Akos Horvath

Akos Horvath
University of Hamburg | UHH · Meteorologisches Institut (MI), Radiation and Remote Sensing Group

Ph.D.

About

88
Publications
12,350
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800
Citations
Introduction
Ákos Horváth currently works at the Meteorological Institute (MI), Radiation and Remote Sensing Group, University of Hamburg. Ákos does research in Meteorology and Remote Sensing.
Additional affiliations
February 2015 - April 2016
Science and Technology Facilities Council
Position
  • Remote Sensing Scientist
October 2011 - January 2015
Leibniz Institute for Tropospheric Research
Position
  • Researcher
May 2007 - September 2011
Max Planck Institute for Meteorology
Position
  • Researcher
Education
July 1999 - May 2004
The University of Arizona
Field of study
  • Atmospheric Science
January 1997 - May 1999
The University of Arizona
Field of study
  • Atmospheric Science
September 1990 - June 1996
Eötvös Loránd University
Field of study
  • Meteorology

Publications

Publications (88)
Article
Full-text available
Recent advances in geostationary imaging have enabled the derivation of high spatiotemporal-resolution cloud-motion winds for the study of mesoscale unsteady flows. Due to the general absence of ground truth, the quality assessment of satellite winds is challenging. In the current limited practice, straightforward plausibility checks on the smoothn...
Article
Full-text available
In June 2019, the Raikoke volcano, Kuril Islands, emitted 0.4–1.8×109 kg of very fine ash and 1–2×109 kg of SO2 up to 14 km into the atmosphere. The eruption was characterized by several eruption phases of different duration and height summing up to a total eruption length of about 5.5 h. Resolving such complex eruption dynamics is required for pre...
Article
Full-text available
In the Northern Hemisphere, south is the conventional azimuth direction of fixed-tilt monofacial solar panels, because this orientation may maximize the received light energy. How does the morning-afternoon cloudiness asymmetry affect the energy-maximizing azimuth direction of such solar panels? Prompted by this question, we calculated the total li...
Article
Full-text available
Stereo methods using GOES-17 and Himawari-8 applied to the Hunga Tonga-Hunga Ha'apai volcanic plume on 15 January 2022 show overshooting tops reaching 50–55 km altitude, a record in the satellite era. Plume height is important to understand dispersal and transport in the stratosphere and climate impacts. Stereo methods, using geostationary satellit...
Article
Full-text available
We estimated geometric plume heights for the daytime eruptions of La Soufrière in April 2021 using visible red band geostationary side views and geostationary–polar orbiter stereo views. Most of the plumes either spread near the tropopause at 16–17 km altitude or penetrated the stratosphere at 18–20 km altitude. Overshooting tops reached heights of...
Preprint
Full-text available
We estimated geometric plume heights for the daytime eruptions of La Soufrière in April 2021 using visible red band geostationary side views and geostationary-polar orbiter stereo views. Most of the plumes either spread near the tropopause at 16-17km altitude or penetrated the stratosphere at 18-20km altitude. Overshooting tops reached heights up t...
Data
This supporting information (SI) provides contrast-enhanced versions of the GOES-17 and Himawari-8 visible images in Figure 1 of the article (S1), an independent geometric estimate of the maximum plume height at 04:30Z obtained by applying the side view method to the corresponding GEO-KOMPSAT-2A image (S2), and additional shadow-based height estima...
Data
This supporting information (SI) provides contrast-enhanced versions of the GOES-17 and Himawari-8 visible images in Figure 1 of the article (S1), an independent geometric estimate of the maximum plume height at 04:30Z obtained by applying the side view method to the corresponding GEO-KOMPSAT-2A image (S2), and additional shadow-based height estima...
Preprint
Full-text available
Stereo methods using GOES-17 and Himawari-8 applied to the Hunga Tonga-Hunga Ha’apai volcanic plume on 15 January 2022 show overshooting tops reaching 50-55 km altitude, a record in the satellite era. Plume height is important to understand dispersal and transport in the stratosphere and climate impacts. Stereo methods, using geostationary satellit...
Data
Evolution of streaklines in the Guadalupe flow. In order to avoid intersections and reduce visual clutter, streaklines are truncated when their distance falls below a threshold.
Data
Texture advection of a MODIS image of a typical trade wind cumulus field by the Guadalupe flow. Essentially, these are densely-seeded timelines with grey values taken from the MODIS image.
Data
Texture advection of zebra-colored timelines by the Guadalupe flow. In addition to pattern formation, it also shows reduced wind speeds in the wake (wind shadow) and that the unperturbed ambient flow is faster west (left) of the wake than east (right) of the wake.
Data
Texture advection of Perlin noise by the Guadalupe flow (https://en.wikipedia.org/wiki/Perlin_noise). Note that structures emerge even when a noise texture is advected.
Data
Evolution of six particular timelines in the Guadalupe flow, the central (in-wake) part of which roll up into the characteristic mushroom pattern. The grey lines are the pathlines of selected points of the topmost (northernmost) timeline.
Data
Texture advection of a checkerboard pattern by the Guadalupe flow. The six colored squares demonstrate different types of deformation. The green squares, east and west of the wake, are advected by the ambient flow and, thus, undergo relatively little deformation. The blue and red squares roll up into anticyclonic and cyclonic vortices, respectively...
Data
Texture advection of a MODIS image of a typical marine stratocumulus field by the Guadalupe flow. Essentially, these are densely-seeded timelines with grey values taken from the MODIS image.
Article
Full-text available
A geometric technique is introduced to estimate the height of volcanic eruption columns using the generally discarded near-limb portion of geostationary imagery. Such oblique observations facilitate a height-by-angle estimation method by offering close-to-orthogonal side views of eruption columns protruding from the Earth ellipsoid. Coverage is res...
Article
Full-text available
In a companion paper (Horváth et al., 2021), we introduced a new technique to estimate volcanic eruption column height from extremely oblique near-limb geostationary views. The current paper demonstrates and validates the technique in a number of recent eruptions, ranging from ones with weak columnar plumes to subplinian events with massive umbrell...
Preprint
Full-text available
In June 2019, the Raikoke volcano, Kuril Islands, emitted 0.4–1.8 × 109 kg of very fine ash and 1–2 × 109 kg of SO2 up to 14 km into the atmosphere. The eruption was characterized by several phases or puffs of different duration and eruption heights. Resolving such complex eruption dynamics is required for precise volcanic plume dispersion forecast...
Preprint
Full-text available
Recent advances in geostationary imaging have enabled the derivation of high spatiotemporal-resolution cloud-motion winds for the study of mesoscale unsteady flows. Due to the general absence of ground truth, the quality assessment of satellite winds is challenging. In the current limited practice, straightforward plausibility checks on the smoothn...
Preprint
Full-text available
A geometric technique is introduced to estimate the height of volcanic eruption columns using the generally discarded near-limb portion of geostationary imagery. Such oblique observations facilitate a height-by-angle estimation method by offering close to orthogonal side views of eruption columns protruding from the Earth ellipsoid. Coverage is res...
Preprint
Full-text available
In a companion paper (Horváth et al., 2021), we introduced a new technique to estimate volcanic eruption column height from extremely oblique near-limb geostationary views. The current paper demonstrates and validates the technique in a number of recent eruptions, ranging from ones with weak columnar plumes to subplinian events with massive umbrell...
Article
Full-text available
Current state-of-the-art regional numerical weather prediction (NWP) models employ kilometer-scale horizontal grid resolutions, thereby simulating convection within the grey zone. Increasing resolution leads to resolving the 3D motion field and has been shown to improve the representation of clouds and precipitation. Using a hectometer-scale model...
Article
Estimating the impact of convection on the upper-tropospheric water budget remains a problem for models employing resolutions of several kilometers or more. A sub-kilometer high-resolution model is used to study summertime convection. The results suggest mostly close agreement with ground- and satellite-based observational data while slightly overe...
Article
Full-text available
The mature inflorescence of sunflowers (Helianthus annuus) orients eastward after its anthesis (the flowering period, especially the maturing of the stamens), from which point it no longer tracks the Sun. Although several hypothetical explanations have been proposed for the ecological functions of this east facing, none have been tested. Here we pr...
Article
Full-text available
A correct and reliable forecast of volcanic plume dispersion is vital for aviation safety. This can only be achieved by representing all responsible physical and chemical processes (sources, sinks, and interactions) in the forecast models. The representation of the sources has been enhanced over the last decade, while the sinks and interactions hav...
Preprint
Full-text available
Current state of the art regional numerical weather prediction (NWP) models employ kilometre scale horizontal grid resolutions thereby simulating convection within its grey-zone. Increasing resolution leads to resolving the 3D motion field and has been shown to improve the representation of clouds and precipitation. Using a hectometer-scale model i...
Preprint
Full-text available
A correct and reliable forecast of volcanic plume dispersion is vital for aviation safety. This can only be achieved by representing all responsible physical and chemical processes (sources, sinks, and interactions) in the forecast models. The representation of the sources has been enhanced over the last decade, while the sinks and interactions hav...
Article
Full-text available
This paper provides an overview of the scientific background and the research objectives of the Research Unit “VolImpact” (Revisiting the volcanic impact on atmosphere and climate – preparations for the next big volcanic eruption, FOR 2820). VolImpact was recently funded by the Deutsche Forschungsgemeinschaft (DFG) and started in spring 2019. The m...
Article
Full-text available
Vortex streets formed in the stratocumulus‐capped wake of mountainous islands are the atmospheric analogues of the classic Kármán vortex street observed in laboratory flows past bluff bodies. The quantitative analysis of these mesoscale unsteady atmospheric flows has been hampered by the lack of satellite wind retrievals of sufficiently high spatia...
Data
Animation of GOES-16 local wind relative vorticity on 9 May 2018 between 14:37 and 22:32 UTC at 5-minute intervals. The median-filtered data were resampled on a 6.3-km UTM grid and smoothed with a 3x3-gridbox averaging window.
Data
Animation of GOES-16 local wind vectors on 9 May 2018 between 14:37 and 22:32 UTC at 5-minute intervals. The wind vectors were median-filtered and resampled without smoothing on a 6.3-km UTM grid and colored according to wind speed.
Data
Animation of GOES-16 local wind streamwise component U on 9 May 2018 between 14:37 and 22:32 UTC at 5-minute intervals. The median-filtered data were resampled on a 6.3-km UTM grid and smoothed with a 3x3-gridbox averaging window.
Data
Animation of GOES-16 band 7 (3.9 μm) and band 2 (0.64 μm) images of the Guadalupe study domain, mapped in cylindrical equidistant projection for the period between 9 May 2018, 00:02 UTC and 10 May 2018, 02:42 UTC at 5-minute intervals.
Data
Animation of GOES-16 local wind transverse component V on 9 May 2018 between 14:37 and 22:32 UTC at 5-minute intervals. The median-filtered data were resampled on a 6.3-km UTM grid and smoothed with a 3x3-gridbox averaging window.
Data
This supporting information provides the streamlines calculated from the wind vector fields plotted in Figures 5c, 6a-b-c-d, 10a, and 12a of the main article.
Preprint
Full-text available
Vortex streets formed in the stratocumulus-capped wake of mountainous islands are the atmospheric analogues of the classic Kármán vortex street observed in laboratory flows past bluff bodies. The quantitative analysis of these mesoscale unsteady atmospheric flows has been hampered by the lack of satellite wind retrievals of sufficiently high spatia...
Article
Full-text available
This study identifies meteorological variables that control the macrophysical properties of shallow cumulus cloud fields over the tropical ocean. We use 1,158 high-resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images to derive properties of shallow cumuli, such as their size distribution, cloud top heights, fract...
Article
Full-text available
This study identifies meteorological variables that control the macrophysical properties of shallow cumulus cloud fields over the tropical ocean. We use 1,158 high‐resolution Advanced Spaceborn Thermal Emission and Reflection Radiometer (ASTER) images to derive properties of shallow cumuli, such as their size distribution, cloud top heights, fracta...
Article
Full-text available
This paper provides an overview of the scientific background and the research objectives of the Research Unit “VolImpact” (Revisiting the volcanic impact on atmosphere and climate – preparations for the next big volcanic eruption, FOR 2820). VolImpact was recently funded by the Deutsche Forschungsgemeinschaft (DFG) and started in spring 2019. The m...
Article
Full-text available
Marine stratocumulus (Sc) clouds play an essential role in the earth radiation budget. Here, we compare liquid water path (LWP), cloud optical thickness (τ), and cloud droplet effective radius (re) retrievals from 2 years of collocated Spinning Enhanced Visible and Infrared Imager (SEVIRI), Moderate Resolution Imaging Spectroradiometer (MODIS), and...
Article
Full-text available
Marine stratocumulus (Sc) clouds play an essential role in the earth radiation budget. Here, we compare liquid water path (LWP), optical thickness (COT), and effective radius (CER) retrievals from two years of collocated Spinning Enhanced Visible and InfraRed Imager (SEVIRI), MODerate resolution Imaging Spectroradiometer (MODIS), and Tropical Rainf...
Article
Full-text available
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) MetOp-A and MetOp-B satellites fly in the same polar orbit with a 180° phase difference, which enables the global retrieval of atmospheric motion vectors (AMVs, or ''winds'') by tracking clouds in a pair of Advanced Very High Resolution Radiometer (AVHRR) infrare...
Article
Full-text available
Cloud motion vector (CMV) winds retrieved from the Multiangle Imaging SpectroRadiometer (MISR) instrument on the polar-orbiting Terra satellite from 2003 to 2008 are compared with collocated atmospheric motion vectors (AMVs) retrieved from Geostationary Operational Environmental Satellite (GOES) imagery over the tropics and midlatitudes and from Mo...
Article
Full-text available
Recent decades have witnessed a drastic increase in the fidelity of numerical weather prediction (NWP) modeling. Currently, both research-grade and operational NWP models regularly perform simulations with horizontal grid spacings as fine as 1 km. This migration towards higher resolution potentially improves NWP model solutions by increasing the re...
Article
Full-text available
Cloud cover estimation is an important part of routine meteorological observations. Cloudiness measurements are used in climate model evaluation, nowcasting solar radiation, parameterizing the fluctuations of sea surface insolation, and building energy transfer models of the atmosphere. Currently, the most widespread ground-based method to measure...
Article
Full-text available
We investigated the view angle dependence of domain mean Moderate Resolution Imaging Spectroradiometer (MODIS) liquid water path (LWP) and that of corresponding cloud optical thickness, effective radius, and liquid cloud fraction as proxy for plane-parallel retrieval biases. Independent Advanced Microwave Scanning Radiometer–EOS LWP was used to cor...
Conference Paper
Full-text available
The goal of this study was to perform a preliminary validation of EUMETSAT's soon-to-be-operational dual-mode METOP AMV (atmospheric motion vector or " wind ") product against other, well-established satellite-derived wind observations. The novel dual-mode wind retrieval technique takes advantage of the swath overlap between the METOP-A/METOP-B tan...
Article
Full-text available