Masatomo Fujiwara

• Hokkaido University

Following strong tropical volcanism, the Middle East and North Africa (MENA) region witnessed significant winter cooling, conventionally attributed to volcanically forced positive phase of North Atlantic Oscillation (NAO) and direct volcanic effects. However, coexisting positive phase of El Niño–Southern Oscillation (ENSO) prompts that this enhance...

Studying tropospheric ozone over the remote areas of the planet, such as the open oceans and the polar regions, is crucial to understand the role of ozone as a global climate forcer and regulator of atmospheric oxidative capacity. A focus on the pristine oceanic and polar regions complements the available land-based data sets and provides insights...

We assess and illustrate the benefits of high-altitude attainment of balloon-borne radiosonde soundings, up to and beyond 10 hPa level compared to e.g. 30 hPa, at operational stations and at sites of the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN). We first discuss technical challenges and the possible solutions for b...

We have developed a Peltier-based non-cryogenic chilled-mirror hygrometer named SKYDEW to measure water vapor from the surface to the stratosphere. Several chamber experiments were conducted to investigate the characteristics and performance of the instrument under various conditions. The stability of the feedback controller that maintains the cond...

We investigate the influence of the background wind regime on interannual variability in equatorial Kelvin waves (including both freely propagating ones and convectively coupled ones) in the upper troposphere and lower stratosphere using the ERA5 reanalysis data. We focus on variability in the number of Kelvin wave cases as a function of the backgr...

The anomalous variability of extreme cases of the tropical tropopause provides insight into the stratosphere‐troposphere exchange process crucial for understanding climate change. The present study analyses the extreme variability of the tropopause and its thermal structure over the tropics using GPS radio occultation data over the period 2006–2019...

The Asian Summer Monsoon Anticyclone (ASMA) is a gateway for atmospheric pollutants transported to the upper troposphere and lower stratosphere (UTLS). Thus, it is necessary to understand the relative roles of vertical transport due to convection and horizontal transport due to advection in the formation and sustenance of the ASMA. Outgoing longwav...

The Asian summer monsoon anticyclone (ASMA) plays a vital role in the transport and redistribution of the tracers in the upper troposphere and lower stratosphere during transient monsoon conditions. The ASMA can be identified using various diagnostics such as winds and divergence, potential vorticity, the Montgomery stream function or geopotential...

A 30-year (1980–2010) climatology of the major variables and terms of the transformed Eulerian-mean (TEM) momentum and thermodynamic equations is constructed by using four global atmospheric reanalyses: the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2); the Japanese 55-year Reanalysis (JRA-55); the European Ce...

We have developed a Peltier-based non-cryogenic chilled-mirror hygrometer named “SKYDEW” to measure water vapor from the surface to the stratosphere. Several chamber experiments were conducted to investigate the characteristics and performance of the instrument under various conditions. The stability of the feedback controller that maintains the co...

High‐latitude winter warming was observed following strong tropical volcanism, which has long been believed to be due to the volcanic‐induced positive North Atlantic Oscillation (NAO) phase. However, recent works argue that this warming is caused by El Niño–Southern Oscillation (ENSO) variability instead of volcanoes. Moreover, some studies further...

A 30-year (1980–2010) climatology of the major variables and terms of the transformed Eulerian-mean (TEM) momentum and thermodynamic equations is constructed by using four global atmospheric reanalyses, MERRA-2, JRA-55, ERA-Interim, and CFSR. Both the reanalysis ensemble mean (REM) and the differences of each reanalysis from the REM are investigate...

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....

High-latitude winter warming was observed following strong tropical volcanism, which has long been believed to be due to the volcanic-induced positive NAO phase. However, recent works argue that this warming is caused by ENSO variability. Moreover, controversies exist about the sensitivity of ENSO to volcanism. Therefore, to better resolve the cont...

Greetings from SRM Institute of Science and technology (SRMIST) Chennai, India. To promote a better understanding towards the increasing emission and their transport to the upper troposphere stratosphere, the 2nd International Conference on the Asian Summer Monsoon Anticyclone: Gateway of surface pollutants to the stratosphere will be held during...

Atmospheric gravity waves transport momentum in the atmosphere and play an important role in determining temperature and wind distributions through driving the meridional circulation in the middle atmosphere. However, they have wide spatial and temporal scales, which make it difficult to capture the whole feature of gravity waves with any of the la...

Water vapor measurements by frost point hygrometers (FPHs) carried aboard aircraft during the mid-1940s revealed the ubiquitous dryness of the stratosphere. It was not until the 1960s that a lightweight and compact FPH was developed for use on meteorological balloons, allowing water vapor vertical profiles to be measured in situ from the very wet s...

Understanding the influence of volcanism on ENSO and associated climatic impacts is of great scientific and social importance. Although many studies on the volcano–ENSO nexus are available, a thorough review of ENSO sensitivity to explosive eruptions is still missing. Therefore, this study aims to provide an in-depth assessment of the ENSO response...

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 Sy...

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 proce...

Plain Language Summary Ozone in the lower atmosphere acts as an air pollutant and is one of the strong greenhouse gases. Understanding chemical and transport processes that control ozone variations provide important implications for the origin of air pollution and for climate change. In the past 20 years, the global tropospheric ozone amount has in...

A total of 99 dual soundings with Meisei iMS-100 radiosonde and Vaisala RS92 radiosondes were carried out at Aerological Observatory of the Japan Meteorological Agency, known as Tateno (36.06° N, 140.13° E, 25.2 m; WMO station number 47646), from September 2017 to January 2020. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRU...

The S-RIP activity focuses predominantly on reanalyses, although some chapters include diagnostics from operational analyses when appropriate. Many of the chapters focus primarily on newer reanalysis systems that assimilate upper-air measurements and produce data at relatively high resolution (i.e., ERA-Interim, JRA55, MERRA, MERRA-2, and CFSR). Th...

Better understanding of aerosol-cloud interaction processes is an important aspect to quantify the role of clouds and aerosols in 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 the...

Eastward air-mass transport from the Asian summer monsoon (ASM) anticyclone in the upper troposphere and lower stratosphere (UTLS) often involves eastward-shedding vortices, which can cover most of the Japanese archipelago. We investigated the aerosol characteristics of these vortices by analysing data from two lidar systems in Japan, at Tsukuba (3...

Solar shortwave and terrestrial thermal longwave irradiance are measured at radiation sites at the Earth's surface and on satellite platforms high up in space, since many years. Radiation profiles through the Earth's atmosphere, however, have only sporadically been measured from enhanced upper-air radiosondes. Here we show profiles of solar and ter...

Eastward airmass transport from the Asian summer monsoon (ASM) anticyclone in the upper troposphere and lower stratosphere (UTLS) often involves eastward shedding vortices, which can cover most of the Japanese archipelago. We investigated the aerosol characteristics of these vortices by analysing data from two lidar systems in Japan, at Tsukuba (36...

The first International ASMA Conference was held on 10-11 February 2020 at SRMIST, Chennai, India, with 45 participants from 5 countries, mostly from India. Scientific presentations and discussions covered a focused and thematic topic on the transport of the surface pollutants to UTLS via ASMA region, its transport pathways, deep convection, the tr...

This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere within six major global atmospheric reanalysis datasets and with recent satellite Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) and Microwave Limb Sounder (MLS) observations....

In situ and remote sensing observations of water vapor are analyzed to assess the evidence for direct convective hydration of the lower stratosphere. We have examined several hundred balloon‐borne and airborne in situ measurements of lower stratospheric humidity in the tropics and northern midlatitudes. We find that the tropical lower stratospheric...

In the last two decades, technological progress has not only seen improvements to the quality of atmospheric upper-air observations but also provided the opportunity to design and implement automated systems able to replace measurement procedures typically performed manually. Radiosoundings, which remain one of the primary data sources for weather...

Abstract. This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere among six major global atmospheric reanalysis datasets and with recent satellite SABER and MLS observations. All reanalyses have a good representation of the quasi-biennial oscillation (QBO)...

Abstract. In the last two decades, technological progress has not only seen improvements to the quality of atmospheric upper-air observations, but also provided the opportunity to design and implement automated systems able to replace measurement procedures typically performed manually. Radiosoundings, which remain one of the primary data sources f...

The global response of air temperature at 2 m above the surface to the eruptions of Mount Agung in March 1963, El Chichón in April 1982, and Mount Pinatubo in June 1991 is investigated using 11 global atmospheric reanalysis data sets (JRA-55, JRA-25, MERRA-2, MERRA, ERA-Interim, ERA-40, CFSR, NCEP-NCAR R-1, 20CR version 2c, ERA-20C, and CERA-20C)....

Equatorial Kelvin and mixed Rossby–gravity (MRG) waves in the tropical tropopause layer and stratosphere represented in recent reanalyses for the period of 1981–2010 are compared in terms of spectral characteristics, spatial structures, long-term variations, and their forcing of the quasi-biennial oscillation (QBO). For both wave types, the spectra...

The global response of air temperature at 2 metre above the surface to the eruptions of Mount Agung in March 1963, El Chichón in April 1982, and Mount Pinatubo in June 1991 is investigated using 11 global atmospheric reanalysis data sets (JRA-55, JRA-25, MERRA-2, MERRA, ERA-Interim, ERA-40, CFSR, NCEP-NCAR R-1, 20CR version 2c, ERA-20C, and CERA-20...

A total of 87 dual flights of Meisei RS-11G radiosondes and Vaisala RS92-SGP radiosondes were carried out at the Aerological Observatory of the Japan Meteorological Agency (36.06∘ N, 140.13∘ E, 25.2 m) from April 2015 to June 2017. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) data products from both sets of radiosonde...

Using COSMIC GPS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with the height resolution of about 0.1 km in the upper troposphere and lower stratosphere (UTLS). We investigated the distribution of static stability (N2) and the zonal structure of the tropopause inversion layer (TIL) in the...

Using COSMIC GPS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with the height resolution of about 0.1 km in the upper troposphere and lower stratosphere (UTLS). We investigated the distribution of static stability (N 2) and the zonal structure of the tropopause inversion layer (TIL) in th...

Large-and-Sparse-particle Clouds (LSC), characterized by large particle size (radius > 50 μm) and small number concentration (<10 ⁴ m ⁻³ ), were observed with the space-borne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and with the space-borne 94-GHz cloud profiling radar (CPR). CALIOP was found to be less sensitive to the LSC...

Equatorial Kelvin and mixed Rossby-gravity (MRG) waves in the tropical tropopause layer and stratosphere represented in recent reanalyses for the period of 1981–2010 are compared in terms of spectral characteristics, spatial structures, long-term variations and their forcing of the quasi-biennial oscillation. For both wave types, the spectral distr...

A total of 87 dual flights of Meisei RS-11G radiosondes and Vaisala RS92-SGP radiosondes were carried out at the Aerological Observatory of the Japan Meteorological Agency (36.06°N, 140.13°E, 25.2m) from April 2015 to June 2017. Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) data products from both sets of radiosonde dat...

Using COSMIC GNSS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with 0.1 km vertical resolution in the upper troposphere and lower stratosphere (UTLS). We investigated the global distribution of static stability (N2) and the characteristics of the tropopause inversion layer (TIL) in the tr...

Since the mid-twentieth century, radiosonde and satellite measurements show that the troposphere has warmed and the stratosphere has cooled. These changes are primarily due to increasing concentrations of well-mixed greenhouse gases and the depletion of stratospheric ozone. In response to continued greenhouse gas increases and stratospheric ozone d...

This data set, which is prepared for the Stratosphere–troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP), provides several zonal-mean diagnostics computed from reanalysis data on pressure levels. Diagnostics are currently provided for a variety of reanalyses, including ERA-40, ERA-Interim, ERA-20C, NC...

This data set, which is prepared for the SPARC-Reanalysis Intercomparison Project (S-RIP), provides several zonal-mean diagnostics computed from reanalysis data on pressure levels. Diagnostics are currently provided for a variety of reanalyses, including ERA-40, ERA-Interim, ERA-20C, NCEP-NCAR, NCEP-DOE, CFSR, 20CR v2 and v2c, JRA-25, JRA-55, JRA-5...

Vertical profiles of carbon dioxide (CO2) mixing ratio in the equatorial eastern and western Pacific were measured by newly developed balloon-borne CO2 sondes in February 2012 (two soundings) and February–March 2015 (four soundings), respectively. The 1–10 km vertically averaged CO2 mixing ratios lie between the background surface values in the Nor...

Atmospheric solar tides in the stratosphere and the lower mesosphere are investigated using temperature data from five state-of-the-art reanalysis data sets (MERRA-2, MERRA, JRA-55, ERA-Interim, and CFSR) as well as TIMED SABER and Aura MLS satellite measurements. The main focus is on the period 2006–2012 during which the satellite observations are...

The stratospheric response to climate forcing, such as an increase in greenhouse gases, is often unpredictable because of interactions between radiation, dynamics, and chemistry. Climate models are unsuccessful in simulating the realistic distribution of stratospheric water vapor. The long-term trend of the stratospheric age of air (AoA), a measure...

Two of the most basic parameters generated from a reanalysis are temperature and winds. Temperatures in the reanalyses are derived from conventional (surface and balloon), aircraft, and satellite observations. Winds are observed by conventional systems, cloud tracked, and derived from height fields, which are in turn derived from the vertical tempe...

Reanalysis data sets are widely used to understand atmospheric processes and past variability, and are often used to stand in as “observations” for comparisons with climate model output. Because of the central role of water vapor (WV) and ozone (O3) in climate change, it is important to understand how accurately and consistently these species are r...

The SHADOZ network was assembled to validate a new generation of ozone-monitoring satellites and to better characterize the vertical structure of tropical ozone in the troposphere and stratosphere. Beginning with nine stations in 1998, more than 7000 ozone and P-T-U profiles are available from 14 SHADOZ sites that have operated continuously for at...

Atmospheric solar tides in the stratosphere and the lower mesosphere are investigated using temperature data from five state-of-the-art reanalysis data sets (MERRA-2, MERRA, JRA-55, ERA-Interim and CFSR) as well as TIMED/SABER and Aura/MLS satellite measurements. The main focus is on the period 2006–2012 during which the satellite observations are...

We validate the Ozone Monitoring Instrument (OMI) Ozone Profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI row anomaly (RA) on the retrieval by dividing the dataset into before and after the occur...

Increasing interest in climate engineering in recent years has led to calls by the international research community for international research collaboration as well as global public engagement. But making such collaboration a reality is challenging. Here, we report the summary of a 2016 workshop on the significance and challenges of international c...

Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long term data records for deriving O3 trends, model development, satellite validation and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reportin...

Two of the most basic parameters generated from a reanalysis are temperature and winds. Temperatures in the reanalyses are derived from conventional (surface and balloon), aircraft, and satellite observations. Winds are both observed by conventional systems, cloud tracked, and derived from height fields which in turn are derived from the vertical t...

We validate the Ozone Monitoring Instrument (OMI) ozone-profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI Row anomaly (RA) on the retrieval by dividing the data set into before and after the occu...

The climate research community uses atmospheric reanalysis data sets to understand a wide range of processes and variability in the atmosphere, yet different reanalyses may give very different results for the same diagnostics. The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP) is a co...

Interest in climate engineering research has grown rapidly owing to the slow progress of international climate negotiations. As some scientists are proposing to expand research and conduct field tests, there is an emerging debate about whether and how it should proceed. It is widely accepted both by the supporters and critics that public engagement...

A meteorological balloon-borne cloud sensor called the cloud particle sensor (CPS) has been developed. The CPS is equipped with a diode laser at ∼ 790 nm and two photodetectors, with a polarization plate in front of one of the detectors, to count the number of particles per second and to obtain the cloud-phase information (i.e. liquid, ice, or mixe...

In this paper, we describe the construction of the Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database, which includes vertically resolved ozone and water vapor data from a subset of the limb profiling satellite instruments operating since the 1980s. The primary SWOOSH products are zonal-mean monthly-mean time series of water vapo...

Temperature variations in the tropical tropopause layer (TTL) play an important role in dehydration in the upper troposphere and lower stratosphere. Equatorial Kelvin waves associated with the Madden–Julian Oscillation (MJO) are known to induce remarkable temperature variations in the TTL. In this study, the influence of topography on temperature v...

The climate research community uses atmospheric reanalysis data sets to understand a wide range of processes and variability in the atmosphere, yet different reanalyses may give very different results for the same diagnostics. The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP) is a co...

This paper reports on a project to compare the representation of the monthly-mean zonal wind in the equatorial stratosphere among major global atmospheric reanalysis data sets. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and this depends on latitude, longitude, heigh...

A meteorological balloon-borne cloud sensor called the Cloud Particle Sensor (CPS) has been developed. The CPS is equipped with a diode laser at ~ 790 nm and two photo detectors, with a polarization plate in front of one of the detectors, to count the number of particles per second and to obtain the cloud phase information (i.e. liquid, ice, or mix...

In this paper, we describe the construction of the Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database, which includes vertically resolved ozone and water vapor data from limb profiling satellite instruments operating since the 1980’s. SWOOSH includes both individual satellite source data as well as a merged data product. A key as...

This paper reports on a project to compare the representation of the monthly-mean zonal wind in the equatorial stratosphere among major global atmospheric reanalysis datasets. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and this depends on latitude, longitude, height...

The global temperature responses to the eruptions of Mount Agung in 1963, El Chichón in 1982, and Mount Pinatubo in 1991 are investigated using nine currently available reanalysis data sets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR). Multiple linear regression is applied to the zonal and monthly mean time seri...

Previous research has found that conventional radiosondes equipped with a traditional pressure sensor can be subject to a pressure bias, particularly in the stratosphere. This study examines this pressure bias and the resulting altitude misestimation, and its impact on temperature, ozone, and water vapor profiles is considered using data obtained b...

Global temperature response to the eruptions of Mount Agung in 1963, El Chichón in 1982 and Mount Pinatubo in 1991 is investigated using nine reanalysis datasets (JRA-55, MERRA, ERA-Interim, NCEP-CFSR, JRA-25, ERA-40, NCEP-1, NCEP-2, and 20CR). Multiple linear regression is applied to the zonal and monthly mean time series of temperature for two p...