Rotation of Coordinates Based on CORDEX Domains
If you're dealing with multiple CORDEX NetCDF files and need to extract data from them, there are two main approaches. These files typically contain latitude and longitude as two-dimensional variables (lat/lon), as well as rotated latitude and longitude as one-dimensional variables (rlat/rlon).
The first method involves locating the appropriate cell in the two-dimensional variables (lat/lon) using your latitude and longitude values, then finding the corresponding grid number. Alternatively, you can utilize the one-dimensional variables (rlat/rlon) to access data from the main variables such as precipitation (pr), maximum temperature (tasmax), and temperature (tas). However, if you're dealing with non-rotated coordinates (usually normal format is non-rotated), this tool can assist in converting them to rotated coordinates based on CORDEX domains. Once converted, you can use the rotated coordinates to determine cell numbers using the rlat/rlon variable in your file.
Automation of this process is possible using tools like Open Nc File and CORDEX Data Extractor eliminating the need for manual intervention or conversion steps. These tools use Unidata Java NetCDF Library to apply projection and extraction.
Our tool simplifies the conversion between non-rotated and rotated coordinates, with the rotation pivot based on CORDEX domains (adjustable as needed). Extracting data from CORDEX NetCDF files is straightforward: convert your regular coordinates to rotated coordinates using our tool, then utilize the rotated coordinates and rlat/rlon variables in your file to extract the desired data.
To validate the accuracy of our tool, you can use the Top Left Corner (TLC) coordinates of each domain in CORDEX Domains and perform conversions between non-rotated and rotated coordinates to ensure correctness.
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