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

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

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

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.

Sources of Snow Data in GHCN-Daily United States U.S. Cooperative Observers Network (COOP) NCDC-3206 (Pre-1948) NCDC-3200 (1948-2010) 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

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

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

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

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

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

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

# of Stations Reporting Snow Depth (January)

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

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

# of Snow Depth Stations by Source United States

# of Snow Depth Stations by Source United States

# of Snow Depth Stations by Source Outside United States

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

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

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)

Potential new GHCN-Station

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

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)

Historical perspective on major source adds and monthly “refreshes”

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

Snow Monitoring https://www.ncdc.noaa.gov/snow-and-ice/

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

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

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

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

Regional Snowfall Impact Scale August 19, 2013 CLASS Operational Transition

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

Thank You! For further information: http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/ Jay.Lawrimore@noaa.gov Matthew.Menne@noaa.gov

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

Number of Stations by Year by element

Snow depth record length

Snow Monitoring; Monthly Summaries

Snow Monitoring; Monthly Summaries