著者

谷田貝 亜紀代 安成 哲三

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.76, no.5, pp.799-815, 1998-10-25 (Released:2008-01-31)

参考文献数

27

被引用文献数

34 45

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ユーラシア大陸内陸の乾燥地域周辺は、砂漠化の問題が生じている地域であり、それらの地域の水循環の変動を、全球、大陸スケールの気候変動とあわせて明らかにすることは不可欠である。内陸の乾燥地域においても、夏季にしばしば強い降水がみられるが、それに関連する水蒸気輸送場は、若干の事例解析があるのみで、気候変動と関連づけて研究した例はほとんどない。そこで、本研究はまず、ユーラシア大陸内陸の乾燥地域周辺における夏季の水蒸気輸送とその収束発散場をヨーロッパ中期予測センター(ECMWF)の再解析データを5年間(1980-1984年)について使用して調べた。夏季平均の鉛直積分された水蒸気フラックス場は、モンゴルと中国北部には北西方向からの水蒸気が輸送されることを示す。平均場では、これらの地域の水蒸気源は西シベリアと、さらにその西方向である。大陸のうち最も乾燥したタクラマカン砂漠への、対流圏下層の水蒸気輸送場をみると、この地域の北西方向からの水蒸気が天山山脈の東側をまわりこむように水蒸気が輸送されていることがわかった。次にタクラマカン砂漠の降水と日平均水蒸気輸送場の関係を統計的に調べた。タクラマカン砂漠周辺の全層水蒸気フラックス場をクラスター分析により、まず8パターンに分類した。次に、日降水量と大気循環場をこれらのクラスターごとに合成した。全体の約9割は、平均場に似て、北西からの輸送に関係したパターンであり、このケースの場合、上空にトラフが存在する時に降雨がみられる。しかし、時折、チベット高原を越えて南から水蒸気が流入し、同時にタクラマカン東部(チベット高原の北東側)の下層で東から水蒸気が入り込むことがあり、このパターンはタクラマカンの強い降水と関係している。大気循環場の特徴として、500hPa等圧面高度の合成図をみると、南西方向に深く伸びたトラフがタクラマカンの北側に出現し、これと同時に中央アジアではリッジが現れる。東風の見られるタクラマカン東部には下層に低気圧が存在する。このケースは、全体の10%以下であるが、出現は多雨年に偏り、多雨年(1981, 1984)の夏季降水量の約半分がこのような循環場でもたらされている。

著者

谷田貝 亜紀代 安成 哲三

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.73, no.5, pp.909-923, 1995-10-25 (Released:2008-01-31)

参考文献数

32

被引用文献数

63 78

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中国とモンゴルの乾燥・半乾燥地域における夏季降水量の経年変動を解析した。回転主成分分析の手法を夏李(6-8月)降水量時系列(1951-1990年)に適用し、その経年変動特性により、対象地域を次の5地域に区分することが出来た。I)タクラマカン砂漠、II)黄土高原、III)中国華北~モンゴル中・南東部、IV)天山山脈の北側、V)モンゴル北部。地域III)の代表的な時系列は、1955年以降の降水量の有意な減少傾向を示した。次に、対象地域の降水量の経年変動とアジアモンスーン活動との関連を調べるために、インド総降水量資料とこれらの地域の降水量変動との関係をモンスーン期の合計降水量についてだけでなく、夏季の各月について調べた。その結果、地域I)、II)の代表時系列はインド総降水量と、それぞれ負、正の相関が見られたことから、ここではこの2地域の夏季降水量の経年変動と大気大循環場との関連を、北半球の100hPa、500hPa高度及び地上気圧の偏差を使用して解析した。その結果、地域I)(タクラマカン砂漠)の夏季降水量の経年変動は、偏西風循環の風上側(大西洋~ユーラシア大陸)の偏差と関係し、多雨年にはトラフが90゜E付近に存在すること、また、チベット高気圧が多(小)雨年にはその東側で強く(弱く)なることがわかった。地域I)の6、7月の降水量はインド総降水量と負相関が見られた。この両地域の夏季降水量の経年変動の関係は中央アジア周辺の比較的局地的な循環場を介在していることが示唆された。一方、地域II)(黄土高原)の2-3年周期を呈する時系列は、6-9月の各月においてインド総降水量と正相関が見られた。対応する大循環場の変動は、太平洋高気圧、チベット高気圧、イラン周辺の地上気圧に見られた。これらは地域II)の夏季降水量の経年変動が、よりグローバルな、モンスーンに伴う大気海洋相互作用と密接な関わりがあることを示唆している。

著者

鬼頭 昭雄 行本 誠史 野田 彰 本井 達夫

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.75, no.6, pp.1019-1031, 1997-12-25 (Released:2009-09-15)

参考文献数

25

被引用文献数

102 142

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大気中の二酸化炭素濃度増加によるアジアの夏季モンスーンの変化を気象研究所全球大気・海洋結合モデルにより調べた。温暖化によりインドの夏季(6~8月)の降水量は顕著に増加するが、逆に850hPaと200hPaの東西風のシアーで定義したモンスーンの風のインデックスは弱くなった。これは850hPaのモンスーン西風の北偏によるもので、サヘルからインド北西部にかけての西風が強化され、一方アラビア海の西風は弱くなる。大気中の水蒸気量が増加するので水蒸気輸送は増加し、降水量の増加をもたらしている。従って風のインデックスは温暖化の良い指標とはいえない。また、中国では降水量変化は少なく土壌は逆に乾燥しており、インドと大きく異なる変化をしている。インドの降水量の年々変動は温暖化により増加した。しかしながらこの年々変動の大きさは制御実験・二酸化炭素濃度漸増実験ともに数十年スケールで変化しており、温暖化による降水量変動度の変化の推定には注意を要する。

著者

Takuto Sato Hiroyuki Kusaka Hideitsu Hino

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-018, (Released:2020-05-20)

被引用文献数

10

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This study reveals the best combination of meteorological variables for the prediction of the number of emergency transport due to heat stroke over 64 years old in Tokyo metropolis based on a generalized linear model using 2008-2016 data. Temperature, relative humidity, wind speed, and solar radiation were used as candidates of the explanatory variables. The variable selection with Akaike's information criterion (AIC) showed that all the four meteorological elements were selected for the prediction model. Additional analysis showed that the combination of daily mean temperature, maximum relative humidity, maximum wind speed, and total solar radiation as explanatory variables gives the best prediction, with approximately 19% less error than the conventional single-variable model which only uses the daily mean temperature. Finally, we quantitatively estimated the relative contribution of each variable to the prediction of the daily number of heat stroke patients using standardized partial regression coefficients. The result reveals that temperature is the largest contributor. Solar radiation is second, with approximately 20% of the temperature effect. Relative humidity and wind speed make relatively small contributions, each contributing approximately 10% and 9% of the temperature, respectively. This result provides helpful information to propose more sophisticated thermal indices to predict heat stroke risk.

著者

Masaki Katsumata Kyoko Taniguchi Tomoaki Nishizawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.16A-002, (Released:2020-05-19)

被引用文献数

2

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A shipboard lidar system was examined the capability to retrieve detailed variation of the water vapor mixing ratio in and above the marine atmospheric boundary layer (MABL). The water vapor mixing ratio is retrieved from the ratio of Raman lidar signals by water vapor and by nitrogen, with the help of radiosonde data beside. Data obtained during two special observations, Pre-YMC and YMC-Sumatra, off the west coast of Sumatra island were examined. The mixing ratio was retrieved in the nighttime over 1 km height with the resolution of 10-minutes in temporal and 120-meters in vertical. The root mean square difference from the radiosonde data is about or less than 1 g/kg in MABL. A case study demonstrates that the retrieved spatiotemporal variation of water vapor mixing ratio captures meso-scale drying and moistening in detail. The capabilities of the retrieved data were well demonstrated, while number of improvements are expected in future work.

著者

Satoru Yokoi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.16A-001, (Released:2020-05-15)

被引用文献数

4

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Given vigorous mean diurnal variation (MDV) of cumulus convection and surface wind over coastal waters of Indonesian Maritime Continent, surface sensible and latent heat fluxes (SHF and LHF) are expected to also exhibit significant MDV. However, it is difficult to grasp characteristics of MDV of these fluxes due to lack of surface observation data. Recently, two intensive observation campaigns were conducted off the west coast of Sumatra Island in boreal winter, which offer us a unique opportunity to examine the characteristics of convection and the fluxes. This study analyzes these observations to reveal that the MDV of both SHF and LHF has considerable amplitude compared with the average. The MDV of SHF is primarily caused by that in surface air temperature, which is due to the MDV of the convection. As for LHF, the MDV is primarily caused by that of surface wind speed, in which both the MDV of convection and sea/land breezes play roles. Furthermore, there are qualitative differences in the MDV of the fluxes between the two campaign periods, which can be explained from the viewpoint of differences in phase and intensity of MDV of convection and the sea/land breezes.

著者

TOMITA Tomohiko YAMAURA Tsuyoshi

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.2020-018, (Released:2020-02-11)

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The Baiu front (BF) is generally formed in May in the western North Pacific. Using objective analysis data from 1979 to 2014 (36 years), this study investigated the interannual variability of Baiu frontal activity (BFA) in May (BFA-M). In May, seasonal enhancement of warm and moist southerlies from the tropics climatologically establishes the BF as a large-scale quasi-stationary front. The strength of the southerlies from the tropics also controls the interannual variability of BFA-M. The anomalous large-scale circulation centered around Taiwan, which can be interpreted as a moist Rossby wave from the equatorial Kelvin–Rossby wave packet in the western tropical Pacific, modifies the strength of the southerlies. The equatorial Kelvin–Rossby wave packet, which is identified as the equatorial intraseasonal oscillation (ISO), propagates eastward from the Indian Ocean to the western Pacific. The interannual variability of BFA-M has a biennial tendency, which stands in contrast with the three-year or four-year variation period of the El Niño/Southern Oscillation (ENSO). The biennial tendency is characterized by a zonal tripole distribution of sea surface temperature anomalies in the tropical Pacific, with corresponding anomalous Walker circulations. The induced anomaly fields are suitable for confining the disintegration of the equatorial Kelvin–Rossby wave packet in the western tropical Pacific and guiding the following northwestward propagation of the moist Rossby wave. With the phase reversal of ISO, the biennial tendency remains in the western part of the BF from May to mid-June, although the ENSO controls the BFA in the central part of the BF in June. This study proposes that the equatorial ISO in the Indian Ocean in April can be an indicator of BFA-M strength in the western North Pacific.

著者

荒川 秀俊

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.16, no.6, pp.233-236, 1938-06-05 (Released:2009-02-05)

参考文献数

2

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Mit Hilfe der passend vereinfachten Bewegungsgleichungen, welche von N. Kotschin(1) geschaffen sind, wird gezeigt, welche Eigenschaften für die allgemeine atmosphärische Zirkulation aus den Gesetzen der Aerodynamik folgen, und wie die Temperaturverteilungen sowie die Luftdruckverteilungen die Zirkulation beeinflussen

著者

Noriko N. Ishizaki Motoki Nishimori Toshichika Iizumi Hideo Shiogama Naota Hanasaki Takahashi Kiyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-014, (Released:2020-04-01)

被引用文献数

24

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Bias corrected climate scenarios over Japan were developed using two distinct methods, namely, the cumulative distribution function-based downscaling method (CDFDM) and Gaussian-type Scaling approach (GSA). We compared spatial distribution, monthly variation, and future trends. The seasonal distribution of bias-corrected data using CDFDM closely followed the original general circulation model (GCM) outputs. GSA overestimated the amount of precipitation by 12-18% in every season because of an unsuitable assumption on the probability distribution. We also examined the contributions of each source of the uncertainty in daily temperature and precipitation indices. For daily temperature indices, GCM selection was the main source of uncertainty in the near future (2026-2050), while different Representative Concentration Pathways (RCPs) resulted in large variability at the end of the 21st century (2076-2100). We found large uncertainty using the bias-correction (BC) methods for daily precipitation indices even in the near future. Our results indicated that BC methods are an important source of uncertainty in climate risk assessments, especially for sectors where precipitation plays a dominant role. An appropriate choice of BC, or use of different BC methods, is encouraged for local mitigation and adaptation planning in addition to the use of different GCMs and RCPs.

著者

Ayataka Ebita Shinya Kobayashi Yukinari Ota Masami Moriya Ryoji Kumabe Kazutoshi Onogi Yayoi Harada Soichiro Yasui Kengo Miyaoka Kiyotoshi Takahashi Hirotaka Kamahori Chiaki Kobayashi Hirokazu Endo Motomu Soma Yoshinori Oikawa Takahisa Ishimizu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.7, pp.149-152, 2011 (Released:2011-10-06)

参考文献数

24

被引用文献数

289 412

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The Japan Meteorological Agency (JMA) started the second Japanese global atmospheric reanalysis project named the Japanese 55-year Reanalysis (JRA-55). It covers 55 years, extending back to 1958, when the global radiosonde observing system was established. Many of the deficiencies found in the first Japanese reanalysis, the Japanese 25-year Reanalysis (JRA-25), have been improved. It aims at providing a comprehensive atmospheric dataset that is suitable for studies of climate change or multi-decadal variability, by producing a more time-consistent dataset for a longer period than JRA-25.Production of JRA-55 started in 2010, and computations for more than 16 years have been completed as of August 2011. The entire JRA-55 production will be completed in early 2013 and thereafter JRA-55 will be continued as a new JCDAS on real time basis. This paper is a brief report to introduce the JRA-55 reanalysis project. The data assimilation and prediction (DA) system used in JRA-55 is introduced and compared to that used in JRA-25. Early results of JRA-55 are presented and discussed, showing general improvements.

著者

Kenji YOSHIDA Hisanori ITOH

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.90, no.3, pp.377-401, 2012-06-25 (Released:2012-06-30)

参考文献数

46

被引用文献数

12 17

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This study examines the indirect effect of tropical cyclones (TCs) on cases of heavy rainfall during the Baiu season in Kyushu, Japan using data analyses and numerical experiments. A detailed analysis of the heavy rainfall event that occurred on 7 June 1999 (JST) is performed. This event was remotely affected by Typhoon Maggie (9903), which was located approximately 2000 km from Kyushu at the time. As Typhoon Maggie passed close to Taiwan, a high potential vorticity (PV) zone appeared to the north of Taiwan. A low PV region formed simultaneously to the east of Taiwan, corresponding to a northwestward extension of the Pacific high. These dynamical changes induced an enhanced southerly moisture flux between the high PV zone and the low PV region, leading to moisture convergence and heavy rain in the vicinity of Kyushu. During this time, Typhoon Maggie also caused the northward advection of a separate tropical disturbance.The high PV zone to the north of Taiwan was produced by diabatic heating associated with interplay between the circulation of Typhoon Maggie and the topography of Taiwan. In contrast, the low PV region was formed through the advection of low-PV air from low latitudes by Typhoon Maggie. A piecewise PV inversion diagnostic shows that the low PV region was the largest contributor to the southerly moisture flux, although both Typhoon Maggie and the high PV zone also made positive contributions. Numerical experiments reveal that the precipitation in and around Kyushu was enhanced by both the topography of Taiwan and the northward advection of the additional tropical disturbance.This study identifies a new mechanism as an indirect effect of TCs. The core element of this mechanism is a large moisture flux south of Kyushu, which is termed “moisture road,” and the difference from “atmospheric river” is discussed. This mechanism is not unique to Typhoon Maggie, as other cases of heavy rainfall in and around Kyushu are associated with similar situations.

著者

Fumiaki FUJIBE Nobuo YAMAZAKI Kenji KOBAYASHI

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.84, no.6, pp.1033-1046, 2006 (Released:2007-01-22)

参考文献数

26

被引用文献数

43 59

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Long-term changes in the intensity and frequency of heavy precipitation in Japan were analyzed using quality checked daily precipitation data at 51 stations from 1901 to 2004. The analysis is based on ten categories defined from precipitation intensity and frequency, and some indices of heavy precipitation, such as ≥100 mm days, the annual maximum, and the top 100 cases during the 104 years. The result indicates that heavy precipitation based on these indices has increased during the 104 years. The linear trend of precipitation corresponding to the upper 10% is 2.3% per decade, and that of the number of top 100 cases is 2.6% per decade on the average over the stations. The increase is most pronounced in western Japan and in autumn, while weak, but similar signals are found in other regions and seasons as well. However, no increasing trend is found for less intense precipitation, such as ≥50 mm days and the number of top 1000 cases.Analysis was also made for 5, 11, and 31 day precipitations, and some indices of dry weather. It is found that the frequency of dry weather has increased during the 104 years. The number of days with precipitation less than 1 mm has increased in all the seasons and regions, with a trend of 0.4-0.7% per decade on the average, while the lower 1% ofcases of 31-day precipitation have doubled with a trend of 10% per decade.

著者

David J. Karoly Brian J. Hoskins

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.60, no.1, pp.109-123, 1982 (Released:2007-10-19)

参考文献数

34

被引用文献数

84 122

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幾何光学およびゆっくり変化する媒質中の波動伝播論における光路追跡(ray tracing)の考え方を大気中のプラネタリー波伝播の研究に応用した。線形化した球面上の準地衡風ポテンシャル渦度方程式の解法に波動の運動学理論を適用する。子午断面内のプラネタリー波の伝播を支配する指数を定義し,波動活性量(wave activity:エネルギーに類似し,平均流変化のある場合にも保存する量)が,この指数の大きくなる方に向けて屈折されることを示す。

著者

Yuhei Takaya

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.15A-010, (Released:2019-07-08)

被引用文献数

15

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The western North Pacific (WNP) exhibited markedly enhanced tropical cyclone (TC, typhoon) activity during the boreal summer (June–August) of 2018; 18 named typhoons were generated and 13 of these approached near Japan, causing serious damage and disruption in the country. During the summer of 2018, warm sea surface temperature persisted over the tropical Northeastern Pacific, which are typical oceanic conditions of a positive phase of the Pacific meridional mode (PMM), while no El Niño condition was observed. The Japan Meteorological Agency seasonal forecast system successfully predicted the enhanced TC activity in the WNP as well as associated seasonal characteristics such as a deep monsoon trough and active convection. Results of sensitivity experiments clearly indicate that the positive phase of the PMM played a major role in establishing the active TC conditions in the WNP during the summer of 2018 and reveal predictable seasonal processes of TC activity (genesis and tracks) during the summer of 2018, when there was no El Niño.

著者

Mayuko ODA Hirotada KANEHISA

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.88, no.2, pp.227-238, 2010 (Released:2010-05-22)

参考文献数

12

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On the basis of buoyancy-vorticity (BV) formulation of Harnik et al. (2008), the initial value problem of vertically propagating gravity waves is analytically solved in a zonal-vertical two-dimensional system. The analytical solutions provide an example of the visualization of BV thinking. Further, the analytical solutions enable a qualitative understanding of the growth of gravity waves in a vertically sheared zonal flow (so-called shear instability of gravity waves) by BV thinking. To this end, the basic buoyancy (i.e., basic potential temperature) is assumed to be piecewise uniform in the vertical direction, and the Green function method is employed. The obtained analytical solutions show the following. In a vertically uniform basic zonal flow, the gravity wave, which is initially at the lowest level, propagates vertically upwards, gets reflected from the highest level back to the lowest level and again from the lowest level to the highest level, and so on. In a vertically sheared basic zonal flow, the behavior of the gravity waves depends on the horizontal wave number. This is caused by the dependence of horizontal propagation velocity on the horizontal wave number. Here, horizontal propagation is defined relative to the fluid. If the horizontal propagation and advection by the basic zonal flow are successfully balanced so that the lower and upper phase velocities are nearly equal, then the gravity wave propagates vertically, and the upper and lower disturbances are phase-locked to each other; this results in an effective interaction between them and in growth as an exponential function of time. On the other hand, if the horizontal propagation and advection by the basic zonal flow are out of balance so that the lower and upper phase velocities are different from each other, then the gravity wave hardly propagates vertically, and the upper and lower disturbances horizontally flow away from each other resulting in an absence of interaction between them and in the oscillation (i.e., no growth). At the marginal points between oscillation and growth, the gravity wave grows as a linear function of time. The behavior of analytical solutions can be qualitatively explained by the BV thinking of Harnik et al. (2008).

著者

圓岡 平太郎

出版者

METEOROLOGICAL SOCIETY OF JAPAN

雑誌

氣象集誌. 第1輯 (ISSN:00261165)

巻号頁・発行日

vol.30, no.8, pp.43-49, 1911

著者

XIN Xiaoge WEI Min LI Qingquan ZHOU Wei LUO Yong ZHAO Zongci

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.2019-043, (Released:2019-04-01)

被引用文献数

3

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Two sets of decadal prediction experiments were performed with Beijing Climate Center climate system model version 1.1 (BCC-CSM1.1) with different initialization strategies. One experiment is relaxing modeled ocean temperature to the Simple Ocean Data Assimilation (SODA) reanalysis data (SODAInit). In the other (EnOI_HadInit) experiment, the modeled ocean temperature were relaxed toward the assimilated ocean data, which were generated by assimilating sea surface temperature (SST) of the Hadley Centre Sea Ice and Sea Surface Temperature (HadISST) data to the ocean model of BCC-CSM1.1 using Ensemble Optimum Interpolation (EnOI) method. Comparisons between EnOI_HadInit and SODAInit hindcasts show that EnOI_HadInit is more skillful in predicting SST over the North Pacific, the southern Indian Ocean, and the North Atlantic. Improved prediction skill is also found for surface air temperature (SAT) over South Europe, North Africa, and Greenland, which is associated with the skillful prediction of the Atlantic multi-decadal oscillation in EnOI_HadInit. EnOI_HadInit and SODAInit are both skillful in predicting East Asian SAT, which is related to their skillful predictions of the tropical western Pacific SST. The result indicates that assimilated data generated by the ocean model of BCC-CSM1.1 with EnOI assimilation provide better initial conditions than SODA reanalysis data for the decadal predictions of BCC-CSM1.1.

著者

LIM Jaechan PARK Hyung-Min

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.2019-041, (Released:2019-03-19)

被引用文献数

1

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In this paper, we propose an H-infinity (H∞) filtering approach for the prediction of bias in post-processing of model outputs and past measurements. This method adopts minimax strategy that is a solution for zero-sum games. The proposed H∞ filtering approach minimizes maximum possible errors whereas a recently common approach that adopts the Kalman filtering (KF) minimizes the mean square errors. The proposed approach does not need the information of noise statistics unlike the method based on the KF, while training process is required. We show that the proposed approach outperforms the method based on the KF in experiments by applying real weather data in Korea.

著者

KUO Tzu-Hsien MURAKAMI Masataka TAJIRI Takuya ORIKASA Narihiro

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.2019-032, (Released:2019-02-02)

被引用文献数

3

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Aluminum oxide (Al2O3) and iron oxide (Fe2O3) particles have been observed not only in industrial areas and their surroundings but also in natural atmospheric environments. These types of aerosols can influence aerosol–cloud interactions. In this study, physico-chemical properties, such as size distribution and ability to act as cloud condensation nuclei (CCN) as well as ice nucleating particles (INPs), of surrogates of ambient Al2O3 and Fe2O3 particles were investigated using a CCN counter, the Meteorological Research Institute’s (MRI’s) cloud simulation chamber, the MRI’s continuous flow diffusion chamber-type ice nucleus counter, and an array of aerosol instruments. The results indicated that their hygroscopicity parameter (κ-value) ranged from 0.01 to 0.03. This range is compatible with that of surrogates of mineral dust particles and is smaller than typical κ-values of atmospheric aerosols. On the other hand, based on their ice nucleation active surface site (INAS) densities, these materials may act as effective INPs via immersion freezing (i.e., ice nucleation triggered by particles immersed in water droplets). In the cloud chamber experiments, Al2O3 and Fe2O3 particles continuously nucleated ice crystals at temperatures < −14°C and < −20°C, respectively. This result indicates that the Al2O3 particles were better INPs than the Fe2O3 particles. Moreover, the INAS density of the Al2O3 particles was comparable to that of natural ambient dust.

著者

TAUVALE Luteru TSUBOKI Kazuhisa

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.2019-042, (Released:2019-04-01)

被引用文献数

7

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Geographic and meteorological characteristics of 479 tropical cyclones (TCs) in a study domain in the Southwest Pacific (defined by 135°E - 120°W and 5°S - 65°S) over the past 48 TC seasons from 1969–1970 to 2016–2017 were examined using the latest Southwest Pacific Enhanced Archive of Tropical Cyclones dataset. Examined metrics include the geographic distributions of TCs, numbers, intensity, length in days (TC days), accumulated cyclone energy (ACE), and power dissipation index (PDI). The results show increasing TC activities in the western, northwestern, northern and central subdomains of the nine subdomains in the study domain. The average latitudes of TC genesis and TC maximum intensity remained almost unchanged. Most of TCs took southward to southeastward paths, and the majority attained their maximum intensities in the western and central parts of the study domain. The annual number of TCs and TC days decreased over the study period, the numbers of stronger TCs slightly increased whereas stronger TC days increased. The highest annual lifetime-maximum intensity and average annual lifetime-maximum intensity also increased. The highest annual maximum intensification rates did not change much over the study period, nor did ACE and PDI. The results show correlations between highest annual lifetime-maximum intensity to the variations of average sea surface temperature (SST) as well as correlations between TC days to the variations of average SST in the region.