Review of Methodology in Algorithm Theoretical Basis Document: MSU/AMSU Radiance FCDR Derived From Integrated Microwave Inter- Calibration Approach Chabitha Devaraj, Ph.D. Assistant Professor Electrical Engineering and Computer Science Department South Dakota State University

Review of methodology: ATBD Summary The ATBD presents a methodology of SNO inter-calibration to create the radiance Fundamental Climate Data Record (FCDR), using the Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit-A (AMSU-A) radiances. It also demonstrates the accuracy of the method using three validation datasets: Pre-launch calibrated MSU/AMSU radiances, GPS RO data and Reanalysis data (NCEP-CFSR and NASA-MERRA). A detailed Error Budget analysis of the final calibrated radiances is presented.

Review of methodology: Method Clarity The developed methodology is written clearly in the ATBD. The logical flow is good and presents sufficient information to get the big picture and refers to the supporting peer reviewed publications for details, thus making the document reader friendly. The color coded illustrations (e.g. Flowchart highlighting differences between MSU and AMSU processing) make it very easy to follow. Appropriate reasoning is provided for the selection of validation dataset.

Review of methodology: Method Clarity Few minor suggestions for document completeness: – Chapter 1: Give satellite altitude along with horizontal resolution. Also both nadir and limb. – Table 2.4 AMSU-A ground IFOV at nadir 45 km – Provide a brief Product level description at the end of Section 2. – Page 26 “μ ,  ” – Figure 3.10 GOM – Chapter 4: Consistent “GPS RO” or “GPSRO” dataset – Matchups are spelled as “Mathchups” at several places in the document.

Review of methodology: Method Utility and Reproducibility The approach appears to be viable and technically correct. The results are well summarized to confirm the advantages of the SNO calibration algorithm for inter-calibration. Detailed description of the various steps involved in the method is presented in the supporting references to enable the user to be able to reproduce the results from this methodology.