SP1A: FULL-AUTOMATIC SUN PHOTOMETER
Purpose of Participation:
- Quantification of aerosol variability (temporal and vertical) in the European Arctic
- Derivation of the height dependent spectral aerosol extinction coefficient based on airborne measurements with POLAR 4
Instrument description:
The instrument SP1A is used for measurements of the direct solar radiation. The sun is sharply focused in a measuring diaphragm with an objective lens having a plane angle (field of view) of 1°. The optical sensor converts the incident radiation into a voltage that is amplified up to eight orders of magnitude depending on the strength of the incoming radiation. The spectral extinction coefficient for different height levels will be derived based on the AOD measurements.
| Method | Direct single solar measurements |
| Quantity primary | Spectral aerosol extinction coefficient |
| Quantity secondary | in case of brightness measurements: phase function and refractive index |
| Spectral range | 350 - 1050 nm (17 channels) with FWHW > 15nm |
| Altitude range | 0.1 - 7.5 km |
| Vertical resolution | in maximum: 1 km |
| Temporal resolution | 1 profile per flight |
| Operation | Depends on flight plan under clear sky conditions |
| Precision | ??a(?) < 0.008 |
| Data availability (during campaign) | next day |
| Final availability (after campaign) | three months |
Specific remarks
- Brightness measurements from Polar 4 are also possible to derive phase function and refractive index.
- The airborne measurements start at 100 m.a.s.l., combined analyses with measurements at NYA and LYR is needed.
References: Nagel, D., A. Herber, L.W. Thomason, U. Leiterer, 1998.Vertical distribution of the spectral aerosol optical depth in the Arctic from 1993 to 1996, J. Geophys. Res., 103, 1857 - 1870.
Herber, A., Thomason, L.W., Gernandt, H., Leiterer, U., Nagel, D., Schulz, K. H., Kaptur, J., Albrecht, T., Notholt, J., 2002. Continuous day and night aerosol optical depth observations in the Arctic between 1991 and 1999. J. Geophys. Res., 107 D10, 10.1029/2001JD000536 - AAC 6-1 to 6-14.