1. Global Snow Data Collections and Monitoring at NOAA’s National Centers for Environmental Information
Jay Lawrimore, Matt Menne
NOAA’s National Centers for Environmental Information
(Formerly National Climatic Data Center)
Asheville, North Carolina, USA
2nd Snow Watch Meeting
Ohio State University
June 13-14, 2016

2. Outline In-situ Data Sets at NCEI Sources of snow data
Global Historical Climatology Network-Daily Data Set
Sources of snow data
Stations Reporting Snow Depth US
Global
QC checks
Tailored Product
Regional Snowfall Impact Scale
Access

3. In situ datasets at NCEI: Global Historical Climatology Network-Daily
U.S. and global daily in situ dataset derived from multiple (~30) sources
Comprehensive daily dataset for the USA with good coverage over many other parts of the world
Integrates latest U.S. daily source archives and real-time updates for many U.S. Networks as well as Canada. GTS updates for non-U.S. sites in some cases. Monthly updates for Australia, ECA&D sites.
>50,000 snowfall or snow depth stations
Uses ISD’s “Global Summary of the Day” as a source for snow depth observations outside the U.S. and Canada
>30,000 temperature stations and >90,000 precipitation stations

4. Sources of Snow Data in GHCN-Daily
U.S. Cooperative Observer Network
Volunteer, once per day observations. Dates to 19th Century--many thousands of sites. Snowfall and snow depth reports.
U.S. City and Airport Sites
Met Service or contract personnel--also once per day for snow depth. Hundreds of locations, some dating to 19th Century.
SNOTEL
Used for water resource management in the Western U.S. Currently about 750 sites in GHCN-Daily (most since 2000). Snow water equivalent and snow depth.
CoCoRaHS
New volunteer network in the U.S. Dates to 1998 in Colorado and became nationwide in the 2000’s. Recently expanded into Canada. Once per day, includes snowfall, snowdepth, snow water equivalent in some cases. About 10,000 observations per day.

5. Sources of Snow Data in GHCN-Daily United States
U.S. Cooperative Observers Network (COOP)
NCDC-3206 (Pre-1948)
NCDC-3200 ( )
NCDC-3207; WxCoder (2011-Present)
U.S. City and Airports
NCDC-3210
ISD (Integrated Surface Dataset)
Snotel (~2000-Present)
CoCoRaHS (~2000-Present)
August 19, 2013
CLASS Operational Transition

6. Sources of Snow Data in GHCN-Daily
Integrated Surface Data (ISD)*
Contains global hourly and synoptic observations
Comprises over 20,000 stations worldwide
Currently over 11,000 stations "active" and updated daily in the database.
Is the Primary source of Snow Depth data for stations outside the U.S. and Canada
Snow Depth integrated into GHCN-Daily each day via GSOD
Global Summary of the Day (GSOD)
Taken from synoptic snow reports transmitted over the GTS. Snow depth only
Tends to be incomplete with higher error rates than in other sources
*Developed as a joint activity within Asheville's Federal Climate Complex. Data feed and new additions managed by the 14th Weather Squadron of the U.S. Air Force.
NOAA/NCEI’s ISD is the public facing version of the Air Force database

7. Sources of Snow Data in GHCN-Daily
Environment Canada
Daily database shared with NOAA as part of a long-standing bi-lateral agreement
Includes snowfall and snow depth
Received daily via ftp (2 to 3 days)
European Climate Assessment & Dataset (ECA&D)
Provide special feed for GHCN-Daily. Many long records in Nordic countries. Snow depth only.
Received once each month on the 15th via ftp
Timeliness varies by country

8. In situ datasets at NCEI: Global Historical Climatology Network-Daily
SNOWFALL
22,899 stations with >=10 years of Snowfall observations
10,901 stations with >=10 years and reported since 2010
SNOW DEPTH
24,331 stations with >=10 years of Snow Depth data
13,428 stations with >=10 years & reported since 2010
9,542 stations with >=10 years & reported in 2016

9. Stations Reporting Snowfall (>=10yrs Data and Reported since 2010)

10. Stations Reporting Snow Depth (>=10yrs Data and Reported since 2010)

11. Stations Reporting Snow Depth (>=10yrs Data and Reported in 2016)

12. # of Stations Reporting Snow Depth (January)

13. # of Stations Reporting Snow Depth U.S. (January)

14. # of Stations Reporting Snow Depth Outside U.S. (January)

15. # of Snow Depth Stations by Source United States

16. # of Snow Depth Stations by Source United States

17. # of Snow Depth Stations by Source Outside United States

18. Water Equivalent of Snow Depth (>=1Yr Data and Reported in 2016)

19. Number of Stations Reporting Water Equivalent of Snow Depth U. S
Number of Stations Reporting Water Equivalent of Snow Depth U.S. (January)

20. Updates and Maintenance: GHCN-Daily
Data are updated each day
All historic sources are “reprocessed” weekly
Dataset is completely reassembled each weekend from primary sources to maintain consistency between each archive source and the integrated dataset
QC checks are applied to entire period of record with each reprocess
Strict versioning of dataset (all versions are archived)

21. Potential new GHCN-Station

22. Quality Assurance
19 different checks most of which can be applied to each of the major five elements (when appropriately tailored)
Low false positive rate overall (i.e., very limited “collateral damage”)
Total flag rate equal to approximately 0.24% of all values (highest flag rates for snowfall and snow depth). 1-2% of the flags are estimated to be false positives (i.e., valid values flagged as bad)
System can be run “unsupervised”
Uniform QC for full period of record

23. Quality Assurance Types of checks: Basic integrity
Value >0 and flag=Trace
90 or more consecutive identical nonzero SNWD values
SNWD<0 or >11460mm (451.2 inches)
Outlier
Gap in SNWD distribution for stn/month >= 350mm (13.8 inches)
Internal and Temporal Consistency
Daily increase in SNWD and TMIN >=7C (44.6F)
Daily increase in SNWD Greater than Snowfall
Daily increase in SNWD >=100mm AND PRCP=0
Daily increase in SNWD >=200mm AND SNWD >100*PRCP
Spatial Consistency
Too warm to snow; Increase in SNWD > 0 & Tmin at Nabors >=7C
(Described in Durre et al. 2010)

24. Historical perspective on major source adds and monthly “refreshes”

25. Four facets to GHCN-Daily Processing
Daily updates (automated) – Updates Data values
Updates values that are new since yesterday’s update
Weekly reprocessing (automated) – Updates Data Values
Reintegrates source databases and reruns quality checks on all values. Helps to ensure that GHCN-Daily is synchronized with its external constituent sources, but does not add new stations
Monthly refreshes for select U.S. networks (automated, but requires approval/manual intervention to deploy refreshed list) – Updates Membership in GHCN-Daily
Removes and reintegrates active data sources for Coop, CoCoRaHS and CRN. Adds stations that are new since last monthly refresh
Periodic adding of new sources or refreshing of large existing data sources (semi-automated) – Updates Membership in GHCN-Daily
Removes and reintegrates large data sources to incorporate station additions since last refresh

26. Snow Monitoring

27. Tailored Snow Product Regional Snowfall Impact Scale
Measures the magnitude (impact) of snowstorms on a regional scale
Uses Snowfall Amount
And Population (2010 Census)
Calibrated to the climatology of each region based on region-specific thresholds
August 19, 2013
CLASS Operational Transition

28. Example from 2 Storms in Southeast U.S.
August 19, 2013
CLASS Operational Transition

29. CLASS Operational Transition
RSI Categories
August 19, 2013
CLASS Operational Transition

30. RSI Storms in the Northeast
August 19, 2013
CLASS Operational Transition

31. Regional Snowfall Impact Scale
August 19, 2013
CLASS Operational Transition

32. Issues, Gaps, Priorities
Further improve timeliness
15 years ago, 4 month delay
10 years ago, 1 month delay
5 years ago to today, Day before yesterday available this morning
Future: More stations with yesterdays data available this morning
Additional source data
Russia
China
Canada, e.g.
Universal reporting of Zero snow depth (instead of missing)
Water Equivalent of Snow Depth available globally
August 19, 2013
CLASS Operational Transition

33. Thank You! For further information:

34. CLASS Operational Transition
Extra Slides
August 19, 2013
CLASS Operational Transition

35. Number of Stations by Year by element

36. Snow depth record length

37. Snow Monitoring; Monthly Summaries

38. Snow Monitoring; Monthly Summaries