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

REN Suling FANG Xiang NIU Ning SONG Wanjiao

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-021, (Released:2023-05-16)

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Based on the vertical atmospheric sounding system carried by the FY-3D meteorological satellite (FY-3D/VASS) and the new wind radar instrument carried by the FY-3E meteorological satellite (FY-3E/WindRAD), a study of the potential application of research on the changes of temperature, humidity, and ocean wind vector (OWV) during the onset of the South China Sea summer monsoon (SCSSM) was carried out. The applications of these satellite datasets in SCSSM monitoring was evaluated, and the SCSSM onset process in 2022 was analyzed. The results showed that the mean bias of the FY-3D/VASS temperature and specific humidity at 850 hPa, compared with that of the fifth-generation ECMWF reanalysis, were −0.6 K and −0.53 g kg−1, respectively, and the pseudo-equivalent potential temperature (θse) was slightly lower, by 1-2 K; the distribution of θse was consistent with the seasonal advancement of the SCSSM. Compared with Metop-C/ASCAT, the mean bias of FY-3E/WindRAD zonal wind was positive and that of meridional wind was negative. The correlation coefficient, mean bias, mean absolute error, and root-mean-square error of the wind speed were 0.79, −0.45 m s−1, 1.56 m s−1, and 2.03 m s−1, respectively. The distributions of OWV were consistent, and the region and intensity of strong wind speed were close to each other. The temperature, humidity, and wind reversal during the onset of the SCSSM in 2022 were well-monitored by the FY-3D/E-derived θse and OWV dual indices, which are consistent with the SCSSM onset date, the third pentad in May, issued officially by the National Climate Center, China Meteorological Administration. Before the SCSSM onset in 2022, the tropical storms' pumping effect in early May increased the westerly wind over the tropical ocean north of the equator. After the storm weakened, the southwesterly wind passed across the Indochina Peninsula and reached South China Sea, causing the SCSSM onset.

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 14

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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

ISHIOKA Keiichi

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-008, (Released:2022-11-17)

被引用文献数

1

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Inspired by the detection of the Pekeris mode of atmospheric free oscillations by a recent study, high-accuracy numerical calculations of the problem of determining the equivalent depth of atmospheric free oscillations are performed. Here, the computational method is largely based on a previous study, but with modifications to improve the accuracy of the calculation. Two equivalent depths are found, with values of 9.9 km and 6.6 km. The former corresponds to the Lamb mode and the latter corresponds to the Pekeris mode. These values deviate from those obtained in the previous study, especially for the Pekeris mode. The causes of this discrepancy is discussed, as well as the correspondence between the equivalent depths obtained in this study and that of the Pekeris mode detected in the recent study.

著者

NAKANO Masuo CHEN Ying-Wen SATOH Masaki

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-013, (Released:2023-02-24)

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Typhoon Krosa (2019) formed in the eastern part of the Philippine Sea and ∼ 1400 km east of another typhoon Lekima on 6 August and made landfall in the western part of Japan's mainland on 15 August. The operational global model forecasts, which were initialized just after Krosa's formation, showed a very large uncertainty and totally failed to predict the actual track of Krosa. In this study, we investigated the causes of this large uncertainty through 101-member ensemble forecast experiments by using a 28-km mesh global nonhydrostatic model. The experiments initialized at 1200 UTC 6 August, showed a large uncertainty. An ensemble-based lagged correlation analysis indicated that the western North Pacific Subtropical High (WNPSH) retreated further east in the members with large track forecast errors than in the members with small errors. For the members with a large track forecast error for Krosa, Krosa and Lekima approached each other by 250 km and Krosa moved northward faster than the observation in 36 hours from the initialization time. For the members with a small track forecast error for Krosa, two typhoons approached each other by only 50 km, and the northward moving speed was comparable with that of the observation. The typhoon-center relative composite analysis exhibited that at the initialization time, the members with a large Krosa track forecast error had a larger horizontal size of Krosa and the difference in Krosa's size was kept during the forecast period. This difference in size led to a stronger interaction between the two typhoons and retreatment of the WNPSH, thus resulting in a fast northward moving speed for the members with a large Krosa track error.

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

LI Linhui LI Shuanglin

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-042, (Released:2022-07-07)

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Twentieth-century atmospheric reanalysis datasets are substantially important for understanding climate in the early era of the century. This paper first compares two sets of the twentieth-century atmospheric reanalyses, the NOAA-CIRES-DOE 20th Century Reanalysis Version 3 (20CRv3) and the ECMWF 20th century reanalysis (ERA20C), as far as the summer low-level cross-equatorial flows (CEFs) over the Asian-Australian monsoon region are concerned. The results show evident regional differences in intensity of individual branches of CEFs between the two reanalyses, in spite of an overall agreement in climatological seasonal mean and variability. At interannual timescale, significant differences are seen prior to 1925 and in the 1940s. During the two periods there are often opposite variations in Somali CEF in the two datasets, along with obvious different amplitudes (variances) in the Bay of Bengal (BOB) and Australian CEFs. At interdecadal timescale, the two datasets have different periodicities in Somali CEF, and have a greater fluctuation of BOB CEF after 1925 in ERA20C than 20CRv3, as well as an opposite decadal variation in the Australian CEF prior to 1940 and in the 1960s. As for the long-term trend, both the Somali and BOB CEFs exhibit intensification in both the datasets, but the intensification amplitude is bigger in 20CRv3 than ERA20C for Somali CEF; the Australian CEF exhibits a weakening trend in both the datasets, but is less evident in 20CRv3. To figure out which of the two datasets is relatively more reliable, the observed cross-equatorial meridional gradient of sea-level pressure index and the Indian summer monsoon rainfall index, which both have longer instrumental records, are used as benchmarks to validate the CEFs in view of their close connections. The results suggest that ERA20C is more reliable, and thus more suitable for investigating decadal climate variability of the 20th century across the hemispheres.

著者

WU Jing KUROSAKI Yasunori SEKIYAMA Tsuyoshi Thomas MAKI Takashi

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-004, (Released:2022-10-27)

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In drylands, the dry vegetation coverage affects dust occurrence by modulating threshold friction velocity (or wind speed) for dust emission. However, there has been little research into quantifying the effect of dry vegetation coverage on dust occurrence. This study investigated spatial and temporal variations of dust occurrence and three definitions of strong wind frequency over the Gobi Desert and surrounding regions in March and April, months when dust occurrence is frequent, during 2001-2021. We evaluated the effects of variations in dry vegetation on dust occurrence by using the threat scores of forecasted dust occurrences for each strong wind definition. Our results indicate that dry vegetation, which was derived from the MODIS Soil Tillage Index, affects dust occurrence more remarkably in April than in March. In March, land surface parameters such as soil freeze-thaw and snow cover, in addition to dry vegetation coverage, should be considered to explain dust variations in that month. However, use of the threshold wind speed estimated from dry vegetation coverage improved the prediction accuracy of dust occurrence in April. Therefore, we propose that the dry vegetation coverage is a key factor controlling dust occurrence variations in April. The findings imply that estimation of dry vegetation coverage should be applied to dust models.

著者

豊田 威信 浮田 甚郎 大島 慶一郎 若土 正暁 村本 健一郎

出版者

社団法人日本気象学会

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)

巻号頁・発行日

vol.77, no.1, pp.117-133, 1999-02-25

被引用文献数

5

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1996年と1997年の2月上旬、オホーツク海南西部の海氷域内部において、パトロール砕氷船「そうや」に乗船してアルベドの観測を行った。アルベドは船首部に上向き、下向きの短波放射計を取付けて測定した。同時に、海氷密接度および氷厚を、ビデオ観測データの解析により定量的に評価した。水平スケール数kmを対象とした解析の結果、アルベドと海氷密接度は良い相関が見られることが分かった。回帰式をもとに、海氷のアルベド(密接度100%)は95%の信頼区間で0.64±0.03と見積もられた。従来、極域定着氷上で測定された値よりもやや小さい値が得られたのは、低緯度海氷域内では海水や日射などの影響により、海氷上の雪粒子が成長しやすいためと推定される。観測値の回帰直線からのずれは、危険率1%で太陽天頂角と、危険率5%で氷厚と統計的に有意な相関が見られ、海氷密接度と太陽天頂角を変数とする重回帰式も導出された。重回帰式において、偏回帰係数はどちらも統計的に有意であるが、アルベドは太陽天頂角に比べて海氷密接度とより強い相関関係にあることが分かった。重回帰式と観測値との差異は氷厚あるいは雲量よりも主として海氷の表面状態の違いによって生じたものと推定される。これらの結果から、海氷上の積雪が海氷域のアルベドに及ぼす影響が大きいことが示唆された。一方、dark nilas(暗い薄氷)で覆われた海面上で停船した期間中に得られた短波放射データから、氷厚1〜1.5cmのdark nilasのアルベドは0.10、氷厚2〜3cmでは0.12と見積もられた。

著者

SATO Kazutoshi KAMEDA Takao SHIRAKAWA Tatsuo

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-045, (Released:2022-07-22)

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Iwamizawa on the Sea of Japan side of Hokkaido is one of the cities in Japan that experience frequent heavy snowfall events. Warm surface-layer ocean anomalies over the Sea of Japan can induce heavy snowfall over the Sea of Japan side of Japan; however, the relationship between ocean temperature over the northern Sea of Japan and snowfall events at Iwamizawa remains uncertain. This study used reanalysis data to investigate atmospheric and oceanic circulation anomalies associated with each anomalous heavy snowfall winter month at Iwamizawa. During all anomalous snowfall winter months at Iwamizawa, a cold air anomaly with northwesterly winds existed over the Far East that was associated with a dipole pattern with anticyclone anomalies over the north coast of the Eurasian Continent and cyclonic anomalies extending zonally over the Far East and northern Pacific Ocean. The surface cold air temperature and strong wind speed anomalies are major factor for anomalous upward turbulent heat flux over the northern Sea of Japan during all anomalous snowfall winter months at Iwamizawa. Additionally, during anomalous snowfall January, warm surface-layer ocean anomaly over the northern Sea of Japan, which preceded the heavy snowfall events at Iwamizawa by two months, has an important role in upward turbulent heat flux anomaly. This preceding warm ocean temperature anomaly was associated with a strong Tsushima Warm Current anomaly. Results showed that warm surface-layer ocean anomaly over the northern Sea of Japan that precedes anomalous cold advection from the Eurasian Continent has also large impact on producing heavy snowfall events over western Hokkaido coastal regions near Iwamizawa in January.

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

YAMADA Shunsuke KUSAKA Hiroyuki

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-039, (Released:2022-06-21)

被引用文献数

1

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We examined the essential features and formation mechanism of the strong local “Suzuka-oroshi” winds, which are located leeward of the Suzuka Mountains in Japan. This area features a favorable topography for downslope windstorms. Climatological analysis revealed that Suzuka-oroshi mainly occurred after an extratropical cyclone with a cold front and passed the Sea of Japan (55 % of all occurrences). Additionally, inversion layers (1-5 km level) were observed in 74 % of cases. Climatological analysis using spatially dense observational data showed that the strongest winds tended to blow in the northern part of the plain on the leeward side. Numerical simulations for one case by the Weather Research and Forecasting (WRF) model with 1 km grid increment supported this finding. Simulation results with and without the Suzuka Mountains demonstrated that the strong Suzuka-oroshi in the northern part of the plain comprised downslope windstorms with transition of flow regime (internal Froude number was less than 1.0 at the windward of mountains and larger than 1.0 above the leeward slope). Additionally, differences in height of the mountains between the north and south parts results in the greater wind speed in the northern parts compared to the southern parts.

著者

YANASE Wataru ARAKI Kentaro WADA Akiyoshi SHIMADA Udai HAYASHI Masahiro HORINOUCHI Takeshi

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-041, (Released:2022-06-30)

被引用文献数

5

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Torrential rain in Typhoon Hagibis caused a devastating disaster in Japan in October 2019. The precipitation was concentrated in the northern half of Hagibis during extratropical transition (ET). To elucidate the mechanisms of this asymmetric precipitation, synoptic- and meso-scale processes were analyzed mainly using the Japan Meteorological Agency Non-Hydrostatic Model. The present study demonstrates that the asymmetric processes were different depending on the ET stages. When Hagibis was close to the baroclinic zone at middle latitudes around 12 October (the frontal stage), heavy precipitation in the northeastern part of Hagibis was attributed to warm frontogenesis and a quasi-geostrophic ascent, as reported in many previous studies. In contrast, when Hagibis was moderately distant from the baroclinic zone around 11 October (the prefrontal stage), heavy precipitation in the northern part occurred in slantwise northward ascending motion in the outer region. This slantwise motion developed in a region with strong westerly vertical shear, which was enhanced between Hagibis and a westerly jet stream. Based on the analyses of potential vorticity and absolute angular momentum, this region was characterized by reduced moist symmetric stability in the lower and middle troposphere accompanied by inertial instability in the upper troposphere and conditional instability in the lower troposphere. These results provide additional insights into the time evolution of asymmetric processes during ET in the absence of a distinct upper-tropospheric trough, particularly the slantwise motion in the prefrontal stage.

著者

DATT Ishan CAMARGO Suzana J. SOBEL Adam H. MCTAGGART-COWAN Ron WANG Zhuo

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2022-037, (Released:2022-05-13)

被引用文献数

3

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A significant fraction of tropical cyclones develop in baroclinic environments, following tropical cyclogenesis “pathways” that are characterized by dynamical processes often associated with higher latitudes. This study investigates whether such storms are more likely to undergo subsequent extratropical transition than those that develop in more typical, non-baroclinic environments. We consider tropical cyclones globally in the period 1979-2011 using best-track datasets, and define the genesis pathway of each storm using McTaggart-Cowan's classification: non-baroclinic, low-level baroclinic, trough-induced, weak and strong tropical transition. In each basin, we analyze the total number and the fraction of storms that underwent extratropical transition, their seasonality, and storm tracks, according to their genesis pathways. The relationship between the pathways and extratropical transition is statistically significant in the North Atlantic and Western North Pacific, where the strong tropical transition and the trough-induced pathways have a significantly greater extratropical fraction compared to all other pathways, respectively. Latitude, longitude and environmental factors such as sea surface temperature and vertical shear were further analyzed to explore whether storms in these pathways happen to be in environments conducive to extratropical transition, or whether a “memory” of the genesis pathway persists throughout the storm life cycle. After controlling for genesis latitude, the relationship between the strong tropical transition and trough induced pathways, and extratropical transition occurrence remains statistically significant, implying a lasting effect from the pathway on the probability of an eventual extratropical transition.

著者

Ahoro ADACHI Takahisa KOBAYASHI Hiroshi YAMAUCHI

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.93, no.3, pp.359-388, 2015 (Released:2015-07-10)

参考文献数

78

被引用文献数

1 7

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A method for estimating three parameters of a gamma raindrop size distribution (DSD) model and the rainfall rate from polarimetric radar at attenuating frequency was developed. The algorithm was developed based on the self-consistency principle but was expanded to consider the attenuation effect by describing the interrelation between polarimetric measurements along the range profile. The proposed method does not require any assumptions of relation among DSD parameters or simplifications of equations that describe the relation between the axis ratio and diameter of raindrops, which have been used in previous studies. Moreover, the proposed algorithm needs no external reference data such as two-dimensional video disdrometer measurements for attenuation corrections because it retrieves the co-polar and differential specific attenuation from the interrelation among the polarimetric measurements. The performance of this algorithm was evaluated by comparison with optical disdrometers and a weighing precipitation gauge. The evaluation of the algorithm showed that the retrieved three DSD parameters of raindrops, reflectivity, and differential reflectivity from actual C-band polarimetric radar data have fairly good agreement with those obtained by surface measurements. Moreover, rainfall rates retrieved using this algorithm have comparable precision with those estimated from the specific differential phase, and outperform those estimated through the so-called Z-R relation, particularly during heavy rainfall. Furthermore, the effects of raindrop temperature and shape parameter on the retrieval of the rainfall rate were examined. The results show that for radar operating at C-band, a raindrop temperature error of 10°C may be negligible in rainfall rate estimations, whereas a shape parameter error of 2 may increase the error of the rainfall rate estimation by 10 %.

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

4

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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

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.