On the intermittency of orographic gravity wave hotspots  and its importance for middle atmosphere dynamics

Kuchař, Aleš; Šácha, Petr; Eichinger, Roland; Jacobi, Ch.; Pišoft, Petr; Rieder, Harald E.

doi:10.5194/wcd-1-481-2020

Cited by 12 publications

(44 citation statements)

References 75 publications

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“…Due to the inhomogeneous data distribution, while these spatial clusters represent both large and small scales well, they contain highly uneven numbers of measurements, with a spread of 3 orders of magnitude in population (compared to 5 orders of magnitude using a regular 3° grid). While suitable for mapping, this may introduce spurious intercluster variations in the statistics we compute, namely, the median and Gini's coefficient of concentration G (used previously for GW studies in, e.g., Hindley et al, 2019; Kuchar et al, 2020; Plougonven et al, 2012; Wright et al, 2013). Means were also calculated for all clusters and showed spatially consistent results but with spike values in some clusters due to outliers.…”

Section: Methodsmentioning

confidence: 99%

Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data

Banyard

2020

JGR Atmospheres

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Gravity waves (GWs) are key drivers of atmospheric dynamics, with major impacts on climate and weather processes. However, they are challenging to measure in observational data, and as a result no large-area multidecadal GW time series yet exist. This has prevented us from quantifying the interactions between GWs and long-timescale climate processes. Here, we exploit temperatures measured by commercial aircraft since 1994 as part of the In-Service Aircraft for a Global Observing System (IAGOS) atmospheric chemistry research program to produce a novel 26-year time series of upper troposphere/lower stratosphere (UTLS) GW measurements across most of the Northern Hemisphere. We analyze 90,342 flight hours (76.2 million flight kilometers) of data, typically at a temporal resolution of seconds and with high temperature precision. We show that GW activity in the Northern Hemisphere UTLS is consistently strongest north of and above the upper tropospheric jet. We also show that GW sources not typically observed in stratospheric data but assumed in model schemes, such as the Rocky Mountains, are visible at these altitudes, suggesting that wave momentum from these sources is deposited specifically between ∼200 and 50 hPa. Our data show no significant impact of the Quasi-Biennial Oscillation, the Northern Annular Mode, or climate change. However, we do see strong evidence of links with the El Niño-Southern Oscillation, which modulates the measured GW signal by ∼25%, and weak evidence of links with the 11-year solar cycle. These results have important implications for atmospheric process modeling and for understanding large-scale climate teleconnections. Plain Language Summary We use 26 years of temperature measurements, made by commercial aircraft flying routine passenger and freight routes, to measure and understand small-scale atmospheric waves ("gravity waves"). These waves play many vital roles in the atmosphere, and they are critically important to understanding and predicting weather and climate. However, due to their small size, they are extremely difficult to study at typical flight altitudes using any other method. Our data provide the longest large-area record of gravity waves from any dataset, with 76 million flight kilometers of measurements made since 1994. We see strong evidence that El Niño affects the behavior of these small waves over northern Europe and central Asia, many thousands of kilometers away from the Pacific Ocean. We also see weak evidence that the waves may be affected by the 11-year cycle of solar intensity. Our results provide a unique window on the interactions between small-scale atmospheric behavior and long-time scale climate dynamical processes and have important implications both for improving atmospheric models and for understanding long-distance climate teleconnections.

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Section: Methodsmentioning

confidence: 99%

Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data

Banyard

2020

JGR Atmospheres

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“…As shown in Figure 8 of Kuchar et al. (2020), the peak is already preceeded by a few days of significant OGWD anomalies in the region of the hotspot. Therefore, at lag = 0 we can see a response that has already been evolving over a few days prior to lag = 0 under an increasing OGWD forcing overlapping with an imprint of the “hotspot preconditioning.” To assess if nudging has a dynamical impact on the composites, we derived the nudging strength as a residual term from the TEM momentum budget (see Equation ).…”

Section: Resultsmentioning

confidence: 85%

“…The identification of strong OGWD events allows to calculate composite anomalies of different variables by subtracting daily values from the monthly climatology of SSW‐free winters. Composites of variables that are analyzed in this study and all processed data are available via the Mendeley Data repository (Kuchar, 2020).…”

Section: Methodsmentioning

confidence: 99%

“…All processed data files for this study are provided via Mendeley Data Kuchar (2020), and all codes to reproduce our figures are provided via GitHub (Kuchar, 2021).…”

Section: Data Availability Statementmentioning

confidence: 99%

“…To account for the intermittency of OGWD and its distribution into hotspots, we build on the methodology of strong OGWD composites presented by Kuchar et al. (2020). The underlying method and model data used are briefly described in Section 2.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Diverse Dynamical Response to Orographic Gravity Wave Drag Hotspots—A Zonal Mean Perspective

Šácha

Kuchař

Eichinger

et al. 2021

Geophysical Research Letters

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In the extratropical atmosphere, Rossby waves (RWs) and internal gravity waves (GWs) propagating from the troposphere mediate a coupling with the middle atmosphere by influencing the dynamics therein. In state‐of‐the‐art chemistry‐climate models (CCMs), RW effects are well resolved while the majority of GW effects have to be parameterized. Here, we analyze orographic GW (OGW) interaction with resolved dynamics in a comprehensive CCM on daily time scales. For this, we apply a recently developed method of strong OGW drag event composites for three pronounced northern hemisphere OGW hotspots. We show that strong OGW drag events are associated with anomalous resolved wave propagation in the stratosphere. Causal links are inferred from previously published work and are supported by the anomalies in zonal circulation and wave activity tendencies. The nature of these anomalies varies depending on the hotspot region, which underlines the parameterized OGW‐resolved dynamics interaction being a two‐way process.

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Parameterized orographic gravity wave drag and dynamical effects in CMIP6 models

Hájková,

Šácha

2023

Clim Dyn

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Orographic gravity waves (OGWs) are an important mechanism for coupling of the free atmosphere with the surface, mediating the momentum and energy transport and influencing the dynamics and circulation especially in the middle-atmosphere. Current global climate models are not able to resolve a large part of the OGW spectrum and hence, OGW effects have to be parameterized in the models. Typically, the only parameterized effect is the OGW induced drag. Despite producing the same quantity as an output and relying on similar assumptions (e.g. instantaneous vertical propagation), the individual OGW parameterization schemes differ in many aspects such as handling of the orography, the inclusion of non-linear effects near the surface and the tuning of the emergent free parameters. In this study, we have reviewed 7 different parameterizations, which are used in 9 different CMIP6 models. We report pronounced differences in the vertical distribution and magnitude of the parameterized OGW drag between the models and study to what extent the inter-model differences can be traced back to the difference in the type and tuning of the schemes. Finally, we demonstrate how the OGW drag differences project to the intermodel differences in the stratospheric dynamics. The study can pave the way for a more systematic research of the OGW parameterizations in the future, with an ultimate goal of lowering the amount of uncertainty of the future climate projections connected with the parameterized effects of unresolved orography.

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On the intermittency of orographic gravity wave hotspots and its importance for middle atmosphere dynamics

Cited by 12 publications

References 75 publications

Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data

Multidecadal Measurements of UTLS Gravity Waves Derived From Commercial Flight Data

Diverse Dynamical Response to Orographic Gravity Wave Drag Hotspots—A Zonal Mean Perspective

Parameterized orographic gravity wave drag and dynamical effects in CMIP6 models

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