alias  mars.number = perturbationNumber;
unalias mars.step;

# Old GRIBS do not have forecast forecastMonth set. It is computed from verifyingMonth

meta forecastPeriodFrom evaluate(verifyingMonth/1000) : no_copy;
meta forecastPeriodTo   evaluate(verifyingMonth%1000) : no_copy;
meta forecastPeriod     sprintf("%d-%d",forecastPeriodFrom,forecastPeriodTo) : dump;
alias mars.fcperiod = forecastPeriod;
alias mars.method = methodNumber;
if (class is "od") { alias mars.system = systemNumber; }