Observed features b)NCEP/NCAR storm tracks 90N 60N 30N EO 60E 120E 180 120W 60 Shaded:standard eviation of 24-h filtered 500-hl geopotential height ontour interval 20 m)computed from the Januaries of 982-1994(NCEP/NCAR reanaly is) (From Chang's homepage) Two storm track zones in N.H. Fig.7.9.The tracks of low pressure centres over the North Atlantic for the period December 1985 to February 1986.The shading indicates the region where the high frequency元l/ exceeded 90m in the ECMWF analyses for the same period. 授课教师：张洋 6
授课教师：张洋 6 Observed features 224 Three-dimensional aspects of the global circulation Fig. 7.9. The tracks of low pressure centres over the North Atlantic for the period December 1985 to February 1986. The shading indicates the region where the high frequency Za exceeded 90 m in the ECMWF analyses for the same period. 'storm track' as observed in the northern hemisphere, namely, the elongated maximum in geopotential height variance, the large vertical temperature flux at low levels, and the dipolar structure of the poleward momentum flux towards the downstream end of the storm track. Attempts to correlate the tracks of synoptic systems with the variance maximum are less successful than in the northern hemisphere. There is a tendency for the cyclonic systems to spiral polewards from cyclogenesis regions on the equatorward flank of the 'storm track' to decay regions in the 'circumpolar trough', the region of low pressure around the Antarctic coast. Partly at least, this is the result of attempting to identify the centres of synoptic weather systems by means of extrema in the surface pressure field. Because the surface wind field is strong around the southern hemisphere baroclinic zone, there is a natural tendency for centres of low pressure to be displaced poleward of the vortex centre, and for centres of high pressure to be displaced equatorward. But, partly, it seems that this spiral trajectory of weather systems is real. Perhaps it would be better to describe the regions of large high frequency variance as 'storm zones' rather than 'storm tracks'. However, the latter nomenclature is in general use despite being rather misleading. Each of the three major storm zones has a distinctive seasonal behaviour. Shaded: standard deviation of 24-h filtered 500-hPa geopotential height (contour interval 20 m) computed from the Januaries of 1982-1994 (NCEP/NCAR reanalysis) Two storm track zones in N.H. (From Chang’s homepage)
Observed features b)NCEP/NCAR storm tracks 90N 60N The storm zones occur in 30N association with the jet EO streams; 60E 120E 180 120W 60W 0 DJF mean at 500 hpa from 1980 to 2000 NP 60N The storm zones are most 295 intense near the longitude of 30N the jet exits. EQ 50 100 150 200 250 300 350 Zonal wind from NCEP/NCAR data 授课教师：张洋7
授课教师：张洋 7 Observed features − 5 10 15 15 20 25 20 −5 30 0 5 10 20 25 10 35 10 10 DJF mean at 500 hpa from 1980 to 2000 0 50 100 150 200 250 300 350 EQ 30N 60N NP Zonal wind from NCEP/NCAR data The storm zones occur in association with the jet streams; The storm zones are most intense near the longitude of the jet exits
Observed features b)NCEP/NCAR storm tracks 90N Temperature distribution from NCEP/NCAR data 60N DJF mean at 850 hpa from 1980 to 2000 NP 30N 60N EO 60E 120E 180 120W 60W 0 30N DJF mean at 500 hpa from 1980 to 2000 EQ NP 50 100 150 200 250 300 350 60N DJF mean at 500 hpa from 1980 to 2000 NP 295 60N 30N 30N 260 EQ 50 100 150 200 250 300 350 EQ 50 100 150 200 250 300 350 授课教师：张洋 8
授课教师：张洋 8 Observed features − 5 10 15 15 20 25 20 −5 30 0 5 10 20 25 10 35 10 10 DJF mean at 500 hpa from 1980 to 2000 0 50 100 150 200 250 300 350 EQ 30N 60N NP − 5 10 15 15 20 25 20 −5 30 0 5 10 20 25 10 35 10 10 DJF mean at 500 hpa from 1980 to 2000 235 240 250 260 0 50 100 150 200 250 300 350 EQ 30N 60N NP 250 255 265 275 285 290 250 DJF mean at 850 hpa from 1980 to 2000 0 50 100 150 200 250 300 350 EQ 30N 60N NP Temperature distribution from NCEP/NCAR data
及图 Observed features 3.00 (b)Track Density 0.0 (c)Genesis Density 0.20 0.00 Using ECMWF,MSLP. from Hoskins and Hodges,2002 授课教师：张洋 9
授课教师：张洋 9 15 MARCH 2002 HOSKINS AND HODGES Observed features 1049 FIG. 5. Attributes for the tracking of negative, cyclonic MSLP features: (a) feature density, (b) track density, (c) genesis density, (d) lysis density, (e) mean intensity (hPa), (f ) mean growth rate (day 1), (g) mean velocity (m s1), and (h) mean lifetime (days). Feature density suppression threshold is 0.5, track density suppression threshold is 0.2. 15 MARCH 2002 HOSKINS AND HODGES 1049 FIG. 5. Attributes for the tracking of negative, cyclonic MSLP features: (a) feature density, (b) track density, (c) genesis density, (d) lysis density, (e) mean intensity (hPa), (f ) mean growth rate (day 1), (g) mean velocity (m s1), and (h) mean lifetime (days). Feature density suppression threshold is 0.5, track density suppression threshold is 0.2. Using ECMWF, MSLP, from Hoskins and Hodges, 2002
及金乐 Observed features 7=仙≈03发 Eddy kinetic energy 0.9 (a) (b) 1350 0.8 300 250 0.5 200 150 0 02 100 0. 50 Fig.2.Left:the Eady growth rate,oL,at 500 hPa in units of I/days.Right:The average eddy kinetic energy at 250 hPa in units of (m/s)2.Both are for the Northern Hemisphere winter (DJF),computed from the NCEP/NCAR re-analysis.The maxima in EKE are downstream of the maxima in growth rate,and the Pacific storm track does not fully decay before the beginning of the Atlantic storm track.The prime meridian (Greenwich)is at 6 O'clock. from Vallis and Gerber,2008 授课教师：张洋10
授课教师：张洋 10 Observed features from Vallis and Gerber, 2008 = kci ⇡ 0.3 ⇤fo N Eddy kinetic energy