Repository collecting and organizing environmental data sources for Japan.
Here, we have downloaded and processed the data available through the site made available by the Japanese National Institute for Environmental Studies (NIES) (https://tenbou.nies.go.jp/download/).
More specifically, we have downloaded the Air Pollution Monitoring data for a total of 2039 stations located around the whole country (represented as red dots in the map below):
Information for the exact location of each station (latitude, longitude and altitude) and the environmental variables available can be found in the table in /data/air_pollution/stations/doc/stations_info.csv
Since the repository includes data for over 2000 stations, the measured variables in each of them are rather heterogeneous. The data is provided in hourly format by the Japanese NIES, and the processed files available in this repository provide the data with a daily frequency, so an aggregation method has been used. The following table summarizes the selected variables, their units, and the aggregation method used to summarize them.
| Variable | Name | Units | Aggregation Method |
|---|---|---|---|
| SO2 | Sulfur Dioxide | ppm | Daily Mean |
| NO | Nitric Oxide | ppm | Daily Mean |
| NO2 | Nitrogen Dioxide | ppm | Daily Mean |
| NOX | Nitrogen Oxides | ppm | Daily Mean |
| CO | Carbon Monoxide | ppm | Daily Mean |
| OX | Photochemical Oxidants | ppm | Daily Mean |
| NMHC | Non-methane Hydrocarbons | ppmC | Daily Mean |
| CH4 | Methane | ppmC | Daily Mean |
| THC | Total Hydrocarbons | ppmC | Daily Mean |
| SPM | Suspended Particulate Matter (<10µm) | mg/m³ | Daily Mean |
| PM2.5 | Particulate matter (<2.5µm) | µg/m³ | Daily Mean |
| TEMP | Temperature | °C | Daily Min, Mean and Max |
| HUM | Relative Humidity | % | Daily Min, Mean and Max |
| RAIN | Total Precipitation | mm | Daily Sum |
Daily data for each station and its measured variables from 2011-01-01 to 2018-12-31 can be accessed in the data/air_pollution/stations/clean folder, classified in subfolders according to the prefecture where they are located.
Averaged daily data for all stations within each municipality in Japan during the same period can be found in the data/air_pollution/municipalities folder, with the first 2 digits of each CSV file indicating the prefecture code and the last 3 digits indicating the municipal code.
Estimates of the daily data for each prefecture have been estimated by averaging over the municipal averages in each prefecture.
At this point, three different methods have been used to compute the averages, weighing the municipalities differently according to diverse criteria:
-
Area-based weighted averages: These averages are completely population-naïve and try to better estimate the overall values for each variable across the whole area of the prefecture, wheighing high and low population density areas exactly the same. The time-series for these can be found in
data/air_pollution/prefectures/area_weighted. -
Population-weighted averages: These averages are computed trying to estimate the values of each variable that represent the most accurate exposure of the population of each prefecture to each pollutant/meteorological variable. For this purpose, the values for each variable have been averaged weighing every municipal term according to their population share in the prefecture. The time-series for these can be found in
data/air_pollution/prefectures/population_weighted. -
Infant population-weighted averages: Following the same principal as the previous averages, these include the daily prefecture-level estimates of each measured variable based on the share of children under 5 years old in each municipal term. The time-series for these can be found in
data/air_pollution/prefectures/under_5_weighted.
The following figure shows the ratio of population covered by the stations in each prefecture (as a ratio of the people living in municipalities with at least one monitoring station):
