State of Environment

Indicator 13 - Polar stratospheric cloud observations at Davis

Index - Description | Data | Custodian evaluation | Related resources | Parameters

Stratospheric cloud at Stevenson Glacier, Heard Island (AAD Photo 1884/ A3) by Unknown

Indicator Definition

Lidar observations at Davis Station, Antarctica, are used to determine
daily values of average percentage occurrence and upper and lower altitude
limits for Polar Stratospheric Clouds. The occurrence values are evaluated
from the total time clouds were detected divided by total observing time,
expressed as a percentage. The altitude limits are the maximum and minimum
altitudes at which clouds were detected during the time interval.

Responsible
Organisation

Australian Antarctic Division (details)

Custodians

ANDREW KLEKOCIUK
andrew.klekociuk@aad.gov.au

INVESTIGATOR
TECHNICAL CONTACT

203 Channel Highway
Australian Antarctic Division
Kingston
Tasmania 7050
Australia
Ph +61 3 6232 3382

Theme Area

Atmosphere

Indicator Type

Condition

Criteria the
Indicator Satisfies

The following 8 out of 15 criteria

1.	Serve as a robust indicator of environmental change
6.	Be scientifically credible
7.	Be easy to understand
9.	Be cost-effective
10.	Have relevance to policy and management needs
11.	Contribute to monitoring of progress towards implementing commitments in nationally important environmental policies
13.	Contribute to the fulfillment of reporting obligations under international agreements
15.	Where possible and appropriate, be consistent and comparable with other countries’ and state and territory indicators

For details of indicators, see the State of Environment Bibliography entries 16336 and 16337

Date Input

Daily measurements

Monitoring Location

Davis (details)

Geographic Coverage is

Rationale For Indicator Selection

The formation of stratospheric clouds in the polar regions requires special
conditions relating to temperature and chemistry. The clouds play a
critical role in the depletion of ozone at high latitudes by initiating
heterogeneous chemical reactions that convert chlorine and bromine
compounds to reactive forms. A general cooling of the stratosphere is
predicted to accompany anthropogenically enhanced greenhouse-gas warming of
the lower atmosphere. This may provide conditions more favourable for the
formation of stratospheric clouds. However, perturbations to stratospheric
thermodynamics and chemistry can be caused by volcanic events. Long-term
quantification of stratospheric cloud properties will aid in understanding
and predicting natural and anthropogenic variability.

Design and Strategy For Indicator Monitoring Program

Spatial scale: Davis Station, Antarctica.

Temporal scale: Values for every day of lidar operation.

Measurement technique: Lidar (532nm wavelength). The raw data used in the
analysis of this indicator are obtained from observations by the Davis Lidar
in Rayleigh and Doppler modes. In Rayleigh mode, the raw data consist of
profiles of the intensity of 532nm laser backscatter versus altitude. In
Doppler mode, spectral scans of 532nm laser backscatter versus altitude are
obtained with a high-resolution Fabry-Perot spectrometer. These measurements
are used to obtain the total backscatter versus altitude by collapsing the
wavelength data down to one bin.

Research Issues

Changes in the extent and occurrence of stratospheric clouds has
implications for the chemistry, structure and dynamics of the lower
stratosphere. To obtain a more comprehensive picture of the spatial extent
of these changes, the underlying physics, and future implications, the
Davis observations should be assimilated into research incorporating a
diverse body of observations and model predictions. Important additional
data will come from in-situ and remote-sensing profiling of trace gas
species (importantly, ozone, and compounds of nitrogen, chlorine, bromine
and sulphur) and the thermal and dynamical behaviour of the atmosphere.

Data

Timespan: 14-February-2001 to 30-December-2001.
Number of data points: 148.

To view or download any of the data, you must be logged into the Data Centre Portal. If you return to this indicator, you will find a Search Data link that will allow you to view or extract the data for this indicator.

Davis: Polar Stratospheric cloud observations

Davis: Polar Stratospheric Cloud Height - Upper Layer

Davis: Time spent on observations

Davis: Polar Stratospheric Cloud Height - Lower Layer

Data Quality, Interpretation and
Analysis of Indicator Data

The raw data used in the analysis of this indicator are obtained from observations by the Davis Lidar in Rayleigh and Doppler modes. In Rayleigh mode, the raw data consist of profiles of the intensity of 532nm laser backscatter versus altitude. The backscatter profiles are converted to profiles of absolute total molecular density using in-situ or extrapolated density measurements for the altitude range 27-28km obtained from balloon-borne radiosonde measurements. In producing the density profiles, account is made for molecular extinction, including ozone, and background signals due to sky light and instrument noise.

In Doppler mode, spectral scans of 532nm laser backscatter versus altitude are obtained with a high-resolution Fabry-Perot spectrometer. These measurements are used to obtain the total backscatter versus altitude by collapsing the wavelength data down to one bin. Profiles of absolute total molecular density are then obtained using the analysis scheme used for the Rayleigh mode data.

Profiles of Rayleigh scattering ratio are generated with 1 hour time binning and 100 metre altitude binning. The scattering ratio is defined as the ratio of the lidar-derived density profile divided by the total molecular density profile obtained from the MSISE-90 atmospheric model. The scattering ratio profile is generally greater than unity below about 27km where scattering by stratospheric aerosols contaminates the lidar-derived density profile. The 'background' scattering ratio profile due to the normal (i.e. cloud-free) loading of stratospheric aerosols (averaged over the month preceeding the first occurrence of stratospheric clouds for the winter season - typically May) is removed. Enhancements in the residual scattering ratio with greater than 2-standard deviation statistical significance are classed as cloud features.

Data Distribution

DATA OFFICER AADC
metadata@aad.gov.au

Australian Antarctic Division
203 Channel Highway
Kingston
Tasmania 7050
Australia
Ph +61 3 6232 3244

Data Access Constraints

These data are publicly available for download from the URL given below.

Custodian Evaluation

Date entered

Evaluation

23-May-2002

PSCs were detected by the Davis lidar between 04 July and 22 September 2001. Analysis is underway to quantify the occurence and altitude parameters of the clouds.

8-Nov-2002

Condition scale - 4 - fair condition

1 - the environment degraded to the point where rehabilitation is impossible

0	1	2	3	4	5	6	7

7 - the environment is pristine, in perfect condition, no anthropogenic influences

State of Knowledge scale - 6

1 - Poor

0	1	2	3	4	5	6	7

7 - Excellent

For definitions of the Scale categories, consult the Explanation of the Status Categories

Related resources

Metadata SOE_PSC - Polar Stratospheric Cloud observations at Davis

Project 737 - Lidar studies of atmospheric dynamics, composition and climatology

Scientific Bibliography 17310 - Klekociuk, A.R. (2001) Rayleigh LIDAR measurements of mean stratopause region temperatures above Kingston, Tasmania (43.00S, 147.30E) betweeen March 1997 and April 1999. ANARE Report 146, Australian solar terrestrial and space physics research Edited by R.J. Morris and P.J. Wilkinson. Available online at the url below.

SOE Indicator 4 - Monthly mean lower stratospheric temperatures above Australian Antarctic Stations

SOE Indicator 5 - Monthly mean mid-tropospheric temperatures above Australian Antarctic Stations

SOE Indicator 9 - Daily records of total column ozone at Macquarie Island

SOE Indicator 14 - Midwinter atmospheric temperature at altitude 87km

SOE Indicator 15 - Stratopause region parameters for Davis

Parameters

The properties link can be used to view details of the parameters measured for this indicator.

Parameter Name	Unit of measure	Properties
Polar Stratospheric Cloud Height - Lower Layer	km	(properties)
Polar Stratospheric Cloud Height - Upper Layer	km	(properties)
Polar Stratospheric cloud observations	%	(properties)
Time spent on observations	%	(properties)

The following parameters and/or sensor notes are from the metadata record.

Parameters -
EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD AMOUNT/FREQUENCY
EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD HEIGHT
EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD VERTICAL DISTRIBUTION

Related URL's

http://data.aad.gov.au/aadc/portal/download_file.cfm?file_id=2271
Download point for the data - pdf copy of chapter 26 of ANARE Report 146

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SIMR - (State of Environment)

State of Environment

Indicator 13 - Polar stratospheric cloud observations at Davis