Water vapor control at the tropopause by equatorial Kelvin waves observed over the Galápagos

Fujiwara, Masatomo; Hasebe, Fumio; Shiotani, Masato; Nishi, Noriyuki; Vömel, H.; Oltmans, S. J.

doi:10.1029/2001gl013310

Cited by 73 publications

(70 citation statements)

References 9 publications

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“…9a, but ozone not shown) are indicative of downward stratospheric air transport in association with a downward-displacement phase of equatorial Kelvin waves (e.g. Fujiwara et al, 2001Fujiwara et al, , 2009. Air was dry and cloud free above ∼ 14 km for this reason.…”

Section: Tropical Upper Tropospheric Thin Cirrus Layersmentioning

confidence: 99%

Development of a cloud particle sensor for radiosonde sounding

et al. 2016

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Abstract. 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 mixed). The lower detection limit for particle size was evaluated in laboratory experiments as ∼ 2 µm diameter for water droplets. For the current model the output voltage often saturates for water droplets with diameter equal to or greater than ∼ 80 µm. The upper limit of the directly measured particle number concentration is ∼ 2 cm −3 (2×10 3 L −1 ), which is determined by the volume of the detection area of the instrument. In a cloud layer with a number concentration higher than this value, particle signal overlap and multiple scattering of light occur within the detection area, resulting in a counting loss, though a partial correction may be possible using the particle signal width data. The CPS is currently interfaced with either a Meisei RS-06G radiosonde or a Meisei RS-11G radiosonde that measures vertical profiles of temperature, relative humidity, height, pressure, and horizontal winds. Twenty-five test flights have been made between 2012 and 2015 at midlatitude and tropical sites. In this paper, results from four flights are discussed in detail. A simultaneous flight of two CPSs with different instrumental configurations confirmed the robustness of the technique. At a midlatitude site, a profile containing, from low to high altitude, water clouds, mixed-phase clouds, and ice clouds was successfully obtained. In the tropics, vertically thick cloud layers in the middle to upper troposphere and vertically thin cirrus layers in the upper troposphere were successfully detected in two separate flights. The data quality is much better at night, dusk, and dawn than during the daytime because strong sunlight affects the measurements of scattered light.

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Section: Tropical Upper Tropospheric Thin Cirrus Layersmentioning

confidence: 99%

Development of a cloud particle sensor for radiosonde sounding

et al. 2016

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“…According to the hypothesis of the dehydration pump by Kelvin waves (Fujiwara et al, 2001), the water vapor in the TTL during the campaign period will be saturated so that the intrusion of tropospheric moist air is inhibited by the closed "valve" shut off by Kelvin waves. Figure 4 shows the vertical distributions of the water vapor mixing ratio (thick lines) given by CFH (solid) and SW (dashed), the SMR (thin lines), the ozone mixing ratios (dotted lines), and the potential temperature (dash-dot lines) observed at Bandung (top) and Tarawa (bottom).…”

Section: Analysis Of the Water Vapor Sonde Datamentioning

confidence: 99%

“…These waves are shown to work as a "dehydration pump" that introduces dry stratospheric air into the uppermost troposphere on the one hand and blocks the entry of humid tropospheric air into the stratosphere on the other due to adiabatic temperature change associated with the vertical displacement (Hasebe et al, 2000;Fujiwara et al, 2001). In case of wave breaking, irreversible mixing in the upper troposphere leaves it under the influence of ozone rich/dry stratospheric air.…”

Section: Introductionmentioning

confidence: 99%

In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific

et al. 2007

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Abstract. Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90 • S, 107.60 • E) and Tarawa, Kiribati (1.35 • N, 172.91 • E) in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL). Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

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“…Using simulations and global observational data, Ryu et al (2008) found that the vertically propagating Kelvin waves play a pivotal role in the tropical tropopause height variability. Kelvin waves are also known in affecting the distribution of water vapor and the formation of clouds in the TTL region (Fujiwara et al, 2001;Zhou and Holton, 2002;Eguchi and Shiotani, 2004;Fueglistaler et al, 2009), even TTL upwelling is linked to the Kelvin waves (Ryu and Lee, 2010). Besides, Kelvin waves with shorter periods can propagate into the thermosphere and the ionosphere and then affect neutral and electron densities (Takahashi et al, 2007;Chang et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Variations of Kelvin waves around the TTL region during the stratospheric sudden warming events in the Northern Hemisphere winter

et al. 2016

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Abstract. Spatial and temporal variabilities of Kelvin waves during stratospheric sudden warming (SSW) events are investigated by the ERA-Interim reanalysis data, and the results are validated by the COSMIC temperature data. A case study on an exceptionally large SSW event in 2009, and a composite analysis comprising 18 events from 1980 to 2013 are presented. During SSW events, the average temperature increases by 20 K in the polar stratosphere, while the temperature in the tropical stratosphere decreases by about 4 K. Kelvin wave with wave numbers 1 and 2, and periods 10-20 days, clearly appear around the tropical tropopause layer (TTL) during SSWs. The Kelvin wave activity shows obvious coupling with the convection localized in the India Ocean and western Pacific (Indo-Pacific) region. Detailed analysis suggests that the enhanced meridional circulation driven by the extratropical planetary wave forcing during SSW events leads to tropical upwelling, which further produces temperature decrease in the tropical stratosphere. The tropical upwelling and cooling consequently result in enhancement of convection in the equatorial region, which excites the strong Kelvin wave activity. In addition, we investigated the Kelvin wave acceleration to the eastward zonal wind anomalies in the equatorial stratosphere during SSW events. The composite analysis shows that the proportion of Kelvin wave contribution ranges from 5 to 35 % during SSWs, much larger than in the non-SSW mid-winters (less than 5 % in the stratosphere). However, the Kelvin wave alone is insufficient to drive the equatorial eastward zonal wind anomalies during the SSW events, which suggests that the effects of other types of equatorial waves may not be neglected.

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Water vapor control at the tropopause by equatorial Kelvin waves observed over the Galápagos

Cited by 73 publications

References 9 publications

Development of a cloud particle sensor for radiosonde sounding

Development of a cloud particle sensor for radiosonde sounding

In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific

Variations of Kelvin waves around the TTL region during the stratospheric sudden warming events in the Northern Hemisphere winter

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