[gradsusr] Multiple accumulation periods

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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