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)

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
Thomas Birner John R. Albers
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.13A, no.Special_Edition, pp.8-12, 2017 (Released:2017-07-25)
参考文献数
34
被引用文献数
4

Abrupt breakdowns of the polar winter stratospheric circulation such as sudden stratospheric warmings (SSWs) are a manifestation of strong two-way interactions between upward propagating planetary waves and the mean flow. The importance of sufficient upward wave activity fluxes from the troposphere and the preceding state of the stratospheric circulation in forcing SSW-like events have long been recognized. Past research based on idealized numerical simulations has suggested that the state of the stratosphere may be more important in generating extreme stratospheric events than anomalous upward wave fluxes from the troposphere. Other studies have emphasized the role of tropospheric precursor events. Here reanalysis data are used to define events of extreme stratospheric mean flow deceleration (SSWs being a subset) and events of extreme lower tropospheric upward planetary wave activity flux. While the wave fluxes leading to SSW-like events ultimately originate near the surface, the anomalous upward wave activity fluxes associated with these events primarily occur within the stratosphere. The crucial dynamics for forcing SSW-like events appear to take place in the communication layer just above the tropopause. Anomalous upward wave fluxes from the lower troposphere may play a role for some events, but seem less important for the majority of them.
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)

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

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)

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.
著者
Kotaro BESSHO Kenji DATE Masahiro HAYASHI Akio IKEDA Takahito IMAI Hidekazu INOUE Yukihiro KUMAGAI Takuya MIYAKAWA Hidehiko MURATA Tomoo OHNO Arata OKUYAMA Ryo OYAMA Yukio SASAKI Yoshio SHIMAZU Kazuki SHIMOJI Yasuhiko SUMIDA Masuo SUZUKI Hidetaka TANIGUCHI Hiroaki TSUCHIYAMA Daisaku UESAWA Hironobu YOKOTA Ryo YOSHIDA
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.94, no.2, pp.151-183, 2016 (Released:2016-04-28)
参考文献数
66
被引用文献数
26 124

Himawari-8/9—a new generation of Japanese geostationary meteorological satellites-carry state-of-the-art optical sensors with significantly higher radiometric, spectral, and spatial resolution than those previously available in the geostationary orbit. They have 16 observation bands, and their spatial resolution is 0.5 or 1 km for visible and near-infrared bands and 2 km for infrared bands. These advantages, when combined with shortened revisit times (around 10 min for Full Disk and 2.5 min for sectored regions), provide new levels of capacity for the identification and tracking of rapidly changing weather phenomena and for the derivation of quantitative products. For example, fundamental cloud product is retrieved from observation data of Himawari-8 operationally. Based on the fundamental cloud product, Clear Sky Radiance and Atmospheric Motion Vector are processed for numerical weather prediction, and volcanic ash product and Aeolian dust product are created for disaster watching and environmental monitoring. Imageries from the satellites are distributed and disseminated to users via multiple paths, including Internet cloud services and communication satellite services.
著者
Ryusuke Masunaga Hisashi Nakamura Hirotaka Kamahori Kazutoshi Onogi Satoru Okajima
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.14, pp.6-13, 2018 (Released:2018-01-18)
参考文献数
37

As an additional product of the Japanese 55-year Reanalysis (JRA-55) project, a new global atmospheric reanalysis product, named JRA-55CHS, is under construction. It utilizes quarter-degree sea-surface temperature (SST) as lower-boundary condition with the same data assimilation system as the JRA-55 Conventional (JRA-55C), into which no satellite data is assimilated. The SST data can resolve steep SST gradients along the western boundary currents (WBCs), which are not necessarily well represented in many of the other atmospheric reanalysis products, including the JRA-55C. The present paper briefly documents basic performance of the JRA-55CHS, through comparing it with the JRA-55C and satellite observations in focusing on the major WBC regions. In the JRA-55CHS, mesoscale atmospheric structures along the WBCs are well reproduced in their climatological-mean fields as captured in the satellite observations. Their interannual- to decadal-scale variations associated with SST variations are also reasonably reproduced. The corresponding atmospheric features are less obvious in the JRA-55C owing to smoother SST prescribed. Furthermore, comparison between the two reanalysis products reveals that the influence of frontal-scale SST distributions can reach into the middle and upper troposphere, especially in summer. The JRA-55CHS will be useful for deepening our understanding of the nature of midlatitude frontal-scale air-sea interactions.
著者
WANG Chung-Chieh CHEN George Tai-Jen NGAI Chi-Hong TSUBOKI Kazuhisa
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2018-051, (Released:2018-07-31)

There exists a minor, secondary early-morning peak in mei-yu rainfall climatology along the western coast of Taiwan, and this work investigates one such event on 8 June 2012 in southwestern Taiwan under weak synoptic conditions through both observational analysis and numerical modeling, with the main focus on the triggering mechanism of the convection. Observations show that the convection developed offshore around midnight near the leading edge of a moderate low-level southwesterly wind surge of 15-20 kts, and intensified and moved onshore to produce rainfall. The cold outflow from precipitation also led to new cell development at the backside, and the rain thus lasted for several hours till about 0700 LST. Numerical simulation using a cloud-resolving model at a grid size of 0.5 km successfully reproduced the event development with close agreement with the observations, once a time delay in the arrival of the southwesterly wind surge in initial/boundary conditions (from global analyses) is corrected. Aided by two sensitivity tests, the model results indicate that the convection breaks out between two advancing boundaries, one from the onshore surge of the prevailing southwesterly wind and the other from the offshore land/mountain breeze, when they move to about 40 km from each other. Also, both boundaries are required, as either one alone does not provide sufficient forcing to initiate deep convection in the model. These findings on the initiation of offshore convection in the mei-yu season, interestingly, are qualitatively similar to some cases in Florida with two approaching sea breeze fronts (in daytime over land).
著者
KANG Yunhee JEONG Jong-Hoon YOU Cheol-Hwan LEE Dong-In
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.2018-050, (Released:2018-07-13)

On July 13, 2012, the bow echo was observed over the lee side of the Mt. Halla (1950 m above sea level) on Jeju Island, Korea. Three-dimensional wind-field and surface observation analyses were carried out to understand the structure and evolution of convective system with bow echo on the bell-shaped terrain. The northeastward-moving convective system passed over the approximately bell-shaped, isolated mountain with a mean speed of 17 m s-1. On the windward side of the mountain, the convective system developed by the inflow of unstable warm air from the ocean and terrain-induced upward motion, even with a low CAPE value of 511 J kg-1. When passing the lee side of the mountain, the bow echo was formed in the convective system by the strongest winds behind the bow echo. Behind the leading edge of the bow echo, the strengthened rear-inflow jet (RIJ) descended with relatively dry air along the surface, resulted in enhancing evaporative cooling. The precipitation-induced downdrafts generated a cold pool on the lee side of mountain. The development of an RIJ and cold pool formation both contributed to the evolution of the bow echo. In addition, the isolated bell-shaped terrain had a major indirect influence on the evolution of convective system with bow echo in this event.
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)

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
PUTRI Nurfiena Sagita IWABUCHI Hironobu HAYASAKA Tadahiro
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.2018-020, (Released:2018-01-23)

Two case studies of Mesoscale Convective System (MCS) in Indonesian region were conducted by applying an improved GTG tracking algorithm and ICAS algorithm to Himawari-8 AHI infrared data. The first case over Java Island showed a land-originating MCS in the boreal winter, which coincided with a wet phase of Madden-Julian Oscillation (MJO) over the Maritime Continent. The second case showed the evolution of MCS under the influence of a strong vertical wind shear during the boreal summer. The cloud top height (CTH) of deep convective part in the first case was larger than that in the second case, while the temporal evolution of CTH was similar between two cases. For the anvil part, the median CTH of the second case was relatively stable at around 13 km, while that of the first case showed a considerable temporal variation ranging from 14 to 16 km. The cloud-particle effective radius (CER) of anvil increased after the period of maximum deep convective CTH in both cases, although the CER was slightly larger in the second case than in the first case. These differences in cloud properties between two cases were attributable to the background wind profiles.
著者
CHAN Kelvin T. F. CHAN Johnny C. L.
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.2018-042, (Released:2018-04-27)

This paper presents a summary of some of the observational and numerical studies on the climatology and possible change mechanisms of the outer-core wind structure of a tropical cyclone (TC), which has been generally referred to as size, a term also to be used in this review although various definitions have been given in the literature. In all the ocean basins where TCs exist, TC size has been found to vary with season, year, decade, latitude and longitude. Such variations are related to those in the synoptic flow patterns in which the TCs are embedded. Several factors have been identified to be responsible for changes in TC size, which include environmental humidity, vortex structure, sea surface temperature and planetary vorticity. Each of these factors can modify the transport of lower tropospheric angular momentum into the TC and hence cause changes in its size. The paper ends with a discussion of outstanding issues in the study of the outer-core wind structure of a TC.
著者
WANG Yafei XU Xiaoyu
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.2018-032, (Released:2018-04-07)

The proposed study aims to examine the relation between the Tibetan Plateau (TP) thermal condition and El Niño and Southern Oscillation (ENSO). There were significantly positive correlations between the snow water equivalent (SWE) over the TP from November to next April and sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) in Novmber from 1987 to 2005. SST in EEP in November is most significantly correlated with the TP-SWE in next April, which suggests an accumulative effect of the ENSO on the TP snow cover. Although El Niño conditions could bring anomalous snowfall over the TP by generating a wave train entering the North African-Asian jet, it is questionable if this impact could change the thermal condition over the TP. There was almost no significant negative correlation between the SWE and TP surface temperature (representing the TP thermal condition) in winter. This suggests that the TP thermal condition hardly varies with the anomalous snowfall caused by this ENSO impact, despite some cooling effect of snowfall during the El Niño phase. On the contrary, preceding El Niño conditions tended to be associated with increasing TP surface temperature in May and there were significant positive correlations between SWE in April and TP surface temperature in May and June. ENSO might play a part in affecting TP thermal condition in a way that is quite different from the previous research. A plausible mechanism based on the relation of ENSO-TP thermal condition has been proposed. The mechanism explained the direct and indirect effects of ENSO on the TP thermal condition and role that the seasonal progress can play in this relation. The issues about snow cover aging and the impact of global warming, among others, were also included in the mechanism.
著者
KAWAI Kei KAI Kenji JIN Yoshitaka SUGIMOTO Nobuo BATDORJ Dashdondog
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.2018-023, (Released:2018-01-26)

The Gobi Desert is one of the major sources of Asian dust, which influences the climate system both directly and indirectly through its long-range transport by the westerlies. In this desert, three ground-based lidars are operated in Dalanzadgad, Sainshand, and Zamyn-Uud, Mongolia. This study firstly combined these lidars into a lidar network and shows the spatial development of a dust layer over the desert and the long-range transport of the dust during 22–23 May 2013 via the lidar network. During this dust event, a cold front accompanying an extratropical cyclone moved southeastward across the desert and sequentially passed through Dalanzadgad, Sainshand, and Zamyn-Uud. In Dalanzadgad, in the central part of the desert, a dust storm occurred owing to the strong wind (6–10 m s -1) associated with the cold front and reached a top height of 1.6 km. Some of the dust floated at a height of 0.9–1.6 km along the cold frontal surface. In Sainshand and Zamyn-Uud, in the eastern part of the desert, the dust layer extended from the atmospheric boundary layer (ABL) to the free troposphere in the updraft region of warm air in the cold frontal system. Overall, while the dust layer was moving across the desert with the cold frontal system, it was developing up to the free troposphere. The mechanism of this development can be explained by the combination of two processes as follows: (1) continuous emission of dust from the desert surface to the ABL by the strong wind around the cold front and (2) continuous transport of the dust from the ABL to the free troposphere by the updraft of the warm air in the cold frontal system. This mechanism can contribute to the long-range transport of dust by the westerlies in the free troposphere.
著者
SEINO Naoko ODA Ryoko SUGAWARA Hirofumi AOYAGI Toshinori
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.2018-029, (Released:2018-02-17)
被引用文献数
1

During the Tokyo Metropolitan Area Convection Study for Extreme Weather Resilient Cities (TOMACS) intensive observation period (IOP) in 2011-2013 summers, atmospheric environment of several heavy rainfalls was observed by means of radiosonde soundings in the Tokyo metropolitan area. We investigated formation and development processes of an extremely developed thunderstorm (Case 1 on 26 August 2011) and a moderately developed thunderstorm (Case 2 on 18 July 2013) observed in the TOMACS IOP, utilizing the radiosonde sounding data. Compared to Case 2, the mesoscale environment of the severe storm in Case 1 featured a lower level of free convection and a deeper layer of easterly flow. We carried out numerical simulations to investigate the formation processes of the convective systems in the two cases, using the Non-Hydrostatic Model (NHM) of the Japan Meteorological Agency (JMA) incorporating the Square Prism Urban Canopy (SPUC) scheme. Model results fairly represented the spatial distribution and amounts of the rainfall in both cases. In Case 1, the formation of a distinct convergence zone between easterly and southerly flows was the likely trigger of active convective systems around Tokyo. To further examine the urban impact on precipitation, we performed two comparative simulations, one using realistic current urban surface conditions (CRNT experiment) and the other using less urbanized surface conditions (LURB experiment). The CRNT experiment yielded more rainfall than the LURB experiment in the central urban area. It appears that higher temperatures caused by urbanization can lead to increased rainfall in Tokyo by intensifying convergence and ascending motion.
著者
V. CHANDRASEKAR Haonan CHEN Brenda PHILIPS
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.2018-015, (Released:2018-01-12)
被引用文献数
2

The Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) Dallas-Fort Worth (DFW) Urban Demonstration Network consists of a combination of high resolution X-band radar network and a National Weather Service S-band radar system (i.e., KFWS radar). Based primarily on these radars, CASA has developed end-to-end warning system that includes sensors, software architecture, products, data dissemination and visualization, and user decision making. This paper presents a technical summary of the DFW radar network for urban weather disaster detection and mitigation, from the perspective of tracking and warning of hails, tornadoes, and floods. Particularly, an overview of the X-band radar network design tradeoffs is presented. The architecture and associated algorithms for various product systems are described, including the real-time hail detection system, the multiple Doppler vector wind retrieval system, and the high-resolution quantitative precipitation estimation system. Sample products in the presence of high wind, tornado, hail, and flash flood are provided, and the systems’ performance is demonstrated through cross validation with ground observations and weather reports.
著者
HIRANO Kohin MAKI Masayuki
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.2018-028, (Released:2018-02-24)

This paper reports the development of a very-short-range nowcast system, VIL Nowcast, which aims to provide precise forecasts of imminent rainfall, and in particular, heavy and localized events. The system is based on the vertically integrated liquid water content (VIL), which is estimated from three-dimensional radar observations as well as the 1-minute-resolution rainfall map obtained from the X-band polarimetric (multi-parameter) RAdar Information Network (XRAIN), to predict rainfall amounts over 10 minutes periods that extend to 10--60 minutes into the future. The spatial resolution of VIL Nowcast was 500 m, and nowcasts were produced at a temporal resolution of 5 minutes. Three precipitation events, of which two were isolated storms and one was a synoptic storm, were used as case studies to verify the model. The performance of VIL Nowcast was evaluated against the XRAIN radar rainfall data and an existing rainfall-rate nowcast system using the same advection scheme. The scope of the evaluation was limited mainly to the first prediction for 10 minutes ahead. It was found that VIL Nowcast showed a small, statistically significant improvement over the entire precipitation event, although its skill decreased at longer lead times and at higher thresholds. The key findings of this study are: (1) VIL Nowcast appears capable of generating skillful forecasts at short lead times, even for very localized heavy rainfall; (2) VIL Nowcast can reduce the time lag in the rainfall-rate nowcast system at initiation and peak precipitation; and (3) this system may improve the accuracy of heavy rainfall alerts provided for public activities and emergency alarms.
著者
Robert CIFELLI V. CHANDRASEKAR Haonan CHEN Lynn E. JOHNSON
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.2018-016, (Released:2018-01-12)
被引用文献数
5

An X-band radar system was deployed in Santa Clara, CA from February through May 2016 to support the National Weather Service in the event of potential flooding during one of the largest El Niños on record and to provide better understanding of rainfall processes occurring in the Bay Area. The system was also used to provide high quality precipitation estimation (quantitative precipitation estimation - QPE) for Santa Clara’s urban hydrologic modeling system. Although the Bay Area has coverage from the NEXRAD operational radar network, the combination of topographic influences and proximity to a maritime environment provide unique QPE challenges in this urban region. The X-band radar provided high quality rainfall estimates that performed better than NEXRAD, demonstrating the added value of the X-band system. High resolution rainfall monitoring systems in urban regions also provide a host of benefits across different sectors of the economy, including flood damage mitigation, water quality, water supply, and transportation.