Title here
Summary here
Work
Saturation in Forcing Efficiency and Temperature Response of Large Volcanic Eruptions (2025)
Paper | Journal of Geophysical Research: Atmospheres, 130(9), e2024JD041098 Authors: Eirik Rolland Enger, Rune Graversen, Audun Theodorsen
Abstract
Volcanic eruptions cause climate cooling due to the reflection of solar radiation by emitted and subsequently produced aerosols. The climate effect of an eruption may last for about a decade and is nonlinearly tied to the amount of injected SO₂ from the eruption. We investigate the climatic effects of volcanic eruptions, ranging from Mt. Pinatubo-sized events to supereruptions. The study is based on ensemble simulations in the Community Earth System Model Version 2 (CESM2) climate model applying the Whole Atmosphere Community Climate Model Version 6 (WACCM6) atmosphere model, using a coupled ocean and fixed sea surface temperature setting. Our analysis focuses on the impact of different levels of SO₂ injections on stratospheric aerosol optical depth (SAOD), effective radiative forcing (ERF), and global mean surface temperature (GMST) anomalies. We uncover a notable time-dependent decrease in aerosol forcing efficiency (ERF normalized by SAOD) for all eruption SO₂ levels during the first posteruption year. In addition, it is revealed that the largest eruptions investigated in this study, including several previous supereruption simulations, provide peak ERF anomalies bounded at −65 W m⁻². Further, a close linear relationship between peak GMST and ERF effectively bounds the GMST anomaly to, at most, approximately −10 K. This is consistent across several previous studies using different climate models.DOI: 10.1029/2024JD041098 Access: Available through AGU Publications (login required)
Nonparametric Estimation of Temperature Response to Volcanic Forcing (2025)
Paper | Journal of Geophysical Research: Atmospheres, 130(10), e2024JD042519 Authors: Eirik Rolland Enger, Rune Graversen, Audun Theodorsen
Abstract
Large volcanic eruptions strongly influence the internal variability of the climate system. Reliable estimates of the volcanic eruption response as simulated by climate models are needed to reconstruct past climate variability. Yet, the ability of models to represent the response to both single-eruption events and a combination of eruptions remains uncertain. We use the Community Earth System Model version 2 along with the Whole Atmosphere Community Climate Model version 6, known as CESM2(WACCM6), to study the global-mean surface temperature (GMST) response to idealized single volcano eruptions at the equator, ranging in size from Mt. Pinatubo-type events to supereruptions. Additionally, we simulate the GMST response to double-eruption events with eruption separations of a few years. For large idealized eruptions, we demonstrate that double-eruption events separated by 4 years combine linearly in terms of GMST response. In addition, the temporal development is similar across all single volcanic eruptions injecting at least 400 Tg (SO₂) into the atmosphere. Because only a few eruptions in the past millennium occurred within 4 years of a previous eruption, we assume that the historical record can be represented as a superposition of single-eruption events. Hence, we employ a deconvolution method to estimate a nonparametric historical GMST response pulse function for volcanic eruptions, based on climate simulation data from 850 to 1850 taken from a previous study. By applying the estimated GMST response pulse function, we can reconstruct most of the underlying historical GMST signal. Furthermore, the GMST response is significantly perturbed for at least 7 years following eruptions.DOI: 10.1029/2024JD042519 Access: Available through AGU Publications (login required)
A model for IS spectra for magnetized plasma with arbitrary isotropic velocity distributions (2020)
Thesis | University of Tromsø - The Arctic University of Norway
View Thesis | Download PDF | GitHub Repository
Abstract
The plasma line in the incoherent scatter spectrum is known to provide information about the state of the ionosphere. However, it is weak in signal strength and therefore difficult to measure reliably and consistently. When high-energetic electrons (suprathermal electrons) are present in the ionosphere the plasma line echo power is enhanced and detectable by more radars. Recent measurements made by the Arecibo radar show an altitude and aspect angle (angle between the radar beam and the magnetic field line) dependence on the returned echo power of the plasma line. This was assumed to be due to enhancements in the suprathermal electron velocity distribution but has neither been confirmed through theory nor numerical analysis. The theory describing the plasma line in the incoherent scatter spectrum due to scattering off thermal electrons has been known for a long time. This theory includes radar measurements at large angles to the magnetic field but a similar general derivation has not been formulated where suprathermal electrons are included in the distribution. In this work a derivation of the dielectric function which is a fundamental part of the derivation of the incoherent scatter spectrum was carried out for an arbitrary isotropic velocity distribution. Further, a program calculating the spectrum using the derived dielectric function was developed. The program was used to model the incoherent scatter spectrum for different electron velocity distributions and the echo power in the plasma line as a function of aspect angle and electron number density. It was shown that the enhancements found in the suprathermal distribution map to the structures found in the plasma line echo power, in line with the proposed explanation based on measurements. These findings support an aspect angle formula relating energy and received plasma resonance frequency based on the assumption that the main contributing factor to the resonance frequency are the electrons with velocity close to parallel to the magnetic field line.Next
Privacy Policy