2005) or group of physical parameterizations ( Jankov et al. 1995) with little evidence that significant improvements in objective skill measures can be obtained in deterministic forecasts by adjustments to initial conditions ( Gallus and Segal 2001) or through the use of a particular model ( McBride and Ebert 2000 Gallus et al. Warm season rainfall forecasting is a difficult challenge (e.g., Olson et al. Surprisingly, however, the overall areal coverage and rain volume within the domain may be more influenced by the dynamic core choice than the physics used. As might be expected for warm season rainfall, the finescale structure of rainfall forecasts is more affected by the physics used than the dynamic core used.
#Olson schwartz update#
Sensitivity to initial conditions (Eta versus the Rapid Update Cycle with an accompanying small change in grid spacing) is generally less substantial than the sensitivity to changes in dynamic core or physics, except in the first 6–12 h of the forecast when it is comparable. For heavier rainfall, the opposite is true with a greater sensitivity occurring when NCEP physics is used. For light rainfall, the WRF model using NCAR physics is much more sensitive to a change in dynamic core than the WRF model using NCEP physics. For light rainfall, the spread in the rainfall forecasts when physics are changed under the ARW core is actually less at most times than when the dynamic core is changed while NCAR physics are used. Sensitivity to a change in physics when the ARW core is used is noticeably less. The greatest sensitivity in general is associated with a change in physics packages when the NMM core is used.
Simulations suggest that the sensitivity of the model to changes in physics is a function of which the dynamic core is used, and the sensitivity to the dynamic core is a function of the physics used. Other physical schemes were the same (e.g., the Noah land surface model, Ferrier et al. One physics package (denoted NCEP) used the Betts–Miller–Janjic convective scheme with the Mellor–Yamada–Janjic planetary boundary layer (PBL) scheme and GFDL radiation package the other package (denoted NCAR) used the Kain–Fritsch convective scheme with the Yonsei University PBL scheme and the Dudhia rapid radiative transfer model radiation. The Advanced Research WRF (ARW) and the nonhydrostatic mesoscale model (NMM) dynamic cores were used. Most simulations were run with 8-km grid spacing.
#Olson schwartz series#
A series of simulations for 15 events occurring during August 2002 were performed using the Weather Research and Forecasting (WRF) model over a domain encompassing most of the central United States to compare the sensitivity of warm season rainfall forecasts with changes in model physics, dynamics, and initial conditions.
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