HR: 0830h
AN: A31C-0050    [PDF]
TI: Cyclone Activity associated with the Summer Precipitation Dipole Pattern over Northern Eurasia
AU: * Fukutomi, Y
EM: fukutomi@jamstec.go.jp
AF: Frontier Research System for Global Change, JAMSTEC Yokohama Institute for Earth Sciences, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Masuda, K
EM: masuda@jamstec.go.jp
AF: Frontier Research System for Global Change, JAMSTEC Yokohama Institute for Earth Sciences, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Yasunari, T
EM: yasunari@ihas.nagoya-u.ac.jp
AF: Frontier Research System for Global Change, JAMSTEC Yokohama Institute for Earth Sciences, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Yasunari, T
EM: yasunari@ihas.nagoya-u.ac.jp
AF: Hydrospheric Atmosheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
AB: An east--west seesaw-like oscillation of dry and wet extremes is a marked characteristic of interannual variability of summer (June--August) precipitation in Siberia (Fukutomi et al. 2003a, JHM). They found an out-of-phase relationship in the temporal and spatial signature of basin-scale precipitation between eastern and western Siberia (ES and WS), which is characterized by an east-west dipole pattern across northern Eurasia. This interannual seesaw with about 6--8-yr timescale has been pronounced in recent 30 years. The formation of the Siberian precipitation dipole anomalies may be related to interannual changes in extratropical cyclone activity. From this viewpoint, this study examines mid-tropospheric cyclone activity and cyclone tracks involved in two opposite phases of the precipitation dipole that are out-of-phase with each other (ES-wet--WS-dry and WS-wet--ES-dry). To accomplish this, the global cyclone climatology data for the period 1957--1997 (Key and Chan 1999, GRL) was employed. Additionally, the NCEP--CPC global land precipitation (PREC/L) data, and the NCEP/NCAR reanalysis data were used. First, we selected four ES-wet--WS-dry summers (1974, 1981, 1988, and 1989) and four WS-wet--ES-dry summers (1979, 1986, 1992, and 1996）based on the Siberian precipitation seesaw index (Fukutomi et al. 2003b, submitted). Then a composite analysis is performed on the 500mb cyclone frequency and cyclone tracks for these phases. The results present a coherent picture of cyclone behavior with the east-west contrastive structure of the summer precipitation distribution over northern Eurasia. Composite field of anomalous cyclone frequency exhibits quite similar east-west dipole pattern across northern Eurasia with that of precipitation. The number of cyclones increases (decreases) in the vicinity of above (below) normal precipitation region. Tracks of cyclones moving into the Siberian domain for the ES-wet--WS-dry phases pass trough central Siberia (CS), and mainly originate in the WS region and Kara Sea. On the other hand, those for the WS-wet--ES-dry phases cross predominantly over WS, and these systems come from European Russia and Barents Sea. In this situation, the cyclone track density is quite low over ES. The interannual variability of the summer cyclone frequency in the WS (CS--ES) box significantly correlates with that of the basin-averaged summer precipitation for WS (ES). In summary, our results suggest that the appearance of the Siberian precipitation dipole pattern strongly depends on the high-latitude cyclone activity.
DE: 1620 Climate dynamics (3309)
DE: 1655 Water cycles (1836)
DE: 3319 General circulation
DE: 3354 Precipitation (1854)
DE: 3364 Synoptic-scale meteorology
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting