1. Download data
There are two ways to download the data, one is to select the target image individually from the homepage and download it, and the other is to specify the conditions on the command line and download them all at once.
To download individual images, click the thumbnail image to be downloaded from the image search screen, right-click the displayed image, and save it. If you need individual image data, you can download the data in netCDF format by clicking the download icon next to the image.
Figure 1. Daily composite Chlorophyll-a concentration observed by SGLI
Please refer to the link below for the sample code when you specify the conditions and download the data in a batch.
＜For Python users＞
＜Jupiter notebook users ＞
2. Data analysis
The downloaded nedCDF format data can be analyzed by preparing an environment that supports reading netCDF.
Here, we will show you the procedure for data visualization and time series data analysis using Python, which is one of the programming languages.
Other software that handles netCDF format data includes SeaDAS, a water area remote sensing software developed by NASA, R, a statistical analysis software, QGIS, a geographic information system, and Windows Image Manager (WIM) from Wimsoft.
The analyzed data is processed and utilized in various shapes according to the purpose. Here, we will introduce an example of the use of artificial satellite remote sensing in the evaluation of eutrophication status within the framework of NOWPAP.
Eutrophication is a phenomenon in which water bodies such as the sea, lakes, and rivers shift from an oligotrophic state to a eutrophication state. In general, it acts to reduce biodiversity. Eutrophication is becoming widely recognized as a pollution and environmental problem, as it causes secondary phenomena such as red tides and blue tides in extreme cases. Therefore, NOWPAP is developing the NOWPAP Eutrophication Assessment Tool (NEAT), a tool for preliminary evaluation of eutrophication, using time-series data of chlorophyll a concentration obtained by artificial satellite remote sensing.
NEAT was developed by Terauchi et al. (2018) as a project of NOWPAP’s Special Monitoring and Coastal Environment Assessment Regional Activity Center (CEARAC), and is used to monitor the eutrophication status of the NOWPAP sea area.
Figure 2. Preliminary evaluation of eutrophication status in NOWPAP sea area by NEAT
In the evaluation of enrichment by NEAT, the average value for the last 3 years in the evaluation target period is obtained from the monthly average chlorophyll a concentration obtained by artificial satellite remote sensing, and the standard value is applied to this, and the sea area to be evaluated is high chlorophyll a. Divide into two areas, one is a concentrated sea area and the other is a low chlorophyll a concentration sea area. The reference value is 5 mg -3, which is the moderate lower limit indicated by Bricker et al. (2003), which was discussed among researchers in NOWPAP member countries. Next, from the monthly average data of the evaluation target period, the annual chlorophyll a maximum value for each year is calculated, and the increasing / decreasing tendency of that value is judged by a statistical method, and it is divided into three categories: increasing tendency, decreasing tendency, and no increase / decrease. To do. Finally, the target sea area is classified into 6 types by combining the results of the chlorophyll a concentration level (high, low) and the increasing / decreasing tendency (increasing tendency, decreasing tendency, no increase / decrease).
Figure 2. Six types of eutrophication status using chlorophyll a concentration
CEARAC regularly holds expert meetings for eutrophication assessment to further improve NEAT. In addition, NEAT is expected to be used by the United Nations Environment Program as a tool for monitoring the achievement status of the Sustainable Development Goals “SDGs” 14 “Let’s protect the abundance of the sea” of the United Nations Environment Program. I will.
The time-series chlorophyll a concentration data used in NEAT is based on the comparison and verification work of field observation data and multiple sea-color remote sensing sensors under the work of promoting the Northwest Pacific Ocean Action Plan activity of the Ministry of the Environment. It is tuned and created according to the characteristics. Please refer to this page for the activities to promote the Northwest Pacific Ocean Action Plan.
4．Introduction of Northwest Pacific Area Sea Action Plan Activity Promotion Business
This project will promote the Northwest Pacific Regional Sea Action Plan (NOWPAP) by building a joint research system with Nagoya University, Toyama National College of Technology, and Toyama Prefecture, centered on the Japan Sea Environment Cooperation Center (NPEC). Since 2003, it has been implemented as a project commissioned by the Ministry of the Environment.
In order to clarify the usefulness of remote sensing as an environmental monitoring method, NPEC is verifying existing algorithms and new algorithms using Toyama Bay as a model sea area. For this reason, we are conducting surveys to collect observation data by satellite and obtain sheet loose data. Furthermore, we are trying to understand the actual condition of the relationship between the behavior of phytoplankton and water quality in Toyama Bay, focusing on the nutrient concentration. Based on the results of these surveys, we aim to show NOW PAP-related countries (China, South Korea, Russia) the usefulness of remote sensing as an environmental monitoring method.
Figure 1. Toyama Bay project conceptual diagram
4.2.Survey points and observation items
In this project, at the observation points shown in Fig. 2, surveys of surface layer (0 m) and subsurface layer (0.5 m, 2 m) are conducted about four times a year.
Figure 2. Observation points in Toyama Bay
At these sites, Suspended Substances (SS), Colored Dissolved Organics (CDOM), Chlorophyll a Concentration (Chl-a), Dissolved Inorganic Phosphorus (DIP), Dissolved Inorganic Nitrogen (DIN), Transparency, We are observing the amount of dissolved oxygen and salinity. Figure 3 shows the data acquisition period and the number of acquired data for each observation item.
Figure 3. Observation items and data acquisition period and number of acquired data in Toyama Bay
* Observation items (0.5 + 2) and 440 indicate values for mixed samples with depths of 0.5 m and 2 m and wavelengths of 440 nm, respectively.
As an example of other data utilization, we will introduce an interview article with users of the Pan-Japan Sea Marine Environment Watch.
“Toward protecting the ever-changing ocean environment”
This is a list of papers using data provided by the Pan-Japan Sea Marine Environment Watch.
Terauchi G, Maúre E R, Yu Z, Wu Z, Kachur V, Lee C and Ishizaka J (2018) Assessment of eutrophication using remotely sensed chlorophyll-a in the Northwest Pacific region Proc. SPIE 10778, Remote Sensing of the Open and Coastal Ocean and Inland Waters, 107780H (24 October 2018); https://doi.org/10.1117/12.2324641
Motoki Terauchi, Keio Maeda (2016) Evaluation of eutrophication by satellite remote sensing and current status and issues of seagrass bed mapping in the northwestern Pacific region, Coastal Ocean Studies, 2016-2017, Vol. 54, No. 1, p. 29-42 , Release date 2020/02/12 , Online ISSN 2434-4036, Print ISSN 1342-2758, https://doi.org/10.32142/engankaiyo.54.1_29
Terauchi G, Tsujimoto R, Ishizaka J and Nakata H (2014) Influence of river dicharge on seasonal and interannual variability of remotely sensed chlorophyll-a concentration in Toyama Bay, the Sea of Japan La mer 52 (3)
Terauchi G, Tsujimoto R, Ishizaka J and Nakata H (2014) Preliminary assessment of eutrophication by remotely sensed chlorophyll-a in Toyama Bay, the Sea of Japan Journal of Oceanography, 70(2), pp175-184. doi: 10.1007/s10872-014-0222-z寺内ら 2016
Motoki Terauchi, Yuji Ishizaka (2007) Monitoring eutrophication in Toyama Bay using satellite data, Coastal Ocean Studies, Vol. 45, No. 1, p. 43-49, https://doi.org/10.32142/ engankaiyo.45.1_43 Machiko Yamada, Mayuko Otsubo, Kunihisa Tada, Yoshikatsu Nakano, Ken Matsubara, Naoki Iida, Yoshinari Endo, Shigeru Kadoya (2016) Species composition of the diatom Skeletonema in five waters of Japan from the subtropical zone to the subtropical zone, Japan Journal of the Japanese Society of Fisheries Science , https://doi.org/10.2331/suisan.16-00040