Improvement of AERI T/q Retrievals and Their Validation at Anmyeon-Do, South Korea

Abstract

n Atmospheric Emitted Radiance Interferometer (AERI), which measures downwelling radiances, has been in operation at Anmyeon-do, South Korea, since June 2010. Temperature and moisture (T/q) profiles with high temporal and vertical resolution can be retrieved from the measured AERI spectrum through the retrieval algorithm AERIPROF. In this work, AERIPROF has been optimized to improve the retrieval performance: 1) a bias spectrum was computed from the coincident radiosondes during the field experiments at Anmyeon-do and 2) regression coefficients were obtained from local radiosondes and associated simulated spectral radiances. An evaluation was performed in the lower troposphere (<700 hPa) with the radiosondes on clear-sky days during the field experiments at Anmyeon-do. The optimized statistical regression results in an improvement of ~0.6 K for temperature and ~0.6 g kg?1 for the mixing ratio on average, in comparison to the original statistical regression. In addition, the optimized AERI T/q retrievals are compared with the satellite [Aqua/Atmospheric Infrared Sounder (AIRS), Meteorological Operation (MetOp)/Infrared Atmospheric Sounding Interferometer (IASI)] T/q retrievals as well as with T/q profiles analyzed from the regional NWP model, the Korea Local Analysis and Prediction System (KLAPS) analysis. The RMS errors of the AERI retrievals are smaller than those of the satellite retrievals (the KLAPS analysis) by ~1.3 K (~0.2 K) for temperature and ~0.3 g kg?1 (~0.2 g kg?1) for the mixing ratio on average. Significant differences could be found between the AERI retrievals with the KLAPS and the satellite retrievals. The local climatic condition seems to be an important factor to bring about this improvement. Considering the training dataset made with spatially distant radiosondes, this is a significant finding. The AERI could bring new information about the lower troposphere.