FAQ
About the Concentration Data >
Q. What is the unit of the gridded concentration data provided by TAP?
A: In the gridded concentration data, the unit is "μg/m³".
Q. How to understand the latitude and longitude coordinates provided in the data?
A. The latitude and longitude coordinates provided in the data are the coordinates of the center in each grid cell.
Q. Why not provide air pollution data for download during the last 60 days?
A. The TAP data is based on the fusion of the data from multiple sources including real-time ground-based observations, near real-time satellite remote sensing data, operational CMAQ model simulations, near real-time meteorological reanalysis data, etc. When any of these data are delayed or missing, the accuracy of the air pollution data products will be affected. To ensure that high quality data products are shared with the community, TAP has established a strict data audit mechanism to ensure that the data products provided for download are produced with complete input data and perfect inversion model, hence the 60-day delay.
Q. How to download the TAP 1-km resolution data?
A. Due to the large data size, the TAP 1-km resolution data were saved and distributed as tiles. After submitted the TAP 1-km data request, an email with a downloading link will be sent when the data are ready. Access the downloading link will receive a zip file with a plain text file named “url.txt” that record the downloading links of all the data files and the coordinates of the centroid of the 1-km grid of each tile. Open the downloading links in your browser will download the data. Downloading tools, i.e. wget, are recommended that allows downloading of all the files in batch. To download one file using wget, enter the following command:
wget --content-disposition <url>
To download multiple data files at once, with a plain-text <url.txt> file with each line containing a data file URL, enter the following command:
wget --content-disposition -i <url.txt>
Q. What is the “tile” of the TAP 1-km resolution data?
The tile is a fishnet grid with grid width and grid length of three degree covering China. A tile includes about 130 thousand 1-km data grids. The location of tile is fixed. The coordinates of the 1-km grid of each tile are distributed together with the data of the corresponding tile.
Q. What is the difference between O3 data version 1 and version 2?
A. The measurement standard of O3 concentration from national air quality monitoring stations changed from under the standard state (273 K, 101.325 kPa) to under the reference state (298.15K, 101.325 kPa) on September 1st, 2018 (HJ 654—2013). Thus, to correctly reveal the temporal trend of O3 pollution, when constructing the near real-time O3 data, we adjusted all the gridded O3 concentration predictions to under the reference state (version 2). We also employed the MERRA-2 meteorology parameters instead of the WRF simulations to describe the meteorological filed more accurately in the version 2 data.
About the Map >
Q. Can TAP draw maps at any spatial scale?
A. TAP supports user-customized drawing ranges, but to ensure the best drawing results, it is recommended that the drawing area has an aspect ratio within the range of 3:1 to 1:3, beyond which it will be automatically adjusted to 3:1 or 1:3.
Q. Can TAP provide spatial distribution maps on daily scale?
A. Yes, please contact the TAP team if you have the specific requests.
Other Questions >
Q. How to cite TAP data?
A: Please refer to INTRODUCTION>How to Cite.
For other questions, please contact the TAP team.