Improving Boundary Layer Profiling by Augmenting Space-Based Measurements with Ground-Based Interferometers

The National Academy of Science’s Earth Science Decadal Survey in 2017 made improving observations of the planetary boundary layer a priority. The current operational observing system utilizes thermodynamic soundings derived from radiosondes, aircraft observations, and space-based instruments making measurements in the infrared and microwave. However, space-based sounders lack the necessary vertical resolution to observe and predict important weather phenomena, especially in the boundary layer. Furthermore, infrared sounding of the boundary layer from space is restricted by the presence of clouds. Microwave sensors are able to profile below the cloud layer, but have even worse vertical resolution than the infrared sounders. Radiosondes are widely considered the gold standard in providing observations of profiles of temperature and moisture, but are launched every 12 h from locations hundreds of kilometers apart – spatial and temporal scales that are also lacking for the goal of improving weather observation and forecasting.

Thermodynamic profiling from ground-based platforms has been used in research capacities for upwards of two decades. The National Research Council has previously suggested the development of a nationwide network of ground-based thermodynamic profilers to supplement space-based sounders and improve observations of the planetary boundary layer. One of the instruments that could potentially be used in a future ground-based network of this type is the Atmospheric Emitted Radiance Interferometer (AERI). AERI measures downwelling radiance at approximately 1 cm^-1 resolution from 520 cm^-1 to 3000 cm^-1. This instrument is very similar to the space-based interferometers, such as the Cross-track Infrared Sounder (CrIS) and the Infrared Atmospheric Sounding Interferometer (IASI), and has been deployed all over the world in a variety of climate regimes. The AERI has proven to be very effective at boundary layer observations, and the current retrieval algorithm, AERIoe, allows for the retrieval of thermodynamic variables up to cloud base. Combined, the ground-based AERI would complement the space-based observing system: AERI would provide high-temporal resolution observations to monitor the rapid transitions in the boundary layer, and the space-based instruments providing observations of the slower evolving middle and upper troposphere.

However, little work has previously been completed on the subject of comparing the information content between space-based and ground-based sensors. This study will assess the information content for the ground-based AERI and space-based CrIS on the NASA Suomi-NPP and the NOAA-20 operational satellites. The goal of this study is to quantify the sensitivity of each instrument to different levels of the troposphere. We will also assess the improvement to the profile given a synergy of the two systems, as compared to using each instrument separately.