著者

Kentaroh Suzuki Toshihiko Takemura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-040, (Released:2020-11-09)

被引用文献数

2

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The apparent hydrological sensitivity, defined as the global-mean precipitation change per increase of the global-mean temperature, is investigated for scenarios induced by different forcing agents. Simulations with a climate model driven individually by four different climate forcers, i.e. sulfate, black carbon, solar insolation and carbon dioxide (CO2), are analyzed in the context of energy balance controls on global precipitation to explore how different forcing agents perturb different energy components grouped into fast and slow responses. Similarities and differences among the forcing agents are found in ingredients of the tendency contributing to the hydrological sensitivity from various energy budget components. Specifically, the sulfate and solar forcings induce the hydrological sensitivity of ∼3.0%K−1 due to the slow response of radiative cooling whereas the black carbon induces a significantly negative hydrological sensitivity (∼−6.0%K−1) due to the strong atmospheric heating. The CO2-induced hydrological sensitivity is found in between (∼1.2%K−1) as a result from the slow response of radiative cooling and its partial compensation by the atmospheric heating. The findings provide a quantitative basis for interpreting climatic changes of global precipitation driven by a mixture of various natural and anthropogenic forcings.

著者

Hiroshi G. Takahashi Takuya Yamazaki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-035, (Released:2020-09-30)

被引用文献数

2

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This study investigated the impact of sea surface temperature (SST) on a snowfall event of late January 2018 on Kanto, Honshu, Japan, associated with an extratropical cyclone (south-coast cyclone) along the Pacific side, during the Kuroshio large meandering period by a regional atmospheric model. We addressed SST impacts on the snowfall event under almost the same synoptic-scale conditions, such as extratropical cyclone, in a framework of lateral boundary forcing. We conducted control experiments (KLM) with SST of the Kuroshio large mean-dering, and sensitivity experiments (NKLM) prescribed non-Kuroshio large meandering SSTs. Observational results showed that SST anomalies south of Tokai, and east of northern Kanto and Tohoku could be candidates to modify a snowfall event. As simulated results, timings of snowfall and precipitation associated with the extratropical cyclone was reproduced. Unlike what has been suggested, the SST impact south of Tokai on snowfall was not clear. However, the SST east of northern Kanto and Tohoku showed a significant impact. This impact was explained by southward advection of modified air-mass from east of northern Kanto and Tohoku. Additional sensitivity experiments supported this result. This study implies the importance of the SST anomaly east of northern Kanto and Tohoku for snowfall in Tokyo.

著者

THUNDATHIL Rohith SCHWITALLA Thomas BEHRENDT Andreas MUPPA Shravan Kumar ADAM Stephan WULFMEYER Volker

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-049, (Released:2020-07-14)

被引用文献数

7

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The impact of assimilating thermodynamic profiles measured with lidars into the Weather Research and Forecasting (WRF)-Noah-Multiparameterization model system on a 2.5-km convection-permitting scale was investigated. We implemented a new forward operator for direct assimilation of the water vapor mixing ratio (WVMR). Data from two lidar systems of the University of Hohenheim were used: the water vapor differential absorption lidar (UHOH WVDIAL) and the temperature rotational Raman lidar (UHOH TRL). Six experiments were conducted with 1-hour assimilation cycles over a 10-hour period by applying a 3DVAR rapid update cycle (RUC): 1) no data assimilation 2) assimilation of conventional observations (control run), 3) lidar–temperature added, 4) lidar–moisture added with relative humidity (RH) operator, 5) same as 4) but with the WVMR operator, 6) both lidar–temperature and moisture profiles assimilated (impact run). The root-mean-square-error (RMSE) of the temperature with respect to the lidar observations was reduced from 1.1 K in the control run to 0.4 K in the lidar–temperature assimilation run. The RMSE of the WVMR with respect to the lidar observations was reduced from 0.87 g kg−1 in the control run to 0.53 g kg−1 in the lidar–moisture assimilation run with the WVMR operator, while no improvement was found with the RH operator; it was reduced further to 0.51 g kg−1 in the impact run. However, the RMSE of the temperature in the impact run did not show further improvement. Compared to independent radiosonde measurements, the temperature assimilation showed a slight improvement of 0.71 K in the RMSE to 0.63 K, while there was no conclusive improvement in the moisture impact. The correlation between the temperature and WVMR variables in the static-background error-covariance matrix affected the improvement in the analysis of both fields simultaneously. In the future, we expect better results with a flow-dependent error covariance matrix. In any case, the initial attempt to develop an exclusive thermodynamic lidar operator gave promising results for assimilating humidity observations directly into the WRF data assimilation system.

著者

MESINGER Fedor VELJOVIC Katarina

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-050, (Released:2020-06-23)

被引用文献数

6

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While the terrain-following (sigma) system of representing topography in atmospheric models has been dominant for about the last 60 years, already half a century ago problems using the system were reported in areas of steep topography. A number of schemes had been proposed to address these problems. However, when topography steepness exceeds a given limit all these schemes except the vertical interpolation of the pressure gradient begin to use model information that for physical reasons they should not use. A radical departure from the system was that of the step-topography eta; but its attractiveness was reduced by the discovery of the corner separation problem. The shaved-cell scheme, nowadays referred to as cut-cell, was free of that problem, and was tested subsequently in idealized as well as real case experiments with encouraging results. The eta discretization has lately been refined to make it also a cut-cell scheme. Another method referred to usually as Immersed Boundary Method enabling treatment of terrain as complex as urban landscape came from computational fluid dynamics. It was made available coupled to the atmospheric Weather Research and Forecasting model.  Results of recent experiments of the cut-cell Eta driven by European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble members are analyzed. In these experiments, all cut-cell Eta members achieved better verification scores with respect to 250 hPa wind speed than their ECMWF driver members. This occurred when an upper tropospheric trough was crossing the Rocky Mountains barrier. These results are considerably less favorable for the Eta when switched to use sigma, i.e., Eta/sigma, pointing to the benefits of using topography intersecting as opposed to terrain-following systems. But even so the Eta/sigma shows an advantage over its driver members, suggesting that its other features deserve attention.

著者

Hyunuk Kim Baek-Jo Kim Hyoung-Gu Nam Jonghyeok Jeong Jae-Kwan Shim Kyu Rang Kim Seungbum Kim

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.180-184, 2020 (Released:2020-10-17)

参考文献数

22

---

Strong winds are one of the several factors contributing to natural disasters. Although in recent years, the intensity and frequency of strong winds has decreased, different areas are differently affected by such winds; these winds still have the potential to cause adverse impacts on life and property. In Korea, strong winds are also responsible for the incidence of increased number of accidents and forest fires. Therefore, in this study, relationship between wind speed and damage was analyzed, and the threshold value of damage-causing wind speed was estimated. We first analyzed the relationship between wind speed and damage occurrences based on the daily maximum wind speed and daily maximum instantaneous wind speed data, and data on damage related to strong winds. Second, we examined the validity regarding the regional segmentation of the Korean criteria of special weather report for strong winds using the critical success index and cumulative percentile distributions to estimate the damage-causing threshold value for each region. We found that damage resulting from very strong wind speeds in Korea had not occurred in recent times. In addition, considerable damage had occurred because of low-speed wind compared to the current criteria for high wind advisory. However, the incidence of damage was higher when wind speed was stronger than the current criteria for high wind advisory. Based on threshold estimation, the study areas were categorized into areas with high threshold values (coastal, mountainous, and island), and those with low threshold values (inland areas). A notable difference was observed between the threshold values of the two categories of areas. This necessitated the regional segmentation of the criteria of special weather report on strong winds.

著者

Takashi Sekiya Yugo Kanaya Kengo Sudo Fumikazu Taketani Yoko Iwamoto Maki N. Aita Akitomo Yamamoto Katsuhiro Kawamoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-037, (Released:2020-10-15)

被引用文献数

6

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We quantified the global bromine- and iodine-mediated tropospheric ozone loss using global chemical transport model simulations. We tested three datasets of very short-lived substances (VSLS) emissions, three datasets of sea surface iodide concentrations, and an explicit representation of the effects of multi-phase reactions at the air-sea boundary on dry deposition. We then determined optimal model settings based on the evaluation using the ship-borne and aircraft-campaign observations over the ocean. Our evaluation suggested that the explicit representation of multi-phase reaction effects substantially reduced model biases of ozone in the lower troposphere (up to 11%). Moreover, the impacts of using different datasets of VSLS emissions and sea-surface iodide concentrations were relatively small. The global bromine- and iodine-mediated chemical ozone losses were estimated to account for 4% and 17% of the total chemical loss, respectively, while the global iodine-mediated dry deposition loss of ozone was estimated to account for 22% of the global total dry deposition. These bromine- and iodine-mediated ozone losses decreased surface ozone concentrations over the ocean by 10% and 23%, respectively. The observational constraint on model simulations made by this study supports that bromine and iodine substantially impact global tropospheric ozone through atmospheric chemical reactions and dry deposition processes.

著者

Hyunuk Kim Baek-Jo Kim Hyoung-Gu Nam Jonghyeok Jeong Jae-Kwan Shim Kyu Rang Kim Seungbum Kim

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-031, (Released:2020-10-02)

---

Strong winds are one of the several factors contributing to natural disasters. Although in recent years, the intensity and frequency of strong winds has decreased, different areas are differently affected by such winds; these winds still have the potential to cause adverse impacts on life and property. In Korea, strong winds are also responsible for the incidence of increased number of accidents and forest fires. Therefore, in this study, relationship between wind speed and damage was analyzed, and the threshold value of damage-causing wind speed was estimated. We first analyzed the relationship between wind speed and damage occurrences based on the daily maximum wind speed and daily maximum instantaneous wind speed data, and data on damage related to strong winds. Second, we examined the validity regarding the regional segmentation of the Korean criteria of special weather report for strong winds using the critical success index and cumulative percentile distributions to estimate the damage-causing threshold value for each region. We found that damage resulting from very strong wind speeds in Korea had not occurred in recent times. In addition, considerable damage had occurred because of low-speed wind compared to the current criteria for high wind advisory. However, the incidence of damage was higher when wind speed was stronger than the current criteria for high wind advisory. Based on threshold estimation, the study areas were categorized into areas with high threshold values (coastal, mountainous, and island), and those with low threshold values (inland areas). A notable difference was observed between the threshold values of the two categories of areas. This necessitated the regional segmentation of the criteria of special weather report on strong winds.

著者

Ha Pham-Thanh Thanh Ngo-Duc Jun Matsumoto Tan Phan-Van Hoa Vo-Van

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.169-174, 2020 (Released:2020-09-17)

参考文献数

21

被引用文献数

9

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This study investigated rainfall trends and their associations with tropical cyclones (TCs) during the period of 1979-2019, using TC best-track data from the Regional Specialized Meteorological Center Tokyo - Typhoon Center and daily rainfall data from 138 meteorological stations in Vietnam. The radius of influence of TCs on local rainfall was limited to 500 km from TC centers. The average annual number of TCs affecting Vietnam has decreased slightly in the last two decades compared to previous decades. The ratio of TC-induced rainfall to total rainfall attained the highest value of 37.3% in the central region, in July. The temporal distribution of TC-induced rainfall coincided with the frequency of TCs, with an active period from June to November. During 1979-2019, the non-TC rainfall was the main contributor to the change in total rainfall, especially in relation to the decline in the north and the increase in the coastal South Central region. The rainfall trend during the entire period was principally explained by the interdecadal shift in the late 1990s. Rainfall intensity and the number of heavy rainfall days were intensified for total rainfall and non-TC rainfall, indicating that TCs contributed minimally to the changes of extreme rainfall events during 1979-2019.

著者

Narihiro Orikasa Atsushi Saito Katsuya Yamashita Takuya Tajiri Yuji Zaizen Tzu-Hsien Kuo Wei-Chen Kuo Masataka Murakami

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-036, (Released:2020-09-23)

被引用文献数

2

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Since March 2012, multi-year ground-based observation of atmospheric aerosol particles has been carried out in Tsukuba, Japan to characterize the aerosol particle number concentrations (NCs), air mass origin relevance, and specifically, their cloud condensation nuclei (CCN) and ice nucleating particle (INP) characteristics. The CCN NCs at any water supersaturation (SS) exhibit strong seasonality, being higher in winter and lower in summer; this pattern is similar in the polluted urban environment in East Asia and contrary to that in the Pacific coastal region. The hygroscopicity (κ) is generally high in early autumn and low in early summer, likely due to the seasonal difference of synoptic-scale systems. In contrast, the INP NCs and ice nucleation active surface site density (ns) at defined temperature (−15 to −35°C) and SS (0%-5%) lack clear seasonal influence. The average INP NCs and ns in this study were comparable at warmer temperatures and approximately one order of magnitude lower at colder temperatures, compared with those in other urban locations under limited dust impact. Moreover, the ns values were one to four orders of magnitude lower and exhibited weaker temperature dependence than previous parameterizations on mineral dust particles.

著者

Ha Pham-Thanh Thanh Ngo-Duc Jun Matsumoto Tan Phan-Van Hoa Vo-Van

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-029, (Released:2020-08-11)

被引用文献数

9

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This study investigated rainfall trends and their associations with tropical cyclones (TCs) during the period of 1979-2019, using TC best-track data from the Regional Specialized Meteorological Center Tokyo - Typhoon Center and daily rainfall data from 138 meteorological stations in Vietnam. The radius of influence of TCs on local rainfall was limited to 500 km from TC centers. The average annual number of TCs affecting Vietnam has decreased slightly in the last two decades compared to previous decades. The ratio of TC-induced rainfall to total rainfall attained the highest value of 37.3% in the central region, in July. The temporal distribution of TC-induced rainfall coincided with the frequency of TCs, with an active period from June to November. During 1979-2019, the non-TC rainfall was the main contributor to the change in total rainfall, especially in relation to the decline in the north and the increase in the coastal South Central region. The rainfall trend during the entire period was principally explained by the interdecadal shift in the late 1990s. Rainfall intensity and the number of heavy rainfall days were intensified for total rainfall and non-TC rainfall, indicating that TCs contributed minimally to the changes of extreme rainfall events during 1979-2019.

著者

Fumiaki Fujibe

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-030, (Released:2020-08-25)

被引用文献数

8

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Japan underwent a nationwide self-restraint of human activities in spring 2020 to prevent the spread of the COVID-19 infection. In order to evaluate the effect of suppressed human activities on temperature in the Tokyo Metropolitan area, a statistical analysis was made for temperature anomalies during the self-restraint period using hourly data on the AMeDAS network. The temperature anomaly was defined by the departure from the value that would have been observed without self-restraint, estimated from regression analysis for temperatures at surrounding non-urban stations. It was found that the temperature in central Tokyo (Kitanomaru Park) had a negative anomaly of −0.49°C with a 95% confidence range of ±0.19°C on the average over the strong self-restraint period from April to May. The anomaly was larger in the nighttime than in the daytime, and was found in an area spreading for several tens of kilometers, with a decreasing magnitude according to the distance from Tokyo. These facts indicate a possibility that the reduction of anthropogenic heat release during the self-restraint period resulted in substantial decrease of temperature in the Tokyo Metropolitan area.

著者

JIN Kai WANG Fei ZONG Quanli QIN Peng LIU Chunxia

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-040, (Released:2020-05-09)

被引用文献数

6

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Observed surface air temperature (SAT) warming at urban stations often contains both the signal of global warming and that of local urban heat island (UHI) effects which are difficult to be separated. In this study, an urban impact indicator (Uii) developed by the authors was modified to represent the extent to which the observed temperature from a station was influenced by UHI effects. While Uii was calculated through simplifying the city's shape to a circle, the modified Uii (MUii) was calculated considering the realistic horizontal distribution of the urban lands. We selected 45 urban stations in mainland China, and then selected an adjacent station for each urban station to constitute a station pair for which the background climate changes are nearly homogeneous. Thus, difference in the trends of annual averaged daily mean SAT (Trendmean), maximum SAT (Trendmax), and minimum SAT (Trendmin) between urban and adjacent stations (ΔTrend) could be mainly attributed to the difference in MUii changes between urban and adjacent stations (ΔMUii). Several linear regressions between ΔTrend and ΔMUii of 45 station pairs were calculated to estimate the UHI effects on Trendmean (UTmean), Trendmax (UTmax), and Trendmin (UTmin) of the 45 urban stations. The results showed that the mean MUii of the 45 urban stations has increased from 0.06 to 0.35 during 1992-2013. The positive correlations between ΔMUii and ΔTrend of the selected 45 station pairs were significant at the 0.001 significance level except for Trendmax. The average UTmean and UTmin of the 45 urban stations during 1954-2013 were approximately 0.05 and 0.11°C decade−1, respectively, accounting for 18 % and 31 % of the overall warming trends, respectively. The UTmin estimated in this study is about twice that of the previous result based on the regression equations between Uii and SAT trends.

著者

FENG Tao YANG Xiu-Qun WU Liang HUANG Ronghui YANG Dejian

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-037, (Released:2020-04-09)

被引用文献数

5

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Using the Climate Forecast System Reanalysis, Joint Typhoon Warning Center best track, and Tropical Rainfall Measuring Mission precipitation data, two long-lasting synoptic-scale wave trains in 2004 and 2006 are selected to investigate the atmospheric factors controlling the structures of westward-propagating synoptic-scale disturbances over the tropical western North Pacific. The essential difference between these two wave trains is found in their vertical structures, such that the maximum perturbations occurred from the middle to lower troposphere with an equivalent barotropic structure in 2004 but primarily occurred in the upper troposphere with a prominent tilt with height in 2006. Distinct configurations of the monsoon troughs, the tropical upper-tropospheric troughs (TUTT), and associated vertical wind shear caused such structural differences. In 2004, the TUTT shifted eastward, creating an easterly sheared environment to confine synoptic-scale waves in the lower troposphere. Then, the monsoon trough enhanced the wave activity through barotropic energy conversion in the lower troposphere. In contrast, while the TUTT shifted westward in 2006, synoptic-scale waves prevailed in the upper troposphere by the environmental westerly shear. Meanwhile, the disturbances developed in the upper troposphere through to the conversion of kinetic energy from the TUTT, exhibiting a top-heavy vertical structure. The coherent movement of the monsoon trough and the TUTT modulate the vertical structure and the development of the synoptic-scale waves.

著者

YOSHINO Katsumi

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.2019-023, (Released:2018-12-13)

被引用文献数

12

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Aircrafts making landing and takeoff at Narita International Airport (Narita Airport) in Japan report frequently low-level wind shear (LLWS), a local variation of wind vector, with turbulence when the prevailing wind is southwesterly, which is crosswind to the runway direction. On 20 June 2012, an arrival aircraft at Narita Airport encountered a LLWS, which consisted of a sudden change of the wind vector from head wind component of 5 knots (2.6 m s-1) to tail wind component of 10 knots (5.1 m s-1), just before the touchdown and made a hard landing. None of cumulonimbus clouds, a front or a wind shear line was observed around the airport during her approaching and landing. Analyses of the data measured by the landing aircraft and the observations by the Doppler lidar at the airport revealed that the LLWS was caused by horizontal roll vortices, which developed in the atmospheric boundary layer (ABL) over the Shimofusa Tableland around the airport. The horizontal roll vortices had their axes nearly parallel to the mean wind direction, and their horizontal and vertical scales were approximately 800 m and 500 m, respectively. The present study demonstrated that existence of the horizontal roll vortices causing LLWS can be effectively detected by a single-Doppler lidar which utilizes backscattering from aerosols. Although the LLWS associated with the horizontal roll vortices has smaller magnitude than those caused by a microburst, a gust front and a front, a landing aircraft just before touchdown encounters the horizontal roll vortices with much higher probability than the other phenomena mentioned here since the horizontal roll vortices occurs at a horizontal spacing of approximately 800 m over a wide area during daytime of a clear day.

著者

Kozo Okamoto Hiromi Owada Tadashi Fujita Masahiro Kazumori Michiko Otsuka Hiromu Seko Yoshifumi Ota Naotaka Uekiyo Hiroshi Ishimoto Masahiro Hayashi Haruma Ishida Akiyoshi Ando Masaya Takahashi Kotaro Bessho Hironobu Yokota

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-028, (Released:2020-07-10)

被引用文献数

14

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To discuss the feasibility of the Himawari follow-on program, impacts of a hyperspectral sounder on a geostationary satellite (GeoHSS) is assessed using an observing system simulation experiment. Hypothetical GeoHSS observations are simulated by using an accurate reanalysis dataset for a heavy rainfall event in western Japan in 2018. The global data assimilation experiment demonstrates that the assimilation of clear-sky radiances of the GeoHSS improves the forecasts of the representative meteorological field and slightly reduces the typhoon position error. The regional data assimilation experiment shows that assimilating temperature and relative humidity profiles derived from the GeoHSS improves the heavy rainfall in the Chugoku region of western Japan as a result of enhanced southwesterly moisture flow off the northwestern coast of the Kyushu Island. These results suggest that the GeoHSS provides valuable information on frequently available vertically resolved temperature and humidity and thus improves the forecasts of severe events.

著者

Keita Fujiwara Ryuichi Kawamura Tetsuya Kawano

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-026, (Released:2020-07-03)

被引用文献数

5

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This study investigated the remote impact of an increase in latent heat flux (LHF) over the Kuroshio on tropical cyclone (TC) development, using a cloud-resolving model. A control run and a sensitivity experiment with Kuroshio's LHF artificially enhanced were performed for Typhoon Chaba in 2010. The TC development simulated in the sensitivity experiment was suppressed as compared with the control run. The sensitivity experiment demonstrated that eyewall convection and the associated TC secondary circulation were suppressed by a decrease in equivalent potential temperature (θe) around the eyewall through the lower θe penetration into the inner core region in the boundary layer. The dynamic features of the TC were also altered by the attenuated TC secondary circulation through the inhibition of the inward advection of the absolute angular momentum. The super-gradient tangential velocities in the inner core were smaller than those in the control run. Such thermodynamic and dynamic changes were remotely induced by the decrease in moisture import from the Kuroshio. Since the increased LHF facilitated the development of a surface low over the Kuroshio, the intensified low further accumulated the Kuroshio's vapor and suppressed low-level northeasterlies toward the TC, resulting in interrupting the moisture import into the TC.

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

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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

CUI Ye RUAN Zheng WEI Ming LI Feng GE Runsheng

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-028, (Released:2020-02-24)

被引用文献数

3

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Data from the continuous observations of 4 shallow snow events (echo top < 8 km) and 2 deep events (> 10 km) were obtained by the C-band vertically pointing radar with frequency modulation continuous wave technology (VPR-CFMCW) with extremely high resolution during the winter of 2015-2016 in middle latitudes of China. Generating cells (GCs) were found near the cloud top in each event. Reflectivity (Z), radial velocity (Vr), the vertical gradient of Z (dZ/dh, h is the vertical distance) and Vr (dVr/dh) showed different vertical distribution characteristics between the upper GC and lower stratiform (St) regions. The fall streaks (FSs) associated with GCs were embedded in the St regions. In the deep events, the proportions of GC regions were slightly larger, but the average contributions to the growth of Z (33 %) were lower than those in the shallow events (42 %). The average dZ/dh were usually 2-3 times larger inside GCs and FSs compared to outside. Bimodal Doppler spectra were used to establish the relationships between the Z and the reflectivity-weighted particle fall speed (Vz) for the 2 regions. The vertical air velocity (Wa) and Vz were then retrieved. The results show that both updraft and downdraft were alternately observed in GC regions. GC locations usually accompanied strong upward air motions, with average speeds mostly distributed around 1.2 m s−1, while downward air motions often appeared between GCs. In the St regions, the speeds of Wa were mainly within 0.5 m s−1. The upper areas of the St regions consisted primarily of weak upward motions, while weak downward motions dominated the lower areas. There was no apparent difference in Wa inside and outside the FSs. The average Vz was slightly larger inside GCs and FSs compared to outside, with the differences of 0.1-0.3 m s−1 and 0.2-0.4 m s−1 respectively.

著者

MA Yingzhao CHANDRASEKAR V. BISWAS Sounak K.

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-025, (Released:2020-02-12)

被引用文献数

8

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The accurate estimation of precipitation is an important objective for the Dual-frequency Precipitation Radar (DPR), which is located on board the Global Precipitation Measurement (GPM) satellite core observatory. In this study, a Bayesian correction (BC) approach is proposed to improve the DPR's instantaneous rainfall rate product. Ground dual-polarization radar (GR) observations are used as references, and a log-transformed Gaussian distribution is assumed as the instantaneous rainfall process. Additionally, a generalized regression model is adopted in the BC algorithm. Rainfall intensities such as light, moderate, and heavy rain and their variable influences on the model's performance are considered. The BC approach quantifies the predictive uncertainties associated with the Bayesian-corrected DPR (DPR_BC) rainfall rate estimates. To demonstrate the concepts developed in this study, data from the GPM overpasses of the Weather Service Surveillance Radar (WSR-88D), KHGX, in Houston, Texas, between April 2014 and June 2018 are used. Observation errors in the DPR instantaneous rainfall rate estimates are analyzed as a function of rainfall intensity. Moreover, the best-performing BC model is implemented in three GPM-overpass cases with heavy rainfall records across the southeastern United States. The results show that the DPR_BC rainfall rate estimates have superior skill scores and are in better agreement with the GR references than with the DPR estimates. This study demonstrates the potential of the proposed BC algorithm for enhancing the instantaneous rainfall rate product from spaceborne radar equipment.