Sensitivities of Lagrangian modelling of mid-latitude cirrus clouds to trajectory data quality

Kienast-Sjögren, Erika; Miltenberger, Annette K.; Luo, B. P.; Peter, Thomas

doi:10.5194/acp-15-7429-2015

Cited by 15 publications

(16 citation statements)

References 76 publications

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“…The amplitudes are statistically distributed, whereas the maximum amplitudes increases with height and range from 0.3 K for the slowest constant vertical velocity to 4 K for the fastest constant vertical velocity. The frequency spectra and the resulting power spectral density (PSD) are in accordance with Kienast-Sjögren et al (2015) and also with in situ measurements of temperature fluctuations during several aircraft campaigns (e.g. MACPEX, see Jensen et al, 2013b).…”

Section: Cirrus Scenariosmentioning

confidence: 67%

A microphysics guide to cirrus clouds – Part 1: Cirrus types

Krämer¹,

Rolf²,

et al. 2016

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Abstract. The microphysical and radiative properties of cirrus clouds continue to be beyond understanding and thus still represent one of the largest uncertainties in the prediction of the Earth's climate (IPCC, 2013). Our study aims to provide a guide to cirrus microphysics, which is compiled from an extensive set of model simulations, covering the broad range of atmospheric conditions for cirrus formation and evolution. The model results are portrayed in the same parameter space as field measurements, i.e., in the Ice Water ContentTemperature (IWC-T) parameter space. We validate this cirrus analysis approach by evaluating cirrus data sets from 17 aircraft campaigns, conducted in the last 15 years, spending about 94 h in cirrus over Europe, Australia, Brazil as well as South and North America. Altogether, the approach of this study is to track cirrus IWC development with temperature by means of model simulations, compare with observations and then assign, to a certain degree, cirrus microphysics to the observations. Indeed, the field observations show characteristics expected from the simulated Cirrus Guide. For example, high (low) IWCs are found together with high (low) ice crystal concentrations N ice .An important finding from our study is the classification of two types of cirrus with differing formation mechanisms and microphysical properties: the first cirrus type forms directly as ice (in situ origin cirrus) and splits in two subclasses, depending on the prevailing strength of the updraft: in slow updrafts these cirrus are rather thin with lower IWCs, while in fast updrafts thicker cirrus with higher IWCs can form. The second type consists predominantly of thick cirrus originating from mixed phase clouds (i.e., via freezing of liquid droplets -liquid origin cirrus), which are completely glaciated while lifting to the cirrus formation temperature region (< 235 K). In the European field campaigns, slow updraft in situ origin cirrus occur frequently in low-and high-pressure systems, while fast updraft in situ cirrus appear in conjunction with jet streams or gravity waves. Also, liquid origin cirrus mostly related to warm conveyor belts are found. In the US and tropical campaigns, thick liquid origin cirrus which are formed in large convective systems are detected more frequently.

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Section: Cirrus Scenariosmentioning

confidence: 67%

A microphysics guide to cirrus clouds – Part 1: Cirrus types

Krämer¹,

Rolf²,

et al. 2016

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“…These processes are subject to uncertainties in the understanding and parametrization of homogeneous and heterogeneous nu-cleation (e.g., Cirisan et al, 2014). For any specific cloud scene, unless there are in situ measurements, there is either no or incomplete knowledge of the number of ice nuclei, the intensity of small-scale temperature fluctuations, or the corresponding accurate values of upper tropospheric humidity (e.g., Rolf et al, 2012;Ickes et al, 2015;Kienast-Sjögren et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements

et al. 2016

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Abstract. Cirrus, i.e., high, thin clouds that are fully glaciated, play an important role in the Earth's radiation budget as they interact with both long-and shortwave radiation and affect the water vapor budget of the upper troposphere and stratosphere. Here, we present a climatology of midlatitude cirrus clouds measured with the same type of ground-based lidar at three midlatitude research stations: at the Swiss high alpine Jungfraujoch station (3580 m a.s.l.), in Zürich (Switzerland, 510 m a.s.l.), and in Jülich (Germany, 100 m a.s.l.). The analysis is based on 13 000 h of measurements from 2010 to 2014. To automatically evaluate this extensive data set, we have developed the Fast LIdar Cirrus Algorithm (FLICA), which combines a pixel-based clouddetection scheme with the classic lidar evaluation techniques. We find mean cirrus optical depths of 0.12 on Jungfraujoch and of 0.14 and 0.17 in Zürich and Jülich, respectively.Above Jungfraujoch, subvisible cirrus clouds (τ < 0.03) have been observed during 6 % of the observation time, whereas above Zürich and Jülich fewer clouds of that type were observed. Cirrus have been observed up to altitudes of 14.4 km a.s.l. above Jungfraujoch, whereas they have only been observed to about 1 km lower at the other stations. These features highlight the advantage of the high-altitude station Jungfraujoch, which is often in the free troposphere above the polluted boundary layer, thus enabling lidar measurements of thinner and higher clouds. In addition, the measurements suggest a change in cloud morphology at Jungfraujoch above ∼ 13 km, possibly because high particle number densities form in the observed cirrus clouds, when many ice crystals nucleate in the high supersaturations following rapid uplifts in lee waves above mountainous terrain.The retrieved optical properties are used as input for a radiative transfer model to estimate the net cloud radiative forcing, CRF NET , for the analyzed cirrus clouds. All cirrus detected here have a positive CRF NET . This confirms that these thin, high cirrus have a warming effect on the Earth's climate, whereas cooling clouds typically have cloud edges too low in altitude to satisfy the FLICA criterion of temperatures below −38 • C. We find CRF NET = 0.9 W m −2 for Jungfraujoch and 1.0 W m −2 (1.7 W m −2 ) for Zürich (Jülich). Further, we calculate that subvisible cirrus (τ < 0.03) contribute about 5 %, thin cirrus (0.03 < τ < 0.3) about 45 %, and opaque cirrus (0.3 < τ ) about 50 % of the total cirrus radiative forcing.

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“…Kienast‐Sjögren et al. () inferred a statistic of mean vertical wind speed variance from ascent data of 71 sounding balloons. The statistic is representative of the region in the vicinity of Zurich and encompasses data taken over a period of 5 years, confirming that mean variances in the same area can be highly variable.…”

Section: Mesoscale Temperature Fluctuationsmentioning

confidence: 99%

“…Kienast‐Sjögren et al. () present a comprehensive analysis of temperature and vertical wind velocity PSDs for areas over Switzerland from numerical weather prediction model‐derived trajectories at variable horizontal and temporal resolution. The trajectories are used in conjunction with a Lagrangian cloud model constrained with measured vertical profiles of cirrus optical extinction.…”

Section: Mesoscale Temperature Fluctuationsmentioning

confidence: 99%

A Stochastic Representation of Temperature Fluctuations Induced by Mesoscale Gravity Waves

Kärcher

Podglajen

2019

JGR Atmospheres

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Ubiquitous mesoscale gravity waves generate high cooling rates important for cirrus formation. We make use of long‐duration balloon observations to devise a probabilistic model describing mesoscale temperature uctuations (MTF) away from strong wave sources. We define background conditions based on observed probability distributions of temperature and underlying vertical wind speed fluctuations. We show theoretically that MTF are subject to damping at a rate near the Coriolis frequency when the vertical wind speed fluctuations are autocorrelated over a fraction of a Brunt‐Väisälä period. We find that for background wave activity, a decrease in temperature of 1K translates into cooling rate standard deviations and mean updraft speeds of 4–8Kh−1 and ≈ 10–20 cms−1, respectively, depending on latitude and stratification. We introduce an effective Coriolis frequency to generate cooling rates in equatorial regions consistent with balloon data. Above ice saturation, MTF are large enough to affect ice crystal nucleation. Our results help constrain uncertainty in aerosol‐cirrus interactions, provide insights to better meet challenges in comparing measurement data with model simulations, and support the development of cutting‐edge ice cloud schemes in global models.

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Sensitivities of Lagrangian modelling of mid-latitude cirrus clouds to trajectory data quality

Cited by 15 publications

References 76 publications

A microphysics guide to cirrus clouds – Part 1: Cirrus types

A microphysics guide to cirrus clouds – Part 1: Cirrus types

Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements

A Stochastic Representation of Temperature Fluctuations Induced by Mesoscale Gravity Waves

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