[ncl-talk] hovmoller plotting issue using high-resolution data

[Jeremy Berman]

Hello,

I am creating a Hovmoller using data that was computed based off of a WRF simulation (15 km grid, output every 3 hours). The data consists of an ensemble-mean isentropic level of potential vorticity, sensitivity values, and a student's t-test; all as a function of time (12 different forecast hours) and distance along the hovmoller (~2400 km). My NCL script reads in this data, and overlays these three variables on a single plot, as a function of forecast hour and distance --- the resulting plot is attached.

The issue is focused on the shading and how NCL is plotting it. The shading corresponds to the sensitivity values, with positive (negative) values in the warm (cool) colors. However, NCL seems to be doing something weird with interpolating between the data points. For example: there are boxes of high positive sensitivity at 1400 km at 21 h, 1600 km at 24 h, 1800 at 27 h, etc.

Thus my question is: Is there something wrong with how I am plotting the data in NCL? Such as with my resources? I am using Rasterfill for example, which has worked in previous applications, but have tried other ones with the same result. Or is there something inherently wrong with using NCL for this application?

Has anyone experienced this plotting problem before, and have any suggestions? Attached is the .nc file (combined_fields.nc), the main NCL script (hovmoller_clean_pv.ncl), and the outputted image (NCL_hovmoller_335K_PV.png). I am using NCL version 6.1.2.

Thank you for your time and consideration.

Many Thanks,

Jeremy Berman
PhD Graduate Student
University at Albany/SUNY

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