著者

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

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.80-85, 2020 (Released:2020-05-13)

参考文献数

25

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

MIYAMOTO Yoshiaki NISHIZAWA Seiya TOMITA Hirofumi

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.2020-023, (Released:2020-02-06)

被引用文献数

2

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The impacts of the number density of cloud condensation nuclei (CCN) and other thermodynamic quantities on moist Rayleigh convection were examined. A numerical model, consisting of a simple two–dimensional equation for Boussinesq air and a sophisticated double moment microphysics scheme, was developed. The impact of the number of CCN is most prominent in the initially formed convection, whereas the convection in the quasi–steady state does not significantly depend on the number of CCN. It is suggested that the former convection is driven by a mechanism without a background circulation, such as parcel theory. In contrast, the latter convection appears to be driven by the statically unstable background layer.  Incorporating the cloud microphysics reduces the integrated kinetic energy and number of convective cell (increases the distance between the cells), with some exceptions, which are consistent with previous studies. These features are not largely sensitive to the number of CCN. It is shown in this study that the reduction in kinetic energy is mainly due to condensation (evaporation) in the upper (lower) layer, which tends to stabilize the fluid. The ensemble simulation shows that the sensitivity of the moist processes to changes the temperature at the bottom boundary, temperature lapse rate, water vapor mixing ratio, and CCN is qualitatively similar to that in the control simulation. The impact becomes strong with increasing temperature lapse rate. The number of convective cell in a domain decreases with the degree of supersaturation or an increase in the domain–integrated condensate.

著者

HOHENEGGER Cathy KORNBLUEH Luis KLOCKE Daniel BECKER Tobias CIONI Guido ENGELS Jan Frederik SCHULZWEIDA Uwe STEVENS Bjorn

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.2020-005, (Released:2019-11-10)

被引用文献数

53

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Basic climate statistics, such as water and energy budgets, location and width of the InterTropical Convergence Zone (ITCZ), trimodal tropical cloud distribution, position of the polar jet and land-sea contrast remain either biased in coarse-resolution General Circulation Models or are tuned. Here we examine the horizontal resolution dependency of such statistics in a set of global convection-permitting simulations integrated with the ICOsahedral Non-hydrostatic (ICON) model, explicit convection and grid spacings ranging from 80 km down to 2.5 km. The impact of resolution is quantified by comparing the resolution-induced differences to the spread obtained in an ensemble of eight distinct global storm-resolving models. Using this metric, we find that, at least by 5 km, the resolution-induced differences become smaller than the spread in 26 out of the 27 investigated statistics. Even for 9 (18) of these statistics, a grid spacing of 80 (10) km does not lead to significant differences. Resolution down to 5 km matters especially for net shortwave radiation, which systematically increases with resolution due to reductions in low cloud amount over the subtropical oceans. Further resolution dependencies can be found in the land-to-ocean precipitation ratio, in the latitudinal position and width of the Pacific ITCZ and in the longitudinal position of the Atlantic ITCZ. Also in the tropics, the deep convective cloud population systematically increases at the expense of the shallow one, whereas the partition of congestus clouds remains fairly constant. Finally, refining the grid spacing systematically moves the simulations closer to observations, but climate statistics exhibiting weaker resolution dependencies are not necessarily associated with smaller biases.

著者

Masahiro Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.12-16, 2020 (Released:2020-01-31)

参考文献数

11

被引用文献数

1

---

The 2015/16 El Niño is compared with the two previous strongest events, the 1982/83 and 1997/98 El Niño. The 2015/16 winter features a basin warming in the Indian Ocean, a negative sea surface temperature (SST) anomaly shifted to the north in the western Pacific Ocean in addition to a positive SST anomaly shifted to the west in the eastern Pacific Ocean. These SST distributions lead to suppressed convection in the Maritime Continent, and to a weakened Hadley circulation in the western Pacific Ocean. The eastern Asian monsoon in the 2015/16 winter was also weakened due to the dominance of the western Pacific (WP) pattern. On the other hand, the third and fourth centers of action of Pacific/North American (PNA) pattern in the 2015/16 case are obscure. This may be due to weak divergence in the eastern Pacific Ocean.

著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-006, (Released:2020-01-21)

被引用文献数

33

---

This study investigated the environmental factors responsible for the development of heavy rainfall in eastern Japan during the passage of Typhoon Hagibis (2019) by using mesoscale gridded analysis data as well as observed data. Environmental indices for diagnosing stability and moisture conditions were examined. It was found that the whole troposphere is almost saturated and the column total water vapor content is extremely large. In the lower troposphere we identified layers of moist absolutely unstable states with the thickness deeper than 2 km. Such deep moist absolutely unstable layers as well as abundant moisture content and almost saturated troposphere set a high potential for convective development. Under these favorable environmental conditions, the fact that the heights of the absolutely unstable layers' bottom are comparable to the mountain elevations is considered to be favorable for topographic lifting of unstable, moist air, which will trigger and activate strong convection and hence heavy rainfall. In spite of a moderate amount of convective available potential energy and a nearly moist-adiabatic lapse rate, moist absolute instability, abundant moisture, and high humidity jointly play a key role to increase the potential for generating the present heavy rainfalls.

著者

UEDA Hiroaki MIWA Kana KAMAE Youichi

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.2018-044, (Released:2018-05-14)

被引用文献数

13

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The response of tropical cyclone (TC) activity to the El Niño-Southern Oscillation (ENSO) and coherent sea surface temperate (SST) anomaly in the Indian Ocean (IO) is investigated with a particular focus on the decaying phase of El Niño. The TC anomalies are obtained from the database for Policy Decision making for Future climate change (d4PDF). This dataset is based on 100-member ensemble simulations for the period of 1951-2010 by use of the state-of-the-art atmospheric general circulation model (AGCM) forced with observed SST as well as the historical radiative forcing. AGCM utilized in the d4PDF is the Meteorological Research Institute Atmospheric General Circulation Model with about 60km horizontal resolution. Our analysis reveals a prolonged decrease in TC frequency over the tropical western Pacific during the post El Niño years until the boreal fall. Dominance of anomalous anticyclone (AAC) over the western Pacific induced by the delayed warming in the tropical Indian Ocean is the main factor for the suppressed TC activity rather than the local SST change. In contrast, the TC number over the South China Sea tends to increase during the post-El Niño fall (September to November). The physical reason can be ascribed to the weakening of AAC associated with the termination of IO warming. Thus we demonstrate that the effect of the IO warming should be taken into account when the ENSO is considered as an environmental factor for predicting TC activity.

著者

Kazuto Takemura Shunya Wakamatsu Hiroki Togawa Akihiko Shimpo Chiaki Kobayashi Shuhei Maeda Hisashi Nakamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.49-54, 2019 (Released:2019-08-09)

参考文献数

21

被引用文献数

1 28

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This study investigates the influence of strong southerly moisture flux on an extreme rainfall event over western Japan in early July 2018, by using a global atmospheric reanalysis dataset. During its peak period from 5 to 7 July, extensive and unprecedented rainfall observed along the well-defined quasi-stationary Baiu front was attributed to two branches of extremely moist inflow from the southern confluence into western Japan. One was a shallow southerly airstream enhanced by the surface North Pacific Subtropical High, and the other was a deeper southwesterly airstream accompanying enhanced convection over the East China Sea. Both the vertically integrated moisture flux from the south and its convergence into western Japan reached the highest levels for 60 years due to an overwhelming contribution from the intensified southerlies. Anomalous diabatic heating associated with the active convection over the East China Sea acted to maintain the southwesterly moisture flux by inducing low-level cyclonic potential vorticity anomalies. During the rainfall event, a strong meander of the upper-level subtropical jet associated with the intensified surface North Pacific Subtropical High accompanied an amplified upper-level trough over the Korean Peninsula, which acted to induce ascent dynamically along the Baiu front.

著者

Akifumi Nishi Hiroyuki Kusaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.17-21, 2019 (Released:2019-02-05)

参考文献数

34

被引用文献数

17

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In this study, we use observational data and numerical models to reveal whether foehn wind affects the record-breaking high-temperature event (41.1°C) at Kumagaya on July 23, 2018. On this day, the weather conditions at Kumagaya satisfied the conditions described in Takane et al. (2014) for a likely extreme high temperature (EHT) day: a “whale-tail” pressure pattern, no precipitation for 6 days, a high potential temperature at 850 hPa, and northerly surface winds. Our back-trajectory analysis shows that the air parcels came to Kumagaya from heights up to 3.0 km above sea level over the Sea of Japan. The Lagrangian energy budget analysis shows that adiabatic heating accounts for about 87.5% of the increase of the thermal energy given to the air parcel, with the rest from diabatic heating. The diabatic heating is caused by heating associated with surface sensible heat flux and the mixing by turbulent diffusion. The adiabatic and diabatic heating are calculated to have raised the temperature of air parcel by 14 and 2.0 K, respectively, for this EHT event. We conclude that the dynamic foehn effect and diabatic heating from the surface, together with mixing in the atmospheric boundary layer, affected the formation of this EHT event.

著者

Daisuke Matsuoka Shiori Sugimoto Yujin Nakagawa Shintaro Kawahara Fumiaki Araki Yosuke Onoue Masaaki Iiyama Koji Koyamada

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.154-159, 2019 (Released:2019-07-23)

参考文献数

19

被引用文献数

7

---

In this study, a stationary front is automatically detected from weather data using a U-Net deep convolutional neural network. The U-Net trained the transformation process from single/multiple physical quantities of weather data to detect stationary fronts using a 10-year data set. As a result of applying the trained U-Net to a 1-year untrained data set, the proposed approach succeeded in detecting the approximate shape of seasonal fronts with the exception of typhoons. In addition, the wind velocity (zonal and meridional components), wind direction, horizontal temperature gradient at 1000 hPa, relative humidity at 925 hPa, and water vapor at 850 hPa yielded high detection performance. Because the shape of the front extracted from each physical quantity is occasionally different, it is important to comprehensively analyze the results to make a final determination.

著者

Shion Sekizawa Takafumi Miyasaka Hisashi Nakamura Akihiko Shimpo Kazuto Takemura Shuhei Maeda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.25-30, 2019 (Released:2019-06-22)

参考文献数

10

被引用文献数

34

---

During a torrential rainfall event in early July 2018, profound enhancement of moisture influx from the south and its convergence occurred over western Japan, which is investigated in this study on the basis of objective analysis and forecast data from the Japan Meteorological Agency Meso-Scale Model. The heavy rainfall over western Japan is found to accompany enhanced oceanic evaporation extensively around Japan, especially around the Kuroshio and entirely over the Sea of Japan. Linear decompositions of the anomalous moisture flux and surface latent heat flux anomalies applied to the high-resolution data reveal that the intensified speed of the low-level southerlies was the primary factor for the pronounced enhancement of both the moisture transport into the heavy rainfall region, especially in its western portion, and evaporation around the Kuroshio into the southerlies. An additional contribution is found from positive sea-surface temperature anomalies to the enhanced southerly moisture inflow into the eastern portion of the rainfall region. These findings have been confirmed through a backward trajectory analysis, which suggests that anomalous moisture supply to air parcels into the rainfall region primarily through the enhanced wind-forced evaporation roughly corresponds to about 10% of the precipitable water anomaly over western Japan.

著者

Koji Terasaki Shunji Kotsuki Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.41-46, 2019 (Released:2019-02-28)

参考文献数

29

被引用文献数

7

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This study investigates the long-term stability of the global atmospheric data assimilation system, incorporating the Local Ensemble Transform Kalman Filter (LETKF) with the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The NICAM-LETKF system assimilates conventional observations, advanced microwave sounding unit–A (AMSU-A) radiances, and global satellite mapping of precipitation (GSMaP) data. The long-term stability of the data assimilation system can be investigated only by running an expensive long-term experiment. This study successfully performed a data assimilation experiment with more than 2 years of data, using the relaxation to prior spread (RTPS) method for covariance inflation. Analysis fields indicate a stable physical performance compared with the ERA-interim data for the entire experimental period.

著者

Haruka Ishizaki Hiroshi Matsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.192-196, 2018 (Released:2018-12-14)

参考文献数

23

被引用文献数

10

---

Radar/Raingauge-Analyzed Precipitation (RA) represents 1 km-grid precipitation after 2006 created by combining radar precipitation and ground precipitation, i.e., Automated Meteorological Data Acquisition System (AMeDAS) of Japan Meteorological Agency along with ground data observed by other organizations. Although RA is slightly greater than ground precipitation, no earlier studies investigated the spatial distribution of this accuracy across Japan using 1 km grid data, as clarified in this study. We selected hourly data of RA and AMeDAS located closest each other, for which miss rates were less than 10% in 2006-2010. We then investigated the distribution of the annual precipitation ratio (RA/AMeDAS). The ratio diverged in the smaller annual precipitation, but converged to ca. 1.2 for larger annual precipitation. By setting the observational area of 46 radars across Japan using Thiessen method, we investigated the relation between the annual precipitation ratio and the distance from the radar to AMeDAS station. We found only negative relation was statistically significant. As a possible reason for this relation, we considered that RA far from the radar is affected by the attenuating and shadowing effect of heavy rainfall near the radar.

著者

Masatake E. Hori Kazuhiro Oshima

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.69-73, 2018 (Released:2018-06-26)

参考文献数

15

被引用文献数

3

---

We use two groups of 100-member ensemble AGCM experiment to investigate the robustness and probabilistic nature of the Warm Arctic/Cold Eurasian (WACE) pattern with or without strong warming SST trend and sea-ice reduction. Model ensembles successfully simulate a distribution of trend coefficients close to that of observation. Results show that the recent trend in WACE pattern is driven by the warming of the Arctic SST, but the pattern itself is not amplified between the warming and non-warming experiment and cannot explain the current cooling trend of the mid-latitudes. We argue that the difference in sea-ice condition regulates the more extreme cases of the pattern thereby contributing to the positive trend in WACE pattern similar to that of observation.

著者

Hironobu IWABUCHI Nurfiena Sagita PUTRI Masanori SAITO Yuka TOKORO Miho SEKIGUCHI Ping YANG Bryan A. BAUM

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.96B, pp.27-42, 2018 (Released:2018-03-16)

参考文献数

35

被引用文献数

44

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An algorithm for retrieving the macroscopic, physical, and optical properties of clouds from thermal infrared measurements is applied to the Himawari-8 multiband observations. A sensitivity study demonstrates that the addition of the single CO2 band of Himawari-8 is effective for the estimation of cloud top height. For validation, retrieved cloud properties are compared systematically with collocated active remote sensing counterparts with small time lags. While retrievals agree reasonably for single-layer clouds, multilayer cloud systems with optically thin upper clouds overlying lower clouds are the major source of error in the present algorithm. Validation of cloud products is critical for identifying the characteristics, advantages, and limitation of each product and should be continued in the future.  As an application example, data are analyzed for eight days in the vicinity of the New Guinea to study the diurnal cycle of the cloud system. The present cloud property analysis investigates cloud evolution through separation of different cloud types and reveals typical features of diurnal cycles related to the topography. Over land, middle clouds increase from 0900 to 1200 local solar time (LST), deep convective clouds develop rapidly during 1200-1700 LST with a subsequent increase in cirrus and cirrostratus cloud amounts. Over the ocean near coastlines, a broad peak of convective cloud fraction is seen in the early morning. The present study demonstrates the utility of frequent observations by Himawari-8 for life cycle study of cloud systems, owing to the ability to capture their continuous temporal variations.

著者

Bh. V. Ramana Murty K. R. Biswas

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.46, no.3, pp.160-165, 1968 (Released:2008-05-27)

参考文献数

9

被引用文献数

2 2

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Experiments on artificial stimulation of clouds using warm cloud seeding technique have been conducted, on randomized basis, from ground for 4 monsoon periods at Jaipur, 6 monsoon periods at Agra and 9 monsoon periods at Delhi, in North India. The seedings were also conducted from aircraft, during one monsoon period at Delhi. Orographic clouds have been seeded for two summer seasons at Munnar in South India.Results have been evaluated on the basis of rainfall amounts obtainedd from raingauges in the respective target and control sectors in each region. Evaluation has also been done on the basis of data obtained by high power microwave radar in the case of a few series of trials conducted at Delhi.A net increase in precipitation was suggested in each area as a result of seeing. The percentage increase in rainfall as a result of ground-based seeding varied from 18.6 to 58.5 according to the area. Statistical evaluation indicated that the results obtained could be significant.

著者

Fumiaki Fujibe Jun Matsumoto Hideto Suzuki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.144-147, 2018 (Released:2018-10-17)

参考文献数

14

被引用文献数

14

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Relationships between daily heat-stroke mortality and temperature were statistically analyzed using Vital Statistics data for 1999 to 2016, with attention to regional differences related to different climate zones. An analysis based on data categorized for each prefecture has revealed that the daily heat-stroke mortality depends not only on daily temperature but also on the summer mean temperature in a way that a prefecture in a cooler summer climate tends to show a higher mortality for a specified value of daily temperature, implying the effect of acclimatization. Additionally, daily heat-stroke mortality is found to be higher for cases of higher temperature on preceding few days to a week, apparently due to accumulated heat stress, but is lower for cases of higher temperature a few weeks ago, presumably due to acclimatization. As for relative humidity, the mortality on a day of higher humidity tends to be higher for a specified value of daily maximum temperature, but lower for a specified value of daily mean temperature. It is also shown that heat-stroke mortality tends to be high on a day of low wind speed and long sunshine hours.

著者

KAWAI Hideaki SHIGE Shoichi

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.2020-059, (Released:2020-08-03)

被引用文献数

3 9

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This review paper aims to provide readers with a broad range of meteorological backgrounds with basic information on marine low clouds and the concept of their parameterizations used in global climate models. The first part of the paper presents basic information on marine low clouds and their importance in climate simulations in a comprehensible way. It covers the global distribution and important physical processes related to the clouds, typical examples of observational and modeling studies of such clouds, and the considerable importance of changes in low cloud for climate simulations. In the latter half of the paper, the concept of cloud parameterizations that determine cloud fraction and cloud water content in global climate models, which is sometimes called cloud “macrophysics”, is introduced. In the parameterizations, the key element is how to assume or determine the inhomogeneity of water vapor and cloud water content in model grid boxes whose size is several tens to several hundreds of kilometers. Challenges related to cloud representation in such models that must be tackled in the next couple of decades are discussed.

著者

加藤 輝之

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.98, no.3, pp.485-509, 2020 (Released:2020-06-20)

参考文献数

50

被引用文献数

19 48

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日本では3時間積算降水量200mmを超える集中豪雨がしばしば観測され、過酷な地滑りや洪水をもたらす。そのような事例は主に、日本語で「線状降水帯」と名付けられた準停滞線状降水システムによってもたらされる。線状降水帯は次々と発生する発達した対流セルが列をなした、組織化した積乱雲群によって、数時間にわたってほぼ同じ場所を通過または停滞することで作り出される、線状に伸びる長さ50~300km程度、幅20~50km程度の強い降水をともなう雨域として定義される。線状降水帯の形成過程としては主に、暖湿流がほぼ停滞している局地前線に流入することで、対流セルが前線上で同時に発生する破線型と、下層風の風上側に新しい対流セルが繰り返し発生し、既存のセルと線状に組織化するバックビルディング型の2つに分類される。 本研究では、線状の降水システムについての過去研究のレビューに加えて、線状降水帯の数値モデルによる再現性および線状降水帯の発生しやすい条件について調査した。2014年8月20日の広島豪雨の事例の再現では、対流セルの形成・発達過程をおおよそ再現できる少なくとも水平解像度2kmが必要であったが、その内部構造を正確に再現するには水平解像度250~500mが必要であった。2㎞のモデルは10時間前の初期値を用いることで広島の事例を量的に再現したが、予想された最大積算降水量は初期時刻が線状降水帯の発生時刻に近づくにつれてかなり減少した。この減少は過度の下層乾燥空気の流入が新たな積乱雲群が発生する領域を移動させたためであった。 線状降水帯を診断的に予測するために、線状降水帯の発生しやすい条件を過去の集中豪雨事例における大気環境場から統計的に構築した。500m高度データをベースに判断する下層水蒸気場を代表して、(1)大量の水蒸気フラックス量(>150g m-2 s-1)と(2)自由対流高度までの距離が短いこと(<1000 m)の2つの条件を選択した。ほかの4つとして、(3)中層(500hPa と 700hPa)の相対湿度が高い(>60%)、(4)ストームに相対的なヘリシティで判断する大きな鉛直シア(>100m2 s-2)、(5)総観スケール(700hPa で空間 400km平均)の上昇流場で判断する上昇流域と(6)700~850hPaに度々みられる暖気移流を除外するための平衡高度が3000m以上の条件を選択した。

著者

MIN Kyeong-Seok TSUBOKI Kazuhisa YOSHIOKA Mayumi K. MORODA Yukie KANADA Sachie

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.2021-017, (Released:2020-12-04)

被引用文献数

3

---

A stationary line-shaped precipitation system (SLPS), which is one type of mesoscale convective systems (MCSs), is a typical heavy-rain-producing weather system formed during warm seasons in Japan. Although the Kinki district, western Japan, is known as a frequent occurrence region for SLPSs, their formation mechanisms in the region have not been sufficiently clarified yet because of their complex formation processes. This study investigated a SLPS event that occurred on 1 September 2015, using observational data and high-resolution numerical experiments. We also carried out numerical sensitivity experiments with regard to the orography and initial time.  The observational data showed that the relative humidity at lower levels was high during the SLPS event. The southwesterly was dominant at middle levels over the Kinki district during the formation of the SLPS. The formation of the SLPS was associated with neither a mesoscale low-pressure system nor a synoptic-scale cold front, demonstrating that these were not necessary conditions for the formation of the SLPS.  In the numerical experiments, we found that the SLPS was formed in a low-level convergence zone of the westerly with the warm and moist south-southwesterly from the Kii Channel. New convective cells formed over the north of Awaji Island and are propagated northeastward by the middle-level southwesterly. This cell formation process was repeated and resulted in the formation of the SLPS. The sensitivity experiments for the orography around the occurrence area of the SLPS indicated that the orography was not a significant factor for the formation of the SLPS in this event. The orography can modify the location of the SLPS.

著者

Hiroshi Takagi Akihiko Ito Heon-Sook Kim Shamil Maksyutov Makoto Saito Tsuneo Matsunaga

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.213-219, 2021 (Released:2021-12-14)

参考文献数

45

被引用文献数

2

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Numerous wetlands, including the world's two largest contiguous wetlands, lie along the free-flowing Paraná and Paraguay Rivers that travel the length of subtropical South America (SSA) region. These wetlands are floodplains that are inundated with rising river water in flood events; their morphology and area are highly changeable with flooding extent. The long-term variability of methane emission from this wetland hotspot and its sensitivity to meteorological conditions are not well known. We herein explore this unknown using space-based estimates of methane flux for the SSA region between 2009 and 2015 along with data of water balance. We find that methane emission from this region coherently varies with precipitation and inundation areal extent.