Retrieval of three-dimensional wind and thermodynamic fields from single-Doppler observations measured during Phoenix II

Retrieval of the unobserved meteorological fields from a single-Doppler radar has recently received considerable attention as the new U.S. weather radar network, NEXRAD, is being installed. One of the promising techniques is the adjoint data assimilation method described in Sun et al. (1991. This technique attempts to determine the unobserved fields by minimizing the difference between single-Doppler observations and the predictions from a dynamic model. We give a brief description of the model and the cost function. In this paper, the applicability of this technique is examined with a gust front case observed in the Phoenix II experiment of 1984. It is shown that the boundary layer flow can be accurately retrieved from observations of the radial velocity alone when the wind behind the front is well observed. Reflectivity observations are required to obtain a satisfactory retrieval when the post-gust front wind is poorly observed.