Particle microphysics and chemistry in remotely observed mountain polar stratospheric clouds

Carslaw, K. S.; Wirth, Martin; Tsias, A.; Luo, B. P.; Dörnbrack, Andreas; Leutbecher, Martin; Volkert, Hans; Renger, W.; Bacmeister, Julio T.; Peter, Thomas

doi:10.1029/97jd03626

Cited by 177 publications

(277 citation statements)

References 37 publications

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“…The ice PSCs are formed at synoptic-scale temperatures of up to 4-10 K above T ice . NAT particles are observed further downstream of the Antarctic Peninsula, which is consistent with the ice particles serving as condensation nuclei for NAT formation (Carslaw et al, 1998a;Höpfner et al, 2006b;Eckermann et al, 2009). Although mountain wave activity is most frequent at the Antarctic Peninsula (Hoffmann et al, 2016a), other orographic features in Antarctica can also play a role in PSC formation.…”

Section: A Survey Of Gravity-wave-induced Psc Formation Eventssupporting

confidence: 64%

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

et al. 2017

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Abstract. Atmospheric gravity waves yield substantial small-scale temperature fluctuations that can trigger the formation of polar stratospheric clouds (PSCs). This paper introduces a new satellite record of gravity wave activity in the polar lower stratosphere to investigate this process. The record is comprised of observations of the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite from January 2003 to December 2012. Gravity wave activity is measured in terms of detrended and noise-corrected 15 µm brightness temperature variances, which are calculated from AIRS channels that are the most sensitive to temperature fluctuations at about 17-32 km of altitude. The analysis of temporal patterns in the data set revealed a strong seasonal cycle in wave activity with wintertime maxima at mid-and high latitudes. The analysis of spatial patterns indicated that orography as well as jet and storm sources are the main causes of the observed waves. Wave activity is closely correlated with 30 hPa zonal winds, which is attributed to the AIRS observational filter. We used the new data set to evaluate explicitly resolved temperature fluctuations due to gravity waves in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis. It was found that the analysis reproduces orographic and non-orographic wave patterns in the right places, but that wave amplitudes are typically underestimated by a factor of 2-3. Furthermore, in a first survey of joint AIRS and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite observations, nearly 50 gravity-wave-induced PSC formation events were identified. The survey shows that the new AIRS data set can help to better identify such events and more generally highlights the importance of the process for polar ozone chemistry.

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Section: A Survey Of Gravity-wave-induced Psc Formation Eventssupporting

confidence: 64%

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

et al. 2017

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“…Figure 1c depicts the averaged differences between temperatures at ILAS-II measurement locations inside the polar vortex and the corresponding TNAT as white contour lines of T. Temperatures at 22 km in June were 0 2 K warmer on average than TNAT. It is well-known that STS droplets form at 3 5 K colder than TNAT (e.g., Carslaw et al 1994), and NAT particles would also form at temperatures several degrees colder than TNAT (Tabazadeh et al 2001) or at even lower temperatures (Carslaw et al 1998). Therefore, a high probability of PSC formation (PPSC) cannot be anticipated in June even though PT(NAT) was relatively large.…”

Section: Discussionmentioning

confidence: 99%

Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

Saitoh

Hayashida

Sugita

et al. 2006

SOLA

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The Improved Limb Atmospheric Spectrometer (ILAS)-II frequently observed polar stratospheric clouds (PSCs) in the Southern Hemisphere (SH) throughout the winter of 2003. Simultaneous observations of the aerosol extinction coefficient (AEC) at 780 nm, nitric acid, and water vapor data were analyzed to investigate the ambient thermodynamic conditions associated with observed PSCs. PSCs were first observed with ILAS-II at the end of May, and observed most frequently in August/September as temperatures cooled. At approximately 20 km late in the PSC season, however, PSCs were less likely to occur, despite cold temperatures, because of the lower concentration of nitric acid due to denitrification caused by sedimentation of previously occurring PSCs. The probability of PSC occurrence and the probability of ambient temperatures colder than nitric acid trihydrate (NAT) saturation temperature (TNAT ) were well correlated below 20 km throughout the winter. In contrast, PSC frequency at 22 km from late August to early September was low even when temperatures were sufficiently colder than TNAT; this is, at least, partly because of the decrease in background aerosol particles in the atmosphere. IntroductionPolar stratospheric clouds (PSCs) consist mainly of nitric acid and water/ice and form in winter and early spring in the lower stratosphere over both polar regions (e.g., Solomon 1999). PSCs play a crucial role in ozone depletion processes; they provide surfaces for heterogeneous reactions that convert inactive chlorine into active chorine (e.g., Solomon 1999) and cause denitrification (e.g., Fahey et al. 1990) and nitrification (e.g., H ubler et al. 1990). Activated chlorine causes severe ozone depletion, especially in the Southern Hemisphere (SH), which is known as the "ozone hole". The climatology of PSC frequency in the SH was examined using aerosol data from the Stratospheric Aerosol Measurement (SAM) II from 1978to 1989(Poole and Pitts 1994, data from the Polar Ozone and Aerosol Measurement (POAM) II from 1994 to 1996 (Fromm et al. 1997), and data from multiple solar occultation sensors from 1978 to 2000 .Poole and Pitts (1994) examined the relationship between PSC frequency and temperature and showed that PSC formation in the SH is less likely later in PSC season than earlier. Other studies (e.g., Watterson and Tuck 1989;Hervig et al. 1997;Mergenthaler et al. 1997) have suggested that PSC formation late in PSC season in the SH is strongly affected by preceding denitrification and dehydration. However, there have been few studies on the variability of the relationship between PSC frequency and temperature over the course of a PSC season that are based on extensive observations of aerosols, nitric acid, and water vapor in the SH.Against this background, we used data obtained by the PSC identification and TNAT calculationPSCs were identified from ILAS-II AEC data over the SH using methods similar to those for ILAS data in the NH (Hayashida et al. 2000). First, averages and standard deviations for ILAS-II AEC data at te...

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“…Aspherical particles, such as ice crystals, are approximated as prolate ("cigar-like") spheroids with aspect ratio A = a/b (the ratio of the equatorial to polar lengths) and volume V = 4/3 π a 2 b, which is set equal to the volume of the ice particles calculated by the microphysical model. Calculations were then made using a T-matrix light scattering algorithm (Mishchenko, 1991;Carslaw et al, 1998) with a refractive index of ice of 1.31 at 455 and 870 nm with spheroid shape. The ice particles are clearly aspherical.…”

Section: Microphysical/optical Column Modelmentioning

confidence: 99%

Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling

et al. 2012

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Abstract. Advanced measurement and modelling techniques are employed to estimate the partitioning of atmospheric water between the gas phase and the condensed phase in and around cirrus clouds, and thus to identify in-cloud and outof-cloud supersaturations with respect to ice. In November 2008 the newly developed balloon-borne backscatter sonde COBALD (Compact Optical Backscatter and AerosoL Detector) was flown 14 times together with a CFH (Cryogenic Frost point Hygrometer) from Lindenberg, Germany (52 • N, 14 • E). The case discussed here in detail shows two cirrus layers with in-cloud relative humidities with respect to ice between 50 % and 130 %. Global operational analysis data of ECMWF (roughly 1 • × 1 • horizontal and 1 km vertical resolution, 6-hourly stored fields) fail to represent ice water contents and relative humidities. Conversely, regional COSMO-7 forecasts (6.6 km × 6.6 km, 5-min stored fields) capture the measured humidities and cloud positions remarkably well. The main difference between ECMWF and COSMO data is the resolution of small-scale vertical features responsible for cirrus formation. Nevertheless, ice water contents in COSMO-7 are still off by factors 2-10, likely reflecting limitations in COSMO's ice phase bulk scheme. Significant improvements can be achieved by comprehensive size-resolved microphysical and optical modelling along backward trajectories based on COSMO-7 wind and temperature fields, which allow accurate computation of humidities, homogeneous ice nucleation, resulting ice particle size distributions and backscatter ratios at the COBALD wavelengths. However, only by superimposing small-scale temperature fluctuations, which remain unresolved by the numerical weather prediction models, can we obtain a satisfying agreement with the observations and reconcile the measured in-cloud nonequilibrium humidities with conventional ice cloud microphysics. Conversely, the model-data comparison provides no evidence that additional changes to ice-cloud microphysics -such as heterogeneous nucleation or changing the water vapour accommodation coefficient on ice -are required.

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Particle microphysics and chemistry in remotely observed mountain polar stratospheric clouds

Cited by 177 publications

References 37 publications

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling

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