Abstract. Various retrieval algorithms have been developed for
retrieving temperature and water vapor profiles from Atmospheric Emitted Radiance Interferometer (AERI) observations. The physical retrieval
algorithm, named AERI Optimal Estimation (AERIoe), outperforms other
retrieval algorithms in many aspects except the retrieval time, which is
significantly increased due to the complex radiative transfer process. The
calculation of the Jacobian matrix is the most computationally intensive
step of the physical retrieval algorithm. Interestingly, an analysis of the
change in AERI observations' information content with respect to Jacobians
revealed that the AERIoe algorithm's performance presents negligible
dependence on these metrics. Thus, the Jacobian matrix could remain
unchanged when the variation in the atmospheric state is small in the
retrieval process to reduce the most time-consuming computation. On the
basis of the above findings, a fast physical–iterative retrieval algorithm
was proposed by adaptively recalculating Jacobians in keeping with the
changes in the atmospheric state. Experiments with synthetic observations
demonstrate that the proposed method experiences an average reduction in
retrieval time by an impressive 59 % compared to the original AERIoe
algorithm while achieving maximum root-mean-square errors of less than 0.95 K and 0.22 log(ppmv) for heights below 3 km for the temperature and water vapor profile, respectively. Further analyses revealed that the fast-retrieval algorithm reached an acceptable convergence rate of 98.7 %, marginally lower than AERIoe's 99.9 % convergence rate for the 826 cases used in this study.