Gottfried Kirchengast

Karl-Franzens-Universität Graz | KFU Graz · Wegener Center for Climate and Global Change

In our new MSc programme "Climate Change and Transformation Science", you will learn with internationally leading experts in climate science, climate economics and transformation science. You can choose to focus on natural science or social science aspects and study * the climate system, climate dynamics and climate change, * the connected risks of...

The kappa‐correction is an easy‐to‐use method to correct for residual ionospheric errors in radio occultation (RO) data. It is a simple empirical model term that only depends on readily available data. While its basic utility was well proven in previous studies, including a recent predecessor study on RO climatologies under solar cycle variations,...

Precipitation is a key input to hydrological models. While rain gauges provide the most direct precipitation measurements , their accuracy in capturing rain patterns highly depends on the spatial variability of rainfall events and the gauge network density. In this study, we employ a high-resolution meteorological station network (mean station dist...

The objective of the United Nations Paris Agreement to limit global warming to well below 2°C, with efforts to reach 1.5°C, requires a strict limitation of future global greenhouse gas (GHG) emissions based on a global carbon budget. Applying equity considerations allows for the derivation of national carbon budgets. A key question then arises: How...

Abstract A new model was recently introduced to correct for higher‐order ionospheric residual biases in radio occultation (RO) data. The model depends on the α1 and α2 dual‐frequency bending angle difference squared, and a factor κ, which varies with time, season, solar activity, and height, needing only the F10.7 solar radio flux index as addition...

Das CCCA wurde gebeten eine Stellungnahme zum Factsheet „Kostenwahrheit CO2“ (Entwurfsversion 20.03.2020) des Bundesministeriums für Klimaschutz (BMK) abzugeben. Das BMK sucht im Sinne des Regierungsprogrammes Wege um Kostenwahrheit für CO2-Emissionen herzustellen. Das BMK orientiert sich dabei an der „Methodenkonvention 3.0“ des deutschen Umweltbu...

The Global Navigation Satellite System (GNSS) Radio Occultation (RO) is a key technique for obtaining thermodynamic profiles of temperature, humidity, pressure, and density in the Earth’s troposphere. However, due to refraction effects of both the dry air and water vapor at low altitudes, retrieval of accurate profiles is challenging. Here we intro...

Ziel des Ref-NEKP ist im Sinne guter wissenschaftsseitiger Praxis im Dialog zwischen Wissenschaft und Politik keinen Plan vorzulegen, der vorgibt, was politisch zu machen sei, sondern mögliche Umsetzungswege darzustellen, mit denen Österreich wirklich seinen fairen und angemessenen Beitrag zu den Pariser Klimazielen erreichen kann (Stichwort policy...

Ziel des Ref-NEKP ist im Sinne guter wissenschaftsseitiger Praxis im Dialog zwischen Wissenschaft und Politik keinen Plan vorzulegen, der vorgibt, was politisch zu machen sei, sondern mögliche Umsetzungswege darzustellen, mit denen Österreich wirklich seinen fairen und angemessenen Beitrag zu den Pariser Klimazielen erreichen kann (Stichwort policy...

Large amounts of ash, aerosols and gases can be ejected from volcanoes during explosive eruptions into the troposphere, and occasionally into the stratosphere, affecting the atmospheric structure, human society and economy, and life on Earth in general both near and far away from the source. Detecting volcanic cloud top and bottom height at high ve...

Der Klimawandel ist Tatsache und hat zunehmend Auswirkungen auf die globale Wasserverfügbarkeit. Dürren, Extremniederschläge oder der Meeresspiegelanstieg bedrohen die Existenzgrundlage vieler Menschen weltweit. Migration ist eine Anpassungsmöglichkeit an solche veränderten Umweltbedingungen, wird jedoch von wirtschaftlichen, sozialen und politisch...

In March 2019, German-speaking scientists and scholars calling themselves Scientists for Future, published a statement in support of the youth protesters in Germany, Austria, and Switzerland (Fridays for Future, Klimastreik/Climate Strike), verifying the scientific evidence that the youth protestors refer to. In this article, they provide the full...

Potential increases in extreme rainfall induced hazards in a warming climate have motivated studies to link precipitation intensities to temperature. Increases exceeding the Clausius–Clapeyron (CC) rate of 6–7%/°C–1 are seen in short-duration, convective, high-percentile rainfall at mid latitudes, but the rates of change cease or revert at regional...

Eight years of daily rainfall data from WegenerNet were analyzed by comparison with data from Austrian national weather stations. WegenerNet includes 153 ground level weather stations in an area of about 15km×20km in the Feldbach region in southeast Austria. Rainfall has been measured by tipping bucket gauges at 150 stations of the network since th...

Global Navigation Satellite System radio occultation (GNSS RO, or in short GRO) has become a major method to observe the Earth's atmospheric thermodynamic state variables, i.e., pressure, temperature, and humidity as retrieved from refraction measurements using the GNSS radio wave signals. The GRO data products, such as bending angle and refractivi...

This paper addresses the representation of lower tropospheric water vapor in the meteorological analyses—fully detailed estimates of atmospheric state—providing the wide temporal and spatial coverage used in many process studies. Analyses are produced in a cycle combining short forecasts from initial conditions with data assimilation that optimally...

A deeper understanding of how clouds will respond to a warming climate is one of the outstanding challenges in climate science. Uncertainties in the response of clouds, and particularly shallow clouds, have been identified as the dominant source of the discrepancy in model estimates of equilibrium climate sensitivity. As the community gains a deepe...

The Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) is one of the new generation payloads onboard the Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth’s neutral atmosphere and ionosphere. GNOS was designed for acquiring setting and rising radio occultation (RO) data by using GNSS s...

Global Navigation Satellite System (GNSS) radio occultation (RO) observations are highly accurate, long-term stable data sets, and are globally available as a continuous record since 2001. Essential climate variables for the thermodynamic state of the free atmosphere, such as pressure, temperature and tropospheric water vapor profiles (involving ba...

The altitude of volcanic clouds and the atmospheric thermal structure after volcanic eruptions are studied using Global Navigation Satellite System (GNSS) Radio Occultation (RO) profiles co-located with independent radiometer images of ash and sulfur dioxide plumes. We use geographically co-located RO profiles to detect the top altitude of volcanic...

A new reference occultation processing system (rOPS) will include a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval chain with integrated uncertainty propagation. In this paper, we focus on wave-optics bending angle retrieval in the lower troposphere and introduce 1. an empirically estimated boundary layer bias (BLB) mode...

We introduce an operational weather diagnostics application for automatic generation of wind fields in near real-time from observations delivered by the high-density meteorological station network WegenerNet Feldbach region, Austria. Purpose of the application is to empirically provide near-surface wind fields of very high spatial and temporal reso...

Global Navigation Satellite System (GNSS) Radio Occultation (RO) observations, globally available as a continuous record since 2001 are highly accurate, and long-term stable data records. Essential climate variables for the thermodynamic state of the free atmosphere, such as temperature and tropospheric water vapor profiles (involving background in...

High-resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic at...

Poster presentation at Klimatag 2016, CCCA, Graz, Austria, 2016

We have developed a formula for the retrieval of the line-of-sight (l.o.s.) wind speed from future low Earth orbit (LEO) satellite-to-satellite infrared laser occultation measurements. The formula involves an Abelian integral transform akin to the Abel transform widely used for deriving refractive index from bending angle in Global Navigation Satel...

The volcanic cloud top altitude and the atmospheric thermal structure after volcanic eruptions are studied using Global Positioning System (GPS) Radio Occultation (RO) profiles co-located with independent radiometric measurements of ash and SO2 clouds. We use the GPS RO data to detect volcanic clouds and to analyze their impact on climate in terms...

The wave optical technique for bending angle retrieval in processing radio occultation observations is nowadays widely used by different data processing and assimilation groups and centers. This technique uses Fourier Integral Operators that map the observed records of the amplitude and phase into the impact parameter representation, which allows f...

We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS)-based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically varying uncertainty profiles and realistic global...

The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earth-orbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmi...

The radio occultation (RO) technique using signals from the Global Navigation Satellite System (GNSS), in particular from the Global Positioning System (GPS) so far, is currently widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source in RO mea...

The new mission concept of microwave and infrared-laser occultation between low-Earth-orbit satellites (LMIO) is designed to provide accurate and long-term stable profiles of atmospheric thermodynamic variables, greenhouse gases (GHGs), and line-of-sight (l.o.s.) wind speed with focus on the upper troposphere and lower stratosphere (UTLS). While th...

Observations from the GPS radio occultation (GPSRO) satellite technique and from the newly established GCOS Reference Upper Air Network (GRUAN) are both candidates to serve as reference observations in the Global Climate Observing System (GCOS). Such reference observations are key to decrease existing uncertainties in upper-air climate research. Th...

Deep convective systems, also more casually often just called storms, are destructive weather phenomena causing every year many deaths, injuries and damages and accounting for major economic losses in several countries. The number and intensity of such phenomena increased over the last decades in some areas of the globe, including Europe. Damages a...

During the night of 12 to 13 June 2011 an explosive eruption occurred at the Nabro volcano located in Eritrea (13.4°N, 41.7°E). This has been recognized as the largest volcanic eruption since Pinatubo 1991, ejecting ash and sulfur dioxide (SO2) into the atmosphere, spreading over more than 60 degrees in latitude and more than 100 degrees in longitu...

The ability of radar–rain gauge merging algorithms to precisely analyse convective precipitation patterns is of high interest for many applications, e.g. hydrological modelling, thunderstorm warnings, and, as a reference, to spatially validate numerical weather prediction models. However, due to drawbacks of methods like cross-validation and due to...

We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS) based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically-varying uncertainty profiles and realistic global...

The radio occultation (RO) technique using signals from the Global Navigation Satellite System (GNSS), in particular from the Global Positioning System (GPS) so far, is meanwhile widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source in RO mea...

The new mission concept of microwave and infrared-laser occultation between low-Earth-orbit satellites (LMIO) is designed to provide accurate and long-term stable profiles of atmospheric thermodynamic variables, greenhouse gases (GHGs), and line-of-sight (l.o.s.) wind speed with focus on the upper troposphere and lower stratosphere (UTLS). While th...

In this study, the effects of transverse refractive gradients in the ionosphere and in the lower atmosphere on GPS signal paths for both ground-based receivers and receivers on board low Earth orbital satellites are examined. A three-dimensional numerical ray tracing technique, based on geometrical optics, together with the models of the ionosphere...

We study the origin and escape of catastrophically outgassed volatiles (H2O, CO2) from exomoons with Earth-like densities and masses of 0.1, 0.5 and 1 M ⊕ orbiting an extra-solar gas giant inside the habitable zone of a young active solar-like star. We apply a radiation absorption and hydrodynamic upper atmosphere model to the three studied exomoon...

A theoretical study on the combination of a passive microwave and a GNSS radio occultation instrument, mounted on the International Space Station (ISS), was performed. Both instruments allow to deduce the atmospheric temperature profile. We combined realistically simulated date of the two highly synergistic sensors with the optimal estimation metho...

The thermal structure of Tropical Cyclones (TCs) in different ocean basins is studied using Global Positioning System (GPS) Radio Occultation (RO) measurements co-located with TCs' best tracks. The objective of this work is to understand the mutual influence of TCs and atmospheric parameters in different regions. We selected 5 more than 20 000 GPS...

The thermal structure of Tropical Cyclones (TCs) in different ocean basins is studied using Global Positioning System (GPS) Radio Occultation (RO) measurements co-located with TCs' best tracks. The objective of this work is to understand the mutual influence of TCs and atmospheric parameters in different regions. We selected more than 20 000 GPS RO...

The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between Low Earth Orbit satellites (LMIO) was performed in the Canary Islands between La Palma and Tenerife in July 2011. This experiment aimed to demonstrate the infrared-laser differential transmission p...

The new mission concept of microwave and infrared-laser occultation between Low Earth Orbit satellites (LMIO) is capable to provide accurate, consistent, and long-term stable measurements of many essential climate variables. These include temperature, humidity, key greenhouse gases (GHGs) such as carbon dioxide and methane, and line-of-sight wind s...

Observations from the GPS radio occultation (GPSRO) satellite technique and from the newly established GCOS Reference Upper Air Network (GRUAN) are both candidates to serve as reference observations in the Global Climate Observing System (GCOS). Such reference observations are key to decrease existing uncertainties in upper-air climate research. Th...

Global Positioning System (GPS) radio occultation (RO) measurements are proven highly useful for observing the thermal structure of the troposphere and stratosphere. Here we use RO data for the first time to derive climatological wind fields from sampling error-corrected geopotential height fields on isobaric surfaces from about 800 hPa to 3 hPa. W...

The ability of radar-rain gauge merging algorithms to precisely analyse convective precipitation patterns is of high interest for many applications, e.g. hydrological modelling. However, due to drawbacks of methods like cross-validation and due to the limited availability of reference datasets on high temporal and spatial scale, an adequate validat...

In order to investigate the effects of residual ionospheric errors (RIEs) on radio occultation (RO) temperature profiles due to solar activity, local time and azimuth of occultation plane, two simulation schemes have been conducted using the models of MSIS90 for atmosphere and 3D NeUoG for ionosphere, and a 3D ray tracing approach. The results show...

Tropical cyclones (TCs) are extreme weather events causing every year huge damages and several deaths.In some countries they are the natural catastrophes accounting for the major economic damages. The thermal structure of TCs gives important information on the cloud top height allowing for a better understanding of the troposphere-stratosphere tran...

Volcanic explosive eruptions affect economic, political and cultural activities. Major explosive eruptions, such as Mount Pinatubo in 1991, can also impact the Earth’s climate. They inject huge amounts of gas, aerosol and ash into the upper troposphere and lower stratosphere (UTLS) causing increased reflection of solar radiation back to space and c...

The Global Positioning System (GPS) Radio Occultation (RO) method provides estimation of atmospheric parameters such as bending angle, refractivity, temperature, pressure and water vapor with high accuracy, high vertical resolution and global coverage. We have used the WEGC OPSv5.6 dataset of GPS RO, collected in the period 2001-2012 from differen...