Synoptic I – ATMS 410

1. Synoptic I – ATMS 410 • Tropical-extratropical connections (LP#4) • Teleconnections • Definition • Impact of atmospheric oscillations

2. Synoptic I – ATMS 410 • Introduction • Baseball perspective; “tipping your pitches” • Makes it easier for a hitter to predict the type of pitch about to be thrown • Gives hitter an advantage http://sportsillustrated.cnn.com/2004/writers/john_donovan/05/12/tipping.pitches/

3. Synoptic I – ATMS 410 • Review • Note the differences in time scales… MJO PDO 40-50 days 20-30 years Synoptic-scale cyclones  3 – 5 days Although weather in the tropics is generally less predictable than in the extratropics, the tropical oscillations tend to be long-lived and, if their interactions with the extratropics can be understood, observations of tropical oscillations can aid in our extratropical weather forecasts

4. Synoptic I – ATMS 410 • In other words, why do we care about tropical oscillations in a course focusing on the extratropics (mid-latitudes)? • Example…recall the relatives who visit for an extended stay • Aunt Matilda and Uncle Billy visit your house for four weeks, what do you predict will happen in your household after the first week of their visit?

5. Synoptic I – ATMS 410 • In the previous lecture packet, we explored… (a) (b) (c) (d) • = undisturbed climatological flow • = long term changes in the climatological flow • = quasi-stationary long waves • = shortwaves and cyclones

6. Synoptic I – ATMS 410 • In this lecture packet, we want to improve our forecasts of… (a) (b) (c) (d) • = undisturbed climatological flow • = long term changes in the climatological flow • = quasi-stationary long waves • = shortwaves and cyclones

7. Synoptic I – ATMS 410 • Review…must properly conserve:

8. Synoptic I – ATMS 410 • Zonal momentum balance As was discussed in the heat balance section, perturbing any one part of the zonal momentum balance (e.g. through oscillations) results in changes in the other parts of the balanced circulation

9. Synoptic I – ATMS 410 • Purpose • This lecture packet is an examination of how observations of global large-scale (long time scale) oscillations can aid our forecasts in the mid-latitudes http://www.mmm.ucar.edu/asr2003/deepconv.html#mjo

10. Synoptic I – ATMS 410 • Definition; teleconnections • Linkages between climate anomalies at some distance from each other • The tendency for atmospheric circulation patterns to be related, either directly or indirectly, over large and spatially non-contiguous areas http://www.isse.ucar.edu/sadc/chptr2.html

11. Synoptic I – ATMS 410 • Examples of atmospheric oscillation teleconnections • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) • North Pacific Oscillation (NPO)/ Pacific Decadal Oscillation (PDO) • Madden-Julian Oscillation (MJO) • Quasi-biennial Oscillation (QBO) • Pacific North American Oscillation (PNA) • Southern Oscillation (SO)

12. Synoptic I – ATMS 410 • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) teleconnections • Positive phase • frequent strong winter storms track in a more northerly path across the North Atlantic Ocean • warm, wet winters in W. Europe since the air from subtropical highs will prevail http://www.gomoos.org/nao/page5.html

13. Synoptic I – ATMS 410 • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) teleconnections • Positive phase* (cont.) • eastern U.S. experiences mild and wet winters *stronger than usual subtropical high pressure and a deeper than normal Icelandic Low http://www.gomoos.org/nao/page5.html

14. Synoptic I – ATMS 410 • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) teleconnections • Negative phase • more cold air invasions are experienced in North America, Western Europe and the Mediterranean http://www.gomoos.org/nao/page5.html

15. Synoptic I – ATMS 410 • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) teleconnections • Good correlation between NAO index and Moroccan rainfall • high Moroccan rainfall tends to coincide with negative phase NAO • low Moroccan rainfall tends to coincide with positive phase NAO negative phase http://www.ifremer.fr/lpo/thuck/nao/nao5.html

16. Synoptic I – ATMS 410 10-30oW • North Atlantic Oscillation (NAO), Arctic Oscillation (AO) teleconnections • Number of January low pressure systems that cross the North Atlantic to the west of Morocco and southwestern Europe are greater during the negative phase (solid line)

17. Synoptic I – ATMS 410 • North Pacific Oscillation (NPO)/ Pacific Decadal Oscillation (PDO) teleconnections • Negative (cool) phase • long-term droughts in the American Southwest • enhanced coastal ocean biological productivity off the west coast of the contiguous United States and inhibited productivity in Alaska (warm phase in figure) http://www.atmos.washington.edu/~mantua/REPORTS/PDO/PDO_egec.htm

18. Synoptic I – ATMS 410 Source: http://www.atmos.washington.edu/~mantua/REPORTS/PDO/PDO_egec.htm • NPO/ PDO teleconnections

19. Synoptic I – ATMS 410 • MJO teleconnections Appears to be a coherent simultaneous relationship between the longitudinal position of maximum MJO-related rainfall and the location of extreme west coast precipitation events http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

20. Synoptic I – ATMS 410 • MJO teleconnections west coast location                           longitude of maximum MJO-related rainfall western Washington:                                           120°E northwestern Oregon                                           125°E southwestern Oregon                                           130°E northwestern California                                         140°E north central California                                         150°E west central California                                          160°E southwestern California                                        165°E southern California                                              170°E link weakens It should be noted that there is case-to-case variability in the amplitude and longitudinal extent of the MJO-related precipitation, so this should be viewed as a general relationship only. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

21. Synoptic I – ATMS 410 • MJO teleconnections (1) 7-10 days prior to the heavy precipitation event: Heavy tropical rainfall associated with the MJO shifts eastward from the eastern Indian Ocean to the western tropical Pacific. A moisture plume extends northeastward from the western tropical Pacific towards the general vicinity of the Hawaiian Islands. A strong blocking anticyclone is located in the Gulf of Alaska with a strong polar jet stream around its northern flank. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

22. Synoptic I – ATMS 410 • MJO teleconnections (2) 3-5 days prior to the heavy precipitation event: Heavy tropical rainfall shifts eastward towards the date line and begins to diminish. The associated moisture plume extends further to the northeast, often traversing the Hawaiian Islands. The strong blocking high weakens and shifts westward. A split in the North Pacific jet stream develops, characterized by an increase in the amplitude and areal extent of the upper tropospheric westerly zonal winds on the southern flank of the block and a decrease on its northern flank. The tropical and extratropical circulation patterns begin to "phase", allowing a developing midlatitude trough to tap the moisture plume extending from the deep tropics. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

23. Synoptic I – ATMS 410 • MJO teleconnections (3) The heavy precipitation event As the pattern of enhanced tropical rainfall continues to shift further to the east and weaken, the deep tropical moisture plume extends from the subtropical central Pacific into the midlatitude trough now located off the west coast of North America. The jet stream at upper levels extends across the North Pacific with the mean jet position entering North America in the northwestern United States. Deep low pressure located near the Pacific Northwest coast can bring up to several days of heavy rain and possible flooding. These events are often referred to as "pineapple express" events, so named because a significant amount of the deep tropical moisture traverses the Hawaiian Islands on its way towards western North America. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

24. Synoptic I – ATMS 410 • MJO teleconnections • Related topic; atmospheric rivers another source of the “pineapple express”

25. Synoptic I – ATMS 410 • MJO teleconnections • atmospheric rivers (Ralph et al. 2004), warm ENSO winter (97, 98)

26. Synoptic I – ATMS 410 • MJO teleconnections • atmospheric rivers FIG. 14. Composite analyses based on the NCEP–NCAR daily reanalysis global gridded dataset for the 46 days with baselines shown in Fig. 13: (a) SLP (mb), (b) 925-mb temperature (T; 8C), (c) 925-mb specific humidity (q; g kg21), (d) 700-mb specific humidity (q; g kg21), (e) 500-mb geopotential height (Z; m), and (f ) 300-mb isotachs (m s21) and wind vectors. Frontal interpretations are based on the composite analyses. Standard frontal notation is used. The bold gray line transecting the cold front in each panel is the composite baseline shown in Fig. 13.

27. Synoptic I – ATMS 410 • MJO teleconnections • atmospheric rivers • significant poleward moisture flux occurs along very narrow zones (rivers) • four to five rivers (within the earth’s circumference at midlatitudes) accomplish 90% of the total instantaneous meridional water vapor transport

28. Synoptic I – ATMS 410 • MJO teleconnections • during the northern winter of 1984/85, positive thickness anomalies (ridging) occurred over the eastern U.S. when the convection associated with the MJO shifted from the Indian Ocean to Indonesia • opposite occurred when the convection approached the central Pacific Ocean Caution! Single season.

29. Synoptic I – ATMS 410 • MJO teleconnections Although tropical cyclones occur throughout the NH warm season (typically May-November) in both the Pacific and the Atlantic basins, in any given year there are periods of enhanced / suppressed activity within the season. There is evidence that the MJO modulates this activity (particularly for the strongest storms) by providing a large-scale environment that is favorable (unfavorable) for development. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

30. Synoptic I – ATMS 410 • MJO teleconnections Figure 2. Composite evolution of MJO events during the summer months together with points of origin of tropical cyclones that developed into hurricanes / typhoons (open circles). The green (brown) shading roughly corresponds to regions where convection is favored (suppressed) as represented by 200-hPa velocity potential anomalies. Composites are based on 21 events over a 35 day period. Hurricane track data is for the period JAS 1979-1997. Points of origin in each panel are for different storms. Contour interval is 0.5x106 m2 s-1, negative contours are dashed, and the zero contour is omitted for clarity.

31. Synoptic I – ATMS 410 • MJO teleconnections The strongest tropical cyclones tend to develop when the MJO favors enhanced precipitation. As the MJO progresses eastward, the favored region for tropical cyclone activity also shifts eastward from the western Pacific to the eastern Pacific and finally to the Atlantic basin. While this relationship appears robust, we caution that the MJO is one of many factors that contribute to the development of tropical cyclones. For example, it is well known that SSTs must be sufficiently warm and vertical wind shear must be sufficiently weak for tropical disturbances to form and persist. http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

32. Synoptic I – ATMS 410 • MJO teleconnections • In other words… • if an easterly wave meets the cloudy sky phase of the MJO, the conditions for hurricane formation improve • note that the easterly wave and the MJO are moving in opposite directions http://www.cpc.ncep.noaa.gov/products/intraseasonal/intraseasonal_faq.html

33. Synoptic I – ATMS 410 • MJO and ENSO… Intraseasonal oscillations often exhibit a strong relationship to the phase of the ENSO cycle. Overall, there tends to be weak or absent MJO activity during moderate or strong El Niño episodes. In contrast, MJO activity is often substantial during ENSO-neutral years and during weak La Niña episodes. http://www.icess.ucsb.edu/esrg/el_nino_events/start.html

34. Synoptic I – ATMS 410 • Quasi-biennial Oscillation (QBO) teleconnections • Plays a role in • stratospheric ozone mixing • hurricane formation • NH winters • modulating timing of ENSO

35. Synoptic I – ATMS 410 • Quasi-biennial Oscillation (QBO) teleconnections • Plays a role in • stratospheric ozone mixing • hurricane formation • NH winters • modulating timing of ENSO http://www.kurasc.kyoto-u.ac.jp/~epic/dynamics.html

36. Synoptic I – ATMS 410 • QBO teleconnections • stratospheric ozone mixing • QBO modulates Mean Meridional Circulations (MMCs), transport of chemical species in/out of stratosphere by • large-scale circulations • mixing processes (eddies)

37. Synoptic I – ATMS 410 • QBO teleconnections • hurricane formation • Atlantic basin; more activity during the QBO west phase • SW Indian basin; more activity in the QBO east phase 30 hPa stratospheric wind direction and the seasonal number of hurricane days (1949 to 1982)

38. Synoptic I – ATMS 410 • QBO teleconnections • hurricane formation, impacts a result of • Change in sea level pressure and corresponding change in vertical wind shear • Shift and change in intensity of ITCZ

39. Synoptic I – ATMS 410 • QBO teleconnections • In both hemispheres, atmospheric conditions associated with smoothly changing seasonal characteristics are modified by the effects of planetary Rossby waves, forced in part by • land-sea contrasts • surface topography • which propagate vertically and horizontally into the winter stratosphere

40. Synoptic I – ATMS 410 • QBO teleconnections • Because the NH has much greater • land-sea contrasts • surface topography • the NH planetary waves tend to have larger amplitudes. • Hence, NH winter stratosphere tends to be more disturbed by planetary waves than SH winter stratosphere.

41. Synoptic I – ATMS 410 • QBO teleconnections • NH winters • Features above 10 hPa are a result of modulation by the QBO of cross-equatorial (summer to winter) branch of the MMC calculate separate averages of the January wind data for the two QBO phases and then take the difference of the averages

42. Synoptic I – ATMS 410 • QBO teleconnections • NH winters • NH dipole pattern; Arctic Oscillation excited by the QBO

43. Synoptic I – ATMS 410 • QBO teleconnections • NH winters • Extratropical QBO signal • begins during autumn in midlatitudes • reaches a high-latitude maximum during January modulates the strength of the northern winter polar vortex

44. Synoptic I – ATMS 410 • QBO teleconnections • SH springs • Extratropical QBO signal • is largest during the late spring (Nov) rather than in mid-winter (as in NH)

45. Synoptic I – ATMS 410 • Pacific North American Oscillation (PNA) teleconnections • planetary Rossby waves are key! Positive index* strong amplitude upper-level waves with a ridge along the west coast of North America (meridional flow) *strong Aleutian Low, strong ridge over western Canada http://www.cdc.noaa.gov/Teleconnections/pna.html

46. Synoptic I – ATMS 410 • PNA teleconnections Negative index zonal flow aloft along the west coast of North America Leathers et al. (1991)

47. Synoptic I – ATMS 410 • PNA teleconnections Winter temperature – PNA index correlations strong in southeast and northwest of U.S. Leathers et al. (1991)

48. Synoptic I – ATMS 410 • PNA teleconnections High winter precipitation – PNA index correlations less extensive in upper Mississippi valley and northern Rockies Leathers et al. (1991)

49. Synoptic I – ATMS 410 • PNA teleconnections • PNA positive winters • more Great Lakes cyclones originate from the northwest (v. from the west and southwest in PNA negative winters) • mean streamflow discharges of the Ohio River 100% lower compared to PNA negative winters http://www.beringclimate.noaa.gov/data/Images/Fig1PNA.htm

50. Synoptic I – ATMS 410 • Southern Oscillation (SO) teleconnections {a.k.a. ENSO} • Recall… • no two ENSO episodes are exactly alike http://www.isse.ucar.edu/sadc/chptr2.html