1. 1 NOHRSC Challenges of using Snow Data Carrie Olheiser Office of Hydrologic Development National Weather Service, NOAA U.S. Department of Commerce National Operational Hydrologic Remote Sensing Center www.nohrsc.noaa.gov

2. 2 NOHRSC National Snow Analyses (NSA) Ground Airborne Satellite Multi-sensor Snow Observations Data Products Interactive Maps Time Series Plots Text Discussions Snow Information Products Snow Modeling and Data Assimilation Numerical Weather Prediction Model Forcings Gridded Snow Characteristics U.S. 1-km 2 Hourly

3. 3 NOHRSC Nature of snow observations. Difficult to get “representative” observation. Metadata inconstancies between sources. Data in proper SHEF format including time, amount and duration. Snowfall observations are not always published in a standard format. Timeliness of data Reliably and timing of observations. Adequate training in data collection. Quality controlling the data, who is responsible? Challenges of snow data

4. 4 NOHRSC NOHRSC performs 4 automated tests –Reasonable Range –Spatial Consistency –Temporal Consistency –Internal Consistency Reasonable range is the only QC test Snowfall data undergoes. Quality Controlling of Data

5. 5 NOHRSC

6. 6 Manual Quality Control Spatial Consistency These points need to be looked at more closely, not spatially consistent

7. 7 NOHRSC Manual Quality Control Temporal Consistency Bad Observation Using data operationally does not allow us to see into the future for temporal quality control. Unstable SNOTEL Observation In early season and late season

8. 8 NOHRSC Manual Quality Control Internal Consistency Density Check

9. 9 NOHRSC Station Representativeness Point in Pixel ESTES PARK RAWS

10. 10 NOHRSC Point in Pixel Consistency ? Elevation –Differences in station elevation and 1 km X1 km DEM elevation vary as much as 1500 meters, example station KRWW4, DEM elevation = 1439 Reported elevation = 2910 Forest Cover Density –Photos from the Northwest SNOTEL sites and model forest cover density disconnects. –Example from Caribou Maine and station KCAR.

11. 11 NOHRSC Disconnects between ground survey coop results for the March 1 to March 4 Survey Forest Density Issues and Stations not representative of the region. Caribou, ME SWE reported March 1, 2004 is 0.038 meters. KCAR is a Coop Station located at the Airport in the large wind swept location that is well exposed with a forest density of ~ 6%. Caribou, ME SJ snow survey site. SWE reported March 1, 2004 is 0.104 meters. This station is reported by the USGS and measured at the medical clinic which is a more heavily wooded area. Assimilation for the region used KCAR a regular reporter in the season but turns out it was not representative of the region. This was not the only station with similar issues.

12. 12 NOHRSC 72 hr Snowfall Observations

13. 13 NOHRSC It was agreed at the NWS 2004 Cold Regions Hydrology Workshop (Kansas City, 2004 November 15-19) that the NOHRSC would develop web-based, real-time, automated, interactive, snowfall maps for the CONUS. History of NOHRSC Snowfall Products

14. 14 NOHRSC National Metadata Sources Over 40 different sources of station metadata Often redundant, often inconsistent! NEED ONE-STOP SHOPPING FOR STATION METADATA National Weather Service Databases NWSLI, MADIS, CSSA (B44’s), NWS-ICAO, NWS-METAR, HADS, NCDC National Weather Service Databases NWSLI, MADIS, CSSA (B44’s), NWS-ICAO, NWS-METAR, HADS, NCDC NRCS SNOTEL and Snow Courses USACE New England District Snow Surveys New York City Dept. Environmental Protection Federal Aviation Administration California Department of Water Resources Maine Cooperative Snow Survey MesoWest (150 + Smaller mesonets) RAWS Remote Automated Weather Stations Federal and State Agencies Weather Forecast Offices, River Forecast Centers and Regional Offices

15. 15 NOHRSC Importance of Accurate Metadata Numerous databases leads to uncertainties in the station metadata.

16. 16 NOHRSC Willow Creek, Wyoming

17. 17 NOHRSC 99 Miles Boulder Creek, Oregon

18. 18 NOHRSC 72 hr SWE Observation

19. 19 NOHRSC Quality Control of Data Internal Quality Control Manual Quality Control Point in Pixel Consistency

20. 20 NOHRSC Internal Quality Control Behind the scenes 4 QC tests are run –Reasonable Range –Spatial Consistency –Temporal Consistency –Internal Consistency Problems with losing to much data if we have strict requirements in an automated quality control scheme. The nature of snow variability makes qc difficult and as much data is needed as possible.

21. 21 NOHRSC PRODUCTS Hourly and Daily 1 km 2 Resolution INTERNET Interactive Maps 3D Visualization e.g. Google Earth Time-series loops National/Regional Discussions Text summaries by watershed Point Queries DIRECT FEED Push or Pull Gridded Data Flat Binary or GIS-ready

22. 22 NOHRSC It was agreed at the NWS 2004 Cold Regions Hydrology Workshop (Kansas City, 2004 November 15-19) that the NOHRSC would develop web-based, real-time, automated, interactive, snowfall maps for the CONUS. History of NOHRSC Snowfall Products

23. 23 NOHRSC NOHRSC has seven (7) new snowfall maps to the NOHRSC selection of Physical Elements on the NOHRSC Interactive Snow Information page. Daily total snowfall observations (for previous 24 hours) 2-day total snowfall observations (for previous 48 hours) 3-day total snowfall observations (for previous 72 hours) Daily total snowfall interpolation (for previous 24 hours) 2-day total snowfall interpolation (for previous 48 hours) 3-day total snowfall interpolation (for previous 72 hours) 24-hr Raw Snowfall – Only displays 24 hour totals NOHRSC Snowfall Products

24. 24 NOHRSC Interpolated Snowfall 24 hrs

25. 25 NOHRSC Are generated in automated process that uses snowfall data encoded in SHEF and MADIS formats received at the NOHRSC over AWIPS and MADIS Snow Collective. The NOHRSC performs only a “reasonable range” quality-control test on the snowfall data. Snowfall maps are generated using both –Temporal quantization and integration –spatial interpolation inverse distance weighting with a search radius of 75km. NOHRSC Snowfall Products

26. 26 NOHRSC Total Observed Snowfall 24 Hrs

27. 27 NOHRSC Total Observed Snowfall 72 Hrs

28. 28 NOHRSC Total Observed Snowfall 72 Hrs

29. 29 NOHRSC Interpolated Snowfall 48 hrs

30. 30 NOHRSC Interpolated Snowfall 72 hrs

31. 31 NOHRSC Snowfall Text Products Raw Data Available for Download

32. 32 NOHRSC Cumulative Snowfall Product Two stations located a couple kilometers apart. Both reporting snowfall, but MITM2 is reporting zero snowfall. Some station do not have a continuous record of snowfall, missing significant events. These products need to be used with a watchful eye!