 1st Glacier over a span of decades. By estimating relative humidity and downward solar radiation from precipitation, heat balance calculations at the glacier can be made using only daily temperature and precipitation, which are easily obtainable. Calculations of daily discharge using the above method during the melting season in 2002 produced a better simulation than those using the conventional positive degree-day (PDD) factor method. (The ablation of glacier during any particular period is assumed to be proportional to the sum of daily mean temperatures above the melting point during that period.)
We calculated the glacier runoff and mass balance at the July 1st Glacier since 1935 from monthly meteorological data taken near the glacier using the above method. We used three patterns of daily temperature and precipitation to estimate daily meteorological data from monthly or annual data. Calculated mass balance using the patterns of air temperature and precipitation in years when the pressure distributions were similar to its long-term average corresponded well with observed data. Our simulation of the glacier runoff since 1935 also showed good results.

http://www3.interscience.wiley.com/journal/121574898/abstract

Effect of precipitation seasonality on climatic sensitivity of glacier mass balance. Reviewed

Fujita K

Earth and Planetary Science Letters Vol. 276 ( 1-2 ) page： 14-19 2008.11

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Numerical calculations are described, aimed at evaluating the influence of precipitation seasonality and seasonality concentration on climatic sensitivity of glacier mass balance. Equilibrium line altitudes (ELAs) are modeled using idealized meteorological variables, and then a warming test (+1 °C) is performed, which revealed that the effects of latitude and the annual precipitation amount are less than those of precipitation seasonality and its concentration. Calculation shows higher sensitivities for the glaciers located in a summer precipitation climate than for those located within a winter-precipitation climate. Difference due to seasonality is enhanced with the seasonality concentration. The present study suggests that the earlier parameterization of glacier mass balance with annual precipitation amount is insufficient to describe the response of glaciers to climate change. Distribution of precipitation seasonality and its concentration suggest that many parts of the world have a summer-precipitation climate but their seasonality concentration is not significant worldwide. On the other hand, an extensive region of Asia and part of the Andes are located in the highly concentrated summer-precipitation climate. This suggests the high sensitivity of glacier mass balance in these regions to climate change.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4TPND5C-1&_user=119029&_coverDate=11/30/2008&_rdoc=3&_fmt=high&_orig=browse&_srch=doc-info(%23toc%235801%232008%23997239998%23701811%23FLA%23display%23Volume)&_cdi=5801&_sort=d&_docanchor=&_ct=25&_acct=C000009318&_version=1&_urlVersion=0&_userid=119029&md5=5e83486055fa5c9d81a457ac60ee1fca

ヒマラヤにおける氷河変動 Invited

藤田耕史

豊田自動織機技報 Vol. 56 page： 78-84 2008.9

Rapid decrease of mass balance observed in the Xiao (Lesser) Dongkemadi Glacier, in the central Tibetan Plateau. Reviewed

Pu J, Yao T, Yang M, Tian L, Wang N, Ageta Y, Fujita K

Hydrological Processes Vol. 22 ( 16 ) page： 2953-2958 2008.7

Language：English Publishing type：Research paper (scientific journal)

The mass balance of the Xiao (Lesser) Dongkemadi Glacier located in the Tanggula Mountains, of the central Qinghai-Tibetan Plateau has been monitored since 1989. The results show that the mass balance of the glacier has recently shown a deficit trend, and that the glacial terminus was also retreating. Positive mass balance of the glacier was dominant during the period 1989-1993, and the accumulated mass balance reached 970 mm. However, negative mass balance of the glacier has occurred since 1994, except for the large positive mass balance year 1997. The mass balance was -701 mm in 1998, an extremely negative glacier mass balance year. The equilibrium line altitude showed a significant increasing trend. The mass balance of the glacier has changed from a significantly positive mass balance to a strongly negative mass balance since 1994. Meteorological data suggest that the rapid decrease in the mass balance is related to summer season warming.

http://www3.interscience.wiley.com/journal/116327612/abstract

Influence of precipitation seasonality on glacier mass balance and its sensitivity to climate change. Reviewed

Fujita K

Annals of Glaciology Vol. 48 page： 88-92 2008.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Numerical calculations are described, aimed at evaluating the influence of precipitation seasonality (summer and winter) on glacier mass balance. First, equilibrium-line altitudes (ELAs) are modeled using idealized meteorological variables. Modeled climatic conditions (summer mean temperature and annual precipitation) at the ELA of glaciers located within a winter accumulation pattern confirm the observational results of earlier studies. However, the ELA of glaciers located within a summer accumulation climate pattern locates in a colder environment than that of glaciers located within a winter accumulation climate pattern. This difference is mainly due to the annual snow accumulation and the surface albedo. A warming test (+1K) reveals higher sensitivities for the glaciers located within a summer accumulation pattern than for the glaciers located within a winter accumulation pattern. In a humid environment, a significant decrease in snow accumulation on the glaciers located within a summer accumulation pattern directly causes higher sensitivities. In an arid environment, on the other hand, the decreased summer snow induces accelerated melting by lowering the surface albedo and thus increasing absorption of solar radiation on the glaciers located within a summer accumulation pattern. Both influences are due to significant differences in summer precipitation. This study shows the importance of precipitation seasonality on the climatic sensitivity of glacier mass balance, which in previous studies has been linked only with annual precipitation.

http://www.ingentaconnect.com/content/igsoc/agl/2008/00000048/00000001/art00013

ドームふじにおける放射観測. Reviewed

平沢尚彦, 藤田耕史

南極資料 Vol. 52 ( 特集号 ) page： 170-181 2008.6

Language：Japanese

第44次南極地域観測隊により,2003年2月1日から2004年1月20日の地上放射観測(短波上向き・下向き,長波上向き・下向き)の結果を報告する.放射計ドームの着霜を回避する目的でファン付き放射計を用いた上向き,下向きの長波放射,及び下向きの短波放射は1997年の観測値と比較的近い値を示し,両年の観測の妥当性を示唆した.しかし,ファンのない放射計を用いた上向き短波放射は,極夜前後の1-2カ月において下向き短波放射を上回るなど,異常値を示している.着霜がこの原因の候補の一つであるが,確かめられない.データの修正については今後の課題とする.また,極夜期の上向き・下向き長波放射について,典型的な地表面放射冷却時期と放射冷却が抑制される時期について,事例を示した.

シーロメータにより観察されたドームふじの雲・降雪の鉛直分布と季節変化. Reviewed

平沢尚彦, 藤田耕史

南極資料 Vol. 52 ( 特集号 ) page： 159-169 2008.6

Language：Japanese

第44次南極地域観測隊のドームふじ基地におけるシーロメータ観測の結果から,雲及び降雪粒子の鉛直プロファイルの季節変化の概要をまとめ,特徴的な鉛直プロファイルを示した.夏季の2003年2月,12月,及び2004年1月には高度1000m以下に明瞭な雲底が検出される場合が比較的多かった.4月から10月には高度3000mから5000m(標高約7000-9000m)層で夏季より高頻度に雲が観測された.極夜期には高度1500m以下の層でストリーク状の降雪が観測され,これまでの研究と比較し議論した.このストリーク状の降雪は地上に近いほど後方散乱係数が大きくなる特徴を示した.

水の酸素・水素安定同位体を用いた地球水循環研究と今後の展望. Reviewed

檜山哲哉, 阿部理, 栗田直幸, 藤田耕史, 池田健一, 橋本重将, 辻村真貴, 山中勤

水文・水資源学会誌 Vol. 21 ( 2 ) page： 158-176 2008.3

Language：Japanese

水の酸素・水素安定同位体（以下，水の安定同位体）を用いた水循環過程に関する重要な研究および最近の研究のレビューを行った．海水の同位体組成（同位体比）に関する知見，同位体大循環モデルを用いた全球スケールの水循環研究，降水形態による同位体比の差異や局域スケールの降水過程に関する研究，流域スケールでの流出過程，植生に関わる蒸発散過程（蒸発と蒸散の分離）の研究をレビューした．加えて，幅広い時間スケールでの気候変動や水循環変動に関する研究として，氷床コアや雪氷コアを利用した古気候・古環境復元とそれらに水の安定同位体を利用した研究についてもレビューした．最後に，水の安定同位体を利用した水循環研究の今後の展望をまとめた．

http://www.jstage.jst.go.jp/article/jjshwr/21/2/21_158/_article/-char/ja/

Performance of ASTER and SRTM DEMs, and their potential for assessing glacier lakes in the Lunana region, Bhutan Himalayas. Reviewed

Fujita K, Suzuki R, Nuimura T, Sakai A

Journal of Glaciology Vol. 54 ( 185 ) page： 220-228 2008.3

七一氷河を巡る

藤田耕史

アジア遊学 Vol. 99 page： 24-27 2007

Surfacewater-groundwater interaction in the Heihe River basin, Northwestern China. Reviewed

Akiyama T, Sakai A, Yamazaki Y, Wang G, Fujita K, Nakawo M, Kubota J, Konagaya Y

Bulletin of Glaciological Research Vol. 24 page： 87-94 2007

Language：English Publishing type：Research paper (scientific journal)

River discharge and groundwater level data were collected in the Heihe River basin, which is the second largest inland river in Northwestern China. The surfacewater-groundwater interaction, particularly in the lower desert reaches, was analyzed with the help of isotope data of water collected from the river. In the non-irrigation period, river water, which originated from the groundwater in the middle oasis reaches, was present throughout the period in the lower desert reaches. During this period, the river water recharged the groundwater not only in the riparian forest region located near the river but also in the desert-riparian fringe region located farther away from the river. In the irrigation period, the river was usually dried up in the lower desert reaches. The river water in the lower reaches appeared just after short-term releases from the middle reaches; the groundwater level in the riparian forest region rose rapidly, but it declined again just after the short-term releases finished. Since the mixing ratio of the short-term released discharge to the groundwater in the desert-riparian fringe region was smaller than that in the riparian forest region, the short-term released discharge did not contribute to the groundwater recharge in the desert-riparian fringe region.

* Spatial distribution of thermal properties on debris-covered glaciers in the Himalayas derived from ASTER data. Reviewed

Suzuki R, Fujita K, Ageta Y

Bulletin of Glaciological Research Vol. 24 page： 13-22 2007

Characteristics and climatic sensitivities of runoff from a cold-type glacier on the Tibetan Plateau. Reviewed

Fujita K, Ohta T, Ageta Y

Hydrological Processes Vol. 21 ( 21 ) page： 2882-2891 2007

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow-ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter.
Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages.

http://www3.interscience.wiley.com/journal/113508995/abstract

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Papers - FUJITA, Koji