By Clarisse Reyna
Geovis Course Assignment, SA8905, Fall 2015 (Rinner)
This is a time series map showing interpolated temperature change. Mount Pinatubo is located in the island of Luzon, Philippines. It erupted in 1991, which marked the second largest volcanic eruption in the 20th century. This caused a cooling effect as it released significant amounts of volcanic gases, aerosols and ash that increases albedo. This means that there is an increase in solar radiation being reflected, which decreases the amount of solar radiation reaching the troposphere and the surface. Since there is less solar radiation at the troposphere and the surface, it causes a temperature decrease. This is exactly what took place when Mount Pinatubo erupted in 1991. After the eruption, there was an observed surface cooling that took place in the Northern Hemisphere of around 0.5 to 0.6 degrees Celsius (Self et al. 1999).
In this time series map, interpolated temperatures in the Philippines from 1988 to 1995 is presented. What you should be able to see is that as time passes after the eruption (1991), there is a significant increase in blue areas which indicate lower temperatures. Originally, the years included would have been from 1985 to 1995. However, there are unusually low temperatures in 1987. In fact, the lowest ever recorded temperature in Manila was on February 4, 1987, with a temperature of 15.1 degrees Celsius. As you can see in the picture below, 1987 has large blue areas, indicating low temperatures. This may cause confusion when viewing the final time series visualization, so it was omitted from the final geovisualization project.
The purpose of including temperatures before the eruption in 1991 is so that the viewer is able to see temperature trends before the cooling occurred. This allows viewers to compare temperature trends before the eruption to temperature trends after the eruption. The years included went up to 1995 because this was the last average temperature where it shows decreasing temperatures from 1991 in most of the cities.
The temperature data in this time series geovisualization were taken from a website called Weather Spark. The data taken from this source was yearly temperature averages from 1988 to 1995 in the Philippine cities of Aparri, Batangas, Bohol, Catarman, Coron, Manila, Davao, Lapu Lapu, Pasig, El Nido, Legazpi, and Pagudpud. Temperature data for the city of Boracay was not available so the province of Malay was used in place of it. Another province used was Bulacan. These areas are very spread apart in the Philippines. Therefore this gives a more accurate representation of temperature patterns during interpolation since the data points are spread apart and covers each part of the country. Lastly, the Philippine boundary shapefile was taken from a website called PhilGIS.
The technology used for this time series visualization was Time Slider, which is available in ArcMap (in versions ArcGIS 10.0 and up). For each year, the data taken from Weather Spark for each city or province was interpolated using the Inverse Distance Weighted method. Therefore, a raster was created for every year. Since there are eight years that are being included in this visualization, eight rasters were created. After creating an interpolation raster for each year, a raster catalog was created, and each of these rasters were added onto the raster catalog. After the rasters were added, time was enabled on the raster catalog layer.
When time is enabled on a layer, ArcMap allows you to use the Time Slider tool to create the time series visualization. This time slider tool allows you to preview what the time series visualization will look like. You can then export the time series visualization to an .avi file by clicking on the icon circled in red in the picture below.
References
Country Boundary. (2013). In PhilGIS. Retrieved from http://philgis.org/freegisdata.htm
Historical Weather. In WeatherSpark Beta. Retrieved from https://weatherspark.com/
Self, S., Zhao, J., Holasek, R., Torres, R., & King, A. (1999). The Atmospheric Impact of the 1991 Mount Pinatubo Eruption. U.S. Geological Survey.