Shin-Ya Ogino

Climatological Description of Seasonal Variations in Lower-Tropospheric Temperature Inversion Layers over the Indochina Peninsula

Abstract In this study operational rawinsonde data are used to investigate climatological features of seasonal variations in static stability in order to understand the behavior of temperature inversion layers, that is, extremely stable layers in the lower troposphere over the Indochina Peninsula region, at the southeastern edge of the Asian continent. Static stability was evaluated from the vertical gradient in potential temperature (Δθ/Δz). Stable (Δθ/Δz > 10 K km−1) and unstable (Δθ/Δz < 1 K km−1) layers frequently appear over the Indochina Peninsula region during boreal winter. Temporal and vertical variations in stability during the boreal winter can be categorized into three characteristic types, type I: the mean height of stable layers increases from 2 to 5 km from the dry to the rainy season over inland areas of the Indochina Peninsula and southern China; type II: similar to type I, with the additional occurrence of stable layers at a height of ∼1 km, mainly over coastal areas of the Indochina Pen...

Inertio-gravity waves and subtropical multiple tropopauses: Vertical wavenumber spectra of wind and temperature observed by the MU radar, radiosondes and operational rawinsonde network

Abstract We have carried out continuous observations of the tropopause region over Japan for three weeks during the Baiu (early summer rain “in Japan”) season in 1991, by using a VHF Doppler radar (the MU radar), radiosondes launched at the radar site and operational rawinsondes at five meteorological stations. Based on these observations, we try to examine the hypothesis that the multiple tropopauses and the dominant inertio-gravity waves are one and the same feature, and obtain some interesting results that are not inconsistent with this hypothesis. First, vertical wavenumber spectra and hodographs analyzed from the radar wind data in the tropopause region suggest that inertio-gravity waves with vertical wavelengths of ∼ 2 km are quasi-monochromatically dominant (with 2–3 day scale variabilities of 10–20%), and are in accordance with activities of the subtropical jet stream and mesoscale cyclone-front system activities observed by the operational network. Second, striking (potential) temperature fluctuations are detected simultaneously by the radiosondes and rawinsondes, which appear as multiple tropopauses in meridional cross-section analysis. Third, vertical wavenumber spectra analyzed from the radiosonde temperature data are consistent with the radar wind spectrum, if we assume that both wind and temperature fluctuations are mainly induced by the dominant inertio-gravity waves. Finally, we confirm that the dominant interio-gravity waves can be barely detected also from routine rawinsonde (1.5-km running-mean) wind data if the amplitude is larger than 1.5 m/s. However, the monochromatic wave structures are generally quite localized in space and time.

First Reprocessing of Southern Hemisphere Additional Ozonesondes (SHADOZ) Ozone Profiles (1998–2016): 2. Comparisons With Satellites and Ground‐Based Instruments

Abstract The Southern Hemisphere ADditional OZonesonde (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 7,000 ozone and P-T-U profiles are available from 14 SHADOZ sites that have operated continuously for at least a decade. We analyze ozone profiles from the recently reprocessed SHADOZ data set that is based on adjustments for inconsistencies caused by varying ozonesonde instruments and operating techniques. First, sonde-derived total ozone column amounts are compared to the overpasses from the Earth Probe/Total Ozone Mapping Spectrometer, Ozone Monitoring Instrument, and Ozone Mapping and Profiler Suite satellites that cover 1998-2016. Second, characteristics of the stratospheric and tropospheric columns are examined along with ozone structure in the tropical tropopause layer (TTL). We find that (1) relative to our earlier evaluations of SHADOZ data, in 2003, 2007, and 2012, sonde-satellite total ozone column offsets at 12 stations are 2% or less, a significant improvement; (2) as in prior studies, the 10 tropical SHADOZ stations, defined as within ±19° latitude, display statistically uniform stratospheric column ozone, 229 ± 3.9 DU (Dobson units), and a tropospheric zonal wave-one pattern with a 14 DU mean amplitude; (3) the TTL ozone column, which is also zonally uniform, masks complex vertical structure, and this argues against using satellites for lower stratospheric ozone trends; and (4) reprocessing has led to more uniform stratospheric column amounts across sites and reduced bias in stratospheric profiles. As a consequence, the uncertainty in total column ozone now averages 5%.

Coordinated Upper-troposphere-to-stratosphere Balloon Experiment in Biak (CUBE/Biak)

Capsule SummaryThis article introduces CUBE/Biak, a big-balloon air sampling campaign conducted in Indonesia, describing from the scientific scope in historical perspective through challenges in campaign coordination.

Tropical Coastal Dehydrator in Global Atmospheric Water Circulation

We present a conceptual advance of the global water cycle in which the precipitation concentrated in tropical coastlines plays the role of an atmospheric dehydrator between the ocean and land. Landward water vapor transport peaks as it enters the coastal region (a few hundred kilometers offshore), and about half of the water vapor is consumed as precipitation over the coastal region before reaching the inland. Our results also revealed that the significant amount of net freshwater is supplied from the atmosphere to the coastal ocean, which is comparable to that of the land water discharge. This fact further provides a new insight on the ocean salinity distribution and its associated dynamics. We discuss a possible link between the tropical land distribution and the Earths climate through the water circulation.

Seasonal Changes in a Vertical Thermal Structure Producing Stable Lower-Troposphere Layers over the Inland Region of the Indochina Peninsula

AbstractThe authors performed a thermal budget analysis to understand the nature of seasonal changes in stable lower-troposphere layers over the inland region of the Indochina Peninsula, using atmospheric reanalysis data. The analysis focuses on subseasonal stable layers. Stability increase in the generation of stable layers is classified into three dominant thermal factors: vertical differences in horizontal potential temperature advection, vertical potential temperature advection, and their residual component Q1. The largest contributor to the stability increase is defined as the dominant thermal factor. Climatological typical heights where stable layers most frequently appear are the 850–700-, 700–600-, and 600–500-hPa levels in November–January, February–March, and April, respectively, according to a previous study. From November to January, most of the stable layers in the typical height are generated by vertical differences in horizontal potential temperature advection. Their generation (dissipation...

Lower-Stratospheric and Upper-Tropospheric Disturbances Observed by Radiosondes over Thailand during January 2000

Abstract Lower-stratospheric and upper-tropospheric disturbances over Thailand during 12–21 January 2000 were studied using the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment-Tropics (GAME-T) intensive rawinsonde observations with fine temporal sampling intervals of 3 h. Analysis was focused on the wind disturbances with a period shorter than about 10 days. Frequency spectra showed three distinct peaks: a 1-day period above a height of 20 km, a near-inertial period around 19 and 27 km, and periods of 2.5–9 days (or longer) in the height range of 12–17 km. The wave with a 1-day period was interpreted as a diurnal tide. A comparison with the migrating tide in the global-scale wave model showed that the observational results had larger amplitude and shorter vertical wavelength than the model. The difference between the observation and the model may be caused by the superposition of the nonmigrating tide. The wave with the near-inertial period was interpreted as an internal inertial...

Horizontal variations of gravity wave activities in the lower stratosphere over Japan: A case study in the Baiu season 1991

Vertical wavenumber spectra are analyzed by using temperature, zonal wind and meridional wind data obtained with MU radar and radiosondes at the MU observatory in Shigaraki and with operational rawinsondes at five stations over Japan. The temperature and meridional wind spectral power densities of the dominant gravity wave increase with a decrease of latitude, whereas the zonal wind spectral power seems to have a maximum near the tropopausal jet stream axis. An analysis technique to estimate a characteristic value of intrinsic frequency from the wind and temperature vertical-wavenumber spectra is proposed. The different meridional distributions of spectral power densities for temperature, zonal wind and meridional wind possibly can be explained by a latitudinal distribution of the characteristic intrinsic frequency.

Cold surge event observed by radiosonde observation from the research vessel “Hakuho-maru” over the Philippine Sea in December 2012

AbstractThe thermal energy transfer from the sea surface to the atmosphere associated with a cold surge event was investigated with observations from radiosondes on the research vessel “Hakuho-maru” over the Philippine Sea in December 2012. These observations were analyzed, and the results were compared with those obtained from observations over the East China Sea in the Air Mass Transformation Experiment in 1974 (AMTEX ‘74). The horizontal advection of cold and dry air associated with the cold surge dominated at heights below 850 hPa. In spite of this strong advection, the local temporal variations in the temperature and moisture were small, because the advection was balanced by the transfer of heat and moisture from the sea surface, which is qualitatively the same behavior as observed during the cold surge event in AMTEX ‘74. The eddy transport of the total heat energy from the sea surface to the atmosphere was estimated at about 410 W/m2, which is about half of the maximum value of 780 W/m2 observed during AMTEX ‘74. This result shows the existence of considerable heat transfer from the sea surface to the atmosphere over the Philippine Sea, which is the downstream region of the cold surge, after it passed through the East China Sea.

Development and decay processes of dual inversion layers in winter over the northwest coast of the South China Sea

AbstractInversion layers in the lower troposphere appear centered at two heights, 1.5 and 4 km, over the northwestern coast of the South China Sea in late boreal winter. The mechanisms of these dua...