Arctic polar stratospheric clouds observed with the Improved Limb Atmospheric Spectrometer during winter 1996/1997

Hayashida, Sachiko; Saitoh, Naoko; Kagawa, A.; Yokota, Tatsuya; Nakajima, H.; Sasano, Yasuhiro

doi:10.1029/2000jd900228

Cited by 30 publications

(53 citation statements)

References 42 publications

(21 reference statements)

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“…A potential improvement would be the use of color index ratio detection The advantages of this PSC detection method are (a) that the threshold for PSC detection can be determined independently with radiative transfer calculations, and (b) that no additional temperature threshold (e.g., T <200 K as in Poole and Fritts, 1994) has to be imposed. In terms of (a), the PSC detection methods applied to solar occultation measurements (Poole and Fritts, 1994;Fromm et al, 1997;Hayashida et al, 2000), require empirical aerosol extinction profiles without PSCs to determine the natural variability.…”

Section: Resultsmentioning

confidence: 99%

Detection and mapping of polar stratospheric clouds using limb scattering observations

et al. 2005

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Abstract. Satellite-based measurements of Visible/NIR limb-scattered solar radiation are well suited for the detection and mapping of polar stratospheric clouds (PSCs). This publication describes a method to detect PCSs from limb scattering observations with the Scanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIA-MACHY) on the European Space Agency's Envisat spacecraft. The method is based on a color-index approach and requires a priori knowledge of the stratospheric background aerosol loading in order to avoid false PSC identifications by stratospheric background aerosol. The method is applied to a sample data set including the 2003 PSC season in the Southern Hemisphere. The PSCs are correlated with coincident UKMO model temperature data, and with very few exceptions, the detected PSCs occur at temperatures below 195-198 K. Monthly averaged PSC descent rates are about 1.5 km/month for the −50 • S to −75 • S latitude range and assume a maximum between August and September with a value of about 2.5 km/month. The main cause of the PSC descent is the slow descent of the lower stratospheric temperature minimum.

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Section: Resultsmentioning

confidence: 99%

Detection and mapping of polar stratospheric clouds using limb scattering observations

et al. 2005

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“…PSCs 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 temperatures warmer than 200 K were calculated for each 10-day period and for each altitude level from April to October in 2003.…”

Section: Psc Identification and Tnat Calculationmentioning

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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“…Next, they applied the PSC detection criteria, which included a 3-median deviation enhancement (plus SAM error) threshold and a temperature threshold (T < 200 K). Hayashida et al [2000] used a method based on PP94 for detecting PSCs using ILAS 780 nm Arctic extinction in 1996/97. F97 constructed an Antarctic PSC data set (1994 -1996) from POAM II 1 mm extinction profiles using an automated algorithm similar to PP94.…”

Section: Mccormick Et Almentioning

confidence: 99%

“…Fromm et al [1997] (hereinafter referred to as F97) and Fromm et al [1999] (hereinafter referred to as F99) added to the PSC climatology with an analysis of 3 years (1993)(1994)(1995)(1996) of POAM II data. Hayashida et al [2000] described 1996/1997 Arctic PSC occurrence using the Improved Limb Atmospheric Spectrometer (ILAS) [Sasano et al, 1995]. These combined results, though valuable, still represent a disjoint survey of the available satellite observation PSC record.…”

Section: Introductionmentioning

confidence: 99%

A unified, long‐term, high‐latitude stratospheric aerosol and cloud database using SAM II, SAGE II, and POAM II/III data: Algorithm description, database definition, and climatology

2003

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A 22 year, high‐latitude, stratospheric aerosol and cloud database has been formed in a “unified” manner by combining the Stratospheric Aerosol Measurement (SAM) II, Stratospheric Aerosol and Gas Measurement (SAGE) II, Polar Ozone and Aerosol Measurement (POAM) II, and POAM III 1 μm aerosol extinction profiles. The database is “unified” in that it embodies similar aerosol extinction measurements, uses a single meteorological data set, and employs a single algorithm for calculating background extinction and cloud detection thresholds. Latitude is constrained to poleward of 45° in each hemisphere. The Unified cloud detection algorithm and database are designed for the straightforward addition of new data when other compatible data sets (e.g., SAGE III) become available. “Unified” cloud detection is similar to, but a refinement of, earlier attempts to identify polar stratospheric clouds (PSCs) with SAM II and POAM II data. The Unified algorithm is instrument‐independent and circumvents fundamental cloud detection pitfalls. The database contains over 73,000 (36,000) polar vortex‐region profiles in the Antarctic (Arctic) and over 21,000 (2000) PSC observations. An introductory climatology of Unified “background” extinction is presented. It is seen that volcanic effects dominate the evolution of outside‐vortex background extinctions, but perturbations apparently not related to volcanoes are seen as well. Interannual variations of background extinction inside the austral vortex are seen to be nearly decoupled from volcanic effects, while in the Arctic, inside‐vortex extinctions show a considerable volcanic influence. An analysis of long‐term PSC sighting is presented. Midwinter (July and January) PSC and clear‐sky measurements at 20 km, in a fixed temperature range, are used for computing PSC probability. The grand average PSC probability calculated this way is nearly identical between hemispheres. In the Antarctic the interannual PSC probability pattern is distinctly cyclic but is convoluted by volcanic perturbations in background aerosol. In the Arctic the PSC probability has much less temporal coherence than in the Antarctic but is similarly impacted by volcanic background increases. An explanation for the variation in PSC probabilities, in terms of interannual differences in denitrification, is discussed. Finally, a statistical analysis of tropopause height in relation to PSC formation is also presented. PSC observations are seen to be strongly associated with elevated tropopause heights, indicating that tropospheric, synoptic‐scale flow perturbations are the primary forcing mechanism for Arctic PSC formation, as evidenced in this long‐term satellite record.

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Arctic polar stratospheric clouds observed with the Improved Limb Atmospheric Spectrometer during winter 1996/1997

Cited by 30 publications

References 42 publications

Detection and mapping of polar stratospheric clouds using limb scattering observations

Detection and mapping of polar stratospheric clouds using limb scattering observations

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

A unified, long‐term, high‐latitude stratospheric aerosol and cloud database using SAM II, SAGE II, and POAM II/III data: Algorithm description, database definition, and climatology

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