[gradsusr] Multiple accumulation periods
RENTSCHLER, SCOTT A GS-12 USAF ACC 16 WS/WXNM
scott.rentschler.1 at us.af.mil
Tue Mar 13 16:12:23 EDT 2018
All -
I'm generating some post-processed information based off an ensemble. So for example, I might be generating the following parameters:
ASNOW Total Snowfall [prob]:surface:240-246 hour acc fcst:prob >2:probability forecast
ASNOW Total Snowfall [prob]:surface:240-246 hour acc fcst:prob >4:probability forecast
ASNOW Total Snowfall [prob]:surface:234-246 hour acc fcst:prob >4:probability forecast
ASNOW Total Snowfall [prob]:surface:234-246 hour acc fcst:prob >6:probability forecast
ASNOW Total Snowfall [prob]:surface:222-246 hour acc fcst:prob >2:probability forecast
ASNOW Total Snowfall [prob]:surface:222-246 hour acc fcst:prob >6:probability forecast
...and I'm writing these fields in GriB2 format. In this example, I'm generating the data off of the GFS ensemble, writing out the information every 6 hours, with data valid at that forecast hour. So the above records appear in the 246 hour forecast file.
Note that we have a couple of fields then that, when using g2ctl, or even alt_g2ctl, would have identical variable names as they only differ in the accumulation period -
ASNOW Total Snowfall [prob]:surface:240-246 hour acc fcst:prob >2:probability forecast
ASNOW Total Snowfall [prob]:surface:222-246 hour acc fcst:prob >2:probability forecast
ASNOW Total Snowfall [prob]:surface:240-246 hour acc fcst:prob >4:probability forecast
ASNOW Total Snowfall [prob]:surface:234-246 hour acc fcst:prob >4:probability forecast
ASNOW Total Snowfall [prob]:surface:234-246 hour acc fcst:prob >6:probability forecast
ASNOW Total Snowfall [prob]:surface:222-246 hour acc fcst:prob >6:probability forecast
The g2ctl utility outputs the following entries into the control file:
ASNOW2e3GTsfc 0,1,0 a1,2 0,1,29,1 ** surface prob >2 Total Snowfall [prob]
ASNOW4e3GTsfc 0,1,0 a1,4 0,1,29,1 ** surface prob >4 Total Snowfall [prob]
ASNOW6e3GTsfc 0,1,0 a1,6 0,1,29,1 ** surface prob >6 Total Snowfall [prob]
The alt_gt2ctl:
ASNOWdprob_>2dprobability_forecastsfc 0 0 "ASNOW.prob_>2.probability_forecast:surface" * ASNOW.prob_>2.probability_forecast:surface
ASNOWdprob_>4dprobability_forecastsfc 0 0 "ASNOW.prob_>4.probability_forecast:surface" * ASNOW.prob_>4.probability_forecast:surface
ASNOWdprob_>6dprobability_forecastsfc 0 0 "ASNOW.prob_>6.probability_forecast:surface" * ASNOW.prob_>6.probability_forecast:surface
...and alt_g2ctl using the "-short" flag:
v1 0 0 "ASNOW.prob_>2.probability_forecast:surface"
v2 0 0 "ASNOW.prob_>4.probability_forecast:surface"
v3 0 0 "ASNOW.prob_>6.probability_forecast:surface"
My problem is that I'm unsure how to reference the different accumulation periods for the given parameters. If I were to create a template for a 246 hour forecast period, and within the GrADS command line interface, input "set t=42", and try to display one of the above parameters, how do I know which one I'm displaying and how does one switch to a different accumulation period? I'm hoping to avoid creating new files containing subsets of the above data, but at the moment I'm not sure how to work around it. Is there a way to give each accumulation period a unique ID or an appropriate mechanism for identifying differing accumulation periods for a given parameter?
Thanks!
Scott
//Signed//
Scott Rentschler, Meteorologist
Fine Scale / Ensemble Models Team
557th Weather Wing, 16WS/WXN
DS: 271-3331 Comm: (402) 294-3331
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