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Solar Radiation Measurements on HALO

Subject Area Atmospheric Science
Term from 2010 to 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 178612691
 
Final Report Year 2015

Final Report Abstract

The instruments HALO-SR and SMART – originally developed for the HALO missions OMO and ML-CIRRUS – were successfully deployed in several HALO and Zeppelin campaigns during the period 2010-2014. In 2010 HALO-SR participated in TECHNO, the first scientific HALO mission. The obtained data were used to investigate the influence of surface albedo and its variability on the retrieval of cloud optical and microphysical properties from spectral radiance measurements using a 1D radiative transfer model. In 2012 and 2013 the actinic radiation components of HALO-SR were employed in three Zeppelin campaigns in southern and northern Europe, producing valuable insight into the photochemistry and the height dependence of photolysis frequencies within the planetary boundary layer. Moreover, photolysis frequency predictions of a regional chemistry-transport model were evaluated. In late 2013 and early 2014 HALO-SR was deployed during the NARVAL mission over the southern and northern North Atlantic. Data analysis so far concentrated on the performance of the retrieval of cloud optical and microphysical properties from measured nadir spectral radiances. The retrieved cloud properties were used as an input to a radiative transfer model predicting spectral actinic flux densities for comparison with the simultaneous measurements. The agreement of the most critical upward spectral actinic flux density was reasonable, but not perfect, and further efforts to improve of the retrieval algorithm are in progress. Moreover, radiance data were used to improve the calibration of MiniDOAS measurements on HALO and to compare retrieved liquid water paths with those from HAMP microwave measurements. Again the campaign data were also utilized to evaluate global chemistry-transport model predictions of photolysis frequencies. Finally, most recently the SMART instrument was operated in the two 2014 missions ML-CIRRUS and ACRIDICON over Europe and the Atlantic, and Brazil, respectively. The essential horizontal stabilization worked successfully allowing for accurate in-flight net irradiance measurements. Moreover, simultaneous spectral radiance measurements were already used for direct comparison with satellite radiance data and retrieved cloud optical thicknesses with promising first results. Most data gained during the various campaigns are still being analyzed and will be the basis for further publications. An OMO test campaign was conducted in January 2015. The OMO mission will take place in summer 2015 and there are further requests to implement HALO-SR in the intended missions T-NAWDEX and NARVAL 2.0 in 2016, EMERGE in 2017/2018 and CAFE 2018. SMART worked successfully during ML-CIRRUS and ACRIDICON. It is planned to continue this work by operating SMART within WISE in 2017 in a combination with the GLORIA IR limbscanner to investigate sub-visible clouds in the tropopause region.

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