A Stochastic Representation of Temperature Fluctuations Induced by Mesoscale Gravity Waves
TLDR
In this article, the authors make use of long-duration balloon observations to devise a probabilistic model describing mesoscale temperature uctuations (MTF) away from strong wave sources and show 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.Abstract:
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 and ≈ 10–20 cms, 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. Plain Language Summary: The limited scientific understanding of pure ice clouds (cirrus)—and therefore the difficulty to account for them inmodels—causes substantial uncertainty in climate projections. Two research issues important for cirrus formation continue to form a roadblock on the path of scientific progress: the dynamical forcing driving cirrus ice crystal formation and the ice‐forming properties of solid atmospheric particles. Long‐duration balloons floating in the high atmosphere have quantified key properties of gravity waves that generate vertical air motions (cooling rates) crucial for ice formation in cirrus. Only when occurrence and magnitude of cooling rates are well understood can effects of different solid and liquid ice‐forming particles during cirrus formation be predicted with confidence. Blending insights obtained from the research balloon measurements with theoretical methods developed in statistical physics, our study elaborates on the dynamical forcing issue by devising a model that represents air parcel cooling rates on a probabilistic basis. We thereby hope to contribute significantly to a comprehensive process understanding and, ultimately, to removing one of the roadblocks in cloud research.read more
Citations
More filters
Journal ArticleDOI
Developing a Cloud Scheme With Prognostic Cloud Fraction and Two Moment Microphysics for ECHAM-HAM
Steffen Muench,Ulrike Lohmann +1 more
Journal ArticleDOI
Process-oriented analysis of aircraft soot-cirrus interactions constrains the climate impact of aviation
TL;DR: In this article, the authors used a high-resolution cirrus column model to investigate how aircraft-emitted soot particles, released after ice crystals sublimate at the end of the lifetime of contrails and contrail cirrus, perturb the formation of cirrus.
Studies on the Competition Between Homogeneous and Heterogeneous Ice Nucleation in Cirrus Formation
TL;DR: In this paper , the reduction of ice crystal numbers produced by homogeneous freezing due to ice-nucleating particles (INPs) in both, individual simulations assuming constant updraft speeds and in ensemble simulations based on a stochastic representation of vertical wind speed fluctuations.
Journal ArticleDOI
Lagrangian gravity wave spectra in the lower stratosphere of current (re)analyses
TL;DR: In this paper, an assessment of the gravity wave spectrum as a function of the intrinsic (air parcel following) frequency in recent (re)analyses (ERA-Interim, ERA5, the ECMWF operational analysis and MERRA-2).
References
More filters
An introduction to dynamic meteorology
TL;DR: The instructor's manual to a work which introduces the fundamental principles of meteorology, explaining storm dynamics and the dynamics of climate and its global implications is described in this paper, where the authors present a detailed discussion of the relationship between meteorology and climate.
Journal ArticleDOI
Quasi-geostrophic motions in the equatorial area
TL;DR: In this article, a single layer of homogeneous incompressible fluid with free surface is treated, where the Coriolis parameter is assumed to be proportional to the latitude, and a strong east-west current was formed along the equator.
Journal ArticleDOI
Gravity wave dynamics and effects in the middle atmosphere
TL;DR: In this article, a review of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape are discussed.
Journal ArticleDOI
Convectively-coupled equatorial waves
TL;DR: In this paper, the authors used convectively coupled equatorial waves (CCEWs) to simulate tropical rainfall variability in the equatorial beta plane of a tropical weather system, and found that CCEWs display a large degree of self-similarity over a surprisingly wide range of scales.