Matthias Zahn

News archive


(Dec 2017) Our article "Trends of cyclone characteristics in the Arctic and their patterns from different re-analysis data" was accepted in the Journal of Geophysical Research - Atmospheres (Impact Factor 3.454 in the 2016 ISI Journal Citation Reports). I am the 1st author of this manuscript, and I had contributions from M. Akperov, A, Rinke, F. Feser and I. Mokhov.

(Mar 2017) Our article "Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe", led Ha Ho-Hagemann with contributions from M. Gröger, B. Rockel, M. Zahn, B. Geyer and M. Meier published in Climate Dynamics (Impact Factor 4.708) went online [online version]
(Jan 2017) We got a new article accepted in Climate Dynamics (Impact Factor 4.708), "Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe", led by Ha Ho-Hagemann contributions from M. Gröger, B. Rockel, M. Zahn, B. Geyer and M. Meier


(4 July 2016) We have a new article out in Nature Geoscience , "North Atlantic summer storm tracks over Europe dominated by internal variability over the past millennium", led by Mary H. Gagen from Swansea University, UK, with contributions from Eduardo Zorita, Danny McCarroll, Matthias Zahn, Giles H.F. Young and Iain Robertson [online version], [Swansea University press release], [ BBC NEWS referring to the article]

(June 2016) Our manuscript "Re-examining the roles of surface heat flux and latent heat release in a 'hurricane-like' polar low over the Barents Sea", the result of a cooperation with Erik Kolstad (Uni Research Climate, Bergen, Norway & Bjerknes Centre for Climate, Bergen, Norway) and Tom Bracegirdle (British Antarctic Survey, Camebridge, U.K.), has been accepted for publication in the Journal of Geophysical Research - Atmospheres (Impact Factor 3.426 in the 2014 ISI Journal Citation Reports) [online version]

(22/04/16) Our manuscript "Interannual Variability in the Summertime Hydrological Cycle over European Regions", the result of a cooperation with Igor Zveryaev (P.P. Shirshov Institute of Oceanology, Moscow, Russia) and Richard Allan (Universiy of Reading, U.K.), has been accepted for publication in the Journal of Geophysical Research - Atmospheres (Impact Factor 3.426 in the 2014 ISI Journal Citation Reports) [pdf] (Nov 2015) As my employer stopped hosting personal web-sites, I relaunched this collection of my scientific work here on www.mzahn.net

(Oct 2015) Our paper "Climatology of polar lows over the Sea of Japan using the JRA-55 reanalysis" has been accepted in the Journal of Climate

(July 15) I have recently added Discriminant Function Analysis to my cyclone tracking code and have submitted the manuscript "Applying Discriminant Function Analysis to Improve Tropical Cyclone Tracking" describing the method to Tellus A.

The abstract reads:
I employ discriminant functions analysis, a method of multivariate statistics, to optimise the detection of tropical cyclones in a globally downscaled6 long-term data set. The tracking results from linear and quadratic discriminant functions are evaluated against observations and their advantages discussed. Both methods improve the case matching in 2004 training and in 1980 test data and reduce the false identifications compared to simple standard approaches. The method could potentially be applied to any spatial data and any type of storm for which suffcient comparison data are available.

I am looking forward to visting Erik Kolstad from Uni Research and Bjerknes Centre for Climate Research in Bergen, Norway, 9 - 12 March.

(March 14) Our REKLIM topic 'Stürme in verschiedenen Regionen der Erde in einer hochaufglösten, globalen Klimasimulation der letzten 65 Jahre' has been selected Research highlight of the month of the Helmholtz Climate Initiative REKLIM. A pdf of the Newsletter including a brief research profile of myself can be found here.

(06/01/14) The special section on Oceanic Sources of Continental Precipitation at Water Resources Research has been published and contains our paper "Quantifying present and projected future atmospheric moisture transports onto land" (written with Richard Allan) [online version]
In this work we calculate atmospheric moisture transports across the global shorelines (i.e. from ocean to land) in a present and in a projected future climate applying high space and time resolution data from a Global Climate Model. We find land- as well as seaward moisture transports intensify with warming. A more pronounced intensification of landward transports results in increased moisture budgets for the continents.
In addition we demonstrate how limitations of 4 times daily data may result in systematic biases of the moisture transports. 4 times daily data may not capture minimum and maximum transports of the diurnal cycle well enough.

(24/10/13) Today I have accepted the invitation to serve as Review Editor in Frontiers in Atmospheric Science. I am looking forward to reviewing under the new two-staged review system promoted by Frontiers, which consists of an independent first review phase and a second interactive review phase discussing manuscripts with the authors in an Interactive Review Forum.

(09/10/13) Our manuscript "Quantifying present and projected future atmospheric moisture transports onto land" written with Richard Allan has been accepted for publication in Water Resources Research (Impact Factor 3.149 in the 2012 ISI Journal Citation Reports ) [online version not yet available]
We calculate atmospheric moisture transports across the global shorelines (i.e. from ocean to land) in a present and in a projected future climate applying high space and time resolution data from a Global Climate Model. We find land- as well as seaward moisture transports intensify with warming. A more pronounced intensification of landward transports results in increased moisture budgets for the continents.
In addition we demonstrate how limitations of 4 times daily data availability can result in systematic biases of the moisture transports because minima and maxima of the diurnal cycle may not be captured well enough.

(Feb 13) On 1st of February I started my new position as a scientist back at Helmholtz Centre Geesthacht in Germany (formerly known as GKSS). The main focus of my work will be tracking of storms over all oceans of the globe, but I also want continue my work on the hydrological cycle and its projected changes in a warming world.

(15/01/13) Our paper "Climate Warming related strengthening of the tropical hydrological cycle" written jointly with Richard Allan has been published in the Journal of Climate (Impact Factor 4.097 in the 2011 Journal Citation Reports) [online version]
Applying high space and time resolution data from a Global Climate Model we find water transports in the tropics increase towards the end of a projected 21st century. This increase is caused by higher atmospheric humidity values in response to warming, while changing wind patterns have a small weakening effect.

(Jan 13) The final version of our article "Physically consistent responses of the global atmospheric hydrological cycle in models and observations" by Allan, Liu, Zahn, Lavers, Koukouvagias and Bodas-Salcedo has been published online in Surveys in Geophysics
In this article we summarise and review our recent work on changes of the hydrological cycle. [online version].

(18/12/12) Our article "On the role of the ocean in projected atmospheric stability changes in the Atlantic polar low region" by Woollings, Harvey, Zahn and Shaffrey has been published in Geophysical Research Letters (Impact Factor 3.792 in the 2011 Journal Citation Reports)
Applying a set of IPCC climate models we show a weakening ocean circulation in response to projected future warming is steering the increase in vertical atmospheric stability over the North Atlantic. This increase was found to be the reason for the projected decline in polar low frequency in my previous Zahn and von Storch (2010) Nature study.
[online version].

(07/11/12) Our article "On the role of the ocean in projected atmospheric stability changes in the Atlantic polar low region" by Woollings, Harvey, Zahn and Shaffrey has been accepted for publication in Geophysical Research Letters (Impact Factor 3.792 in the 2011 Journal Citation Reports)
Applying a set of IPCC climate models we show a weakening ocean circulation in response to projected future warming is steering the increase in vertical atmospheric stability over the North Atlantic. This increase was found to be the reason for the projected decline in polar low frequency in my previous Zahn and von Storch (2010) Nature study.
[early online version].

(05/11/12) Our article "Physically consistent responses of the global atmospheric hydrological cycle in models and observations" by Allan, Liu, Zahn, Lavers, Koukouvagias and Bodas-Salcedo has been accepted for publication in Surveys in Geophysics
In this article we summarise and review our recent work on changes of the hydrological cycle.
(Sep/12) Our (Zahn and von Storch) article "Investigation of past and future Polar Low frequency in the North Atlantic" summarising our polar low work and showing in more detail the evolution of vertical stability over the North Atlantic has been published in: Sharma, A. S., A. Bunde, V. P. Dimri, and D. N. Baker (Eds.) (2012), Extreme Events and Natural Hazards: The Complexity Perspective, Geophys. Monogr. Ser., vol. 196, 371 pp., AGU, Washington, D. C., doi:10.1029/GM196 . [link].

(09/07/12) My paper "Climate Warming related strengthening of the tropical hydrological cycle" written jointly with Richard Allan has been accepted for publication in the Journal of Climate (Impact Factor 4.097 in the 2011 Journal Citation Reports) [Abstract]
Applying high space and time resolution data from a Global Climate Model we find water transports in the tropics increase towards the end of a projected 21st century. This increase is caused by higher atmospheric humidity values in response to warming, while changing wind patterns have a small weakening effect.

(30/5/12) For the recent EPLWG workshop in Oslo (21-22 May 2012) I wrote an extended abstract which summarises my work on polar lows on just 3 pages. [link].

(08/1/12) Our work (Xia et al.) on "A comparison of two identification and tracking methods for polar lows" has been published at Tellus A [see].
Two storm tracking methods differing in their ways of mathematical filtering, detection of minima in the filtered fields and subsequent tracking were applied to two years of RCM data. Both methods were adjusted to track the same subsynoptic-scale type of storms, polar lows. We found a major influence of the mathematical filtering part, but a minor effect of detection and tracking.

(24/9/11) Our (Zahn and Allan) work on "Changes in water vapor transports of the ascending branch of the tropical circulation" has been published in the J. Geophys. Res. (Impact Factor 3.303 in the 2010 Journal Citation Reports) [see].
Over the past two decades we found a significant intensification of tropical moisture transports of both, the lower level inflow and the mid level outflow. The intensification is much less pronounced in the resulting tropical moisture budget (inflow - outflow or precipitation - evaporation), as strengthening of the lower level inflow and mid level outflow neutralize each other, at least to some extent. We also highlight the importance of estimating moisture transports from 3-d high resolution instantaneous data, as averaging does not represent the temporal coincidence of high/low values for humidity and wind vectors.

(9/8/11) Our paper on "The changing atmospheric water cycle in polar regions in a warmer climate" (Bengtsson et al, 2011, one co-author M.Zahn) has been published in Tellus A. [online version].

(27/6/11) The review article "Investigation of past and future Polar Low frequency in the North Atlantic" by Zahn and von Storch, summarising my PhD and subsequent work has been accepted for publication in the special issue on extreme events of the AGU Geophysical Monograph Series. [manuscript].

(03/5/11) The early version of the review article Feser et al, (2011, one co-author M.Zahn) published in BAMS on the added value in Regional Climate Models went online. [see].