Regional Snowfall Index
| category | RSI values | description |
|---|---|---|
| 1 | 1-3 | Notable ("noteworthy") |
| 2 | 3-6 | Significant ("significant") |
| 3 | 6-10 | Major ("difficult") |
| 4th | 10-18 | Crippling ("paralyzing") |
| 5 | > 18 | Extreme ("extreme") |
The Regional Snowfall Index (RSI) is a system used by NOAA to assess the societal impact of winter storms in the six easternmost regions of the United States . The system replaced the Northeast Snowfall Impact Scale (NESIS), which the National Climatic Data Center (NCDC) began using in 2005. The NCDC has retrospectively calculated RSI values for more than 500 winter storms since 1900.
The index takes into account population and regional differences to assess the impact of the snowfall. For example, in areas where there is less snow on average, a higher value is calculated for the same amount of snow than in areas where heavy snowfalls are not uncommon.
method
Four thresholds based on climatological records have been set in each region:
- a quarter of the amount of snow that usually occurs once every ten years
- half the amount of snow that typically falls once every 25 years
- the amount of snow that typically falls once every 25 years
- one and a half times the amount of snow that typically falls once every 25 years
For example, in the northeast, one location has 16 inches of snow every ten years and 20 inches every 25 years, so the thresholds are 4, 10, 20, and 30 inches.
For each threshold and in each region, the area and the number of inhabitants associated with the baseline are determined, and for a given storm, the area in which the snowfall exceeds one of the thresholds is normalized using the value associated with the baseline. For example, in the northeast, the area of four inches or more of snow is divided by 149,228 square miles and the number of residents affected by 51,553,600 (based on 2010 United States Census data ). This results in eight different values that show how far-reaching the particular snowstorm is in comparison to the snowstorms worth mentioning (that is, the category 1 snowstorms) in the region. The area and population that belong to the respective baseline corresponds to the average area and population of large-scale snowstorms, so that these eight different values assume the value 1 for the purpose of calibration on the average of the storms classified as significant. The RSI is the sum of these eight values.
See also
literature
- Michael F. Squires, Jay H. Lawrimore, Richard R. Heim Jr .: The Regional Snowfall Index . In: Bulletin of the American Meteorological Society . tape 95 , no. 12 , 2014, ISSN 0003-0007 , p. 1835-1848 , doi : 10.1175 / BAMS-D-13-00101.1 .