A5049147203- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- GNSS positioning and interference
- Geomagnetism and Paleomagnetism Studies
- Earthquake Detection and Analysis
- Solar and Space Plasma Dynamics
- Climate variability and models
- Meteorological Phenomena and Simulations
- Astro and Planetary Science
- Planetary Science and Exploration
- Atmospheric and Environmental Gas Dynamics
- Spacecraft Design and Technology
- Geochemistry and Geologic Mapping
- Calibration and Measurement Techniques
- Geophysical and Geoelectrical Methods
- Tropical and Extratropical Cyclones Research
- Methane Hydrates and Related Phenomena
- Space exploration and regulation
- Scientific Research and Discoveries
- Arctic and Antarctic ice dynamics
- Impact of Light on Environment and Health
- Advanced Image Fusion Techniques
- Radiative Heat Transfer Studies
- Diverse Interdisciplinary Research Innovations
Danish Meteorological Institute
2014-2024
Swinburne University of Technology
2014
Lund University
1996-1999
To examine the claim that Global Positioning System (GPS) radio occultation (RO) data are useful as a benchmark set for climate monitoring, structural uncertainties of retrieved profiles result from different processing methods quantified. Profile‐to‐profile comparisons CHAMP (CHAllenging Minisatellite Payload) January 2002 to August 2008 by six RO centers presented. Differences and standard deviations individual relative inter‐center mean used quantify uncertainty. Uncertainties accumulate...
Abstract. Global Positioning System (GPS) radio occultation (RO) has provided continuous observations of the Earth's atmosphere since 2001 with global coverage, all-weather capability, and high accuracy vertical resolution in upper troposphere lower stratosphere (UTLS). Precise time measurements enable long-term stability but careful processing is needed. Here we provide climate-oriented atmospheric scientists multicenter-based results on RO climatological fields for trend studies. We...
Abstract Temperature observations of the upper-air atmosphere are now available for more than 40 years from both ground- and satellite-based observing systems. Recent have seen substantial improvements in reducing long-standing discrepancies among datasets through major reprocessing efforts. The advent radio occultation (RO) 2001 has led to further vertically resolved temperature measurements, enabling a detailed analysis upper-troposphere/lower-stratosphere trends. This paper presents...
[1] With data from the Canadian Magnetic Observatory System, Array for Real time Investigations of Activity, Geophysical Institute Magnetometer Array, Greenland, Time History Events and Macroscale Interactions during Substorms (THEMIS), Cusp Cleft Studies ground magnetometer arrays, we applied state-of-art technique on basis spherical elementary currents systems (SECS) developed by Amm Viljanen (1999) in order to calculate maps ionospheric equivalent over whole North American auroral region....
Despite numerous reports of apparent climate responses to the 11‐year solar cycle, Sun's role for weather and has remained a matter controversy. One important reason is difficulty reliably attributing observed atmospheric effects variability, rather than other forcing factors or intrinsic variability. Here we show that consistent patterns statistically significant signals emerge in all major observables throughout low‐ mid‐latitude troposphere, when El Niño volcanic are removed from...
Abstract. Atmospheric climate monitoring requires observations of high quality that conform to the criteria Global Climate Observing System (GCOS). Radio occultation (RO) data based on Positioning (GPS) signals are available since 2001 from several satellite missions with global coverage, accuracy, and vertical resolution in troposphere lower stratosphere. We assess consistency long-term stability multi-satellite RO for use as records. As a measure stability, we quantify structural...
Historically, observational information about atmospheric temperature has been limited due to a lack of suitable measurements. Recent advances in satellite observations provide new insight into the fine structure free atmosphere, with upper troposphere and lower stratosphere comprising essential components climate system. This is prerequisite for understanding complex processes this part which also known have large impact on surface climate. With unprecedented resolution, latest reveal...
We here present a model for real time forecasting of the geomagnetic index Dst . The consists recurrent neural network that has been optimized to be as small possible without degrading accuracy. It is driven solely by hourly averages solar wind magnetic field component B z , particle density n and velocity V which means does not rely on observed In an evaluation based more than 40,000 hours data, it shown this smaller errors other models currently in operational use. A complete description...
We investigate correlations between geomagnetic activity indices, the North Atlantic Oscillation (NAO), and stratospheric geopotential heights. It is shown that correlation index Ap NAO high significant since about 1970, it during winter only, was not before are dominated by quasi‐decadal scales of variability. Analysis spatial pattern correlations, restricted to Northern Hemisphere wintertime, shows sea‐level pressures heights found for period 1973–2000. However, 1949–1972 no at surface...
Abstract. We here present results from an evaluation of the Radio Occultation Meteorology Satellite Application Facility (ROM SAF) gridded monthly mean climate data record (CDR v1.0), based on Global Positioning System (GPS) radio occultation (RO) CHAMP (CHAllenging Minisatellite Payload), GRACE (Gravity Recovery and Climate Experiment), COSMIC (Constellation Observing for Meteorology, Ionosphere, Climate), Metop satellite missions. Systematic differences between RO missions, as well...
Abstract The emerging signal of climate change is now clearly evident in Global Navigation Satellite System (GNSS) radio occultation (RO) data, matching predictions made by models 15 years ago. observed RO trends represent well-understood responses to global warming, particular the widespread cooling lower stratosphere and warming troposphere. This demonstrates value measurements for monitoring, consistent with their information content use both weather forecasting atmospheric reanalyses.
Abstract. We have used time-delay feed-forward neural networks to compute the geomagnetic-activity index Dst one hour ahead from a temporal sequence of solar-wind data. The input data include density n, velocity V and southward component Bz interplanetary magnetic field. is not included in implement an explicit functional relationship between solar wind geomagnetic disturbance, including both direct time-delayed non-linear relations. In this study we especially consider influence varying...
Abstract Over the last 15 years, global mean surface temperatures exhibit only weak trends. Recent studies have attempted to attribute this so called temperature hiatus several causes, amongst them incomplete sampling of rapidly warming Arctic region. We here examine zonal trends in satellite‐based tropospheric data sets (based on from (Advanced) Microwave Sounding Unit and Global Navigation Satellite System Radio Occultation instruments) (HadCRUT4). Omission successively larger polar...
Abstract Temperature changes in the lower and middle stratosphere during 2001–2016 are evaluated using measurements from GPS Radio Occultation (RO) Advanced Microwave Sounding Unit (AMSU) aboard Aqua satellite. After downsampling of GPS‐RO profiles according to AMSU weighting functions, spatially seasonally resolved trends two data sets excellent agreement. The observations indicate that has cooled time period 2002–2016 at an average rate −0.14 ± 0.12 −0.36 0.14 K/decade, while no...
In the tropics, upper troposphere warms faster than lower and surface in response to increased greenhouse gas concentrations. This differential warming is a robust feature climate models. High-quality observational datasets confirm stronger at higher altitudes, but limitations observing systems have made it difficult accurately characterize vertical structure of observed temperature trends tropics. Additionally, low resolution most satellite-based data records with global coverage further...
The dissipative processes in the Earth's magnetosphere, such as ring current and auroral electrojets, depend on both external solar wind forcing factors internal to magnetosphere. Previous studies have shown that artificial neural networks are able compute index Dst very accurately from only data. In this study, we use model response of electrojets conditions. input consist 5‐min averaged data Earth‐orbiting spacecraft IMP 8, while output is electrojet AE . relationships between index,...
Mappings of geomagnetic perturbations are shown for different combinations the solar wind velocity, interplanetary magnetic field (IMF), and dipole tilt angle (season). Average maps were derived separately northward, eastward, vertical (downward) components disturbances, using spherical cap harmonics in least error fits sorted measurements. The source data obtained from 104 ground‐based magnetometer stations Northern Hemisphere at latitudes over 40° during years 1998 through 2001. Contour...
Equivalent ionospheric currents obtained with the spherical elementary current systems (SECS) method and derived from nearly 100 ground magnetometers spread over North America Greenland are compared flow vectors measured by SuperDARN radars during both summer winter seasons. This comparison is done a range of spatial separations, magnetic latitudes, local times, auroral electrojet activity to investigate under what conditions anti‐parallel one another. Our results show that in general...
Abstract Radio occultation (RO) by the Earth's atmosphere of transmitted signals Global Navigation Satellite Systems' satellites has improved numerical weather prediction, benefited atmospheric process studies, and benchmarked climate change its strong traceability to international definition second. Until now, research with RO been isolated few centers that actually data impracticable elsewhere because limitations on formats, organization volume data, download bandwidth, lack a database can...
This study shows how locally observed geomagnetic disturbances can be predicted from solar wind data with artificial neural network (ANN) techniques. After subtraction of a secularly varying base level, the horizontal components X Sq and Y quiet time daily variations are modeled radial basis function networks taking into account seasonal activity modulations. The remaining disturbance Δ gated delay local as input. field is not used input to networks, which thus constitute explicit nonlinear...
Abstract. The possibility of simplifying the retrieval scheme required to produce GNSS radio occultation refractivity climatologies is investigated. In a new, simplified approach, main statistical analysis performed in bending angle space and an estimate average profile then propagated through Abel transform. composed means medians ionospheric corrected angles up 80 km. Above that, observed exponentially extrapolated infinity using fixed priori scale height. new approach circumvents need...
Neural networks with internal feedback from the hidden nodes to input [ Elman , 1990] are developed for prediction of auroral electrojet index AE solar wind data. Unlike linear and nonlinear autoregressive moving‐aver age (ARMA) models, such free develop their own representation recurrent state variables. Further, they do not incorporate an explicit memory past states; is implicitly given by structure networks. It shown that network can predict around 70% observed variance using a single...
Abstract. We discuss the processing of GRAS radio occultation (RO) data done at Satellite Application Facility. The input consists operational near-real time bending angles from December 2010 Metop-A satellite operated by EUMETSAT. are processed an Abel inversion algorithm in combination with statistical optimization based on a two-parameter fit to MSIS climatology. compare retrieved refractivity analyses ECMWF. It is found that for global averages, mean differences ECMWF smaller than 0.2%...
This work presents a detailed multi‐instrument and modeling case study of an ion upflow event occurring over the Sondrestrom incoherent scatter radar on 17 February 2001. is used to demonstrate effectiveness previously developed optical estimator upflow. The applied in two step process: (1) near‐infrared (NIR) observations 700–850 nm wavelength range are inverted reconstruct energy distribution precipitating electrons then (2) reconstructed precipitation combined fluid‐kinetic model...