The diabatic heat budget of the upper troposphere and lower/mid stratosphere in ECMWF reanalyses

Fueglistaler, S.; Legras, Bernard; Beljaars, A.; Morcrette, J. J.; Simmons, A. J.; Tompkins, Adrian M.; Uppala, S.

doi:10.1002/qj.361

Cited by 105 publications

(143 citation statements)

References 47 publications

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“…We cannot rule out that our simulation is influenced to a certain extent by such problems. However, Fueglistaler et al [2009] showed that the biases in the heat and momentum budget of ERA-Interim are much reduced compared to previous reanalysis like ERA-40. Moreover, Monge-Sanz et al [2012] found recently that also the spurious dispersive transport in ERA-Interim is significantly reduced and characteristics of stratospheric transport (e.g., age of air, vertical dispersion) are clearly improved.…”

Section: 1002/2014jd022468mentioning

confidence: 78%

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

et al. 2015

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We analyze the variability of mean age of air (AoA) and of the local effects of the stratospheric residual circulation and eddy mixing on AoA within the framework of the isentropic zonal mean continuity equation. AoA for the period 1988–2013 has been simulated with the Lagrangian chemistry transport model CLaMS driven by ERA‐Interim winds and diabatic heating rates. Model simulated AoA in the lower stratosphere shows good agreement with both in situ observations and satellite observations from Michelson Interferometer for Passive Atmospheric Sounding, even regarding interannual variability and changes during the last decade. The interannual variability throughout the lower stratosphere is largely affected by the quasi‐biennial‐oscillation‐induced circulation and mixing anomalies, with year‐to‐year AoA changes of about 0.5 years. The decadal 2002–2012 change shows decreasing AoA in the lowest stratosphere, below about 450 K. Above, AoA increases in the Northern Hemisphere and decreases in the Southern Hemisphere. Mixing appears to be crucial for understanding AoA variability, with local AoA changes resulting from a close balance between residual circulation and mixing effects. Locally, mixing increases AoA at low latitudes (40°S–40°N) and decreases AoA at higher latitudes. Strongest mixing occurs below about 500 K, consistent with the separation between shallow and deep circulation branches. The effect of mixing integrated along the air parcel path, however, significantly increases AoA globally, except in the polar lower stratosphere. Changes of local effects of residual circulation and mixing during the last decade are supportive of a strengthening shallow circulation branch in the lowest stratosphere and a southward shifting circulation pattern above.

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Section: 1002/2014jd022468mentioning

confidence: 78%

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

et al. 2015

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“…TPTT) and only the temperature tendency due to radiation are stored. The latter term could be further split into the clear-sky and cloud contributions, with a further separation of the clear-sky radiative tendency into short and long wave components (Fueglistaler et al 2009). …”

Section: Definition Of Indicesmentioning

confidence: 99%

The summer circulation over the eastern Mediterranean and the Middle East: influence of the South Asian monsoon

2012

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The summer circulation over the eastern Mediterranean and the Middle East (EMME) is dominated by persistent northerly winds (Etesians) whose ventilating effect counteracts the adiabatic warming induced by large scale subsidence. The ERA40 dataset is used to study the vertical distribution of these circulation features, which both appear to be reconciled manifestations of the South Asian monsoon influence. As predicted by past idealized modeling studies, in late spring a westward expanding upper level warm structure and subsidence areas are associated with Rossby waves excited by the monsoon convection. Steep sloping isentropes that develop over the EMME facilitate further subsidence on the western and northern periphery of the warm structure, which is exposed to the midlatitude westerlies. The northerly flow and descent over the eastern Mediterranean have maxima in July that are strikingly synchronous to the monsoon convection over northern India, where the weaker easterly jet favors a stronger Rossby wave response and consequent impact on the EMME circulation. The pronounced EMME topography modifies the monsoon induced structure, firstly, by inducing orographically locked summer anticyclones. These enhance the mid and low level northwesterly flow at their eastern flanks, leading to distinct subsidence maxima over the eastern Mediterranean and Iran. Secondly, topography amplifies the subsidence and the northerly flow over the Aegean, Red Sea, the Iraq-Gulf region and to the east of the Caspian Sea.

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“…The first involves ascents to compensate diabatic heating (e.g. Salby and Callaghan, 2004;Fueglistaler et al, 2009b); this compensating effect led to very small updraughts with vertical velocity values of w ∼ 0.001 m s −1 . The second source involves large-scale equatorial waves, e.g.…”

Section: Large-scale Dynamicsmentioning

confidence: 99%

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers

Spichtinger

Krämer²

2013

Atmos. Chem. Phys.

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Abstract. The occurrence of high, persistent ice supersaturation inside and outside cold cirrus in the tropical tropopause layer (TTL) remains an enigma that is intensely debated as the "ice supersaturation puzzle". However, it was recently confirmed that observed supersaturations are consistent with very low ice crystal concentrations, which is incompatible with the idea that homogeneous freezing is the major method of ice formation in the TTL. Thus, the tropical tropopause "ice supersaturation puzzle" has become an "ice nucleation puzzle". To explain the low ice crystal concentrations, a number of mainly heterogeneous freezing methods have been proposed. Here, we reproduce in situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamic conditions in the TTL, namely the superposition of slow large-scale updraughts with high-frequency short waves. From the simulations, it follows that the full range of observed ice crystal concentrations can be explained when the model results are composed from scenarios with consecutive heterogeneous and homogeneous ice formation and scenarios with pure homogeneous ice formation occurring in very slow (< 1 cm s −1 ) and faster (> 1 cm s −1 ) largescale updraughts, respectively. This statistical analysis shows that about 80 % of TTL cirrus can be explained by "classical" homogeneous ice nucleation, while the remaining 20 % stem from heterogeneous and homogeneous freezing occurring within the same environment. The mechanism limiting ice crystal production via homogeneous freezing in an environment full of gravity waves is the shortness of the gravity waves, which stalls freezing events before a higher ice crystal concentration can be formed.

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The diabatic heat budget of the upper troposphere and lower/mid stratosphere in ECMWF reanalyses

Cited by 105 publications

References 47 publications

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

The summer circulation over the eastern Mediterranean and the Middle East: influence of the South Asian monsoon

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers

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