A Modular Retrieval Testbed for Microwave Sounders: Examples from AMSU/MHS, ATMS and HAMSR

Microwave sounders are used since several decades to measure the atmospheric state of the Earth’s atmosphere. The main instrument specifics and spectral range are hereby often similar. However, the accuracy of retrieved parameters like temperature and water vapor is often hard to compare, because retrievals are very sensitive to error sources, technical variations of instruments or variations in the retrieval components. This makes the inter-comparisons of retrieved products often difficult.

We are therefore developing a modular retrieval system for microwave sounders.  The code will have the capability to use different modular components with respect to solving algorithms, background information and radiative transfer codes. It will help to easily compare different kinds of retrieval components within the same retrieval environment and evaluate the impact of background information or radiative transfer algorithms on the solution. It makes it therefore easier to understand the impacts of the different components on the results.

The intention is to use it on various remote sensing systems with similar specifications from current missions and compare the results by using a variety of modular components. We will show scenes from space from the Advanced Technology Microwave Sounder (ATMS) on Suomi NPP, the Advanced Microwave Sounder (AMSU-A and MHS) on NOAA-18 and compare it with airborne HAMSR data. We will show that the selection of the radiative transfer code or the background information can have a strong impact on the comparison of retrievals from these instruments, even if all other components are kept similar.