著者

Gerald STANHILL Shabtai COHEN

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.86, no.1, pp.57-67, 2008 (Released:2008-05-12)

参考文献数

28

被引用文献数

44 48

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Annual values of sunshine duration (SS) measured in Japan between 1890 and 2002 were used as a proxy for global irradiance (Eg↓) to study trends and changes in solar forcing at the Earth's surface. Proxy relationships established for the two SS recorders used in the JMA network both yielded estimates of mean annual values of Eg↓ with RMS &1t; 6%. A first order integrated moving average model (ARIMA) adequately described the time course of SS and Eg↓, which indicated a small, irregular but significant annual increase in solar forcing during the 20th century averaging 0.08 W m-2 or 2.3 hours of Jordan SS recorder sunshine, equivalent to 0.5% per decade. The rate of increase was four times the average in the first four and last three decades of the century reaching a maximum after 1980. The negative effect of the five major volcanic eruptions on Eg↓ was shown to yield a significant linear negative forcing of -41 W m-2 per unit AOD stratospheric aerosol optical depth). The degree of negative solar forcing was related to latitude: between 25° and 44°N each degree shift to the North was associated with an annual increase in Eg↓averaging 0.02%. The time course of changes in solar radiation in Japan during the 20th century resembled that measured in air temperature; correlations between annual values of Eg↓and those in the air temperature of the Northern Hemisphere were very highly significant (P < 0.001) both for the concurrent and preceding year.

著者

Kenneth Sassen

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.58, no.5, pp.422-429, 1980 (Released:2007-10-19)

参考文献数

14

被引用文献数

64 69

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大気中を自然落下している板状氷晶の落下姿勢と氷晶の大きさとの関係を知るため,氷晶によって生ずる光学現象である光柱(light pillars)の拡がり角および散乱光強度の分布を光柱写真の解析から求めた。その結果,レイノルズ数(Re)にして1.0<Re<100の範囲氷晶は,基底面(basal plane)を落下方向に対して垂直,すなわち水平方向に保つような落下姿勢が卓越し,特にRe=10前後ではこの姿勢が最も安定な落下姿勢であることが判った。落下中の板状結晶の基底面の水平方向からの傾き角は,大気中の乱れのため一般的には,水平方向を中心にガウス分布をしている。これら観測結果と,大気光学現象との関係や雲構成要素の性質のアクチブリモートセンシングについて議論を行った。

著者

Takeshi ENOMOTO Hirokazu ENDO Yayoi HARADA Wataru OHFUCHI

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.87, no.1, pp.139-156, 2009 (Released:2009-03-07)

参考文献数

43

被引用文献数

13 14

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In July 2004, torrential rainfalls caused significant damages in parts of Japan, followed by heat waves. Our data analysis shows that both rainfall and heat wave events in late Baiu season were caused by the intensification of the subtropical anticyclone near Japan (Bonin high) and that intensity of the Bonin high was significantly influenced by propagation of Rossby waves along the subtropical jet. Hindcast experiments from 15 July were conducted to study the mechanisms and predictability of these high-impact weather events. On 17-18 July, localized rainfalls at a few locations along the coast of the Sea of Japan including Sakata and Fukui were successfully simulated in a high-resolution (21-km mesh) global hindcast simulation. These rainfall events were found to occur near the leading edge of a filament of moist and warm air advected clockwise. On 20 July, anomalously high temperature was reproduced in the high-resolution hindcast simulation. With a moderate resolution of 83 km, the intensification of the subtropical anticyclone was reproduced although the föhn was much weaker. This result indicates that temperature distribution associated with föhn requires a resolution high enough to resolve major mountains. In order to investigate the predictability of propagation of Rossby waves and intensification of the Bonin high, 25-member ensemble experiments from 1 July 2004 were conducted using the moderate-resolution model. It is shown that the region along the Asian jet has twice as long predictability as the entire Northern Hemisphere. This case study suggests that the intensification of the Bonin high associated with the propagation of Rossby waves along the Asian jet could be predicted a few weeks in advance with an ensemble forecast at a moderate resolution.

著者

和田 章義 柳瀬 亘 岡本 幸三

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.100, no.2, pp.387-414, 2022 (Released:2022-04-07)

参考文献数

48

被引用文献数

1 4

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2018年台風第12号(ジョンダリ)は7月29日の日本上陸前に、対流圏上層寒冷低気圧の円周に沿った異常な経路をとった。大気海洋相互作用および対流圏上層寒冷低気圧とジョンダリの相互作用が台風経路に及ぼす影響を調べるため、3kmメッシュ非静力学大気モデルと大気波浪海洋結合モデル及び異なる初期時間を採用して作成した初期条件に基づく数値シミュレーションを実施した。シミュレーションされた対流圏上層寒冷低気圧は355K等温線上の高ポテンシャル渦度、低い気圧、低い相対湿度の特徴をもつ。7月25日から27日にかけて対流圏上層寒冷低気圧はジョンダリの北側を南西方向に移動し、この期間にシミュレーションされたジョンダリは対流圏上層寒冷低気圧の円周に沿って反時計回りに移動した。ジョンダリが西に移動し始めてから、大気波浪海洋結合モデルによるシミュレーション結果において、経路に沿って海面冷却が生じていた。日本上陸後にジョンダリは勢力を弱めると、対流圏上層寒冷低気圧も日本の南側で勢力を弱めた。特に潜熱フラックスと対流による対流圏上部における加湿が勢力の弱化に影響を与えていた。ジョンダリが九州の南海上で再び発達したとき、台風域では渦位は柱状に高くなり、一方で対流圏上層寒冷低気圧付近の対流圏上層渦位は相対的に低い値であったことから、台風域の渦は対流圏上層寒冷低気圧と合体する様子がシミュレーションされた。大気波浪海洋結合モデルのシミュレーション結果では、寒冷低気圧付近の対流圏上層部における高渦位は維持される一方、柱状の台風域の渦位はその高さを下げつつ弱まり、台風中心からの対流圏上層への外出流が弱まった。この結果、対流圏上層寒冷低気圧から変形した高渦位の折り返し位置に影響を与える様子が見られた。ジョンダリの経路に影響を及ぼす指向流は、対流圏上層寒冷低気圧下の地衡風の影響を受けていたため、実際は上記海洋結合の効果よりも大気初期条件の違いがジョンダリと対流圏上層寒冷低気圧両方の経路と強度により強い影響を与えていた。

著者

直井 萌香 釜江 陽一 植田 宏昭 Wei MEI

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.98, no.3, pp.655-668, 2020 (Released:2020-06-20)

参考文献数

48

被引用文献数

11 15

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中緯度の細い水蒸気輸送帯は大気の川と呼ばれ、東アジアにしばしば重大な社会・経済的影響をもたらす。夏季東アジアにおける大気の川の活動は、先行する冬季エルニーニョの発達に大きく左右される一方で、冬季から夏季にかけてのENSOの季節的な遷移が大気の川の活動にどの程度影響するのかは、明らかになっていない。本研究では、大気再解析と高解像度大気大循環モデルによるアンサンブル実験の結果を用いて、ENSOの季節的な遷移と夏季東アジアにおける大気の川の活動の関係を調査する。先行する冬季のエルニーニョから夏季のラニーニャへと早く遷移した年には、エルニーニョが持続または衰退した年に比べ、西部北太平洋の下層の高気圧偏差がより北へ拡大することにより、東アジア北部でより多くの大気の川が通過する。この高気圧の北への拡大は、海洋大陸と赤道太平洋上の凝結熱加熱偏差に対する大気の定常応答と整合する。再解析と大気大循環モデル実験とでは、中緯度の大気の川と循環の偏差が生じる位置が南北にずれており、これにはサンプル数が限られることとモデルバイアスが影響している可能性があり、東アジアにおける大気の川に関連した地域ごとの自然災害リスクの季節的な予測には課題が残されていることを示唆している。

著者

Peiming Wu Masayuki Hara Hironori Fudeyasu Manabu D. Yamanaka Jun Matsumoto Fadli Syamsudin Reni Sulistyowati Yusuf S. Djajadihardja

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.3, pp.93-96, 2007 (Released:2007-09-13)

参考文献数

10

被引用文献数

38 67

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Torrential rains that repeatedly occurred over Java Island causing widespread floods in late January and early February 2007 coincided with a strong and persistent trans-equatorial monsoon flow from the Northern Hemisphere. While convections develop frequently over the island’s mountainous areas in the afternoon, convections over the northern plains are active during the night and morning hours. The strong trans-equatorial monsoon flow with an upper southeasterly wind produces a strong low-level vertical shear of wind and dry mid-level environment over the island. These conditions allow the severe convections to occur repeatedly for days and to sustain for an extended period of time. The results suggest that the trans-equatorial monsoon flow plays a principal role in the formation of the repeated torrential rains. The probability of occurrence of a strong and persistent trans-equatorial monsoon flow that causes torrential rains and widespread floods over Java Island is estimated to be once every 5-10 years.

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.19, pp.ii-iii, 2023 (Released:2023-02-11)

参考文献数

2

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The Editorial Committee of Scientific Online Letters on the Atmosphere (SOLA) presents the SOLA Award to one or two outstanding papers published each year. We are pleased to announce that the SOLA Award in 2022 will be given to the paper by Dr. Yasumitsu Maejima et al., entitled “Observing system simulation experiments of a rich phased array weather radar network covering Kyushu for the July 2020 heavy rainfall event” (Maejima et al. 2022), and to the paper by Dr. Tomoe Nasuno et al., entitled “Impacts of midlatitude western North Pacific sea surface temperature anomaly on the subseasonal to seasonal tropical cyclone activity: Case study of the 2018 boreal summer” (Nasuno et al. 2022).

著者

Yousuke YAMASHITA Hideharu AKIYOSHI Theodore G. SHEPHERD Masaaki TAKAHASHI

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.93, no.6, pp.629-644, 2015 (Released:2016-01-13)

参考文献数

52

被引用文献数

7 9

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The combined influences of the westerly phase of the quasi-biennial oscillation (QBO-W) and solar maximum (Smax) conditions on the Northern Hemisphere extratropical winter circulation are investigated using reanalysis data and Center for Climate System Research/National Institute for Environmental Studies chemistry climate model (CCM) simulations. The composite analysis for the reanalysis data indicates strengthened polar vortex in December followed by weakened polar vortex in February-March for QBO-W during Smax (QBO-W/Smax) conditions. This relationship need not be specific to QBO-W/Smax conditions but may just require strengthened vortex in December, which is more likely under QBO-W/Smax. Both the reanalysis data and CCM simulations suggest that dynamical processes of planetary wave propagation and meridional circulation related to QBO-W around polar vortex in December are similar in character to those related to Smax; furthermore, both processes may work in concert to maintain stronger vortex during QBO-W/Smax. In the reanalysis data, the strengthened polar vortex in December is associated with the development of north-south dipole tropospheric anomaly in the Atlantic sector similar to the North Atlantic oscillation (NAO) during December-January. The structure of the north-south dipole anomaly has zonal wavenumber 1 (WN1) component, where the longitude of anomalous ridge overlaps with that of climatological ridge in the North Atlantic in January. This implies amplification of the WN1 wave and results in the enhancement of the upward WN1 propagation from troposphere into stratosphere in January, leading to the weakened polar vortex in February-March. Although WN2 waves do not play a direct role in forcing the stratospheric vortex evolution, their tropospheric response to QBO-W/Smax conditions appears to be related to the maintenance of the NAO-like anomaly in the high-latitude troposphere in January. These results may provide a possible explanation for the mechanisms underlying the seasonal evolution of wintertime polar vortex anomalies during QBO-W/Smax conditions and the role of troposphere in this evolution.

著者

Fumiaki Fujibe Nobuo Yamazaki Mitsugi Katsuyama Kenji Kobayashi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.1, pp.41-44, 2005 (Released:2005-04-21)

参考文献数

14

被引用文献数

78 86

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Long-term changes of precipitation intensity were analyzed using a dataset which was recently compiled by the Japan Meteorological Agency (JMA). After some quality check, data of four-hourly, daily, and hourly precipitation at 46, 61, and 8 stations, respectively, were used for the period 1898-2003 on the condition that data for at least 80 years were usable in each month. As the measure of precipitation intensity, ten categories were defined so as to equate the total precipitation amount in each month at each station. The result is characterized by increase of precipitation in high categories, namely intense precipitation, and decrease in low categories. The linear trend for the highest and lowest categories is ±20-30% per century. This feature is found invariably for four-hourly, daily, and hourly precipitation, and qualitatively for all the seasons and regions.

著者

Masahiro Ohashi H. L. Tanaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.6A, no.SpecialEdition, pp.1-4, 2010 (Released:2010-03-13)

参考文献数

17

被引用文献数

6 5

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In this study, we investigate the mechanism of the arctic warming pattern in surface air temperature (SAT) and sea ice concentrations over the last two decades in comparison with global warming since the 1970s.According to the analysis result, it is found that the patterns of SAT and sea ice before 1989 are mostly determined by the Arctic Oscillation (AO) in winter. In contrast, arctic warming patterns after 1989 are characterized by the intensification of the Beaufort High and the reduced sea-ice concentrations in summer induced by the positive ice-albedo feedback.It is concluded that the arctic warming before 1989 especially in winter was explained by the positive trend of the AOI. Moreover the intensified Beaufort High and the drastic decrease of the sea ice concentrations in September after 1989 were associated with the recent negative trend of the AOI. Since the decadal variation of the AO is recognized as the natural variability of the global atmosphere, it is shown that both of decadal variabilities before and after 1989 in the Arctic can be mostly explained by the natural variability of the AO not by the external response due to the human activity.

著者

HSIEH Min-Ken CHEN Yu-Wen CHEN Yi-Chun WU Chien-Ming

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-028, (Released:2022-03-10)

被引用文献数

3

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We applied tracer transport simulations using Taiwan vector vorticity equation cloud-resolving model (TaiwanVVM) to evaluate the effects of the local circulation associated with the lee vortex and the planetary boundary layer development on the transport and accumulation of the pollutants on a diurnal time scale in central Taiwan. The wind directions of crucial synoptic northeast monsoon are idealized as the initial conditions of the simulations to examine the impact of the lee vortex on the pollutants transport. The primary local non-traffic emission sources are taken as the tracer emission sites so that the experiment results could be a good proxy of the realistic scenarios. With the local circulation over complex topography being resolved explicitly, the impact of the boundary layer development on the tracer transport of the Puli basin is discussed. The simulation results clarify the contribution of the sea breeze and the lee vortex to the tracer transport in central Taiwan. We conclude that high tracer concentration at Puli at night is due to the tracer being trapped by the thinning of the mixed layer depth in the evening. The sensitivity of the local tracer transport to the change of the synoptic wind direction shows that under northeasterly due east (due north) environment, the pollutant transports from the southern source (northern source) of central Taiwan are most likely to induce high concentration in Puli at night. This is the first study to distinguish the contribution of the sea breeze and the lee vortex in pollutants transport in Taiwan. The results obtained from idealized experiments provide the possible mechanism of pollutants transport, which could be taken as an insight to interpret the observations and guide the design of field experiment to further establish the fundamental principles of the pollution transports in central Taiwan.

著者

Prabir K. PATRA Edward J. DLUGOKENCKY James W. ELKINS Geoff S. DUTTON 遠嶋 康徳 笹川 基樹 伊藤 昭彦 Ray F. WEISS Manfredi MANIZZA Paul B. KRUMMEL Ronald G. PRINN Simon O'DOHERTY Daniele BIANCHI Cynthia NEVISON Efisio SOLAZZO Haeyoung LEE Sangwon JOO Eric A. KORT Suman MAITY 滝川 雅之

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.100, no.2, pp.361-386, 2022 (Released:2022-04-13)

参考文献数

65

被引用文献数

8

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大気中の一酸化二窒素(N2O)は地球温暖化および成層圏オゾン減少に影響を及ぼしており、発生源ごとの放出量推定の精緻化は気候変動の政策決定において非常に重要である。本研究ではまず大気大循環モデルMIROC4を基にした化学輸送モデル(ACTM)を用いたコントロール実験を行い、大気中N2O濃度の時空間変動について現場観測等を用いた検証を行なった。本計算に際しては各種起源(土壌起源、農業起源、その他人為起源、海洋起源)について複数のインベントリを用い、合計5種類の組み合わせで計算を行なった。その結果、N2Oの大気中寿命は年々変動の影響を含め、127.6±4.0年と推定された。次に、世界各地の42地点における1997年から2019年にかけての観測結果を用いて、世界を84分割した各地域におけるN2O放出量についてベイズ手法を用いた逆解法による推定を行なった。その結果、全球の陸域および海洋起源それぞれの放出量は2000年代には12.99±0.22 および 2.74±0.27 TgN yr-1、2010年代は14.30±0.20および 2.91±0.27 TgN yr-1と推定された。 地域別に見ると、南極海周辺での海洋起源放出量について既存インベントリが過大評価傾向にあることがわかった。一方熱帯域および中高緯度域の地表からの放出量についてはそれぞれ過少および過大評価傾向にあったと考えられ、別の観測の結果とも整合的であった。また全球の陸域および海洋起源放出量の時間変動についてはエルニーニョ・南方振動と強い相関が見られた。地域ごとの陸域起源放出量の2000年代と2010年代の間の変化量について調べたところ、北アメリカ、中央および熱帯アメリカおよび中央アフリカ、南、東および東南アジアで増加傾向が見られた。一方ヨーロッパでは減少する傾向が見られたが、これは化学工業に起因すると推定された。また15地域中3地域(東アジア、北アメリカおよび中央アフリカ)および南極海において、季節変化について今後の改良が必要なことが示唆された。陸域生態系モデル(VISIT)による推定放出量を用いた場合、観測から推定される1978年以降の増加速度をよく再現しているが、一方で窒素肥料の施肥から大気への放出にかかる変換時定数については改めて検討する必要があることが示唆された。

著者

HSU Wei-Ching KIKUCHI Kazuyoshi ANNAMALAI H. RICHARDS Kelvin J.

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-020, (Released:2021-12-21)

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Previous studies suggest the nature of the air-sea interaction of the tropical intraseasonal oscillation (ISO) can strongly influence our understanding and simulation of the ISO characteristics. In this study we assess the representation of the surface components in three of the most up-to-date reanalyses, including ERA5, ERA-interim (ERAi), and JRA55, to identify which reanalysis dataset is more suitable for investigating air-sea interaction associated with the ISO, and to quantify the intraseasonal biases of related variables for simulating the ocean responses. All three reanalyses well capture the ISO convective characteristics in terms of the spatial patterns and the propagation features, although the amplitude of the outgoing longwave radiation is severely underestimated (by ∼40 to 60 %, depending on region and season) in JRA55. Out of the two ERA reanalysis datasets, our results indicate the ERA5 may serve as a better ocean forcing dataset, as the ERAi largely underestimates the magnitudes of the ISO-related precipitation and 10-meter winds (of summer ISO, or BSISO) while overestimates the latent heat flux (of winter ISO, or MJO). JRA55, while having comparable amplitude biases to ERA5 in variables except precipitation, generally shows larger phase biases than the two ERA renalyses.

著者

TAO Wei-Kuo LANG Stephen IGUCHI Takamichi SONG Yi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-015, (Released:2021-12-13)

被引用文献数

5

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The Goddard Convective-Stratiform Heating (CSH) algorithm has been used to retrieve latent heating (LH) associated with clouds and cloud systems in support of the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) mission. The CSH algorithm requires the use of a cloud-resolving model (CRM) to simulate LH profiles to build look-up tables. This paper describes the current V6 CSH and its differences/similarities versus the previous V5 CSH. Long-term CRM simulations are conducted to identify the impact of CRM resolution and the convective-stratiform separation method on LH structure/profiles. The TRMM and GPM Combined radar-radiometer algorithm derived surface rain rates and their associated precipitation properties are the input to the CSH algorithm. CSH V6 retrieved regional LH profiles in the tropics and subtropics display the classic signatures of heating in the convective region and heating over cooling in the stratiform region. Since there is no direct measurement of LH structure, the performance of the CSH V6 algorithm is examined by comparing its vertically-integrated heating (or equivalent surface rain rate) against the surface rain rate derived from the TRMM/GPM Combined algorithm. The CSH three-month and zonal mean equivalent surface rain rates are in good agreement with the Combined rain rates over the ITCZ region; the agreement is best over ocean. CSH three-month and zonal mean equivalent surface rain rates are larger than the Combined rain rates over land in both the tropics and sub-tropics. CSH three-month mean equivalent surface rain rates also have local differences with the Combined rain rates that can be smoothed by area averaging to larger horizontal resolutions (from the CSH standard grid of 0.25° × 0.25° to 0.5° × 0.5° or 1.0° × 1.0°). CSH equivalent surface rain rates have more light rain rates but less larger rates compared to the GPM Combined surface rain rates.

著者

Yaokun Li Yanyan Kang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.76-80, 2022 (Released:2022-04-25)

参考文献数

23

被引用文献数

2

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The energy dispersion process of westward propagating Rossby waves in tropical easterlies are investigated in the linear nondivergent barotropic atmosphere. The variations in wave energy and amplitude along energy dispersion paths are calculated by solving the wave action conservation equation. The results suggest that a westward marching ray can form a cycle-like path near the turning latitude that is located in easterlies. Waves with shorter periods propagate between two turning latitudes, which are located in either the easterlies or westerlies and have the largest meridional propagation range. Waves with longer periods propagate between a turning latitude in westerlies and a critical latitude in easterlies. Both wave energy and amplitude can simultaneously increase to their maximum values at the turning latitudes that are located in easterlies. This implies that waves may develop significantly. Wave energy and amplitude do not always have an in-phase variation when the ray moves toward the turning latitude that is located in westerlies. The oscillating ranges of wave energy and amplitude are also limited. In this case, waves may not develop significantly.

著者

FUDEYASU Hironori SHIMADA Udai OIKAWA Yoshinori EITO Hisaki WADA Akiyoshi YOSHIDA Ryuji HORINOUCHI Takeshi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-031, (Released:2022-04-21)

被引用文献数

4

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This study investigated the atmospheric and oceanic contributions to the genesis of Typhoon Faxai in 2019. Our statistical analysis using the tropical cyclone genesis score (TGS) attributed the tropical disturbance that developed into Faxai (Pre-Faxai) to easterly waves (EWs). The EW score evaluated by a grid version of the TGS (Grid-EW) averaged around the occurrence of Pre-Faxai was approximately twice as large as the climatological mean; it was the second largest value in the past 38 years. The Pre-Faxai area with high Grid-EW scores could be traced back to the eastern North Pacific (ENP) around August 25, 2019. The lower-troposphere environment characterized by high Grid-EW scores was favorable for vortex formation because it provided a containment area for moisture entrained by the developing circulation or lofted by the deep convection therein. The Pre-Faxai area with high Grid-EW scores moved westward because of the background easterly flow over the ENP, then entered the western North Pacific (WNP). The Typhoon Intensity Forecast Scheme (TIFS) showed that the important environments for its genesis were ocean conditions and the vertical wind shear. The oceanic conditions contributed to the development of Pre-Faxai as it traveled over the WNP. The enhancement of vertical wind shear and subsequent suppression of the development of Pre-Faxai were caused by the lower-troposphere easterly winds associated with high EW scores; they were also caused by upper-troposphere westerly winds associated with an upper cold low northwest of Pre-Faxai. When the vertical shear decreased with weakening of the upper cold low, Pre-Faxai reached tropical storm intensity on September 4. Therefore, TGS and TIFS detected Pre-Faxai 10 days before the typhoon arose, an indication that monitoring environmental factors such as EW and vertical wind shear are important for disaster prevention.

著者

OSE Tomoaki ENDO Hirokazu TAKAYA Yuhei MAEDA Shuhei NAKAEGAWA Toshiyuki

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-032, (Released:2022-04-14)

被引用文献数

3

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Robust and uncertain sea-level pressure patterns over summertime East Asia in the future global warming projections and their causes are studied by applying the inter-model empirical orthogonal function (EOF) analysis to the multi-model experiments in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and focusing common features with the previous CMIP5 analysis. The ensemble average and the first to third EOF modes associated with future pressure changes are similar to the corresponding ones from CMIP5. The first and second modes represent strengthened and weakened high pressure systems in subtropical and northern East Asia, respectively. The third mode is the reverse anomaly of the climatological pressure pattern over summertime East Asia, indicating weakened southerly monsoon winds. The second mode pattern makes positive contributions to almost all the CMIP6 future pressure changes, representing a robust future projection pattern. The robust mode is the result of surface warming over the northern continents and neighboring seas that is stronger than the global average. The first and third modes are considered to be uncertain (but major) patterns in the ensemble projections because the signs of their contributions to the future changes are dependent on the model used. Suppressed vertical motion over the equatorial (northern) Indian Ocean caused by the vertically stabilized atmosphere under the global warming scenario is the source of the first (third) mode, together with the counter vertical motion anomaly over the equatorial (northern) Pacific. The above characteristics of the modes are essentially similar to those identified in the CMIP5 analysis while different sea surface temperature anomalies are related to the secondary structures of the modes. Some uncertainties in the future projections can be attributed to the systematic differences in the model climatology of the present-day precipitation, which determines the distribution of the suppressed vertical motion under the future warmer climate.

著者

Hirokazu Endo Akio Kitoh Ryo Mizuta

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.58-64, 2022 (Released:2022-03-29)

参考文献数

38

被引用文献数

1

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Future changes in extreme precipitation over the western North Pacific and East Asia (WNP-EA) are investigated using a 20 km mesh atmospheric general circulation model (AGCM). Time-slice simulations are performed under low- and high-emission scenarios using different spatial patterns of changes in sea surface temperature. In the WNP-EA region, future changes in the climatological mean of the annual maximum 1 day precipitation total (Rx1d) are characterized by a large meridional variation, where the higher the latitude, the greater the rate of increase in Rx1d, although this pattern is not so clear under the low emission scenario. This feature probably results from a combination of two factors: a greater warming in high latitudes and a decrease in tropical cyclone (TC) frequency in the subtropics. The future changes in Rx1d climatology for the 20 km AGCM show a marked difference in comparison with those of the lower-resolution AGCM and conventional climate models. Part of this discrepancy may come from differences in model resolution through representation of TCs, suggesting that coarse-resolution models may have some systematic bias in future projections of extreme precipitation in the WNP-EA region.

著者

NUR'UTAMI Murni Ngestu HAYASAKA Tadahiro

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-004, (Released:2021-10-04)

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The interannual and interdecadal variabilities of Indonesian rainfall in dry seasons (June–November) are investigated by using rainfall data from the Climate Research Unit (CRU) from 1939 to 2016, and from the Global Precipitation Climatology Project (GPCP) from 1979 to 2016. The first principal component (PC1) of both the CRU and GPCP data shows that the canonical El Niño-Southern Oscillation (ENSO), ENSO Modoki, and Indian Ocean Dipole (IOD) are major climate modes influencing the interannual variability of rainfall in Indonesia, and the Interdecadal Pacific Oscillation (IPO) is the major decadal phenomenon affecting the decadal variability of the rainfall. Furthermore, the IPO modulates the influence of IOD on Indonesian rainfall, with a weaker influence during the positive IPO phase during 1979-1997 and a stronger influence during the negative IPO phases during 1939-1978 and 1998-2016. The dependency of Indonesian rainfall response to the canonical ENSO and ENSO Modoki on IPO phases is not significant, although the response to the ENSO Modoki (canonical ENSO) becomes significant (less significant) in the negative IPO phase during 1998-2016 compared with earlier periods.

著者

TAKAHASHI Chiharu IMADA Yukiko WATANABE Masahiro

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-014, (Released:2021-11-12)

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The present study found a significant influence of the Madden-Julian Oscillation (MJO) on the occurrence probability of extreme snowfall and precipitation in Japan during boreal winter (December-February) using observational data and the Database for Policy Decision Making for Future Climate Change (d4PDF). The analysis of d4PDF containing 90-member and 50-member ensemble historical simulations by global and high-resolution regional models, respectively, enabled us to quantify and elucidate the geographical distribution of the occurrence probability of extreme weather in Japan related to the MJO. The d4PDF global simulations well represent the MJO and its teleconnection over the Pacific-North America region. Our results show that (1) the probability of extreme snowfall on the Sea of Japan side of northwestern Japan (SJA) increases (decreases) by approximately 20 % (30-40 %) associated with enhanced MJO over the Maritime Continent and western Pacific (western Indian Ocean) relative to that for all winter days; (2) the extreme precipitation on the Pacific Ocean side (PAC) of Japan increases (reduces) by 40-50 % (approximately 30 %) when the MJO is active over the Indian Ocean (western Pacific); and (3) the extreme snowfall on the Kanto area in PAC increases by 30-45 % when the MJO is enhanced over the eastern Indian Ocean and Maritime Continent. Composite analysis reveals that different physical processes associated with the MJO are responsible for the occurrence of extremes in the three regions. The MJO intensifies cold air intrusion from Siberia into Japan associated with a more frequent blocking over East Siberia, causing extreme snowfall in SJA. The MJO stimulates the explosive development of extratropical cyclones due to enhanced moisture flux convergence, leading to extreme precipitation in PAC and extreme snowfall in Kanto. Furthermore, the Kanto snowfall is partly related to a cold air outflow from the blocking induced by the MJO.