Intensive Soundings at Santa Cruz

Since Tuesday and continuing through Sunday, a crew of US and Costa Rican scientists and students is logging long days launching radiosondes at Santa Cruz every two hours between 6 am and 6 pm.  Our interest in performing these high frequency launches is to capture the daytime evolution of the atmospheric thermodynamic and wind profiles over land.  We are especially interested in assessing the interplay between the land surface and deep convection, namely how the fluxes of energy and water from the land surface impact the development of convection.  There are potentially competing processes affecting how land surface conditions, as reflected in, e.g., the partitioning between latent and sensible heat fluxes, may impact convection.  On the one hand, increasing latent heat flux (evapotranspiration) moistens the boundary layer and lowers the lifting condensation level, so parcels from the surface reach saturation sooner.  On the other hand, increasing sensible heat flux invigorates boundary layer growth and deepens the boundary layer toward the level of free convection, which may favor convective initiation.  Of course, it is also necessary to consider the meso- to large-scale environment in which such land surface interactions occur, as the atmospheric conditions above the boundary layer impact development (e.g., through entrainment).  Below is the sequence of skew-T diagrams for Wednesday September 4^th.  Note the evolution of the near surface mixed layer and the moistening in the mid-troposphere over course of the day.  Our high frequency sounding measurements are complemented by GPS column water vapor and surface meteorological measurements at various sites near Santa Cruz, as well as flux tower measurements of latent and sensible heat near Filadelfia.