During the International H2O Project (IHOP_2002), the airborne water vapor differential absorption lidar (DIAL) LEANDRE 2 was operated in the horizontal-pointing mode from the NRL P-3. Such measurements provided the first ever observations of the horizontal structure of the water vapor field in the quiescent boundary layer and its evolution in the course of the day.

During the 14 June boundary layer evolution (BLE) case of IHOP_2002, the moisture in the planetary boundary layer (PBL) over the Oklahoma panhandle was documented using two DIALs (one pointing horizontally in the PBL and one pointing to the nadir), two aircraft and numerous balloon soundings. The present study focuses on the evolution of the two-dimensional structure of the water vapor mixing ratio in the PBL between 1130 and 1730 UTC. The characteristic scales of moisture variability and their evolution with time are compared with that issued from a realistic Large-Eddy Simulations (designed with the Méso-NH model) from 1500 UTC on.