To improve the forecast accuracy of numerical weather prediction, it is essential to obtain better initial conditions by combining simulations and available observations via data assimilation. It has ...been known that a part of observations degrade the forecast accuracy. Detecting and discarding such detrimental observations via proactive quality control (PQC) could improve the forecast accuracy. However, conventional methods for diagnosing observation impacts require future observations as a reference state and PQC cannot be real‐time in general. This study proposes using machine learning (ML) trained by a time series of analyses to obtain a reference state without future observations and enable real‐time ML‐based PQC. This study presents proof‐of‐concept using a low‐dimensional dynamical system. The results indicate that ML‐based and model‐based estimates of observation impacts are generally consistent. Furthermore, ML‐based real‐time PQC successfully improves the forecast accuracy compared to a baseline experiment without PQC.
Plain Language Summary
Simulation‐based weather prediction needs observations to obtain accurate initial conditions and to improve the forecast accuracy. However, it has been reported that a part of observations degrade the forecast accuracy. Detecting such detrimental observations using future observations and proactively denying them could result in skillful predictions. This approach is referred to as proactive quality control (PQC) and cannot be real‐time in general because PQC uses future information. To enable real‐time PQC, this study proposes using machine learning (ML) predictions instead of future observations in PQC. This study demonstrates for the first time that ML‐based real‐time PQC successfully improves the forecast accuracy in a low‐dimensional dynamical system. Future research could apply ML‐based PQC for more complicated weather prediction systems.
Key Points
Proactive quality control (PQC) uses future information for detecting detrimental observations and cannot be real‐time in general
We propose using machine learning (ML) predictions instead of future information and enabling real‐time PQC
ML‐based real‐time PQC successfully improves the forecast accuracy in a low‐dimensional dynamical system
Recently, secondary organic aerosols (SOAs) generated from anthropogenic volatile organic compounds have been proposed as a possible source of light-absorbing organic compounds, "brown carbon," in ...the urban atmosphere. However, the atmospheric importance of these SOAs remains unclear due to limited information about their optical properties. In this study, the complex refractive index (RI, m = n-ki values at 405, 532, and 781 nm of the SOAs generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx = NO + NO2 ) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring-down spectroscopy (CRDS). The complex RI-values obtained in the present study and reported in the literature indicate that the k-value, which represents the light absorption of the toluene-SOAs, increased to shorter wavelengths at <532 nm, and the n-value also increased to shorter wavelengths from 781 to 355 nm. The k-values at 405 nm were found to increase from 0.0018 to 0.0072 with increasing initial NOx concentration from 109 to 571 ppbv. The nitrate to organics ratio of the SOAs determined using a high-resolution time-of-flight aerosol mass spectrometer (H-ToF-AMS) also increased with increasing initial NOx concentration. The RI-values of the SOAs generated during the photooxidation of 1,3,5-trimethylbenzene in the presence of NOx (1,3,5-TMB-SOAs) were also determined to investigate the influence of the chemical structure of the precursor on the optical properties of the SOAs, and it was found that the light absorption of the 1,3,5-TMB-SOAs is negligible at all of the wavelengths investigated (405, 532, and 781 nm). These results can be reasonably explained by the hypothesis that nitroaromatic compounds, such as nitrocresols, are the major contributors to the light absorption of the toluene-SOAs. Using the obtained RI-values, mass absorption cross sections of the toluene-SOAs at 405 nm were estimated to be 0.08-0.52 m2 g-1 under typical conditions in an urban atmosphere during the daytime. These results indicate that light absorption by the SOAs potentially contributes to the radiation balance at ultraviolet wavelengths below ~400 nm, specifically when the mass concentrations of the anthropogenic SOAs are significant compared with other light-absorbing particles.
We present the first comparison of Jupiter's auroral morphology with an extended, continuous, and complete set of near‐Jupiter interplanetary data, revealing the response of Jupiter's auroras to the ...interplanetary conditions. We show that for ∼1–3 days following compression region onset, the planet's main emission brightened. A duskside poleward region also brightened during compressions, as well as during shallow rarefaction conditions at the start of the program. The power emitted from the noon active region did not exhibit dependence on any interplanetary parameter, though the morphology typically differed between rarefactions and compressions. The auroras equatorward of the main emission brightened over ∼10 days following an interval of increased volcanic activity on Io. These results show that the dependence of Jupiter's magnetosphere and auroras on the interplanetary conditions are more diverse than previously thought.
Plain Language Summary
Jupiter's auroras (northern lights) are the brightest in the solar system, over a hundred times brighter than the Earth's. Auroras on Earth are driven by the solar wind, a million mile‐per‐hour stream of charged particles flowing away from the Sun, hitting the Earth's magnetic field, and stirring it around, but it is not known whether the solar wind causes any significant auroras on Jupiter. The main reason for this uncertainty is a lack of observations of the planet's auroras obtained while spacecraft have been near Jupiter and able to supply a full and continuous set of measurements of the solar wind and its accompanying magnetic field. In early mid‐2016 Juno approached Jupiter, providing such an interplanetary data set, and we obtained over a month's worth of observations of Jupiter's auroras using the Hubble Space Telescope. We saw several solar wind storms, each causing auroral fireworks on Jupiter. We captured the most powerful auroras observed by Hubble to date, brightened main oval emissions, and flashing high‐latitude patches of auroras during the solar wind storms. These results indicate that Jupiter's auroral response to the solar wind is more diverse than we previously have thought.
Key Points
We present the first comparison of Jupiter's auroras with an extended and complete set of near‐Jupiter interplanetary data
During compressions, the well‐defined sector of Jupiter's emission and the dusk poleward region brightened, the latter pulsating
The power emitted from the noon active region did not exhibit dependence on any interplanetary parameter, though the morphology changed
Terrestrial exoplanets orbiting within or near their host stars' habitable zone are potentially apt for life. It has been proposed that time-series measurements of reflected starlight from such ...planets will reveal their rotational period, main surface features and some atmospheric information. From imagery obtained with the Akatsuki spacecraft, here we show that Venus' brightness at 283, 365, and 2020 nm is modulated by one or both of two periods of 3.7 and 4.6 days, and typical amplitudes <10% but occasional events of 20-40%. The modulations are unrelated to the solid-body rotation; they are caused by planetary-scale waves superimposed on the super-rotating winds. Here we propose that two modulation periods whose ratio of large-to-small values is not an integer number imply the existence of an atmosphere if detected at an exoplanet, but it remains ambiguous whether the atmosphere is optically thin or thick, as for Earth or Venus respectively. Multi-wavelength and long temporal baseline observations may be required to decide between these scenarios. Ultimately, Venus represents a false positive for interpretations of brightness modulations of terrestrial exoplanets in terms of surface features.
Since the first discovery of Jovian Synchrotron Radiation (JSR) from Jovian radiation belt in late 1950s, origin of its time variations has been one of the main subjects of the Jovian radiation belt ...study. JSR is reported to be strongly correlated with solar wind ram pressure with a possible time lag, which remains an unsolved issue. In our study, the influence of dawn‐to‐dusk electric field modulated with solar wind ram pressure on JSR variations is investigated. Alongside the original diffusion coefficient (DLL(UV)), a new diffusion coefficient (DLL(Elec)) which is dependent on solar wind conditions is applied to a one‐dimensional lossy radial diffusion model, and we reproduce long‐term variations of JSR between 1971 and early 2018. For the specific choice of DLL(UV) = 3.0 × 10−10L3s−1, the correlation coefficient is found to be 0.6 between the simulated JSR and the ground observation data prior to 2005, and the intermittent observation after 2005 supports our simulation as well. We suggest that while DLL(UV) is the primary mode of diffusion that determines the steady profile of electron population and JSR, DLL(Elec) serves as a secondary mode, which controls long‐term variations of JSR.
Key Points
Radial diffusion coefficient derived from dawn‐to‐dusk electric field fluctuations controlled by solar wind conditions is introduced
The coefficient is comparable to dynamo electric field influence on Jupiter's upper atmosphere at the outer part of the radiation belt
Our radial diffusion model provides the best reproduction of Jovian synchrotron radiation observed in the past
Embedded deep inside the huge magnetosphere of Jupiter, the moon Io has active volcanos. Jovian magnetospheric dynamics are driven by the expulsion of Iogenic plasma in the strongly magnetized, ...fast‐rotating system and should vary in response to Io's volcanic activity. In early 2015 when various observations indicated an increase in volcanic activity, the EXCEED instrument onboard the Hisaki spacecraft continuously observed the Jovian magnetosphere via the aurora emission and the emission from the Io plasma torus. The plasma diagnosis of the enhanced Io plasma torus spectrum along with a physical chemistry model for deducing plasma parameters revealed a higher plasma density and a 2–4 times faster radial flow as compared with a volcanically quiet period. Aurora emissions reflecting midmagnetospheric activities showed multiple highly elevated brightness peaks about a month later. Long‐term and continuous monitoring by Hisaki enabled the first comprehensive observations of the Jovian magnetosphere in response to Io's enhanced volcanic activity.
Plain Language Summary
This article, based on the high‐resolution and continuous extreme ultraviolet spectroscopic data taken by the Japanese Hisaki satellite, shows that the plasma dynamics in the Jovian magnetosphere is highly influenced by Io's volcanic activity. The observations were made continuously from the beginning to end of a volcanic event. Through the detailed analysis of the spectra around Io's orbit and the Jovian aurora, and by fitting the data to a physical chemistry model, this first comprehensive study concludes that the plasma transport within the magnetosphere is enhanced by a factor of 2–4 by Io's volcanic activity.
Key Points
Continuous remote observations of the Io plasma torus were made by Hisaki from beginning to end of an Io volcanic event in January 2015
The plasma parameters and transport timescales were deduced through a detailed analysis of the spectra and physical chemistry model
Plasma transport timescale and source strength were enhanced and changed from 34 to 9.9 days and 0.7 to 3.0 tons/s by Io's volcanic activity, respectively
We summarize Jupiter's ultraviolet (UV) auroral response to solar wind dynamic pressure variations during Juno's approach to Jupiter in 2016. The response time of Jupiter's aurora to external drivers ...has thus far been unknown owing to a sparsity of upstream in situ solar wind measurements. Combining the Juno solar wind observations with continuous UV aurora data obtained by Hisaki EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) and Juno UV spectrograph, the UV aurora brightenings in response to three major shock arrivals showed time lags of 10–15 hr. These time lags are longer than the time required for ballistic propagation of the shocks by the solar wind. In addition to that puzzle, while an enhancement in the UV auroral power was observed with an increase in dynamic pressure to ~0.03 nPa, no associated brightening was observed with a dynamic pressure elevation of >0.1 nPa. These imply that internal magnetospheric aspects need to be taken into consideration to fully resolve the issue.
Plain Language Summary
Jovian ultraviolet aurora are emitted from hydrogen molecules in Jupiter's atmosphere when energetic electrons precipitate from the magnetosphere to excite the atmospheric molecules. The Jovian magnetosphere is always under the influence of the solar wind. Variation in the solar wind affects magnetospheric dynamics and thus the Jovian aurora intensity. The solar wind‐magnetosphere interaction is well studied for Earth, and the issue of aurora response to the solar wind is also well studied for Earth, but the issue remains open for Jupiter. Here we obtain the response time of aurora brightening upon intensification of the solar wind, which is a very fundamental quantity, to find it to be too long to be explained by a simple propagating model that assumes the solar wind as the dominant driver. Furthermore, some small variations in solar wind shocks led to aurora brightenings, while larger variations did not trigger other events. The characteristics discussed in this paper provide good case studies to validate theories or numerical simulations of how Jovian aurora may respond to changes in the solar wind.
Key Points
We compare Jupiter's ultraviolet aurora variation observed by Hisaki with changes in the upstream solar wind conditions observed by Juno
Transient brightenings responded to major solar wind shocks with ~10 hr lag time, which is inconsistent with a solar wind propagation model
A brightening triggered by a dynamic pressure elevation of 0.03 nPa was detected, whereas a 0.1 nPa elevation did not trigger a brightening
Contents
Environmental factors such as the temperature–humidity index (THI) are known to affect reproductive parameters in cattle. Therefore, here, we examined whether there was any correlation ...between the THI and the reproductive performance of Japanese Black cattle by analysing the first‐service conception rates of 178,492 artificially inseminated cows across 9,833 herds in south‐western Japan over a 3‐year period. The daily mean (±SD) THI over the study period was 63.6 ± 11.3 (range: 41.4–81.5). The calving to first artificial insemination (AI) interval was significantly negatively correlated with THI in the month of AI (r = −.75, p < .001), whereas conception rate to first AI (CRFA) showed a cyclical change that did not correspond with that of THI, resulting in a time lag between CRFA and THI in the month of AI. Furthermore, there was a stronger correlation between CRFA and THI between 3 and 2 months before AI (r = .76 vs. .83, p < .001) than in the month of AI (r = .34, p = .04). Therefore, this extensive field study showed that a decrease in THI was associated with declined reproductive performance in Japanese Black cattle and that the impact of the cold environment on the conception rate is attributable to a carryover effect from the cold season before AI rather than conditions at the time of AI.
Abstract
The satellite Io, which has volcanoes and is located at 5.9
R
J
from the center of Jupiter, is a powerful plasma source in the magnetosphere. The heavy ions originating from Io form a ...torus‐like structure and emit radiation. The pickup energy and hot electrons are believed to power the Io plasma torus. Voyager data showed that a trace amount of hot electrons (at several hundreds of eV) exist in the torus. The origin of hot electrons, that is, plasma heating and/or transport mechanisms, have been mentioned in previous research. However, the contribution of each mechanism toward supplying hot electrons remains poorly understood. To address this issue, we explored the time variation and spatial structure of hot electrons by spectroscopic observations using the Hisaki satellite. In this study, the radial distributions of plasma densities and temperatures were derived from the emission line intensities in the extreme ultraviolet range of day of year (DOY) 331 in 2014 to DOY 134 in 2015, which includes the Io's volcanically active period. We found that hot electrons inside the torus began to increase particularly on the duskside ~40 days after the onset of volcanic activity. This result suggests that the mass increase in the torus with volcanic activity enhanced the plasma transport from the outside within a specific region or via a local heating process.
Key Points
Long‐term continuous monitoring revealed that the plasma environment around Jupiter fluctuated coincident with Io's volcanic activity
Around 40 days after the volcanic activity starts, hot electron components inside the torus began to increase especially on the duskside
We present evidence that enhanced mass production produces either increased inward transport of hot electrons or local heating
In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous ...imaging made by the Hubble Space Telescope (HST) suggested that the transient aurora is associated with a global magnetospheric disturbance that spans from the inner to outer magnetosphere. However, the temporal and spatial evolutions of the magnetospheric disturbance were not resolved because of the lack of continuous monitoring of the transient aurora simultaneously with the imaging. Here we report the coordinated observation of the aurora and plasma torus made by Hisaki and HST during the approach phase of the Juno spacecraft in mid‐2016. On day 142, Hisaki detected a transient aurora with a maximum total H2 emission power of ~8.5 TW. The simultaneous HST imaging was indicative of a large “dawn storm,” which is associated with tail reconnection, at the onset of the transient aurora. The outer emission, which is associated with hot plasma injection in the inner magnetosphere, followed the dawn storm within less than two Jupiter rotations. The monitoring of the torus with Hisaki indicated that the hot plasma population increased in the torus during the transient aurora. These results imply that the magnetospheric disturbance is initiated via the tail reconnection and rapidly expands toward the inner magnetosphere, followed by the hot plasma injection reaching the plasma torus. This corresponds to the radially inward transport of the plasma and/or energy from the outer to the inner magnetosphere.
Key Points
By monitoring of Jupiter with Hisaki and HST we discovered that dawn storm is followed by outer emission during transient aurora
The monitoring with Hisaki indicated hot electron injection in the plasma torus during the declining phase of the transient aurora
Energy for these disturbances is likely released via tail reconnection and transported to the plasma torus within a few Jupiter rotations
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