IVT thresholds used by the Viale_SAmerica algorithm:

Grid-point IVT must exceed the following relative thresholds:

1. 85th percentile within the AR structure
2. The mean direction of IVT withing the AR structure must be from the NorthWest

then the object with enhanced IVT must meet the following criteria:

3. Length criterion: 1500 km north of 35°S and 2000 km south of 35°S
4. Width criterion: ratio of area to length greater than 2 (i.e., length must double 
the width, following the typical long and narrow structure) 
5. Object must make landfall on the west coast of South America
6. Object must be associated with a frontal zone overlaping or inmediate south of the 
   the object. 
   
NOTE: Percentiles are calculate separately for each grid box and month,
considering the time period 1980-2017 within a window of 5 months
centered at the month under consideration. 

More details on the method can be found in:

Viale M., R. Valenzuela, R. Garreaud, F.M. Ralph (2018): Impacts of atmospheric
rivers on the southern South America. Journal of Hydrometeorology. In review

Based on this algorithm, an AR archive has been built for southern
America, covering 1980-2017 and the region of 180°W-35°W and 10°N-70°S:

Contact: maxiviale@mendoza-conicet.gob.ar