In this bonus task, perform manual quality control checks for annual maximum data collected in Task 1 of the workshop. 

  1. If you are continuing from the previous tasks, check to see if the "all_data" data frame is in your global variables. If not, load the “clean_precip_data.RData” in the data/ folder
  2. Inspect the “all_data” data frame
  3. Recall, in Task 1, we removed all data points that had a quality flag
  4. Take a look at the GHCN documentation and identify the different quality flags: https://www.ncei.noaa.gov/pub/data/ghcn/daily/readme.txt
  5. Compare this to the data in “all_data”. What quality flags are present, and what do they represent?
  6. Sort the data to view the largest daily precipitation
  7. Do these values have quality flags? Do the values seem realistic?
  8. Pick a data point that has a quality flag and has a very large precipitation value. We will search historical records to determine whether or not the measurement is accurate. For simplicity, pick a data point post-1951, as we would need to search other data sources for dates prior to 1951.
  9. Look up the station name and location using the station ID and the “stations_metadata” data frame. You can use the search bar in the top right to quickly search using the ID
  10. One source of historical precipitation reports is the Hourly Precipitation Data (HPD) reports, which are available starting in 1951: https://www.ncdc.noaa.gov/IPS/hpd/hpd.html
  11. Select the state for your chosen station, then select the year and month for the chosen GHCN measurement. Inspect the daily precipitation measurements in the report and decide whether the GHCN value should be included or excluded.