Impact of Synthetic Wind Retrieval on Tropical Cyclone Structures at the Extratropical Transition Stage in the JRA-25 Reanalysis

Kitabatake, Naoko

doi:10.2151/sola.2010-020

Cited by 2 publications

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“…The time when parameter B exceeds 10 during or after the recurvature is defined as the beginning (onset) of ET. Although a bogus vortex is implemented for a TC in the JRA-25 (Hatsushika et al 2006;Onogi et al 2007), termination of the bogus implementation associated with ET completion is considered to have practically no impact on the judgment of ET (Kitabatake 2010).…”

Section: Methodsmentioning

confidence: 99%

“…Since the major advantage of the Japanese 25-year Reanalysis (JRA-25) dataset (Onogi et al 2007) is the representation of TC structures (Hatsushika et al 2006), we use it in this study. Although the implementation of an artificial vortex, that is a TC bogus, may result in artificial discontinuity of the storm structure before and after ET, Kitabatake (2010) demonstrated that the impact from removal of a bogus vortex at the completion of ET is very small and practically negligible.…”

Section: Introductionmentioning

confidence: 99%

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Climatology of Extratropical Transition of Tropical Cyclones in the Western North Pacific Defined by Using Cyclone Phase Space

Kitabatake¹

2011

Journal of the Meteorological Society of Japan

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Tropical cyclones (TCs) in the western North Pacific are examined to present climatology of their extratropical transition (ET) during the period of 1979-2004. Two parameters of the cyclone phase space (CPS) are calculated using the Japanese 25-year Reanalysis (JRA-25) dataset as indices of ET for the TCs in the best track data from the Japan Meteorological Agency. The onset and the completion of ET are defined as the beginning of an increase in thermal asymmetry and the evolution from the warm to the cold-core structure, respectively. Forty percent of all TCs are assumed to complete ET. The mean transition period from the ET onset until ET completion is estimated to be about 18 hrs, although 16.8% of all ET storms are transformed into the cold-core structure before the increase in thermal asymmetry. Meridional fluctuation in the location of ET completion by season attains its peak in August, while the peak of ET events occurs in September-October with regards to the ratio of ET frequency to all TCs, the transition period, and intensity at the time of ET completion.The background environment of ET events are also examined using the monthly mean of the JRA-25 and sea surface temperature of the centennial in situ observation-based estimates (COBE). Both air-sea thermal contrast and the tropospheric vertical shear are greater in autumn than in the Baiu season and summer. The results suggest that, whereas a TC can translate into higher latitudes with a warm-core structure in an environment of weak vertical shear and small air-sea contrast in summer, it tends to complete ET in lower latitudes in an environment of strong vertical shear and large air-sea contrast in autumn-winter. These characteristics of ET affect the seasonal variation in the structure of landfalling TCs on the main islands of Japan.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Climatology of Extratropical Transition of Tropical Cyclones in the Western North Pacific Defined by Using Cyclone Phase Space

Kitabatake¹

2011

Journal of the Meteorological Society of Japan

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Parameter Spaces of Environmental Fields Responsible for Cyclone Development from Tropics to Extratropics

et al. 2014

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Objective cyclone tracking applied to a 30-yr reanalysis dataset shows that cyclone development in the summer and autumn seasons is active in the tropics and extratropics and inactive in the subtropics. To understand this geographically bimodal distribution of cyclone development associated with tropical and extratropical cyclones quantitatively, the direct relationship between cyclone types and their environments are assessed by using a parameter space of environmental variables [environmental parameter space (EPS)]. The number of cyclones is analyzed in terms of two different factors: the environmental conditions favorable for cyclone development and the area size that satisfies the favorable condition. The EPS analysis is mainly conducted for two representative environmental parameters that are commonly used for cyclone analysis: potential intensity for tropical cyclones and baroclinicity for extratropical cyclones. The geographically bimodal distribution is attributed to the high sensitivity of the cyclone development to the change in the environmental fields from tropics to extratropics. In addition, the bimodal distribution is partly attributed to the rapid change in the environmental fields from tropics to extratropics. The EPS analysis also shows that other environmental parameters, including relative humidity and vertical velocity, may enhance the contrast between the tropics (extratropics) and subtropics, whereas they are not essential for determining cyclone types. The relationship between cyclones and their environments is found to be similar between the hemispheres in the EPS, although the geographical distribution, particularly the longitudinal uniformity, is markedly different between the hemispheres.

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Impact of Synthetic Wind Retrieval on Tropical Cyclone Structures at the Extratropical Transition Stage in the JRA-25 Reanalysis

Cited by 2 publications

References 8 publications

Climatology of Extratropical Transition of Tropical Cyclones in the Western North Pacific Defined by Using Cyclone Phase Space

Climatology of Extratropical Transition of Tropical Cyclones in the Western North Pacific Defined by Using Cyclone Phase Space

Parameter Spaces of Environmental Fields Responsible for Cyclone Development from Tropics to Extratropics

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