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In the present study, the tropical tropopause inversion layer (TIL) Kelvin waves are extracted from the Global Navigation Satellite System (GNSS) radio occultation (RO) temperature data of multiple missions from January 2007 to December 2020. We focus on the variations of TIL Kelvin waves in two longitude regions, the Maritime Continent (MC; 90°–150°E) and the Pacific Ocean (PO; 170°–230°E). The results show that over both regions, ENSO leads to the opposite variations of TIL Kelvin wave temperature amplitude during different ENSO phases. Specifically, during La Niña, the strong (weak) deep convection over MC (PO) leads to strengthened (weakened) static stability. With enhanced easterly (westerly) winds and strengthened (weakened) static stability, the TIL Kelvin wave temperature amplitudes are stronger (weaker) over MC (PO). The opposite phenomenon occurs during El Niño. The zonal-mean zonal winds affect TIL Kelvin wave temperature amplitudes by two mechanisms. First, the prevalence of easterlies (westerlies) in the upper troposphere affects the upward propagation of Kelvin waves, resulting in stronger (weaker) TIL Kelvin wave temperature amplitudes over MC (PO). Second, the TIL Kelvin wave temperature amplitude peaks about 2 months before the zero-wind line of the descending westerly QBO phase occurs, due to dissipation on the critical line. Additionally, the rapid increase of zonal-mean static stability significantly affects the annual variation of TIL Kelvin wave temperature amplitudes. They both reach maxima during DJF and minima during JJA, which should be related to the annual cycles of temperature and ozone mixing ratio in the TIL. Significance Statement: Recent studies indicate that the Kelvin wave temperature amplitudes in the tropical tropopause inversion layer (TIL) exhibit distinct characteristics compared with those in other height levels, while the modulation mechanisms of the TIL Kelvin waves need further investigation. The present study aims to study the differences in the variabilities and the modulation factors of TIL Kelvin waves over two longitude regions. Our findings suggest that the different responses of background conditions during ENSO phases influence the spatiotemporal distribution of the TIL Kelvin waves. Besides, the zonal winds and the static stability significantly affect the temporal variations of TIL Kelvin waves. Our work fills the research gap of TIL Kelvin waves and contributes to understanding the dynamics of tropical tropopause variations. [ABSTRACT FROM AUTHOR]

Motivated by efforts to return humanity to the Moon, three cases are reviewed for X-ray astronomy from the lunar surface: (i) facilitation of ambitious engineering designs including high-throughput telescopes, long focal length optics and X-ray interferometery; (ii) occultation studies and the gain they enable in astrometric precision; and (iii) multi-messenger time-domain coordinated observations. The potential benefits of, and challenges presented by, operating from the Moon are discussed. Some of these cases have relatively low mass budgets and could be conducted as early pathfinders, while others are more ambitious and will likely need to await improvements in technology or well-developed lunar bases. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'. [ABSTRACT FROM AUTHOR]

The concept of the expected saviour exists as a phenomenon in various religions and cultures, albeit with some differences. In the Shīʿite sect that emerged in Islamic history after the death of ʿAlī b. Abī Ṭālib (d. 40/661), ʿAlī and his descendants were referred to as imams based on the imamate doctrine. Members of the sect, who had difficulty accepting the death of the imams to whom they attributed political and sometimes spiritual leadership, believed that the imam they followed would return to the world and bring justice to the oppressed earth. In the Imāmiyya Shīʿa (Twelvers), one of the main branches of the sect that has survived to the present day, the doctrine of the Imamate is one of the basic tenets of the faith, and the line of the imamate ends with the twelfth imam, Muhammad b. al-Hasan. With the twelfth imam went into occultation in 260/874, the belief that he would one day come and rule the oppressed world with justice under the title of al-mahdī (the guided one) and al-muntaẓar (the expected one) has become an important tenet in Imāmiyya. This study deals chronologically with the claims of mahdism that emerged from within Shiʿism during the so-called occultation period. Especially in Iran and its surroundings, where Imāmiyya Shīʿites live densely, some messianic movements have emerged around people who declared themselves or were declared as the expected saviour. In this article, the movements that emerged around the idea of messiahship such as Ḥurūfism, Musha'sha'a, Ṣafavism, Bābism and Bahā'īsm are discussed. [ABSTRACT FROM AUTHOR]

Superrefraction at the top of the atmospheric boundary layer introduces problems for assimilation of radio occultation data in weather models. A method of detection of superrefraction by spectral analysis of deep radio occultation signals introduced earlier has been tested using 2 years of COSMIC-2/FORMOSAT-7 radio occultation data. Our analysis shows a significant dependence of the probability of detection of superrefraction on the signal-to-noise ratio, which results in a certain sampling nonuniformity. Despite this nonuniformity, the results are consistent with the known global distribution of superrefraction (mainly over the subtropical oceans) and show some additional features and seasonal variations. Comparisons to the European Centre for Medium-Range Weather Forecasts analyses and limited set of radiosondes show reasonable agreement. Being an independent measurement, detection of superrefraction from deep radio occultation signals is complementary to its prediction by atmospheric models and thus should be useful for assimilation of radio occultation data in the atmospheric boundary layer. [ABSTRACT FROM AUTHOR]

Estimation of uncertainties (random error statistics) of radio occultation (RO) observations is important for their effective assimilation in numerical weather prediction (NWP) models. Average uncertainties can be estimated for large samples of RO observations and these statistics may be used for specifying the observation errors in NWP data assimilation. However, the uncertainties of individual RO observations vary, and so using average uncertainty estimates will overestimate the uncertainties of some observations and underestimate those of others, reducing their overall effectiveness in the assimilation. Several parameters associated with RO observations or their atmospheric environments have been proposed to estimate individual RO errors. These include the standard deviation of bending angle (BA) departures from either climatology in the upper stratosphere and lower mesosphere (STDV) or the sample mean between 40 and 60 km (STD4060), the local spectral width (LSW), and the magnitude of the horizontal gradient of refractivity (|∇HN|). In this paper we show how the uncertainties of two RO datasets, COSMIC-2 and Spire BA, as well as their combination, vary with these parameters. We find that the uncertainties are highly correlated with STDV and STD4060 in the stratosphere, and with LSW and |∇HN| in the lower troposphere. These results suggest a hybrid error model for individual BA observations that uses an average statistical model of RO errors modified by STDV or STD4060 above 30 km, and LSW or |∇HN| below 8 km. Significance Statement: These results contribute to the understanding of the sources of uncertainties in radio occultation observations. They could be used to improve the effectiveness of these observations in their assimilation into numerical weather prediction and reanalysis models by improving the estimation of their observational errors. [ABSTRACT FROM AUTHOR]

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]

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.

In Indian classical astronomy, the Siddhāntic texts discuss in detail conjunctions of the Sun, the Moon, the planets and important stars like Rohiṇī (Aldebaran), Tiṣya or Puṣya (δ Cancri), Citrā (Spica), Jyeṣṭhā (Antares), Makhā (Regulus) etc. The star Rohiṇῑ is given prominence, and in this paper we discuss the circumstances required for an occultation of Rohiṇῑ to occur, historical examples of such occultations and the periodicity of Rohiṇῑ occultations. [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]

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.

The local spectral width (LSW) of a radio occultation (RO) observation in impact parameter representation is a useful parameter for providing information on the uncertainty associated with the RO bending angle measurement. The LSW can potentially be used to specify the bending angle observation error (BaOE) in the lower troposphere for each individual sounding. This study assesses the usefulness and limitations of LSW in representing BaOE for a global data assimilation system. A two-step scheme is proposed to derive profile-dependent BaOE from LSW. Since the LSW-based BaOE varies with each individual RO observation, it is here designated as a dynamic BaOE (DBOE) in contrast to the traditional statistics-based BaOE specification. A benchmark control run and two sensitivity experiments are conducted with continuous cycling data assimilation using the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) and Global Forecast System (GFS). The usefulness and impact of the LSW-based DBOE are evaluated using radiosonde observations and global analyses. Results show that DBOE is able to improve the assimilation of RO data, leading to better forecast skill scores. Another experiment, in which the GSI statistical observation error of the benchmark run is replaced by the average of LSW-based DBOE, shows that the ability to assign larger weighting for high-quality observation and lower weighting for low-quality observation is the key factor for the success of the LSW-based DBOE. [ABSTRACT FROM AUTHOR]

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]

We present long‐term density trends of the Earth's upper atmosphere at altitudes between 71 and 116 km, based on atmospheric occultations of the Crab Nebula observed with X‐ray astronomy satellites, ASCA, RXTE, Suzaku, NuSTAR, and Hitomi. The combination of the five satellites provides a time period of 28 years from 1994 to 2022. To suppress seasonal and latitudinal variations, we concentrate on the data taken in autumn (49 < doy < 111) and spring (235 < doy < 297) in the northern hemisphere with latitudes of 0°–40°. With this constraint, local times are automatically limited either around noon or midnight. We obtain four sets (two seasons × two local times) of density trends at each altitude layer. We take into account variations due to a linear trend and the 11‐year solar cycle using linear regression techniques. Because we do not see significant differences among the four trends, we combine them to provide a single vertical profile of trend slopes. We find a negative density trend of roughly −5%/decade at every altitude. This is in reasonable agreement with inferences from settling rate of the upper atmosphere. In the 100–110‐km altitude, we found an exceptionally high density decline of about −12%/decade. This peak may be the first observational evidence for strong cooling due to water vapor and ozone near 110 km, which was first identified in a numerical simulation by Akmaev et al. (2006, https://doi.org/10.1016/j.jastp.2006.03.008). Further observations and numerical simulations with suitable input parameters are needed to establish this feature. Plain Language Summary: Numerical simulations have shown that, while an increase of greenhouse gases such as CO2 in the atmosphere causes heating of the troposphere (near surface), it causes cooling of the middle and upper atmosphere, which is the so‐called "greenhouse cooling." The greenhouse cooling should result in atmospheric contraction and consequently a temporal density decrease at a fixed height. However, observational evidence for the density decrease has been scarce in the mesosphere and lower thermosphere (MLT: 80–110 km), owing to difficulty in measuring the density in this region. Here, we present the first direct measurements of long‐term variations for combined N and O atom number density in the MLT, based on atmospheric occultations of the Crab Nebula observed with X‐ray astronomy satellites. The combination of five X‐ray astronomy satellites, ASCA, RXTE, Suzaku, NuSTAR, and Hitomi, allows us to explore density trends for a long period from 1994 to 2022. We take into account variations due to a temporal linear trend and the 11‐year solar cycle, using linear regression techniques. As a result, we find a negative density trend of roughly −5%/decade at every altitude, with a local minimum of −12%/decade near 105 km. This is in reasonable agreement with the state‐of‐the‐art numerical simulations. Key Points: Time series of combined O and N densities are measured in the MLT, based on atmospheric occultations of the Crab Nebula using X‐ray astronomy satellitesThe density is decreasing everywhere, with a local minimum of −12%/decade near 105 kmThe local minimum in density trends may be due to strong cooling by water vapor and ozone, as was first predicted by Akmaev et al. (2006, https://doi.org/10.1016/j.jastp.2006.03.008) [ABSTRACT FROM AUTHOR]

According to the most widely accepted view, Imāmism and Muʿtazilism were originally poles apart. Subsequently, proselytes physically transported Muʿtazilī theology to Imāmī circles where it was adopted by the Banū Nawbakht among others. The basic problem with this explanation is that intellectual developments remain disconnected from wider social and political realities, which obscures the illocutionary force of texts and distorts their significance. Therefore, the first part of this article examines the background to the Imāmī turn toward rationalism. To understand the assimilation of Muʿtazilism as a creative historical process, intellectual developments are placed in the context of three sociopolitical factors: the crisis of the Occultation, Buwayhid patronage, and the religious topography of Baghdad. The second part of the article compares two texts that represent the evolution of Imāmī theology in this period: Ibn Bābawayh's Iʿtiqādāt al-imāmiyya and al-Mufīd's Taṣḥīḥ iʿtiqādāt al-imāmiyya. When historicised properly, a detailed comparison of these creeds suggests a more nuanced understanding of the Imāmī turn toward rationalism. [ABSTRACT FROM AUTHOR]

Interannual variability of tropospheric moisture and temperature are key aspects of Earth's climate. In this study, monthly mean specific humidity (q) and temperature (T) variability is analyzed using 12 years of COSMIC-1 (C1) radio occultation retrievals between 60°N and 60°S, with a focus on the tropics. C1 retrievals are relatively independent of the a priori values for q and T within the lower/middle troposphere and upper troposphere/lower stratosphere, respectively. Tropical interannual variability is dominated by El Niño–Southern Oscillation (ENSO). Systematic increases and decreases in zonal mean q and T are observed during the 2009/10 and 2015/16 El Niño events and 2007/08 and 2010/11 La Niña events, respectively. ENSO patterns in q and T are isolated using linear regression, and anomaly magnitudes increase with altitude, reaching a maximum in the upper troposphere. Upper-tropospheric q anomalies expand from the tropics into the midlatitude lower stratosphere, and the T vertical structure is consistent with a moist adiabatic response. C1 results are compared with NCAR's Whole Atmosphere Community Climate Model (WACCM), forced by observed sea surface temperatures, to evaluate model behavior in an idealized setting. WACCM ENSO variations in q and T generally show consistent behavior with C1 with somewhat smaller magnitudes. Case studies are conducted for major ENSO events during the study period. The spatial variability of q is closely aligned with outgoing longwave radiation (OLR) anomalies. For example, midtropospheric q increases over 100% and OLR decreases over 50 W m−2 over the central Pacific during the 2015/16 El Niño, and substantial regional q and T anomalies are observed throughout the tropics and midlatitudes for each event. [ABSTRACT FROM AUTHOR]

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.

Random errors (uncertainties) in COSMIC radio occultation (RO) soundings, ERA-Interim (ERAi) reanalyses, and high-resolution radiosondes (RS) are estimated in the northeast Pacific Ocean during the MAGIC campaign in 2012 and 2013 using the three-cornered hat method. Estimated refractivity and bending angle errors peak at ∼2 km, and have a secondary peak at ∼15 km. They are related to vertical and horizontal gradients of temperature and water vapor and associated atmospheric variability at these two levels. MAGIC RS refractivity and bending angles obtained from forward models have the largest uncertainties, followed by COSMIC RO soundings. ERAi has the smallest uncertainties. The large RS uncertainties can be primarily attributed to representativeness errors (differences). Differences in space and time of the RO and model datasets from the RS observations, error correlations among datasets, and the small sample size are other possible reasons contributing to these differences of estimated error statistics. RO temperature and humidity are retrieved from refractivity using a one-dimensional variational (1D-Var) method from the COSMIC Data Analysis and Archive Center (CDAAC). The estimated errors for COSMIC temperature are comparable to those of the MAGIC RS except near 1 km, where they are much higher. The estimated errors for COSMIC specific humidity are similar to the MAGIC specific humidity errors below ∼5 km and much smaller above this level. Estimates of COSMIC random errors based on ERAi, JRA-55, and MERRA-2 reanalyses in the same region, as well as comparison with estimates from other studies, support the reliability of our estimates. [ABSTRACT FROM AUTHOR]

We compare two seemingly different methods of estimating random error statistics (uncertainties) of observations, the three-cornered hat (3CH) method and Desroziers method, and show several examples of estimated uncertainties of COSMIC-2 (C2) radio occultation (RO) observations. The two methods yield similar results, attesting to the validity of both. The small differences provide insight into the sensitivity of the methods to the assumptions and computational details. These estimates of RO error statistics differ considerably from several RO error models used by operational weather forecast centers, suggesting that the impact of RO observations on forecasts can be improved by adjusting the RO error models to agree more closely with the RO error statistics. Both methods show RO uncertainty estimates that vary with latitude. In the troposphere, uncertainties are higher in the tropics than in the subtropics and middle latitudes. In the upper stratosphere–lower mesosphere, we find the reverse, with tropical uncertainties slightly less than in the subtropics and higher latitudes. The uncertainty estimates from the two techniques also show similar variations between a 31-day period during Northern Hemisphere tropical cyclone season (16 August–15 September 2020) and a month near the vernal equinox (April 2021). Finally, we find a relationship between the vertical variation of the C2 estimated uncertainties and atmospheric variability, as measured by the standard deviation of the C2 sample. The convergence of the error estimates and the standard deviations above 40 km indicates a lessening impact of assimilating RO above this level. Significance Statement: Uncertainties of observations are of general interest and their knowledge is important for assimilation in numerical weather prediction models. This paper compares two methods of estimating these uncertainties and shows that they give nearly identical results under certain conditions. The estimation of the COSMIC-2 bending angle uncertainties and how they compare to the assumed bending angle error models in several operational weather centers suggests that there is an opportunity for obtaining improved impact of RO observations in numerical model forecasts. Finally, the relationship between the COSMIC-2 bending angle errors and atmospheric variability provides insight into the sources of RO observational uncertainties. [ABSTRACT FROM AUTHOR]

The transition to deep convection and associated precipitation is often studied in relationship to the associated column water vapor owing to the wide availability of these data from various ground or satellite-based products. Based on radiosonde and ground-based global navigation satellite system (GNSS) data examined at limited locations and model comparison studies, water vapor at different vertical levels is conjectured to have different relationships to convective intensity. Here, the relationship between precipitation and water vapor in different free-tropospheric layers is investigated using globally distributed GNSS radio occultation (RO) temperature and moisture profiles collocated with GPM IMERG precipitation across the tropical latitudes. A key feature of the RO measurement is its ability to directly sense in and near regions of heavy precipitation and clouds. Sharp pickups (i.e., sudden increases) of conditionally averaged precipitation as a function of water vapor in different tropospheric layers are noted for a variety of tropical ocean and land regions. The layer-integrated water vapor value at which this pickup occurs has a dependence on temperature that is more complex than constant RH, with larger subsaturation at warmer temperatures. These relationships of precipitation to its thermodynamic environment for different layers can provide a baseline for comparison with climate model simulations of the convective onset. Furthermore, vertical profiles before, during, and after convection are consistent with the hypothesis that the lower troposphere plays a causal role in the onset of convection, while the upper troposphere is moistened by detrainment from convection. [ABSTRACT FROM AUTHOR]

Representation of complex vertical structures observed in the troposphere can vary depending on data sources. The radio occultation (RO) technique offers great advantages for sensing the atmosphere down to its lowermost layers using high-resolution measurements collected by satellites on low-Earth orbit (LEO). The structures are generally smoother in vertical when reproduced from atmospheric models. We evaluate the quality of troposphere retrievals from the COSMIC-2 mission and demonstrate that systematic effects in fractional refractivity deviations with respect to European Centre for Medium-Range Weather Forecasts (ECMWF) background fields are spatially correlated with positive refractivity gradients characterized as subrefraction. The magnitude of refractivity biases observed mostly over the equatorial regions can exceed 1% within altitudes of 3–5 km. Respective zonal means reveal seasonal trends linked with the distribution of atmospheric inversion layers and signal-to-noise ratio values in RO data. The positive biases are vertically collocated with significant refractivity gradients in COSMIC-2 retrievals that are not reflected in the corresponding ECMWF profiles. The analysis of gradients based on COSMIC-2 data, further supported by radiosonde observations, suggests that most of subrefractions is identified in the middle troposphere at around 4 km. While the altitudes of maximum refractivity gradients from COSMIC-2 and ECMWF data are in fairly good agreement, the magnitude of ECMWF gradients is significantly smaller and rarely exceeds positive values. [ABSTRACT FROM AUTHOR]

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.

Solar occultation measurements by the SPICAM IR on Mars-Express have been used to study aerosol vertical distribution during the 2007 global dust storm (GDS) of Mars Year 28. Measurements in the near-IR spectral range from 1 to 1.7 μm provide information about aerosol optical properties, extinction coefficient, particle size and number density. The observations were performed at Ls = 254–302° of MY28 and latitudes from 65°S to 65°N. Within the SPICAM spectral range we could not distinguish between absorption due to dust or water ice. The particle size distribution and its parameters, the effective radius r eff and variance ν eff , are retrieved assuming either mineral dust or water ice refraction indices. Before the MY 28 GDS at Ls < 265° the aerosol was detected from 20 to 60 km with dust particle size ∼0.75 μm below 50 km and decreasing with altitude above. The detached layers, presumably consisting of water ice, were observed at ∼60 km in the Southern hemisphere and 45 km in the Northern and Southern hemispheres with opacity <0.02 and 0.01–0.15, respectively. The effective radius varied from 0.2 to 1.6 μm with number density from 0.4 to 50 cm−3. With the development of the GDS dust reached to 80 km and higher, while r eff tended to increase with altitude up to 0.9–1 μm at 70–75 km. The dust number density decreased from 2 to 4 cm−3 at 40 km to 0.1 cm−3 at 70–80 km. The dependence of the effective variance on altitude and season has been studied. Before the beginning GDS ν eff varied below 50–60 km from 0.2 to 0.4 in the Southern hemisphere to 0.4–0.6 in the Northern hemisphere. During the GDS, the wider distribution propagated higher, with ν eff ∼ 0.5 up to 70 km in the southern hemisphere. In high latitudes of both hemispheres at Ls = 268–275° optically thin water ice high altitude clouds were detected at 80–90 km with r eff < 0.5 μm and number density 10–100 cm−3. • Aerosol vertical distribution has been studies during the MY28 Global Dust Storm. • Before GDS the dust particles size was ∼0.75 μm below 50 km and decreases with altitude above. • H 2 O ice clouds observed before GDS at 40–65 km with effective radius 0.2–1.6 μm and number density of 0.4–50 cm−3. • During the storm dust reached 80 km with effective radius up to 1 μm at 70 km. • During the peak of GDS water ice clouds detected at 80–90 km with τ < 0.01 and radius < 0.5 μm. [ABSTRACT FROM AUTHOR]

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.

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.

Following the successful launch of the Spanish PAZ mission the proof of concept experiment "Radio Occultation and Heavy Precipitation with PAZ" (ROHP-PAZ) started operating in May 2018. The ROHP-PAZ observations demonstrated that precise measurements of the phase shift between horizontal and vertical polarizations from Global Navigation Satellite System (GNSS) L-band signals are sensitive to oriented hydrometeors along the ray paths. While this differential phase shift measurement as a function of time has proven very useful, the regular radio occultation (RO) intermediate products from different polarized channels, such as bending angle and phase retrievals on the domain of impact parameter, have never been exploited. In this research, we studied the characteristics of polarimetric phase and bending angle difference retrieved by the radio-holographic (RH) method to mitigate atmospheric multipath effect and to explore their use in data assimilation. To validate RH approach in polarimetric retrievals, we performed end-to-end simulations where the hydrometeors are modeled by the effective refractivity with different horizontal extents. The simulation results demonstrate that the strong precipitation (>15 mm h−1) with 40-km horizontal extent can be detected with the retrieved bending angle shift. The calibration process on the impact parameter domain has also been developed to extract the differential phase and bending angle shift from the actual polarimetric RO data. Statistics from the PAZ data shows that the mean retrieved RH polarimetric phase shift with various horizontal extent is approximately proportional to the tangent point location rain rate at a ratio of 0.02 rad (mm h−1)−1. [ABSTRACT FROM AUTHOR]

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).

The idea of occultation as one of the most important beliefs of the Shi'i-Imamiyyah sect, expresses the belief that Muhammad b. Hasan al-Mahdi al-Muntazar disappeared into a cellar after his father's death and will return to earth in a near-apocalyptic period. In the process that started with the making of this claim, there were various attempts to adopt this belief in the society and to defend it against the opponents. The first of these attempts was the Akhbari school, which advocated occultation by basing it on verse, hadith and ahbar. The other was the attitude that dealt with the issue with the rational explanations pioneered by the Usuli school, which started with Sheikh Mufid. As a result of the works that we have applied to present an evaluation of the arguments used by both schools in explaining occultation, it has been understood that the belief in occultation was revealed through some basic issues in both schools. The Akhbaris prioritized traditions on issues such as the birth of the Imam, the cause of the occultation, the duration of the occultation, the longevity of the Imam, the benefits of the Imam in the occultation, and the appearance of the Imam, while the Usulis tried to explain these matters with rational arguments. However, it has been observed that both schools adopt a similar attitude by resorting to reason and traditions betweentimes. It is important that making important rational interpretations of the Akhbari school and the Usuli school, in which rational arguments come to the fore, gave weight to narration in the explanation of some issues. [ABSTRACT FROM AUTHOR]

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]

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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]

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]

• We evaluate occultation atmospheric profiles and their derived parameters in both land and sea areas using ERA5 pressure-level products as verification data. • Globally, the mean STD is 1.28 K, 1.04 hpa, and 46.27 % for temperature, pressure, and specific humidity from earth observations of FY-3E occultation, respectively. • Fresh FY-3E surpasses its predecessor FY-3D in the precision of releasing atmospheric profile and derived parameters (ZTD, Tm, PWV). • But FY-3E is inferior to the other well-known occultation projects, including COSMIC-2, SPIRE, and METOP. As a space-borne GNSS observation, occultation effectively fills up the data gap caused by the absence of ground-based stations, especially on the ocean. With the launch of more low-orbit satellites, more and more occultation projects have been formed and offered atmosphere profiles. FY-3E is nearly the latest fully operated meteorological satellite in the Feng Yun series, so its atmospheric profile products are rarely discussed. Therefore, we evaluate FY-3E atmosphere profiles over the land with radiosonde data, and using ERA5 pressure-level products as verification data in both land and sea areas. Moreover, three critical parameters, ZTD, Tm, and PWV, are derived using occultation atmosphere profiles, and assessed with the GNSS data in the land area, and ERA5 data in both land and sea areas. From the results, the precision evaluated by the ground data is slightly lower than the ERA5 validation. The FY-3E results are compared with the predecessor FY-3D and other common occultation systems products, including COSMIC-2, SPIRE, and METOP. The comparisons show that FY-3E surpasses FY-3D in accuracy but is inferior to the other former occultation projects. Overall, the METOP has the best performance, and the COSMIC-2 is second and approximated to the SPIRE. The evaluations are significant for the community to know the current performance of FY-3E occultation. Besides, the results of derived parameters offer a reference for applying occultation products, which broadens the application scenarios of occultation observations. [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.