著者

TOHJIMA Yasunori NIWA Yosuke TSUBOI Kazuhiro SAITO Kazuyuki

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.2022-021, (Released:2021-12-28)

被引用文献数

2

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Synoptic-scale variabilities of atmospheric CO2 and CH4 observed at Yonagunijima (Yonaguni Island, YON, 24.47°N, 123.01°E) during winter (from January to March) in 1998-2020 were examined. The monthly mean variability ratios (ΔCO2/ΔCH4) based on correlation slopes within 24-hour time windows showed a clear increasing trend, which is mainly attributed to the unprecedented increase in the fossil fuel-derived CO2 (FFCO2) emissions from China. A similar increasing trend of the ΔCO2/ΔCH4 ratio had been reported for the observation at Hateruma Island (HAT, 24.06°N, 123.81°E), located at about 100 km east of YON. However, the absolute values for YON were 34 % larger than those for HAT. In addition, the monthly average in February 2020 for YON showed no marked change, while that for HAT showed an abrupt considerable decrease associated with the FFCO2 emission decrease in China presumably caused by the COVID-19 lockdown. Investigating the diurnal variations, we found that the local influences were larger at YON, especially during daytime, than at HAT. Using nighttime data (20-6 LST) and a longer time window (84-hour), we succeeded in reducing the local influences and the resulting monthly mean ΔCO2/ΔCH4 ratio showed considerable similarity to that observed at HAT including the abrupt decrease in February 2020. These results convinced us that the ΔCO2/ΔCH4 ratio could be successfully used to investigate the relative emission strength in the upwind region.

著者

Adam H. Sobel 堀之内 武

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.78, no.2, pp.167-173, 2000-04-25 (Released:2009-09-15)

参考文献数

29

被引用文献数

11 12

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ITCZやモンスーントラフ域で観測される回転性の総観規模風速擾乱の幾つかの側面は、大きなメソスケール対流システムに特徴的な振幅や時・空間スケールを持つパルス的加熱に対する、乾燥・静止大気の線形応答を考えることで理解できることを議論する。その鍵は、短波長のロスビー波の平均流から見た群速度、位相速度は小さいことと、加熱が赤道上よりも赤道から少し離れた位置にあるほうがロスビーモードの応答は遥かに大きなエネルギーを持つことである。故に、観測される擾乱に似た特徴を持つ総観規模ロスビー波は、大きなメソスケール積雲システムが発達する赤道を少し離れた領域に存在するということになる。

著者

SISWANTO Siswanto SCHRIER Gerard van der HURK Bart van den

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.2022-023, (Released:2022-02-08)

被引用文献数

4

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Sub-daily extreme precipitation in Jakarta exhibits trends related to local temperature, seasonal tropical monsoon circulations, and other environmental drivers. Analysis of 81 years of hourly rainfall between 1900-2010 shows a significant increase of about doubling the number of short-duration rainfall events in the wet season. In recent decades, rainfall is found to be higher in intensity and shorter in duration relative to preceding decades. These short-duration rain showers develop typically between afternoon and late night or during early morning hours. Changing short-duration rainfall characteristics throughout the last century are partly attributed to changes in the surface environment of urban Jakarta. A recent temperature increase and land surface drying in the city, in combination with a small increase of the atmospheric moisture content, promote intensified atmospheric convection. A combination of rain gauge data with upper-air observations collected during 2002-2016 reveals that surface warming in the urbanized city accompanied by enhanced availability of moisture results in an increase of convective available potential energy (CAPE), which contributes to enhanced intense precipitation. Super Clausius-Clapeyron scaling (CC) of high-intensity rainfall is attributed to high near-surface temperature and atmospheric moisture content in the morning. This super CC scaling is present in a relatively small range of surface temperature values. Results of this study are in agreement with earlier findings exploring the intensification of extreme morning precipitation and a temporal shift of the diurnal convective maximum from late afternoon to late night/early morning in response to local warming. For a delta city such as Jakarta with abundant convection and heavy precipitation, a well-maintained rainfall database is crucial to assist urban flood early warning.

著者

増山 元三郎

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.15, no.6, pp.215-223, 1937-06-05 (Released:2009-02-05)

参考文献数

8

被引用文献数

1 1

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Je suppose que les postulates fondamentaux en hydrodynamique sont K. I.....K. 10 (§ 1), qui soot été employés par nombreux auteurs explicitement on implicitement pour deduire l'équation de NAVIER-STOKES (1.17).Il y a en § 2 quelques critiques pour les postulates K. I.....K. 10, et on obtient un nonvel terme turbulent fr (2.3). Il faut en conséquence développer le tenseur de viscosité Zrs en série des gradients de vitesse vr, s comme (2.5). Dans le cas du médium isotrope le coefficient de viscosité _??_rsmn n'est pas nécessairement symétrique, et on a un nouvel terme kr (2.7) additivement à côté droit de l'équation (2.11). Si on l'écrit vectoriellement, on obtient (2.9) pour kr comme l'expression vectorielle. J.y donne de plus une nouvelle expression (2.12), qui peut être employée au lieu de relation “Austausch” de Prandtl.On a quelques explications à phenomènes hydrodynamiques biers connues mais non expliqués jusqu'ici (§ 3). Enfin j'étudie sur la fondation d'équation (3.2) quand tourbillon se mouvoit le long de son axe, et explique géométriquement sa condition nécessaire et suffisante.

著者

KUSAKA Hiroyuki NAKAMURA Yusuke ASANO Yuki

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.2022-035, (Released:2022-05-13)

被引用文献数

1

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Ultra Violet (UV) parasols are a reasonable countermeasure against heat stress as they are portable and inexpensive. This study compared the heat stress mitigation effect of a UV parasol with that of street trees and dry-mist spraying on a hot and humid summer day in Japan. We observed meteorological elements and calculated the universal thermal climate index (UTCI) and wet-bulb globe temperature (WBGT) under UV parasol, street trees, dry-mist spraying, and direct sunlight. The observed UTCI and WBGT under the UV parasol were lower than those in direct sunlight by 4.4 and 1.3°C, respectively, because of the decrease in black globe temperature caused by the reduced downward shortwave radiation. This demonstrated that UV parasol reduced heatstroke risk by one level. The effect of the UV parasol was equal to or greater than 75 % of that of the street trees from the perspective of UTCI. The street trees reduced the UTCI and WBGT by 5.9 and 1.9°C, respectively, compared to those in direct sunlight, resulting in the reduction of heatstroke risk by one level. In contrast, dry-mist spraying did not mitigate heat stress in conditions with moderate winds. Although the results of this study were obtained from observations on a single day, comparison with earlier studies confirms that the values observed in this study are representative results on summer days in Japan.

著者

伊藤 耕介

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.321-341, 2022 (Released:2022-04-13)

参考文献数

46

被引用文献数

4

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気象庁の全球日別海面水温解析の準リアルタイム版(以下、R-MGD)では、解析時間の前に得られた観測データに短時間スケールの変動を落とすようなフィルタを適用している。そのため、台風の通過に伴う急激な海面水温の変化がバイアスを生むと考えられる。本研究では、R-MGDの現場観測に対するバイアスを、北西太平洋における台風の通過に沿って定量化した。初めに、2020年8月~9月にかけて立て続けに接近した3つの台風に関し、事例解析を行った。R-MGDは3つの台風の通過直後では2℃以上もの正バイアスを生じており、最後の台風が通過して1週間以上経過したのち負バイアスが観測された。R-MGDと係留ブイの比較を行ったところ、短時間スケールを落とすフィルタリングと解析時間の前に得られたデータを用いていることで、バイアスが説明できた。次に、2015年5月から2020年10月の期間でコンポジット解析を行ったところ、台風最接近の1日前から4日後までに統計的に有意な正バイアス、台風最接近の7日後から14日後までに統計的に有意な負バイアスが、台風から500 kmの範囲内で検出された。正バイアスは、冷たい亜表層の水と激しい台風の通過に伴って生じやすく、とりわけ、黒潮と黒潮続流域を除く中緯度帯で大きくなっていた。また、R-MGDの解析時間の72時間前までに得られた現場観測を追加の最適内挿法で同化することにより、バイアスは軽減されることが分かった。これは、この過程により短周期の変動が復元されたためである。台風予報への影響評価および最適内挿法の独立な観測に対する検証も実施した。

著者

宮本 佳明 筆保 弘徳 和田 章義

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.1, pp.181-196, 2022 (Released:2022-02-22)

参考文献数

48

被引用文献数

6

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中心気圧が960hPaで関東地方に上陸した台風Faxai (1915)に関して、非静力学モデルを用いて格子間隔1kmでの数値シミュレーションを行なった。Faxaiは上陸まで軸対称的な構造を維持し、強風により甚大な被害をもたらした。シミュレーションの結果、上陸前後の48時間の現実的な経路・強度が再現された。計算された強度は上陸まで強く、渦の水平方向の大きさは小さかった。計算されたFaxaiの構造は、熱帯海洋上における発達した熱帯低気圧(TC)のように、軸対称的で目の壁雲が存在していた。中心付近で海面の潜熱フラックスは上陸まで300W m-2を超えていて、高度1.5-12 kmでの鉛直シアーは中緯度としては比較的弱く、9m s-1よりも低かった。 台風の環境場パラメータからポテンシャル強度(MPI)を算出した。計算されたTCの強度もベストトラックの強度も、上陸12時間前からMPIよりも大きいsuperintense状態にあった。これは、内部コア域で超傾度風化していたことによるもので、強い強度や軸対称な構造が原因と考えられる。計算されたTCは、成熟期において傾度風平衡を除いたMPIの式に必要な近似を良く満たしており、これはTCの構造が熱帯で発達したものと類似していたためと考えられる。 今回の解析から、Faxaiは、好ましい環境条件と渦構造によって強い強度を維持したと考えられる。

著者

YULIHASTIN Erma HADI Tri Wahyu ABDILLAH Muhammad Rais FAUZIAH Irineu Rakhmah NINGSIH Nining Sari

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.2022-005, (Released:2021-10-04)

被引用文献数

7

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Early morning precipitation (EMP) events occur most frequently during January and February over the northern coast of West Java and are characterized by propagating systems originating from both inland and offshore. The initial location, direction, and speed of the propagating precipitating system determine the timing of EMP. This study explores processes that characterize such propagating precipitation systems by performing composite analysis and real-case numerical simulations of selected events using the Weather and Research Forecasting (WRF) model with a cloud-permitting horizontal resolution of 3 km. In the composite analysis, EMP events are classified according to the strength of the northerly background wind (VBG), defined as the 925-hPa meridional wind averaged over an area covering western Java and the adjacent sea. We find that under both strong northerly (SN) and weak northerly (WN) wind conditions, EMP is mainly induced by a precipitation system that propagates from sea to land. For WN cases, however, precipitating systems that propagate from inland areas to the sea also play a role. The WRF simulations suggest that mechanisms akin to cold pool propagation and advection by prevailing winds are responsible for the propagating convection that induces EMP, which also explains the dependence of EMP frequency on the strength of VBG. Based on the WRF simulations, we also discuss the roles of sea breeze and gravity waves in the initiation of convection.

著者

松野 太郎

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.44, no.1, pp.25-43, 1966 (Released:2008-05-27)

参考文献数

10

被引用文献数

1371 1997

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コリオリの力が働かなくなる赤道近辺での大規模運動の特性を理論的に検討してみた。自由表面をもった単層の流体-いわゆる発散順圧モデル-について線型化された運動方程式を扱い東西方向に動く自由波動の解を求めると,一定のスケールに対して3つの解が得られた。これらは振動数解の形(圧力及び運動の場)から夫々東向きおよび西向きの慣性重力波およびロスビー波であることがわかる.但し南北スケール最小のものに関してはその区別は明瞭でなく一方の型から他方の型に連続的にかわる。ロスビー波に相当する解は風と圧力の関係が高緯度でほぼ地衡風的であるごと,および赤道近くで特異なふるまいをするのが特徴である。次に同じモデル熱冷源に相当するものとして東西に周期的なmass source,sinkを与え,定常解と求めた。熱源に相当する所は低圧になるが赤道で分断され,赤道のごく近くはやや逆センスになり,これに伴って高緯度と逆向きの強い流れが生ずることが分った。

著者

ROH Woosub SATOH Masaki HOHENEGGER Cathy

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.2021-070, (Released:2021-08-24)

被引用文献数

12

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We intercompared the cloud properties of the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) simulation output over the Atlantic Ocean. The domain averaged outgoing long-wave radiation (OLR) is relatively similar across the models, but the net shortwave radiation at the top of the atmosphere (NSR) shows large differences among the models. The models capture the triple modes of cloud systems corresponding to shallow, congestus, and high clouds, even though their partition in these three categories is strongly model dependent.The simulated height of the shallow and congestus peaks is more robust than the peak of high clouds, whereas cloud water content exhibits larger intermodel differences than cloud ice.  Furthermore, we investigated the resolution dependency of the vertical profiles of clouds for NICAM (Nonhydrostatic ICosahedral Atmospheric Model), ICON (Icosahedral Nonhydrostatic), and IFS (Integrated Forecasting System). We found that the averaged mixing ratio of ice clouds consistently increased with finer grid spacing. Such a consistent signal is not apparent for the mixing ratio of liquid clouds for shallow and congestus clouds. The impact of the grid spacing on OLR is smaller than on NSR and also much smaller than the intermodel differences.

著者

Bjorn STEVENS Masaki SATOH

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.99, no.6, pp.1393-1394, 2021 (Released:2021-12-24)

参考文献数

10

著者

MURAKAMI Masataka

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.2019-009, (Released:2018-11-05)

被引用文献数

5

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A large amount of snowfall caused by snow clouds over the Sea of Japan sometimes severely affects social and economic activities in Japan. Therefore, snow clouds, which form and develop mainly over the ocean and bring heavy snowfall to populated coastal plains, have long been intensively studied from the perspective of disaster prediction and prevention. Most studies have analyzed data acquired by aerological, meteorological satellite, and radar observations, or have conducted numerical simulations. Because of the difficulties involved in accessing cloud systems over the ocean, however, few in situ observation data have been available, and up until the middle 1990s, many problems remained unsolved or their analysis and simulation results remained unvalidated. Here, knowledge gained from instrumented aircraft observations made from the middle 1990s through the early 2000s is reviewed, in particular with regard to the development of a convectively mixed boundary layer and the inner structures of longitudinal-mode cloud bands, Japan-Sea polar-air mass convergence zone cloud bands, and a polar low. Unsolved problems relating to the inner structures and precipitation mechanisms of snow clouds and the expected contributions of aircraft observations to further progress in these areas of atmospheric science are also briefly discussed.

著者

Falko JUDT Daniel KLOCKE Rosimar RIOS-BERRIOS Benoit VANNIERE Florian ZIEMEN Ludovic AUGER Joachim BIERCAMP Christopher BRETHERTON Xi CHEN Peter DÜBEN Cathy HOHENEGGER Marat KHAIROUTDINOV 小玉 知央 Luis KORNBLUEH Shian-Jiann LIN 中野 満寿男 Philipp NEUMANN William PUTMAN Niklas RÖBER Malcolm ROBERTS 佐藤 正樹 澁谷 亮輔 Bjorn STEVENS Pier Luigi VIDALE Nils WEDI Linjiong ZHOU

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.99, no.3, pp.579-602, 2021 (Released:2021-06-10)

参考文献数

68

被引用文献数

26

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近年のコンピューターとモデル開発の進歩により、全球ストーム解像モデルの時代が始まり、それに伴って気象や気候予測が一変する可能性を秘めている。本研究では、この新しいクラスのモデルを検証するという一般的なテーマの中で、9つの全球ストーム解像モデルについて、熱帯低気圧(TC)をシミュレートする能力を評価した。その結果、大まかにいえば、これらのモデルは現実的な熱帯低気圧を再現し、熱帯低気圧の強度の正確なシミュレーションを可能とするなど、全球モデルの長年の課題が解消されていることが示された。一方、TCはモデルの設計に強く影響され、全てのモデルはTCの数、強度、大きさ、構造に関して独自のバイアスを持っている。いくつかのモデルは他のモデルよりも優れたTCをシミュレートするが、全ての点で優れたモデルが存在するわけではなかった。全体的な結果は、全球ストーム解像モデルがTC予測の新時代を切り拓くことが可能であることを示しているが、その可能性を最大限に引き出すためには改良が必要である。

著者

宇田 智紀 坂上 貴之 稲津 將 古賀 一基

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.99, no.5, pp.1169-1183, 2021 (Released:2021-10-27)

参考文献数

21

被引用文献数

3

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本論文では500hPaの等高線が作るトポロジー構造を抽出して大気ブロッキング現象の同定を実現するアルゴリズムを提案する。このアルゴリズムは,構造安定な2次元のハミルトンベクトル場の作る流線パターンのトポロジーによる分類理論に基づいて、この流線構造に部分順序根付き木(partially cyclically ordered rooted tree=COT)表現とそれに付随するレーブグラフ(Reeb graph)という木構造を一意に割り当て、それを用いてブロッキング同定を可能にする。この方法は,従来手法に比べて気象学的なパラメータをほとんど利用せずに簡便かつ効果的に大気ブロッキング現象を抽出できる。加えて、従来手法では困難であったオメガ(Ω)型や双極子型といった大気ブロッキングのタイプ(型)を区別することもできる。このアルゴリズムで同定された大気ブロッキングイベントの期間やそのタイプは現業予報で行われている主観的な判断とよく一致する。

著者

TAKATA Kumiko HANASAKI Naota

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.2021-034, (Released:2021-02-22)

被引用文献数

2

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The Minimal Advanced Treatments of Surface Interaction and RunOff (MATSIRO), which has been used as a land-surface scheme in the global climate model, the Model for Interdisciplinary Research On Climate (MIROC), calculates Dunne runoff and base runoff using the TOPography-based MODEL (TOPMODEL). In past experiments that used MATSIRO, the runoff and its response to precipitation were too low compared to observation. We conjectured that those biases could be attributed to the water table's excessive depth. Its depth was diagnosed based on grid-mean soil moisture, using a saturation threshold that was originally set to almost equal the porosity. In this study, sensitivity experiments, in which the threshold was decreased to 75 %, 50 %, 25 %, and less than 13 % of the porosity, were conducted, and the subsequent effects on river flow were investigated in the Chao Phraya River basin, Thailand, as a case study. As a result, both Dunne and base runoff increased along with the response of river flow to precipitation. The simulated river flow matched observations most closely with the threshold of 50 % saturation. In addition, soil moisture and the Bowen ratio also changed significantly with the runoff changes induced by the threshold changes. These results suggested the importance of the relationship between grid-mean soil moisture and groundwater level for TOPMODEL. Preliminary global experiments indicate that the runoff sensitivity might be dependent on climate zone.

著者

SATO Takuto KUSAKA Hiroyuki

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.2021-047, (Released:2021-04-14)

被引用文献数

1

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In this study, we compare the accuracy of five representative similarity metrics in extracting sea level pressure (SLP) patterns for accurate weather chart classification: correlation coefficient, Euclidean distance (EUC), S1-score (S1), structural similarity (SSIM), and average hash. We use a large amount of teacher data to statistically evaluate the accuracy of each metric. The evaluation results reveal that S1 and SSIM have the highest accuracy in terms of both average and maximum scores. Their accuracy does not change even when non-ideal data are used as the teacher data. In addition, S1 and SSIM can reproduce the subjective resemblance between two maps better than EUC. However, EUC reproduces the central position of the signal in a sample case. This study can serve as a reference for identifying the most useful similarity metric for the classification of SLP patterns, especially when using non-ideal teacher data.

著者

Takeshi ENOMOTO Shozo YAMANE 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.93, no.2, pp.199-213, 2015 (Released:2015-05-14)

参考文献数

31

被引用文献数

8 10

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Simple methods are formulated using an ensemble forecast to identify the sensitive initial perturbations that grow in a specified region at the verification time. These methods do not require the tangent-linear or adjoint models, but use an ensemble forecast to obtain approximated solutions. Input to the sensitivity calculation can be any ensemble forecast integrated from initial conditions perturbed with the bred vector, singular vector, or ensemble Kalman filter methods. Two formulations are presented here to approximate the adjoint and singular vector methods using an ensemble forecast. The ensemble singular vector sensitivity, which has already been applied in previous studies, is obtained with a single eigenvector calculation. The ensemble adjoint sensitivity only requires an even simpler matrix-vector multiplication. To validate the formulations, ensemble-based sensitivity analysis has been conducted in a few cases. First, the two methods were applied to identify the sensitive initial perturbations that grow in the verification region over Japan in January and August 2003. The first singular vector mode indeed achieves the largest amplitude at the verification time, but that is not necessarily true after the verification time. Both methods can identify the sensitive regions more specifically than the regions with large ensemble spread in cases with a mid-latitude cyclone and with a tropical cyclone. The monthly-mean sensitivity in January 2003 indicates the effect of Rossby waves and synoptic disturbances in upstream sensitive regions over Siberia, Tibet, and a downstream sensitive region in the north-western Pacific; the sensitivity in August 2003 suggests the influence of the Asian summer monsoon. Next, for an August 2002 storm case in Europe, global 20-km resolution simulations were conducted from the initial conditions perturbed by the ensemble singular vector method to compare with the unperturbed simulation. In the perturbed simulation, the cyclone is deeper by a few hPa in its north-east sector with more precipitation north of the Alps more consistently with observations. These results indicate that reasonable sensitive regions can be identified with our methods.

著者

WU Ying-Jhang LIOU Yu-Chieng LO Yi-Chuan TAI Sheng-Lun CHANG Shao-Fan SUN Juanzhen

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.2021-049, (Released:2021-04-20)

被引用文献数

1

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The evolution of a heavy rainfall event occurred on 19 August 2014 in northern Taiwan is investigated with observed data and analyses from a newly-developed system named IBM_VDRAS, which is based on a four-dimensional Variational Doppler Radar Assimilation System (VDRAS) with the capability to assimilate radar observations and surface station data over a complex terrain by adopting the Immersed Boundary Method (IBM). This event possesses different precipitating processes and track from those frequently observed in that region. From the surface observations and the high spatiotemporal resolution analysis fields generated by IBM_VDRAS, it is found that the rainfall process started with the initiation of two individual convective cells triggered through the interaction between land-sea breeze and terrain in two different cities (Taoyuan and Taipei). The outflow of one of the convective cells developed in Taoyuan City at an earlier time merged with another convective system which grew in Taipei Basin, and provided favorable conditions to intensify the latter. The enhanced major convective cell moved into the Taipei City metropolitan area and produced 80 mm of precipitation within approximately 2.5 h. The kinematic, thermodynamic, and microphysical fields of the convective cells are analyzed in details to explain the mechanisms which helped to maintain the structure of the rainfall system. Sensitivity experiments of quantitative precipitation forecast (QPF) show that the terrains prevent the location of major rainfall from shifting outside of Taipei Basin. By assimilating surface data, the model can better predict the position of the rainfall.

著者

SHIBATA Kiyotaka SAI Ayano

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.2021-019, (Released:2021-01-13)

被引用文献数

2

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The surface meteorological data in Japan, beginning around the 1880s, archived by the Japan Meteorological Agency are analyzed focusing on the long–term trends and variations in humidity and temperature. It is found that the annual–mean temperature trend exhibits statistically significant warming of 1.0-2.5°C century−1 for most stations, while the annual–mean relative humidity shows significantly decreasing trend of −2 % to −12 % century−1 for most stations with small seasonality. On the other hand, the annual–mean mixing ratio trend displays a different spatial distribution compared to the temperature or relative humidity trend. In this study, three types of trends exist: significantly positive and negative values, and virtually zero. Significantly negative trends of about −0.2 to −0.3 g kg−1 century−1 are located approximately in the Pacific side of Honshu from the middle Tohoku through Shikoku to the eastern Kyushu. Significantly positive trends of about 0.2 to 0.4 g kg−1 century−1 are observed over Hokkaido, the western Japan along Sea of Japan, the western Kyushu, and the remote islands including Okinawa. The overall pattern is similar for other seasons except for most of the remote islands in winter. Empirical orthogonal function (EOF) analysis indicates that the linear trends in the annual–mean temperature and relative humidity can be almost explained by the nearly uniform persistent warming and drying of EOF–1 components. On the other hand, for the annual–mean mixing ratio, EOF–2 is almost identical with the linear trend component, although the fraction of EOF–2 (14 %) is much smaller than that of EOF–1 (49 %). In recent years from 1960 to 2018 the mixing ratio and temperature trends are very different from those in the longer period from the 1880s. The mixing ratio trend and the temperature trend increase on average from 0.0 to 0.5 g kg−1 century−1 and from 1.5°C to 2.5°C century−1, respectively.

著者

FENG Lujia ZHANG Tengfei KOH Tieh-Yong HILL Emma M.

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.2021-026, (Released:2021-01-15)

被引用文献数

3

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Using data from the Sumatran GPS Array in Indonesia–a hero network in tectonic and earthquake studies–we study the summer intra-seasonal variability of precipitable water vapor (PWV) over Sumatra in years without strong inter-annual variability. Unlike most other studies that use external meteorological data to derive PWV from GPS (Global Positioning System) signal delays, we use the zenith wet delay (ZWD) time series estimated from a regular geodetic-quality processing routine as a proxy for PWV variations without using auxiliary meteorological data. We decompose the ZWD space-time field into modes of variability using rotated Empirical Orthogonal Function (EOF) analysis, and investigate the mechanisms behind the two most important modes using linear regression analysis both with and without lags. We show that the summer intra-seasonal variability of daily ZWD over Sumatra in 2008, 2016, and 2017 is dominated by the South Asian Summer Monsoon, and further influenced by dry-air intrusions associated with Rossby waves propagating in the Southern Hemisphere midlatitudes. Both active South Asian monsoons and dry-air intrusions contribute to the dryness over Sumatra during northern summer. Our results indicate an intra-seasonal connection between the South Asian and western North Pacific Summer Monsoons: when the South Asian monsoon is strong, it pumps atmospheric water vapor over the eastern Indian Ocean to feed into the western North Pacific monsoon. We also show a tropical-extratropical teleconnection where PWV over the southern Maritime Continent can be modulated by the activity of eastward-traveling Rossby waves in the southern midlatitudes. Our case study demonstrates the use of regional continuously operating GPS (cGPS) networks for investigating atmospheric processes that govern intra-seasonal variability in atmospheric water vapor.