Summary

Observations and numerical modeling studies in the past suggested that land use modulates formation and development of convective and orographic clouds in northern Costa Rica. During the dry season of March, satellite observations in this region show suppression of cumulus cloud formation over deforested areas. Orographic clouds show sensitivity to lowland deforestation in numerical modeling experiments. Thus lowland deforestation in this region has serious implications since harvesting of water from the orographic clouds by vegetation is a major source of dry season moisture for the ecologically sensitive tropical montane cloud forests.

A ground observation network acquiring surface meteorological variables, soil moisture and visual observations of orographic cloud banks has been operating in the northern Costa Rican region to support NASA and NSF funded research on impact of land use change on cloud formation. For a three week period in March of 2003, Land Use Cloud Interaction Experiment (LUCIE) was conducted during which coordinated high temporal resolution radiosonde observations were collected over paired sites using mobile GLASS maintained by NCAR Atmospheric Technology Division. The main objectives of the experiment was to compare the boundary layer development over forested and deforested areas, characterize the spatial variation of atmospheric thermodynamic profile ranging from the Caribbean to Pacific cost and aid in the initialization and validation of the numerical model simulations. Initial analysis of the radiosonde observations reveals systematic differences in Lifting Condensation Level (LCL) between forested and deforested sites. Numerical simulations utilizing radiosonde observation collected during LUCIE show differences in orographic cloud formation in response to lowland deforestation. The use of LUCIE data for developing remote sensing techniques to aid in the mapping of cloud forest ecosystems will also be disc