The Impact of Verification Area Design on Tropical Cyclone Targeted Observations Based on the CNOP Method |
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Authors: | ZHOU Feifan and MU Mu |
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Institution: | Laboratory of Cloud-Precipitation Physics and Severe Storms, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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Abstract: | This study investigated the impact of different verification-area designs on
the sensitive areas identified using the conditional nonlinear optimal
perturbation (CNOP) method for tropical cyclone targeted observations. The
sensitive areas identified using the first singular vector (FSV) method,
which is the linear approximation of CNOP, were also investigated for
comparison. By analyzing the validity of the sensitive areas, the proper
design of a verification area was developed.
Tropical cyclone Rananim, which occurred in August 2004 in the northwest
Pacific Ocean, was studied. Two sets of verification areas were designed;
one changed position, and the other changed both size and position. The CNOP
and its identified sensitive areas were found to be less sensitive to small
variations of the verification areas than those of the FSV and its sensitive
areas. With larger variations of the verification area, the CNOP and the FSV
as well as their identified sensitive areas changed substantially. In terms
of reducing forecast errors in the verification area, the CNOP-identified
sensitive areas were more beneficial than those identified using FSV. The
design of the verification area is important for cyclone prediction. The
verification area should be designed with a proper size according to the
possible locations of the cyclone obtained from the ensemble forecast
results. In addition, the development trend of the cyclone analyzed from its
dynamic mechanisms was another reference. When the general position of the
verification area was determined, a small variation in size or position had
little influence on the results of CNOP. |
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Keywords: | sensitive area verification area CNOP FSV |
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