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Alexander Myagkov, Patric Seifert, Ulla Wandinger, Matthias Bauer-Pfundstein, and Sergey Y. Matrosov

Abstract

This paper presents an experimental analysis of the antenna system effects on polarimetric measurements conducted with cloud radars operating in the linear depolarization ratio (LDR) mode. Amplitude and phase of the copolar and cross-polar antenna patterns are presented and utilized. The patterns of two antennas of different quality were measured at the Hungriger Wolf airport near Hohenlockstedt, Germany, during the period from 28 January to 1 February 2014. For the measurements a test transmitter mounted on a tower and the scanning 35-GHz (Ka band) cloud radar MIRA-35, manufactured by METEK GmbH and operated in the receiving mode, were used. The integrated cross-polarization ratios (ICPR) are calculated for both antennas and compared with those measured in light rain. Correction algorithms for observed LDR and the co-cross-channel correlation coefficient ρ are presented. These algorithms are aimed at removing/mitigating polarization cross-coupling effects that depend on the quality of radar hardware. Thus, corrected LDR and ρ are primarily influenced by scatterer properties. The corrections are based on the decomposition of the coherency matrix of the received signals into fully polarized and nonpolarized components. The correction brings LDR values and the co-cross-channel correlation coefficients from two radars with different antenna systems to a close agreement, thus effectively removing hardware-dependent biases. Uncertainties of the correction are estimated as 3 dB for LDR in the range from −30 to −10 dB. In clouds, the correction of the co-cross-channel correlation coefficient ρ results in near-zero values for both vertically pointed radars.

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Christian Herold, Dietrich Althausen, Detlef Müller, Matthias Tesche, Patric Seifert, Ronny Engelmann, Cyrille Flamant, Rohini Bhawar, and Paolo Di Girolamo

Abstract

Water vapor measurements with the multiwavelength Raman lidar Backscatter Extinction Lidar-Ratio Temperature Humidity Profiling Apparatus (BERTHA) were performed during the Convective and Orographically-induced Precipitation Study (COPS) in the Black Forest, Germany, from June to August 2007. For quality assurance, profiles of the water vapor mixing ratio measured with BERTHA are compared to simultaneous measurements of a radiosonde and an airborne differential absorption lidar (DIAL) on 31 July 2007. The differences from the radiosonde observations are found to be on average 1.5% and 2.5% in the residual layer and in the free troposphere, respectively. During the two overflights at 1937 and 2018 UTC, the differences from the DIAL results are −2.2% and −3.7% in the residual layer and 2.1% and −2.6% in the free troposphere. After this performance check, short-range forecasts from the German Meteorological Service’s (Deutscher Wetterdienst, DWD) version of the Consortium for Small-Scale Modeling (COSMO-DE) model are compared to the BERTHA measurements for two case studies. Generally, it is found that water vapor mixing ratios from short-range forecasts are on average 7.9% drier than the values measured in the residual layer. In the free troposphere, modeled values are 9.7% drier than the measurements.

Full access
Andrea Lammert, Akio Hansen, Felix Ament, Susanne Crewell, Galina Dick, Verena Grützun, Henk Klein-Baltink, Volker Lehmann, Andreas Macke, Bernhard Pospichal, Wiebke Schubotz, Patric Seifert, Erasmia Stamnas, and Bjorn Stevens

Abstract

Central Europe has a vital and extensive meteorological research community comprising national weather services, universities, and research organizations and institutes. Nearly all of them are involved in the open scientific questions regarding clouds and precipitation processes. The research activities include observations (from in situ ground-based remote sensing radio soundings to satellite-based observations), model development on all scales (from direct numerical simulations to global climate models), and other activities. With Germany as an example our first objective is to show the large amount and the diversity of observations regarding clouds and precipitation. The goal is to give an overview of existing measurements and datasets to show the benefit of combining the different information from a variety of observations. Up to now the access to and the usage of these datasets from different sources was not straightforward, due to the issue of missing data and archiving standards for observational data. This then motivates our second objective, which is to introduce our solution for this issue—the novel Standardized Atmospheric Measurement Data archive (SAMD). SAMD is one of the outcomes of the German research initiative High Definition Clouds and Precipitation for Advancing Climate Prediction [HD(CP)2]. The goal of SAMD is an easy-to-use approach for both data producers and archive users. Therefore the archive provides observational data in the common Climate Forecast (CF) Conventions format and makes it available to the broader public. SAMD offers highly standardized quality-controlled data and metadata for a wide range of instruments, with open access, which makes this novel archive important for the research community.

Open access
David H. Bromwich, Kirstin Werner, Barbara Casati, Jordan G. Powers, Irina V. Gorodetskaya, François Massonnet, Vito Vitale, Victoria J. Heinrich, Daniela Liggett, Stefanie Arndt, Boris Barja, Eric Bazile, Scott Carpentier, Jorge F. Carrasco, Taejin Choi, Yonghan Choi, Steven R. Colwell, Raul R. Cordero, Massimo Gervasi, Thomas Haiden, Naohiko Hirasawa, Jun Inoue, Thomas Jung, Heike Kalesse, Seong-Joong Kim, Matthew A. Lazzara, Kevin W. Manning, Kimberley Norris, Sang-Jong Park, Phillip Reid, Ignatius Rigor, Penny M. Rowe, Holger Schmithüsen, Patric Seifert, Qizhen Sun, Taneil Uttal, Mario Zannoni, and Xun Zou

Abstract

The Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) had a special observing period (SOP) that ran from 16 November 2018 to 15 February 2019, a period chosen to span the austral warm season months of greatest operational activity in the Antarctic. Some 2,200 additional radiosondes were launched during the 3-month SOP, roughly doubling the routine program, and the network of drifting buoys in the Southern Ocean was enhanced. An evaluation of global model forecasts during the SOP and using its data has confirmed that extratropical Southern Hemisphere forecast skill lags behind that in the Northern Hemisphere with the contrast being greatest between the southern and northern polar regions. Reflecting the application of the SOP data, early results from observing system experiments show that the additional radiosondes yield the greatest forecast improvement for deep cyclones near the Antarctic coast. The SOP data have been applied to provide insights on an atmospheric river event during the YOPP-SH SOP that presented a challenging forecast and that impacted southern South America and the Antarctic Peninsula. YOPP-SH data have also been applied in determinations that seasonal predictions by coupled atmosphere–ocean–sea ice models struggle to capture the spatial and temporal characteristics of the Antarctic sea ice minimum. Education, outreach, and communication activities have supported the YOPP-SH SOP efforts. Based on the success of this Antarctic summer YOPP-SH SOP, a winter YOPP-SH SOP is being organized to support explorations of Antarctic atmospheric predictability in the austral cold season when the southern sea ice cover is rapidly expanding.

Free access
Manfred Wendisch, Andreas Macke, André Ehrlich, Christof Lüpkes, Mario Mech, Dmitry Chechin, Klaus Dethloff, Carola Barrientos Velasco, Heiko Bozem, Marlen Brückner, Hans-Christian Clemen, Susanne Crewell, Tobias Donth, Regis Dupuy, Kerstin Ebell, Ulrike Egerer, Ronny Engelmann, Christa Engler, Oliver Eppers, Martin Gehrmann, Xianda Gong, Matthias Gottschalk, Christophe Gourbeyre, Hannes Griesche, Jörg Hartmann, Markus Hartmann, Bernd Heinold, Andreas Herber, Hartmut Herrmann, Georg Heygster, Peter Hoor, Soheila Jafariserajehlou, Evelyn Jäkel, Emma Järvinen, Olivier Jourdan, Udo Kästner, Simonas Kecorius, Erlend M. Knudsen, Franziska Köllner, Jan Kretzschmar, Luca Lelli, Delphine Leroy, Marion Maturilli, Linlu Mei, Stephan Mertes, Guillaume Mioche, Roland Neuber, Marcel Nicolaus, Tatiana Nomokonova, Justus Notholt, Mathias Palm, Manuela van Pinxteren, Johannes Quaas, Philipp Richter, Elena Ruiz-Donoso, Michael Schäfer, Katja Schmieder, Martin Schnaiter, Johannes Schneider, Alfons Schwarzenböck, Patric Seifert, Matthew D. Shupe, Holger Siebert, Gunnar Spreen, Johannes Stapf, Frank Stratmann, Teresa Vogl, André Welti, Heike Wex, Alfred Wiedensohler, Marco Zanatta, and Sebastian Zeppenfeld

Abstract

Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC) project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.

Open access