著者

Lusha Wang Ayumi Kotani Takafumi Tanaka Takeshi Ohta

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-043, (Released:2020-11-23)

被引用文献数

1

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Based on the drought severity index (DSI), which is derived from the ratio of evapotranspiration (ET) to potential evapotranspiration (PET) and normalized difference vegetation index (NDVI), as measured by remote sensing, we replaced the ET/PET ratio with soil moisture (0-10 cm) to establish an improved index (IDSI) and evaluated the drought situation in Inner Mongolia. The two components in IDSI are independently derived; however, the effects of evapotranspiration are contained in the soil moisture, and even precipitation changes could be reflected. We used monthly IDSI data for Inner Mongolia to evaluate drought throughout the growing season (May–September) during 2001-2010. The IDSI showed that 2001, 2007, and 2009 were years with significant drought. Areas that experienced extreme drought were less extensive than those found by the DSI because we removed the ET/PET component, which already contains the effects of the NDVI. IDSI results not only contained the degree of precipitation change for a given month through soil moisture, but also reflected the influence of water and heat in the previous month through the NDVI. Moreover, IDSI results were generally consistent with agricultural drought disaster records.

著者

Kazuo Saito Takumi Matsunobu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.198-205, 2020 (Released:2020-11-04)

参考文献数

25

被引用文献数

5

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Heavy rainfalls often occur when a tropical cyclone (TC) exists on the sea off the south coast. These pre-typhoon rainfalls (PRE) is associated with the northward moisture transport ahead of the TC. In this paper, we examine the northward moisture transport by the ageostrophic winds associated with typhoon T0918 (Melor) and its impact on PRE. According to a numerical simulation conducted in the previous study (Saito 2019), we analyzed the northward moisture fluxes by reproduced geostrophic and ageostrophic winds. Although the southerly ageostrophic winds are dominant mainly in the upper levels, the ageostrophic winds contribute to enhance the poleward water vapor transport for the upper and middle levels above 3 km. To see the impact of the ageostrophic moisture transport on PRE, we conducted a sensitivity experiment where the model moisture in middle and upper levels over the sea off the south coast of western Japan was reduced. Precipitation over western Japan was decreased about 30% when the contributions in moisture fluxes by ageostrophic winds were removed. This result suggests that the northward ageostrophic winds associated with a TC enhance PRE by moistening the middle and upper atmosphere.

著者

SUZUKI Kento IWASAKI Toshiki YAMAZAKI Takeshi

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.2021-002, (Released:2020-10-21)

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Local fronts formed near the coast of the Kanto Plain mainly in a cold season, so-called “coastal fronts”, tend to be forecast on the inland side of their actual positions by the operational mesoscale Numerical Weather Prediction (NWP with a horizontal grid spacing of 5 km) model at Japan Meteorological Agency (JMA). In this study, we confirm a systematic NWP error through statistical validations of coastal fronts that occurred with southerly onshore winds during 2015-2018. Using a nonhydrostatic numerical model (JMA-NHM), we explore the relevant physical mechanisms through sensitivity experiments involving different horizontal resolution, envelope orography, and physics parameterization schemes for three cases with typical errors. The operational NWP model is shown to have a systematic error, with local fronts being consistently shifted to the inland side of their actual positions when the forecast period exceeds 5 hours, regardless of precipitation. The sensitivity experiments suggest that the systematic error associated with coastal fronts may be primarily caused by an underestimation of the mountain barrier surrounding the Kanto Plain in the model. The northwestward distance error of coastal fronts, averaged over the three illustrative cases, can be reduced by 27 % and 37 % by increasing the horizontal resolution from 5 km to 2 km and 1 km, respectively, and can be almost entirely eliminated by using the envelope orography. Moreover, the evaporative cooling of precipitation shifts coastal fronts to the seaward. Most coastal fronts are thought to take the form of cold air trapped on the southeastern slope of the mountains surrounding the Kanto Plain, where the elevation angle of the frontal surface is roughly controlled dynamically. The local front shifts to the seaward when the ridgelines of the mountains become higher, and shifts to the seaward through the reduction of the elevation angle when the trapped air becomes colder.

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

vol.16, pp.212-219, 2020 (Released:2020-11-05)

参考文献数

31

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

Kyosuke Kawano Ryoko Oda Atsushi Inagaki Makoto Nakayoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.192-197, 2020 (Released:2020-10-29)

参考文献数

23

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The thermal stress along a marathon course in Tokyo is evaluated using a radiation balance model. The wet-bulb globe temperatures (WBGTs) for runners and spectators are calculated based on the surrounding building and tree geometries using the Solar LongWave Environmental Irradiance Geometry model. Analysis is conducted in terms of summer days in August 2018, which was during the hottest summer in the past 5 years. The WBGT classification for runners along the outward leg (until around 14 km) reaches the “Warning” level (WBGT = 26.5°C) despite of the many shadows on the street in the early morning (until 0645 JST). The WBGT increases around the Imperial Palace because the road has a sky view factor of over 95%, and no obstacles to make shadows on the street at around 0750 JST. The WBGT classification for runners reaches the level of “Severe warning”. For spectators, the difference of average WBGT from the runners are about 0.1°C although the difference could be significant locally due to partial shading on a road side.

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

vol.16, pp.206-211, 2020 (Released:2020-11-04)

参考文献数

15

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 meandering, 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

Mikiko Fujita Tatsuya Fukuda Iwao Ueki Qoosaku Moteki Tomoki Ushiyama Kunio Yoneyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.16A-004, (Released:2020-10-13)

被引用文献数

4

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We report experimental observations of precipitable water vapor (PWV) derived using Global Positioning System/Global Navigation Satellite System (GPS/GNSS) receivers mounted on autonomous surface vehicles (ASVs), which were deployed in the tropical Pacific Ocean from July to September 2018. The GPS atmospheric delay was estimated by precise point positioning and converted to PWV with ASV surface meteorological data. The GPS-PWV was in agreement with the PWV obtained from radiosondes, with a root mean square error of 3.02 mm and a mean difference of 0.16 mm. A similar accuracy was found in a comparison of GPS-PWV with satellite-based microwave measurements. In anticipation of real-time monitoring applications, PWV was also estimated using real-time clock and orbit data. These estimates were in agreement with the post-processing values. High-resolution temporal observations of PWV over the open ocean made possible by ASV technology could greatly improve our understanding of the rapid variations of developing convective systems.

著者

Kyosuke Kawano Ryoko Oda Atsushi Inagaki Makoto Nakayoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-033, (Released:2020-09-10)

---

The thermal stress along a marathon course in Tokyo is evaluated using a radiation balance model. The wet-bulb globe temperatures (WBGTs) for runners and spectators are calculated based on the surrounding building and tree geometries using the Solar LongWave Environmental Irradiance Geometry model. Analysis is conducted in terms of summer days in August 2018, which was during the hottest summer in the past 5 years. The WBGT classification for runners along the outward leg (until around 14 km) reaches the “Warning” level (WBGT = 26.5°C) despite of the many shadows on the street in the early morning (until 0645 JST). The WBGT increases around the Imperial Palace because the road has a sky view factor of over 95%, and no obstacles to make shadows on the street at around 0750 JST. The WBGT classification for runners reaches the level of “Severe warning.” For spectators, the difference of average WBGT from the runners are about 0.1°C although the difference could be significant locally due to partial shading on a road side.

著者

Kazuo Saito Takumi Matsunobu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-034, (Released:2020-09-11)

被引用文献数

5

---

Heavy rainfalls often occur when a tropical cyclone (TC) exists on the sea off the south coast. These pre-typhoon rainfalls (PRE) is associated with the northward moisture transport ahead of the TC. In this paper, we examine the northward moisture transport by the ageostrophic winds associated with typhoon T0918 (Melor) and its impact on PRE. According to a numerical simulation conducted in the previous study (Saito 2019), we analyzed the northward moisture fluxes by reproduced geostrophic and ageostrophic winds. Although the southerly ageostrophic winds are dominant mainly in the upper levels, the ageostrophic winds contribute to enhance the poleward water vapor transport for the upper and middle levels above 3 km.To see the impact of the ageostrophic moisture transport on PRE, we conducted a sensitivity experiment where the model moisture in middle and upper levels over the sea off the south coast of western Japan was reduced. Precipitation over western Japan was decreased about 30% when the contributions in moisture fluxes by ageostrophic winds were removed. This result suggests that the northward ageostrophic winds associated with a TC enhance PRE by moistening the middle and upper atmosphere.

著者

Narihiro Orikasa Masataka Murakami Takuya Tajiri Yuji Zaizen Taro Shinoda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-032, (Released:2020-08-28)

被引用文献数

2

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Aircraft observations were conducted over the eastern mountainous areas of the United Arab Emirates (UAE) in September 2017 to characterize the microphysical properties of diurnal convective clouds. Aerosol particle and cloud condensation nuclei (CCN) measurements indicate that the air mass had a continental nature, resulting in high cloud droplet concentrations of 600-800 cm−3. Two case studies were undertaken to obtain the vertical profiles of hydrometeors up to the cloud top. The ice particle number concentrations in the updraft core were a few particles L−1, which is similar to the primary ice nucleating particle (INP) number concentrations estimated from immersion freezing of high concentration dust particles in the convectively mixed boundary layer. The ice particle number concentrations were several tens of particles L−1 outside the updraft core in the upper levels. INP measurements and the observed cloud microphysical structure suggest that drizzles, frozen via the immersion freezing nucleation of dust particles, formed graupel embryos and ice particles, with concentrations of one to two orders of magnitude greater than those of the primary INPs, which may be generated via secondary ice production and/or ice particle accumulation from primary ice nucleation in clouds with relatively warm cloud top temperatures (approximately −12°C).

著者

西井 和晃 田口 文明 中村 尚

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.98, no.4, pp.801-820, 2020 (Released:2020-08-26)

参考文献数

32

被引用文献数

8

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2018年7月に日本において2つの極端現象が発生した。本研究では大気大循環モデル(AGCM)のアンサンブル実験にもとづき、これらをもたらした大気大循環偏差に対する海面水温偏差の潜在的影響を評価した。一つ目の極端現象は、7月上旬での西日本を中心とする豪雨であり、日本の南西にあった低気圧性偏差と日本の東にあった高気圧性偏差による顕著な水蒸気輸送がこの主要因である。全球で観測された海面水温を与えたAGCM実験は日本の東の高気圧性偏差を再現できず、このため水蒸気輸送と豪雨を再現できなかった。もう一つの極端現象は7月中下旬に日本で全国的に観測された猛暑であり、これは日本を覆う顕著な高気圧性偏差によるものである。この高気圧性偏差はAGCM実験によって高温偏差とともによく再現された。さらなる実験により、熱帯と中緯度北太平洋のそれぞれの海面水温偏差が、猛暑をもたらした北西太平洋上の大気循環の主要モードを強制していた可能性が示された。また、6月から7月にかけて持続した北西太平洋での亜熱帯ジェットの北偏傾向、及び、北半球中緯度対流圏での高温偏差傾向も、これらの海面水温偏差がそれぞれ強制していた可能性を示した。

著者

KAWANO Tetsuya KAWAMURA Ryuichi

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.2020-033, (Released:2020-05-12)

被引用文献数

21

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A quasi-stationary convective band that persisted for approximately ten hours caused precipitation in the northern part of Kyushu Island, Japan on 5 July 2017. The extreme amount of rainfall produced by this convective band caused a number of landslides and flash floods and resulted in a severe disaster. The Weather and Research and Forecasting (WRF) model was used to perform numerical simulations and to clarify the genesis and maintenance processes of the convective band. A full-physics WRF simulation successfully reproduced the observed features of the convective band and extreme precipitation. It is shown that a quasi-stationary convergence zone in the low level played a crucial role in generating and maintaining the convective band. Trajectory and frontogenesis analyses showed that low-level confluent flows due to the blocking effects of a high pressure system located over the Sea of Japan were responsible for the formation, intensification, and sustenance of the convergence zone. Furthermore, the frontal structure of the convergence zone was intensified due to the land-sea thermal contrast between Kyushu Island and the Tsushima Strait. Two additional experiments, namely a simulation with flattened topography of Kyushu Island and a simulation without considering raindrop evaporation also reproduced the observed band well. These results indicate that topography and a cold pool due to raindrop evaporation played only minor roles in the genesis and maintenance of the convective band.

著者

TAKAMURA Nao WADA Akiyoshi

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.2020-035, (Released:2020-05-26)

被引用文献数

3

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In August 2016, a total of eight typhoons formed in the western North Pacific, and four of which landed on northern and eastern Japan. These typhoons were associated with heavy rainfall and strong winds and caused massive damages in the Japanese archipelago. Moreover, five of the eight typhoons underwent extratropical transition (ET), which was more frequent than an average of 2.1 typhoons per year during August. To clarify the characteristics of the typhoon tracks that caused such unusual landfall and frequent ET in August 2016, we conducted k-means cluster and cyclone phase space (CPS) analyses for typhoons that occurred in August and September. Composite analysis and case study were also conducted to clarify the synoptic environments around the typhoons. To examine the unusual characteristics in August 2016, we compared the results of the analyses for this period with those in August from 2001 to 2015 and those in September 2016. The k-means cluster analysis showed that the direction of the typhoon tracks in August 2016 were more northward than that of the typhoons in August from 2001 to 2015 and those in September 2016. Moreover, the CPS analysis revealed that ET in August 2016 was characterized by a more indistinct structural change from a warm-core structure to a cold-core structure with a shorter duration than ET in August from 2001 to 2015. The synoptic environments around the typhoons in August 2016 were characterized by enhanced undulations of the upper-tropospheric jet stream, increased amplitudes of the mid-tropospheric trough, and relatively warm air around the typhoons in the lower troposphere. These synoptic environments explained the unusual landfall of typhoons with a more northward track and the more frequent ET and more indistinct structural evolution of ET in August 2016.

著者

YAMAJI Moeka TAKAHASHI Hiroshi G. KUBOTA Takuji OKI Riko HAMADA Atsushi TAKAYABU Yukari N.

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.2020-038, (Released:2020-05-27)

被引用文献数

18

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This study investigates the global drop size distribution (DSD) of rainfall and its relationship to large-scale precipitation characteristics using the Dual-frequency Precipitation Radar (DPR) onboard the Global Precipitation Measurement (GPM) Core Observatory. This study focuses on seasonal variations in the dominant precipitation systems regarding variations in DSD. A mass-weighted mean diameter (Dm), which is estimated based on the dual-frequency information derived from the GPM/DPR, is statistically analyzed as a typical parameter of the DSD. Values of the annual mean Dm, in general, are larger over land than over the oceans, and the relationship between Dm and precipitation rate (R) is not a simple one-to-one relationship. Furthermore, Dm exhibits statistically significant seasonal variations, specifically over the northwest Pacific Ocean, whereas R shows insignificant variations, indicating the variations in R cannot explain the distinct seasonal changes in Dm. Focusing on the seasonal variation in Dm over the northwest Pacific Ocean, the results indicate that the variation in Dm is related to the seasonal change in the dominant precipitation systems. In the summer over the northwest Pacific Ocean, Dm is related to the organized precipitation systems associated with the Baiu front over the mid-latitudes and tropical disturbances over the subtropical region, with relatively higher precipitation top heights, composed of both stratiform and convective precipitations. Contrary to the summer, larger Dm over the mid-latitudes in winter is related to extratropical frontal systems with ice particles in the upper layers, which consists of more stratiform precipitation in the storm track region. The smaller Dm over the subtropical northwest Pacific Ocean in winter is associated with shallow convective precipitation systems with trade-wind cumulus clouds and cumulus congestus under the subtropical high.

著者

Sheau Tieh Ngai Hidetaka Sasaki Akihiko Murata Masaya Nosaka Jing Xiang Chung Liew Juneng Supari Ester Salimun Fredolin Tangang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-023, (Released:2020-06-25)

被引用文献数

9

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The Non-hydrostatic Regional Climate model (NHRCM) was used in simulating the present and future rainfall climate over Malaysia under the RCP8.5 scenario in this study. Simulation and projection from 1979 to 2002 for present day and 2070 to 2100 for the end of century were conducted over the Malaysia. The 20 km resolution MRI-AGCM3.2 model simulation from Meteorological Research Institute, MRI was used as boundary conditions. The objective of this study was to estimate the extreme rainfall projections in Malaysia at 5 km of resolution during the November to February period, representing the northeast monsoon season. Overall, the model was capable to simulate the historical rainfall climatology and distribution, but model tended to underestimate high rainfall frequency and mean rainfall intensity in Malaysia. However, compared with simulations at 25 km, added values have been shown at 5 km resolution. Based on the NHRCM05 simulations, a number of hotspots have been identified with significant projected increases up to 80% for the extreme rainfall indices (R20mm, RX1day, R95pTOT and R99pTOT), 30% increases in mean rainfall intensity (SDII) and 20% for consecutive dry days indices (CDD).

著者

Takafumi Miyasaka Hiroaki Kawase Tosiyuki Nakaegawa Yukiko Imada Izuru Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-022, (Released:2020-06-22)

被引用文献数

14

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Heavy precipitation in Japan is caused by various phenomena, such as tropical cyclones and the Baiu front, and shows regional-scale variation. Here we investigate extremely heavy precipitation events exceeding the 100-year return period in the Kanto area and future projections of such events using large ensemble climate simulations for periods of several thousand years. To understand these extreme events, associated sea level pressure anomalies over Japan and the surrounding region are classified into four clusters. These cluster means are characterized by (1) a strong anomalous cyclone, (2) a weak anomalous cyclone, (3) an anomalous cyclone accompanied by an anomalous anticyclone to the north, and (4) an anomalous anticyclone to the north. The cluster with a strong anomalous cyclone is accompanied by widely distributed heavy precipitation, and its area-averaged precipitation is predicted to be more enhanced under global warming than that of other clusters, partly because of an increase in the strength of strong tropical cyclones approaching Kanto. The cluster dominated by an anomalous anticyclone is characterized by localized heavy precipitation in the plains area. The relative frequency of this cluster will increase, whereas that of other clusters will decrease under global warming.

著者

SHIBATA Kiyotaka LEHMANN Ralph

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.2020-032, (Released:2020-04-02)

被引用文献数

2

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Ozone loss pathways and their rates in the ozone quasi-biennial oscillation (QBO) simulated by a chemistry-climate model of the Meteorological Research Institute of Japan are evaluated by using an objective pathway analysis program (PAP). The analyzed chemical system contains catalytic cycles due to NOx, HOx, ClOx, Ox, and BrOx. PAP quantified the rates of all significant catalytic ozone loss cycles, and evaluated the partitioning among these cycles. The QBO amplitude of the sum of all cycles amounts to about 4 and 14 % of the annual mean of the total ozone loss rate at 10 and 20 hPa, respectively. The contribution of catalytic cycles to the QBO of the ozone loss rate is found to be as follows: NOx cycles contribute the largest fraction (50-85 %) of the QBO amplitude of the total ozone loss rate; HOx cycles are the second-largest (20-30 %) below 30 hPa and the third-largest (about 10 %) above 20 hPa; Ox cycles rank third (5-20 %) below 30 hPa and second (about 20 %) above 20 hPa; ClOx cycles rank fourth (5-10 %); and BrOx cycles are almost negligible. The relative contribution of the NOx and Ox cycles to the QBO amplitude of ozone loss differs by up to 10 and 20 %, respectively, from their contribution to the annual-mean ozone loss rate. The ozone QBO at 20 hPa is mainly driven by ozone transport, which then affects the ozone loss rate. In contrast, the ozone QBO at 10 hPa is driven chemically mainly by NOx and the temperature dependence of [O]/[O3], which results from the temperature dependence of the reaction O + O2 + M → O3 + M. In addition, the ozone QBO at 10 hPa is influenced by the overhead ozone column, which affects [O]/[O3] (through ozone photolysis) and the ozone production rate (through oxygen photolysis).

著者

GENG Biao KATSUMATA Masaki

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.2020-031, (Released:2020-03-17)

被引用文献数

5

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In this study, an algorithm is developed to detect the spurious differential phase ΦDP and specific differential phase KDP in the rain for application following the removal of gate-to-gate ΦDP fluctuations. The algorithm is a threshold filter that is designed based on the empirical relationship between the KDP and radar reflectivity factor at horizontal polarization ZH for raindrops. The construction and validation of the algorithm was conducted using the data observed by the C-band polarimetric radar on board the research vessel Mirai near Sumatra from 23 November to 17 December 2015, when a pilot field campaign of the Years of the Maritime Continent (YMC) project was conducted. Perturbations exist in the ΦDP and associated spurious values of KDP on a 10-km scale in the range direction, which are mainly induced by second-trip echoes and nonuniform beam filling. These perturbed ΦDP values and the positively and negatively biased KDP values can be efficiently detected by this new algorithm. The standard deviation of the KDP in areas with relatively low ZH is also significantly reduced by applying the algorithm. Simultaneously, the rain rate estimation from the filtered KDP has been greatly improved. The results indicate that the algorithm developed in this study can efficiently manage the quality of the data observed not only in the open ocean but also in coastal areas of the Maritime Continent.

著者

Atsushi Inagaki Yovita Wangsaputra Manabu Kanda Meral Yücel Naoyuki Onodera Takayuki Aoki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-021, (Released:2020-06-08)

被引用文献数

2

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The similarity of the turbulence intensity profile with the inner-layer (i.e. from the ground to the top of the logarithmic layer) and the outer-layer (i.e. from the top of the inner layer to top of the boundary layer) scalings were examined for an urban boundary layer using numerical simulations. The simulations consider a developing neutral boundary layer over realistic building geometry with and without a slightly upsloping terrain. The computational domain covers an 19.2 km by 4.8 km and extends up to a height of 1 km, and is resolved by 2-m grids. Several turbulence intensity profiles are defined locally in the computational domain. The inner- and outer-layer scalings work well reducing the scatter of the turbulence intensity within the inner- and outer-layers, respectively, regardless of the surface geometry. Although the main scatters among the scaled profiles are attributed to the mismatch of the parts of the layer (i.e. inner or outer) and the scaling parameters, their behaviours can also be explained by introducing a non-dimensional parameter which consists of the ratio of the inner- and outer-layer parameters for length (the boundary-layer height over the roughness length), or velocity (the external free stream velocity over the friction velocity).

著者

Shuhei Matsugishi Hiroaki Miura Tomoe Nasuno Masaki Satoh

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.16A-003, (Released:2020-05-21)

被引用文献数

6

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We show that a modification to the latent heat flux (LHF) formulation in Non-hydrostatic Icosahedral Atmospheric Model (NICAM) impacts the representation of a Madden–Julian oscillation (MJO) event during the Pre-Years of the Maritime Continent (Pre-YMC) field campaign in 2015. First, we compare the LHFs computed by the standard NICAM setting with those estimated from the ship observation during Pre-YMC. In this comparison, the NICAM LHF is smaller than observation in the low wind speed region and larger in the high wind speed region. Consequently, the MJO signal weakens when it passes over the Maritime Continent (MC). Next, sensitivity experiments are conducted with a modification to the threshold minimum wind speed in the bulk formula, to enhance the LHFs in the low wind speed region. With this modification, propagation of the MJO is better simulated over the MC, although a bias still remains without corrections in the high wind speed regions. This result indicates that increasing the LHF in the low wind speed region likely contributes to a more effective accumulation of moisture over the eastern MC region and consequently allows the MJO to pass over the MC in the model.