1. Dan Zarrow Northeast Regional Climate Center Fall 2010
Extreme Precipitation in New York & New England Background / Methodology
Dan Zarrow
Northeast Regional Climate Center
Fall 2010

2. Project Background

3. History of Extreme Precipitation
Technical Paper 40 (1961)
Wilks (1993)
NOAA Atlas 14 (2004)
NRCC (2010)

4. Project Goals
Create an updated, comprehensive extreme precipitation atlas for the Northeast US.
Match the products and output of NOAA Atlas 14 for NRCS compatability.
Add additional products to supplement NRCS hydrologic design.
Produce real-time monitoring and climate change tools.

5. Scope of Data/Output N-minute Hourly Daily 5min 1hr 1day 10min 2hr
Years
1yr
2yr
5yr
10yr
25yr
50yr
100yr
200yr
500yr
States
Connecticut
Maine
Massachusetts
New Hampshire
New York
Rhode Island
Vermont
(surrounding states)
(Canada)

6. Extreme Precip 101

7. It’s all about probability…
100-yr Storm
1 / 100 = 1% chance of occurrence in any year
25-yr Storm
1 / 25 = 4% chance of occurrence in any year
1-yr Storm
1 / 1 = 100% chance of occurrence???

8. The Process
It rains! Data Collection & Quality Control Distribution Filtering Gridding Smoothing Output

9. Partial Duration Series
Burlington International Airport (#431081) – (68 complete years)
3.99"
2.42"
2.21"
1.99"
1.85"
1.75"
1.69"
3.62"
2.38"
1.98"
1.83"
1.74"
1.68"
3.59"
2.36"
2.14"
1.96"
3.11"
2.13"
1.94"
1.79"
2.69"
2.32"
2.11"
1.78"
2.60"
2.31"
2.09"
1.92"
2.58"
1.77"
1.73"
2.54"
2.28"
2.05"
1.91"
1.72"
2.48"
2.27"
2.04"
1.9"
1.76"
1.71"
2.46"
2.26"
2.03"
2.24"
2.01"
1.87"

10. Fitting the Distribution
25yr Storm
3.37”
100yr Storm
4.54”

11. Partial Duration Series
Concord Municipal Airport (#271683) – (86 complete years)
5.95"
3.30"
2.74"
2.49"
2.42"
2.25"
2.16"
2.04"
5.12"
2.73"
2.48"
2.40"
2.24"
4.37"
3.27"
2.11"
4.12"
3.25"
2.69"
2.47"
2.10"
3.99"
3.22"
2.67"
2.46"
2.23"
2.02"
3.92"
3.02"
2.65"
2.44"
2.09"
2.98"
2.57"
2.43"
2.37"
2.22"
3.84"
2.56"
2.35"
2.21"
2.07"
2.01"
3.71"
2.91"
2.54"
2.34"
2.19"
2.06"
2.00"
3.56"
2.89"
2.51"
2.33"
3.53"
2.79"
2.50"
2.27"
2.18"

12. Fitting the Distribution
25yr Storm
4.60”
100yr Storm
6.45”

13. Partial Duration Series
Bangor International Airport (#170355) – (51 complete years)
5.98"
3.23"
2.68"
2.35"
2.17"
5.10"
3.09"
2.66"
2.32"
2.16"
4.68"
3.04"
4.40"
3.03"
2.31"
2.15"
4.08"
2.93"
2.52"
2.28"
2.14"
3.98"
2.89"
2.50"
2.24"
2.12"
3.67"
2.81"
2.49"
2.22"
2.11"
3.55"
2.74"
2.21"
3.53"
2.72"
2.41"
2.20"
3.51"
2.38"
2.18"
3.31"
2.36"

14. Fitting the Distribution
25yr Storm
4.46”
100yr Storm
6.21”

15. Partial Duration Series
Hartford Bradley International Airport (#063456) – (59 complete years)
7.70"
4.04"
3.15"
2.90"
2.72"
2.48"
6.27"
3.75"
3.12"
2.70"
2.47"
5.88"
3.68"
3.07"
2.89"
2.67"
5.72"
3.33"
3.06"
2.85"
2.60"
2.46"
5.26"
3.32"
2.99"
2.56"
5.22"
3.31"
2.98"
2.84"
5.10"
3.30"
2.55"
4.81"
3.25"
2.96"
2.78"
2.53"
4.41"
3.22"
2.76"
2.52"
4.31"
3.21"
2.94"
2.73"
2.51"
4.05"
3.19"
2.92"

16. Fitting the Distribution
25yr Storm
5.93”
100yr Storm
8.68”

17. Partial Duration Series
Providence TF Green Airport (#376698) – (76 complete years)
6.31"
4.23"
3.38"
3.08"
2.87"
2.76"
2.62"
6.17"
3.95"
3.37"
3.06"
2.86"
2.74"
2.60"
5.43"
3.73"
3.31"
3.04"
2.73"
5.39"
3.62"
3.29"
3.02"
2.85"
5.15"
3.57"
3.28"
2.72"
2.59"
4.78"
3.52"
2.97"
2.82"
2.70"
2.57"
4.75"
3.47"
3.23"
2.92"
2.81"
2.66"
4.71"
3.46"
3.18"
2.91"
2.80"
4.38"
3.15"
2.90"
2.78"
2.64"
2.56"
4.37"
3.42"
3.14"
2.54"
4.30"
3.40"
3.12"
2.77"
2.63"

18. Fitting the Distribution
25yr Storm
5.36”
100yr Storm
7.40”

19. Partial Duration Series
Boston Logan Internation Airport (#190770) – (72 complete years)
7.06"
3.84"
3.11"
2.81"
2.64"
2.52"
2.42"
6.11"
3.77"
3.00"
2.80"
2.40"
5.69"
3.58"
2.98"
2.77"
2.63"
2.50"
5.63"
3.51"
2.95"
2.60"
4.88"
3.49"
2.94"
2.76"
2.59"
2.49"
2.39"
4.71"
3.36"
2.91"
2.38"
4.47"
3.34"
2.90"
2.71"
2.58"
2.47"
4.29"
3.32"
2.89"
2.67"
2.55"
2.46"
4.21"
3.31"
2.66"
2.54"
4.12"
3.16"
2.87"
4.00"
3.15"
2.82"
2.53"

20. Fitting the Distribution
25yr Storm
5.13”
100yr Storm
7.15”

21. Data

22. Period of Record
From start of record to end of 2008 Must have 20 complete years of data <25% of data record missing

23. Analysis of Daily Data
Used NRCC database to obtain data for 2,070 NOAA Cooperative Network stations in the Northeast.
Ran distribution for durations of 1day, 2day, 4day, 7day, and 10day.

24. Analysis of Hourly Data
Obtained historical precipitation data from NCDC hourly dataset for 603 stations in the Northeast.
Ran distribution for durations of 1hr, 2hr, 3hr, 6hr, 12hr, 24hr, and 48hr.
Calculated 24hr/1day ratio of 1.13, using data from initial Daily analysis. *Same as Atlas14

25. Analysis of Sub-Hourly Data
Used 5-minute data for 30 stations in the Northeast to run distribution for 5min, 10min, 15min, 30min, 60min, and 120min durations.
Calculated 60min/1hr ratio of 1.16, using data from Hourly analysis. *Same as Atlas14
Calculated Nmin/60min ratios based on sub- hourly results.

26. Analysis of Sub-Hourly Data

27. Injection of Canadian Data
Used NCDC dataset with 649 daily stations in eastern Canada.
Ran Beta-P distribution for durations of 1day, 2day, 4day, 7day, and 10day.
Used average ratios throughout Northeast US study region to estimate hourly and subhourly return periods.

28. Quality Control

29. NRCC QC Process
Data is pre-screened by NOAA and climate center staff each month, and flagged if suspect, erroneous, or an accumulated value.
Unusually high daily data values are checked against nearby stations. If a daily rainfall value exceeds 10”, at least two nearby stations (within 200 miles) must also have reported amounts of at least 5”. If a daily rainfall value exceeds 5”, at least two nearby stations must also have reported amounts of at least 3”.
Hourly precipitation data are checked against corresponding daily data. For each hour's data, at least one nearby station must have recorded a higher daily total rainfall amount.
After the distribution is run for the entire Northeast, stations outside more than 2 standard deviations than the mean of all stations are removed.

30. NRCC QC Process AUTOMATIC
Data is pre-screened by NOAA and climate center staff each month, and flagged if suspect, erroneous, or an accumulated value.
Unusually high daily data values are checked against nearby stations. If a daily rainfall value exceeds 10”, at least two nearby stations (within 200 miles) must also have reported amounts of at least 5”. If a daily rainfall value exceeds 5”, at least two nearby stations must also have reported amounts of at least 3”.
Hourly precipitation data are checked against corresponding daily data. For each hour's data, at least one nearby station must have recorded a higher daily total rainfall amount.
After the distribution is run for the entire Northeast, stations outside more than 2 standard deviations than the mean of all stations are removed.

31. Distribution

32. PDS vs. AMS
Partial Duration Series (PDS) for n years in a station’s record, use the n highest independent rainfall amounts. Annual Maximum Series (AMS) use the highest rainfall amount for each year in a station’s record that has sufficient data.

33. Partial Duration Series
Burlington International Airport (#431081) – (68 complete years)
3.99"
2.42"
2.21"
1.99"
1.85"
1.75"
1.69"
3.62"
2.38"
1.98"
1.83"
1.74"
1.68"
3.59"
2.36"
2.14"
1.96"
3.11"
2.13"
1.94"
1.79"
2.69"
2.32"
2.11"
1.78"
2.60"
2.31"
2.09"
1.92"
2.58"
1.77"
1.73"
2.54"
2.28"
2.05"
1.91"
1.72"
2.48"
2.27"
2.04"
1.9"
1.76"
1.71"
2.46"
2.26"
2.03"
2.24"
2.01"
1.87"

34. Burlington International Airport (#431081) – 1940-2008 (68 years)
Annual Maximum Series
Burlington International Airport (#431081) – (68 years)
3.99"
2.36"
2.05"
1.83"
1.63"
1.46"
1.26"
3.62"
2.04"
1.79"
1.44"
0.86"
3.59"
2.32"
2.03"
1.77"
1.62"
1.42"
3.11"
2.31"
2.01"
1.41"
2.69"
1.99"
1.75"
1.61"
2.60"
2.28"
1.98"
1.60"
1.40"
2.58"
2.27"
1.94"
1.74"
1.57"
1.38"
2.48"
2.21"
1.92"
1.51"
1.36"
2.46"
1.35"
2.42"
2.13"
1.91"
1.71"
1.32"
2.38"
2.09"
1.87"
1.65"
1.47"
1.27"

35. Partial Duration Series
Concord Municipal Airport (#271683) – (86 complete years)
5.95"
3.30"
2.74"
2.49"
2.42"
2.25"
2.16"
2.04"
5.12"
2.73"
2.48"
2.40"
2.24"
4.37"
3.27"
2.11"
4.12"
3.25"
2.69"
2.47"
2.10"
3.99"
3.22"
2.67"
2.46"
2.23"
2.02"
3.92"
3.02"
2.65"
2.44"
2.09"
2.98"
2.57"
2.43"
2.37"
2.22"
3.84"
2.56"
2.35"
2.21"
2.07"
2.01"
3.71"
2.91"
2.54"
2.34"
2.19"
2.06"
2.00"
3.56"
2.89"
2.51"
2.33"
3.53"
2.79"
2.50"
2.27"
2.18"

36. Concord Municipal Airport (#271683) – 1921-2008 (87 years)
Annual Maximum Series
Concord Municipal Airport (#271683) – (87 years)
5.95"
3.30"
2.50"
2.40"
2.09"
1.97"
1.70"
1.44"
5.12"
2.48"
2.06"
1.94"
1.63"
4.37"
3.27"
2.47"
2.37"
2.04"
1.92"
1.43"
4.12"
3.25"
2.46"
2.33"
2.02"
1.90"
1.62"
3.99"
3.22"
2.44"
2.25"
1.87"
1.42"
3.92"
2.98"
2.43"
2.22"
1.86"
1.55"
1.39"
2.89"
2.42"
2.19"
2.01"
1.85"
1.54"
1.35"
3.84"
2.79"
2.18"
2.00"
1.82"
1.52"
1.31"
3.71"
2.73"
2.16"
1.99"
1.81"
1.50"
1.30"
3.56"
2.65"
1.98"
1.48"
1.29"
3.53"
2.56"
1.80"
1.45"

37. Partial Duration Series
Bangor International Airport (#170355) – (51 complete years)
5.98"
3.23"
2.68"
2.35"
2.17"
5.10"
3.09"
2.66"
2.32"
2.16"
4.68"
3.04"
4.40"
3.03"
2.31"
2.15"
4.08"
2.93"
2.52"
2.28"
2.14"
3.98"
2.89"
2.50"
2.24"
2.12"
3.67"
2.81"
2.49"
2.22"
2.11"
3.55"
2.74"
2.21"
3.53"
2.72"
2.41"
2.20"
3.51"
2.38"
2.18"
3.31"
2.36"

38. Bangor International Airport (#170355) – 1953-2008 (52 years)
Annual Maximum Series
Bangor International Airport (#170355) – (52 years)
5.98"
2.89"
2.31"
1.94"
1.74"
5.10"
2.81"
2.28"
1.92"
4.68"
2.72"
2.20"
1.89"
1.63"
3.98"
2.68"
2.16"
1.86"
1.52"
3.67"
2.14"
3.55"
2.66"
2.09"
1.51"
3.51"
2.08"
1.82"
1.47"
3.23"
2.50"
1.81"
1.35"
3.09"
2.38"
2.02"
3.03"
2.36"
2.01"
1.79"
2.93"
2.32"
1.95"
1.75"

39. Partial Duration Series
Hartford Bradley International Airport (#063456) – (59 complete years)
7.70"
4.04"
3.15"
2.90"
2.72"
2.48"
6.27"
3.75"
3.12"
2.70"
2.47"
5.88"
3.68"
3.07"
2.89"
2.67"
5.72"
3.33"
3.06"
2.85"
2.60"
2.46"
5.26"
3.32"
2.99"
2.56"
5.22"
3.31"
2.98"
2.84"
5.10"
3.30"
2.55"
4.81"
3.25"
2.96"
2.78"
2.53"
4.41"
3.22"
2.76"
2.52"
4.31"
3.21"
2.94"
2.73"
2.51"
4.05"
3.19"
2.92"

40. Annual Maximum Series
Hartford Bradley International Airport (#063456) – (60 complete years)
7.70"
3.31"
2.92"
2.55"
2.14"
1.54"
5.88"
3.30"
2.90"
2.51"
2.09"
1.51"
5.72"
3.22"
2.47"
1.85"
5.26"
3.21"
2.89"
2.46"
1.83"
1.49"
5.22"
3.19"
2.85"
2.42"
1.81"
5.10"
3.12"
2.84"
2.36"
1.80"
4.81"
3.07"
2.73"
4.31"
2.99"
2.70"
2.29"
1.79"
4.05"
2.98"
2.67"
2.24"
1.67"
4.04"
2.96"
2.60"
2.20"
1.66"
3.33"
2.94"
2.56"
2.16"
1.60"

41. Partial Duration Series
Providence TF Green Airport (#376698) – (76 complete years)
6.31"
4.23"
3.38"
3.08"
2.87"
2.76"
2.62"
6.17"
3.95"
3.37"
3.06"
2.86"
2.74"
2.60"
5.43"
3.73"
3.31"
3.04"
2.73"
5.39"
3.62"
3.29"
3.02"
2.85"
5.15"
3.57"
3.28"
2.72"
2.59"
4.78"
3.52"
2.97"
2.82"
2.70"
2.57"
4.75"
3.47"
3.23"
2.92"
2.81"
2.66"
4.71"
3.46"
3.18"
2.91"
2.80"
4.38"
3.15"
2.90"
2.78"
2.64"
2.56"
4.37"
3.42"
3.14"
2.54"
4.30"
3.40"
3.12"
2.77"
2.63"

42. Providence TF Green Airport (#376698) – 1932-2008 (77 complete years)
Annual Maximum Series
Providence TF Green Airport (#376698) – (77 complete years)
6.31"
4.23"
3.28"
2.85"
2.54"
2.23"
1.95"
6.17"
3.95"
3.23"
2.78"
2.22"
1.92"
5.43"
3.73"
3.15"
2.76"
2.51"
2.20"
5.39"
3.62"
3.14"
2.73"
2.45"
2.17"
1.88"
5.15"
3.57"
3.12"
2.72"
2.12"
1.87"
4.78"
3.47"
3.06"
2.70"
2.42"
1.86"
4.75"
3.46"
3.04"
2.66"
2.11"
1.74"
4.71"
3.38"
2.97"
2.64"
2.35"
2.10"
1.70"
4.38"
3.37"
2.91"
2.59"
2.31"
2.07"
1.61"
4.37"
3.29"
2.90"
2.57"
2.27"
2.05"
1.57"
4.30"
2.86"
2.25"
1.96"
1.51"

43. Partial Duration Series
Boston Logan Internation Airport (#190770) – (72 complete years)
7.06"
3.84"
3.11"
2.81"
2.64"
2.52"
2.42"
6.11"
3.77"
3.00"
2.80"
2.40"
5.69"
3.58"
2.98"
2.77"
2.63"
2.50"
5.63"
3.51"
2.95"
2.60"
4.88"
3.49"
2.94"
2.76"
2.59"
2.49"
2.39"
4.71"
3.36"
2.91"
2.38"
4.47"
3.34"
2.90"
2.71"
2.58"
2.47"
4.29"
3.32"
2.89"
2.67"
2.55"
2.46"
4.21"
3.31"
2.66"
2.54"
4.12"
3.16"
2.87"
4.00"
3.15"
2.82"
2.53"

44. Annual Maximum Series
Boston Logan Internation Airport (#190770) – (73 complete years)
7.06"
3.51"
2.90"
2.63"
2.36"
2.13"
1.81"
6.11"
3.49"
2.89"
2.59"
2.34"
2.11"
1.75"
5.69"
3.34"
2.82"
2.33"
2.10"
1.73"
5.63"
3.32"
2.77"
2.54"
2.05"
1.71"
4.71"
3.15"
2.76"
2.32"
2.04"
1.65"
4.29"
3.11"
2.52"
2.29"
2.00"
1.48"
4.21"
3.00"
2.66"
2.26"
1.99"
4.12"
2.98"
2.64"
2.49"
2.25"
1.90"
4.00"
2.95"
2.46"
2.19"
1.87"
3.84"
2.94"
2.15"
1.84"
3.58"
2.91"
2.40"

45. Selecting a Distribution
Wilks,D.S., 1993: Comparison of three-parameter probability distributions for representing annual extreme and partial duration precipitation series, Water Resources Research, 29,

46. Selecting a Distribution
Wilks,D.S., 1993: Comparison of three-parameter probability distributions for representing annual extreme and partial duration precipitation series, Water Resources Research, 29,

47. Filtering

48. Spatial Interpolation and Smoothing
It became clear we needed to smooth our Beta-P results based on Distance to Nearby Stations and the Period of Record of Nearby Stations.
From the August Journal of Hydrology: “Regionalization of extreme precipitation estimated for the Alabama rainfall atlas” (Durrans & Kirby)

49. Regionalization Demonstration
Tully, NY
1day 100yr: 5.95”
Distance: 28 miles
Record Len.: 40 yrs.
Auburn, NY
1day 100yr: 4.89”
Distance: 33 miles
Record Len.: 93 yrs.
Ithaca, NY
1day 100yr: 5.58”
Ithaca, NY Estimate
1day 100yr: 5.30”
Elmira, NY
1day 100yr: 5.45”
Distance: 31 miles
Record Len.: 114 yrs.
Binghamton, NY
1day 100yr: 5.46”
Distance: 29 miles
Record Len.: 61 yrs.

50. NRCC QC Process AUTOMATIC
Data is pre-screened by climate center staff each month, and flagged if suspect, erroneous, or an accumulated value.
Unusually high daily data values are checked against nearby stations. If a daily rainfall value exceeds 10”, at least two nearby stations (within 200 miles) must also have reported amounts of at least 5”. If a daily rainfall value exceeds 5”, at least two nearby stations must also have reported amounts of at least 3”.
Hourly precipitation data are checked against corresponding daily data. For each hour's data, at least one nearby station must have recorded a higher daily total rainfall amount.
After the distribution is run for the entire Northeast, stations outside more than 2 standard deviations than the mean of all stations are removed.

51. Quality Control – Last Step
Any stations outside 2 standard deviations
IGNORED.
Any stations outside
± 2.25”
IGNORED.
51 stations ignored
17 stations ignored

52. Gridding

53. Smoothing

54. Raw Data

55. Gridded Data

56. Smoothed Data

57. Final Output

58. Confidence Intervals

59. Confidence Intervals Approach
Monte Carlo Approach
Draw 1,000 x-year samples from fit Beta-P distribution at each station.
Refit Beta-P based on random samples.
Compute return period amounts for confidence intervals (90%)
Analogous to Atlas14’s approach

60. Climate Change

61. Extreme Precip in a Changing Climate
U.S. Global Change Research Program Global climate change impacts in the United States: a state of knowledge report. Cambridge [England]: Cambridge University Press.

62. Extreme Precip in a Changing Climate
DeGaetano, Arthur T., 2009: Time-Dependent Changes in Extreme-Precipitation Return-Period Amounts in the Continental United States. J. Appl. Meteor. Climatol., 48, 2086–2099.

63. Extreme Precip in a Changing Climate
DeGaetano, Arthur T., 2009: Time-Dependent Changes in Extreme-Precipitation Return-Period Amounts in the Continental United States. J. Appl. Meteor. Climatol., 48, 2086–2099.

64. Extreme Precip in a Changing Climate
Example:
Reagan Airport, DC (#448906)
1 day duration
Beta-P distribution
79 years of record through 2008
through 2000
through 2008
1-yr
2.46”
2.58”
2-yr
2.65”
2.78”
5-yr
3.53”
3.76”
10-yr
4.39”
4.73”
25-yr
5.85”
6.39”
50-yr
7.28”
8.03”
100-yr
9.05”
10.09”
200-yr
11.25”
12.68”
500-yr
15.00”
17.15”

65. Sample Changing Climate Product: Percent Difference Maps

66. Sample Changing Climate Product: Comparison Chart

67. Daily Monitoring

68. Project Timeline Jan 2009 Project start Apr 2009
Sub-daily analysis, Hourly analysis, Comparison between NRCC results and Atlas14
Jul 2009
Daily analysis, Multi-daily analysis, Gridding and smoothing processes, Develop isohyetal maps
Oct 2009
Compute confidence intervals, Intensity frequency duration curves, Site-specific distribution curves, Atlas14-like data files
Jan 2010
Beta version of web site to allow for user feedback and testing
Apr 2010
Software for real-time monitoring, Modifications from beta testing
July 2010
Finalize web site, Technical documentation and users guide
Oct 2010
Beta version of real-time monitoring web site, Complete documentation
Jan 2011
Finalize real-time monitoring site

69. Taking It to the Web

70. Lots of Data
430,243,488 data values packed into a file using HDF5 architecture (~2.66 gigabytes) plus 486 GIS ASCII raster files (~6.33 gigabytes) and 3,888 state and regional maps (~0.5 gigabytes)