論文ID: 2025-012
This study evaluates the representation of the quasi-biennial oscillation (QBO) in zonal wind and temperature in Japanese Reanalysis of Three Quarters of a Century (JRA-3Q). We examine the temporal consistency of the QBO between the post- and pre-satellite eras, by comparing it with other reanalyses and observations of radiosonde and satellite data. Here, we quantify the disagreement between the post- and pre-satellite eras using the background spectrum based on the post-satellite era. In the satellite era, the QBO amplitudes of the zonal wind and temperature at 20-30 hPa are somewhat reduced in JRA-3Q by approximately 8 % and 4 %, respectively, compared with other reanalyses. However, the JRA-3Q QBO from the early 1960s and before is substantially degraded, falling below the 95 % confidence level. The representation of the JRA-3Q annual oscillation in the equatorial stratosphere is improved, whereas that in the pre-satellite era in the Japanese 55-year Reanalysis completely disappears due to unrealistically strong damping. The zonal asymmetry of the zonal wind QBO amplitude is characterized by a wave-1 structure with a magnitude of approximately 1 m s−1 in the middle-to-upper stratosphere and a larger amplitude in the central Pacific in the lower stratosphere, consistent with previous studies. The disconnection of temperature QBO-amplitude anomalies between the lower and middle stratosphere is observed in some reanalyses, whereas those in JRA-3Q exhibit an eastward tilt with height, although underlying cause of these anomalies remains unclear.
In short, QBOs remain a challenge especially with high-resolution models. 1) How to tune the high-resolution-version QBOs to match lower-resolution versions set up for climate when restricted to outputs over the short numerical weather prediction timescales. 2) How to sustain QBO amplitudes further into the past with limited data availability. This study has a broader applicability than simply development of reanalysis systems, and understanding and implications of their limitations.
