著者

Sujeong Lim Hyo-Jong Song In-Hyuk Kwon

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-025, (Released:2020-07-02)

被引用文献数

1

---

One way of the tropical cyclone (TC) initialization is assimilating the official advisory sea-level pressure observation to specify the initial structures of a TC with the aid of a background error covariance (BEC). In the hybrid four dimensional ensemble- variational data assimilation system, a static BEC explains the geostrophic and cyclostrophic wind-mass balance, and an ensemble BEC expresses the flow-dependent feature. Assimilation of the minimum sea-level pressure using a larger localization length-scale with limited ensemble members yields the closest to the observations at the initial state, but an imbalance in the broad analysis increment distorts geopotential and wind fields. Moreover, the reduced central pressure of TC is rapidly returned to an intensity that a model resolution can represent during the prediction. We introduce the application of final-scale localization (FSL) at the last outer loop with the shortest one to improve the TC initialization. With the aid of FSL, we may conduct the shorter localization length-scale, especially adopted for the TC initialization. As preliminary results, both analysis and prediction become more stable and the large-scale environments are preserved better than in the control experiment.

著者

Yu Someya Yukio Yoshida Shamil Maksyutov

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-027, (Released:2020-07-08)

被引用文献数

2

---

Although wetlands are the largest natural source of atmospheric methane, the amount and variability of methane emissions from wetlands still have large uncertainty. We investigated the local growth rate of the column-averaged methane dry air mole fraction (XCH4) in Siberia where wetlands are widely abundant using 11-year (2009-2019) Greenhouse gases Observing SATellite (GOSAT) data. While the mean growth rate during the summer from the GOSAT observations is 7.2 ppb yr−1 globally, that in West Siberia is 8.4 ppb yr−1. In particular, the growth rates in West Siberia after 2013 is much larger in July and August than in the other months. Moreover, the growth of XCH4 in West Siberia appears to larger than in the other boreal areas. These results imply that methane emissions from wetlands in West Siberia increased during the summer in recent several years.

著者

Hideo Shiogama Rui Ito Yukiko Imada Toshiyuki Nakaegawa Nagio Hirota Noriko N. Ishizaki Kiyoshi Takahashi Izuru Takayabu Seita Emori

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-013, (Released:2020-03-30)

被引用文献数

6

---

The ensemble average projections of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) ensemble show future increases in shortwave radiation at the surface (SW) in Japan. We reveal that the Arctic Oscillation-like atmospheric circulation trends cause cloud cover decreases around Japan, leading to increases in the SW. In many cases, impact assessment studies use the outputs of only a few models due to limited research resources. We find that the four climate models used in the Japanese multisector impact assessment project, S-8, do not sufficiently capture the uncertainty ranges of the CMIP5 ensemble regarding the SW projections. Therefore, the impact assessments using the SW of these four models can be biased. We develop a novel method to select a better subset of models that are more widely distributed and are not biased, unlike the S-8 models.

著者

Yanjie Li

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-016, (Released:2020-04-08)

被引用文献数

1

---

The meridional propagation of Rossby waves links different latitudes. Traditional wave propagation theory is mostly discussed in the non-divergent atmosphere. This work emphasizes the influence of the divergent effect on wave propagation by analyzing wave solutions to the linearized shallow-water quasi-geostrophic potential vorticity equation on the zonal mean flow. Changes in the basic-state quantities and wave solutions generated from consideration of the divergent effect are highlighted. Compared with the non-divergent situation, more waves are allowed to exist and propagate to much higher latitudes in the divergent case. The turning latitudes are generally moved northward when the divergent effect is included. This main conclusion is robust in the idealized super-rotational flow and 300 hPa climatological flows in winter and summer. The divergent effect also tends to slow the speed of wave propagation and favor waves reaching remoter longitudes. These finding implicates Rossby wave propagation with divergent effect may contribute more to the long-distance teleconnection than that in non-divergent case.

著者

Masayuki Takigawa Prabir K. Patra Yutaka Matsumi Surendra K. Dhaka Tomoki Nakayama Kazuyo Yamaji Mizuo Kajino Sachiko Hayashida

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-015, (Released:2020-04-06)

被引用文献数

16

---

The severe air pollution events continue to occur every year during late October and early November in Delhi, forcing air/land traffic disruptions and anxiety in the daily life of the citizens. We analyze the behaviors of the air pollution events in October and November 2019 that arose from the crop-residue burning as seen using remote sensing techniques. Transport pathways and the mean transit time from the fire hotspots are evaluated using the FLEXPART (FLEXible PARTicle dispersion model). Our results suggest that the polluted regions in Delhi are partly influenced by the crop-residue burning. The uncertainty of our evaluation can be attributable to insufficient information on emission sources because the biomass burning emission based on daily-basis fire radiative power (FRP) of Moderate-Resolution Imaging Spectroradiometry (MODIS) is significantly degraded by the existence of hazy clouds. In future, it is desirable to establish a dense measurement network between Punjab and Delhi for the early detection of the source signals of aerosol emissions and their transport in this region. The FLEXPART model simulation shows the transport of emission signals from Punjab to Delhi, which further expands toward the Bengal region within a span of two days.

著者

Satoru Yoshida Sho Yokota Hiromu Seko Tetsu Sakai Tomohiro Nagai

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-008, (Released:2020-02-13)

被引用文献数

9

---

We conducted observation system simulation experiments (OSSE) to investigate the effects of water vapor vertical profiles observed by Raman lidar (RL) on forecasts of heavy precipitation in Hiroshima, Japan, on August 19, 2014 using a local ensemble transform Kalman filter. We employed a simulation result similar to reality as nature-run (NR) and performed two OSSEs. In the first experiment (DaQv), conventional observation data and vertical profiles of water vapor mixing ratio in air (qv) estimated from NR were assimilated. In the second experiment (CNTL), only conventional observation data were assimilated. In DaQv, we assumed that the RL was in the low-level inflow that supplied water vapor to the heavy precipitation in Hiroshima. Assimilating qv for several hours increased qv around the RL observation station, especially at low level. The regions modified by the assimilation of qv moved to Hiroshima by low-level inflow, resulting in 9-hour precipitation being approximately 28% greater than that of CNTL, and was thus closer to that of the NR. The OSSEs suggest that water vapor RL observations on the windward side of the heavy precipitation are a useful approach for improving precipitation forecasts.

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.i-ii, 2020 (Released:2020-01-28)

参考文献数

12

---

Scientific Online Letters on the Atmosphere (SOLA) has been a fully Open Access journal under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License (http://creativecommons.org/ license/by/4.0) since 2018, and has been added in the DOAJ (Directory of Open Access Journals) list. Last year, SOLA has updated the Guide for Authors and renewed its own web site (https://www.metsoc.jp/sola/). In response to the extreme weather events in the summers of 2017 and 2018, SOLA welcomed submissions of paper on the related topics and has published the special edition “Extreme Rainfall Events in 2017 and 2018” as Volume 15A. The published papers cover the large-scale atmospheric and oceanic features of extreme weather in the summer of 2018 (Shimpo et al. 2019; Sekizawa et al. 2019; Takemura et al. 2019; Takaya 2019), the mesoscale environmental properties of the extreme rainfall in July 2018 (Takemi and Unuma 2019), the predictability of extreme weather in the summer of 2018 (Kotsuki et al. 2019; Matsunobu and Matsueda 2019; Kobayashi and Ishikawa 2019), the relationship between a typhoon and the rainfall in July 2018 (Moteki 2019; Enomoto 2019), the use of a gridded precipitation product in investigating extreme rainfalls (Yatagai et al. 2019), and the impacts of global warming on the extreme hot summer in 2018 (Imada et al. 2019). We are growing. SOLA welcomes submission from the international community in meteorology, atmospheric sciences, and the related fields.

著者

Daisuke Hatsuzuka Tomonori Sato Kohei Yoshida Masayoshi Ishii Ryo Mizuta

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-005, (Released:2020-01-16)

被引用文献数

12

---

This study investigated future changes in extreme precipitation associated with tropical cyclones (TCs) around Japan using large ensemble regional climate simulations for historical and +4 K climates. Under the warmer climate, extreme TC precipitation, defined as the 90th percentile value of the maximum daily precipitation derived from each TC (TCP90), is projected to increase throughout Japan from Kyushu to Kanto. We attributed most of the increase in TCP90 to increased atmospheric moisture due to global warming. Furthermore, it was found that TCP90 is projected to increase for all TC intensity categories. However, the projected increase in intense TCs affects TCP90 in only a limited area. Stronger TCs enhance TCP90 over east- and north-facing slopes of mountainous terrain, while TCP90 in most other areas is insensitive to TC intensity. These results suggest that even relatively weak TCs could have potential to produce extreme precipitation that might cause natural disasters.

著者

Udai Shimada Munehiko Yamaguchi Shuuji Nishimura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-001, (Released:2019-12-17)

被引用文献数

8

---

Japan Meteorological Agency (JMA) best track data indicate that the number of rapid intensification (RI) tropical cyclone events in the western North Pacific increased from 1987 to 2018. To clarify whether this increase is due to climatological changes or qualitative changes in the data, the long-term trend of RI events in JMA operational Dvorak data, which have been used as the first guess for best track analysis, was investigated. Because the JMA Dvorak analysis procedure has remained almost unchanged since 1987, the temporal homogeneity of the Dvorak data is expected to be much better than that of the best track data. The results showed no discernable trend in Dvorak-based RI events over the 32 years. Although the frequency distribution of 24-h intensity changes changed slightly in the Dvorak analysis, that of the best track data changed significantly; as a result, the frequency of best track-based RI events increased after 2006. JMA started using microwave satellite imagery for best track analysis in 2006. This change likely affected the temporal homogeneity of the best track data. These results suggest that the increase in best track-based RI events was due mainly to qualitative changes related to advances in observational techniques.

著者

Arata Amemiya Takumi Honda Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-002, (Released:2019-12-28)

被引用文献数

7

---

The observation operator for the Phased Array Weather Radar in the SCALE-LETKF data assimilation system is revisited, and the impact of its improvement on the analyses and forecasts is examined. The observation operator provides a functional relationship between equivalent radar reflectivity factor (Ze) and hydrometeor mass density (W) of each precipitation particle category. The W − Ze relationship is obtained by a radar simulator. This study performs a radiation code calculation with the parameters regarding particle size distribution of graupel consistent with the cloud microphysics scheme in the SCALE model. The newly obtained observation operator provides much stronger sensitivity of graupel mixing ratio to observed Ze compared to the operator originally used in the model. To examine the impact on the SCALE-LETKF analyses and forecasts, an experiment on a 13 July 2013 heavy rain case is performed with the new observation operator and is compared with the previous study. The forecast initiated by the analysis using the new operator shows much more realistic evolution of Ze in the middle troposphere, where a large amount of graupel is located. The overestimation of forecast Ze is significantly alleviated by the new observational operator. The 30-minute forecast of surface precipitation rate is also improved.

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

pp.2019-028, (Released:2019-06-28)

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

Sachie Kanada Hidenori Aiki Kazuhisa Tsuboki Izuru Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-044, (Released:2019-11-07)

被引用文献数

8

---

From 16 to 23 August 2016, typhoons T1607, T1609, and T1611 hit eastern Hokkaido in northern Japan and caused heavy rainfall that resulted in severe disasters. To understand future changes in typhoon-related precipitation (TRP) in midlatitude regions, climate change experiments on these three typhoons were conducted using a high-resolution three-dimensional atmosphere–ocean coupled regional model in current and pseudo-global warming (PGW) climates. All PGW simulations projected decreases in precipitation frequency with an increased frequency of strong TRP and decreased frequency of weak TRP in eastern Hokkaido. In the current climate, snow-dominant precipitation systems start to cause precipitation in eastern Hokkaido about 24 hours before landfall. In the PGW climate, increases in convective available potential energy (CAPE) developed tall and intense updrafts and the snow-dominant precipitation systems turned to have more convective property with less snow mixing ratio (QS). Decreased QS reduced precipitation area, although strong precipitation increased or remained almost the same. Only TRP of T1607 increased the amounts before landfall. In contrast, all typhoons projected to increase TRP amount associated with landfall, because in addition to increased CAPE, the PGW typhoon and thereby its circulations intensified, and a large amount of rain was produced in the core region.

著者

Kenichi Kusunoki Ken-ichiro Arai Hanako Y. Inoue Chusei Fujiwara

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-042, (Released:2019-10-24)

---

On December 11, 2012, a wind gust caused an F0-intensity wind damage in the Shonai area, Yamagata Prefecture, Japan. This paper provides an overview of an anticyclonic misocyclone (i.e., anticyclonic circulation in the Doppler velocity) related to a wind gust from X-band Doppler radar data. The anticyclonic misocyclone was embedded within a cell with a spiral echo diameter of approximately 3-4 km. The misocyclone over the Sea of Japan moved southeastward at a speed of 11 m s−1, made landfall, and passed over the damaged area; this timing is consistent with the Japan Meteorological Agency (JMA) wind damage assessment. Over the damaged area, the diameter of the misocyclone in the Doppler velocity was estimated to be smaller than 893 m, and the peak tangential wind speed and the vorticity of the vortex were estimated to be at least 8 m s−1 and −3.6 × 10−2 sec−1, respectively. This study discusses various possible explanations for the relationship between the misocyclone and wind gust and provides a first overview of a wintertime anticyclonic misocyclone associated with a surface wind gust on the coast of the Sea of Japan and may provide useful insights to the understanding of wintertime vortices.

著者

Akira T. Noda Hiroshi Niino

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.1, pp.5-8, 2005 (Released:2005-01-25)

参考文献数

17

被引用文献数

9 13

---

A major tornado spawned by a supercell is reproduced by a fine-resolution three-dimensional numerical simulation, and its genesis mechanism and structure are clarified. The tornado, which is associated with a maximum vertical vorticity of 0.85 s-1 and a pressure drop of 27 hPa, originates from one of the small-scale vortices on the gust front that forms between a warm moist environmental air and a rain-cooled air produced by the storm. Only the small-scale vortex that develops into a major tornado is located right under the low-level updraft associated with the low-level mesocyclone; the others that fail to develop are not. Several interesting previously-unexamined characteristics of the threedimensional structure of the simulated tornado vortex are also reported.

著者

Teruyuki Kato Kohei Aranami

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.1, pp.1-4, 2005 (Released:2005-01-07)

参考文献数

7

被引用文献数

28 37

---

Localized, band-shaped heavy rainfall was observed over the Niigata-Fukushima area on July 13th 2004 and the over Fukui area on July 18th 2004. Both areas are located on the Japan-Sea side of the Japan Islands. These heavy rainfall events were a result of an intensification of convective instability over the Baiu frontal zone, induced by the inflows of low-level humid air and middle-level dry air. The middle-level air was considerably warm, not colder than the surrounding air. This indicates that the formation factors of heavy rainfall should be examined using convective instability, rather than potential instability.Numerical simulations using a cloud-resolving model with a horizontal grid of 1.5 km were carried out in an attempt to reproduce these heavy rainfall events. The Niigata-Fukushima heavy rainfall was reproduced well, while the Fukui heavy rainfall was not. This failure of the Fukui case could be the result of the uncertain analysis of the wind field over the Sea of Japan that determined the movement of low-level humid air. edevelopment of new observation systems over the sea, where upper-air sounding is seldom operated, are required to improve heavy rainfall predictions and to prevent such failures.

著者

Yan Nie Lijuan Li Yanli Tang Bin Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-038, (Released:2019-09-23)

被引用文献数

11

---

External forcings among the different phases of the Coupled Model Intercomparison Project (CMIP) vary considerably, but their impacts have not been extensively investigated yet. This study compares the impacts of CMIP5 and CMIP6 forcings on model stability and the 20th-century global warming and El-Niño Southern Oscillation (ENSO) based on the Pre-Industrial control (PI-control) and historical runs of the Flexible Global Ocean–Atmosphere–Land System Model: Grid-point Version 2 (FGOALS-g2). Results indicate that CMIP6 forcings result in a larger climate drift and a lower climatological global average surface temperature (GAST) than those of CMIP5 in PI-control runs. In historical runs, stronger 20th-century warming trends occur during the periods 1910-1940 and 1970-2005 using CMIP6 forcings, which are closer to the HadCRUT than those of the CMIP5 forcings simulation. A stronger spurious warming trend in the CMIP6 results in an evolution of GAST that is less consistent with the HadCRUT dataset than that in the CMIP5 during 1940-1970. Among all forcings, GHGs and aerosol forcings play the dominant roles in differences in GAST, particularly in the Northern Hemisphere. In both the PI-control and historical runs, a larger ENSO amplitude and smaller seasonality are simulated in CMIP6 than in CMIP5.

著者

Abd. Rahman As-syakur Keiji Imaoka Kakuji Ogawara Manabu D. Yamanaka Tasuku Tanaka Yuji Kashino I Wayan Nuarsa Takahiro Osawa

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-039, (Released:2019-09-24)

被引用文献数

7

---

We analyzed 3-hourly Tropical Rainfall Measuring Mission multi-satellite analysis (TRMM 3B42) version-7 data for the 17-year period 1998-2014 to investigate seasonal and geographic characteristics of the diurnal rainfall cycle (DRC) over Sumatera, Indonesia. Dividing Sumatera into north, central, and south regions approximately perpendicular to the west coast, we point out for the first time early-afternoon initiation of daily rainfall not only in the Barisan Mountains but also in the east-coastal small islands (ECSIs) such as Bangka and Belitung. Westward and eastward migrations of rainfall areas from the Barisan Mountains are varied with seasons and regions, with the most remarkable being westward during September-October-November (SON) in the central region and the least remarkable occurring during June-July-August (JJA) in the southern region. In the central region, the DRC reaches a distance of ∼700 km off the west coast during SON and of only 200 km during March-April-May (MAM). The other westward migrations from the ECSIs in the central and southern regions (except for JJA) have been confirmed by 5-year hourly Multi-functional Transport Satellite-1R (MTSAT-1R) cloud-top data. The results shown in this paper suggest that the rainfall distribution with respect to coastal distance, varying geographically and seasonally.

著者

Hidekazu Matsueda Rebecca R. Buchholz Kentaro Ishijima Helen M. Worden Dorit Hammerling Toshinobu Machida

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2019-037, (Released:2019-09-06)

被引用文献数

5

---

We analyzed temporal variations of carbon monoxide (CO) in the upper troposphere from 30°N to 30°S observed using instruments aboard commercial airliner flights between Japan and Australia over the period 1993-2016. Here we focused on the CO variations in the Southern Hemisphere (SH) that showed a unique seasonal cycle with an increased CO around October-November every year. The seasonal CO peaks in the SH showed significant interannual variability (IAV), and are notably enhanced in strong El Niño years, especially 1997. The CO enhancements are proportionally associated with CO emissions from Indonesian fires, when compared to the Global Fire Emissions Database (GFED). The IAV of the CO peak anomalies relative to the mean seasonal cycle was assessed by a statistical regression model that uses a combination of multiple climate indices and their interaction terms. We found that over 80% of the CO IAV observed in the upper troposphere could be explained by the model. The largest anomaly in 1997 showed a different CO-climate relationship than the other periods, which could be due to amplification during synchronized climate modes, or include additional influence from other factors such as human activities.

著者

Ryo Onishi Daisuke Sugiyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.235-239, 2017 (Released:2017-12-21)

参考文献数

15

被引用文献数

1 10

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We have proposed a deep convolution neural network (CNN) approach for the accurate estimation of the cloud coverage (CC) from images captured by a consumer camera, i.e., snapshot pictures. This CNN can successfully estimate the CC to within the level of the inherent error in the training dataset. A segmentation-based method using a linear support vector machine (SVM) is shown to be unable to distinguish between water surfaces and the sky, while the present CNN can correctly distinguish between them, possibly because the CNN can understand the positioning of components in the images; the sky is over a water surface. The present CNN can also be applied to photo-realistic computer-graphic (CG) images from numerical simulations. Comparisons between the CNN estimates for camera images and for the CG images can provide useful information for data assimilation, and thus contribute to numerical weather forecasting. The CC is a sort of far-field (remote) information. The present CNN has the potential to allow consumer cameras to be used as remote weather sensors.

著者

Baosheng Li Ruiqiang Ding Jianping Li Yidan Xu Jiao Li

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.52-56, 2018 (Released:2018-04-26)

参考文献数

33

被引用文献数

5

---

The connection between the predictability of the East Asian summer monsoon (EASM) and El Niño-Southern Oscillation (ENSO) has recently attracted widespread attention. Of particular importance is the effect of El Niño and La Niña on EASM predictability. In this paper, the signal-to-noise ratio (SNR) method is used to analyze reanalysis data, and the results show that the EASM potential predictability intensity is much stronger under El Niño forcing than that under La Niña forcing. Meanwhile, the asymmetric response of EASM predictability remains within the Community Atmosphere Model (CAM) simulations. The EASM predictability is quantitatively determined using the nonlinear local Lyapunov exponent (NLLE) method. The EASM predictability limit under El Niño forcing is longer than that for La Niña forcing. Two monsoon indices are used to measure the EASM, the predictability limits of which perform differently because of their particular definitions. However, the asymmetric response of EASM predictability to El Niño and La Niña can be verified using observational data and model experiments.