Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: Martin Stengel x
  • Refine by Access: All Content x
Clear All Modify Search
Daniel Philipp
,
Martin Stengel
, and
Bodo Ahrens

Abstract

Satellite-based cloud, radiation flux, and sea ice records covering 34 years are used 1) to investigate autumn cloud cover trends over the Arctic, 2) to assess its relation with declining sea ice using Granger causality (GC) analysis, and 3) to discuss the contribution of the cloud–sea ice (CSI) feedback to Arctic amplification. This paper provides strong evidence for a positive CSI feedback with the capability to contribute to autumnal Arctic amplification. Positive low-level cloud fractional cover (CFClow) trends over the Arctic ice pack are found in October and November (ON) with magnitudes of up to about +9.6% per decade locally. Statistically significant anticorrelations between sea ice concentration (SIC) and CFClow are observed in ON over melting zones, suggesting an association. The GC analysis indicated a causal two-way interaction between SIC and CFClow. Interpreting the resulting F statistic and its spatial distribution as a relation strength proxy, the influence of SIC on CFClow is likely stronger than the reverse. ERA-Interim reanalysis data suggest that ON CFClow is impacted by sea ice melt through surface–atmosphere coupling via turbulent heat and moisture fluxes. Due to weak solar insolation in ON, net cloud radiative forcing (CRF) exerts a warming effect on the Arctic surface. Increasing CFClow induces a large-scale surface warming trend reaching magnitudes of up to about +8.3 W m−2 per decade locally. Sensitivities of total CRF to CFClow ranges between +0.22 and +0.66 W m−2 per percent CFClow. Increasing surface warming can cause a melt season lengthening and hinders formation of perennial ice.

Free access
Axel Lauer
,
Lisa Bock
,
Birgit Hassler
,
Marc Schröder
, and
Martin Stengel

Abstract

Simulating clouds with global climate models is challenging as relevant physics involves many non-linear processes covering a wide range of spatial and temporal scales. As key components of the hydrological cycle and the climate system, an evaluation of clouds from models used for climate projections is an important prerequisite for assessing the confidence in the results from these models. Here, we compare output from models contributing to Phase 6 of the Coupled Model Intercomparison Project (CMIP6) with satellite data and with results from their predecessors (CMIP5). We use multi-product reference datasets to estimate the observational uncertainties associated with different sensors and with internal variability on a per-pixel basis. Selected cloud properties are also analyzed by region and by dynamical regime and thermodynamic conditions.

Our results show that for parameters such as total cloud cover, cloud water path and cloud radiative effect, the CMIP6 multi-model mean performs slightly better than the CMIP5 ensemble mean in terms of mean bias, pattern correlation and relative root-mean square deviation. The inter-model spread in CMIP6, however, is not reduced compared to CMIP5. Compared with CALIPSO-ICECLOUD data, the CMIP5/6 models overestimate cloud ice particularly in the lower and middle troposphere partly due to too high ice fractions for given temperatures. This bias is reduced in the CMIP6 multi-model mean. While many known biases such as an underestimation in cloud cover in stratocumulus regions remain in CMIP6, we find that the CMIP5 problem of too few but too reflective clouds over the Southern Ocean is significantly improved.

Restricted access
Marlon Maranan
,
Andreas H. Fink
,
Peter Knippertz
,
Leonard K. Amekudzi
,
Winifred A. Atiah
, and
Martin Stengel

Abstract

Using a two-year dataset (2016–17) from 17 one-minute rain gauges located in the moist forest region of Ghana, the performance of Integrated Multisatellite Retrievals for GPM, version 6b (IMERG), is evaluated based on a subdaily time scale, down to the level of the underlying passive microwave (PMW) and infrared (IR) sources. Additionally, the spaceborne cloud product Cloud Property Dataset Using SEVIRI, edition 2 (CLAAS-2), available every 15 min, is used to link IMERG rainfall to cloud-top properties. Several important issues are identified: 1) IMERG’s proneness to low-intensity false alarms, accounting for more than a fifth of total rainfall; 2) IMERG’s overestimation of the rainfall amount from frequently occurring weak convective events, while that of relatively rare but strong mesoscale convective systems is underestimated, resulting in an error compensation; and 3) a decrease of skill during the little dry season in July and August, known to feature enhanced low-level cloudiness and warm rain. These findings are related to 1) a general oversensitivity for clouds with low ice and liquid water path and a particular oversensitivity for low cloud optical thickness, a problem which is slightly reduced for direct PMW overpasses; 2) a pronounced negative bias for high rain intensities, strongest when IR data are included; and 3) a large fraction of missed events linked with rainfall out of warm clouds, which are inherently misinterpreted by IMERG and its sources. This paper emphasizes the potential of validating spaceborne rainfall products with high-resolution rain gauges on a subdaily time scale, particularly for the understudied West African region.

Open access
Rob Roebeling
,
Bryan Baum
,
Ralf Bennartz
,
Ulrich Hamann
,
Andrew Heidinger
,
Jan Fokke Meirink
,
Martin Stengel
,
Anke Thoss
,
Andi Walther
, and
Phil Watts
Full access
Robert J. H. Dunn
,
F. Aldred
,
Nadine Gobron
,
John B. Miller
,
Kate M. Willett
,
M. Ades
,
Robert Adler
,
Richard, P. Allan
,
Rob Allan
,
J. Anderson
,
Anthony Argüez
,
C. Arosio
,
John A. Augustine
,
C. Azorin-Molina
,
J. Barichivich
,
H. E. Beck
,
Andreas Becker
,
Nicolas Bellouin
,
Angela Benedetti
,
David I. Berry
,
Stephen Blenkinsop
,
Olivier Bock
,
X. Bodin
,
Michael G. Bosilovich
,
Olivier Boucher
,
S. A. Buehler
,
B. Calmettes
,
Laura Carrea
,
Laura Castia
,
Hanne H. Christiansen
,
John R. Christy
,
E.-S. Chung
,
Melanie Coldewey-Egbers
,
Owen R. Cooper
,
Richard C. Cornes
,
Curt Covey
,
J.-F. Cretaux
,
M. Crotwell
,
Sean M. Davis
,
Richard A. M. de Jeu
,
Doug Degenstein
,
R. Delaloye
,
Larry Di Girolamo
,
Markus G. Donat
,
Wouter A. Dorigo
,
Imke Durre
,
Geoff S. Dutton
,
Gregory Duveiller
,
James W. Elkins
,
Vitali E. Fioletov
,
Johannes Flemming
,
Michael J. Foster
,
Stacey M. Frith
,
Lucien Froidevaux
,
J. Garforth
,
Matthew Gentry
,
S. K. Gupta
,
S. Hahn
,
Leopold Haimberger
,
Brad D. Hall
,
Ian Harris
,
D. L. Hemming
,
M. Hirschi
,
Shu-pen (Ben) Ho
,
F. Hrbacek
,
Daan Hubert
,
Dale F. Hurst
,
Antje Inness
,
K. Isaksen
,
Viju O. John
,
Philip D. Jones
,
Robert Junod
,
J. W. Kaiser
,
V. Kaufmann
,
A. Kellerer-Pirklbauer
,
Elizabeth C. Kent
,
R. Kidd
,
Hyungjun Kim
,
Z. Kipling
,
A. Koppa
,
B. M. Kraemer
,
D. P. Kratz
,
Xin Lan
,
Kathleen O. Lantz
,
D. Lavers
,
Norman G. Loeb
,
Diego Loyola
,
R. Madelon
,
Michael Mayer
,
M. F. McCabe
,
Tim R. McVicar
,
Carl A. Mears
,
Christopher J. Merchant
,
Diego G. Miralles
,
L. Moesinger
,
Stephen A. Montzka
,
Colin Morice
,
L. Mösinger
,
Jens Mühle
,
Julien P. Nicolas
,
Jeannette Noetzli
,
Ben Noll
,
J. O’Keefe
,
Tim J. Osborn
,
T. Park
,
A. J. Pasik
,
C. Pellet
,
Maury S. Pelto
,
S. E. Perkins-Kirkpatrick
,
G. Petron
,
Coda Phillips
,
S. Po-Chedley
,
L. Polvani
,
W. Preimesberger
,
D. G. Rains
,
W. J. Randel
,
Nick A. Rayner
,
Samuel Rémy
,
L. Ricciardulli
,
A. D. Richardson
,
David A. Robinson
,
Matthew Rodell
,
N. J. Rodríguez-Fernández
,
K.H. Rosenlof
,
C. Roth
,
A. Rozanov
,
T. Rutishäuser
,
Ahira Sánchez-Lugo
,
P. Sawaengphokhai
,
T. Scanlon
,
Verena Schenzinger
,
R. W. Schlegel
,
S. Sharma
,
Lei Shi
,
Adrian J. Simmons
,
Carolina Siso
,
Sharon L. Smith
,
B. J. Soden
,
Viktoria Sofieva
,
T. H. Sparks
,
Paul W. Stackhouse Jr.
,
Wolfgang Steinbrecht
,
Martin Stengel
,
Dimitri A. Streletskiy
,
Sunny Sun-Mack
,
P. Tans
,
S. J. Thackeray
,
E. Thibert
,
D. Tokuda
,
Kleareti Tourpali
,
Mari R. Tye
,
Ronald van der A
,
Robin van der Schalie
,
Gerard van der Schrier
,
M. van der Vliet
,
Guido R. van der Werf
,
A. Vance
,
Jean-Paul Vernier
,
Isaac J. Vimont
,
Holger Vömel
,
Russell S. Vose
,
Ray Wang
,
Markus Weber
,
David Wiese
,
Anne C. Wilber
,
Jeanette D. Wild
,
Takmeng Wong
,
R. Iestyn Woolway
,
Xinjia Zhou
,
Xungang Yin
,
Guangyu Zhao
,
Lin Zhao
,
Jerry R. Ziemke
,
Markus Ziese
, and
R. M. Zotta
Free access