Characteristics of water vapor structure of two cold front systems over central U.S.: High—resolution numerical simulations

It has been recognized that the details of water vapor mixing ratio profiles in the mixed layer and lower troposphere are crucial for generating or maintaining mesoscale convective system. However, due to the lack of high temporal and spatial resolution water vapor measurement, understanding of the characteristics of water vapor structures for mesoscale severe weather systems remains a challenging problem.

This presentation illustrates the characteristics of water vapor structure of two cold front systems over central U.S. through 1) the observations obtained by the NASA/GSFC Raman Lidar instrument in very high temporal (every 10minutes) and vertical (~100 m) resolution; and 2) the numerical simulations from the PSU/NCAR Mesoscale model version 5 (MM5) in high-resolution (~1.3km horizontally). Preliminary study shows that the MM5 numerical simulations could reproduce some of the Raman Lidar observed water vapor features for the cold front systems in lower troposphere, indicating that it is reasonable to use the numerical results to diagnose the characteristics of water vapor structure in cold front systems. Then, a series of studies are conducted to investigate the evolution of water vapor structures during cold front systems. In addition, as the numerical simulations produce the three-dimensional structure of thermodynamic field variables associated with water vapor fields, the mechanism of water vapor variations during the cold front systems is also investigated. Detailed results will be presented in the conference.