Climate Change and Extreme Precipitation


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Extreme weather is becoming more common in our region. Flood events can impact human health and safety, and result in substantial costs to property and infrastructure. Geared toward municipal decision makers and concerned citizens, this forum provides on-the-ground examples of flood resilience strategies that can help Hudson Valley communities minimize risks while conserving financial resources.

Presentation by Climatologist for the Northeast Regional Climate Center Jessica Rennells for a flood management forum hosted by the Cary Institute of Ecosystem Studies in Millbrook, NY on May 4, 2013.

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  • A non-random change in climate that is measured over several decades or longer. The change may be due to natural or human-induced causes. (nws)Global annual average temperature (as measured over both land and oceans; scale on left) has increased by more than 1.4°F (0.8°C) since 1880. (NOAA NCDC)
  • 1895-2012 = increase of 1 deg F (46.6 – 47.6) 1983-2012 = increase of 1.5 (46.9 – 48.4)Axis at 47.1, average of all yearsSecond trend line is 30 years (1983-2012)
  • Through 2012. warmed about 1.2 deg F (47.2 – 48.4)
  • 13 longest-record rural, unregulated rivers (I.e. do not have a dam on them) in New England (Hodgkins et al. 2003). provides a date when half of the volume of a river has passed a gauging station for a particular season. Center-of-volume flows have been getting earlier on all the rivers studied, indicating the snowpack is melting earlier. Note the significant change around 1970. Over last 30 years, 1-2 weeks earlierEffect on Spring flooding – when flow rates at their highest.Jan – May; chart Mar 11, Mar 21, Mar 31, Apr 10, Apr 20, Apr 30, May 10Annual peak stream flows have increased at gauges in the Northeast during the past 85 years (Hirsch and Ryberg 2012)
  • Annual mean sea level for gauges at four major Northeast coastal cities. Data from PSMSL (2012). 1856-2006Over past 1000 years regional rising of .34-.43” /decade. During 20th century rise of 1.2”/decade. Rate of change similar in recent decades Observed Sea Level Rise in NYC (at the Battery, NYC) 1.2’ over 100 years, exceeding the global ave of 8” (from NYC Panel on CC 2010)Warming water => increase ocean water volume (thermal expansion), melting of glaciers & ice sheets, changes in Atlantic Ocean Circulation, geological processes (land subsidence)Saltwater front moves further up the Hudson River (sea level rise), saltwater intrusion
  • Increase by almost 6” (39 – 44.9)Axis at 41.9 – average of all years
  • Through 2012. shows considerable year-to-year variability, overall increase. . This increase in precipitation is consistent with the warmer temperatures the region has experienced (warmenr temperatures - more evaporation - increased capacity of atmosphere to hold moisture - more precipitation.One of the most striking features in the drought in the first half of the 1960sIncrease of about 7.2” (38.8 – 46)
  • 1895-2011 (using CDDv2 data set) Summer doesn’t exhibit the trend, but some very wet summers in past 10 years (2006, 2009). Fall is statistically significant: +0.24”/decade
  • a 2-day 5-year storm event for contiguous US (1901-2011) compared to 1901-1960 period. (Figure source: adapted from (Kunkel et al. 2012)
  • Very Heavy events (heaviest 1% of daily events from 1901-2011) compared to 1901-1960 average (Figure source: NOAA NCDC/CICS-NC)
  • Increase of about 2 days
  • Iren on 8/28/2011 (NASA Satellite Image)
  • 72-h precipitation (inches, shaded every 2 in) ending at 1200 UTC 29 Aug 2011. From the Northeast Regional Climate Center (NRCC) high-resolution gridded dataset.
  • Based on precip amounts only. From precip.netSlide Mtn: 8.62” = 200 yr storm event (8.03”) (Ulster County)Rosendale: 8.52” = 100 yr storm event (7.37”) (Ulster County)Mohonk Lake: 8.21” = 100yr storm event (7.36”) (Ulster County)Walden: 6.65” = 50yr storm event (6.13”) (Orange County)Poughkeepsie: 5.95” = 25yr storm event (5.16”) (Dutchess County)
  • 100-year storm(ClimAID) HadCM3 model, consistent w/ other 15 gcm’sNYS stations
  • 1-day 20-year event for 2081-2100 compared to 1981-2000. Left: emissions reduction scenario (1-2x more), Right: continued increases in emissions (3-4x more)
  • This method is one of the most straightforward and popular procedures for climate risk assessment, provided that the prerequisite climate model outputs are available. Change factors are typically calculated for calendar months by comparing the present and projected climatology in GCM for grid boxes overlying the target region.Change factors for temperature are calculated by subtracting the model averages representing baseline (1961–1990) from the future (e.g. 2020s, 2050s or 2080s) temperatures. Change factors for precipitation arenormally derived from the ratio of the projected-to-baseline averages, but absolute differences can also be applied. The temperature changes are then added to observations (or in the case of P multiplied by observations) to yield a climate series at the study location.Pros:Easy to apply; Can handle probabilistic climate model outputCons:1. Perturbs only baseline mean and variance
  • 90 days- Days per year reaching 90 or hotter (low & high scenarios)- Heat waves increasing in frequency, duration, intensity- Overnight temps too Heat Index- Averages summer heat index under high & low scenarios (temp & RH)- higher RH b/c warmer atmosphere can hold more moisture
  • Droughtincreased in late summer/fall b/c warmer temps = higher evap rates, earlier spring snow meltextreme rain – too much of a good thing – ground can’t absorb/runoff/flooding - Short term droughts (lasting 1-3 months) could occur once per year, under higher-emissions scenario
  • Snow MapHistoric vs late century : dusting of snow for at least 30 daysNortheast projected to lose 4-8 days / 10-15 days snow cover per monthMore precip falling as rain
  • Global sea level rise of 1-4’ by 21004” more than global ave in Northeast (b/c land subsidence)
  • Cat 4&5 Hurricanes are expected to increase 75% from the 2001-2020 period to the 2081-2100 period.
  • measure of overall hurricane intensity; upward trend in strength of hurricanes and the # of strong hurricanes (Cat 4&5)­­ from 1983-2009 (Kossin et al. 2007)There has been an increase in the overall strength of hurricanes and in the number of strong (Category 4 and 5) hurricanes in the North Atlantic since the early 1980s. The intensity of the strongest hurricanes is projected to continue to increase as theoceans continue to warm.
  • Climate Change and Extreme Precipitation

    1. 1. Climate Change&Extreme PrecipitationJessica RennellsNOAA, Northeast Regional Climate Center at CornellUniversity
    2. 2. What is Climate Change?The Earth is warming because ofincreased greenhouse gases.
    3. 3. Global Average Annual Temperature Anomaly (oF)From meteorological stations 1880-2005Hansen et al. (2001) J. Geophysical Res. Vol 106, p. 23,947-23,963Data from 1900 1920 1940 1960 1980 2000TemperatureAnomoly(oF)Year
    4. 4. 1995-2004 vs. 1940-1980-3.6 -1.8-2.7 -0.9
    5. 5. 4344454647484950511895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005AverageAnnualTemperature°FYearColdest year onrecord - 1917Hottest year onrecord - 2012Average Annual Temperature in Northeast1895 - 2012
    6. 6. Hudson Valley Climate DivisionAverage Annual Temperature1895-201244454647484950511895189819011904190719101913191619191922192519281931193419371940194319461949195219551958196119641967197019731976197919821985198819911994199720002003200620092012Temperature°FYear
    7. 7. Spatial Variation of Days with Snow on Ground 1970-2000
    8. 8. Winter/Spring Center of Volume Dates
    9. 9. Sea level rise
    10. 10. 30343842465054581895189819011904190719101913191619191922192519281931193419371940194319461949195219551958196119641967197019731976197919821985198819911994199720002003200620092012AnnualPrecipitation(inches)YearAverage Annual Precipitation in the Northeast1895-2012
    11. 11. Hudson Valley Climate DivisionAverage Annual Precipitation1895-20122530354045505560189518991903190719111915191919231927193119351939194319471951195519591963196719711975197919831987199119951999200320072011Precipitation(inches)Year
    12. 12. Winter SpringSummer FallPrecipitation Trends
    13. 13. 2-Day 5-Year Event
    14. 14. 1-Day Very HeavyPrecipitation
    15. 15. Observed Trends in 1-day Very Heavy Precipitation(1958 to 2010)NOAA/NCDC
    16. 16. Percent Change in 1-day Annual Maximum ObsAtmospheric Water VaporNOAA/NCDC
    17. 17. West Point, NY# of days with 2” or more Precipitation
    18. 18. 72-h Precipitation (in) Ending at 8 AM 29 Aug 2011Rainfall Associated with TC Irene
    19. 19. 1-Day storm events on 8/28/2011Slide Mtn: 8.62” = 200 yr storm event (8.03”) Rosendale:8.52” = 100 yr storm event (7.37”) Mohonk Lake: 8.21” =100yr storm event (7.36”)Walden: 6.65” = 50yr storm event (6.13”)
    20. 20. Projected Rainfall & Frequencyof 100-year storm
    21. 21. 1-Day 20-Year Event
    22. 22. Climate Model Ensembles67%
    23. 23. AverageSummerHeat Index # Days Over 90 
    24. 24. Seasonality
    25. 25. Area with Snow Cover for at least 30 daysUnder high emissions scenario
    26. 26. Source: CCSRNYCTroyNew York City Baseline(1971-2000)2020s 2050s 2080sSea level rise(central range)NA + 2 to 5 in + 7 to 12 in + 12 to 23 inRapid Ice-MeltSea level riseNA ~ 5 to 10 in ~ 19 to 29 in ~ 41 to 55 inTroy Baseline(1971-2000)2020s 2050s 2080sSea level rise(Central range)NA + 1 to 4 in + 5 to 9 in + 8 to 18 inRapid Ice-MeltSea level riseNA ~ 4 to 9 in ~ 17 to 26 in ~ 37 to 50 inSea level rise
    27. 27. Figure 5.6. Hudson River Estuary withlocation of salt front on10/30/2009, approximate distance is 53 rivermiles from the Battery at New York City(USGS).•Rising sea level•slope of the river 2 ft/150mi•sea level rise 1 in/decade•0.6 mi up river/ year•Reduced precip•Increased temp (more evap)Salt FrontMigration
    28. 28. Flood-Producing Extreme Precipitation- Frontal systems- Thunderstorms- Coastal storms- Nor’easters- Tropical stormsOther Factors – How will Climate Change affect these?- Rain-on-snow events- Geography- Antecedent soil conditions- Snowmelt- Ice Jams- Rain-on-snow events- Antecedent soil conditions- Geography- Infrastructure- Impervious surfaces
    29. 29. Questions?
    30. 30. Time-series represents an areally weighted average of data from 56 stations in theNortheast that have been in operation continuously since 1900.Data from the NOAA-NCDC ( Annual Temperature in the Northeast 1899-2000Until 2012: 50.2
    31. 31. Average Annual Precipitation in the Northeast, 1899-2000Time series represent average of 79 meteorological stations in the Northeast.