Radiosonde Temperature Anomalies in the Troposphere and Lower Stratosphere for the Globe, Hemispheres, and Latitude Zones

Abstract. Measurements from the Microwave Limb Sounder (MLS) on the 68 hPa pressure level from 1 January 2005 to 31 December 2010 are used to calculate the coherence between anomalies in the tropical mean mixing ratios of H2O, CO, and N2O, and 100 hPa temperature. We show that the fluctuations of lower stratospheric water vapor in the subseasonal and multiyear time windows are generated by different physical mechanisms. In the subseasonal time window, the spatial pattern of the coherence between 100 hPa temperature and water vapor, and the time lag, show that the variability in lower stratospheric water vapor is dominated by fluctuations in upwelling forced by the dissipation of tropical Rossby waves. In the multiyear time window, the variability of lower stratospheric water vapor is more strongly coherent with temperature fluctuations on the 100 hPa surface in regions where the annual mean temperature is colder than 194 K. In addition, the 68 hPa water vapor anomalies lag the 100 hPa temperature anomalies by roughly 140 days. In this time window, the variability of lower stratospheric water vapor is therefore dominated by changes in the temperature dependent dehydration efficiency which modulate the water vapor stratospheric entry mixing ratio. On subseasonal timescales, the spatial pattern of the coherence between 100 hPa temperature and 68 hPa CO anomalies is very similar to the pattern of coherence between 100 hPa temperature and the Real-time Multivariate MJO series 1 (RMM1) index of the Madden Julian Oscillation (MJO). The MJO therefore has a strong influence on the subseasonal variability of CO in the lower stratosphere. The subseasonal 68 hPa CO and H2O anomalies lag the 100 hPa temperature anomalies by 3.16 and 2.51 days, respectively. The similarity between the two time lags suggests that the subseasonal CO anomalies can also be attributed to changes in upwelling. The multiyear variability in lower stratospheric N2O appears to be dominated by the Quasi Biennial Oscillation (QBO).

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11569-2020 ◽

2020 ◽

Vol 20 (19) ◽

pp. 11569-11592 ◽

Cited By ~ 2

Author(s):

Robin Pilch Kedzierski ◽

Katja Matthes ◽

Karl Bumke

Keyword(s):

Wave Packet ◽

Rossby Wave ◽

Lower Stratosphere ◽

Satellite System ◽

Pressure Data ◽

Hilbert Transforms ◽

Upper Troposphere ◽

Temperature Anomalies ◽

Zonal Scale ◽

Novel Approach

Abstract. The present study describes Rossby wave packet (RWP) properties in the upper troposphere and lower stratosphere (UTLS) with the use of Global Navigation Satellite System radio occultation (GNSS-RO) measurements. This global study covering both hemispheres' extratropics is the first to tackle medium- and synoptic-scale waves with GNSS-RO. We use 1 decade of GNSS-RO temperature and pressure data from the CHAMP, COSMIC, GRACE, Metop-A, Metop-B, SAC-C and TerraSAR-X missions, combining them into one gridded dataset for the years 2007–2016. Our approach to extract RWP anomalies and their envelope uses Fourier and Hilbert transforms over longitude without pre- or post-processing the data. Our study is purely based on observations, only using ERA-Interim winds to provide information about the background wind regimes. The RWP structures that we obtain in the UTLS agree well with theory and earlier studies, in terms of coherent phase or group propagation, zonal scale and distribution over latitudes. Furthermore, we show that RWP pressure anomalies maximize around the tropopause, while RWP temperature anomalies maximize right above the tropopause height with a contrasting minimum right below. RWP activity follows the zonal-mean tropopause during all seasons. RWP anomalies in the lower stratosphere are dynamically coupled to the upper troposphere. They are part of the same system with a quasi-barotropic structure across the UTLS. RWP activity often reaches up to 20 km height and occasionally higher, defying the Charney–Drazin criterion. We note enhanced amplitude and upward propagation of RWP activity during sudden stratospheric warmings. We provide observational support for improvements in RWP diagnostics and wave trend analysis in models and reanalyses. Wave quantities follow the tropopause, and diagnosing them on fixed pressure levels (which the tropopause does not follow) can lead to aliasing. Our novel approach analyzing GNSS-RO pressure anomalies provides wave signals with better continuity and coherence across the UTLS and the stratosphere, compared to temperature anomalies. Thus, RWP vertical propagation is much easier to analyze with pressure data.

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

10.5194/acp-2020-124 ◽

2020 ◽

Author(s):

Robin Pilch Kedzierski ◽

Katja Matthes ◽

Karl Bumke

Keyword(s):

Wave Packet ◽

Rossby Wave ◽

Lower Stratosphere ◽

Satellite System ◽

Pressure Data ◽

Hilbert Transforms ◽

Upper Troposphere ◽

Temperature Anomalies ◽

Zonal Scale ◽

Novel Approach

Abstract. The present study describes Rossby wave packet (RWP) properties in the upper-troposphere and lower-stratosphere (UTLS) with the use of Global Navigation Satellite System radio occultation (GNSS-RO) measurements. This global study covering both hemisphere's extratropics is the first to tackle medium and synoptic-scale waves with GNSS-RO. We use one decade of GNSS-RO temperature and pressure data from the CHAMP, COSMIC, GRACE, Metop-A, Metop-B, SAC-C and TerraSAR-X missions; combining them into one gridded dataset for the years 2007–2016. Our approach to extract RWP anomalies and their envelope uses Fourier and Hilbert transforms over longitude without pre- or post-processing the data. Our study is purely based on observations, only using ERA-Interim winds to provide information about the background wind regimes. The RWP structures that we obtain in the UTLS agree well with theory and earlier studies, in terms of coherent phase/group propagation, zonal scale and distribution over latitudes. Furthermore, we show that RWP pressure anomalies maximize around the tropopause, while RWP temperature anomalies maximize right above tropopause height with a contrasting minimum right below. RWP activity follows the zonal-mean tropopause during all seasons. RWP anomalies in the lower stratosphere are dynamically coupled to the upper troposphere. They are part of the same system with a quasi-barotropic structure across the UTLS. RWP activity often reaches up to 20 km height and occasionally higher, defying the Charney–Drazin criterion. We note enhanced amplitude and upward propagation of RWP activity during sudden stratospheric warmings. We provide observational support for improvements in RWP diagnostics and wave trend analysis in models and reanalyses. Wave quantities follow the tropopause, and diagnosing them on fixed pressure levels (which the tropopause does not follow) can lead to aliasing. Our novel approach analysing GNSS-RO pressure anomalies provides wave signals with better continuity and coherence across the UTLS and the stratosphere, compared to temperature anomalies. Thus, RWP vertical propagation is much easier to analyse with pressure data.

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A global perspective on atmospheric blocking using GPS radio occultation – one decade of observations

Atmospheric Measurement Techniques ◽

10.5194/amt-10-4727-2017 ◽

2017 ◽

Vol 10 (12) ◽

pp. 4727-4745 ◽

Cited By ~ 5

Author(s):

Lukas Brunner ◽

Andrea K. Steiner

Keyword(s):

Southern Hemisphere ◽

Radio Occultation ◽

Lower Stratosphere ◽

Global Perspective ◽

Specific Humidity ◽

Atmospheric Blocking ◽

Data Set ◽

Gps Radio Occultation ◽

Temperature Anomalies ◽

Temperature And Humidity

Abstract. Atmospheric blocking represents a weather pattern where a stationary high-pressure system weakens or reverses the climatological westerly flow at mid-latitudes for up to several weeks. It is closely connected to strong anomalies in key atmospheric variables such as geopotential height, temperature, and humidity. Here we provide, for the first time, a comprehensive, global perspective on atmospheric blocking and related impacts by using an observation-based data set from Global Positioning System (GPS) radio occultation (RO) from 2006 to 2016. The main blocking regions in both hemispheres and seasonal variations are found to be represented well in RO data. The effect of blocking on vertically resolved temperature and humidity anomalies in the troposphere and lower stratosphere is investigated for blocking regions in the Northern and Southern hemispheres, respectively. We find a statistically significant correlation of blocking with positive temperature anomalies, exceeding 3 K in the troposphere, and a reversal above the tropopause with negative temperature anomalies below −3 K in the lower stratosphere. Specific humidity is positively correlated with temperature throughout the troposphere with larger anomalies revealed in the Southern Hemisphere. At the eastern and equatorward side of the investigated blocking regions, a band of tropospheric cold anomalies reveals advection of cold air by anticyclonic motion around blocking highs, which is less distinct in the Southern Hemisphere due to stronger zonal flow. We find GPS RO to be a promising new data set for blocking research that gives insight into the vertical atmospheric structure, especially in light of the expected increase in data coverage that future missions will provide.

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Variability in QBO Temperature Anomalies on Annual and Decadal Time Scales

Journal of Climate ◽

10.1175/jcli-d-20-0287.1 ◽

2021 ◽

Vol 34 (2) ◽

pp. 589-605

Author(s):

Zane Martin ◽

Adam Sobel ◽

Amy Butler ◽

Shuguang Wang

Keyword(s):

Time Scales ◽

Lower Stratosphere ◽

Boreal Winter ◽

Quasi Biennial Oscillation ◽

Tropical Tropopause Layer ◽

Temperature Anomalies ◽

Tropical Tropopause ◽

Tropical Troposphere ◽

The Relationship ◽

Biennial Oscillation

AbstractThe stratospheric quasi-biennial oscillation (QBO) induces temperature anomalies in the lower stratosphere and tropical tropopause layer (TTL) that are cold when lower-stratospheric winds are easterly and warm when winds are westerly. Recent literature has indicated that these QBO temperature anomalies are potentially important in influencing the tropical troposphere, and particularly in explaining the relationship between the QBO and the Madden–Julian oscillation (MJO). The authors examine the variability of QBO temperature anomalies across several time scales using reanalysis and observational datasets. The authors find that, in boreal winter relative to other seasons, QBO temperature anomalies are significantly stronger (i.e., colder in the easterly phase of the QBO and warmer in the westerly phase of the QBO) on the equator, but weaker off the equator. The equatorial and subtropical changes compensate such that meridional temperature gradients and thus (by thermal wind balance) equatorial zonal wind anomalies do not vary in amplitude as the temperature anomalies do. The same pattern of stronger on-equatorial and weaker off-equatorial QBO temperature anomalies is found on decadal time scales: stronger anomalies are seen for 1999–2019 compared to 1979–99. The causes of these changes to QBO temperature anomalies, as well as their possible relevance to the MJO–QBO relationship, are not known.

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A global perspective on atmospheric blocking using GPS radio occultation – one decade of observations

10.5194/amt-2017-205 ◽

2017 ◽

Author(s):

Lukas Brunner ◽

Andrea K. Steiner

Keyword(s):

Southern Hemisphere ◽

Radio Occultation ◽

Lower Stratosphere ◽

Global Perspective ◽

Specific Humidity ◽

Atmospheric Blocking ◽

Data Set ◽

Gps Radio Occultation ◽

Temperature Anomalies ◽

Temperature And Humidity

Abstract. Atmospheric blocking represents a weather pattern where a stationary high-pressure system weakens or reverses the climatological westerly flow at mid-latitudes for up to several weeks. It is closely connected to strong anomalies in key atmospheric variables such as geopotential height, temperature, and humidity. Here we provide, for the first time, a comprehensive, global perspective on atmospheric blocking and related impacts by using an observation-based data set from Global Positioning System (GPS) radio occultation (RO) from 2006 to 2016. The main blocking regions in both hemispheres and seasonal variations are found to be well-represented in RO data. The effect of blocking on vertically resolved temperature and humidity anomalies in the troposphere and lower stratosphere is investigated for blocking regions in the northern and southern hemisphere, respectively. We find a statistically significant correlation of blocking with positive temperature anomalies, exceeding 3 K in the troposphere and a reversal above the tropopause with negative temperature anomalies below -3 K in the lower stratosphere. Specific humidity is positively correlated with temperature throughout the troposphere with larger anomalies revealed in the southern hemisphere. At the eastern and equator-ward side of the investigated blocking regions, a band of tropospheric cold anomalies reveals advection of cold air by anti-cyclonic motion around blocking highs, which is less distinct in the southern hemisphere due to stronger zonal flow. We find GPS RO a promising new data set for blocking research giving insight into the vertical atmospheric structure, especially in light of the expected increase in data coverage that future missions will provide.

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