Indicator 12 - Noctilucent cloud observations at DavisIndex - Description | Data | Custodian evaluation | Related resources | Parameters |
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| Indicator Definition | Lidar observations at Davis Station, Antarctica, are used to determine monthly averages of 'percentage of time noctilucent clouds detected' (i.e. total time clouds detected divided by total observing time, as a percentage), and monthly averages of median altitude of noctilucent clouds. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Responsible Organisation |
 Australian Antarctic Division (details) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Custodians |
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| Theme Area | Atmosphere | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Indicator Type | Condition | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Criteria the Indicator Satisfies |
The following 8 out of 15 criteria
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| Date Input | Monthly measurements | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Monitoring Location |
Davis (details)
Geographic Coverage is
Longitude (78.0 to 78.0)
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| Rationale For Indicator Selection | Increases in occurrence and spatial extent of noctilucent clouds in the Northern Hemisphere have been linked to cooling of the mesopause region related to enhanced greenhouse warming of the troposphere, and increases in tropospheric methane. Both of these effects have anthropogenic sources. Southern Hemisphere observations of noctilucent clouds are sparse, but potentially provide an independent data set to the Northern Hemisphere observations. A long-term consistent data set is required to determine variations in percentage occurrence and compare this to northern hemisphere observations, particularly as there are subtle differences in the characteristics of the atmosphere in the two hemispheres. Perturbations to the thermodynamics and chemistry of the mesopause region can conceivably be caused by volcanic events and variations in solar activity. Long-term quantification of noctilucent 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: Monthly values. Measurement technique: Lidar (532nm wavelength, minimum altitude resolution 18.7 metres). The raw data used in the analysis of this indicator are obtained from observations by the Davis Lidar in Rayleigh mode. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Research Issues | Changes in the extent and occurrence of noctilucent clouds have implications for the chemistry and climate of the mesopause region. 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 the remote sensing of temperatures and winds in the mesopause region, from instruments at Davis such as the Czerny-Turner spectrometer, the MF radar and the proposed VHF radar, and other Antarctic measurements. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Data |
Timespan: January-2001 to April-2002. Number of data points: 34. 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: Noctilucent cloud observations  Davis: Noctilucent Cloud Height - Upper 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 mode. 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 or 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. 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. Enhancements in the scattering ratio greater than 1.05 with greater than 1-standard deviation statistical significance in the altitude range 85-95km are classed as cloud features. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Data Distribution |
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| Data Access Constraints | These data are publicly available for download from the URL given below. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Custodian Evaluation |
For definitions of the Scale categories, consult the Explanation of the Status Categories | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Related resources |
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| Parameters |
The properties link can be used to view details of the parameters measured for this indicator.
Parameters - | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
