1. Spatial distribution of tropical cyclone rainfall and its
contribution to the precipitation climatology of Puerto Rico
SEDAAG 2015
PhD Student Honors Competition
José J. Hernández Ayala
Department of Geography
University of Florida
2. Introduction
• Puerto Rico is highly exposed to tropical cyclone rainfall (TCR),yet little is
known about the spatial and temporal characteristics of this precipitation.
• This study focuses on two main questions:
1) Is TCR randomly distributed or is it clustered in some regions?
2) How much TCs contribute to the rainfall climatology of the island?
3. Literature
• No study has looked at the spatial distribution of TCR or its contribution to the
climatology of Puerto Rico.
• Some studies have focused on the role that individual TCs like hurricanes Hugo
(1989), Hortense (1996) and Georges (2008) have played in extreme flood events
(Torres-Sierra, 1997; Larsen and Santiago-Roman, 2001; Smith et al., 2005).
• TCR variability over Puerto Rico is mostly influenced by environmental moisture
distribution and storm center distance from the island’s coast (Hernández and
Matyas, 2015).
• Storms over moisture environments of 44.5 mm or > of total precipitable water
and storm center distances of 230 km or less were associated with mean TCR
values of 50 mm or more for the island.
5. Data
• Tracks of TCs from the International Best Track Archive for Climate
Stewardship (IBTrACS) that were at least tropical depressions and spent 12
hours or more within a 500 km radius around the island.
• Daily and monthly rainfall totals were obtained from the National Climatic
Data Center (NCDC) for 32 rain gauges located on the main island of Puerto
Rico for the years 1970-2010.
• Digital elevation model (DEM) was obtained from the US Geological Survey
(USGS) and the percent rise slope and aspect were calculated in a GIS.
7. Methods
• Four different group means for all 32 stations for the 86 TCs.
• Proximity to the center of the storm and environmental moisture are the most
important factors when it comes to overall TCR variability over Puerto Rico.
• The groups of TCs were divided considering those two key variables.
• Groups are: 1)All 86 TCs, 2) Land falling TCs, 3) TCs with closer circulation
centers (230 km or more) and higher moisture (44.5 mm or more) and 4) Farther
TCs (230 km or less) over lower moisture environments (44.5 mm or less).
8. Methods: Spatial Distribution of TCR
• Two geo-statistical interpolation methods were implemented.
• 1) Ordinary Kriging (ORK):generates an estimated surface from a
scattered set of points with z-values, this is done by first fitting a model
and then making a prediction.
• 2) Ordinary Cokriging (OCK):a multivariate extension of kriging that
was implemented to examine the TCR-topography relationship.
• Both methods were compared by implementing a cross-validation
procedure that uses the root mean square error (RMSE) to determine the
accuracy of the methods.
9. Methods: TCs Contribution
• The contribution of rainfall associated with TCs was estimated for each
month of the hurricane season.
• This was done by calculating a percentage between monthly total rainfall
and accumulated TCR for all storms over the 1970-2010 period.
• For example, if a station had a total monthly value of 10,000 mm for the
given time period and an accumulated TCR of 800 mm, the percentage of
contribution of TCs to overall precipitation on that rain gauge is 8%.
• Ordinary kriging was used to map the contribution percentages for each of
the months of the hurricane season.
10. Results: TC Characteristics
Kernel density surface of a) all 86 TC tracks, b) Closer and higher
moisture TCs c) landfilling TCs and d) Farther and lower moisture TCs .
a) number of TCs per year within 500 km radius of Puerto Rico, b) number of
TCs per month and c) number of TCs by Saffir-Simpson Categories
11. Results: Spatial Distribution of TCR I
All 86 Events
LF TCs (8)
ORK
ORK
OCK (elevation and slope)
OCK (slope and aspect)
12. Results: Spatial Distribution of TCR II
Closer and higher
moisture TCs
Farther and lower
moisture TCs
ORK
ORK
OCK (slope)
OCK (aspect)
13. Results: Spatial Distribution of TCR III
All 86 TCs Land falling TCs
Closer and higher moisture TCs Farther and lower moisture TCs
17. Conclusions
• Results show that for all TC groups, TCR tends to be cluster in the southeastern
and central regions of the island with a decrease in values as we move west.
• High values of TCR were found in the high elevated areas of the southeast and
central mountains.
• The month with the largest contributions (>20%) for most of the stations was
August followed by September, while the months with the lowest contributions
were June and July.
• For August, the stations in the south and eastern portions of the island had TCR
percentages of more than 25%with a few stations in the southern coastal
plains exhibiting 30%.
