V2.0 Improvements

The v2.0 production algorithm has many improvements over v1.07 in both the Level 1 procedures, which turn the instrument data into calibrated radiance profiles, and Level 2 procedures, which produce the science products from the Level 1 radiance data. The level 1 improvements are primarily in the correction of electronic gain steps and corrections to detector relaxation of the long-wave channels (1-7) for the up scans. These improvements reduce up-down scan differences that were evident in v1.07 to residual levels that are essentially insignificant. The level 2 improvements are primarily to the procedures used to simultaneously retrieve temperature and pressure in the middle stratosphere - where the CO2 populations of interest are in local thermodynamic equilibrium (LTE), and to the procedures used to retrieve temperature for conditions that are not in local thermodynamic equilibrium (nLTE) - primarily involving details of the vibrational temperature model iteration and maintenance of input parameters as functions of pressure. The v2.0 level2 algorithm also includes significant improvements to the O, H, and chemical heating algorithm, primarily updated reaction rates and procedures and a final pass calculation of energetics parameters. The T(P) retrieval improvements along with significant changes to the climatology (now using WACCM Refb2) have greatly reduced the number of rejected events (and anomalies), particularly for the problematic polar winter periods. The following figure provides a good example of this improvement, it compares the rejection frequency for the NH winter yaw period, January 11 to March 15 2009, a period that includes a strong sudden stratosphere warming (SSW) event - note the dramatic reduction in rejected events for the NH polar region.


Events rejected by screening algorithm for versions 2.0 and 1.07.
Click here for larger image