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Saffron is an extremely high-value spice made from the dried stigmas of the saffron crocus (Crocus sativus). The saffron crocus flowers in the fall, grows vegetatively during the winter and spring, and is dormant during the summer. It is native to the Mediterranean region and most of the global saffron crop is produced in the Mediterranean and western Asia. Summer rainfall is rare in these regions. However, saffron crocus is becoming increasingly popular as a niche crop in the northeastern United States and other areas where summer rainfall is common. This study evaluated four methods of weed control during summer dormancy to determine the relative costs and the effects on saffron yield. Hand cultivation (HC) was the most expensive method and resulted in significantly decreased saffron yields. Covering the saffron crocus field with a light-proof plastic tarp (occultation) was the least expensive and had no effect on saffron yield. Annual planting of saffron crocus also had no effect on saffron yield but required more labor than occultation. Intercropping basil (Ocimum basilicum) resulted in the highest revenue per unit area and did not negatively affect yields of either saffron or basil. Based on this study intercropping is recommended for summer weed management for producers seeking to maximize revenue per unit area, while occultation is recommended for producers seeking to minimize production costs.

Using JWST observations of a primary transit and two secondary eclipses for GJ 1214b, we determine an eccentricity that is more precise than a decade of HARPS data, which enables us to measure the stellar density to 2.62%. Coupled with a prior on the stellar mass from a dynamically calibrated K _S – M _* relation, we determine R _* to 1.13%—3 times more precise than any other published analysis of this system. Then, using the bolometric flux from a spectral energy distribution model, we determine T _eff to 1.39%—40% more precise than systematic floors from spectroscopy. Within the global model, these also improve the planetary radius and insolation. This is a proof of concept for a new method to determine accurate R _* and T _eff to a precision currently achieved for only a small number of low-mass stars. By applying our method to all high signal-to-noise ratio planetary transits and occultations, we can expand the sample of precisely measured stars without assuming tidal circularization and calibrate new relations to improve our understanding of all low-mass stars.

Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have flown on small satellites with the goal "to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth's ionosphere and thermosphere." The primary science instrument is the Amptek X123 X-ray spectrometer that has improved with each generation of the MinXSS experiment. This third-generation MinXSS-3 has a higher energy resolution and larger effective area than its predecessors and is also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022 February 14, and INSPIRESat-1 has successfully completed its 6 month prime mission. The INSPIRESat-1 is in a dawn–dusk, Sun-synchronous orbit and therefore has had 24 hr coverage of the Sun during most of its mission so far. The rise of Solar Cycle 25 has been observed by DAXSS. This paper introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the science results here on a solar occultation experiment and multiple flares on 2022 April 24. One key flare result is that the reduction of elemental abundances appears greatest during the flare impulsive phase, thus highlighting the important role of chromospheric evaporation during flares to inject warmer plasma into the coronal loops. Furthermore, these results are suggestive that the amount of chromospheric evaporation is related to flare temperature and intensity. [ABSTRACT FROM AUTHOR]

Based on observations from the K2 mission of the Kepler Space Telescope a study is made of the activity of EPIC 204376071, a young object in the Upper SCO association with an age of 11±3 million years whose light curve has a single darkening lasting one day with a depth of about 80%. EPIC 204376071 is a low-mass M-dwarf with a mass of 0.16 M⨀. Based on observations from the C15 campaign of the K2 mission we refined the rotation period and the amplitude of the variability of the star's brightness, and also estimated the absolute magnitude of the spottedness parameter A by the standard method. The magnitude of the star's rotation period, P, equals 1.6270 ± 0.030 days. The area of the spots on the surface of EPIC 204376071 exceeds the maximum spot area on the sun and is on the order of 7900 msh. The results of a recovery of the temperature inhomogeneities on the surface of EPIC 204376071 are presented. Two cold regions separated in longitude by roughly 150° can be distinguished on the constructed chart. For estimating the properties of the flare activity of EPIC 204376071 one of the most reliable flares with a brightness amplitude of about 4% was examined. The measured relative energy RE of the flare was 212 s. The calculated energy Efl of the flare turned out to be equal to 1.1·1034 erg (logEfl = 34.05). The probable coronal mass ejection corresponding to it may reach 4.1·1020 g. Published data on the possible nature of the single occultation of diurnal duration with a depth of about 80% on the light curve of EPIC 204376071 are examined. [ABSTRACT FROM AUTHOR]

Tatabbo', in different aspects of Mahdism, is the completion of parts that provide Mahdism scholars with a more comprehensive picture of this issue and its various angles, which is the way to solve problems related to Mahdism. Following different aspects of Mahdism means completing parts that provide a more comprehensive picture of this issue and its different angles to Mahdism scholars, which is the way to solve problems related to Mahdism. One of the aspects of this discussion is the recognition of the works of Mahdavi Moteqadim. In this research, what has been investigated on the writings of Mahdavi Imamiya is a comprehensive typology in three axes, the authorship subject, the religion of the authors, and the time of writing the work in the three periods of presence, Minor Occultation, and Major Occultation until the fifth century. Based on this, in this article, all the narrative, theological, commentary, and historical works whose authors were Imams have been mentioned. In addition to the works written explicitly and specifically about Mahdism, various types of works that implicitly deal with Mahdism have also been identified. These works include: Books of Malahem, Books of Al-Awsiya, a book about Asna Ashar, books about Adad al-Aemah, books about the Nawab Arba’eh, and some books with the title of al-Imamah, as well as a book on miracles and a book on sectology. The results of this research show the quantitative and qualitative superiority of the works of the Imamiyyah Qateiah (Ithna'ashriyyah) compared to the sects that branched off from the Imamiyyah in all types of Mahdavi studies, as well as the non-reliance of the works of the Mahdavi Imamiyyah Qateiah on the works of the waqifah. In addition, from the beginning of major occultation until the fifth century, while there is nothing left of the Waqifs and their works, Imamiya's works have more than doubled.

The navigation by the stellar refraction is important for a LEO (Low-Earth-Orbit) satellite, especially in a GNSS (Global Navigation Satellite System)-denied environment, since it is totally autonomous. However, the biggest barrier to the accurate navigation by the stellar refraction lies in the accurate stratospheric density. Therefore, the retrieval of the stratospheric density by the star occultation is proposed in this paper to acquire the stratospheric density globally with the high accuracy. Compared with the retrieval of the stratospheric density by the GPS (Global Positioning System) radio occultation, the retrieval by the star occultation can achieve a high vertical resolution. The retrieval of the stratospheric density by the star occultation is first derived in principle. Then, the performance of the retrieval, including the spatial resolution, the atmospheric attenuation, and the accuracy, was investigated in detail. The performance of the retrieval was also comprehensively verified by simulations. The simulation results prove that the retrieval of the stratospheric density by the star occultation can achieve a similar accuracy to that by the GPS radio occultation, but it has a higher vertical resolution than that by the GPS radio occultation, which is good for improving the accuracy of the navigation by the stellar refraction. [ABSTRACT FROM AUTHOR]

The Oort cloud is presumably a pristine relic of the solar system formation. Detection of the Oort cloud may provide information regarding the stellar environment in which the Sun was born and on the planetesimal population during the outer planets’ formation phase. The best suggested approach for detecting Oort cloud objects in situ, is by searching for subsecond occultations of distant stars by these objects. Following Brown & Webster, we discuss the possibility of detecting Oort cloud objects by observing near the quadrature direction. Due to the Earth’s projected velocity, the occultations are longer near the quadrature direction and are therefore easier to detect, but have lower rate. We show that, for ≲1 m size telescopes, the increased exposure time will result in about one to 3 orders of magnitude increase in the number of detectable stars that have an angular size smaller than the Fresnel scale and are therefore suitable for an occultation search. We discuss the ability of this method to detect Oort cloud objects using existing survey telescopes, and we estimate the detection rate as a function of the power-law index of the size distribution of the Oort cloud objects and their distance from the Sun. We show that occultations detected using ≈1 s integration by ≲1 m telescopes at the optimal region near the quadrature points will be marginally dominated by Oort cloud objects rather than Kuiper belt objects.

At the time of Abbasid caliphate's determination to eliminate Imam Mahdi (AS), the most important responsibility of Imam Askari (A.S) was to protect his son by taking advantage of conventional human methods. On this basis, Imam took measures that, on the one hand, were the factor of preserving the honorable existence of Imam Mahdi (A.S), and on the other hand, were considered to be the basis for Shia's entry into the age of occultation. The present article, written with a descriptive-analytical method, indicates that Imam Hasan Askari (A.S) accomplished this important issue through the actions such as concealing the birth of a child, informing some relatives and friends about the birth of a child, and keeping Imam Mahdi away from Samearra.

Small-scale vegetable farmers are interested in cover crops and reduced tillage, but scale-appropriate technology and equipment are necessary to expand these practices to the growing segment of small farms. We sought to determine the efficacy of tarps, an increasingly popular tool on small farms, to end overwintering cover crops and provide weed suppression for subsequent no-till cabbage production. In three fields over two seasons in Maine, we grew a winter rye (Secale cereale L.) and hairy vetch (Vicia villosa L.) cover crop, which we managed by a factorial combination of tillage (no-till, till) and tarping (tarp, no-tarp) in June, followed by a transplanted cabbage crop (Brassica oleracea L. var. Capitata) in July. Within each treatment, subplots were either weeded by hand or left unweeded. Cover crop biomass ranged from 2.8 to 4.5 Mg⋅ha−1. Mean cabbage weights in the novel no-till system (no-till/tarp) were greater than (year 1) or equal to (year 2) those in tillage-based systems (till/no-tarp and till/tarp). In year 1, the mean cabbage weight in weeded subplots was 48% greater in no-till/tarp than in till/no-tarp systems. In unweeded subplots, this difference was 270%, highlighting the efficacy of the no-till/tarp system to reduce the impact of weeds. In year 2, weed biomass was higher with all treatments than it was in year 1, and unweeded subplots failed to produce marketable heads (i.e., >300 g). The mean cabbage weight in weeded subplots was equal among no-till/tarp, till/tarp, and till/no-tarp systems. Tarping had a strong effect on weed biomass and weed community composition measured at the time of cabbage harvest in unweeded subplots. In year 1, weed biomass at the time of cabbage harvest with tarp treatments was less than half that with no-tarp treatments. Tarps effectively facilitated the cover crop mulch-based no-till system. We propose that this system is an adaptive strategy for farmers affected by climate change. However, both cover crop production and tarping shorten the growing season. We discuss tradeoffs and opportunity costs using the metric of growing degree days.

Covering the soil surface with opaque plastic sheets to kill vegetation is referred to as tarping and is used by small-scale and organic growers to control weeds before planting crops. There are few published studies on tarping, and here we present a review of the literature in combination with observations from two on-farm case studies, one carried out in northern California and the other in northwestern Washington. An advantage of tarping is that it enables growers to control weeds without herbicides or tillage equipment, which can be cost-prohibitive for small-scale growers. Tarping is also suitable for no- or reduced-tillage systems, which is a primary goal for many small-scale and organic growers. Silage tarps that are 5 to 6 mils thick and black on one side and white on the other are most commonly used for tarping, are readily available new or used from some local agricultural suppliers or online, and can be reused for six or more seasons. Tarps are placed with the black side up to warm the soil, which encourages weed seed germination. When the soil is tilled and then tarped, a 3-week period with sufficient soil temperature and moisture is sufficient to kill emergent weeds in the top ≈1 inch of soil and provides a 95% to 100% weed-free surface at tarp removal. When a tarp is applied from autumn until spring to a plot that has established weeds, winter annual weeds can be controlled for several weeks after tarp removal, and then soil disturbance results in germination of additional weed seeds. For established perennial weeds, it may be necessary to extend the tarp application time to several months during critical weed growth phases or a full year to break the vegetative life cycle. Tarping does not reduce the weed seed bank, thus minimal soil disturbance after tarp removal is needed to maintain a reduced weed population during the cropping period.

Résumé : La présente contribution se donne pour objectif d’interroger l’éducation à la citoyenneté au collège dans les établissements d’enseignement secondaire public. Celle-ci s’organise autour de curricula permettant d’enseigner un certain nombre de savoirs, de normes et de valeurs légitimes de la société. Le développement durable étant encore largement considéré comme un savoir occidental, les orientations pédagogiques sur ces problématiques, censées préparer les jeunes élèves à faire face aux nouveaux défis du millénaire, ne proposent que rarement des contenus d’enseignement y relatifs. Or, avec les nombreux accords internationaux ratifiés et les mesures gouvernementales déployées depuis bientôt trois décennies, le Gabon apparaît comme un pays avant-gardiste sur les questions de développement durable avec un couvert forestier de plus de 80%. Ainsi, pourrait-on s’interroger sur l’existence d’un lien entre éducation à la citoyenneté des collégiens et développement durable. En d’autres termes, les manuels d’éducation civique au premier cycle de l’enseignement secondaire s’inscrivent-ils, peu ou prou, dans une perspective de légitimation des engagements internationaux pris par le Gabon dans le cadre des accords sur le développement durable ?

We present the technical design, construction and testing of the Colibri telescope array at Elginfield Observatory near London, Ontario, Canada. Three 50-cm telescopes are arranged in a triangular array and are separated by 110–160 m. During operation, they will monitor field stars at the intersections of the ecliptic and galactic plane for serendipitous stellar occultations (SSOs) by trans-Neptunian objects (TNOs). At a frame rate of 40 frames per second (fps), Fresnel diffraction in the occultation light curve can be resolved and, with coincident detections, be used to estimate basic properties of the occulting object. Using off-the-shelf components, the Colibri system streams imagery to disk at a rate of 1.5 GB/s for next-day processing by a custom occultation detection pipeline.The imaging system has been tested and is found to perform well, given the moderate site conditions. Limiting magnitudes at 40 fps are found to be about 12.1 (temporal SNR = 5, visible light Gaia G band) with time-series standard deviations ranging from about 0.035 mag to >0.2 mag. SNR is observed to decrease linearly with magnitude for stars fainter than about G = 9.5 mag. Brighter than this limit, SNR is constant, suggesting that atmospheric scintillation is the dominant noise source. Astrometric solutions show errors typically less than ±0.3 pixels (0.8 arc seconds) without a need for high-order corrections.

The navigation by the stellar refraction is important for a LEO (Low-Earth-Orbit) satellite, especially in a GNSS (Global Navigation Satellite System)-denied environment, since it is totally autonomous. However, the biggest barrier to the accurate navigation by the stellar refraction lies in the accurate stratospheric density. Therefore, the retrieval of the stratospheric density by the star occultation is proposed in this paper to acquire the stratospheric density globally with the high accuracy. Compared with the retrieval of the stratospheric density by the GPS (Global Positioning System) radio occultation, the retrieval by the star occultation can achieve a high vertical resolution. The retrieval of the stratospheric density by the star occultation is first derived in principle. Then, the performance of the retrieval, including the spatial resolution, the atmospheric attenuation, and the accuracy, was investigated in detail. The performance of the retrieval was also comprehensively verified by simulations. The simulation results prove that the retrieval of the stratospheric density by the star occultation can achieve a similar accuracy to that by the GPS radio occultation, but it has a higher vertical resolution than that by the GPS radio occultation, which is good for improving the accuracy of the navigation by the stellar refraction.

Small-scale vegetable farmers are interested in cover crops and reduced tillage, but scale-appropriate technology and equipment are necessary to expand these practices to the growing segment of small farms. We sought to determine the efficacy of tarps, an increasingly popular tool on small farms, to end overwintering cover crops and provide weed suppression for subsequent no-till cabbage production. In three fields over two seasons in Maine, we grew a winter rye (Secale cereale L.) and hairy vetch (Vicia villosa L.) cover crop, which we managed by a factorial combination of tillage (no-till, till) and tarping (tarp, no-tarp) in June, followed by a transplanted cabbage crop (Brassica oleracea L. var. Capitata) in July. Within each treatment, subplots were either weeded by hand or left unweeded. Cover crop biomass ranged from 2.8 to 4.5 Mg·ha−1 . Mean cabbage weights in the novel no-till system (no-till/tarp) were greater than (year 1) or equal to (year 2) those in tillage-based systems (till/no-tarp and till/tarp). In year 1, the mean cabbage weight in weeded subplots was 48% greater in no-till/tarp than in till/no-tarp systems. In unweeded subplots, this difference was 270%, highlighting the efficacy of the no-till/tarp system to reduce the impact of weeds. In year 2, weed biomass was higher with all treatments than it was in year 1, and unweeded subplots failed to produce marketable heads (i.e., >300 g). The mean cabbage weight in weeded subplots was equal among no-till/tarp, till/tarp, and till/no-tarp systems. Tarping had a strong effect on weed biomass and weed community composition measured at the time of cabbage harvest in unweeded subplots. In year 1, weed biomass at the time of cabbage harvest with tarp treatments was less than half that with no-tarp treatments. Tarps effectively facilitated the cover crop mulch-based no-till system. We propose that this system is an adaptive strategy for farmers affected by climate change. However, both cover crop production and tarping shorten the growing season. We discuss tradeoffs and opportunity costs using the metric of growing degree days. [ABSTRACT FROM AUTHOR]

No special political, social, and governmental approach or deployment has ever been expressed since the beginning of the school of Tafkik (distinguishment) by its founders so Hakimi is recognized in charge of explaining the different aspects of this school of thought. In this regard, the purpose of the present study is to investigate the place of politics and government in the school of Tafkik as mentioned in the works of Hakimi. Therefore, the main research question of the study aims to determine the foundations of the political and governmental ideology of Mohammad Reza Hakimi and his approach to the Islamic Revolution in Iran. The method of study is descriptive analysis and it relies on the hypothesis that the intellectual transformations of Hakimi can be interpreted within a “justice-centered” approach to the Islamic state and the profound impact of “function” on “theory” in his ideas. The results of the study show that the transformation of the political ideology of Mohammad Reza Hakimi before and after the establishment of the Islamic Republic of Iran has been from the guardianship of the Islamic jurist to Hey’ate-Nawwab in occultation and the Islamic state based on the guardianship of the Islamic jurist to the state of Masanekh.

Şia'nın günümüze kadar varlığını sürdüren en büyük ve en önemli kollarından biri İmâmiyye’dir. İmâmiyye Şiası, imamların sayısını on iki ile sınırlandırarak diğer Şiî gruplardan ayrışmıştır. Bu ayrışmayla birlikte İmâmiyye Şiası, bazı kavramları inanç esası haline getirerek kurumsal bir kimliğe kavuşmuştur. Konuyla alakalı çeşitli çalışmaları bulunan Prof. Dr. Cemil Hakyemez, İmâmiyye Şiası'nın bu temel kavramlarını açıklamak amacıyla İmâmiyye Şiası ve Temel Kavramları başlıklı bir eser kaleme almıştır. Eser, imâmet anlayışı etrafında şekillenen temel kavramların fikirsel arka planını, tarihsel süreç içerisinde başlıklar halinde incelemektedir. Bu doğrultuda çalışmamız, Hakyemez'in ilgili eseri üzerine bir değerlendirme niteliği taşımaktadır.

The purpose of the present study is to review the essence of government during occultation from the perspective of Seyed Ja’far Kashfi, one of the Shi’ite scholars in the Fath Ali Shah Qajar dynasty. In this regard descriptive analysis was used to survey the principles of political thinking, relationship between Seyed Ja’far Kashfi and Fath Ali Shah Qajar, necessity of government, various forms of government, and the characteristics of a ruler from his viewpoint. The results showed that Seyed Ja’far Kashfi, setting some strict conditions for the characteristics of a ruler jurist, did not acknowledge any of the jurists in his age as a qualified candidate for this position. This viewpoint is enough for him to defend the theory of simultaneous chairmanship of 2 learned scholars or twin rulers for the matter of norms and religious issues in society. In his view, a fair king would govern the worldly affairs as his validity and legitimacy exclusively comes from the Treaty of Malek Ashtar; and a jurist would govern religious affairs such as Hesbi issues (charity), judgement, mortmain property and so on. This theory that was also considered in later periods, is somehow a foundation for constitutionalism because it defends the authority of a king to govern the civil affairs not definitely mentioned in the Qur’anic verses (Gheyr-Mansusat) and the authority of a jurist to implement the definite rules in the Qur’an (Mansusat).

Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have flown on small satellites with the goal “to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth’s ionosphere and thermosphere.” The primary science instrument is the Amptek X123 X-ray spectrometer that has improved with each generation of the MinXSS experiment. This third-generation MinXSS-3 has a higher energy resolution and larger effective area than its predecessors and is also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022 February 14, and INSPIRESat-1 has successfully completed its 6 month prime mission. The INSPIRESat-1 is in a dawn–dusk, Sun-synchronous orbit and therefore has had 24 hr coverage of the Sun during most of its mission so far. The rise of Solar Cycle 25 has been observed by DAXSS. This paper introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the science results here on a solar occultation experiment and multiple flares on 2022 April 24. One key flare result is that the reduction of elemental abundances appears greatest during the flare impulsive phase, thus highlighting the important role of chromospheric evaporation during flares to inject warmer plasma into the coronal loops. Furthermore, these results are suggestive that the amount of chromospheric evaporation is related to flare temperature and intensity.

Radio occultation (RO) measurements have little direct sensitivity to clouds, but recent studies have shown that they may have an indirect sensitivity to thin, high clouds that are difficult to detect using conventional passive space-based cloud sensors. We implement two RO-based cloud detection (ROCD) algorithms for atmospheric layers in the middle and upper troposphere. The first algorithm is based on the methodology of a previous study, which explored signatures caused by upper-tropospheric clouds in RO profiles according to retrieved relative humidity, temperature lapse rate, and gradients in log-refractivity (ROCD-P), and the second is based on inferred relative humidity alone (ROCD-M). In both, atmospheric layers are independently predicted as cloudy or clear based on observational data, including high-performance RO retrievals. In a demonstration, we use data from 10 days spanning 7 months in 2020 of Formosa Satellite 7 (FORMOSAT-7)/COSMIC-2. We use the forecasts of NOAA GFS to aid in the retrieval of relative humidity. The prediction is validated with a cloud truth dataset created from the imagery of the GOES-16 Advanced Baseline Imager (ABI) satellite and the GFS three-dimensional analysis of cloud-state conditions. Given these two algorithms for the presence or absence of clouds, confusion matrices and receiver operating characteristic (ROC) curves are used to analyze how well these algorithms perform. The ROCD-M algorithm has a balanced accuracy, which defines the quality of the classification test that considers both the sensitivity and specificity, greater than 70% for all altitudes between 6 and 10.25 km. [ABSTRACT FROM AUTHOR]

We apply the three-cornered hat (3CH) method to estimate refractivity, bending angle, and specific humidity error variances for a number of datasets widely used in research and/or operations: radiosondes, radio occultation (COSMIC, COSMIC-2), NCEP global forecasts, and nine reanalyses. We use a large number and combinations of datasets to obtain insights into the impact of the error correlations among different datasets that affect 3CH estimates. Error correlations may be caused by actual correlations of errors, representativeness differences, or imperfect collocation of the datasets. We show that the 3CH method discriminates among the datasets and how error statistics of observations compare to state-of-the-art reanalyses and forecasts, as well as reanalyses that do not assimilate satellite data. We explore results for October and November 2006 and 2019 over different latitudinal regions and show error growth of the NCEP forecasts with time. Because of the importance of tropospheric water vapor to weather and climate, we compare error estimates of refractivity for dry and moist atmospheric conditions. [ABSTRACT FROM AUTHOR]

This study explores the importance of midlevel moisture for tropical cyclone (TC) formation in monsoon and easterly environments over the western North Pacific in regional simulations (15-km resolution). The Weather Research and Forecasting (WRF) Model is used to simulate 22 TCs that form in monsoon environments (MTCs) and 13 TCs that form in easterly environments (ETCs) over the period 2006–10. To characterize the moisture contribution, simulations with midlevel moisture improved through assimilation of global positioning system (GPS) radio occultation (RO) data (labeled as EPH) are compared to those without (labeled as GTS). In general, the probability of TC formation being detected in the simulations is higher for MTCs than ETCs, regardless of GPS RO assimilation, especially for the monsoon trough environment. In total, 54% of ETC formations are sensitive to the midlevel moisture patterns, while only 18% for MTC formations are sensitive, indicating that the importance of midlevel moisture is higher for ETC formations. Because of a model dry bias, the simulation of TC formation in an observed environment with lower vorticity but higher moisture is sensitive to the moisture increase through GPS RO data. Sensitivity experiments show that if the moisture in GTS is replaced by that in EPH, the TC formation can be detected in the GTS simulations. In turn, the TC formation cannot be detected in the EPH simulations with GTS moisture. The mechanism causing the difference in simulation performance of TC formation is attributed to more diabatic heating release and stronger positive potential vorticity tendency at midlevels around the disturbance center caused by the higher moisture magnitudes. [ABSTRACT FROM AUTHOR]

The FORMOSAT-7/COSMIC-2 Global Navigation Satellite System (GNSS) Radio Occultation (RO) satellite constellation was launched in June 2019 as a successor of the FORMOSAT-3/COSMIC mission. The Central Weather Bureau (CWB) of Taiwan has received FORMOSAT-7/COSMIC-2 GNSS RO data in real time from the Taiwan Analysis Center for COSMIC. With the global numerical prediction system at CWB, a parallel semioperational experiment assimilating the FORMOSAT-7/COSMIC-2 bending angle data with all other operational observation data has been conducted to evaluate the impact of the FORMOSAT-7/COSMIC-2 data. The first seven-month results show that the quality of the early FORMOSAT-7/COSMIC-2 data has been satisfactory for assimilation. Consistent and significant positive impacts on global forecast skills have been observed since the start of the parallel experiment, with the most significant impact found in the tropical region, reflecting the low-inclination orbital design of the satellites. The impact of the FORMOSAT-7/COSMIC-2 RO data is also estimated using the ensemble forecast sensitivity to observation impact (EFSOI) method, showing an average positive impact per observation similar to other existing GNSS RO datasets, while the total impact is impressive by virtue of its large amount. Sensitivity experiments suggest that the quality control processes built in the Gridpoint Statistical Interpolation (GSI) system for RO data work well to achieve a positive impact by the low-level FORMOSAT-7/COSMIC-2 RO data, while more effort on observation error tuning should be focused to obtain an optimal assimilation performance. This study demonstrates the usefulness of the FORMOSAT-7/COSMIC-2 RO data in global numerical weather prediction during the calibration/validation period and leads to the operational use of the data at CWB. Significance Statement: The importance of the Global Navigation Satellite System Radio Occultation measurement has been widely acknowledged by the numerical weather prediction community. Following the successful FORMOSAT-3/COSMIC mission, the FORMOSAT-7/COSMIC-2 constellation, consisting of also six radio occultation satellites, was launched on 25 June 2019. As a collaborator of the mission, we prepared early to investigate the anticipated impact of the FORMOSAT-7/COSMIC-2 data on weather prediction as soon as the preliminary data were available. Statistically significant improvement in global forecast skills is clearly shown, with the most significant impact found in the tropics, consistent with the primary goal of the mission. The real-time tropospheric and stratospheric FORMOSAT-7/COSMIC-2 radio occultation data have been officially released since March 2020, available for use in operational weather prediction worldwide. [ABSTRACT FROM AUTHOR]

Inversion of radio occultation (RO) measurements to atmospheric parameters in the neutral atmosphere utilizes the assumption of spherical symmetry by implementation of the Abel transform. The main contribution to the retrieved refractional angle and other geophysical parameters comes from gaseous properties of the atmosphere. The atmospheric refraction is expressed by a function of air pressure, air temperature, and water vapor pressure. Such commonly adopted methodology results in highly comparable RO retrievals with background models. However, in the lowermost troposphere referred to as planetary boundary layer, inversion in spherically symmetric atmosphere is an ill‐conditioned problem. The presence of superrefractions introduces negative errors in the RO‐retrieved refractivity (N‐bias). We show that significant refractivity gradients are frequently collocated with clouds over oceans in tropical and subtropical regions. Based on gridded monthly means we show that superrefractions usually occur at altitudes up to 2 km and the largest cloud fractions tend to suspend at underlying layers. The magnitude of clouds expressed in terms of refractivity units can exceed 1.5, which corresponds to 0.5% in terms of fractional differences. We use both geometrical optics and wave optics techniques to illustrate propagation mechanisms in RO retrievals. Simulation experiments suggest that RO inversions in cloudy planetary boundary layer lead to larger negative N‐biases. Low‐level clouds retrieved from numerical weather prediction model could therefore be used as an indicator of erroneous RO observations. A better agreement with RO refractivity could be achieved by incorporating cloud variables into background fields especially over the Pacific and Atlantic Oceans.

İmâmiyye, nass ve tayin merkezli bir imamet nazariyesi inşa etmekte ve imamın dinî ve dünyevî bütün yetkileri kendisinde toplayan kişi olduğunu kabul etmektedir. İmâmın yetkileri arasında ḥadleri uygulamak, zekât ve ḫumusu toplamak, adaleti sağlamak ve cihad ilan etmek gibi dinî, sosyal ve siyasî görevler bulunmaktadır. İmâma ait bu görevlerin yerine getirilebilmesi için bizzat imamın veya nâibinin işin başında olması gerekir. İmâmla irtibatın tamamen kesildiği gaybet-i kübrâ’nın (329/941---) başlamasıyla İmâmiyye taraftarları, imamın varlığıyla irtibatlandırılan bu görev ve yetkilerin yerine getirilip getirilemeyeceği meselesinde bir belirsizlik yaşamışlardır. Şiî ulemâ, bu kargaşa ortamında oluşan boşluğu doldurmak ve toplum içerisindeki muhtemel dağılmaları önlemek amacıyla faaliyet alanlarını genişleterek imamın görevlerini üstlenmeye başlamışlardır. Başlangıç itibariyle dinî alanla sınırlı olan bu yetki devrinin kapsamı, süreç içerisinde tedrîcen genişletilmiştir. Uzun bir zamanı kapsayan bu yetki devrinin belirli dönemler halinde ele alınması gerekir. Bu çalışmada konu, hicrî beşinci asırda yaşayan âlimler ekseninde ele alınmaktadır. Makalede Şeyḫ Müfîd sonrası dönemde Uṣûlî düşüncenin sistemleşmesinde pay sahibi olan âlimlerin, fakîhin otoritesinin genişletilmesi veya daraltılması problemi bağlamında imamın yetkileri dâhilindeki konuları nasıl ele aldığı ortaya konulmaktadır. Özet: Hz. Peygamber’den sonra Müslümanların siyaseten farklılaşmalarına yol açan imâmet/ḫilafet meselesinde İmâmiyye, nass ve tayini esas alan bir imâmet nazariyesi inşa etmektedir. Bu nazariye’ye göre nass ve tayin dışında ismet, ilim, şecaat, efdâliyet gibi şahsî niteliklerin bulunması gereken imamlar, Hz. Ali, Hasan, Hüseyin ve Hüseyin’in neslinden gelen dokuz kişidir. Hz. Peygamber’den sonra onun yerine geçen imam, dinî ve siyasî bütün yetkilerin kendisinde toplanan kişidir. İmâmın görevleri arasında ḥadleri uygulamak, zekât ve ḫumusu toplamak, adaleti sağlamak ve cihad ilan etmek gibi görevler bulunmaktadır. İmâmiyye’ye göre bu görev ve yetkilerin yerine getirilebilmesi için toplum üzerinde mutlak otorite sahibi imâmın veya onun tarafından atanan kişinin bizzat işin başında olması gerekir. On ikinci imâmın gâib olduğunu ve bir gün dönerek yeryüzünde adaleti yeniden tesis edeceğini kabul eden İmâmiyye taraftarları, gaybet döneminde itikâdi meseleler yanı sıra bizzat imâmın varlığı ile irtibatlandırılan konuların çözümünde çeşitli sorunlarla yüzleşmek zorunda kaldılar. Özellikle de imâmla irtibatın tamamen kesildiği gaybet-i kübrâ (329/941---) döneminde İmâmiyye mensupları, imâmın varlığıyla irtibatlandırılan görevlerin yerine getirilmesinde bir belirsizlik yaşadı. Mezhep mensuplarının belirsizlik ve kaos yaşamalarındaki muhtemel sebep, gaybet döneminde imâma ait görev ve yetkilerin nasıl yerine getirileceğine dair bir haberin olmamasıdır. Her ne kadar ḫumus özelinde ifade etmiş olsa da Şeyḫ Müfîd bu hususa dikkat çekmektedir. Şiî ulemâ, bu belirsizlik ortamında oluşan boşluğu doldurmak ve toplum içerisindeki muhtemel dağılmaları önlemek amacıyla ön plana çıkmışlardır. Onlar, on ikinci imâmdan gelen bir tevḳi‘ye atıfta bulunarak toplum üzerindeki etkinlik alanlarını genişletmişler ve imâmın yokluğunda ona ait görevlerin kendileri tarafından yerine getirilebileceğini iddia etmektedirler. Başlangıç itibariyle dinî alanla sınırlı olan bu yetki devrinin kapsamı, bazı âlimlerim katkılarıyla tedrîcen genişletildi. “Velâyet-i fakîh” teorisinin uygulanmasıyla da en geniş boyuta ulaştı. Günümüze kadar devam eden bu uzun zaman diliminde Şerîf el-Murtażâ ve öğrencilerin yaşadığı dönem, günümüze kadar devam eden bu sürecin başlangıç dönemi olarak nitelendirilmesi mümkündür. Şerîf el-Murtażâ ve öğrencilerinin yaşadığı hicrî beşinci asırda, imâma ait yetkilerin ulemâ tarafından üstlenilmesi daha çok dinî alanla sınırlıdır. Bu makalede Şeyḫ Müfîd sonrası dönemde Uṣûlî düşüncenin sistemleşmesinde pay sahibi olan âlimlerin imâmın yetkileri arasındaki konuları nasıl ele aldıkları ve ne ölçüde İmâmî fakîhe referans gösterdikleri ortaya konulmaktadır. İmâma ait yetkilerin kullanımında Şerîf el-Murtażâ ve öğrencileri, bazen ihtiyatlı ve temkinli bir tavır sergilemişlerdir. Bununla birlikte onlar, gaybet döneminde ortaya çıkan belirsizliğin ortadan kaldırılmasında fakîhin rolüne işaret etmektedirler. Nitekim gaybet döneminde imâmın yetkileri arasındaki ḫumusun toplanıp dağıtılmasında Şeyḫ Ṭûsî ve Ḳâḍî İbnü’l-Berrâc, önemli katkılar sunmuşlardır. Ancak daha da önemli bir adım, Sellâr ed-Deylemî tarafından atılmıştır. O, gaybet döneminde ḫumusu bir lütuf olarak kabul etmekte ve imâmın paylarını da kapsayacak şekilde onun kullanımına müsaade etmektedir. Zekât konusunda ise onlar, daha açık ifadelerle fakîhin konumuna işaret eden görüşler ileri sürmektedirler. Hatta İbnü’l-Berrâc, imâm ve nâibinin olmadığında verilecek yerleri daha iyi bildikleri gerekçesiyle zekâtı fakîhlere vermenin vâcib olduğunu iddia etmektedir. Dolayısıyla onlar, imâmın ve nâibinin olmadığı veya ona ulaşma imkânın bulunmadığı durumlarda, zekâtın toplanıp dağıtılmasında fakîhi adres göstererek daha erken bir dönemde bir çözüm üretmişlerdir. İmâmın toplum üzerindeki en etkin görevlerinden birisi olan Cuma namazı meselesinde ise Şerîf el-Murtażâ ve öğrencileri, imâmın veya onun tayin ettiği kişinin bulunmasını cumanın sıhhat şartları arasında saymışlardır. el-Ḥalebî bu şarta ilave olarak gerekli şartları taşıyan bir kişinin olmasını da cumanın sıhhat şartı olduğunu kabul etmektedir. el-Ḥalebî’nin bu açılımı, hem gaybet döneminde Cuma namazı ile ilgili karşılaşılan problemin çözümüne hem de imâmın dinî ve siyasî yetkisinin fakîh tarafından devralınmasına önemli bir katkıdır. Bununla birlikte Şerîf el-Murtażâ’nın bir diğer öğrencisi Sellâr, gerekli şartlar oluştuğunda fakîhin Cuma namazını kıldırabileceği görüşüne karşı çıkmaktadır. Sellar’ın bu yaklaşımı mezhep içerisinde gaybet döneminde Cuma namazı kılmanın haram olduğu şeklindeki görüşlere zemin hazırladığı söylenebilir. Gaybet döneminde ḥadlerin uygulanması konusunda ise Şerîf el-Murtażâ ve öğrencileri, genel olarak ihtiyatlı bir tutum sergilemektedirler. Onlar, insanlara ḥad cezalarının uygulanabilmesi için imâmın mevcut olması gerektiğini ileri sürmektedirler. Bununla birlikte gaybet döneminde ḥadlerin uygulanmasıyla ilgili belirsizliğin ortadan kaldırılmasına yönelik en önemli adım, Şeyh Tûsî tarafından atılmıştır. O, imâmların Şiî fakîhlerine cezâ hukukunu uygulamaya izin verdiklerini söylemektedir. Bu konuya ilave olarak Şiî ulemânın tartıştığı bir diğer konu da gaybet döneminde mevcut yönetimlerde görev almak zorunda kalan bir kişinin bu cezaları uygulayıp uygulayamayacağıdır. Şerîf el-Murtażâ, bu problemin çözümüne yönelik Mes’ele fi’l-‘amel me‘a’s-sulṭân başlıklı bir risâle kaleme almıştır. O, mevcut yönetimlerde görev üstlenmenin niteliğini, kişinin icra edeceği fiil ve üstlendiği sorumluluğu yerine getirip getiremeyeceğine göre sınıflandırmıştır. Şerîf el-Murtażâ’nın öğrencileri de mevcut siyasî otoritelerde görev alma konusunda hocalarının uzlaşmacı tutumunu devam ettirmişlerdir. Son tahlilde imâma ait görevlerin nasıl ve kimler tarafından yerine getirileceği probleminin çözümünde Şerîf el-Murtażâ ve öğrencilerinin katkıları, daha sonraki dönemlerde fakîhin otoritesinin pekişmesine ve nihâi olarak bir fakîhin imâmın siyasî yetkilerini de kullanabilecek konuma gelmesine zemin hazırlamıştır. Hatta Şerîf el-Murtażâ’nın mevcut yönetimlerde görev üstlenme konusundaki açılımı, daha sonraki dönemlerde otoritelerle ilişki kurmak isteyen ulemâ için bir çıkış yolu olmuştur.

Stale seedbeds are commonly used by organic vegetable farmers to reduce in-season weed density. The primary purpose of this study was to evaluate the efficacy of soil solarization (clear plastic) with subsequent flaming for stale seedbed preparation. A secondary objective was to compare the efficacy of solarization with tarping (black plastic). Solarization is an established weed management practice in warmer climates, but its efficacy in the humid continental Northeast USA was unknown. We hypothesized that solarization during May-June in Maine, USA would increase weed emergence, and could thereby contribute to depletion of the germinable weed seedbank and, with subsequent flaming, creation of an improved stale seedbed. We expected that firming soil with a roller prior to solarization would further increase weed emergence. Across four site-years of replicated field experiments and two on-farm trials we found that, contrary to expectations, 2 weeks of solarization reduced apparent weed emergence (density) in comparison to nonsolarized controls by 83% during treatment, and 78% after 2 weeks of observation following plastic removal and flaming. Rolling did not significantly affect weed density. Soil temperatures were elevated in solarized plots, reaching a maximum of 47◦ C at 5 cm soil depth, compared to 38◦ C in controls. Weed community analyses suggested that solarization might act as an ecological filter limiting some species. Addressing our secondary objective, two replicated field experiments compared the efficacy of solarization with tarping applied for periods of 2, 4, and 6 weeks beginning in July. Across treatment durations, solarization was more effective than tarping in one site-year, but tarping outperformed solarization in the other; this discrepancy may be explained by differences in weed species and soil temperatures between experiments. Overall, solarization and tarping are promising stale seedbed preparation methods for humid continental climates, but more work is needed to compare their relative efficacy.

Bayesian interpolation has previously been proposed as a strategy to construct maps of radio occultation (RO) data, but that proposition did not consider the diurnal dimension of RO data. In this work, the basis functions of Bayesian interpolation are extended into the domain of the diurnal cycle, thus enabling monthly mapping of radio occultation data in synoptic time and analysis of the atmospheric tides. The basis functions are spherical harmonics multiplied by sinusoids in the diurnal cycle up to arbitrary spherical harmonic degree and diurnal cycle harmonic. Bayesian interpolation requires a regularizer to impose smoothness on the fits it produces, thereby preventing the overfitting of data. In this work, a formulation for the regularizer is proposed and the most probable values of the parameters of the regularizer determined. Special care is required when obvious gaps in the sampling of the diurnal cycle are known to occur in order to prevent the false detection of statistically significant high-degree harmonics of the diurnal cycle in the atmosphere. Finally, this work probes the ability of Bayesian interpolation to generate a valid uncertainty analysis of the fit. The postfit residuals of Bayesian interpolation are dominated not by measurement noise but by unresolved variability in the atmosphere, which is statistically nonuniform across the globe, thus violating the central assumption of Bayesian interpolation. The problem is ameliorated by constructing maps of RO data using Bayesian interpolation that partially resolve the temporal variability of the atmosphere, constructing maps for approximately every 3 days of RO data. [ABSTRACT FROM AUTHOR]

Global positioning system (GPS) radio occultation (RO) observations, first made of Earth's atmosphere in 1995, have contributed in new ways to the understanding of the thermal structure and variability of the tropical upper troposphere–lower stratosphere (UTLS), an important component of the climate system. The UTLS plays an essential role in the global radiative balance, the exchange of water vapor, ozone, and other chemical constituents between the troposphere and stratosphere, and the transfer of energy from the troposphere to the stratosphere. With their high accuracy, precision, vertical resolution, and global coverage, RO observations are uniquely suited for studying the UTLS and a broad range of equatorial waves, including gravity waves, Kelvin waves, Rossby and mixed Rossby–gravity waves, and thermal tides. Because RO measurements are nearly unaffected by clouds, they also resolve the upper-level thermal structure of deep convection and tropical cyclones as well as volcanic clouds. Their low biases and stability from mission to mission make RO observations powerful tools for studying climate variability and trends, including the annual cycle and intraseasonal-to-interannual atmospheric modes of variability such as the quasi-biennial oscillation (QBO), Madden–Julian oscillation (MJO), and El Niño–Southern Oscillation (ENSO). These properties also make them useful for evaluating climate models and detection of small trends in the UTLS temperature, key indicators of climate change. This paper reviews the contributions of RO observations to the understanding of the three-dimensional structure of tropical UTLS phenomena and their variability over time scales ranging from hours to decades and longer. [ABSTRACT FROM AUTHOR]

The sampling error caused by the uneven distribution of radio occultation (RO) profiles in both space and time domains is an important error source of RO climatologies. In this paper, the sampling error RO temperature climatologies is investigated using the 4-yr (2007-10) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate mission. The error is divided into three parts, including local time component (LTC), temporal component (TC), and spatial component (SC). The characteristics of the three components are investigated. Results show the following: 1) The LTC part of the total sampling error is characterized by a pattern of periodic positive and negative deviations, with a full cycle of about four months. The most significant LTC values are found in the area around 608N/S and the polar regions. 2) The TC part is mainly associated with the extent of day-to-day temperature variability and the daily number of RO profiles observed in each month. The most pronounced TC part is shown in high-latitude areas in wintertime, where the day-to-day temperature variability is high. 3) The SC part shows distinct features in different altitude ranges. It is characterized by a systemic error in the lower troposphere (2-8 km) but exhibits a seasonal trend at the altitude range from 8 to 40 km. 4) The total sampling error is dominated by the TC and SC parts in the troposphere and lower stratosphere, whereas in the upper stratosphere it is dominated by the LTC part. [ABSTRACT FROM AUTHOR]

The Earth occultation technique has broad applications in both astronomy and atmospheric density measurements. We construct the background model during the occultation of the Crab Nebula observed by the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) at energies between 6 and 100 keV. We propose a Bayesian atmospheric density retrieval method based on the Earth occultation technique, combining Poisson and Gaussian statistics. By modeling the atmospheric attenuation of X-ray photons during the occultation, we simultaneously retrieved the neutral densities of the atmosphere at different altitude ranges. Our method considers the correlation of densities between neighboring atmospheric layers and reduces the potential systematic bias to which previous work may be subject. Previous analyses based on light-curve fitting or spectral fitting also lost some spectral or temporal information of the data. In contrast to previous work, the occultation data observed by the three telescopes on board Insight-HXMT is fully used in our analysis, further reducing the statistical error in density retrieval. We apply our method to cross-check the (semi)empirical atmospheric models, using 115 sets of occultation data of the Crab Nebula observed by Insight-HXMT. We find that the retrieved neutral density is ∼10%, ∼20%, and ∼25% less than the values of the widely used atmospheric model NRLMSISE-00, in the altitude range of 55–80 km, 80–90 km, and 90–100 km, respectively. We also show that the newly released atmospheric model NRLMSIS 2.0 is generally consistent with our density measurements.

Long-term stability, global coverage and high resolution are characteristics that make the Global Navigation Satellite System (GNSS) radio occultation (RO) technique well-suitable to serve as anchor measurements for observing the Earth’s atmosphere. The concept of occultation soundings utilizes a receiver placed on a low Earth orbit to measure the accumulated atmospheric contribution along the limb in terms of a phase delay. A high sampling rate allows to reconstruct profiles of geophysical parameters through an inversion process of occultation signals. However, such measurements require a careful processing in order to provide accurate retrievals in the neutral atmosphere. The following development describes specific aspects in radio occultation methodology implemented in the retrieval chain from phase data to profiles of dry pressure and dry temperature. Independent retrievals from nearreal time measurements are compared with occultation products provided by official processing centers to demonstrate reliability of the solution. The region within the upper troposphere and lower stratosphere (UTLS) is particularly represented by a low uncertainty being within 0.5% (K). A comparison with radiosondes shows a significant contribution of a water vapor term in the lower troposphere that comes from the dry air assumption in occultation profiles of pressure and temperature. Radiosonde measurements reproduced to refractivity profiles show very high agreement with occultation soundings, which is generally below 5%. A superior accuracy of RO refractivity is observed in the upper troposphere, where retrievals are consistent with radiosondes to 1%.

Inversion of radio occultation (RO) measurements to atmospheric parameters in the neutral atmosphere utilizes the assumption of spherical symmetry by implementation of the Abel transform. The main contribution to the retrieved refractional angle and other geophysical parameters comes from gaseous properties of the atmosphere. The atmospheric refraction is expressed by a function of air pressure, air temperature, and water vapor pressure. Such commonly adopted methodology results in highly comparable RO retrievals with background models. However, in the lowermost troposphere referred to as planetary boundary layer, inversion in spherically symmetric atmosphere is an ill‐conditioned problem. The presence of superrefractions introduces negative errors in the RO‐retrieved refractivity (N‐bias). We show that significant refractivity gradients are frequently collocated with clouds over oceans in tropical and subtropical regions. Based on gridded monthly means we show that superrefractions usually occur at altitudes up to 2 km and the largest cloud fractions tend to suspend at underlying layers. The magnitude of clouds expressed in terms of refractivity units can exceed 1.5, which corresponds to 0.5% in terms of fractional differences. We use both geometrical optics and wave optics techniques to illustrate propagation mechanisms in RO retrievals. Simulation experiments suggest that RO inversions in cloudy planetary boundary layer lead to larger negative N‐biases. Low‐level clouds retrieved from numerical weather prediction model could therefore be used as an indicator of erroneous RO observations. A better agreement with RO refractivity could be achieved by incorporating cloud variables into background fields especially over the Pacific and Atlantic Oceans. Key Points: Superrefractions show geographical and temporal relationship to cloud liquid water in PBLOccultations measured under superrefraction conditions can be affected by clouds to a nonnegligible order (1.5 N‐units or 0.5%)Statistics of systematic errors in RO observations indicate particularly active oceanic regions [ABSTRACT FROM AUTHOR]

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Long-term stability, global coverage and high resolution are characteristics that make the Global Navigation Satellite System (GNSS) radio occultation (RO) technique well-suitable to serve as anchor measurements for observing the Earth's atmosphere. The concept of occultation soundings utilizes a receiver placed on a low Earth orbit to measure the accumulated atmospheric contribution along the limb in terms of a phase delay. A high sampling rate allows to reconstruct profiles of geophysical parameters through an inversion process of occultation signals. However, such measurements require a careful processing in order to provide accurate retrievals in the neutral atmosphere. The following development describes specific aspects in radio occultation methodology implemented in the retrieval chain from phase data to profiles of dry pressure and dry temperature. Independent retrievals from nearreal time measurements are compared with occultation products provided by official processing centers to demonstrate reliability of the solution. The region within the upper troposphere and lower stratosphere (UTLS) is particularly represented by a low uncertainty being within 0.5% (K). A comparison with radiosondes shows a significant contribution of a water vapor term in the lower troposphere that comes from the dry air assumption in occultation profiles of pressure and temperature. Radiosonde measurements reproduced to refractivity profiles show very high agreement with occultation soundings, which is generally below 5%. A superior accuracy of RO refractivity is observed in the upper troposphere, where retrievals are consistent with radiosondes to 1%. [ABSTRACT FROM AUTHOR]

Global positioning system (GPS) radio occultation (RO) is capable of retrieving vertical profiles of atmospheric parameters with high resolution (<100 m), which can be achieved in spherically symmetric atmosphere. Horizontal inhomogeneity of real atmosphere results in representativeness errors of retrieved profiles. In most cases these errors increase with a decrease of vertical scales of atmospheric structures and may not allow one to fully utilize the physical resolution of RO. Also, GPS RO–retrieved profiles are affected by observational noise of different types, which, in turn, affect the representation of small-scale atmospheric structures. This study investigates the effective resolution and optimal smoothing of GPS RO–retrieved temperature profiles using high-pass filtering and cross correlation with collocated high-resolution radiosondes. The effective resolution is a trade-off between representation of real atmospheric structures and suppression of observational noise, which varies for different latitudes (15°S–75°N) and altitudes (10–27 km). Our results indicate that at low latitudes the effective vertical resolution is about 0.2 km near the tropical tropopause layer and about 0.5 km in the lower stratosphere. The best resolution of 0.1 km is at the cold-point tropical tropopause. The effective resolutions at the midlatitudes are slightly worse than at low latitudes, varying from ~0.2 to 0.6 km. At high latitudes, the effective resolutions change notably with altitude from ~0.2 km at 10–15 km to ~1.4 km at 22–27 km. Our results suggest that the atmospheric inhomogeneity plays an important role in the representation of the vertical atmospheric structures by RO measurements. [ABSTRACT FROM AUTHOR]

Assimilation of radio occultation (RO) observations into numerical weather prediction (NWP) models has improved forecasts, where RO is typically one of the top five observational systems contributing to forecast accuracy. By measuring the phase delay of radio waves traversing Earth's atmosphere between global positioning system (GPS) and low-Earth orbiting satellites, RO obtains quasi-vertical profiles of bending angles (BA) of the radio waves' trajectories. BA are the RO observation most often assimilated into NWP models, but since they are not computed or analyzed in the models, they must be computed from model data using a forward model. First, model refractivity N is computed from variables specified on the model's vertical levels, then using the Abel integral, BA are computed from N. The forward model requires vertical differentiation of N, and accurate differentiation requires vertical interpolation of N between model levels. The interpolation results in errors, which then propagate through the forward model to produce BA errors. In this study, we investigate the sensitivity of forward-modeled BA to five different methods of vertical interpolation of N between model levels to determine a method that minimizes interpolation errors. We use RO-observed N to isolate the interpolation errors and determine an accurate method that can be applied to any NWP model. Of the five methods investigated, the log-spline interpolation reduces N and BA errors the most, regardless of the vertical resolution of the model grid. [ABSTRACT FROM AUTHOR]

Experiments with a global observing system simulation experiment (OSSE) system based on the recent 7-km-resolution NASA nature run (G5NR) were conducted to determine the potential value of proposed Global Navigation Satellite System (GNSS) radio occultation (RO) constellations in current operational numerical weather prediction systems. The RO observations were simulated with the geographic sampling expected from the original planned Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) system, with six equatorial (total of ~6000 soundings per day) and six polar (total of ~6000 soundings per day) receiver satellites. The experiments also accounted for the expected improved vertical coverage provided by the Jet Propulsion Laboratory RO receivers on board COSMIC-2. Except that RO observations were simulated and assimilated as refractivities, the 2015 version of the NCEP's operational data assimilation system was used to run the OSSEs. The OSSEs quantified the impact of RO observations on global weather analyses and forecasts and the impact of adding explicit errors to the simulation of perfect RO profiles. The inclusion or exclusion of explicit errors had small, statistically insignificant impacts on results. The impact of RO observations was found to increase the length of the useful forecasts. In experiments with explicit errors, these increases were found to be 0.6 h in the Northern Hemisphere extratropics (a 0.4% improvement), 5.9 h in the Southern Hemisphere extratropics (a significant 4.0% improvement), and 12.1 h in the tropics (a very substantial 28.4% improvement). [ABSTRACT FROM AUTHOR]

L’auteure appréhende la communication gouvernementale canadienne à la lumière des apports théoriques de Jacques Ellul sur les mythes modernes du 20e siècle et sur la propagande. Il ressort de l’analyse des propos des sujets parlants et des images de 26 vidéos diffusées sur le site Internet de l’armée canadienne, destinées au recrutement de jeunes de 18 à 34 ans (2010), une typologie de mythes fondateurs (Science, Histoire, Progrès) et de mythes secondaires connexes (progrès technique, technicien performant, formation et carrière idéales, réalisation du bonheur matériel, fratrie, valeurs supérieures, héros exemplaire, vie rêvée, jeunesse promise à des lendemains qui chantent). Ces mythes supportent l’idée que le métier des armes est un métier comme un autre tout en occultant sa finalité guerrière et létale. Constitutifs de communications publicitaires largement financées et diffusées par le gouvernement conservateur de Steven Harper, via le ministère de la Défense nationale, en poussant les jeunes Canadiens à s’engager dans l’armée, ces mythes qui assurent l’efficacité orthopraxique de ces communications, apparentent ces dernières à de la propagande.