Degree Heating Weeks (DHW) Estimation using Python Programming and Sea Surface Temperature Data from The Google Earth Engine Dataset as Coral Bleaching Analysis Tools
Hariyanto Triwibowo(a), Joko Prihantono(b*), Nasir Sudirman(b), Agus Sufyan(b), Eva Mustikasari(b)

a) Research Center for Oceanography, National Research and Innovation Agency (BRIN), Jakarta 14430, Indonesia
b) Research Center for Conservation of Marine and Inland Water Resources, National Research and Innovation Agency (BRIN), Cibinong 16911, Indonesia
*jk.prihantono[at]gmail.com

Abstract

National Oceanic and Atmospheric Administration (NOAA) use the Degree Heating Weeks (DHW) method as a coral bleaching alert worldwide. However, their DHW time series data is only provided in the specified virtual stations and cannot be moved as desired. In this study, DHW calculations were performed using the Python programming language and sea surface temperature (SST) data available in Google Earth Engine (GEE) datasets such as HyCom, MODIS-Aqua, NOAA Pathfinder v5.3, and NOAA OISST v2.1. This Python code allows users to calculate DHW with the desired time range and the coordinate location. Thus, the analysis and early warning of coral bleaching can be done cheaply at that location. The results show that Python code can extract the SST from the GEE dataset according to the user^s input. Then, it calculates and shows the graph of DHW showing coral bleaching alert levels. The SST data from HyCom and NOAA OISST v2.1 are preferred because they have long and continuous data ranges. Unfortunately, HyCom data was available in the GEE dataset until 8 May 2023. At the same time, MODIS-Aqua has blank data at several measurements, and the data availability starts from 2002. In the other hand, The NOAA Pathfinder v5.3 data shows unsatisfactory results because the obtained data shows several unrealistic values and blank data. Therefore, in this study, NOAA OISST v2.1 is the recommended SST data for calculating DHW. However, this program is still in development, so improvements are required to enhance its capabilities. This program will help users concerned with coral research and monitoring.

Keywords: coral bleaching, degree heating weeks, python, google earth engine

Topic: Ocean Remote Sensing and Marine Technology