Figure Caption: An orthographic projection of the Northern Hemisphere (center) showing 4-day running mean geopotential height (GPH) at 0.01 hPa for January 10–13, 2019 surrounded by time-height sections of temperature (T) at 70°N latitude and a variety of longitudes (30°E, 75°E, 120°E, 165°E, 150°W, 105°W, 60°W, and 15°W). Star symbols in the GPH map denote the locations for the T figures. Orange stars show locations at which an elevated stratopause appears clearly at a height of ∼80 km (the same as Figure 3 of Okui et al. (2021) but using JAGUAR-DAS outputs). Courtesy of Haruka Okui.
Model Description: JAGUAR-DAS is an assimilation system developed by a joint project by The University of Tokyo and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) (Koshin et al., 2020; 2021). JAGUAR-DAS employs a four-dimensional local ensemble transform Kalman filter (4D-LETKF) data assimilation system (Miyoshi and Yamane, 2007). The JAGUAR, which was used in JAGUAR-DAS as a forecast model, is a comprehensive numerical model that extends from the Earth’s surface to the lower thermosphere (~150 km) (Watanabe and Miyahara, 2009). It is based on the Model for Interdisciplinary Research on Climate (MIROC) and the Kyushu-GCM and cooperatively developed by JAMSTEC, Kyushu University, and The University of Tokyo. A full set of physical parameterizations necessary for the surface to ~150 km is included.
JAGUAR-DAS assimilates the standard National Centers for Environmental Prediction (NCEP) PREPBUFR dataset for the troposphere and lower stratosphere. For the stratosphere, mesosphere, and lower thermosphere, JAGUAR-DAS assimilates bias-corrected MLS temperature retrievals from 100–0.002 hPa (~16–90 km altitude), SABER temperature retrievals from 40–0.00014 hPa (~22–110 km altitude) and the SSMI/S UAS microwave radiance measurements from 10–0.01hPa (~30–80 km). Model error covariances are estimated from 50-member ensembles. The output from JAGUAR-DAS is 6-hourly and has horizontal grid spacing of 2.8125° in latitude and longitude. JAGUAR-DAS contributed to the intercomparison of middle atmospheric meteorological analyses for the northern hemisphere winter 2009-2010 (McCormack et al., 2021).
JAGUAR-DAS outputs are used as initial values of gravity-wave permitting high-resolution JAGUAR simulations. A series of hindcasts of the major sudden warming occurred in the northern hemisphere winter 2018-2019 were performed using T639 (the minimum resolvable horizontal wavelength of 60 km) using JAGUAR with vertical intervals of 300 m in the middle atmosphere. An elevated stratopause appeared after the sudden warming event ceased. The dynamics of the formation of the elevated stratopause was examined in detail from the viewpoint of the interaction of gravity waves and planetary waves with the mean field (Okui et al., 2021). The three-dimensional structure of the elevated stratopause analyzed using JAGUAR-DAS output is shown here.
References: Koshin, D., Sato, K., Miyazaki, K., & Watanabe, S. (2020). An ensemble Kalman filter data assimilation system for the whole neutral atmosphere. Geoscientific Model Development, 13, 3145–3177. https://doi.org/10.5194/gmd-13-3145-2020
Koshin, D., Sato, K., Kohma, M., & Watanabe, S. (2021). An update on the 4D-LETKF data assimilation system for the whole neutral atmosphere, Geoscientific Model Development Discussion. https://doi.org/10.5194/gmd-2020-381
McCormack, J. P., Harvey, V. L., Pedatella, N., Koshin, D., Sato, K., Coy, L., Watanabe, S., Randall, C. E., Sassi, F., and Holt, L. A. (2021). Intercomparison of Middle Atmospheric Meteorological Analyses for the Northern Hemisphere Winter 2009–2010, Atmos. Chem. Phys., in press. https://doi.org/10.5194/acp-2021-224
Miyoshi, T. and Yamane, S, (2007). Local Ensemble Transform Kalman Filtering with an AGCM at a T159/L48 Resolution, Mon. Weather Rev., 135, 3841–3861, https://doi.org/10.1175/2007MWR1873.1
Okui, H., Sato, K., Koshin, D., & Watanabe, S. (2021). Formation of a mesospheric inversion layer and the subsequent elevated stratopause associated with the major stratospheric sudden warming in 2018/19. Journal of Geophysical Research: Atmospheres, 126, e2021JD034681. https://doi.org/10.1029/2021JD034681
Watanabe, S., & Miyahara, S. (2009). Quantification of the gravity wave forcing of the migrating diurnal tide in a gravity wave-resolving general circulation model. Journal of Geophysical Research, 114, D07110. https://doi.org/10.1029/2008JD011218
