Explore the vast range of titles available.

The eruption of the Hunga Tonga—Hunga Ha'apai (HTHH) volcano on 15 January 2022 injected about 150 Tg of water vapor (H2O), roughly 10% of the background stratospheric H2O content, to altitudes above 50 km. Simulations of the spatial evolution of the H2O cloud with the ICON‐Seamless model are very close to observations from the Aura Microwave Limb Sounder. The vertical transport of the H2O cloud had three phases: an initial subsidence phase, a stable phase, and a rising phase. Radiative cooling of H2O clearly affects the transport of the H2O cloud, as demonstrated with passive tracers, and is the main driver within the subsidence phase. It also counteracts the large‐scale rising motion in the tropics, leading to the stable phase, and modulates the large‐scale transport of the H2O cloud for about 9 months. This holds for different QBO phases, where the H2O cloud differs mainly in its vertical extent. Plain Language Summary The eruption of the Hunga Tonga—Hunga Ha'apai (HTHH) volcano on 15 January 2022 injected about 150 Tg water vapor (H2O) to an altitude above 50 km. This is more than 10% of the total stratospheric H2O content. We study the distribution of the H2O cloud and its ascent into the mesosphere using observations from the Aura Microwave Limb Sounder satellite and by performing simulations of the cloud with the ICON‐Seamless model. The vertical transport of the H2O cloud had three phases: a subsidence, a stable, and a rising phase. The temperature inside the H2O cloud is lower than outside the cloud. This causes the subsidence of the H2O cloud and has consequences for the transport during the next months. From October 2022 on, the transport is mainly determined by the large‐scale wind patterns. Key Points Radiative cooling of the H2O cloud influences the transport of the H2O cloud, stratospheric dynamics and, changes tracer transport Radiative cooling of the H2O cloud influences the cross equatorial transport of the H2O cloud The phase of the QBO modulates the large‐scale transport and the vertical extension of the HTHH cloud

The stratospheric aerosol layer plays an important role in the radiative balance of Earth primarily through scattering of solar radiation. The magnitude of this effect depends critically on the size distribution of the aerosol. The aerosol layer is in large part fed by volcanic eruptions strong enough to inject gaseous sulfur species into the stratosphere. The evolution of the stratospheric aerosol size after volcanic eruptions is currently one of the biggest uncertainties in stratospheric aerosol science. We retrieved aerosol particle size information from satellite solar occultation measurements from the Stratospheric Aerosol and Gas Experiment III mounted on the International Space Station (SAGE III/ISS) using a robust spectral method. We show that, surprisingly, some volcanic eruptions can lead to a decrease in average aerosol size, like the 2018 Ambae and the 2021 La Soufrière eruptions. In 2019 an intriguing contrast is observed, where the Raikoke eruption (48∘ N, 153∘ E) in 2019 led to the more expected stratospheric aerosol size increase, while the Ulawun eruptions (5∘ S, 151∘ E), which followed shortly after, again resulted in a reduction in the values of the median radius and absolute distribution width in the lowermost stratosphere. In addition, the Raikoke and Ulawun eruptions were simulated with the aerosol climate model MAECHAM5-HAM. In these model runs, the evolution of the extinction coefficient as well as of the effective radius could be reproduced well for the first 3 months of volcanic activity. However, the long lifetime of the very small aerosol sizes of many months observed in the satellite retrieval data could not be reproduced.

Stratospheric aerosols are an important component of the climate system. They not only change the radiative budget of the Earth but also play an essential role in ozone depletion. These impacts are particularly noticeable after volcanic eruptions when SO2 injected with the eruption reaches the stratosphere, oxidizes, and forms stratospheric aerosol. There have been several studies in which a volcanic eruption plume and the associated radiative forcing were analyzed using climate models and/or data from satellite measurements. However, few have compared vertically and temporally resolved volcanic plumes using both measured and modeled data. In this paper, we compared changes in the stratospheric aerosol loading after the 2018 Ambae eruption observed by satellite remote sensing measurements and simulated by a global aerosol model. We use vertical profiles of the aerosol extinction coefficient at 869 nm retrieved at the Institute of Environmental Physics (IUP) in Bremen from OMPS-LP (Ozone Mapping and Profiling Suite – Limb Profiler) observations. Here, we present the retrieval algorithm and a comparison of the obtained profiles with those from SAGE III/ISS (Stratospheric Aerosol and Gas Experiment III on board the International Space Station). The observed differences are within 25 % for most latitude bins, which indicates a reasonable quality of the retrieved limb aerosol extinction product. The volcanic plume evolution is investigated using both monthly mean aerosol extinction coefficients and 10 d averaged data. The measurement results were compared with the model output from MAECHAM5-HAM (ECHAM for short). In order to simulate the eruption accurately, we use SO2 injection estimates from OMPS and OMI (Ozone Monitoring Instrument) for the first phase of eruption and the TROPOspheric Monitoring Instrument (TROPOMI) for the second phase. Generally, the agreement between the vertical and geographical distribution of the aerosol extinction coefficient from OMPS-LP and ECHAM is quite remarkable, in particular, for the second phase. We attribute the good consistency between the model and the measurements to the precise estimation of injected SO2 mass and height, as well as to the nudging to ECMWF ERA5 reanalysis data. Additionally, we compared the radiative forcing (RF) caused by the increase in the aerosol loading in the stratosphere after the eruption. After accounting for the uncertainties from different RF calculation methods, the RFs from ECHAM and OMPS-LP agree quite well. We estimate the tropical (20∘ N to 20∘ S) RF from the second Ambae eruption to be about −0.13 W m−2.

The 2022 Hunga Tonga – Hunga Ha'apai eruption emitted approximately 150 Tg H2O into the middle atmosphere, which is still detectable 2 years after the event. Microwave Limb Sounder (MLS) observations show that the Hunga H2O reached the upper polar mesosphere in the Southern Hemisphere (SH) in the beginning of 2024, increasing the H2O mixing ratio in January by about 1 ppmv between 70 and 80° S up to an altitude of 83 km. No clear signal was detected for the noctilucent cloud occurrence frequency inferred from Ozone Mapping and Profiling Suite – Limb Profiler (OMPS-LP) measurements. It cannot, however, be ruled out that a slight increase from mid-January to February is potentially caused by the additional water vapour from the Hunga event. Several months later, the water vapour anomaly reached the polar summer mesopause region in the Northern Hemisphere (NH) during the noctilucent cloud season in 2024. However, a subsequent anomalous warming during the second half of the season might have hindered the ice particle formation, leading to a decrease in occurrence frequency of the mesospheric clouds compared to previous years. To summarize, based on the analysis performed in the study, we show that the volcanic water vapour needs 2 years to reach the summer polar mesopause region. This resembles the Krakatoa case that is argued to have caused the first sightings of noctilucent clouds 2 years after its eruption in 1883.

Explosive volcanic eruptions emitting large amounts of sulfur can alter the temperature of the lower stratosphere and change the circulation of the middle atmosphere. The dynamical response of the stratosphere to strong volcanic eruptions has been the subject of numerous studies. The impact of volcanic eruptions on the mesosphere is less well understood because of a lack of large eruptions in the satellite era and only sparse observations before that period. Nevertheless, some measurements indicated an increase in mesospheric mid-latitude temperatures after the 1991 Pinatubo eruption. The aim of this study is to uncover potential dynamical mechanisms that may lead to such a mesospheric temperature response. We use the Upper-Atmospheric ICOsahedral Non-hydrostatic (UA-ICON) model to simulate the atmospheric response to an idealized strong volcanic injection of 20 Tg S into the stratosphere (about twice as much as the eminent 1991 Pinatubo eruption). Two experiments with differently parameterized effects of sub-grid-scale orography are compared to test the impact of different atmospheric background states. The simulations show a significant warming of the polar summer mesopause of up to 15–21 K in the first November after the eruption. We argue that this is mainly due to intrahemispheric dynamical coupling in the summer hemisphere and is potentially enhanced by interhemispheric coupling with the winter stratosphere. This study focuses on the first austral summer after the eruption because mesospheric temperature anomalies are especially relevant for the properties of noctilucent clouds, whose season peaks around January in the Southern Hemisphere.

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 have received less attention. In particular, aerosol dynamic processes and aerosol–radiation interaction are neglected so far. Here we address this gap by further developing the ICON-ART (ICOsahedral Nonhydrostatic – Aerosols and Reactive Trace gases) global modeling system to account for these processes. We use this extended model for the simulation of volcanic aerosol dispersion after the Raikoke eruption in June 2019. Additionally, we validate the simulation results with measurements from AHI (Advanced Himawari Imager), CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), and OMPS-LP (Ozone Mapping and Profiling Suite-Limb Profiler). Our results show that around 50 % of very fine volcanic ash mass (particles with diameter d<30 µm) is removed due to particle growth and aging. Furthermore, the maximum volcanic cloud top height rises more than 6 km over the course of 4 d after the eruption due to aerosol–radiation interaction. This is the first direct evidence that shows how cumulative effects of aerosol dynamics and aerosol–radiation interaction lead to a more precise forecast of very fine ash lifetime in volcanic clouds.

The Mt. Pinatubo eruption in 1991 had a severe impact on the Earth system, with a well-documented warming of the tropical lower stratosphere and a general cooling of the surface. This study focuses on the impact of this event on the mesosphere by analyzing solar occultation temperature data from the Halogen Occultation Experiment (HALOE) instrument on the Upper Atmosphere Research Satellite (UARS). Previous analyses of lidar temperature data found positive temperature anomalies of up to 12.9 K in the upper mesosphere that peaked in 1993 and were attributed to the Pinatubo eruption. Fitting the HALOE data according to a previously published method indicates a maximum warming of the mesosphere region of 4.1 ± 1.4 K and does not confirm significantly higher values reported for that lidar time series. An alternative fit is proposed that assumes a more rapid response of the mesosphere to the volcanic event and approximates the signature of the Pinatubo with an exponential decay function having an e-folding time of 6 months. It suggests a maximum warming of 5.4 ± 3.0 K, if the mesospheric perturbation is assumed to reach its peak 4 months after the eruption. We conclude that the HALOE time series probably captures the decay of a Pinatubo-induced mesospheric warming at the beginning of its measurement period.

Presents results from a survey in the United States that provides some indication of how reading specialists fulfill their roles and how they offer students effective literacy instruction. Notes that the goal was to investigate what reading specialists do so that educators could better understand how they provide services to students and teachers. (SG)

The ReAch Early Intervention Program was created to help low-performing first and second grade students make progress in learning to read and meet standards of literacy that would permit them to perform successfully in their regular classrooms. The tutorial instruction was developed using Reading Recovery principles and research. However, instruction was delivered by instructional assistants—paraprofessionals who worked under the direction and the close supervision of the school reading specialist. Data from four years of the program in three pilot schools were analyzed to determine the amount of growth made by students from the beginning to the end of the intervention and to calculate the percentage of students achieving literacy standards established within the ReAch model. Results indicated that the program was successful in helping students make gains in reading achievement and attain levels of literacy which would allow success in the classroom. In addition, a treatment-control study was conducted to determine the significance of the gains. Multiple regression analysis revealed that ReAch students made significantly greater gains on program measures. The study also attempted to use scores from reading sub-tests of a standardized achievement test. However, no significant differences were noted, and correlation analysis suggested that the test was not a valid measure for these students. Discussion related to the role of program evaluation in support of the program design and implementation process has been included. The use of instructional assistants, or paraprofessionals, as tutors for students experiencing difficulty learning to read has been a major component of the ReAch program. The efficacy of using instructional assistants, or paraprofessionals in providing direct instruction to students is discussed.