Understanding the Discrepancy of the Upper Atmosphere Temperature Trend from Satellite Observations

As stated in the IPCC 6^th Assessment (IPCC, 2022; Chapter 2), the upper atmospheric temperature clearly shows a cooling trend in the stratosphere, and a warming trend in the upper troposphere. The observations from AIRS, GPS-RO, and radiosonde data converge on the sign of the temperature trends over the last 20 years. However, the magnitudes vary among different instruments and even between products from the same instrument but processed using different NASA operational algorithms. Such discrepancies are not only closely related to the uncertainty of the trends derived from different datasets, but also contributed by sampling differences among different instruments. In this study, we examine the upper atmospheric temperature trends from different AIRS products, GPS-RO, and a temperature record from a climate finger printing method. We further quantify the impact of temporal and spatial sampling on the discrepancy of the trends derived from these datasets. With the daily global coverage and the long-term consistency of the AIRS soundings, we explore the spatial and temporal contexts of AIRS data for monitoring the regional temperature change, and the requirement on the data record length.