Acknowledgments

I want to thank Dr. Fernando Gilbes Santaella for the opportunity and all the

support in this work. Also I want to thank the Meteorology Program of University

of Puerto Rico- Mayaguez Campus and Dr. Hector Jimenez for the trust in me

and all the persons that make this possible. Special thanks to Teresa Rodriguez,

Cristimer González and Oscar Hernandez for their revision.

Angela M. Ferrá Elías1 and Fernando Gilbes Santaella2

1Department of Physics, University of Puerto Rico - Mayagüez Campus 2Department of Geology, University of Puerto Rico - Mayagüez Campus

Abstract

In this research we analyze the impact of tropical storms in the ocean color of the Puerto Rico coast. The changes in ocean color are due to the

absorption and scattering of light. It has been shown that remote sensing techniques are used as a fast and economical way to study the

concentrations of phytoplankton and other water constituents at the ocean. Data from MODIS (Moderate Resolution Imaging Spectroradiometer) were

used to generate images of ocean color. The images were downloaded from internet and processed using the program developed by NASA called

SeaDAS. The processing involved the standard atmospheric correction and algorithm application proposed by Morel and Prieur (1977) and Gordon

(1983). Dramatic changes in ocean color were detected due to tropical storms Earl and Jeanne. The results support the use of remote sensing in this

type of assessments.

Introduction

The ocean color is due to the ability of phytoplankton appearing

as different colors in certain bands of the electromagnetic

spectrum because of their chlorophyll concentrations. The lighter

tones are concentrated in coastal areas and darker tones appear

further. These changes in ocean color are due to the absorption

and scattering of the light. In water, absorption is weak in the blue

and strong in the red and for these reasons the ocean is seen

blue.

This is important because it helps understand the life in the ocean

and estimate the concentration of the constituents of the water

such as the phytoplankton, sediment particles suspended in water

and the chlorophyll.

Through this research we will observe and analyze if the pass of

tropical storms affects the color of Puerto Rico’s coast. We will

compare images of the ocean color for two different events

through MODIS.

Figure 2. Chlorophyll-a as estimated using the MODIS satellite sensor before and

after the hurricane Jeanne. The scale in mg m-3 units is the same for all the

images.

Figure 1. Chlorophyll-a as estimated using the MODIS satellite sensor before and

after the hurricane Earl. The scale in mg m-3 units is the same for all the images.

Results

The selected images illustrate the concentration of

chlorophyll-a before and after the passage of the

hurricanes Earl and Jeanne in 2010 and 2004

respectively. Both passed over Puerto Rico as TS.

The green color represents the amount reflected by the

phytoplankton and the color blue is scattered by the

amount of sea water. The black spots represent

interference between the satellite and the Earth surface.

Discussion and Conclusion

The images used were taken randomly. These images showed

that before the passage of the tropical system the

concentration was less than a month after the event. This

means, that the process of discharge is not immediate.

From hurricane Earl the biggest amount of precipitation was

recorded to be approximately 10 inches of rain in the interior of

the island. If we associate this factor with the images taken a

month after the passage of the tropical system we could say

that all the concentration of rainfall received in the interior of

the island takes this time to be discharged into the ocean. This

was also observed in the images of hurricane Jeanne.

In conclusion, we can say that the passage of Jeanne in 2004

and Earl in 2010 caused significant changes in the ocean color

in the coast of Puerto Rico. These changes are due to the

discharges of sediments and nutrients that occur after the rain

event associated with tropical system. These nutrients

increase the concentrations of phytoplankton, therefore

increase the chlorophyll and the sediment.

References

Gordon, H. and A. Morel. 1981. Water Colour Measurements - An Introduction. In:

Oceanography from Space. Edited by. J. Gower, Plenum Press, New York.

Morel, A. and L. Prieur. 1977. Analysis of variations in ocean color. Limnology and

Oceanography, Vol. 22, Num. 4, pp. 709-722.

NASA Science Earth: Ocean Color. Available at: http://science.nasa.gov/earth`

science/oceanography/living-ocean/ocean-color/. Accessed: July 2011.

Webster’s Online Dictionary. Ocean Color definition. Available at: www.websters

-onlinedictionary.org/definition/.../OCEAN+COLOR.html. Accessed: August

2011.

Methodology

A.MODIS sensor

For images about ocean color we use data from MODIS.

MODIS collects information about the variables phytoplankton

and dissolved organic matter in the area of study in this research.

Although this sensor contains 36 bands for the phytoplankton

analysis we only use the bands from 8 to 16.

B. SeaDAS data program

The images were downloaded from internet using the

program developed by NASA, SeaDAS. The SeaWiFS Data

Analysis System (SeaDAS) is a comprehensive image analysis

package for the processing, display, analysis, and quality control

of ocean color data. This program is online at

http://seadas.gsfc.nasa.gov/.

To find the presence of biomass necessary for this research we

use the Chloropyll-a algorithm. This parameter is responsible for

providing the concentration of pigment, which implies the

presence of biomass.