observing networks, precipitation and extreme precipitation

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

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  • Observing Networks, Precipitation and Extreme Precipitation

    Paul H. WhitfieldMeteorological Service of CanadaDepartment of Earth Sciences, Simon Fraser University

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    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?BackgroundMultiple site precipitationMultiple site extremesPineapple Express

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

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    Multi-site PrecipitationPrecipitation 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)

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    Algorithms

    Let PX and PY be daily precipitation amounts at X and Y =PX / PY (1) For a suitable > 1, -1 is regarded as regional Otherwise as local

    Or = max(PX, PY) / (PX + PY) (2) For a suitable > 0.5, > is regarded as local is regarded as regional

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    AlgorithmsFor 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 > 0.5, > is regarded as local is regarded as regional

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    ApplicationsThe Dongting Lake Basin Subtropical monsoonal climate, wet in summer.

    The BC Inner South Coast Mid-latitude coastal climate, wet in winter.

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    DataDaily precipitation data from the 10 climate stations (1979 2008)NCEP/DOE AMIP-II Reanalysis datasets (2.5x2.5 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)

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    Multi-Location Scheme

    ( 0.5 1 )

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    All year round DLB-HPCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression lines

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    Wet Season DLB-HPCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression lines

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    Dry Season DLB-HPCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75

    Regional events Local events Regression lines

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatology1333 Local318 Regional

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatology777 Local331 Regional

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    (Multi-Location scheme) (with = 0.75)

    Climatological mean

    850-hPa moisture flux & divergence

    Composite local events:

    Composite regional events:

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    All year round ISC-BCCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression lines

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    Wet Season ISC-BCCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression lines

    Page * *

    Dry Season ISC-BCCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75

    Regional events Local events Regression lines

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatology1620 Local577 Regional

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatology1128 Local90 Regional

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    (Multi-Location scheme) (with = 0.75)

    Climatological mean

    850-hPa moisture flux & divergence

    Composite local events:

    Composite regional events:

    Pineapple Express?

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    Extremes

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    Multi-Location Scheme

    ( 0.5 1 )At least one station p>25mm

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    All year round DLB-HPCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression linesAt least one station p>25mm

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatologyAt least one station p>25mm331 Local182 Regional

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatologyAt least one station p>25mm27 Local45 Regional

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    All year round ISC-BCCross plots of daily precipitation between two of five selected climate stations in using a log-log scale.

    Based on Eq. (2) with = 0.75 Regional events Local events Regression linesAt least one station p>25mm

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatologyAt least one station p>25mm218 Local183 Regional

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    (Multi-Location scheme with = 0.75) Composites and anomalies from climatologyAt least one station p>25mm55 Local11 Regional

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    Pineapple Express

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    Pineapple Express

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    Pineapple Expressa 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.

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    November 2006 flood, Granite Falls on the Stillaguamish River

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    Lake Bad Water Death Valley Winter 2005

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    Pineapple Express

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    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.

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    Average of deviation, on the 100 days with the most intense pineapple-express circulations of surface-air temperatures (top) and precipitation rates (bottom) from long-term mean. Graphics courtesy of the NOAA/Climate Diagnostics Center.

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    Relations (a) between the NINO3.4 sea-surface temperature (SST) index of the El Nio-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 Nios and (b) El Nio-like PDO years; blue dots indicate (a) La Nias and (b) La Nia-like PDO years; green dots are neutral years. Lines are regression fits.

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

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    Dettinger 2004

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    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 CanadaEffect 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?

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    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 CanadaEffect 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

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