Winter Time 10-20 Day Variations in the Upper Troposphere

Pan, Hua-Lu

doi:10.2151/jmsj1965.65.4_587

Cited by 5 publications

(2 citation statements)

References 38 publications

(49 reference statements)

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“…The short-term quasiperiodic climate change in Taiwan is not only limited to diurnal and seasonal variations, but also intraseasonal low-frequency oscillations. These oscillations may include, for instance, the 10-20-day mode in winter (e.g., Pan 1987) and the 30-60-day north-south oscillation of the Mei-yu front (e.g., Chen and Murakami 1988). The effects of these intraseasonal oscillations on Taiwan rainfall need further study using the ARMTS rainfall data.…”

Section: Seasonal Variationmentioning

confidence: 99%

Diurnal and Seasonal Variations of the Rainfall Measured by the Automatic Rainfall and Meteorological Telemetry System in Taiwan

Chen¹,

Yen²,

Hsieh³

et al. 1999

Bull. Amer. Meteor. Soc.

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Under a weather hazard prevention program in Taiwan, the Vaisala Meteorological Instrument, Inc., of Finland and the Environmental Science and Engineering Corporation of Taiwan jointly developed and installed more than 300 stations of the Automatic Rainfall and Meteorological Telemetry System (ARMTS) over this subtropical island with an area of approximately 30 000 km 2. The Taiwan ARMTS network can provide the hourly rainfall data of not only a densely instrumented, but also very uniquely observed, geographically complex island embedded in the east Asian monsoon environment. The hourly ARMTS rainfall for the period 1993-96 supplemented with the hourly surface winds and pressure observed by 25 conventional surface stations around this island are analyzed to understand three aspects of the diurnal and seasonal variations of Taiwan rainfall. The preliminary results of the analysis are presented in this paper. 1) The maximum daily rainfall occurs at about 1600 ~ 1700 LST, which is about 2-3 h behind the maximum horizontal convergence of surface airmass flux. This time lag suggests that the interaction between mountains and the land-sea breeze circulation may have a timing regulation effect on the maximum daily rainfall. 2) The daily rainfall variations in Taiwan exhibit a bimodality (an early morning minor maximum and an early evening maximum). Although the timing of these two rainfall maxima coincides with the surface pressure minima of semidiurnal variation, the surface pressure tendency analysis does not support this possible cause of the bimodal rainfall variation. The contrast between daily rainfall variation and divergence of surface airmass flux suggests that the early morning rainfall maximum may be induced by the nocturnal drainage flow along the western slope of the Taiwan central mountain range. 3) The seasonal variation of Taiwan rainfall consists basically of a seasonal seesaw between the summer rainfall over west Taiwan and the fall-winter rainfall over northeast Taiwan. Four rainfall regimes over a year are identified around the island. The seasonal transitions of Taiwan rainfall are essentially formed by a counterclockwise rotation of these four rainfall regimes.

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Section: Seasonal Variationmentioning

confidence: 99%

Diurnal and Seasonal Variations of the Rainfall Measured by the Automatic Rainfall and Meteorological Telemetry System in Taiwan

Chen¹,

Yen²,

Hsieh³

et al. 1999

Bull. Amer. Meteor. Soc.

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“…The atmospheric quasi-biweekly mode (QBWM) with a period of approximately 10-20 days is one of the prominent intraseasonal modes in both the tropics and extratropics (e.g., Krishnamurti and Ardanuy 1980;Pan and Zhou 1985;Pan 1987;Chen et al 1995;Li 1996;Fukutomi and Yasunari 2002;Chatterjee and Goswami 2004;Chen and Sui 2010;Zhang et al 2020). From the perspective of atmospheric convection, the QBWM is most active in the tropics with maximum intensity seasonally switching between the two hemispheres (Kikuchi and Wang 2009).…”

Section: Introductionmentioning

confidence: 99%

Maintenance of the Basin-Dependent Quasi-Biweekly Mode in the Indian Ocean during Summer

Yang

et al. 2022

Journal of Climate

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The atmospheric 10–20-day quasi-biweekly mode (QBWM) significantly modulates the active-break spells of the South Asian monsoon. Current knowledge, however, is limited concerning the diversity of the QBWM in the Indian Ocean (IO). Based on extended empirical orthogonal function analysis, two dominant summer modes are constructed in the IO. The first mode (QBWM1) generally depicts IO basin-dependent variability, while the second mode (QBWM2) exhibits a close relationship with the northwestern Pacific. QBWM1 initiates in the equatorial western IO and propagates toward the eastern IO along the equator. Two Rossby wave cells evolve in the off-equatorial eastern IO when convection encounters the Maritime Continent, and subsequently, the northern cell develops and moves westward in the South Asian monsoon region. In contrast, QBWM2 originates in the northwestern Pacific and passes westward across the South Asian monsoon region in the form of convectively-coupled Rossby waves. The maintenance mechanism of the peculiar IO basin-dependent QBWM1 is understood in terms of moisture dynamics. Significant moisture anomalies are found to precondition convection initiation in the western IO and subsequent eastward movement along the equator. Afterward, two off-equatorial moisture centers are generated in the double Rossby wave cells along with convection dissipation in the eastern IO, and the moisture anomalies are delivered from the southern cell toward the convection initiation area in the western IO via a moisture conveyor belt without coupling with convection. Moisture budget analysis indicates that the horizontal moisture advection associated with QBWM1 is regulated by the mean clockwise circulation in the tropical IO.

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Observational climatology and characteristics of wintertime atmospheric blocking over Ural–Siberia

et al. 2012

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Winter Time 10-20 Day Variations in the Upper Troposphere

Cited by 5 publications

References 38 publications

Diurnal and Seasonal Variations of the Rainfall Measured by the Automatic Rainfall and Meteorological Telemetry System in Taiwan

Diurnal and Seasonal Variations of the Rainfall Measured by the Automatic Rainfall and Meteorological Telemetry System in Taiwan

Maintenance of the Basin-Dependent Quasi-Biweekly Mode in the Indian Ocean during Summer

Observational climatology and characteristics of wintertime atmospheric blocking over Ural–Siberia

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