# Comparing Dual-Doppler Radar Analysis to WRF Output

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.

#### twhittock3

##### New member
Hello WRF community,

I have a dual-doppler radar analysis of the landfall of Hurricane Florence. It contains a grid of 200x175 points, and the X and Y coordinates are distances in meters from one of the two radar towers. The grid has a resolution of 1km, i.e. there is a radar observation recorded every 1000m. The radar analysis files are in netCDF format, and they do not contain latitude and longitude, so I am unsure how to plot it on a map with coastlines and state borders. The (X,Y) point (0,0) is the only known latitude and longitude (the same as one of the radar stations: 33.9892, -78.4291). I would like to use this radar analysis to help evaluate/validate 10m wind speeds that I get from a WRF run.

Here is my question/problem: Is there a way that I could convert a 200x175 grid of distances (dx,dy) reported from one reference latitude and longitude, into a grid of latitude and longitude points that I can then compare with my WRF output? Alternatively, is there a relatively easy way to convert WRF output into a grid of distances, in meters, from one reference latitude and longitude, that I can then use to compare with my radar analysis?

Thank you,
Ted

Hi Ted,
Unfortunately I'm not aware of any methods for doing this, but hopefully someone from the community will have some ideas.

I think knowing only the latitude and longitude of the (0,0) point, along with the fact that all points are spaced 1 km apart (along two orthogonal axes?) may not be enough information to determine the latitude and longitude of every point. For example, in the figures below, the points are at 1 km spacing and both grids have a corner point located at (0,0).

Do you know the orientation of the axes of the grid, or something else that would allow for an unambiguous description of the grid?

Positive values on the Y-axis correspond to North and positive values on the X-axis correspond to East. There are also negative Y and X values that correspond to South and West, respectively. In other words, the 0,0 point represents the location of the radar station, and there are positive coordinates N/E of the radar and negative coordinates to the W/S of it. I will attach an image of one of my plots for a visual representation of it. I want to associate the grid of the attached plot with its corresponding latitude and longitude grid, and once I have done that, I can plot it on a map with coastlines and state borders.

The axes are orthogonal as you assumed; hopefully the x and y-axis labels on the attached plot help make it clear. The radar station, known as KLTX, is marked on the map with a gray dot, and its coordinates are labeled.

Thank you,
Ted