92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012
Impact of Ensemble Initial Perturbation From Different Cyclings and Rescaling for NCEP GEFS
Hall E (New Orleans Convention Center )
Juhui Ma, NOAA/NWS/NCEP/EMC, Camp Springs, MD; and Y. Zhu and D. Hou

For the medium range weather forecast, the sources of uncertainties are mainly related to the baroclinic instability of the synoptic scale flow. The convective instability is growing much faster and saturated at very early stage with lower energy level. Therefore, appropriate cycling and rescaling for ensemble initial perturbations could select oriented growth mode, filter out part of non-growth modes. In this study, 12 hours cycling and various rescaling factors have been investigated to compare 6 hours cycling based on NCEP global ensemble forecast system (GEFS). The skills of ensemble forecast are compared from various verification methods during August 1st, 2010 to September 31st, 2010 for 500hPa and 1000hPa geopotential height, 850hPa and 2-meter temperature, 10-meter u-component and v-component of wind over the Northern Hemisphere (NH, 20˚-80˚N), the Southern Hemisphere (SH, 20˚-80˚S) and the tropics (TR, 20˚N-20˚S). The further discussion will be followed up by using NCEP standard probabilistic verification package.

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