2018_EJRNL_PP_YUJIE_PAN_1.pdf
Terbatas pustaka bosscha
» ITB
Terbatas pustaka bosscha
» ITB
Assimilation configurations have significant impacts on analysis results and subsequent forecasts. A squall line system
that occurred on 23 April 2007 over southern China was used to investigate the impacts of the data assimilation frequency
of radar data on analyses and forecasts. A three-dimensional variational system was used to assimilate radial velocity data,
and a cloud analysis system was used for reflectivity assimilation with a 2-h assimilation window covering the initial stage of
the squall line. Two operators of radar reflectivity for cloud analyses corresponding to single- and double-moment schemes
were used. In this study, we examined the sensitivity of assimilation frequency using 10-, 20-, 30-, and 60-min assimilation
intervals. The results showed that analysis fields were not consistent with model dynamics and microphysics in general;
thus, model states, including dynamic and microphysical variables, required approximately 20 min to reach a new balance
after data assimilation in all experiments. Moreover, a 20-min data assimilation interval generally produced better forecasts
for both single- and double-moment schemes in terms of equitable threat and bias scores. We conclude that a higher data
assimilation frequency can produce a more intense cold pool and rear inflow jets but does not necessarily lead to a better
forecast.