Search

A dryline and misocyclones have been simulated in a cloud-resolving model by applying specified initial and time-dependent lateral boundary conditions obtained from analyses of the 22 May 2002 IHOP dataset. The initial and lateral boundary conditions were obtained from a combination of the time-spaced Lagrangian analyses for temperature and moisture with horizontal velocities from multiple-Doppler wind syntheses. The simulated dryline, horizontal dry-convective rolls (HCRs) and open cells (OCCs), misocyclones, and cumulus clouds are similar to the corresponding observed features. The misocyclones move northward at nearly the mean boundary layer (BL) wind speed, rotate dryline gradients owing to their circulations, and move the local dryline eastward via their passage. Cumuli develop along a secondary dryline, along HCR and OCC segments between the primary and secondary drylines, along HCR and OCC segments that have moved over the dryline, and within the dryline updraft. After the initial shearing instability develops, misocyclogenesis proceeds from tilting and stretching of vorticity by the persistent secondary dryline circulation. The resulting misocyclone evolution is discussed [ABSTRACT FROM AUTHOR]

A new Lagrangian analysis technique is developed to assimilate in situ boundary layer measurements using multi-Doppler-derived wind fields, providing output fields of water vapor mixing ratio, potential temperature, and virtual potential temperature from which the lifting condensation level (LCL) and relative humidity (RH) fields are derived. The Lagrangian analysis employs a continuity principle to bidirectionally distribute observed values of conservative variables with the 3D, evolving boundary layer airflow, followed by temporal and spatial interpolation to an analysis grid. Cloud is inferred at any grid point whose height z > zLCL or equivalently where RH ≥ 100%. Lagrangian analysis of the cumulus field is placed in the context of gridded analyses of visible satellite imagery and photogrammetric cloud-base area analyses. Brief illustrative examples of boundary layer morphology derived with the Lagrangian analysis are presented based on data collected during the International H2O Project (IHOP): 1) a dryline on 22 May 2002; 2) a cold-frontal–dryline “triple point” intersection on 24 May 2002. The Lagrangian analysis preserves the sharp thermal gradients across the cold front and drylines and reveals the presence of undulations and plumes of water vapor mixing ratio and virtual potential temperature associated with deep penetrative updraft cells and convective roll circulations. Derived cloud fields are consistent with satellite-inferred cloud cover and cloud-base locations. [ABSTRACT FROM AUTHOR]