Ice-supersaturated  air  masses  in  the  northern mid-latitudes from regular in-situ   observations   by   passenger   aircraft: vertical distribution, seasonality and tropospheric fingerprint

Petzold, A.; Neis, Patrick; Rütimann, Mihal; Rohs, Susanne; Berkes, Florian; Smit, H. G. J.; Krämer, M.; Spelten, N.; Spichtinger, Peter; Nédélec, Philippe; Wahner, Andreas

doi:10.5194/acp-2019-735

Cited by 8 publications

(17 citation statements)

References 34 publications

(68 reference statements)

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“…However, existing studies have highlighted that the ERA5 humidity fields are generally weakly supersaturated (RHi ≈ 100 %) and underestimate regions with very high supersaturations (RHi > 120 %) (Gierens et al, 2020;Schumann et al, 2021;Rädel and Shine, 2010;Reutter et al, 2020;Tompkins et al, 2007). We present a comparison of the ERA5 humidity fields with in situ measurements from the In-service Aircraft for a Global Observing System (IA-GOS) database (Petzold et al, 2020;Boulanger et al, 2018) in Sect. S3, and our analysis supports these earlier findings (Fig.…”

Section: Meteorologymentioning

confidence: 95%

Aviation contrail climate effects in the North Atlantic from 2016 to 2021

et al. 2022

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Abstract. Around 5 % of anthropogenic radiative forcing (RF) is attributed to aviation CO2 and non-CO2 impacts. This paper quantifies aviation emissions and contrail climate forcing in the North Atlantic, one of the world's busiest air traffic corridors, over 5 years. Between 2016 and 2019, growth in CO2 (+3.13 % yr−1) and nitrogen oxide emissions (+4.5 % yr−1) outpaced increases in flight distance (+3.05 % yr−1). Over the same period, the annual mean contrail cirrus net RF (204–280 mW m−2) showed significant inter-annual variability caused by variations in meteorology. Responses to COVID-19 caused significant reductions in flight distance travelled (−66 %), CO2 emissions (−71 %) and the contrail net RF (−66 %) compared with the prior 1-year period. Around 12 % of all flights in this region cause 80 % of the annual contrail energy forcing, and the factors associated with strongly warming/cooling contrails include seasonal changes in meteorology and radiation, time of day, background cloud fields, and engine-specific non-volatile particulate matter (nvPM) emissions. Strongly warming contrails in this region are generally formed in wintertime, close to the tropopause, between 15:00 and 04:00 UTC, and above low-level clouds. The most strongly cooling contrails occur in the spring, in the upper troposphere, between 06:00 and 15:00 UTC, and without lower-level clouds. Uncertainty in the contrail cirrus net RF (216–238 mW m−2) arising from meteorology in 2019 is smaller than the inter-annual variability. The contrail RF estimates are most sensitive to the humidity fields, followed by nvPM emissions and aircraft mass assumptions. This longitudinal evaluation of aviation contrail impacts contributes a quantified understanding of inter-annual variability and informs strategies for contrail mitigation.

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Section: Meteorologymentioning

confidence: 95%

Aviation contrail climate effects in the North Atlantic from 2016 to 2021

et al. 2022

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“…All this results in a nicely coherent pattern with the ISSR directly below the tropopause. This is in general a preferred location for ice supersaturation (Spichtinger et al, 2003a;Petzold et al, 2020).…”

Section: An Example Casementioning

confidence: 98%

The effect of ice supersaturation and thin cirrus on lapse rates in the upper troposphere

et al. 2022

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Abstract. In this paper, the effects of ice-supersaturated regions and thin, subvisual cirrus clouds on lapse rates are examined. For that, probability distribution and density functions of the lapse rate and the potential temperature gradients from 10 years of measurement data from the MOZAIC/IAGOS project and ERA5 reanalysis data were produced, and an analysis of an example case of an ice-supersaturated region with a large vertical extent is performed. For the study of the probability distribution and density functions, a distinction is made between ice-subsaturated and ice-supersaturated air masses (persistent contrails) and situations of particularly high ice supersaturation that allow the formation of optically thick and strongly warming contrails. The estimation of the lapse rates involves two adjacent standard pressure levels of the reanalysis surrounding MOZAIC's measurement/flight points. If the upper of these levels is in the stratosphere, the distribution function for subsaturated cases shows much lower lapse rates than those of supersaturated cases. If all levels are in the troposphere, the distributions become more similar, but the average lapse rates are still higher in supersaturated than in subsaturated cases, and the distributions peak at higher values and are narrower in ice-supersaturated regions (ISSRs) than elsewhere. This narrowing is particularly pronounced if there is substantial supersaturation. For the examination of an example case, ERA5 data and forecasts from ICON-EU (DWD) are compared. ERA5 data, in particular, show a large ice-supersaturated region below the tropopause, which was pushed up by uplifting air, while the data of ICON-EU indicate areas of saturation. The lapse rate in this ice-supersaturated region (ISSR), which is large, is associated with clouds and high relative humidity. Supersaturation and cloud formation result from uplifting of air layers. The temperature gradient within an uplifting layer steepens, for both dry and moist air. As soon as condensation or ice formation starts in the upper part of a lifting layer, the release of latent heat begins to decrease the lapse rate, but radiation starts to act in the opposite direction, keeping the lapse rate high. The highest lapse rates close to the stability limit can only be reached in potentially unstable situations.

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“…Comparing the mean pathlengths for every season in the IAGOS data makes clear that the strongest seasonal cycle is present in the lower stratosphere, with the lowest mean pathlength in summer and the highest values in fall and winter. This might be due to the enhanced storm track activity during fall and winter, where the mass flux (including water vapour) from the troposphere to the stratosphere is largest (Reutter et al, 2015). Further investigations are needed to answer this question.…”

Section: Seasonal Cycle and Height Dependence Of Issr Pathlengthsmentioning

confidence: 99%

“…Many studies in this decade regarding the UTLS region are based on ERA-Interim model output (e.g. Zhan and Wang, 2012;Riese et al, 2012;Uma et al, 2014;Madonna et al, 2014;Reutter et al, 2015). Also, ERA-Interim is still used in many ongoing investigations.…”

Section: Introductionmentioning

confidence: 99%

Ice supersaturated regions: properties and validation of ERA-Interim reanalysis with IAGOS in situ water vapour measurements

Reutter

Neis

Rohs³

et al. 2020

Atmos. Chem. Phys.

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Abstract. Cirrus clouds and their potential formation regions, so-called ice supersaturated regions (ISSRs), with values of relative humidity with respect to ice exceeding 100 %, occur frequently in the tropopause region. It is assumed that ISSRs and cirrus clouds can change the tropopause structure by diabatic processes, driven by latent heating due to phase transition and interaction with radiation. For many research questions, a three-dimensional picture including a sufficient temporal resolution of the water vapour fields in the tropopause region is required. This requirement is fulfilled nowadays by reanalysis products such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. However, for a meaningful investigation of water vapour in the tropopause region, a comparison of the reanalysis data with measurement is advisable, since it is difficult to measure water vapour and to assimilate meaningful measurements into reanalysis products. Here, we present an intercomparison of high-resolution in situ measurements aboard passenger aircraft within the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org, last access: 15 January 2020) with ERA-Interim. Temperature and humidity data over the North Atlantic from 2000 to 2009 are compared relative to the dynamical tropopause. The comparison of the temperature shows good agreement between the measurement and ERA-Interim. While ERA-Interim also shows the main features of the water vapour measurements of IAGOS, the variability of the data is clearly smaller in the reanalysis data set. The combination of temperature and water vapour leads to the relative humidity with respect to ice (RHi). Here, ERA-Interim deviates from the measurements concerning values larger than RHi=100 %, both in number and strength of supersaturation. Also, pathlengths of ISSRs along flight tracks are investigated, representing macrophysical properties as linked to atmospheric flows. The comparison of ISSR pathlengths shows distinct differences, which can be traced back to the spatial resolution of both data sets. Also, the seasonal cycle and height dependence of pathlengths changes for the different data sets due to their spatial resolution. IAGOS shows a significantly greater amount of smaller ISSRs compared to ERA-Interim. Good agreement begins only at pathlengths on the order of the ERA-Interim spatial resolution and larger.

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Ice-supersaturated air masses in the northern mid-latitudes from regular in-situ observations by passenger aircraft: vertical distribution, seasonality and tropospheric fingerprint

Cited by 8 publications

References 34 publications

Aviation contrail climate effects in the North Atlantic from 2016 to 2021

Aviation contrail climate effects in the North Atlantic from 2016 to 2021

The effect of ice supersaturation and thin cirrus on lapse rates in the upper troposphere

Ice supersaturated regions: properties and validation of ERA-Interim reanalysis with IAGOS in situ water vapour measurements

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