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Development of a Quality Controlled Snowstorm

DatabaseAnna Wilson

Faculty/NCDC Advisor: Mike Squires

April 2009

Outline

• Background• NESIS, RESIS, the Snowstorm Database

• QC Procedures• Delineate storm, create grid, manual check

• Future Work• Uses for the public, database expansion

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Northeast Snowfall Impact Scale

• NCDC began calculating this index in the 2005-2006 season

• Uses data east of the Rocky Mountains to evaluate Northeast snowstorms

• Constants in the NESIS algorithm are determined by top 30 Northeast storms – Snowfall area, snowfall amount, population

density

Regional Snowfall Impact Scale

• Based on NCDC climate regions for easy integration with other products

• Expressed in percentiles to facilitate historical comparison

• Algorithm is currently in development

• National snowfall index will be computed as well as a separate index for each region

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Snowstorm Database

• Comprised of top 100 storms since 1900

• Used to calculate national index

• Presented in GIS – Inclusion of other information will assist users in

assessment of societal impacts• Hospitals, schools, transportation networks

Data Source

• Automated QC done on databases

• Used newest, “best” data: GHCN-D

• Snowstorm is put in a GIS environment

• Zero values are discarded– Eliminates part of one problem – zero values that

should be reported as missing

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QC Step 1: Delineate the storm.

January 13-16, 1918

QC Step 1: Delineate the storm.

January 12-15, 1982

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Day 1: January 12, 1982

Day 2: January 13, 1982

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Day 3: January 14, 1982

Day 4: January 15, 1982

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QC Step 2: Run Script

• Flags suspiciously different points using Moran’s I statistic

• Removes values of less than 6 inches if any dates have missing values

• Creates grid using an inverse distance weighted technique

QC Step 3

• Manually check the data– Expect basic spatial continuity

– Variation can result from….

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Variation in TopographyJanuary 11-14, 1964

Lake Effect SnowJanuary 6-9, 1988

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Different Observing TechniquesJanuary 6-9, 1996

Temperature VariationDecember 10-13, 1992

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Quality Control Goals

• Use consistent, repeatable procedures so that different analysts get the same results

• Type I or Type II error – Choose to keep points if it is not absolutely clear

they are incorrect

• Questions– Should a zero value actually be reported as

missing?

– Is there an order of magnitude error?

January 15-17, 1945

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January 12-15, 1979

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Conclusions and Future Work

• Rigorous, robust QC important for accuracy– ~1.3% of data taken out per storm

• Range: 0.61% - 3.19%

• Snowstorm database will have widespread applications– Expansion to include other parts of the country

– Assist in development of regional/national indices

– User input will determine new information to include in the GIS interface

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References

• Doesken, N.J., and A. Judson, 1996: The Snow Booklet: A Guide to the Science, Climatology and Measurement of Snow in the United States. Colorado State University, 85 pp.

• Kocin, P.J. and L.W. Uccellini, 2004: A Snowfall Impact Scale Derived From Northeast Storm Snowfall Distributions. Bull. Amer. Meteor. Soc., 85, 177-194

• Kocin, P.J. and L.W. Uccellini. Northeast Snowstorms, vol. 1 and 2. Boston: American Meteorological Society, 2004.

• Squires, M.F. and J.H. Lawrimore, 2006: Development of an Operational Snowfall Impact Scale. 22nd IIPS, Atlanta, GA.

• Squires, M.F., J.H. Lawrimore, et. al., 2008: Development of Operational Regional Snowfall Indices. 24th IIPS, (Atlanta GA?)