Warm events, periods when rising surface air temperatures can trigger surface melt, have been recorded during the austral summer at Syowa station on the East Antarctic coast. This study identifies air masses responsible for summer warm events at Syowa. Air masses arriving at Syowa are classified into marine and glacial sources based on their isotopic characteristics. Warm events are not associated with moist marine air intrusion, but with the downward flow of dry glacial air along the west side slope of the mountains in Enderby Land (EL). We use simulations from the Antarctic Mesoscale Prediction System (AMPS) to explore the atmospheric process responsible for the warmest event at Syowa. The model output illustrates several foehn-associated features such as low-level blocking, precipitation on the mountain's windward side, and mountain wave activity, with warm air ascending on the upstream slope and descending to Syowa. The foehn warming is caused by an easterly cross-mountain flow associated with a low-pressure system to the north of the EL coast. Future changes in synoptic cyclonic activity off the EL coast may have a significant impact on the frequency and intensity of foehn events at Syowa and the associated coastal warm events.

抄録全体を表示

 Cloud fractions were observed during research cruises onboard the research vessel (R/V) Shirase between Japan and

using a whole-sky camera and a ceilometer. The cruises, Japanese Antarctic Research Expeditions (JARE) 55 and 56, took place from November 2013 to April 2014 and from November 2014 to April 2015, respectively. Cloud fractions were estimated from the whole-sky camera based on the sky brightness and spectral characteristics, and the ceilometer recorded the cloud occurrence frequency. According to the comparison of daily-averaged cloud fractions from the whole-sky camera with the ceilometer observations over the open ocean between Japan and , the correlation coefficients were 0.87 and 0.93 for JARE 55 and 56, respectively. Overall, the results from both observation methods were consistent over the open ocean. Nevertheless, it was necessary to take surface conditions into consideration, particularly for the estimated cloud fractions from the whole-sky camera, because the contrast in brightness and spectral properties between cloudy and clear skies was lower over the sea ice region, owing to the higher surface albedo. Hence, the classification parameter was expressed as a function of sun elevation over the sea ice region in this study. This parameter was determined from part of the data over the sea ice region during JARE 55 and then applied to JARE 56 as well as to the remaining data from JARE 55. As a result, the daily-averaged cloud fractions over the sea ice region were approximately 84 % and 57 % from JARE 55 and 56, respectively. The daily-averaged cloud fractions estimated from the whole-sky camera were also consistent with the ceilometer observations, where the correlation coefficients with the sea ice region were 0.93 and 0.96 for JARE 55 and 56, respectively.

抄録全体を表示

Studies on ice cores drilled in Antarctic, Greenland and Canadian Arctic ice caps provide the environmental composition and the in the past. This information and further study will help in the understanding of the basic natural processes and the extent of human impact on the environment and . This will eventually enable us to predict the future of the environment. This review summarizes the state of the art methodologies used in ice core studies, with highlights on the recent studies in this group.

抄録全体を表示

The extreme conditions and the sparse number of research stations in limit the number of meteorological records over this area. Satellite radiometric measurements and ground-based GPS measurements can therefore improve the amount of available water vapour information. Combining the Zenith Total Delay (ZTD) time series from 6 Antarctic GPS stations and surface meteorological data, we have determined Precipitable Water Vapour (PW) variations with a 2-hour temporal resolution for a period of 5 years. Data from the Advanced Microwave Sounding Unit (AMSU-B) on board the NOAA-15 satellite cover most parts of but with observations limited to merely few times a day. GPS and AMSU-B data sets are therefore complementary with respect to time and space.
We present a cross validation between PW results from the two independent retrieval algorithms using one year data. Additionally, we compare the observed PW from AMSU-B and GPS with the National Centre for Environmental Prediction (NCEP) reanalysis. All three data sets are highly correlated. The mean differences between the three data sets are station dependent and vary from -1.7 to +1.2 mm. A large part of the bias may result from pressure uncertainties affecting the GPS PW estimates. GPS and AMSU-B as independent data sources are confirmed to be accurate methods for PW estimation for the dry Antarctic atmosphere. PW results from the NCEP analysis corresponds, in general, well to the PW observations at the investigated stations along the Antarctic coast. The results obtained at the station O’Higgins differ from those of the other station. O’Higgins is located at the Antarctic Peninsula and has a more humid environment than the coast of the main Antarctic continent, which may explain the peculiar behaviour of this station.

抄録全体を表示

The accumulation rate, aerosol flux, and air temperature fluctuation can be determined from the study of ice cores drilled through ice sheets and glaciers. The aerosol which gives and environmental information is accumulated on the surface of ice sheet. In order to elucidate the and environmental changes, it is necessary to find the changes in concentration, composition, and isotope ratio of impurities in accumulated particles after the deposition on the snow surface. This study revealed that the global and environmental changes have occurred on various time scales in the past million years. The characteristics of aerosol particles deposited on the Antarctic ice sheet are investigated. Furthermore, the history of solar activity and associated geomagnetic fields is clarified by analyzing the cosmogenic nuclides in ice cores. An interdisciplinary study on ice cores is also carried out to elucidate the evolution mechanisms of microorganisms in the ice cores.

抄録全体を表示

 High quality wave data in data-scarce regions are required in order to provide a reliable source for wave assessment. In this study, numerical modeling was utilized in order to generate the wave characteristics in the Indian Ocean (IO) region using super-high-resolution wind field MRI-AGCM3.2S as forcing. The model was evaluated in comparison to the satellite data and the validated model was performed to simulate historical and future projections of the wave in the study area (25 years for each period). Comparison of mean annuals of the wave indicated a slight decrease of significant wave height (SWH) in the Northern Indian Ocean (NIO) and middle parts of the Southern Indian Ocean (SIO) while there is a considerable increase near the southern ocean adjacent to . The change of mean wave period (T_m01) will be less in the future, however, there will be a considerable increase in the south of India. The results of this study indicate the different patterns of change for wind and wave parameters in different regions of the IO.

抄録全体を表示

Light absorbing carbonaceous particles in the atmosphere (i.e. black carbon and soot) have been of great interest from the view point of radiation budget and impact. Air quality including the carbonaceous particles is much different between Arctic and . Because of large human activity in the Northern hemisphere (even in the Arctic Circle), many anthropogenic species are believed to be transported into the Arctic. In contrast, is isolated from other continents and human activity. In this paper, we discuss the seasonal variation, the inter-annual variation, and the transport processes of absorbing carbonaceous particles in Arctic and .

抄録全体を表示

Sea-level rise is a major effect of change. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. There are questions associated with sea-level rise which science needs to answer. To what extent did change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. Then the impacts are examined along with other consequences of change, from both global and Japanese perspectives. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society.

(Communicated by Kiyoshi HORIKAWA, M.J.A.)

抄録全体を表示

衛星データを使ってグローバルな気候研究を進める上で、極域の正確な雲分布を求めることは焦眉の課題である。極域では地表面が雪や氷におおわれ、アルベードが高く、地表面温度が低く、単一の可視や赤外のデータから雲を検知することは大変難しいためである。本研究では、AVHRRのスプリット・ウインドウ・データを使って雲の識別を行った.11μm(チャンネル4)と12μm(チャンネル5)チャンネルの輝度温度差は薄い雲の指標として有効である。輝度温度差と輝度温度自身との相関をも使うことで、さらに厚い雲も検知可能となった。求めた雲量は、地上で測定された全天カメラによる雲量とうまく対応付けられた。こうした雲解析を、昭和基地にて受信・処理された1987年1月から1988年1月までの13ヶ月分のNOAA-9の毎日のデータについて行った。
東南極大陸上の雲の地域・時間分布特性が得られた。年平均雲量は場所によって異なり、50%から10%以下の場所まで広がり、沿岸近くで大きく内陸で小さくなった。内陸では、さらに、東向き斜面より、ウエッデル海に面した西向き斜面で雲量は多めであった。擾乱の振る舞いに関連して、多くの場所で雲量の半年周期変動が見られた。7月から9月に内陸の雲量は増加し、11月から1月にかけて多くの場所で雲量は増加した。しかし、沿岸ではあまり変動は見られなかった。解析領域は、地形の関係で3つの異なった変動特性を持つ領域に分けられた。多くの場所で、雲量の7日から15日周期振動が顕著に見られた。晴天域と曇天域の輝度温度を比較して、大気上端の雲の放射効果は、冬の内陸で負の値(冷却)、夏は全域で長波長では正の値(加熱)となった。

抄録全体を表示

垂直レーダーとマイクロ波放射計を用いて気柱中の雲水量と氷水量の観測を1989年に南極昭和基地で行った。その結果、雲水量の多い雲(>40mg/cm²)は秋に、雲水量の少ない雲(<20mg/cm²)は冬から早春に多く見られた。雲水量の多い雲の頻度は、昭和基地の気温より海氷域の面積の季節変化によく対応していた。南極外洋から大陸に近づく間に海氷上で雲水の氷化が進むと考えられる。雲水量の多い雲は少ない雲に比べ海岸から50km以内に多くの降水をもたらした。この海岸付近の降水の増加は、大陸斜面上の地形効果による降水の増加と考えられる。

抄録全体を表示

Future changes in extremes indices on precipitation were projected with a 20-km horizontal grid atmospheric general circulation model. At the end of the 21st Century, heavy precipitation was shown to increase enormously in South Asia, the Amazon, and West Africa, while a dry spell was shown to increase in South Africa, south Australia, and the Amazon, suggesting that the risk of water-related disasters will be higher in these regions. In the Asian monsoon region, heavy precipitation increases notably in Bangladesh and in the Yangtze River basin due to the intensified convergence of water vapor flux in summer. In the Amazon, a dry spell greatly increases due to a reduction in the Walker circulation caused by an El Niño-like change in SST prescribed as boundary condition.

抄録全体を表示

The direct and indirect radiative effects of aerosol particles and clouds have been identified as key uncertainties in the prediction of future global . In order to improve knowledge on aerosol and cloud properties, as well as their impact on in the Polar Regions, many observations have been carried out. This paper reviews the direct and indirect radiative forcing of tropospheric aerosols based on the field observations in the Polar Regions.

抄録全体を表示

世界の都市域に関する主要な4つの先行研究（コロンビア大学（GRUMP），世界食糧農業機関，ボストン大学（MOD12），世界銀行）の成果と，気候変動に関する政府間パネル（IPCC）の「排出シナリオに関する特別報告書（SRES）」の3つの社会・経済シナリオを用いて，世界185カ国を対象に2100年までの都市面積の予測を行った。さらに，非都市域における将来の都市化のポテンシャルが，現在のその地域の人口密度に比例すると仮定して都市の拡大による既存の農地と作物の潜在生産量の減少を試算した。本研究の分析および先行研究のレビューから，SRESシナリオで想定されている将来の社会・経済条件のもとでは，以下のことが予測された。1）先行研究から2000年の世界全体の都市面積は，41万km²から351万km²と見積もられ，南極を除く世界の陸地面積の0.3％から2.6％の推計幅を持つことが確認された。2）本研究において，MOD12の都市域を国連の都市人口統計と整合性を持つように補正した結果，2000年の世界全体の都市面積は112万km²と推計された（MOD12-a）。3）MOD12-aにおいて2050年の世界全体の都市面積はA2rシナリオで312万km²，B1シナリオで299万km²，B2シナリオで309万km²まで拡大することが予測された。4）このとき都市へ転用される農地面積は，世界全体で2050年にA2rシナリオで101万km²，B1シナリオで89万km²，B2シナリオで98万km²に達することが推計された。5）これにより世界全体の作物の潜在生産量は，2000年の潜在生産量と比較して2050年にはA2rシナリオで8.5％，B1シナリオで7.4％，B2シナリオで8.3％減少する。国別にみると，特にパキスタン，バングラデシュ，インドネシア，フィリピン，中国，ベトナム，カンボジア，インド，ミャンマーなどのアジアの途上国において減少率が著しく高くなることが示された。

抄録全体を表示

空中写真や衛星画像は,世界の氷河に関する知識を向上・蓄積させて来た道具として非常に効果的で,それらが果たしてきた役割は大きい.この解説記事ではリモート・センシング・データを使って主に南極・グリーンランド・アラスカ・スバールバル・パタゴニア・山岳地域の氷河を対象として行った研究についてレヴューした.内容を大きく,(1)ある地域の氷河インベントリー作成や氷河変動を求めるための,あるいは氷河表面状態などの氷河マッピング,(2)氷河表面高度の変化から,あるいは夏の終わりの画像を使って氷河質量収支を求める方法,そして(3)氷河流動とその変化,あるいは氷河流出などによる氷河ダイナミクスの解析,などに分けてレヴューを行った.古い空中写真と最近の衛星データを比べることによって,過去数十年間の氷河末端変化・面積変化・体積増減などが求められ,最近の地球温暖化への応答や海面上昇への寄与などが評価されるようになった.

抄録全体を表示

In , the geochemical properties of meltwater and pondwater are very sensitive to global warming. Therefore, understanding the geochemical properties of the meltwater and pondwater is crucial to evaluating global change. This study was performed to examine the chemical and isotopic compositions of the meltwater and pondwater at the Barton and Weaver Peninsulas of King George Island, , to understand their spatial variation and to evaluate factors controlling the surface water chemistry. The meltwater, pondwater and seawater were sampled at 50 sites of the Barton and Weaver Peninsulas during the period from 23 December 2010 to 5 January 2011. The chemical compositions of the meltwater and pondwater were mainly influenced by sea salt. Additionally, the influence of water-rock interaction was observed in some meltwater and pondwater. The LREE/HREE ratios of some of the pondwater in the Barton Peninsula showed a decreasing trend by influence of water-rock interaction. The influences of sea salt and water-rock interaction were more dominant at the Barton Peninsula than the Weaver Peninsula. The δ¹⁸O and δD of the meltwater and pondwater showed a wide range. Little evaporation losses were observed at the Barton Peninsula but evaporation losses did not occurred at the Weaver Peninsula.

抄録全体を表示

1972年3月～1973年2月の1ケ年間, 越冬生活を送った第12次日本南極地域観測隊29名中13名いてBMR, FFAの季節変動は次の如く要約される。
1.冬季7月のBMRの低下, 秋季2月のBMRの亢進を除いて他の月にはBMRの変動は認められない。
2.冬季7月のBMRの低下は, 6月の暗夜の時期における生活が屋内生活が主となり, 身体活動の減少と室内気温18℃に曝露されていた為の影響と考えられる。
3.秋季2月のBMRの亢進は, 越冬終了直前の為, 身体活動が最も激しくなり, かつ, 0℃～-10℃の外気温に曝露された為の亢進と考えられる。
4.FFAの季節変動には著明な傾向を認めなかった。FFAの血中濃度は全期間を進じて平均816.7μEq/lと高いレベルにあった。
5.FFAとBMRの関係は, FFAの高い者はBMRが亢進の傾向にあるが, 個人内でのFFAとBMRの変動は有意な負の相関々係をとっている。即ち, BMRが亢進するとFFAは減少する。
6.BMRとRQの間には負の相関々係を示し, BMRが亢進するとRQは低下する。個人内での変動にも同様に負の相関々係がある。
7.FFAとRQの間には負の相関々係を有し, FFAの高い者はRQが低いという関係にあるが, FFAとRQの個人内での変動では有意の相関々係は認められなかった。

抄録全体を表示

南半球の対流圏循環の特徴として南極の回りの深いトラフ、冬季の二重ジェット、海面気圧や東西流にみられる半年振動がある。この論文ではこれらの南半球の基本的特徴を再現している気象研究所大気大循環モデルの12年ランの結果について観測値(1979-1987)と比較して議論する。
7月の南北温度傾度は上部対流圏の30°S、下部対流圏の60°Sで大きい。強い傾圧帯の分布は東西に一様ではない。7月の500mb東西風は太平洋域では30°Sと60°Sに軸を持つ二重ジェット、大西洋•インド洋域では一本のジェットがモデルでシミュレートされており観測結果とよい対応がある。太平洋域の二本の傾圧帯(二重ジェット)は5月から10月まで存在する。残りの季節には高緯度側の一つだけになる。50°Sと60°Sの問では春と秋の年2回傾圧性が強くなり、東西風や海面気圧の半年振動が現れる。南極下層大気の初秋の急激な冷え込み、その後の真冬になっても気温がそれほど下がらず(コアレスウィンター)、春先に最低気温の出現する気温推移を正しくモデルでシミュレートすること及び南極大陸の波数1的地形に対応するインド洋にトラフ、太平洋にリッジを持った波数1の定常派の存在が南半球中•高緯度の半年振動や冬季の二重ジェットのシミュレーションに重要である。

抄録全体を表示

Changes in temperature-based extremes over land due to global warming estimated by a global 20-km-mesh atmospheric model are analyzed using Frich’s five extremes indices. At the end of the 21^st Century, under the Intergovernmental Panel on Change (IPCC) SRES A1B scenario, the model projects that the total number of frost days (Fd) decreases by more than 20 days per year and the length of the growing season (GSL) increases by about 14-34 days in northern mid- and high latitudes. The heat wave duration index (HWDI) and the percentage of time with a daily minimum temperature above the present-day 90^th percentile (Tn90) increase worldwide. The intra-annual extreme temperature range (ETR) decreases in northern high latitudes, east Asia, and eastern North America by 1.3-3.9°C, but it increases by 1.0°C in the Amazon. The high-resolution simulation reveals that changes in these indices are influenced by regional properties, such as the altitude and distance from the coast.

抄録全体を表示

The seasonal and wintertime interannual variability of the split jet and the storm-track activity minimum near New Zealand (NZ) have been examined based upon the European Centre for Medium Range Weather Forecast Reanalysis (ERA-40) 1979-2001 daily data. Using the split jet index defined in this paper, the climatological variation in the split jet is closely related to the storm-track activity minimum. In austral winter, the split jet is located near NZ along with the storm-track activity minimum, which is established by the climatological Rossby wave forced by the cross-equatorial flow in the Indian Ocean. In austral spring and autumn, in contrast, both the NZ split jet and the storm-track activity minimum are less clear in the absence of the Rossby wave, because of the near-zero Indian Ocean cross-equatorial flow.
However, interannual variation in the wintertime Indian Ocean cross-equatorial flow is only weakly associated with interannual variability in the split jet, the correlation being 0.14. The interannual variation in the cross-equatorial flow further east, in the Indonesian region, shows a higher correlation of 0.29. The middle and higher latitude components of the split jet structure are more strongly related to the zonally asymmetric part of the Antarctic Oscillation. An index for this has a 0.43 correlation on interannual time scales with the split jet index. Other processes must also be important for the interannual variability of the split jet and storm-track activity minimum in the NZ region. It is hypothesized that blocking in that region may be of particular importance.

抄録全体を表示