Gravity‐Wave‐Driven Seasonal Variability of Temperature Differences Between ECMWF IFS and Rayleigh Lidar Measurements in the Lee of the Southern Andes

Abstract

Long‐term high‐resolution temperature data of the Compact Rayleigh Autonomous Lidar (CORAL) is used to evaluate temperature and gravity wave (GW) activity in ECMWF Integrated Forecasting System (IFS) over Río Grande (53.79°S, 67.75°W), which is a hot spot of stratospheric GWs in winter. Seasonal and altitudinal variations of the temperature differences between the IFS and lidar are studied for 2018 with a uniform IFS version. Moreover, interannual variations are considered taking into account updated IFS versions. We find monthly mean temperature differences <2 K at 20–40 km altitude. At 45–55 km, the differences are smaller than 4 K during summer. The largest differences are found during winter (4 K in May 2018 and −10 K in August 2018, July 2019 and 2020). The width of the difference distribution (15th/85th percentiles), the root mean square error, and maximum differences between instantaneous individual profiles are also larger during winter (>±10 K) and increase with altitude. We relate this seasonal variability to middle atmosphere GW activity. In the upper stratosphere and lower mesosphere, the observed temperature differences result from both GW amplitude and phase differences. The IFS captures the seasonal cycle of GW potential energy (Ep) well, but underestimates Ep in the middle atmosphere. Experimental IFS simulations without damping by the model sponge for May and August 2018 show an increase in the monthly mean Ep above 45 km from only ≈10% of the Ep derived from the lidar measurements to 26% and 42%, respectively. GWs not resolved in the IFS are likely explaining the remaining underestimation of the Ep.

Observations of Typhoon Generated Gravity Waves From the CIPS and AIRS Instruments and Comparison to the High‐Resolution ECMWF Model

“…As expected, the horizontal extent of concentric GWs expands as the waves propagate upward, consistent with the CIPS and AIRS observations shown in Figures 2a and 2b. Amplitudes of concentric waves are getting weaker above 0.8 hPa level (∼55 km) and wave structures are significantly weakened and disappeared above 0.25 hPa level (∼60 km), which we believe is due to damping in ECMWF at higher altitudes by the sponge layers discussed by previous studies (e.g., Ehard et al., 2018; Gisinger et al., 2022). Gisinger et al.…”

“…Amplitudes of concentric waves are getting weaker above 0.8 hPa level (∼55 km) and wave structures are significantly weakened and disappeared above 0.25 hPa level (∼60 km), which we believe is due to damping in ECMWF at higher altitudes by the sponge layers discussed by previous studies (e.g., Ehard et al, 2018;Gisinger et al, 2022). Gisinger et al (2022) observed that above ∼45 km the amplitudes of GWs in ECMWF are weaker than in lidar observations. Although GW amplitudes might be reduced above ∼45 km, our results indicate that GW structures are reasonably simulated compared to CIPS around 50-55 km.…”

“…This version of ECMWF is capable of resolving mesoscale GWs with horizontal scales larger than ∼70 km (Preusse et al., 2014). Although ECMWF extends up to ∼80 km, amplitudes of GWs are suppressed above ∼45 km due to a sponge layer (Ehard et al., 2018; Gisinger et al., 2022; Schroeder et al., 2009). Earlier versions of ECMWF GWs have been validated against AIRS, SABER, and COSMIC satellite observations, lidar and radiosonde ground‐based observations, and other high‐resolution models including the Weather Research and Forecasting (WRF) model (e.g., Alexander & Teitelbaum, 2007; Kim et al., 2009; Schroeder et al., 2009; D. L. Wu & Eckermann, 2008; Yamashita et al., 2010).…”

Non‐Orographic Gravity Waves and Turbulence Caused by Merging Jet Streams

“…Note that the major phase lines in the IFS data are aligned in an almost identical orientation compared with the airborne observations. A lower degree of agreement of the amplitudes of Δ T above 40 km is probably related to increased layer level spacing and artificial damping in the IFS model (e.g., Gisinger et al., 2022).…”

The Mission Support System (MSS v7.0.4) and its use in planning for the SouthTRAC aircraft campaign

“…The scientific objectives were very diverse, ranging from examining air polluted by biomass burning in the tropics (Johansson et al, 2022) (and, as a target of opportunity, Australia; Ohneiser et al, 2022), the breakdown of the Antarctic polar vortex and the associated chemical and physical structure, the general chemical composition of the Southern Hemisphere's upper troposphere-lower stratosphere (Johansson et al, 2022), to studying gravity waves. Some exemplary outcomes from the gravity wave part of the SouthTRAC campaign include clear-air turbulence studies (Rodriguez Imazio et al, 2022;Dörnbrack et al, 2022), gravity wave propagation from the Southern Andes and the Antarctic peninsula into the mesosphere (Reichert et al, 2021;Conte et al, 2022), gravity wave observation and model intercomparison (Gisinger et al, 2022;Dörnbrack et al, 2022;Liu et al, 2022;Alexander et al, 2022), mountain waves drifting upwind of the Andes (Krasauskas et al, 2022), gravity wave refraction due to wind shear (Geldenhuys et al, 2022), and gravity waves from orographic and non-orographic sources (Alexander et al, 2022;de la Torre et al, 2022).…”