scholarly journals Detection and mapping of polar stratospheric clouds using limb scattering observations

2005 ◽  
Vol 5 (4) ◽  
pp. 7169-7190 ◽  
Author(s):  
C. von Savigny ◽  
E. P. Ulasi ◽  
K.-U. Eichmann ◽  
H. Bovensmann ◽  
J. P. Burrows
Keyword(s):  
A Priori ◽  
Polar Stratospheric Clouds ◽  
Data Set ◽  
Latitude Range ◽  
Stratospheric Temperature ◽  
A Value ◽  
Index Approach ◽  
Sample Data ◽  
Scanning Imaging ◽  
Stratospheric Clouds

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 (SCIAMACHY) 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.

scholarly journals Detection and mapping of polar stratospheric clouds using limb scattering observations

2005 ◽  
Vol 5 (11) ◽  
pp. 3071-3079 ◽  
Author(s):  
C. von Savigny ◽  
E. P. Ulasi ◽  
K.-U. Eichmann ◽  
H. Bovensmann ◽  
J. P. Burrows
Keyword(s):  
A Priori ◽  
Polar Stratospheric Clouds ◽  
Data Set ◽  
Latitude Range ◽  
Stratospheric Temperature ◽  
A Value ◽  
Index Approach ◽  
Sample Data ◽  
Scanning Imaging ◽  
Stratospheric Clouds

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 (SCIAMACHY) 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.

scholarly journals Effects of polar stratospheric clouds in the Nimbus 7 LIMS Version 6 data set

2016 ◽  
Vol 9 (7) ◽  
pp. 2927-2946 ◽  
Author(s):  
Ellis Remsberg ◽  
V. Lynn Harvey
Keyword(s):  
Stratospheric Aerosol ◽  
Transport Processes ◽  
The Arctic ◽  
Additional Parameter ◽  
Polar Stratospheric Clouds ◽  
Data Set ◽  
Screening Criteria ◽  
Temperature Thresholds ◽  
Level 3 ◽  
Stratospheric Clouds

Abstract. The historic Limb Infrared Monitor of the Stratosphere (LIMS) measurements of 1978–1979 from the Nimbus 7 satellite were re-processed with Version 6 (V6) algorithms and archived in 2002. The V6 data set employs updated radiance registration methods, improved spectroscopic line parameters, and a common vertical resolution for all retrieved parameters. Retrieved profiles are spaced about every 1.6° of latitude along orbits and include the additional parameter of geopotential height. Profiles of O3 are sensitive to perturbations from emissions of polar stratospheric clouds (PSCs). This work presents results of implementing a first-order screening for effects of PSCs using simple algorithms based on vertical gradients of the O3 mixing ratio. Their occurrences are compared with the co-located, retrieved temperatures and related to the temperature thresholds needed for saturation of H2O and/or HNO3 vapor onto PSC particles. Observed daily locations where the major PSC screening criteria are satisfied are validated against PSCs observed with the Stratospheric Aerosol Monitor (SAM) II experiment also on Nimbus 7. Remnants of emissions from PSCs are characterized for O3 and HNO3 following the screening. PSCs may also impart a warm bias in the co-located LIMS temperatures, but by no more than 1–2 K at the altitudes of where effects of PSCs are a maximum in the ozone; thus, no PSC screening was applied to the V6 temperatures. Minimum temperatures vary between 187 and 194 K and often occur 1 to 2 km above where PSC effects are first identified in the ozone (most often between about 21 and 28 hPa). Those temperature–pressure values are consistent with conditions for the existence of nitric acid trihydrate (NAT) mixtures and to a lesser extent of super-cooled ternary solution (STS) droplets. A local, temporary uptake of HNO3 vapor of order 1–3 ppbv is indicated during mid-January for the 550 K surface. Seven-month time series of the distributions of LIMS O3 and HNO3 are shown based on their gridded Level 3 data following the PSC screening. Zonal coefficients of both species are essentially free of effects from PSCs on the 550 K surface, based on their average values along PV contours and in terms of equivalent latitude. Remnants of PSCs are still present in O3 on the 450 K surface during mid-January. It is judged that the LIMS Level 3 data are of good quality for analyzing the larger-scale, stratospheric chemistry and transport processes during the Arctic winter of 1978–1979.

scholarly journals Polar Stratospheric Clouds Detection at Belgrano II Antarctic Station with Visible Ground-Based Spectroscopic Measurements

2021 ◽  
Vol 13 (8) ◽  
pp. 1412
Author(s):  
Laura Gomez-Martin ◽  
Daniel Toledo ◽  
Cristina Prados-Roman ◽  
Jose Antonio Adame ◽  
Hector Ochoa ◽  
...  
Keyword(s):  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Polar Stratospheric Clouds ◽  
Meteorological Model ◽  
Weather Forecasts ◽  
Stratospheric Temperature ◽  
Medium Range ◽  
Stratospheric Clouds ◽  
Good Agreement

By studying the evolution of the color index (CI) during twilight at high latitudes, polar stratospheric clouds (PSCs) can be detected and characterized. In this work, this method has been applied to the measurements obtained by a visible ground-based spectrometer and PSCs have been studied over the Belgrano II Antarctic station for years 2018 and 2019. The methodology applied has been validated by full spherical radiative transfer simulations, which confirm that PSCs can be detected and their altitude estimated with this instrumentation. Moreover, our investigation shows that this method is useful even in presence of optically thin tropospheric clouds or aerosols. PSCs observed in this work have been classified by altitude. Our results are in good agreement with the stratospheric temperature evolution obtained by the global meteorological model ECMWF (European Centre for Medium Range Weather Forecasts) and with satellite PSCs observations from CALIPSO (Cloud-Aerosol-Lidar and Infrared Pathfinder Satellite Observations). To investigate the presence and long-term evolution of PSCs, the methodology used in this work could also be applied to foreseen and/or historical observations obtained with ground-based spectrometers such e. g. those dedicated to Differential Optical Absorption Spectroscopy (DOAS) for trace gas observation in Arctic and Antarctic sites.

scholarly journals Improved interpretation of studies comparing methods of dietary assessment: combining equivalence testing with the limits of agreement

2016 ◽  
Vol 115 (7) ◽  
pp. 1273-1280 ◽  
Author(s):  
Marijka J. Batterham ◽  
Christel Van Loo ◽  
Karen E. Charlton ◽  
Dylan P. Cliff ◽  
Anthony D. Okely
Keyword(s):  
Clinical Decision Making ◽  
Dietary Assessment ◽  
A Priori ◽  
Clinical Decision ◽  
Equivalence Testing ◽  
Limits Of Agreement ◽  
Data Set ◽  
Sample Data ◽  
The Mean ◽  
Acceptable Agreement

AbstractThe aim of this study was to demonstrate the use of testing for equivalence in combination with the Bland and Altman method when assessing agreement between two dietary methods. A sample data set, with eighty subjects simulated from previously published studies, was used to compare a FFQ with three 24 h recalls (24HR) for assessing dietary I intake. The mean I intake using the FFQ was 126·51 (sd 54·06) µg and using the three 24HR was 124·23 (sd 48·62) µg. The bias was −2·28 (sd 43·93) µg with a 90 % CI 10·46, 5·89 µg. The limits of agreement (LOA) were −88·38, 83·82 µg. Four equivalence regions were compared. Using the conventional 10 % equivalence range, the methods are shown to be equivalent both by using the CI (−12·4, 12·4 µg) and the two one-sided tests approach (lower t=−2·99 (79 df), P=0·002; upper t=2·06 (79 df), P=0·021). However, we make a case that clinical decision making should be used to set the equivalence limits, and for nutrients where there are potential issues with deficiency or toxicity stricter criteria may be needed. If the equivalence region is lowered to ±5 µg, or ±10 µg, these methods are no longer equivalent, and if a wider limit of ±15 µg is accepted they are again equivalent. Using equivalence testing, acceptable agreement must be assessed a priori and justified; this makes the process of defining agreement more transparent and results easier to interpret than relying on the LOA alone.

scholarly journals The effects of atmospheric waves on the amounts of polar stratospheric clouds

2011 ◽  
Vol 11 (6) ◽  
pp. 16967-17012 ◽  
Author(s):  
M. Kohma ◽  
K. Sato
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Gravity Waves ◽  
Planetary Waves ◽  
Areal Extent ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Atmospheric Waves ◽  
Latitude Range ◽  
Stratospheric Clouds

Abstract. A quantitative analysis on the relationship between atmospheric waves and polar stratospheric clouds (PSCs) in the 2008 austral winter and the 2007/2008 boreal winter is made using CALIPSO, COSMIC and Aura MLS observation data and reanalysis data. A longitude-time section of the frequency of PSC occurrence in the Southern Hemisphere indicates that PSC frequency is not regionally uniform and that high PSC frequency regions propagate eastward at different speeds from the background zonal wind. These features suggest a significant influence of atmospheric waves on PSC behavior. Next, three temperature thresholds for PSC existence are calculated using HNO3 and H2O mixing ratios. Among the three, the TSTS (a threshold for super cooled ternary solution)-based estimates of PSC frequency accord best with the observations in terms of the amount, spatial and temporal variation, in particular for the latitude range of 55° S–70° S in the Southern Hemisphere and for 55° N–85° N in the Northern Hemisphere. Moreover, the effects of planetary waves, synoptic-scale waves and gravity waves on PSC areal extent are separately examined using the TSTS-based PSC estimates. The latitude range of 55° S–70° S is analyzed because the TSTS-based estimates are not consistent with observations at higher latitudes (< 75° S) above 18 km, and PSCs in lower latitudes are more important to the ozone depletion because of the earlier arrival of solar radiation in spring. It is shown that nearly 100 % of PSCs between 55° S and 70° S at altitudes of 16–24 km are formed by temperature modulation, which is influenced by planetary waves during winter. Although the effects of synoptic-scale waves on PSCs are limited, around an altitude of 12 km more than 60 % of the total PSC areal extent is formed by synoptic-scale waves. The effects of gravity waves on PSC areal extent are not large in the latitude range of 55° S–70° S. However, at higher latitudes, gravity waves act to increase PSC areal extent at an altitude of 15 km by about 30 % in September. Similar analyses are performed for the Northern Hemisphere. It is shown that almost all PSCs observed in the Northern Hemisphere are attributable to low temperature anomalies associated with planetary waves.

Occurrence of Polar Stratospheric Clouds using ground-based DOAS observations

2021 ◽  
Author(s):  
Bianca Lauster ◽  
Steffen Dörner ◽  
Udo Frieß ◽  
Myojeong Gu ◽  
Janis Pukite ◽  
...  
Keyword(s):  
Colour Index ◽  
Optical Absorption Spectroscopy ◽  
High Temporal Resolution ◽  
Transfer Model ◽  
Research Station ◽  
Strong Impact ◽  
Polar Stratospheric Clouds ◽  
Data Set ◽  
Spatial Coverage ◽  
Stratospheric Clouds

&lt;p&gt;Polar Stratospheric Clouds (PSCs) favour heterogeneous reactions and thus are an important component of ozone depletion processes in polar regions. Although satellite observations already yield high spatial coverage, the sampling frequency of a specific air volume depends on the measurement method. Here, continuous ground-based measurements with high temporal resolution can be a valuable complement.&lt;/p&gt;&lt;p&gt;Since 1999, a MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) instrument has been operating at the German research station Neumayer (70&amp;#176; S, 8&amp;#176; W), Antarctica. Primarily, slant column densities of trace gases such as NO&lt;sub&gt;2&lt;/sub&gt;, BrO and OClO are retrieved. However, in this study the so-called colour index (CI), i.e. the colour of the zenith sky, is investigated. Defined as the ratio between the observed intensities of scattered sun light at two wavelengths, it enables to monitor the occurrence of polar stratospheric clouds during twilight even in the presence of tropospheric clouds.&lt;/p&gt;&lt;p&gt;Using the radiative transfer model McArtim, the CI changes in the presence of polar stratospheric clouds can be analysed. Especially the height of the PSC layer affects the retrieved signal, but also the choice of the wavelengths has a strong impact. Here, it is advantageous that measurements are available in the UV and visible spectral range which allows a more extensive comparison of different CI choices. In order to assess the application of the colour index method, meteorological data are used to identify PSC cases in the data set.&lt;/p&gt;&lt;p&gt;The aim is to improve and evaluate the potential of this method. It is then used to infer the occurrence of PSCs throughout the measurement time series of more than 20 years.&lt;/p&gt;

scholarly journals The effects of atmospheric waves on the amounts of polar stratospheric clouds

2011 ◽  
Vol 11 (22) ◽  
pp. 11535-11552 ◽  
Author(s):  
M. Kohma ◽  
K. Sato
Keyword(s):  
Northern Hemisphere ◽  
Gravity Waves ◽  
Planetary Waves ◽  
Spatial And Temporal Variation ◽  
Areal Extent ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Atmospheric Waves ◽  
Latitude Range ◽  
Stratospheric Clouds

Abstract. A quantitative analysis on the relationship between atmospheric waves and polar stratospheric clouds (PSCs) in the 2008 austral winter and the 2007/2008 boreal winter is made using CALIPSO, COSMIC and Aura MLS observation data and reanalysis data. A longitude-time section of the frequency of PSC occurrence in the Southern Hemisphere indicates that PSC frequency is not regionally uniform and that high PSC frequency regions propagate eastward at different speeds from the background zonal wind. These features suggest a significant influence of atmospheric waves on PSC behavior. Next, three temperature thresholds for PSC existence are calculated using HNO3 and H2O mixing ratios. Among the three, the TSTS (a threshold for super cooled ternary solution)-based estimates of PSC frequency accord best with the observations in terms of the amount, spatial and temporal variation, in particular, for the latitude ranges of 55° S–70° S and 55° N–85° N. Moreover, the effects of planetary waves, synoptic-scale waves and gravity waves on PSC areal extent are separately examined using the TSTS-based PSC estimates. The latitude range of 55° S–70° S is analyzed because the TSTS-based estimates are not consistent with observations at higher latitudes (<75° S) above 18 km, and PSCs in lower latitudes are more important to the ozone depletion because of the earlier arrival of solar radiation in spring. It is shown that nearly 100% of PSCs between 55° S and 70° S at altitudes of 16–24 km are formed by temperature modulation, which is influenced by planetary waves during winter. Although the effects of synoptic-scale waves on PSCs are limited, around an altitude of 12 km more than 60% of the total PSC areal extent is formed by synoptic-scale waves. The effects of gravity waves on PSC areal extent are not large in the latitude range of 55° S–70° S. However, at higher latitudes, gravity waves act to increase PSC areal extent at an altitude of 15 km by about 30% in September. Similar analyses are performed for the Northern Hemisphere. It is shown that almost all PSCs observed in the Northern Hemisphere are attributable to low temperature anomalies associated with planetary waves.

scholarly journals Effects of polar stratospheric clouds in the Nimbus-7 LIMS version 6 data set

2016 ◽  
Author(s):  
Ellis Remsberg ◽  
V. Lynn Harvey
Keyword(s):  
Stratospheric Aerosol ◽  
Transport Processes ◽  
The Arctic ◽  
Additional Parameter ◽  
Polar Stratospheric Clouds ◽  
Data Set ◽  
Screening Criteria ◽  
Temperature Thresholds ◽  
Level 3 ◽  
Stratospheric Clouds

Abstract. The historic Limb Infrared Monitor of the Stratosphere (LIMS) measurements of 1978–1979 from the Nimbus 7 satellite were re-processed with Version 6 (V6) algorithms and archived in 2002. The V6 dataset employs updated radiance registration methods, improved spectroscopic line parameters, and a common vertical resolution for all retrieved parameters. Retrieved profiles are spaced about every 1.6° of latitude along orbits and include the additional parameter of geopotential height. Profiles of O3 are sensitive to perturbations from emissions of polar stratospheric clouds (PSCs). This work presents results of implementing a first-order screening for effects of PSCs using simple algorithms based on vertical gradients of the O3 mixing ratio. Their occurrences are compared with the co-located, retrieved temperatures and related to the temperature thresholds needed for saturation of H2O and/or HNO3 vapor onto PSC particles. Observed daily locations where the major PSC screening criteria are satisfied are validated against PSCs observed with the Stratospheric Aerosol Monitor (SAM) II experiment also on Nimbus 7. Remnants of emissions from PSCs are characterized for O3 and HNO3 following the screening. PSCs may also impart a warm bias in the co-located LIMS temperatures, but by no more than 1–2 K at the altitudes of where effects of PSCs are a maximum in the ozone; thus, no PSC screening was applied to the V6 temperatures. Minimum temperatures vary between 187 K and 194 K and occur at or just above where the PSC effects are first identified in the ozone (most often between about 21 hPa to 28 hPa). Those temperature-pressure values are consistent with conditions for saturation and formation of supercooled ternary solution (STS) droplets and/or nitric acid trihydrate (NAT) aerosols. A temporary uptake of HNO3 vapor by about 2–3 ppbv is indicated in mid-January downwind of and at pressure-altitudes where effects of PSCs are found. Seven-month, time series of the distributions of LIMS O3 and HNO3 are shown based on their gridded Level 3 data following the screening. The zonal coefficients of both O3 and HNO3 are essentially free of effects from PSCs on the 550 K surface as averaged at equivalent latitudes. Remnants of PSCs are still present in O3 during mid-January on the 450 K surface. It is judged that the LIMS Level 3 data are of good quality for analyzing the larger-scale, stratospheric chemistry and transport processes during the Arctic winter of 1978–1979.

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