9595 年年 55 月月 1212 日於文化大學大氣科學系日於文化大學大氣科學系

陳 泰 然陳 泰 然

國立台灣大學大氣科學系國立台灣大學大氣科學系

從挪威學派談起：從挪威學派談起：溫帶氣旋的結構與演變溫帶氣旋的結構與演變

Fig. 1. Idealized cyclone (Bjerknes and Solberg 1922).

Fig. 2. The life cycle of cyclones (Bjerknes and Solberg 1922).

Fig. 3. “The ‘zonal cross-section,’ evening of the 15th of February, 1953” (Bjerknes and Palmén 1937).

Fig. 4. Upper panel: Cross sectional (time series) analysis of BAO wind tower temperature and wind measurements, Lower panel: Corresponding analysis of vertical motion. Note the distance scale in lower right (Shapiro 1984).

C ~ 17 m s-1

L ~ 170 m

ωmax ~ 5 m s-1 at 300 m

Fig. 5. Schematic diagram of the cloud patterns associated with an extratropical cyclone at four stages of development. Dashed lines indicate cirrostratus cloud decks, cross-hatching frontal cloud bands, arrowsheads show low- or middle-level cloud decks. (Adapted from lecture notes of Roger B. Weldon by Wallace and Hobbs 1977, p. 262.)

Fig. 6. Surface analysis for (a) 06 UTC 7 January, (b) 18 UTC 7 January, and (c) 06 UTC 8 January 1981 (Mullen 1983).

Fig. 7. 920-mb temperature (°C, solid lines) and geopotential height (m, dashed lines) analysis at ~12 UTC 27 January 1988. NOAA P-3 920-mb flight track, small- dotted lines with plotted wind vectors. Dropwindsonde development positions denoted by triangles. 920-mb temperatures plotted at rawinsonde and dropwindsonde positions. Warm and cold front boundaries indicated with conventional symbols. Line AA’, segment of cross-section projection line for Fig. 10.21.

Fig. 8. An observational study of a lower tropospheric front, taken from S55. Slightly thicker continous lines denote the boundaries of the region of very strong gradients, continous lines are isolines of potential temperature (contour interval, 5 K), and broken lines are isolines of long-front velocity (contour interval, 10 m s -1).

Fig. 9. (a) Horizontal distribution of streamlines (solid) and isotherms (dashed) in a frontogenetic confluence. (b) Vertical section showing confluent flow and the induced transverse ageostrophic circulation required to maintain thermal wind balance under the frontogenetical action (Sawyer 1956).

Fig. 10. Distribution of 1000 mb contour height at 200-ft intervals (solid lines) and 500-mb temperature at 5°C intervals (dashed lines) at 20 days (Phillips 1956). Fronts (added) have been subjectively located on the basis of the contour and isotherm configurations.

Fig. 11. Upper-level frontogenesis in a two-region semigeostrophic model. Solid lines, potential isotherms (interval 7.8 K); dashed lines, isotachs (interval 10.5 m s-1). Richardson number contour value of 1.0 is indicated by small circles (Hoskins 1971).

Fig. 12. Cross sections of the transverse ageostrophic circulation and potential temperature after the 24-h integration of a two-dimensional primitive equation model of frontogenesis due to (a) pure confluence and (b) confluence in the presence of upper-level cold advection (Keyser and Pecnick 1985).

Fig. 13. Nonlinear semigeostrophic simulation of a baroclinic development from a small-amplitude disturbance to a cyclone. The diagrams show the surface fields of potential temperature (solid lines) and pressure (dashed lines) in a domain of 8000 × 4000 km. The contour interval is 2 K for potential temperature and 3 mb for pressure. The time interval between (a) and (c) is 96 h (Schär 1989).

Fig. 14. The life cycle of the marine extratropical frontal cyclone: (I) incipient frontal cyclone; (II) frontal fracture; (III) bent-back warm front and frontal T-bone; (IV) warm-core frontal. seclusion. Upper: sea-level pressure, solid lines; fronts, bold lines; and cloud signature, shaded. Lower: temperature, solid lines; cold and warm air currents, solid and dashed arrows, respectively.

Fig. 15. Idealized schematic depiction on a constant pressure surface of the propagation of an upper-tropospheric jet-front system through a midlatitude baroclinic wave over a 72-h period: (a) formation of jet front in the confluence between mid- and high-latitude currents, (b) jet front situated in the northwesterly flow inflection of amplifying wave, (c) jet front at the base of the trough of fully developed wave, and (d) jet front situated in the southwesterly flow inflection of damping wave. Geopotential height contours, thick solid lines; isotachs, thick dashed lines; isentropes or isotherms, thin dashed lines. From Shapiro (1983).