Utilizing PBL Height Data from Multiple Observing Systems in the GEOS System (I): Assimilation Framework

Abstract

In this study, a strategy and framework are developed to build a global Planetary Boundary Layer (PBL) height (PBLH) analysis and monitoring capability from multiple observing systems in the NASA Global Earth Observing System (GEOS) data assimilation system. To facilitate this effort, PBLH are derived from radiosonde and Global Navigation Satellite System Radio Occultation (GNSS-RO) refractivity data. As PBLH can be sensitive to potentially disparate observables and retrieval algorithms, new model PBLH definitions consistent with each observation type are added to the forecast model for the calculation of first guess departures from observations (OmF). These model definitions are augmented to the control variable vector, interacting with other control variables through flow-dependent ensemble background error covariance component. Moreover, to capture capping inversions, methods are explored using PBLH data to improve background error covariance through inflation of ensemble spread and adjustment of vertical localization length scale for virtual temperature and relative humidity variables. Experiments are conducted to assess the separate and combined impacts of these methods and the correlation relationships between PBLH and other control variables in the background error covariance. Preliminary results show that these changes are beneficial to the assimilation of other observations to improve the PBL thermodynamic structure.