Data collection: The catalog of atmospheric rivers land-falling North American West Coast during 1 January 1948 Ð 31 March 2017

Creators: Shulgina Tamara, Gershunov Alexander
Contributors: F. Martin Ralph, David Lavers, Jonnathan J. Rutz
Date Issued: 2017
Cite this work: Gershunov A., T.M. Shulgina, F.M. Ralph, D. Lavers and J.J. Rutz, 2017: Assessing climate-scale variability of Atmospheric Rivers affecting western North America.ÊGeophysical Research Letters, in review.

Description: 
Atmospheric river detection methodology
NCEP/NCAR Reanalysis (R1) provides humidity and wind data, among other variables, at 6-hourly intervals with 2.5¡ horizontal resolution on 8 pressure levels between 1000 and 300 hPa (1000, 925, 850, 700, 600, 500, 400, 300 hPa) from 1948 (January 1) through 2017 (March 31). Both integrated water vapor transport (IVT) and integrated water vapor (IWV) information is used to detect atmospheric rivers (ARs) making landfall at the North American West Coast, 20 Ð 60¡N, as follows: 
* At each time step, spatial patterns of contiguous grid cells with IVT in excess of 250 kg/m/s and IWV in excess of 15 mm are identified. 
* Those patterns that cross the coastline and are at least 1500 km long in their entirety (offshore + inland) are retained.
* The grid cell corresponding to the IVT maximum along the coast is considered the potential central land-falling location.
* From one time step to the next, maximum movement of two grid points (5¡ north/south) of the central land-falling location is allowed for a continuous AR event. 
* Patterns identified thus are considered ARs if such atmospheric conditions are observed for at least 18 consecutive hours (3 consecutive time steps).
Two AR events making landfall in the same coastal vicinity are considered distinct if they are separated by at least 24 hours (4 time steps). More than one AR is allowed to make landfall contemporaneously if their central land-falling locations are separated by at least 7500 km (7.5¡ north/south, i.e. 3 grid points).

SIO-R1 catalog
The SIO-R1 catalog (txt format) provides an array of variable charactering AR events at the central land-falling location over their land-falling duration. The columns in the data file are:
1. Number of AR
2.ÊYear of AR landfall
3. Month of AR landfall
4. Day of AR landfall
5. Hour of AR landfall
6. Latitude of grid point used to present a center of AR landfall 
7. Longitude of grid point used to present aÊcenter of AR landfall
8. IVT at landfall grid point
9. IWV at landfall grid point
10. U component of wind at 850 Mb over the landfall grid point
11. V component of wind at 850 Mb over the landfall grid pointÊ

6-hourly IVT data
The SIO-R1 catalog is accompanied by the set of 6-hourly IVT data (netCDF format) covering the North American West (hereinafter, the ÒWestÓ) and the eastern North Pacific Ocean [20.0 Ð 60.0¡N, 160 - 100¡W] with 2.5¡ spatial resolution. 
