One important advance in COSMIC, compared with previous missions, is the development and implementation of the open loop tracking technique. The open look tracking technique allows COSMIC GPS radio occultation (RO) soundings to penetrate the lower troposphere, and to provide an estimate of atmospheric boundary layer (ABL) height. The measurements and analysis of ABL height globally will provide valuable information that is important to weather forecasting and climate process studies.

Through the analysis of COSMIC GPS RO soundings, we found significant variations of ABL heights in different geographical regions. For a given geographical region, there are also significant changes in ABL height and intensity, depending on synoptic weather systems. We also found that global analyses tend to possess larger errors (in terms of refractivity) at the top of the ABL, when there are sharply defined ABL. In this study, we will examine the cases with and without strong ABL gradients. We will also perform numerical simulations using the Weather Research and Forecasting (WRF) model, and to examine the ability of the model in capturing ABL structures as detected by COSMIC GPS RO soundings. We will study how the simulation is affected by model initialization, vertical and horizontal resolutions, and model planetary boundary layer (PBL) parameterization.