著者
SAITO Kazuo KUNII Masaru ARAKI Kentaro
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
(Released:2018-02-11)

Local heavy rainfall of about 100 mm h-1 occurred in Tokyo and Kanagawa Prefecture on 26 August 2011. This rain was brought by a mesoscale convective system (MCS) that developed near a stationary front that slowly moved southward. In an analysis using geostationary multi-purpose satellite rapid scan images and dense automated weather station networks, development of the MCS occurred after the merging of sea breezes from the east (Kashima-nada) and the south (Tokyo Bay). Numerical experiments by the Japan Meteorological Agency (JMA) nonhydrostatic model (NHM) with horizontal resolutions of 10 km and 2 km using mesoscale 4D-VAR analysis of JMA for initial conditions tended to predict the position of intense rainfall areas west of observed positions. In the mesoscale ensemble forecast using perturbations from JMA’s one-week global ensemble prediction system (EPS) forecast, some ensemble members showed enhanced precipitation around Tokyo, but false precipitation areas appeared north of the Kanto and Hokuriku Districts. As an attempt to improve the model forecast, we modified the model, reducing the lower limit of subgrid deviation of water vapor condensation to diagnose the cloudiness for radiation. In the modified model simulation, surface temperatures around Tokyo increased by about 1°C and the position of the intense precipitation was improved, but the false precipitation areas in the Hokuriku District were also enhanced in the ensemble member which brought a better forecast than the control run. We also conducted ensemble prediction using a singular vector method based on NHM. One of the ensemble members unstabilized the lower atmosphere on the windward side of the Kanto District and suppressed the false precipitation in the Hokuriku District, and observed characteristics of the local heavy rainfall were well reproduced by NHM with a horizontal resolution of 2 km. A conceptual model of the initiation of deep convection by the formation of a low-level convergence zone succeeding merging of the two sea breezes from the east and south is proposed based on observations, previous studies, and numerical simulation results. In this event, the northerly ambient wind played an important role on the occurrence of the local heavy rainfall around Tokyo by suppressing the northward intrusion of the sea breeze from the south.
著者
Meiji Honda Akira Yamazaki Akira Kuwano-Yoshida Yusuke Kimura Katsushi Iwamoto
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.12, pp.259-264, 2016 (Released:2016-09-22)
参考文献数
17

Synoptic conditions causing an extreme snowfall event in the Kanto-Koshin district occurred on 14-15 February 2014 are investigated through a reanalysis data set. Associated with a developing cyclone passing the south coast of Japan, persistent snowfall exceeding more than 24 hours over the Kofu-Basin resulted in 112 cm snowfall at Kofu. Slow progress of the south-coast cyclone also contributed to the long snowfall duration. An anticyclone developed over the northern Japan (∼1032 hPa) also contributed to this extreme snowfall. This anticyclone brought warm and moist air inflow by southeasterlies forming moisture flux convergence over the Kanto-Koshin district on the morning of 14th when snowfall started in the Koshin district in spite that the south-coast cyclone was located to the south of Kyushu. Further, ageostrophic cold northerlies with high pressure extension from the anticyclone by “cold-air damming (CAD)” would suppress warming with the approaching south-coast cyclone and keep snowfall until the morning of 15th. In other four heavy snowfall events at Kofu, snowfall durations were almost 12 hours. Although anticyclone to the north and CAD were identified in each case, the moisture transport from the southeast was not evident and moisture flux convergence was not formed earlier.
著者
Tetsuya Takemi
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.14, pp.ii-iii, 2018 (Released:2018-01-25)
参考文献数
2

The Editorial Committee of Scientific Online Letters on the Atmosphere (SOLA) gives The SOLA Award to outstanding paper(s) published each year. I am pleased to announce that The SOLA Award in 2017 is going to be presented to the paper by Dr. Hiroaki Miura, entitled with “Coupling the hexagonal B1-grid and B2-grid to avoid computational mode problem of the hexagonal ZM-grid” (Miura 2017), and to the paper by Dr. Daisuke Goto et al., entitled with “Vertical profiles and temporal variations of greenhouse gases in the stratosphere over Syowa Station, Antarctica” (Goto et al. 2017).
著者
Tetsuya Kawano Ryuichi Kawamura
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.14, pp.1-5, 2018 (Released:2018-01-18)
参考文献数
21

To investigate the influence of the distribution of sea ice in the Sea of Okhotsk on the behavior of a severe snowstorm, which occurred in Hokkaido, Japan, on 2 March 2013 and which was associated with an explosive cyclone, three WRF simulations with realistic, reduced, and enhanced sea ice-cover were carried out. A comparison among these experiments reveals that the extent of the sea ice influenced low-level temperatures and winds to the rear of the cyclone center during the development of the explosive cyclone over the Sea of Okhotsk. Sea ice insulates the ocean from heat exchange with the atmosphere. As a result, when the Okhotsk sea ice extent reaches Hokkaido Island, cold air masses from the north traverse the island without first being heated by the ocean. The consequent temperature reduction produces a low-level higher pressure region to the rear of the cyclone center. As a result, a large geopotential gradient is generated just to the rear of the cyclone center, and low-level winds are intensified within this region. Therefore, the Okhotsk sea ice extent reaching Hokkaido Island plays a significant role in lowering temperatures and intensifying winds in the island.
著者
MURAZAKI Kazuyo TSUJINO Hiroyuki MOTOI Tatsuo KURIHARA Kazuo
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.93, no.2, pp.161-179, 2015

We performed a 20-year numerical experiment over the period 1985 to 2004 using a high-resolution North Pacific Ocean General Circulation Model (NPOGCM) and a 20 km-resolution regional climate model (RCM20) to clarify the impact of the Kuroshio large meander (LM) on the climate around Japan. The NPOGCM reproduced the two primary quasi-stationary states, straight path (SP), and large meander (LM), although the periods during which each state prevailed differed from those indicated in the observational data. The NPOGCM result also showed that the Kuroshio LM causes a cold sea surface temperature anomaly to the south of the Pacific coast of the central Japan. Using the result as a lower boundary condition, a continuous numerical integration was performed by the RCM20. An 8-year composite analysis of the atmospheric circulations of the RCM20 simulation for the Kuroshio LM and SP showed that, in both winter and summer, substantial decreases in the upward surface turbulent heat flux, the frequency of precipitation, and the frequency of steep horizontal gradients in equivalent potential temperature over the ocean are caused by the cold sea surface temperature anomaly. Similar effects are evident over the land area of Japan, although they are less intense, at most 20-50 % of magnitude over the cold sea surface temperature anomaly area, and limited to the coastal region on the Pacific Ocean side in the central part of the country.
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
(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
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
(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 or 0

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
Stéphane BÉLAIR Sylvie LEROYER Naoko SEINO Lubos SPACEK Vanh SOUVANLASSY Danahé PAQUIN-RICARD
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
(Released:2017-12-21)

Heavy precipitation fell over Tokyo in the afternoon of 26 August 2011, leading to flooding and major disruptions for the population, businesses, and authorities. Over 150 mm of precipitation was observed over the city center on that day, with hourly accumulations reaching values as high as 90 mm in late afternoon. Numerical forecasts of this case were performed with a 250-m grid spacing version of the Global Environmental Multi-scale (GEM) model in the context of the Tokyo Metropolitan Area Convection Study (TOMACS). Although initialized only from a global 25-km upper-air analysis, results indicate that GEM is able to produce the intense precipitation over Tokyo at about the right location and time. A sensitivity test in which the urban surface scheme is switched off and replaced with tall grass suggests that the urban environment might have had considerable impact on precipitation intensity, but not on its occurrence or its timing. Based on diagnostics from the GEM integrations, the increased intensity of precipitation seems more related to an enhancement of lateral inflow of low-level moist static energy from Tokyo Bay than to augmented surface fluxes of heat and humidity from the city itself. The existence of low-level bands with locally high values of equivalent potential temperature indicates that the additional moist energy is distributed unevenly through the Tokyo area, an aspect of the simulation which is speculated to have directly contributed to the increase in precipitation intensity over the city.
著者
Hironori IWAI Shoken ISHII Seiji KAWAMURA Eiichi SATO Kenichi KUSUNOKI
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.96A, pp.3-23, 2018 (Released:2018-02-19)
参考文献数
61

During the Tokyo Metropolitan Area Convection Study for Extreme Weather Resilient Cities (TOMACS), many isolated convective storms developed in the southern Kanto Plain on August 17, 2012. The aim of this study was to clarify the dynamics leading to the convection initiation of one of them using different remote sensing instruments. Before the convection initiation, a southeasterly flow transported water vapor inland from Tokyo Bay and the well-mixed and a cumulus-cloud-topped convective boundary layer developed. A convergence line in the form of a sea breeze front (SBF) also moved inland from Tokyo Bay. A near-surface air parcel was lifted to its lifting condensation level (LCL) by an updraft in a convergence zone with a 3 km horizontal scale, which formed the west edge of the convergence line. The saturated air parcel at the LCL was then lifted to its level of free convection (LFC) by the updrafts associated with thermals below the cumulus cloud base. A Ku-band radar detected the first echo of hydrometeors about 6 minutes after the air parcel reached its LFC, then the convective cell developed rapidly. When an SBF arriving from Sagami Bay passed under the cell, the updraft over the nose of the SBF triggered a new precipitation cell, but no intensification of the preexisting cell was observed.
著者
Yoshihito SETO Hitoshi YOKOYAMA Tsuyoshi NAKATANI Haruo ANDO Nobumitsu TSUNEMATSU Yoshinori SHOJI Kenichi KUSUNOKI Masaya NAKAYAMA Yuto SAITOH Hideo TAKAHASHI
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.96A, pp.35-49, 2018 (Released:2018-02-19)
参考文献数
16

The relationships between the occurrence of intense rainfall and the convergence of surface winds and water vapor concentration for typical heavy-rainfall cases were examined using data from July to August in 2011-2013, obtained from high-density meteorological observations in Tokyo, Japan. Additionally, the temporal variations in wind convergence and water vapor between days with and without heavy rainfall events were compared. Corresponding to heavy-rainfall areas, the convergence of surface winds tended to increase for several tens of minutes prior to the heavy rainfall. The peak of convergence was observed 10-30 min before the heavy-rainfall occurrence, and convergence continued to increase for approximately 30 min until the convergence peak time. Around the heavy-rainfall area, the increase in the water vapor concentration index coincided with the increase in convergence. From these results, by monitoring the temporal variations and distributions of these parameters using a high-density observation network, it should be possible to predict the occurrence of heavy rainfall rapidly and accurately.
著者
Shin-ichi SUZUKI Takeshi MAESAKA Koyuru IWANAMI Shingo SHIMIZU Kaori KIEDA
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.96A, pp.25-33, 2018 (Released:2018-02-19)
参考文献数
20

X-band dual-polarization (multi-parameter) radars were used to observe a supercell storm that generated an F3 tornado in Ibaraki Prefecture, Japan on 6 May 2012. The observed data collected for this storm clearly exhibited the typical polarimetric features of a supercell storm, such as the ZDR (differential reflectivity) arc, ZDR column, and the KDP (specific differential phase) column, as well as their time evolution. The ZDR arc emerged at 10 to 15 min before the tornadogenesis. The ZDR column appeared approximately 1 h before the formation of the ZDR arc and was intermittent until tornadogenesis. As the ZDR arc appeared, the column became tall and stable and lasted until the dissipation of the tornado. These ZDR signatures of the supercell storm persisted for approximately half an hour.
著者
Ryohei MISUMI Namiko SAKURAI Takeshi MAESAKA Shin-ichi SUZUKI Shingo SHIMIZU Koyuru IWANAMI
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.96A, pp.51-66, 2018 (Released:2018-02-19)
参考文献数
26

Convective storms are frequently initiated over mountains under weak synoptic forcing conditions. However, the initiation process of such convective storms is not well understood due to a lack of observations, especially the transition process from non-precipitating cumuli to precipitating convective clouds. To investigate the initiation process, we conducted observations around the mountains in the Kanto region, Japan on 18 August 2011 using a 35 GHz (Ka-band) Doppler radar and a pair of digital cameras. The evolution of convective clouds was classified into three stages: convective clouds visible but not detected by the Ka-band radar (stage 0), convective clouds detectable by the Ka-band radar with reflectivity below 15 dBZ (stage 1), and convective clouds accompanied by descending echoes corresponding to precipitation (stage 2). During the transition process from stage 1 to stage 2, weak radar echoes rose to the higher level and reflectivity rapidly increased. This phenomenon suggests that drizzle particles produced in a preexisting convective cloud were lifted by a newly developed updraft, and raindrops were formed rapidly by coalescence of the drizzle particles and cloud droplets. This hypothetical process explains the precipitation echo formation in the lower layer frequently observed in the mountainous area in the Kanto region.
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
(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
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
(Released:2018-02-05)

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.