Observing Networks, Precipitation and Extreme Precipitation

1. Observing Networks, Precipitation and Extreme Precipitation Paul H. Whitfield Meteorological Service of Canada Department of Earth Sciences, Simon Fraser University

2. Can we learn more about extremes [and climatology in general] from networks of stations rather than single stations?What do we learn when the 100 year event happens at one location? • Background • Multiple site precipitation • Multiple site extremes • Pineapple Express

3. A scheme for precipitation measures at two locations (Toews et al. 2009)

6. Multi-site Precipitation Precipitation has many types (drizzle, hail, virga, graupel). For some meteorological & climatological applications, it can be classified into: Convective vs. stratiform (Based on mechanisms of genesis) And for some other applications (e.g., Hydrology): Local vs. regional: (Based on distribution and impact)

7. Algorithms Let PX and PY be daily precipitation amounts at X and Y η =PX / PY (1) For a suitable η > 1, η≥η≥η-1 is regarded as regional Otherwise as local Or λ = max(PX, PY) / (PX + PY)(2) For a suitable λ > 0.5, λ > λ is regarded as local λ ≤ λ is regarded as regional

8. Algorithms • For precipitation measures at multiple (M) locations, (3) where M is number of locations with precipitation (M ≥ 2), MH ≤ M / 2, And P represents the precipitation amount,P1≥ P2 ≥ ··· ≥PM , For a suitable Λ > 0.5, Λ > Λis regarded as local Λ ≤ Λis regarded as regional

9. Applications • The Dongting Lake Basin Subtropical monsoonal climate, wet in summer. • The BC Inner South Coast Mid-latitude coastal climate, wet in winter.

10. Data • Daily precipitation data from the 10 climate stations (1979 – 2008) • NCEP/DOE AMIP-II Reanalysis datasets (2.5°x2.5° grid, every 6 hrs) Wet season: 9 Apr – 8 Jul (DLB-HP) and 1 Nov – 30 Jan (ISC-BC) Dry season: 15 Nov – 13 Feb (DLB-HP) 19 Jun – 17 Sep (ISC-BC)

11. Multi-Location Scheme ( 0.5 ≤ Λ≤ 1 )

12. All year round DLB-HP Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

13. Wet Season DLB-HP Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

14. Dry Season DLB-HP Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

15. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology 1333 Local 318 Regional

16. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology 777 Local 331 Regional

17. (Multi-Location scheme) (with Λ = 0.75) Climatological mean 850-hPamoisture flux & divergence Composite local events: Composite regional events:

18. All year round ISC-BC Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

19. Wet Season ISC-BC Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

20. Dry Season ISC-BC Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

21. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology 1620 Local 577 Regional

22. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology 1128 Local 90 Regional

23. (Multi-Location scheme) (with Λ = 0.75) Climatological mean 850-hPamoisture flux & divergence Composite local events: Composite regional events: Pineapple Express?

24. Extremes

25. At least one station p>25mm Multi-Location Scheme ( 0.5 ≤ Λ≤ 1 )

26. At least one station p>25mm All year round DLB-HP Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

27. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology At least one station p>25mm 331 Local 182 Regional

28. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology At least one station p>25mm 27 Local 45 Regional

29. At least one station p>25mm All year round ISC-BC Cross plots of daily precipitation between two of five selected climate stations in using a log-log scale. Based on Eq. (2) with λ = 0.75 • Regional events • Local events Regression lines

30. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology At least one station p>25mm 218 Local 183 Regional

31. (Multi-Location scheme with Λ = 0.75) Composites and anomalies from climatology At least one station p>25mm 55 Local 11 Regional

32. Pineapple Express

33. Pineapple Express

34. Pineapple Express a weather condition made of a jet stream of wet, warm air that reaches western North America from the Pacific Ocean, usually by way of Hawaii, and causes heavy rainfall.

35. November 2006 flood, Granite Falls on the Stillaguamish River

36. Lake Bad Water – Death Valley Winter 2005

37. Pineapple Express

39. Mean seasonal cycles of the timing of pineapple-express circulations (bars) and the latitude of the jet stream core (maximum wind speeds at 250 hectopascals (hPa) pressure levels) north of Hawaii (curve); notice that the timing histogram has been reversed for comparison to the latitude curve.

40. Relations (a) between the NINO3.4 sea-surface temperature (SST) index of the El Niño-Southern Oscillation and the sum of water-vapor transports (Table 1) by pineapple-express circulations, and (b) between the Pacific Decadal Oscillation (PDO) index and the circulations. Red dots indicate (a) El Niños and (b) El Niño-like PDO years; blue dots indicate (a) La Niñas and (b) La Niña-like PDO years; green dots are neutral years. Lines are regression fits.

41. Exceedance probabilities for day-to-day changes in December–February discharges in the Merced River at Happy Isles, Yosemite National Park, under various circulation and precipitation conditions.

42. Dettinger 2004

43. Climate/weather questions: • Does the distance from the jet stream affect the intensity? During events stations outside the ‘front’ should have less precipitation than those along the band. Using real observations can we detect if this is true? This needs a new way to structure data. • Determine relative frequency of events in observations across a sample space of the climate network with some augmentation for the first 100 km south of Canada • Effect of the Pineapple Express should both decrease with distance from the coast and have some significant effects in some regions of the interior. Is this more prevalent in some locations? • Does the angle of transit affect intensity of precipitation [i.e. does it explain Tropical Punch?] • Can we understand better the connection to ENSO and PDO to occurrence? • Will these events change in a warmer climate – is there a way to tease out any part of the pineapple express variability to warmer/cooler periods/years?

44. Flood/streamflow questions: • Does the distance from the jet stream affect the intensity? During events stations outside the ‘front’ should have less precipitation than those along the band. Using real observations can we detect if this is true? This needs a new way to structure data. • Determine relative frequency of events in observations across a sample space of the climate network with some augmentation for the first 100 km south of Canada • Effect of the Pineapple Express should both decrease with distance from the coast and have some significant effects in some regions of the interior. Is this more prevalent in some locations? • Does the angle of transit affect intensity of precipitation [i.e. does it explain Tropical Punch?] • Can we understand better the connection to ENSO and PDO to occurrence? • Will these events change in a warmer climate – is there a way to tease out any part of the pineapple express variability to warmer/cooler periods/years?

45. Discussion questions: • Will climate change shift the landing of Pineapple Express northward? • Can information from multiple sites be useful in validating models? • Can we apply EVT to multiple stations? • How to deal with processes that are important at local scale and not resolved in GCM?