ORCID Profile
0000-0003-4111-1228
Current Organisation
Pusan National University
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Publisher: Wiley
Date: 06-10-2014
DOI: 10.1002/WCC.318
Abstract: Stochastic methods are a crucial area in contemporary climate research and are increasingly being used in comprehensive weather and climate prediction models as well as reduced order climate models. Stochastic methods are used as subgrid‐scale parameterizations (SSPs) as well as for model error representation, uncertainty quantification, data assimilation, and ensemble prediction. The need to use stochastic approaches in weather and climate models arises because we still cannot resolve all necessary processes and scales in comprehensive numerical weather and climate prediction models. In many practical applications one is mainly interested in the largest and potentially predictable scales and not necessarily in the small and fast scales. For instance, reduced order models can simulate and predict large‐scale modes. Statistical mechanics and dynamical systems theory suggest that in reduced order models the impact of unresolved degrees of freedom can be represented by suitable combinations of deterministic and stochastic components and non‐Markovian (memory) terms. Stochastic approaches in numerical weather and climate prediction models also lead to the reduction of model biases. Hence, there is a clear need for systematic stochastic approaches in weather and climate modeling. In this review, we present evidence for stochastic effects in laboratory experiments. Then we provide an overview of stochastic climate theory from an applied mathematics perspective. We also survey the current use of stochastic methods in comprehensive weather and climate prediction models and show that stochastic parameterizations have the potential to remedy many of the current biases in these comprehensive models. WIREs Clim Change 2015, 6:63–78. doi: 10.1002/wcc.318 This article is categorized under: Climate Models and Modeling Model Components
Publisher: American Geophysical Union (AGU)
Date: 04-01-2018
DOI: 10.1002/2017JD027222
Publisher: American Meteorological Society
Date: 03-2013
Abstract: Changes in the metastability of the Southern Hemisphere 500-hPa circulation are examined using both cluster analysis techniques and split-flow blocking indices. The cluster methodology is a purely data-driven approach for parameterization whereby a multiscale approximation to nonstationary dynamical processes is achieved through optimal sequences of locally stationary fast vector autoregressive factor (VARX) processes and some slow (or persistent) hidden process switching between them. Comparison is made with blocking indices commonly used in weather forecasting and climate analysis to identify dynamically relevant metastable regimes in the 500-hPa circulation in both reanalysis and Atmospheric Model Intercomparison Project (AMIP) datasets. The analysis characterizes the metastable regime in both reanalysis and model datasets prior to 1978 as positive and negative phases of a hemispheric midlatitude blocking state with the southern annular mode (SAM) associated with a transition state. Post-1978, the SAM emerges as a true metastable state replacing the negative phase of the hemispheric blocking pattern. The hidden state frequency of occurrences exhibits strong trends. The blocking pattern dominates in the early 1980s, and then gradually decreases. There is a corresponding increase in the SAM frequency of occurrence. This trend is largely evident in the reanalysis summer and spring but was not evident in the AMIP dataset. Further comparison with the split-flow blocking indices reveals a superficial correspondence between the cluster hidden state frequency of occurrences and split-flow indices. Examination of composite states shows that the blocking indices capture splitting of the zonal flow whereas the cluster composites reflect coherent block formation. Differences in blocking climatologies from the respective methods are discussed.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-10775
Abstract: & & In an era where communicating your science goes hand in hand with doing your science, many scientists devote time to develop tools and learn new skills and strategies for Science Communication. The European Geosciences Union (EGU) has put in place one of those tools: the Divisions& #8217 Blog. Most of the current EGU Divisions has an active blog run mainly by one or more volunteer early-career scientists.& & br& Regularly, both editors, and regular and guest authors write about research in their field, talk about relevant topics discussed within the scientific community, and highlight interesting facts for scientists and the general public. The goal is to provide a platform for enhancing communication among geoscientists in ways that go beyond the means of peer-reviewed publication or scientific conferences. At the same time, we aim at engaging with the general public, by writing in a technically sound, but more accessible form. Each Division& #8217 s blog has its character, like the teams behind it, making the blogs a ersified and exciting digital environment.& & & & Here we show the main numbers, statistics, and feedback from each Division Blog, thus providing a measure of the efforts put in and the impact made so far by the broad Geoscience community. We discuss best practices, blog styles and topics which do work well or not, based on readership statistics. We also show the channels chosen for advertising the blogs, such as social media, and the impact of the choices made. Finally, we show that even though EGU has its base in Europe, we reach an audience beyond Europe thanks to active members based outside Europe and to topics addressing particular geographical areas.& & & & We conclude that, within the increasingly essential role played by Science Communication in every research field, the EGU Divisions& #8217 Blogs are successful at sharing research related to their fields with the broad geoscientific and non-scientific community. This success mainly relies on the time, effort, motivation, and creativity of editors and guest authors.& &
Publisher: American Geophysical Union (AGU)
Date: 27-05-2013
DOI: 10.1002/JGRD.50374
Publisher: Springer Science and Business Media LLC
Date: 15-08-2016
No related grants have been discovered for Christian Franzke.