Occultation Observations Research Articles

Development and Deployment of Large Solar Viewing Window Structures for Safe Public Solar Eclipse Observation

Development and Deployment of Large Solar Viewing Window Structures for Safe Public Solar Eclipse Observation

Combined analysis of the 12.8 and 15 μm JWST/MIRI eclipse observations of TRAPPIST-1 b

Combined analysis of the 12.8 and 15 μm JWST/MIRI eclipse observations of TRAPPIST-1 b

Unveiling Illumination Variations During a Lunar Eclipse: Multi-Wavelength Spaceborne Observations of the January 21, 2019 Event

Space-based observations of the total lunar eclipse on 21 January 2019 were conducted using the geostationary Earth-orbiting satellite Gaofen-4 (GF-4). This study represents a pioneering effort to address the observational gap in full-disk lunar eclipse photometry from space. With its high resolution and ability to capture the entire lunar disk, GF-4 enabled both quantitative and qualitative analyses of the variations in lunar brightness, as well as spectra and color changes, across two spatial dimensions, from the whole lunar disk to resolved regions. Our results indicate that before the totality phase of the lunar eclipse, the irradiance of the Moon diminishes to below approximately 0.19% of that of the uneclipsed Moon. Additionally, we observed an increase in lunar brightness at the initial entry into the penumbra. This phenomenon is attributed to the opposition effect, providing scientific evidence for this unexpected behavior. To investigate detailed spectral variations, specific calibration sites, including the Chang’E-3 landing site, MS-2 in Mare Serenitatis, and the Apollo 16 highlands, were analyzed. Notably, the red-to-blue ratio dropped below 1 near the umbra, contradicting the common perception that the Moon appears red during lunar eclipses. The red/blue ratio images reveal that as the Moon enters Earth’s umbra, it does not simply turn red; instead, a blue-banded ring appears at the boundary due to ozone absorption and the lunar surface composition. These findings significantly enhance our understanding of atmospheric effects on lunar eclipses and provide crucial reference information for the future modeling of lunar eclipse radiation, promoting the integration of remote sensing science with astronomy.

Expanded Linear Responsivity for Earth and Planetary Radiometry

Abstract Earth and planetary radiometry requires spectrally dependent observations spanning an expansive range in signal flux due to variability in celestial illumination, spectral albedo, and attenuation. Insufficient dynamic range inhibits contemporaneous measurements of dissimilar signal levels and restricts potential environments, time periods, target types, or spectral ranges that instruments observe. Next-generation (NG) advances in temporal, spectral, and spatial resolution also require further increases in detector sensitivity and dynamic range corresponding to increased sampling rate and decreased field of view (FOV), both of which capture greater intrapixel variability (i.e., variability within the spatial and temporal integration of a pixel observation). Optical detectors typically must support expansive linear radiometric responsivity, while simultaneously enduring the inherent stressors of field, airborne, or satellite deployment. Rationales for significantly improving radiometric observations of nominally dark targets are described herein, along with demonstrations of state-of-the-art (SOTA) capabilities and NG strategies for advancing SOTA. An evaluation of linear dynamic range and efficacy of optical data products is presented based on representative sampling scenarios. Low-illumination (twilight or total lunar eclipse) observations are demonstrated using a SOTA prototype. Finally, a ruggedized and miniaturized commercial-off-the-shelf (COTS) NG capability to obtain absolute radiometric observations spanning an expanded range in target brightness and illumination is presented. The presented NG technology combines a multipixel photon counter (MPPC) with a silicon photodetector (SiPD) to form a dyad optical sensing component supporting expansive dynamic range sensing, i.e., exceeding a nominal 10 decades in usable dynamic range documented for SOTA instruments.

No Thick Atmosphere on the Terrestrial Exoplanet Gl 486b

A primary science goal for JWST is to detect and characterize the atmospheres of terrestrial planets orbiting M dwarfs (M-Earths). The existence of atmospheres on M-Earths is highly uncertain because their host stars’ extended history of high X-ray and ultraviolet irradiation may act to completely remove their atmospheres. We present two JWST secondary eclipse observations of the M-Earth Gl 486b (also known as GJ 486b) between 5 and 12 μm. We combined these observations with a precise analysis of the host star parameters to derive a planetary dayside temperature of T p = 865 ± 14 K. We compared this temperature to the maximum expected temperature for a zero albedo, zero heat redistribution bare rock and derived a temperature ratio of R=Tp,daysideTp,max=0.97±0.01 . This value is consistent with an airless body with a slight nonzero albedo or a thin atmosphere with <1% H2O or <1 ppm CO2. However, it is inconsistent with an Earth- or Venus-like atmosphere, and the spectrum shows no clear emission or absorption features. Additionally, our observations are inconsistent with the water-rich atmospheric scenario allowed by previous transit observations and suggest the transmission spectrum was instead shaped by stellar contamination. Given the potential for atmospheric escape throughout the system’s ≥6.6 Gyr lifetime, we conclude that the observations are likely best explained by an airless planet. This result is the most precise measurement yet of terrestrial exoplanet thermal emission with JWST, which places a strong constraint on the position of the “cosmic shoreline” between airless bodies and those with atmospheres.

Physical properties of trans-Neptunian object (143707) 2003 UY117 derived from stellar occultation and photometric observations

Context. Trans-Neptunian objects (TNOs) are considered to be among the most primitive objects in our Solar System. Knowledge of their primary physical properties is essential for understanding their origin and the evolution of the outer Solar System. In this context, stellar occultations are a powerful and sensitive technique for studying these distant and faint objects. Aims. We aim to obtain the size, shape, absolute magnitude, and geometric albedo for TNO (143707) 2003 UY117. Methods. We predicted a stellar occultation by this TNO for 2020 October 23 UT and ran a specific campaign to investigate this event. We derived the projected profile shape and size from the occultation observations by means of an elliptical fit to the occultation chords. We also performed photometric observations of (143707) 2003 UY117 to obtain the absolute magnitude and the rotational period from the observed rotational light curve. Finally, we combined these results to derive the three-dimensional shape, volume-equivalent diameter, and geometric albedo for this TNO. Results. From the stellar occultation, we obtained a projected ellipse with axes of (282 ± 18) × (184 ± 32) km. The area-equivalent diameter for this ellipse is Deq,A = 228 ± 21 km. From our photometric R band observations, we derived an absolute magnitude of HV = 5.97 ± 0.07 mag using V − R = 0.46 ± 0.07 mag, which was derived from a V band subset of these data. The rotational light curve has a peak-to-valley amplitude of ∆m = 0.36 ± 0.13 mag. We find the most likely rotation period to be P = 12.376 ± 0.0033 hours. By combining the occultation with the rotational light curve results and assuming a triaxial ellipsoid, we derived axes of a × b × c = (332 ± 24) km × (216 ± 24) km × (180−24+28) km for this ellipsoid, and therefore a volume-equivalent diameter of Deq,V = 235 ± 25 km. Finally, the values for the absolute magnitude and for the area-equivalent diameter yield a geometric albedo of pV = 0.139 ± 0.027.

On the impact of the vertical structure of Martian water ice clouds on nadir atmospheric retrievals from simultaneous EMM/EXI and TGO/ACS-MIR observations.

Retrieving the optical depth of the Martian clouds (τcld) is a powerful way to monitor their spatial and temporal evolution. However, such retrievals from nadir imagery rely on several assumptions, including the vertical structure of the clouds in the atmosphere. Here we compare the results of cloud optical depth retrievals at 320 nm from the Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM) “Hope” orbiter performed using a basic uniform cloud profile used in previous studies and using derived cloud profiles obtained from near-simultaneous Solar Occultation observations in the 3.1–3.4 μm spectral range from the Middle-Infrared channel of the Atmospheric Chemistry Suite (ACS) instrument onboard the ESA Trace Gas Orbiter (TGO). We show that the latitudinal dependence of the cloud vertical profiles can have a strong impact on the nadir retrievals; neglecting it can lead to a significant underestimation of τcld in the polar regions (up to 25 % to 50 %, depending on the vertical distribution of the dust in the atmosphere) and to a lesser extent, to an overestimation of τcld around the equator. We also discuss the impact of a vertically-dependent particle size profile, as previous studies have shown the presence of very small water ice particles at the top of the clouds. From this analysis, we provide recommendations for the improvement of water ice cloud parameterization in radiative transfer algorithms in nadir atmospheric retrievals.

A Software Tool for the True Height Analysis of Ionograms Using the Iterative Gradient Correction (IGC) Method

AbstractDeriving the precise true height electron density profile from the measured ionosonde virtual heights is quite a challenging problem. Recently, Ankita and Tulasi Ram (2023, https://doi.org/10.1029/2023RS007808) presented a new method, Iterative Gradient Correction (IGC) method, for true height analysis that uses HF radio wave propagation path computations to reconstruct the true height profile. Through iterative corrections on electron density gradients between successive points, the IGC method minimizes errors below a specified tolerance at each point and reconstructs a complete electron density profile. The derived profiles from the IGC method are found to be accurate when compared with Incoherent Scatter Radar and Global Navigation Satellite System—Radio Occultation observations. To facilitate true height analysis by IGC method for a wider user community, a MATLAB‐based software has been developed and is outlined in this report. The software can be installed on any Windows platform and is designed with a user‐friendly interface for easy and efficient application by the users. It can analyze multiple scaled ionograms in a single run and outputs the real height profiles in ASCII format. Further, the software also captures important ionospheric parameters such as the base altitudes and peak frequencies of E‐ and F‐layers (e.g., hE, hF, foE, and foF2) etc., from the computed true height profiles and tabulates in a separate output file for the ready use. The software also provides the option for extrapolation of true height profile into top‐side ionosphere up to a user‐specified height and reconstructs the complete vertical electron density profile.

Unambiguous detection of mesospheric CO2 clouds on Mars using 2.7 μm absorption band from the ACS/TGO solar occultations

Mesospheric CO2 clouds are one of two types of carbon dioxide clouds known on Mars. We present observations of mesospheric CO2 clouds made by Atmospheric Chemistry Suite (ACS) onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO). We analyzed 1663 solar occultation sessions of Thermal InfraRed (TIRVIM) and Middle InfraRed (MIR) channels of ACS covering more than two Martian years that contain spectra of 2.7 μm carbon dioxide ice absorption band. That allowed us to unambiguously discriminate carbon dioxide ice aerosols from mineral dust and water ice aerosols, not relying on the information of atmospheric thermal conditions. CO2 clouds were detected in eleven solar occultation observations at altitudes from 39 km to 90 km. In five cases, there were two or three layers of CO2 clouds that were vertically separated by 5–15 km gaps. Effective radius of CO2 aerosol particles is in the range of 0.1–2.2 μm. Spectra produced by the smallest particles indicate a need for a better resolved CO2 ice refractive index. Nadir optical depth of CO2 clouds is in the range 5 × 10−4–4 × 10−2 at both 2.7 μm and 0.8 μm. Asymmetrical diurnal distribution of detections observed by ACS is potentially due to local time variations of temperature induced by thermal tides. Two out of five cases of carbon dioxide cloud detections made by the TIRVIM instrument reveal the simultaneous presence of CO2 ice and H2O ice aerosols. Temperature profiles measured by the Near InfraRed (NIR) channel of ACS are used to calculate CO2 saturation ratio S at locations of carbon dioxide clouds. Supersaturation S > 1 is detected in only 6 out of 19 cases of CO2 cloud layers; extremely low values of S < 0.1 are found in 9 out of 19 cases.

JWST-TST DREAMS: Nonuniform Dayside Emission for WASP-17b from MIRI/LRS

We present the first spectroscopic characterization of the dayside atmosphere of WASP-17b in the mid-infrared using a single JWST MIRI/LRS eclipse observation. From forward-model fits to the 5–12 μm emission spectrum, we tightly constrain the heat redistribution factor of WASP-17b to be 0.92 ± 0.02 at the pressures probed by this data, indicative of inefficient global heat redistribution. We also marginally detect a supersolar abundance of water, consistent with previous findings for WASP-17b, but note our weak constraints on this parameter. These results reflect the thermodynamically rich but chemically poor information content of MIRI/LRS emission data for high-temperature hot Jupiters. Using the eclipse mapping method, which utilizes the signals that the spatial emission profile of an exoplanet imprints on the eclipse light curve during ingress/egress due to its partial occultation by the host star, we also construct the first eclipse map of WASP-17b, allowing us to diagnose its multidimensional atmospheric dynamics for the first time. We find a day–night temperature contrast of order 1000 K at the pressures probed by this data, consistent with our derived heat redistribution factor, along with an eastward longitudinal hotspot offset of 18.7−3.8+11.1◦ , indicative of the presence of an equatorial jet induced by day–night thermal forcing being the dominant redistributor of heat from the substellar point. These dynamics are consistent with general circulation model predictions for WASP-17b. This work is part of a series of studies by the JWST Telescope Scientist Team, in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy.

Comparison of tropical cyclone structures over different ocean basins revealed in COSMIC-2 radio occultation observations

Utilizing three-years COSMIC-2 radio occultation (RO) bending angle (BA) observations from 1 October 2019 to 31 December 2022, composite structures of BA anomalies α−α¯env/α¯env in vertical and radial directions are generated for hurricanes, tropical storms and tropical depressions over the ocean basins of North Atlantic, West Pacific, East Pacific, South Pacific, North Indian, and South Indian. The magnitude and altitude of the maximum BA anomaly within hurricanes, tropical storms and tropical depressions are about (6 km, 14%), (5 km, 11%) and (3.5 km, 9%), respectively. The vertical and radial extents of BA anomaly exceeding 6% are (6 km, 450 km) and (7 km, 500 km) over North Atlantic and West Pacific oceans, respectively. The warm core of hurricane over East Pacific ocean displays the widest radial extent (650 km), while that over North India ocean has the deepest vertical extent (8.5 km). As expected, the BA anomalies of tropical storms and tropical depressions are weaker in magnitude and smaller in size than those of hurricanes. An exception is found for the maximum BA anomaly of hurricanes over South Pacific ocean is not located near hurricane centers but at the 175-km radial distance. Accordingly, the mean altitudes of the atmospheric boundary layer estimated from COSMIC-2 BA observations increase from the 175-km radial distances to both sides for hurricanes over South Pacific ocean, while those over the other five ocean basins increase from eye centers outward.

Upper limits of HO2 in the atmosphere of Mars from the ExoMars Trace Gas Orbiter

ABSTRACT Odd-hydrogen (HO$_\mathrm{x}$) species have a crucial role in regulating the chemistry of the atmosphere of Mars and are important to understand some of the most fundamental aspects regarding its atmospheric composition such as the long-term stability of CO$_2$. Despite the key role of these species for our understanding of the Martian photochemistry, there is little observational evidence constraining their abundances. In this study, we use infrared solar occultation observations from the Atmospheric Chemistry Suite aboard the ExoMars Trace Gas Orbiter to search for spectral signatures of HO$_2$ in the atmosphere of Mars. In our analysis of the data, we retrieve vertical profiles of pressure, temperature, and water vapour mixing ratio, but are unable to confidently detect the presence of HO$_2$ features in the spectra. We report upper limits of 15 ppbv (5$\sigma$), which represents an order of magnitude improvement with respect to previous investigations. Comparing the derived upper limits with the expectations from 3-dimensional Global Climate Models, we find that approximately an order of magnitude improvement in the instrument sensitivity would be required to detect this molecule and/or constrain the models.

Several outstanding issues concerning the ionosphere of Mars

Several outstanding issues concerning the ionosphere of Mars can be addressed with the support of radio occultation observations acquired near the solar zenith angle limit of 45∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document}. First, two fundamentally different types of instruments (topside radar sounding, radio occultations) have been used to characterize how the subsolar peak density changes over the solar cycle. Here we find that their results for solar minimum and solar maximum values of peak density are consistent. This verifies that systematic errors do not affect peak density measurements from either type of instrument. Second, reported descriptions of how the peak altitude changes with solar zenith angle are inconsistent. Specifically, values reported by radio occultation and radar sounder instruments for the characteristic lengthscale used to describe changes in peak altitude with solar zenith angle vary by a factor of two. We find that the change in peak altitude with solar zenith angle is governed by a lengthscale that is close to the thermospheric scale height, as predicted theoretically. However, this behavior is only apparent when the Mars–Sun distance is held fixed. Reported smaller values of this lengthscale, which are not consistent with theoretical expectations, were adversely affected by using near-terminator peak altitude values only, which display marked variability. Third, Viking Lander entry science data have been interpreted to suggest that the M1 layer is not present in the ionosphere at solar zenith angles of 45∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document} or smaller. We show radio occultation observations at 45∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document} in which the M1 layer is present. This suggests that the basic structure of the dayside ionosphere remains the same at all solar zenith angles.Graphical

Impact of Varying Number of Radio Occultation Observations on Regional Weather Prediction Over India During the Summer Monsoon Season

AbstractObserving system simulation experiments are carried out to investigate the added value of radio occultation (RO) refractivity observations with various spatial sampling scenarios on regional weather predictions across the Indian region. A full summer monsoon season (June through September 2020) was used to demonstrate how varying the numbers and horizontal resolutions of RO data impacted regional‐scale weather forecasting. The MPAS (Model for Prediction Across Scales) was used to produce a nature run at a maximum horizontal resolution of 10 km. Then the WRF model with 12‐km horizontal resolution was used to carry out assimilation/forecast experiments with varying number of simulated RO observations. When the performance of the experiments is taken into account for moisture, temperature, winds and rainfall, as well as prediction lengths, the results show that RO observations with 50‐km resolution assimilated every 6 hr would provide the best results. Increasing the horizontal resolution to 25 km per 6 hr shows little overall improvement. Furthermore, RO data with horizontal resolutions lower than 100 km per 6 hr have only a small impact on the regional numerical weather prediction system. The number of low Earth orbit satellites in low‐inclination orbits required to achieve occultations every 6 hr with 50‐km resolution based on the COSMIC‐2 mission is approximately 700. This work is relevant for the deployment of the cost‐effective RO observing system for improved weather forecasting over the Indian region.

УСВОЕНИЕ ДАННЫХ РАДИОЗАТМЕННЫХ НАБЛЮДЕНИЙ В ЧИСЛЕННОМ ПРОГНОЗЕ ПОГОДЫ

The paper discusses the principles of the assimilation of radio occultation observations into numerical weather prediction models. The most widely used approach is assimilation of the bending angle profiles obtained from the observations by the wave optics methods. The observation operators are constructed from the geometric optics equations and can be three-dimensional (3D), taking into account the actual field of meteorological parameters, or one-dimensional (1D), using only one vertical profile. In the approximation of weak gradients, the 3D operator is reduced to the two-dimensional (2D) one, which takes into account the section of the fields of meteorological parameters by the vertical plane of the occultation event. Another approach is the assimilation of the retrieved atmospheric refractivity profiles by means of a simplest 1D or more accurate 2D operator. Some examples of statistical comparisons of the profiles of temperature, pressure, and specific humidity obtained by variational assimilation with the GFS reanalysis data are given.

Observations of solar eclipses in russia: between the chronicles and the first scientific expeditions (18ʰᵗ – 19ʰᵗ Centuries)

A solar eclipse is a rare and spectacular celestial event that has a powerful emotional impact on people and is often reflected in their writings and communications. The reports of eclipse observations are contained in the 10th–17ʰᵗ century Russian chronicles. Modern observation reports, starting wiʰᵗ the 1887 eclipse, have also been well studied. In the intermediate period, starting from 1706, however, only three eclipses (1748, 1842 and 1851) have been described in publicly available sources despite the fact that 30 total and annular eclipses passed through Russia during this period. Using a computer program, the regions and time intervals were identified to search for the mentions of such eclipses. Possible sources include memoirs, reports and other documents written by educated people – participants in all kinds of campaigns, voyages, and expeditions, not necessarily the astronomical ones. As a result of studying diverse sources, a number of valuable reports of eclipse observations were discovered. Most often, these are the observations of eyewitnesses who had accidentally happened to be in the eclipse path. The firstly discovered materials shed light on the level of astronomical knowledge among various groups of the Russian population as well as equipment available to them, and touch upon the issues of local peoples’ superstitions and prejudices. A periodization of solar eclipse observations is also proposed.

Data Assimilation Impact of GNSS RO Measurements from Cube Satellites on Arctic Weather Forecasts

Abstract In this study, the effects of assimilating Global Navigation Satellite System (GNSS) radio occultation (RO) observations from existing and recently added commercial cube satellites on analyses and forecasts over the Arctic region were investigated by conducting observing system experiments (OSEs). Profiles of refractivity were assimilated with a local observation operator using the three-dimensional variational method. The analyses and forecasts from the OSEs were verified against ERA5 reanalysis, radiosonde observations, and buoy observations. In addition to the averaged impact on forecast skill, the impact of GNSS RO observations was further examined for an individual Arctic cyclone case, focusing on the added value of the cube satellite data. The effects of GNSS RO observations from existing satellites on analyses and forecasts over the Arctic region are positive, and the assimilation of GNSS RO observations from cube satellites leads to additional improvements, particularly for temperature in the upper troposphere and lower stratosphere (UTLS). Temperature biases in the UTLS are significantly reduced in the analyses, and the improved analyses result in better forecasts of upper-level potential vorticity and cyclone development when GNSS RO observations from cube satellites are assimilated. This result demonstrates the potential of GNSS RO data from cube satellites to enhance forecasts over the Arctic region.

Citizen Science on April 20th Total Solar Eclipse Observation

Citizen Science on April 20th Total Solar Eclipse Observation

Enhancing Exoplanet Ephemerides by Leveraging Professional and Citizen Science Data: A Test Case with WASP-77 A b

We present an updated ephemeris, and physical parameters, for the exoplanet WASP-77 A b. In this effort, we combine 64 ground- and space-based transit observations, 6 space-based eclipse observations, and 32 radial velocity observations to produce this target's most precise orbital solution to date aiding in the planning of James Webb Space Telescope and Ariel observations and atmospheric studies. We report a new orbital period of 1.360029395 ± 5.7 × 10−8 days, a new mid-transit time of 2459957.337860 ± 4.3 × 10−5 Barycentric Julian Date in the Barycentric Dynamical Timescale (BJDTDB) and a new mid-eclipse time of 2459956.658192 ± 6.7 × 10−5 BJDTDB. Furthermore, the methods presented in this study reduce the uncertainties in the planet's mass 1.6654 ± 4.5 × 10−3 M Jup and orbital period 1.360029395 ± 5.7 × 10−8 days by factors of 15.1 and 10.9, respectively. Through a joint fit analysis comparison of transit data taken by space-based and citizen science-led initiatives, our study demonstrates the power of including data collected by citizen scientists compared to a fit of the space-based data alone. Additionally, by including a vast array of citizen science data from ExoClock, Exoplanet Transit Database, and Exoplanet Watch, we can increase our observational baseline and thus acquire better constraints on the forward propagation of our ephemeris than what is achievable with Transiting Exoplanet Survey Satellite data alone.

CERRA, the Copernicus European Regional Reanalysis system

AbstractA regional reanalysis has been produced for a domain covering entire Europe from 1984 to 2021. The reanalysis is produced as part of the Copernicus Climate Change Service. The Service provides the high‐resolution deterministic Copernicus European Regional Reanalysis (CERRA), run at a horizontal resolution of 5.5 km, a 10‐member ensemble run at 11‐km resolution as well as an offline surface analysis, CERRA‐Land. CERRA‐EDA uses an ensemble data assimilation (EDA) technique to perturb the initial condition of the different members. Apart from the horizontal resolution the CERRA and CERRA‐EDA setups are the same; for example, the same data assimilation scheme, same physics parameterization as well as the same vertical levels. These new systems are built from HARMONIE cy40 version, including some back‐phased physics from a newer model version (cy42). Conventional observations, satellite‐based radiances, atmospheric motion vector winds and bending angle from radio occultation observations are used. In addition, ground‐based zenith total delay (ZTD) from global navigational satellite systems (GNSS) and local surface observations, rescued from historical archives at the local National Meteorological Services, are used. Another new feature is the construction of the background error statistics for the data assimilation. Information from the ensemble run, CERRA‐EDA, is used in the derivation of the background error statistics for the high‐resolution CERRA runs. These background error statistics are updated every second day. By doing so, daily environment variation is taken into account as well as all variations over the 37 years of production. The reanalyses and reforecasts from CERRA show an added value compared to the global ERA5 for almost all variables at the surface level. This becomes particularly clear when selecting smaller areas with complex terrain where the high resolution is beneficial. In the free atmosphere it is primarily the analyses and short forecasts, 3–6 hours, that give an added value.