STUDY ON SOUNDING BALLOON DRIFTING AND ITS IMPACT ON NUMERICAL PREDICTIONS

To investigate the impact of height-depending sounding balloon's drifting on numerical prediction and extract to the full utility of soundings, a positioning scheme is designed to locate the balloon's position at every pressure level, based on sounding principles. Data used before and after the position correcting are assimilated using the 3D-VAR system separately, with the assimilations applied as the initial field of the WRF model for predictions, which then undergo analysis for comparison. The main results are as follows: (1) the distance a sounding balloon drifts during operation is a lot longer than that is accepted as a horizontal resolution by present numerical models; (2) the positioning scheme presented for sounding balloons is basically applicable to a resolution of 10km×10km; (3) on the whole, the position correction leads to the fact that the resulting analytic increment field is one order of magnitude smaller than the original; (4) analysis of the model predictions shows that soundings, when positioned, would improve predictions. Moreover, the accurate position correction of leveled soundings will better the output of high-resolution numerical models to some extent but further case studies are needed.