Study on Adjoint-Based Targeted Observation of Mesoscale Low on Meiyu Front
Targeted observation is such an idea that to reduce the small errors in the initial analysis that induce great errors in the numerical weather forecast by adding observation in the targeted area and so obtain the improvement of the numerical prediction accuracy of a given weather system. Many works associated with this topic have been carrying out, especially by European and USA scientists. The cyclone forming and developing in Pacific and Atlantic Ocean is mainly focused on in their research. It has significant meaning to address the key issues associated with targeted observation of Asian weather systems, together with the feasibility to improve the accuracy of their numerical forecast by using this technology. These weather systems have individual characteristics comparing with that of European and USA.
Study on adjoint-based targeted observation of mesoscale low on Meiyu Front is implemented in this paper. The mesoscale model MM5 and its corresponding tangent linear and adjoint model are used. The scheme of sensitivity analysis based on adjoint method is designed firstly. The linear assumption is verified to remain valid for two days, thus it is proper to use the adjoint-based method for the targeted observation issue of two days numerical forecast of mesoscale low on Meiyu Front. The distributions of sensitivity gradient of different physical fields tend to be consistent. So the targeted observation region decided by this kind of sensitivity analysis will fulfill the requirement of targeted observation. At the same time, it is found that the sensitivity gradient is dominated by the leading vectors. It denotes that it is also proper to decide the targeted observation region by using the leading singular vectors. Following the discussions of these key issues associated with adjoint-based targeted observation of mesoscale low on Meiyu Front, the possibility is verified whether the accuracy of numerical forecast could be improved by this method.
KeywordsTargeted observation adjoint sensitivity analysis mesoscale low meiyu front
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