著者

WoonSeon Jung Masataka Murakami Taro Shinoda Masaya Kato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.197-202, 2018 (Released:2018-12-21)

参考文献数

19

被引用文献数

1

---

The Cloud Resolving Storm Simulator (CReSS) model with default parameter settings largely underestimates the diurnal variation of land surface temperature (LST) and hence the formation of summertime diurnal convective clouds over the United Arab Emirates (UAE), which are the primary target of cloud seeding in the UAE. Based on sensitivity experiment results, we optimized a set of land surface parameters to minimize the underestimation of LST and improve the performance of weather simulations over deserts and mountains in the UAE. In the optimized experiment, the difference in LST between Aqua/MODIS observations and CReSS simulation results decreased from 13.0 to 2.3 K under daytime conditions, mainly due to decreased evapotranspiration efficiency and soil thermal diffusivity. Moreover, the difference decreased from 3.8 to 2.0 K under nighttime conditions, mainly due to decreased evapotranspiration efficiency and increased soil temperature at the deepest layer. A decrease in roughness length suppressed the increase in surface air temperature (SAT), contributing to the reproduction of a realistically large difference between LST and SAT during the daytime. The improvement in temperature matching demonstrates that the CReSS model, when used at a 1-km horizontal resolution, accurately simulates the formation of diurnal convective clouds and development of precipitation over deserts in the UAE and low mountains in northeastern UAE.

著者

FUKUI Shin IWASAKI Toshiki SAITO Kazuo SEKO Hiromu KUNII Masaru

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.2018-056, (Released:2018-09-14)

被引用文献数

10

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The feasibility of regional reanalysis assimilating only conventional observations was investigated as an alternative to dynamical downscaling to estimate the past three-dimensional high-resolution atmospheric fields with long-term homogeneity over about 60 years. The two types of widely applied dynamical downscaling approaches have problems. One with a serial long-term time-integration often fails to reproduce synoptic-scale systems and precipitation patterns. The other with frequent reinitializations underestimates precipitation due to insufficient spin-up. To address these problems maintaining long-term homogeneity, we proposed the regional reanalysis assimilating only the conventional observations. We examined it paying special attention to summer precipitation, through one-month experiment before conducting a long-term reanalysis. The system is designed to assimilate surface pressure and radiosonde upper-air observations, using the Japan Meteorological Agency's nonhydrostatic model (NHM) and the local ensemble transform Kalman filter (LETKF). It covers Japan and its surrounding area with a 5-km grid spacing and East Asia with a 25-km grid spacing, applying one-way double nesting in the Japanese 55-year reanalysis (JRA-55). The regional reanalysis overcomes the problems with both types of dynamical downscaling approaches. It reproduces actual synoptic-scale systems and precipitation patterns better. It also realistically describes spatial variability and precipitation intensity. The 5-km grid spacing regional reanalysis reproduces frequency of heavy precipitation and describes anomalous local fields affected by topography such as circulations and solar radiation better than the coarser reanalyses. We optimized the NHM-LETKF for long-term reanalysis by sensitivity experiments. The lateral boundary perturbations derived from an empirical orthogonal function analysis of JRA-55 brings stable analysis, saving computational costs. The ensemble size of at least 30 is needed because further reduction significantly degrades the analysis. The deterministic run from non-perturbed analysis is adopted as first guess in LETKF, instead of the ensemble mean of perturbed runs, enabling reasonable simulation of spatial variability in the atmosphere and precipitation intensity.

著者

YAMASHITA Yousuke NAOE Hiroaki INOUE Makoto TAKAHASHI Masaaki

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.2018-057, (Released:2018-10-05)

被引用文献数

9

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We investigate the effects of the stratospheric equatorial quasi-biennial oscillation (QBO) on the extratropical circulation in the Southern Hemisphere (SH) from SH winter to early summer. The Japanese 55-year Reanalysis (JRA-55) dataset is used for 1960–2010. The factors important for the variation of zonal wind of the SH polar vortex are identified via multiple linear regression, using Equivalent effective stratospheric chlorine (EESC), middle- and lower-stratospheric QBO, solar cycle, El Niño-Southern Oscillation (ENSO), and volcanic aerosol terms as explanatory variables. The results show that the contributions to the SH polar vortex variability of ENSO are important in SH early winter (June) to mid-winter (July), while that of middle-stratospheric QBO is important from spring (September to November) to early summer (December). Analyses of the regression coefficients associated with both middle- and lower-stratospheric QBO suggest an influence on the SH polar vortex from SH winter through early summer in the seasonal evolution. One possible pathway is that the middle-stratospheric QBO results in the SH low-latitudes stratospheric response through the QBO-induced mean meridional circulation, leading to a high-latitude response. This favours delayed downward evolution of the polar-night jet (PNJ) at high latitudes (around 60°S) from late winter (August) to spring (September–November) during the westerly phase of the QBO, consequently tending to strengthen westerly winds from stratosphere to troposphere in SH spring. The other possible pathway involves the response to lower-stratospheric QBO that induces the SH late winter increase in upward propagation of planetary waves from the extratropical troposphere to stratosphere, which is consistent with weakening of the PNJ.

著者

Kenji Suzuki Katsuhiro Nakagawa Tetsuya Kawano Shuichi Mori Masaki Katsumata Fadli Syamsudin Kunio Yoneyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.148-152, 2018 (Released:2018-10-17)

参考文献数

20

被引用文献数

3

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Videosonde observations were conducted at the southwestern coastal region of Sumatra Island, Indonesia, as part of a pilot field campaign of the Years of the Maritime Continent project (Pre-YMC), to investigate the role of solid hydrometeor for precipitation processes in clouds. Videosondes were launched into three types of clouds: convective and stratiform clouds, and a thick upper stratiform cloud with shallow convection at lower level. A quantitative evaluation of the graupel shape data obtained from the videosondes showed different graupel formations in different rain systems. For the typical stratiform cloud, almost no graupel was observed. In contrasts, for the thick upper stratiform clouds with shallow convection, large numbers of ice crystals in the upper layer suggested to act as embryos and form a lot of graupel with the riming of the supercooled droplets that was supposed to be provided from the shallow convection. On the other hand, for the convection case, the videosonde observed spherical graupel just above the freezing level. This suggested that frozen drops acting as embryos formed spherical graupel, which were uplifted by the strong updraft in the convective cloud, and were different from the generally irregular-shaped graupel in the thick upper stratiform cloud.

著者

Guoyu Zhang Jinglin Zhang Jian Shang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.132-137, 2018 (Released:2018-09-19)

参考文献数

25

被引用文献数

9

---

There is growing attention that the contrail by aviation may affect the earth's energy balance and climate change. In this paper, we propose a novel approach, the convolutional neural network model termed ContrailMod, which can be used in contrail classification with Himawari-8 stationary satellite and outperforms the representative conventional algorithm contrail detection algorithm (CDA). We estimate the distribution of potential contrail formation using temperature and specific humidity from ECMWF reanalysis (ERA-Interim) in South China region. According to the convolutional neural network identification (CNNI) and artificial visual inspection (AVI), we adopt the contrail occurrence and persistence (COP) measured from Himawari-8 stationary satellite imagery to evaluate the potential contrail coverage (PCC) fractions of the ECMWF reanalysis data. There is a high correlation between contrail occurrence and persistence and potential contrail coverage. The correlation coefficient of convolutional neural network identification is close to artificial visual inspection, which illustrates that the parameterization is reliable by comparing the observation results and the actual reflection of contrail coverage in parameterization calculation of South China region.

著者

Miho SEKIGUCHI Hironobu IWABUCHI Takashi M. NAGAO Teruyuki NAKAJIMA

出版者

Meteorological Society of Japan

雑誌

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

巻号頁・発行日

pp.2018-007, (Released:2017-12-08)

被引用文献数

2

---

We developed an atmospheric gas absorption table for the Advanced Himawari Imager (AHI) based on the correlated k-distribution (CKD) method with the optimization method, which was used to determine quadrature weights and abscissas. We incorporated the table and band information of the AHI into a multi-purpose atmospheric radiative transfer package, Rstar. We updated the package so that users could easily specify the satellite and band number. Use of this update made it possible for the optimized CKD method to carry out calculations rapidly and accurately. Rstar is easy for beginners to use and facilitates comparison of results. Cloud retrieval tests using different numbers of quadrature points showed that cloud retrievals could be significantly affected by the accuracy of the CKD model.

著者

Kentaro Ishijima Masayuki Takigawa Yousuke Yamashita Hisashi Yashiro Chihiro Kodama Masaki Satoh Kazuhiro Tsuboi Hidekazu Matsueda Yosuke Niwa Shigekazu Hirao

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.111-115, 2018 (Released:2018-08-21)

参考文献数

27

被引用文献数

3

---

Atmospheric radon-222 (222Rn) variability is analyzed and compared with model simulations made by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), with three horizontal resolutions (223, 56, and 14 km), in order to understand high 222Rn events predominantly caused by frontal activities. Seasonal variations of event frequency are well reproduced by the model, with correlation coefficients of 0.79 (223 km) to 0.99 (14 km). The three horizontal resolutions can reproduce general features of the observed peak shapes of events in winter, which dominantly reflect the passage of cold fronts that trap dense amounts of 222Rn. Peak height and width are well reproduced by the 56 km and 14 km resolution models, while the 223 km resolution model shows much lower and broader peaks due to insufficient resolution. We also find that simulations of 222Rn and equivalent potential temperature gradient (|∇θe|) during the events show similar horizontal distributions around the 222Rn observation station, suggesting |∇θe| is a useful tool to understand the variability of atmospheric components around fronts. Consequently, model with horizontal resolution of 56 km and 14 km can well simulate spatiotemporal variations of atmospheric components driven by frontal activities, while 223 km resolution is not enough to reproduce them.

著者

TAKAHASHI Hiroshi G.

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.2018-046, (Released:2018-05-25)

被引用文献数

2

---

This study investigated the absolute values of column-integrated water vapor (precipitable water; PW) in the climate models used in the Coupled Model Intercomparison Project Phase 5 (CMIP5), in terms of the relationships between PW and precipitation characteristics. We identified that global mean PW values are systematically much lower in CMIP5 models than in observations. This dry bias is most profound over the tropical ocean. The dry bias is partly due to biases in sea surface temperatures in the CMIP5-coupled climate models. However, the dry bias is also present in Atmospheric Model Intercomparison Project (AMIP) experiments, which implies the existence of other factors. The relationship between PW and rainfall characteristics shows that rainfall occurs when water vapor levels are lower than in observations, particularly in models with a relatively strong dry bias. This suggests that the reproducibility of rainfall characteristics may be associated with the dry bias.

著者

Sueng-Pil Jung Tae-Yong Kwon So-Ra In Seon-Jeong Kim Geon-Tae Kim Jae-Kwan Shim Chang-Geun Park Byoung-Choel Choi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.86-90, 2018 (Released:2018-07-12)

参考文献数

23

被引用文献数

1

---

The kinetic energy associated with Chang-ma periods was investigated using rawinsonde data from Korea during 2013-2015. Changes in kinetic energy (which is defined in terms of storm relative helicity, SRH) were more pronounced than changes in thermal energy (which is defined in terms of convective available potential energy, CAPE) during precipitation. The median value of SRH increased by 14, 125, and 185 m2 s−2 in no-rain, weak-rain (< 5 mm 3 hr−1), and strong-rain (≥ 5 mm 3 hr−1) time periods, respectively. However, the values of CAPE remained below 100 J kg−1 regardless of the rainfall intensity. Moreover, the correlation coefficients (R) between SRH and precipitation amount about 0.4 with 99% confidence level. In addition, we used two vectors constituting the SRH (storm motion vector and horizontal wind vector) to determine the reason for the SRH differences. The change in the y-components of the horizontal wind vector at low levels (850-750 hPa) was determined to be closely related to SRH. The increase in SRH during the precipitation periods was therefore determined to be due to the low-level southerly wind. Based on these results, we conclude that SRH can be used not only to predict mesoscale storms but also to forecast precipitation in the early summer monsoon season in Korea.

著者

Minghao Yang Ruiting Zuo Liqiong Wang Xiong Chen Yanke Tan Xin Li

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.74-78, 2018 (Released:2018-06-26)

参考文献数

18

被引用文献数

3

---

Based on 55-yr output data from the historical runs of twelve Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) models and a NCEP (National Centers for Environmental Prediction) reanalysis, we evaluate the capability of those models to simulate the interannual variability of the winter North Atlantic storm track (WNAST). It is found that the multi-model ensemble (MME) is better than any single models in reflecting the spatial distribution of WNAST interannual variability and has the smallest root mean square error (RMSE). The strengths of the interannual variations in half of the models are universally weaker than in the NCEP reanalysis. In addition, the simulated interannual variability vary largely among these models in (55°N–65°N, 35°W–0°). MPI-ESM-LR, FGOALS-s2 and MRI-CGCM3 have relatively better abilities than other models to reflect the interannual variability of WNAST strength, longitude and latitude indices respectively. However, the interannual variability of WNAST longitude and latitude indices (strength index) are (is) overestimated (underestimated) in MME.

著者

TAKAHASHI Hiroshi G. DADO Julie Mae B.

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.2018-031, (Released:2018-03-09)

被引用文献数

7

---

We offer a new perspective on a relationship between sea surface temperature (SST) over the windward region of the Philippines and rainfall in the western Philippines during the Asian summer monsoon season, which has been known as the negative correlation, using observational daily SST, rainfall, and atmospheric circulation datasets. This study focuses on the local SST effect rather than the remote effect. A warmer local SST results in greater rainfall over the western Philippines under similar monsoon westerlies conditions, particularly during moderate and relatively stronger monsoon regimes. This result is obtained after selecting only the moderate or relatively stronger monsoon days, because the positive effect of SST on rainfall is masked by the apparent negative correlation between SST and rainfall. The warmer SSTs being associated with less rainfall correspond to weaker cooling by weaker monsoon westerlies and the cooler SSTs being associated with more rainfall correspond to stronger cooling by stronger monsoon westerlies. The cooler SSTs are the result of stronger monsoon cooling and are not the cause of the greater rainfall, which is the apparent statistical relationship. This also implies that the monsoon westerly is the primary driver of the variation in rainfall in this region. We conclude that the local SST makes a positive contribution toward rainfall, although it does not primarily control rainfall. This conclusion can be applicable to coastal regions where, climatologically, rainfall is controlled by winds from the ocean.

著者

Hiroaki Kawase Akira Yamazaki Hajime Iida Kazuma Aoki Wataru Shimada Hidetaka Sasaki Akihiko Murata Masaya Nosaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.39-45, 2018 (Released:2018-03-29)

参考文献数

22

被引用文献数

8

---

Extremely small snow cover in the winter of 2015/16 and interannual variations of snow cover over the Japanese Northern Alps are simulated by a regional climate model with 2 km grid spacing based on the Japanese 55-year Reanalysis (JRA-55). Our simulation well reproduces the daily variation of snow depth along the Tateyama-Kurobe Alpine Route, located at the Japanese Northern Alps, as compared to snow depths observed by time-lapse cameras in 2014/15. Our simulations indicate that the maximum snow depth in 2015/16 was the lowest of 16 years at high elevations, especially in the spring. In March 2016, weak cold air outbreaks and inactive storm-tracks cause little precipitation around central Japan, resulting in greatly reduced annual accumulated snowfall than usual at high elevations. Warmer April conditions also contribute to accelerated snow melting, resulting in the disappearance of snow at high elevations one-month earlier than usual. Analysis of large-scale circulations related to past large El Niño years shows a warmer April is a typical response in El Niño events, while weak cold air outbreaks and inactive storm-tracks are contributed by the extratropical internal variation rather than lingering El Niño effects in tropics.

著者

OKAMOTO Kozo ISHIBASHI Toshiyuki ISHII Shoken BARON Philippe GAMO Kyoka TANAKA Taichu Y. YAMASHITA Koji KUBOTA Takuji

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.2018-024, (Released:2018-02-05)

被引用文献数

8

---

This study evaluated the impact of a future space-borne Doppler wind lidar (DWL) on a super-low-altitude orbit using an observing system simulation experiment (OSSE) based on a sensitivity observing system experiment (SOSE) approach. Realistic atmospheric data, including wind and temperature, was provided as “pseudo-truth” (PT) to simulate DWL observations. Hourly aerosols and clouds that are consistent with PT winds were also created for the simulation. A full-scale lidar simulator, which is described in detail in the companion paper, simulated realistic line-of-sight wind measurements and observation quality information, such as signal-to-noise-ratio (SNR) and measurement error. Quality control (QC) procedures in the data assimilation system were developed to select high-quality DWL observations based on the averaged SNR from strong backscattering in the presence of aerosols or clouds. Also, DWL observation errors used in the assimilation were calculated using the measurement error estimated by the lidar simulator. The forecast impacts of DWL onboard polar- and tropical-orbiting satellites were assessed using the operational global data assimilation system. Data assimilation experiments were conducted in January and August in 2010 to assess overall impact and seasonal dependence. It is found that DWL on either polar- or tropical-orbiting satellites is overall beneficial for wind and temperature forecasts, with greater impacts for the January experiments. The relative forecast error reduction reaches almost 2 % in the tropics. An exception is a degradation in the southern hemisphere in August, suggesting a need to further refine observation error assignment and QC. A decisive conclusion cannot be drawn of the superiority of polar- or tropical-orbiting satellites due to their mixed impacts. This is probably related to the characteristics of error growth in the tropics. The limitations and possible underestimation of the DWL impacts, for example due to a simple observation error inflation setting, in the SOSE-OSSE are also discussed.

著者

UCHIYAMA Akihiro CHEN Bin YAMAZAKI Akihiro SHI Guangyu KUDO Rei NISHITA-HARA Chiharu HAYASHI Masahiko HABIB Ammara MATSUNAGA Tsuneo

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.2018-026, (Released:2018-02-05)

被引用文献数

1

---

The aerosol optical characteristics in the East Asian cities of Fukuoka and Beijing were measured from 2010 to 2014. These long-term season-crossing data were compared to understand the differences between the aerosol characteristics at a source and a downstream region. Previously, few long-term, season-crossing observations have been reported. Using a method developed by one of the present authors, the measurement data were analyzed so that the retrieved optical properties can be more accurate than those obtained in previous studies. Using these data, the aerosol characteristics and their frequency distributions were reliably obtained. In Fukuoka, the annual means of the extinction, scattering, and absorption coefficients Cext (525 nm), Csca (525 nm), and Cabs (520 nm) were 74.6, 66.1, and 8.1 M m−1, respectively, whereas those in Beijing were 412.1, 367.2, and 42.4 M m−1, respectively. The coefficients in Fukuoka were approximately one-fifth of those in Beijing. The single-scattering albedos ω 0 (525 nm) in Fukuoka and Beijing were 0.877 and 0.868, respectively. The asymmetry factors G (525 nm) in the two cities were 0.599 and 0.656, respectively. The extinction Ångström exponents αext in the two cities were 1.555 and 0.855, respectively. The absorption Ångström exponents αabs in the two cities were 1.106 and 0.977, respectively. The fine and coarse mode volume fractions in Fukuoka were approximately 80 % and 20 %, and those in Beijing were both approximately 50 % except in the summer. The Cext , Csca , and Cabs showed seasonal variation in both cities. Some other properties showed also seasonal variation. In particular, the seasonal variation in αabs was clear in both cities; it tended to be small in the summer and large in the winter. The frequency distributions of various parameters were also investigated. The frequency of Cext >500 M m−1 in Fukuoka was very low, and large Cext values were recorded more frequently in the spring than in other seasons. In Beijing, Cext > 1000 M m−1 values were recorded more frequently, and the frequency of 10 M m−1 ≤ Cabs ≤ 60 M m−1 was high in the spring and summer. Furthermore, αabs < 1.0 values were recorded frequently, which cannot be explained by the simple external mixture of absorbing aerosols. To demonstrate the usefulness of the data obtained in this study, the relationships among αabs , αext , the volume size distribution, the imaginary part of the refractive index and ω 0 were investigated, and two characteristic cases in Beijing (winter) and Fukuoka (spring) were preliminarily analyzed.

著者

LONG Jingchao WANG Yuqing ZHANG Suping

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.2018-018, (Released:2018-01-15)

被引用文献数

1

---

The cloud variability and regime transition from-stratocumulus-to-cumulus across the sea surface temperature front in the Kuroshio region over the East China Sea are important regional climate features and may affect the earth’s energy balance. However, because of large uncertainties among available cloud products, it is unclear which cloud datasets are more reliable for use in studying the regional cloud features and to validate cloud simulations in the region by climate models. In this study, the monthly low cloud amount (LCA) and total cloud amount (TCA) datasets in the region from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), Moderate-resolution Imaging Spectroradiometer (MODIS) and International Comprehensive Ocean-Atmosphere Data Set (ICOADS) are validated against the combined product of CloudSat+CALIPSO (CC) in terms of the consistency and discrepancy in the climatologically mean, seasonal cycle, and interannual variation. The results show that LCA and TCA derived from MODIS and CALIPSO present relatively high consistency with CC data in the climatological annual mean and show similar behavior in seasonal cycle. The consistency in LCA between the three datasets and the CC is generally good in cold seasons (winter, spring and fall) but poor in summer. MODIS shows the best agreement with CC in fall with the correlation coefficient of 0.77 at the confidence level over 99%. CALIPSO and MODIS can provide competitive description of TCA in all seasons while ICOADS is good in terms of the climatological seasonal mean of TCA in winter only. Moreover, the interannual variation of LCA and TCA from all datasets is highly correlated with that from CC in both winter and spring with the Matching Score ranging between 2/3 and 1. Further analysis with long-term data suggests that both LCA and TCA from ICOADS and MODIS can be good references for the studies of cloud interannual variability in the region.

著者

Yuki Minamoto Kotaro Nakamura Minrui Wang Kei Kawai Kazuma Ohara Jun Noda Enkhbaatar Davaanyam Nobuo Sugimoto Kenji Kai

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.33-38, 2018 (Released:2018-03-01)

参考文献数

17

被引用文献数

16

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A large-scale dust event occurred in East Asia during early May 2017, and transported dust was measured all over Japan. We performed an analysis of the entire dust event using multiple sources: a local ceilometer measurement, measurements from an optical particle counter in the Gobi Desert (Dalanzadgad, Mongolia), a study of Dust RGB imagery obtained from Himawari-8, lidar measurements from Japan, and meteorological data. Our results show that three extratropical low pressure systems occurred consecutively in Mongolia and generated dust storms in the Gobi Desert. The dust generated by the third low pressure system was transported to Japan by a cold front and two pressure troughs, which were associated with the low pressure system. Remarkably, the Dust RGB imagery shows both the occurrence and the transportation of the dust, and was able to detect two dust outbreaks in the Horqin Sandy Land of Northern China and their transportation to eastern Japan; this shows that the Horqin Sandy Land was one of the source regions of this dust event.

著者

Tsutao OIZUMI Kazuo SAITO Junshi ITO Thoru KURODA Le DUC

出版者

Meteorological Society of Japan

雑誌

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

巻号頁・発行日

pp.2018-006, (Released:2017-11-30)

被引用文献数

9

---

An intense rainband associated with Typhoon 1326 (Wipha) induced a fatal debris flow on Izu Oshima, Japan, on October 15-16, 2013. This rainband formed along a local front between the southeasterly humid warm air around the typhoon and the northeasterly cold air from the Kanto Plain. In this paper, the Japan Meteorological Agency Nonhydrostatic Model was optimized for the “K computer,” and ultra-high-resolution (500-250 m grid spacing) numerical simulations of the rainband with a large domain were conducted. Two of main factors that affect a numerical weather prediction (NWP) model, (1) grid spacing and (2) planetary boundary layer (PBL) schemes [Mellor–Yamada–Nakanishi–Niino (MYNN) and Deardorff (DD)], were investigated. Experiments with DD (Exps_DD: grid spacings of 2 km, 500 m, and 250 m) showed better reproducibility of the rainband position than experiments with MYNN (Exps_MYNN: grid spacings of 5 km, 2 km, and 500 m). Exps_DD simulated distinct convective-scale up/downdraft pairs on the southeast/northwest sides of the front, whereas those of Exps_MYNN were not clear. Exps_DD yielded stronger cold pools near the surface than did Exps_MYNN. These differences in the boundary layer structures likely had a large impact on the position of the front and the associated rainband. Exps_DD with the 500-m grid spacing showed the best precipitation performance according to the Fractions Skill Score. To check other factors of the precipitation forecast, model domain sizes, lateral boundary conditions in nesting simulations, and terrain representations were investigated. In the small domain experiments, the rainband shapes were very different from the observations. In the experiment using a nesting procedure, the deterioration of the forecast performance was acceptably reduced. The model with fine terrains better reproduced the intense rain over the island. These results demonstrate that the ultra-high-resolution NWP model with a large domain has the possibility to improve predictions of heavy rain.

出版者

Meteorological Society of Japan

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:21869057)

巻号頁・発行日

pp.2018-003, (Released:2017-11-16)

被引用文献数

1

著者

岡田 武松

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.32, no.11, pp.478-479, 1913

著者

Yoshiharu IWASA Takashi ARAKAWA Akimasa SUMI

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.1, pp.11-33, 2012-02-29 (Released:2012-02-29)

参考文献数

31

被引用文献数

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Time integration using the Regional Atmospheric Modeling System (RAMS), a non-hydrostatic cloud-resolving model, was performed for 12 days over a low-latitude band (45°S–45°N) circling an aqua planet with 5-km horizontal grid-point intervals. Tropical and subtropical regions with active precipitation and clear sky, respectively, were clearly divided at 10° latitudes. The numerical experiments derived obvious tropospheric mid-level detrainment (TMD) flows near the 0°C level (z ∼ 5 km) out of the tropics into the subtropics. The TMD flows became largest near the border (10° latitude). In this paper, the time-longitudinal mean field was spotlighted and the atmospheric structure accompanying the TMD flow was investigated. When averaged over time and longitude, the subtropical mid-level troposphere, into which the TMD flows move, is approximately in a state of local thermodynamic equilibrium sustained mainly by the balance between the net radiative cooling and adiabatic heating due to mean subsidence flow. Considering the heat balance, a thermodynamic diagnosis of the mean subsidence flow field suggests the following mechanisms for the mean TMD flow: (1) The mean atmosphere near the melting level has stronger radiative cooling and a larger temperature lapse rate than the atmosphere above it. (2) Free subsidence in the mean subtropical mid-level troposphere, which is consistent with the vertical variation of thermal structure and suffers from no direct dynamic forcings, such as buoyancy, involves a vertically mass-divergent layer just above the melting level. (3) The steady poleward mean TMD flow out of the convective tropic atmosphere exists so as to compensate for the vertical mass divergence in the subtropical atmosphere. Because net meridional transports of sensible heat and water vapor in the middle troposphere are influenced by the mean TMD flow, the existence and the maintaining mechanisms of the mean TMD flow could be important elements of the climate system.