Advanced Microwave Radiometer for Rain Identification (ADMIRARI II)
Final Report Abstract
Within the course of this project, significant progress has been made in characterizing ice clouds and snowfall. They are still poorly represented in atmospheric weather and climate prediction models and improvements in observation methods are highly desired. The improvements in observation within ADMIRARI II can be stated in 6 major points: • A new method to use the widely distributed MRR (Micro Rain Radar) also for snowfall measurements has been successfully developed. The original method supplied by the manufacturer allows only dealing with liquid precipitation (rain) and thus the instrument operated erroneously during snowfall. Low snowfall rates can now be measured due to the improvement in MRR sensitivity of 5dB. This is of high significance, especially for operation in Polar regions. • Based on the improved MRR analysis - the "blind-zone" of Cloudsat was characterized. However, Cloudsat has limitations in measuring the snow in the lowest kilometer above the surface. It was found that the blind-zone leads to an overestimation of the number of snowfall events of around 5% and an underestimation of the total precipitation amount by 10%. These results must be considered for global snowfall climatologies and future satellite missions. • Based on the spectral analysis method and intense international collaboration, a Doppler radar simulator was developed for frozen clouds and precipitation. For the first time, atmospheric Doppler spectra (including the moments of the Doppler spectrum) can be simulated for different types of ice particles. The model is very important for understanding the physics of ice and mixed-phase clouds as well as for future evaluation of ice cloud parameters in weather prediction model with sophisticated ice cloud microphysics. • The Doppler radar simulator was used to improve the representation of cloud ice. Because atmospheric ice particles appear in innumerable different sizes and shapes, these are ideally parameterized to a handful of characteristic numbers. The Doppler radar simulator was applied to ice clouds collocated with aircraft measurements. The differences were evaluated as a function of the different parameterizations available in literature and an optimized set of corresponding mathematical description methods was derived. From this, future methods will be developed to directly retrieve ice cloud parameters from Doppler radar spectra. • A unique synergy of ADMIRARI with active C- and X-band radars made possible the evaluation of retrieved micro-physical properties of solid and mixed-phase precipitation (melting-layer). The presence of supercooled LWC helps to understand different radar signatures, which can help estimate snow accumulation by weather radars. Additionally, instrument synergy offers a unique tool to estimate attenuation properties of melting-layer. • Improvements on the retrievals of rain and cloud LWP partitioning have been achieved thanks to the inclusion of a ceilometer to correct for biases during non-rainy periods and to constrain a-priori information. Additionally ADMIRARI measurements improved the understanding of 3D radiative transfer effects in tropical convective as well as warm rain cases by successfully simulating events with those radiative characteristics.
Publications
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2011: Understanding three-dimensional effects in polarized observations with the ground-based ADMIRARI radiometer during CHUVA campaign. JGR Atmospheres, Vol. 116, D09204
Battaglia, A., P. Saavedra, C.A. Morales, and C. Simmer
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2012: Improved Micro Rain Radar snow measurements using Doppler spectra post-processing. Atmospheric Measurement Techniques, 5, 2661–2673
Maahn, M., und P. Kollias
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2012: Partitioning of cloud water and rainwater by ground-based observations with the Advanced Microwave Radiometer for Rain Identification (ADMIRARI) in synergy with a micro rain radar. JGR Atmospheres, Vol. 117, D05203
Saavedra, P., A. Battaglia, C. Simmer
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2014: Cloud and precipitation properties from ground-based remote sensing instruments in East Antarctica The Cryosphere, 9, 285-304, 2015
Gorodetskaya, I.V., S. Kneifel, M. Maahn, K. Van Tricht, J. H. Schween, S. Crewell, and N. P. M. Van Lipzig
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2014: How does the spaceborne radar blind zone affect derived surface snowfall statistics in polar regions? J. Geophys. Res.-Atmospheres, 119, 13604–13620
Maahn M., C. Burgard, S. Crewell, I. V. Gorodetskaya, S. Kneifel, S. Lhermitte, K. Van Tricht, N. P. M. van Lipzig
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2015: Developing and Evaluating Ice Cloud Parameterizations for Forward Modeling of Radar Moments Using In Situ Aircraft Observations Journal of Atmospheric and Oceanic Technology (Early Online Release)
Maahn, M., U. Löhnert, P. Kollias, R. C. Jackson and G. M. McFarquhar
