I am struggling a bit with the timing of my meteorological data. I have to add that this is my first contact with grib, arl and forecast/reanalysis data so maybe I'm asking questions which are obvious for everybody else.
I am working with CFSR forecast (6hr) and analysis data and calculating trajectories. I'm dealing with both forecast and analysis, since not all fields (for example the 10m winds) are available in the analysis.
I don't understand how the timing is set up in the grib and arl files, since depending how I look at the data, I get different answers:
For example in the arl-header under "Greenwich date/time for which data valid" is this the time for which the forecast is valid or is it the time where the forecast was initiated? I.e. which time is used later in the trajectory calculations, the time indicated here or this time + "Forecast"?
Same thing when looking at the grib data with wgrib or grib_ls, which time is shown?
So basically do I need to shift the Forecast data manually by 6hr to compare Forecast and Analysis at the same moment or is that already taken care off automatically?
I am using MeteoInfo to convert from grib2 to arl and as it looks the midnight grib2 data in some cases is identical to the 6am arl data, so I think something is going wrong somewhere and I need to better understand how this timevariable is dealt with.
Thanks for your input on that question,