ORCID Profile
0000-0002-2228-0088
Current Organisation
Japan Agency for Marine-Earth Science and Technology
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Publisher: Proceedings of the National Academy of Sciences
Date: 26-10-2015
Abstract: We estimate that stratospheric sulfate aerosol geoengineering may somewhat ameliorate Atlantic hurricane intensity and frequency, but there will be more “Katrina”-level events than during the past 30 y. Geoengineering would likely be reasonably effective at controlling coastal flood risk relative to the coastal flood risk expected under the Representative Concentration Pathway (RCP) 4.5 greenhouse gas warming, in part, due to its impact on global sea level rise, although flood risk would still be significantly larger than at present.
Publisher: American Geophysical Union (AGU)
Date: 27-05-2013
DOI: 10.1002/JGRD.50316
Publisher: IOP Publishing
Date: 03-2017
Publisher: American Geophysical Union (AGU)
Date: 08-07-2014
DOI: 10.1002/2013JD021403
Publisher: Copernicus GmbH
Date: 19-01-2018
Abstract: Abstract. Here we show results from Earth system model simulations from the marine cloud brightening experiment G4cdnc of the Geoengineering Model Intercomparison Project (GeoMIP). The nine contributing models prescribe a 50 % increase in the cloud droplet number concentration (CDNC) of low clouds over the global oceans in an experiment dubbed G4cdnc, with the purpose of counteracting the radiative forcing due to anthropogenic greenhouse gases under the RCP4.5 scenario. The model ensemble median effective radiative forcing (ERF) amounts to −1.9 W m−2, with a substantial inter-model spread of −0.6 to −2.5 W m−2. The large spread is partly related to the considerable differences in clouds and their representation between the models, with an underestimation of low clouds in several of the models. All models predict a statistically significant temperature decrease with a median of (for years 2020–2069) −0.96 [−0.17 to −1.21] K relative to the RCP4.5 scenario, with particularly strong cooling over low-latitude continents. Globally averaged there is a weak but significant precipitation decrease of −2.35 [−0.57 to −2.96] % due to a colder climate, but at low latitudes there is a 1.19 % increase over land. This increase is part of a circulation change where a strong negative top-of-atmosphere (TOA) shortwave forcing over subtropical oceans, caused by increased albedo associated with the increasing CDNC, is compensated for by rising motion and positive TOA longwave signals over adjacent land regions.
Publisher: American Meteorological Society
Date: 15-02-2016
Abstract: Southern Hemisphere extratropical gravity wave activity is examined using simulations from a free-running middle-atmosphere general circulation model called Kanto that contains no gravity wave parameterizations. The total absolute gravity wave momentum flux (MF) and its intermittency, diagnosed by the Gini coefficient, are examined during January and July. The MF and intermittency results calculated from the Kanto model agree well with results from satellite limb and superpressure balloon observations. The analysis of the Kanto model simulations indicates the following results. Nonorographic gravity waves are generated in Kanto in the frontal regions of extratropical depressions and around tropopause-level jets. Regions with lower (higher) intermittency in the July midstratosphere become more (less) intermittent by the mesosphere as a result of lower-level wave removal. The gravity wave intermittency is low and nearly homogeneous throughout the SH middle atmosphere during January. This indicates that nonorographic waves dominate at this time of year, with sources including continental convection as well as oceanic depressions. Most of the zonal-mean MF at 40°–65°S in January and July is due to gravity waves located above the oceans. The zonal-mean MF at lower latitudes in both months has a larger contribution from the land regions but the fraction above the oceans remains larger.
No related grants have been discovered for Shingo Watanabe.