SABER Temperature Retrieval Accuracies

SABER temperature and pressure profiles are retrieved operationally using two channels observing emission in the vicinity of 15 µm. The measured 15 µm limbpath emission profiles are matched to model calculated values by varying temperature and pressure (hydrostatically constrained) and using WACCM generated CO₂ vertical mixing ratio profiles. Table 1 summarizes the single profile uncertainties of the operational temperture product. These errors are based on studies reported in papers by Remsberg et al. (2008) and Garcia-Comas et al. (2008). The uncertainties discussed in these papers were based on the v1.07 data version but the operational Tk uncertainties used in the tables here include consideration of changes introduced by the v2.0 algorithm. There are no changes in v2.0 relative to v1.07 that would impact precision but overall accuracy can be impacted due to changes in inputs to the NLTE model including:

• v2.0 uses retrieved [O] values for all events whereas v1.07 used retrieved [O] for SZA < 85 degree.
• v2.0 uses CO₂ from an updated WACCM model (version 3.5.48) and is purely WACCM whereas v1.07 uses scaled WACCM results to match a CO₂ trend model.
• Some reaction rates were changed in the CO₂ vibrational temperature model.

Changes to coefficients used for instrument electronic gain switches, the Local Thermodynamic Equilibrium (LTE) algorithm and the procedure used to merge LTE and Non-LTE results, lead to small v2.0 versus v1.07 (<2 K) differences below 80 km. These changes result in a more reliable and more self-consistent product for v2.0. Also, errors in the tables are representative of all environments except for polar summer mesopause events where systematic errors above 80 km are expected to be higher due to higher uncertainty in the vibrational temperatures calculated for these very cold conditions.

Table 1: SABER operational single profile Tk total uncertainty

Operational T Retrieval*	15 km	20 km	30 km	40 km	50 km	60 km	70 km	80 km	90 km	100 km	110 km
Temp. prec. (K)	0.3	0.3	0.3	0.6	0.6	0.7	1.0	1.8	3.6	6.7	15.0
Temp. systematic (K)	1.4	1.2	0.7	1.5	1.9	1.9	1.5	1.4	4.0	5.0	25.0
Temp. accuracy (K)	1.4	1.3	0.8	1.6	2.0	2.0	1.8	2.3	5.4	8.4	29.2

*The WACCM CO₂ results are used at all altitudes for the operational Tk retrieval.

References:

Garcıa-Comas, M., M. Lopez-Puertas, B.T. Marshall, P. P. Wintersteiner, B. Funke,1 D. Bermejo, Pantaleón, C. J. Mertens, E. E. Remsberg, L. L. Gordley, M.G. Mlynczak, and J.M. Russell III, Errors in SABER kinetic temperature caused by non-LTE model parameters, VOL. 113, D24, doi: 10.1029/2008JD010105, 2008.
Link to Article

Remsberg, E. E., B. T. Marshall, M. Garcia-Comas, D. Krueger, G. S. Lingenfelser, J. Martin-Torres, M. G. Mlynczak, J. M. Russell III, A. K. Smith, Y. Zhao, C. Brown, L. L. Gordley, M. J. Lopez-Gonzalez, M. Lopez-Puertas, C.-Y. She, M. J. Taylor, and R. E. Thompson , Assessment of the quality of the Version 1.07 temperatureversus-pressure profiles of the middle atmosphere from TIMED/SABER, JGR, VOL. 113, D17101, doi:10.1029/2008JD010013, 2008.
Link to Article