DSpace Collection:
http://hdl.handle.net/2115/20051
2024-03-29T07:19:40ZA rapid synthesis of Hf-Beta zeolite as highly active catalyst for Meerwein-Ponndorf-Verley reduction by controlling water content of precursor gel
http://hdl.handle.net/2115/91231
Title: A rapid synthesis of Hf-Beta zeolite as highly active catalyst for Meerwein-Ponndorf-Verley reduction by controlling water content of precursor gel
Authors: Nakamura, Taichi; Kamiya, Yuichi; Otomo, Ryoichi
Abstract: Hf-Beta is a promisingly active Lewis acid catalyst for Meerwein-Ponndorf-Verley (MPV) reduction and other important organic reactions. However, the conventional hydrothermal synthesis of Hf-Beta inevitably requires the troublesome procedure for hydrolysis of tetraethoxysilane and the long period to complete crystallization. In the present study, we applied a synthetic approach of reducing water content of precursor gel and succeeded in considerably shortening the period for crystallization of Hf-Beta using fumed silica as silicon source. By using precursor gel with H2O/SiO2 = 1.4-7.6, effect of water content of precursor gel on the crystallization of Hf-Beta, the incorporation of Hf into the zeolite framework, and the catalytic performance were thoroughly investigated. Low water content was favorable for accelerating the crystallization, but unfavorable for the incorporation of Hf into the zeolite framework, resulting in poor catalytic activity. With the assistance of seed crystal, Hf-Beta with a relatively large amount of framework Hf was obtained from the precursor gel with H2O/SiO2 = 6.4 in 24 h. HfBeta synthesized in this way showed higher catalytic activity for MPV reduction than Hf-Beta as well as Zr-, and Sn-Beta synthesized by the conventional hydrothermal method.2022-02-28T15:00:00ZNakamura, TaichiKamiya, YuichiOtomo, RyoichiHf-Beta is a promisingly active Lewis acid catalyst for Meerwein-Ponndorf-Verley (MPV) reduction and other important organic reactions. However, the conventional hydrothermal synthesis of Hf-Beta inevitably requires the troublesome procedure for hydrolysis of tetraethoxysilane and the long period to complete crystallization. In the present study, we applied a synthetic approach of reducing water content of precursor gel and succeeded in considerably shortening the period for crystallization of Hf-Beta using fumed silica as silicon source. By using precursor gel with H2O/SiO2 = 1.4-7.6, effect of water content of precursor gel on the crystallization of Hf-Beta, the incorporation of Hf into the zeolite framework, and the catalytic performance were thoroughly investigated. Low water content was favorable for accelerating the crystallization, but unfavorable for the incorporation of Hf into the zeolite framework, resulting in poor catalytic activity. With the assistance of seed crystal, Hf-Beta with a relatively large amount of framework Hf was obtained from the precursor gel with H2O/SiO2 = 6.4 in 24 h. HfBeta synthesized in this way showed higher catalytic activity for MPV reduction than Hf-Beta as well as Zr-, and Sn-Beta synthesized by the conventional hydrothermal method.Revisiting the strong and weak ENSO teleconnection impacts using a high-resolution atmospheric model
http://hdl.handle.net/2115/91107
Title: Revisiting the strong and weak ENSO teleconnection impacts using a high-resolution atmospheric model
Authors: Dogar, Muhammad Mubashar Ahmad; Almazroui, Mansour
Abstract: To evaluate the performance of a high-resolution atmospheric model (HiRAM) and to improve our understanding of the climatic impacts of ENSO forcing and associated teleconnections, we analyzed AMIP-style HiRAM simulations conducted effectively at 25 km grid spacing. To better assess HiRAM response to ENSO climate variability; we categorized it into strong and weak El Niño/La Niña episodes. The HiRAM model reproduced the impacts of strong ENSO over global scale very well, however, it underestimated ENSO teleconnection patterns and associated changes over regional scale (e.g., MENA and South Asia), especially following weak ENSO that could be attributed to model weak response to circulation changes such as Pacific North American (PNA) and North Atlantic Oscillation (NAO). Moreover, our results emphasize that ENSO impacts are relatively stronger over the Inter-Tropical Convergence Zone (ITCZ) compared to extra-tropics and high-latitude regions. The positive phase of ENSO causes weakening in rainfall over the African tropical rain-belt, parts of South and Southeast Asia. Both the reanalysis and HiRAM results reveal that ENSO-induced negative (positive) NAO-like response and associated changes over Southern Europe and North Africa vary significantly following the increased intensity of El Niño (La Niña). We further found that the ENSO magnitude significantly impacts Hadley and Walker circulations. The El Niño phase of ENSO overall strengthens the Hadley Cell, and the reverse is true for the La Niña phase. This ENSO-induced strengthening and weakening of Hadley Cell induce significant impact over South Asian and African convective regions through modification of the ITCZ circulation system.2022-01-31T15:00:00ZDogar, Muhammad Mubashar AhmadAlmazroui, MansourTo evaluate the performance of a high-resolution atmospheric model (HiRAM) and to improve our understanding of the climatic impacts of ENSO forcing and associated teleconnections, we analyzed AMIP-style HiRAM simulations conducted effectively at 25 km grid spacing. To better assess HiRAM response to ENSO climate variability; we categorized it into strong and weak El Niño/La Niña episodes. The HiRAM model reproduced the impacts of strong ENSO over global scale very well, however, it underestimated ENSO teleconnection patterns and associated changes over regional scale (e.g., MENA and South Asia), especially following weak ENSO that could be attributed to model weak response to circulation changes such as Pacific North American (PNA) and North Atlantic Oscillation (NAO). Moreover, our results emphasize that ENSO impacts are relatively stronger over the Inter-Tropical Convergence Zone (ITCZ) compared to extra-tropics and high-latitude regions. The positive phase of ENSO causes weakening in rainfall over the African tropical rain-belt, parts of South and Southeast Asia. Both the reanalysis and HiRAM results reveal that ENSO-induced negative (positive) NAO-like response and associated changes over Southern Europe and North Africa vary significantly following the increased intensity of El Niño (La Niña). We further found that the ENSO magnitude significantly impacts Hadley and Walker circulations. The El Niño phase of ENSO overall strengthens the Hadley Cell, and the reverse is true for the La Niña phase. This ENSO-induced strengthening and weakening of Hadley Cell induce significant impact over South Asian and African convective regions through modification of the ITCZ circulation system.Cloud observations
http://hdl.handle.net/2115/90914
Title: Cloud observations
Authors: Fujiwara, Masatomo; Reale, Anthony; Sun, Bomin; Calbet, Xavier; Maturilli, Marion; Demoz, Belay; Sakai, Ricardo; Lam, David; Edwards, David; Madonna, Fabio; Cimini, Domenico; Dupont, Jean-Charles; Iwabuchi, Masami; Kivi, Rigel; Carminati, Fabien; Gardiner, Tom; Sommer, Michael; Simeonov, Tzvetan; Wang, Junhong; Thorne, Peter2022-06-26T15:00:00ZFujiwara, MasatomoReale, AnthonySun, BominCalbet, XavierMaturilli, MarionDemoz, BelaySakai, RicardoLam, DavidEdwards, DavidMadonna, FabioCimini, DomenicoDupont, Jean-CharlesIwabuchi, MasamiKivi, RigelCarminati, FabienGardiner, TomSommer, MichaelSimeonov, TzvetanWang, JunhongThorne, PeterLODEWAVE (Long-Duration Balloon Experiment of Gravity WAVE over Antarctica)
http://hdl.handle.net/2115/90913
Title: LODEWAVE (Long-Duration Balloon Experiment of Gravity WAVE over Antarctica)
Authors: TOMIKAWA, Yoshihiro; SATO, Kaoru; SAITO, Yoshitaka; MURATA, Isao; HIRASAWA, Naohiko; KOHMA, Masashi; NAKASHINO, Kyoichi; AKITA, Daisuke; MATSUO, Takuma; FUJIWARA, Masatomo; KAHO, Takana; YOSHIDA, Lihito2023-03-22T15:00:00ZTOMIKAWA, YoshihiroSATO, KaoruSAITO, YoshitakaMURATA, IsaoHIRASAWA, NaohikoKOHMA, MasashiNAKASHINO, KyoichiAKITA, DaisukeMATSUO, TakumaFUJIWARA, MasatomoKAHO, TakanaYOSHIDA, LihitoCause of a Lower‐Tropospheric High‐Ozone Layer in Spring Over Hanoi
http://hdl.handle.net/2115/90912
Title: Cause of a Lower‐Tropospheric High‐Ozone Layer in Spring Over Hanoi
Authors: Ogino, S.‐Y.; Miyazaki, K.; Fujiwara, M.; Nodzu, M. I.; Shiotani, M.; Hasebe, F.; Matsumoto, J.; Witte, J.; Thompson, A. M.; Nguyen‐Thi, H. A.; Nguyen, T. V.
Abstract: The ozonesonde observations in Hanoi, Vietnam, over 14 years since 2004, have confirmed an enhancement in lower tropospheric ozone concentration at about 3 km altitude in the spring season. We investigated the evolution of the ozone enhancement from analysis of meteorological data, backward trajectories, and model sensitivity experiments. In spring, air masses over Hanoi exhibit strong height dependence. At 3 km, the high-ozone air masses originate from the land area to the west of Hanoi, while low-ozone air masses below about 1.5 km are from the oceanic area to the east. Above 4 km, the air masses are mostly traced back to the farther west area. The chemical transport model simulations revealed that precursor emissions from biomass burning in the inland Indochina Peninsula have the largest contribution to the lower tropospheric ozone enhancement, which is transported upward and eastward and overhangs the clean air intrusion from the ocean to the east of Hanoi. At this height level, the polluted air has the horizontal extent of about 20° in longitude and latitude. The polluted air observed in Hanoi is transported further east and widely spread over the northern Pacific Ocean.2022-04-28T15:00:00ZOgino, S.‐Y.Miyazaki, K.Fujiwara, M.Nodzu, M. I.Shiotani, M.Hasebe, F.Matsumoto, J.Witte, J.Thompson, A. M.Nguyen‐Thi, H. A.Nguyen, T. V.The ozonesonde observations in Hanoi, Vietnam, over 14 years since 2004, have confirmed an enhancement in lower tropospheric ozone concentration at about 3 km altitude in the spring season. We investigated the evolution of the ozone enhancement from analysis of meteorological data, backward trajectories, and model sensitivity experiments. In spring, air masses over Hanoi exhibit strong height dependence. At 3 km, the high-ozone air masses originate from the land area to the west of Hanoi, while low-ozone air masses below about 1.5 km are from the oceanic area to the east. Above 4 km, the air masses are mostly traced back to the farther west area. The chemical transport model simulations revealed that precursor emissions from biomass burning in the inland Indochina Peninsula have the largest contribution to the lower tropospheric ozone enhancement, which is transported upward and eastward and overhangs the clean air intrusion from the ocean to the east of Hanoi. At this height level, the polluted air has the horizontal extent of about 20° in longitude and latitude. The polluted air observed in Hanoi is transported further east and widely spread over the northern Pacific Ocean.Balloon-borne aerosol–cloud interaction studies (BACIS): field campaigns to understand and quantify aerosol effects on clouds
http://hdl.handle.net/2115/90910
Title: Balloon-borne aerosol–cloud interaction studies (BACIS): field campaigns to understand and quantify aerosol effects on clouds
Authors: Ravi Kiran, Varaha; Venkat Ratnam, Madineni; Fujiwara, Masatomo; Russchenberg, Herman; Wienhold, Frank G.; Madhavan, Bomidi Lakshmi; Roja Raman, Mekalathur; Nandan, Renju; Akhil Raj, Sivan Thankamani; Hemanth Kumar, Alladi; Ravindra Babu, Saginela
Abstract: A better understanding of aerosol–cloud interaction processes is important to quantify the role of clouds and aerosols on the climate system. There have been significant efforts to explain the ways aerosols modulate cloud properties. However, from the observational point of view, it is indeed challenging to observe and/or verify some of these processes because no single instrument or platform has been proven to be sufficient. Discrimination between aerosol and cloud is vital for the quantification of aerosol–cloud interaction. With this motivation, a set of observational field campaigns named balloon-borne aerosol–cloud interaction studies (BACIS) is proposed and conducted using balloon-borne in situ measurements in addition to the ground-based (lidar; mesosphere, stratosphere and troposphere (MST) radar; lower atmospheric wind profiler; microwave radiometer; ceilometer) and space-borne (CALIPSO) remote sensing instruments from Gadanki (13.45∘ N, 79.2∘ E), India. So far, 15 campaigns have been conducted as a part of BACIS campaigns from 2017 to 2020. This paper presents the concept of the observational approach, lists the major objectives of the campaigns, describes the instruments deployed, and discusses results from selected campaigns. Balloon-borne measurements of aerosol and cloud backscatter ratio and cloud particle count are qualitatively assessed using the range-corrected data from simultaneous observations of ground-based and space-borne lidars. Aerosol and cloud vertical profiles obtained in multi-instrumental observations are found to reasonably agree. Apart from this, balloon-borne profiling is found to provide information on clouds missed by ground-based and/or space-borne lidar. A combination of the Compact Optical Backscatter AerosoL Detector (COBALD) and Cloud Particle Sensor (CPS) sonde is employed for the first time in this study to discriminate cloud and aerosol in an in situ profile. A threshold value of the COBALD colour index (CI) for ice clouds is found to be between 18 and 20, and CI values for coarse-mode aerosol particles range between 11 and 15. Using the data from balloon measurements, the relationship between cloud and aerosol is quantified for the liquid clouds. A statistically significant slope (aerosol–cloud interaction index) of 0.77 found between aerosol backscatter and cloud particle count reveals the role of aerosol in the cloud activation process. In a nutshell, the results presented here demonstrate the observational approach to quantifying aerosol–cloud interactions.2022-08-18T15:00:00ZRavi Kiran, VarahaVenkat Ratnam, MadineniFujiwara, MasatomoRusschenberg, HermanWienhold, Frank G.Madhavan, Bomidi LakshmiRoja Raman, MekalathurNandan, RenjuAkhil Raj, Sivan ThankamaniHemanth Kumar, AlladiRavindra Babu, SaginelaA better understanding of aerosol–cloud interaction processes is important to quantify the role of clouds and aerosols on the climate system. There have been significant efforts to explain the ways aerosols modulate cloud properties. However, from the observational point of view, it is indeed challenging to observe and/or verify some of these processes because no single instrument or platform has been proven to be sufficient. Discrimination between aerosol and cloud is vital for the quantification of aerosol–cloud interaction. With this motivation, a set of observational field campaigns named balloon-borne aerosol–cloud interaction studies (BACIS) is proposed and conducted using balloon-borne in situ measurements in addition to the ground-based (lidar; mesosphere, stratosphere and troposphere (MST) radar; lower atmospheric wind profiler; microwave radiometer; ceilometer) and space-borne (CALIPSO) remote sensing instruments from Gadanki (13.45∘ N, 79.2∘ E), India. So far, 15 campaigns have been conducted as a part of BACIS campaigns from 2017 to 2020. This paper presents the concept of the observational approach, lists the major objectives of the campaigns, describes the instruments deployed, and discusses results from selected campaigns. Balloon-borne measurements of aerosol and cloud backscatter ratio and cloud particle count are qualitatively assessed using the range-corrected data from simultaneous observations of ground-based and space-borne lidars. Aerosol and cloud vertical profiles obtained in multi-instrumental observations are found to reasonably agree. Apart from this, balloon-borne profiling is found to provide information on clouds missed by ground-based and/or space-borne lidar. A combination of the Compact Optical Backscatter AerosoL Detector (COBALD) and Cloud Particle Sensor (CPS) sonde is employed for the first time in this study to discriminate cloud and aerosol in an in situ profile. A threshold value of the COBALD colour index (CI) for ice clouds is found to be between 18 and 20, and CI values for coarse-mode aerosol particles range between 11 and 15. Using the data from balloon measurements, the relationship between cloud and aerosol is quantified for the liquid clouds. A statistically significant slope (aerosol–cloud interaction index) of 0.77 found between aerosol backscatter and cloud particle count reveals the role of aerosol in the cloud activation process. In a nutshell, the results presented here demonstrate the observational approach to quantifying aerosol–cloud interactions.Comparison of GRUAN data products for Meisei iMS-100 and Vaisala RS92 radiosondes at Tateno, Japan
http://hdl.handle.net/2115/90907
Title: Comparison of GRUAN data products for Meisei iMS-100 and Vaisala RS92 radiosondes at Tateno, Japan
Authors: Hoshino, Shunsuke; Sugidachi, Takuji; Shimizu, Kensaku; Kobayashi, Eriko; Fujiwara, Masatomo; Iwabuchi, Masami
Abstract: A total of 99 dual soundings with Meisei iMS-100 radiosonde and Vaisala RS92 radiosondes were carried out at the Aerological Observatory of the Japan Meteorological Agency, known as Tateno (36.06∘ N, 140.13∘ E, 25.2 m; the World Meteorological Organization, WMO, station number 47646), from September 2017 to January 2020. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) data products (GDPs) from both sets of radiosonde data for 59 flights were subsequently created using a documented processing programme along with the provision of optimal estimates for measurement uncertainty. Differences in radiosonde performance were then quantified using these GDPs. For daytime observations, the iMS-100 temperature is around 0.5 K cooler than RS92-GDP in the stratosphere, with significant differences in the upper troposphere and lower stratosphere in consideration of combined uncertainties. For nighttime observations, the difference is around −0.1 K, and data are mostly in agreement. For relative humidity (RH), iMS-100 is around 1 % RH–2 % RH higher in the troposphere and 1 % RH smaller in the stratosphere than RS92, but both GDPs are in agreement for most of the profile. The mean pressure difference is ≤0.1 hPa, the wind speed difference is from −0.04 to +0.14 m s−1, the wind direction difference is , and the root mean square vector difference (RMSVD) for wind is ≤1.04 m s−1.2022-10-18T15:00:00ZHoshino, ShunsukeSugidachi, TakujiShimizu, KensakuKobayashi, ErikoFujiwara, MasatomoIwabuchi, MasamiA total of 99 dual soundings with Meisei iMS-100 radiosonde and Vaisala RS92 radiosondes were carried out at the Aerological Observatory of the Japan Meteorological Agency, known as Tateno (36.06∘ N, 140.13∘ E, 25.2 m; the World Meteorological Organization, WMO, station number 47646), from September 2017 to January 2020. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) data products (GDPs) from both sets of radiosonde data for 59 flights were subsequently created using a documented processing programme along with the provision of optimal estimates for measurement uncertainty. Differences in radiosonde performance were then quantified using these GDPs. For daytime observations, the iMS-100 temperature is around 0.5 K cooler than RS92-GDP in the stratosphere, with significant differences in the upper troposphere and lower stratosphere in consideration of combined uncertainties. For nighttime observations, the difference is around −0.1 K, and data are mostly in agreement. For relative humidity (RH), iMS-100 is around 1 % RH–2 % RH higher in the troposphere and 1 % RH smaller in the stratosphere than RS92, but both GDPs are in agreement for most of the profile. The mean pressure difference is ≤0.1 hPa, the wind speed difference is from −0.04 to +0.14 m s−1, the wind direction difference is , and the root mean square vector difference (RMSVD) for wind is ≤1.04 m s−1.Development of a New Particle Imaging Radiosonde with Particle Fall Velocity Measurements in Clouds
http://hdl.handle.net/2115/90906
Title: Development of a New Particle Imaging Radiosonde with Particle Fall Velocity Measurements in Clouds
Authors: Suzuki, Kenji; Hara, Yurika; Sugidachi, Takuji; Shimizu, Kensaku; Fujiwara, Masatomo
Abstract: A new particle imaging radiosonde “Rainscope” has been developed, and for the first time, particle fall velocity measurement functionality was added to a balloon-borne device. Rainscope can capture a clear still image of precipitation particles in a cloud when they interrupt an infrared beam, using a CMOS camera equipped with an electronic shutter. It can also record the time when a particle passes the upper and lower built-in infrared sensors, enabling measurement of the velocity of falling precipitation particles. For ground testing in rain and snow, a ground-based Rainscope showed raindrop/snowflake size-fall velocity distributions similar to those obtained in previous studies. In a comparison with a Parsivel2 disdrometer in rain, the Rainscope results were in good agreement with the distributions obtained by an adjacent Parsivel2. In a test flight of Rainscope into a stratiform cloud, raindrops, mostly melted particles, snowflakes in the process of melting, graupel, and snowflakes were observed. It was observed that the fall velocity varied depending on the type of solid precipitation particles.2023-10-30T15:00:00ZSuzuki, KenjiHara, YurikaSugidachi, TakujiShimizu, KensakuFujiwara, MasatomoA new particle imaging radiosonde “Rainscope” has been developed, and for the first time, particle fall velocity measurement functionality was added to a balloon-borne device. Rainscope can capture a clear still image of precipitation particles in a cloud when they interrupt an infrared beam, using a CMOS camera equipped with an electronic shutter. It can also record the time when a particle passes the upper and lower built-in infrared sensors, enabling measurement of the velocity of falling precipitation particles. For ground testing in rain and snow, a ground-based Rainscope showed raindrop/snowflake size-fall velocity distributions similar to those obtained in previous studies. In a comparison with a Parsivel2 disdrometer in rain, the Rainscope results were in good agreement with the distributions obtained by an adjacent Parsivel2. In a test flight of Rainscope into a stratiform cloud, raindrops, mostly melted particles, snowflakes in the process of melting, graupel, and snowflakes were observed. It was observed that the fall velocity varied depending on the type of solid precipitation particles.Planning and Proposal for Phase 2 of the SPARC-Reanalysis Inter-comparison Project (S-RIP)
http://hdl.handle.net/2115/90894
Title: Planning and Proposal for Phase 2 of the SPARC-Reanalysis Inter-comparison Project (S-RIP)
Authors: Wright, Jonathon; Manney, Gloria; Fujiwara, Masatomo2022-12-31T15:00:00ZWright, JonathonManney, GloriaFujiwara, MasatomoCurrent Challenges and Future Directions in Data Assimilation and Reanalysis
http://hdl.handle.net/2115/90893
Title: Current Challenges and Future Directions in Data Assimilation and Reanalysis
Authors: Valmassoi, Arianna; Keller, Jan D.; Kleist, Daryl T.; English, Stephen; Ahrens, Bodo; Ďurán, Ivan Bašták; Bauernschubert, Elisabeth; Bosilovich, Michael G.; Fujiwara, Masatomo; Hersbach, Hans; Lei, Lili; Löhnert, Ulrich; Mamnun, Nabir; Martin, Cory R.; Moore, Andrew; Niermann, Deborah; Ruiz, Juan José; Scheck, Leonhard2023-03-31T15:00:00ZValmassoi, AriannaKeller, Jan D.Kleist, Daryl T.English, StephenAhrens, BodoĎurán, Ivan BaštákBauernschubert, ElisabethBosilovich, Michael G.Fujiwara, MasatomoHersbach, HansLei, LiliLöhnert, UlrichMamnun, NabirMartin, Cory R.Moore, AndrewNiermann, DeborahRuiz, Juan JoséScheck, Leonhard