New insights into Rossby wave packet properties in the extratropical UTLS using GNSS radio occultations

Kedzierski, Robin Pilch; Matthes, Katja; Bumke, Karl

doi:10.5194/acp-20-11569-2020

Cited by 9 publications

(6 citation statements)

References 105 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results are presented in wavenumber-latitude diagrams, similarly to previous studies (e.g. Pilch Kedzierski et al, 2020;Wolf and Wirth, 2017). Our wavenumber-latitude analysis is not directly comparable to either of the studies mentioned above because we did not apply any high-pass filtering in time before the Fourier decomposition.…”

Section: Model Experimental Design Data and Methodologysupporting

confidence: 49%

Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps

Savita,

Kjellsson,

Pilch Kedzierski

et al. 2024

Geosci. Model Dev.

Self Cite

View full text Add to dashboard Cite

Abstract. We examine the impact of horizontal resolution and model time step on the climate of the OpenIFS version 43r3 atmospheric general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e. ∼100, ∼50, and ∼25 km) while maintaining the same time step (i.e. 15 min) and using different time steps (i.e. 60, 30, and 15 min) at 100 km horizontal resolution. We find that the surface zonal wind bias is significantly reduced over certain regions such as the Southern Ocean and the Northern Hemisphere mid-latitudes and in tropical and subtropical regions at a high horizontal resolution (i.e. ∼25 km). Similar improvement is evident too when using a coarse-resolution model (∼100 km) with a smaller time step (i.e. 30 and 15 min). We also find improvements in Rossby wave amplitude and phase speed, as well as in weather regime patterns, when a smaller time step or higher horizontal resolution is used. The improvement in the wind bias when using the shorter time step is mostly due to an increase in shallow and mid-level convection that enhances vertical mixing in the lower troposphere. The enhanced mixing allows frictional effects to influence a deeper layer and reduces wind and wind speed throughout the troposphere. However, precipitation biases generally increase with higher horizontal resolutions or smaller time steps, whereas the surface air temperature bias exhibits a small improvement over North America and the eastern Eurasian continent. We argue that the bias improvement in the highest-horizontal-resolution (i.e. ∼25 km) configuration benefits from a combination of both the enhanced horizontal resolution and the shorter time step. In summary, we demonstrate that, by reducing the time step in the coarse-resolution (∼100 km) OpenIFS model, one can alleviate some climate biases at a lower cost than by increasing the horizontal resolution.

show abstract

Section: Model Experimental Design Data and Methodologysupporting

confidence: 49%

Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps

Savita,

Kjellsson,

Pilch Kedzierski

et al. 2024

Geosci. Model Dev.

Self Cite

View full text Add to dashboard Cite

show abstract

“…High‐resolution temperature data in the TTL are available from satellite retrievals based on the Global Navigation Satellite System‐Radio Occultation (GNSS‐RO) technique. We use a monthly mean, gridded data set of cold point and 100 hPa temperatures constructed from measurements obtained from all major GNSS‐RO missions between 2002 and 2018 (Pilch Kedzierski et al, 2020). For each profile, the CPT temperature was identified based on the cold point criteria and monthly mean profiles are computed for 30° × 10° bins between 30°N and 30°S (see Tegtmeier et al, 2020, for details).…”

Section: Methodsmentioning

confidence: 99%

Zonal Asymmetry of the QBO Temperature Signal in the Tropical Tropopause Region

Tegtmeier

Anstey

Davis

et al. 2020

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

The quasi-biennial oscillation (QBO) of the equatorial zonal wind leads to zonally symmetric temperature variations in the stratosphere that descend downward. Here we investigate the QBO-induced temperature anomalies in the tropical tropopause layer (TTL) and detect pronounced longitudinal variations of the signal. In addition, the QBO temperature anomalies show a strong seasonal variability. The magnitude of these seasonal and longitudinal QBO variations is comparable to the magnitude of the well-known zonal mean QBO signal in the TTL. At the cold point tropopause, the strongest QBO variations of around ±1.6 K are found over regions of active convection such as the West Pacific and Africa during boreal winter. The weakest QBO variations of ±0.25 K are detected over the East Pacific during boreal summer, while the zonal mean signal ranges around ±0.7 K. The longitudinal variations are associated with enhanced convective activity that occurs during QBO cold phases and locally enhances the cold anomalies. Plain Language Summary Temperatures in the tropical stratosphere, the atmospheric region between 20°S and 20°N and above 18 km, oscillate between colder and warmer conditions with a full cycle taking about 28 months on average. Observations over the last decades have shown that the strength of this so-called quasi-biennial oscillation of stratospheric temperature is similar for all longitudes within the tropics. The temperature variations extend downward into the region that connects the stratosphere with troposphere. We show that in this transition region between the two atmospheric layers, the temperature oscillations can be stronger or weaker depending on the geographical position along the equator. Especially strong temperature oscillations are found over regions of frequently occurring thunderstorms such as the West Pacific and Africa. The fact that a stratospheric signal such as the quasi-biennial oscillation is linked with thunderstorms has implications for understanding how the upper atmosphere can impact tropical weather phenomena.

show abstract

“…Beside hemisphere-wide planetary wave patterns, RWPs are related to mid-latitude heat events (Fragkoulidis et al, 2018;Röthlisberger et al, 2016). For instance, a recurrence of transient RWPs was identified during the European heat event of 1994 (Röthlisberger et al, 2019) and the Russian heat event of 2010 (Pilch Kedzierski et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Connecting North Atlantic SST Variability to European Heat Events over the Past Decades

Krüger,

Kjellsson,

Kedzierski

et al. 2023

TellusA

Self Cite

View full text Add to dashboard Cite

The occurrence of European heat events has increased during the last two decades. European heat events are responsible for social, economic and environmental damage and are projected to increase in magnitude, frequency and duration under global warming, strengthening the interest about the contribution of different mechanisms. Using the ERA5 reanalysis product, we go beyond case studies relating European heat events with cold North Atlantic sea surface temperatures (SSTs), and perform a systematic approach with a composite analysis to investigate the link between North Atlantic SSTs in a domain south of Greenland and the 2m air temperature (T2m) over central Europe. Composites of different North Atlantic SST states show that events with a negative tendency of North Atlantic SSTs are often followed by positive European T2m anomalies during summers when the North Atlantic SSTs are persistently low for several months. Enhanced lower–tropospheric baroclinicity in the North Atlantic is followed during these events by a slantwise ascent and an enhanced upper–tropospheric waveguide, promoting a downstream development of an European ridge. A combination of a wave number 3 pattern and regionally confined Rossby wave activity contribute to a trough–ridge pattern in the North Atlantic–European sector. A composite of European heat events further confirms the lagged statistical relationship between cold North Atlantic SSTs with a negative tendency and positive European T2m anomalies. A negative tendency of North Atlantic SSTs precedes 15 of 18 European heat events, and cold North Atlantic SST conditions are present during 14 of 18 European heat events.

show abstract

New insights into Rossby wave packet properties in the extratropical UTLS using GNSS radio occultations

Cited by 9 publications

References 105 publications

Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps

Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps

Zonal Asymmetry of the QBO Temperature Signal in the Tropical Tropopause Region

Connecting North Atlantic SST Variability to European Heat Events over the Past Decades

Contact Info

Product

Resources

About