Abstract
Carbon-climate feedbacks, which amplifies or attenuates atmospheric CO
2
from fossil fuel emissions, are one of the largest sources of uncertainty in climate projections. However, these ...feedbacks depend both on temperature and its coupling to water and energy cycles, especially in the tropics. We show that atmospheric aridity—quantified as vapor pressure deficit (VPD)—is a good proxy for this coupling. Tropical VPD is strongly correlated to the global CO
2
growth rate (CGR) with observed present-day sensitivities of −2.5 ± 0.4 GtC mb
−1
yr
−1
. The sensitivity of CGR to tropical VPD interannual variability has increased by a factor of 1.7 ± 0.3 in the 21st century. A combination of causality and statistical analysis point to mechanistic moisture drivers of the VPD–CGR sensitivities, independent of temperature. Observational records provide evidence that tropical atmospheric aridity is linked to both water deficit and spatially correlated with evaporative fraction suggesting that CGR variability is indirectly driven by land—atmosphere coupling (compound soil and atmospheric drought). This coupling is manifest as a kind of carbon-climate feedback in CMIP6 Earth System Models where long–term increases in tropical VPD reduce tropical carbon storage but with a substantial inter-model range −1.4 to −59.4 GtC mb
−1
. However, by employing a hierarchical emergent constraint, the best estimate of atmospheric aridity—carbon cycle feedback (
φ
TL
) is
−
19
±
10 GtC mb
−1
, which is 28% lower than model estimates with an uncertainty reduction of 50%. Our results bridge the role of moisture and land–atmosphere coupling on net carbon variability to the vulnerability of carbon storage in a changing climate.
Optimal Estimation (OE) methods can simultaneously estimate surface and atmospheric properties from remote Visible/Shortwave imaging spectroscopy. Simultaneous solutions can improve retrieval ...accuracy with principled uncertainty quantification for hypothesis testing. While OE has been validated under benign atmospheric conditions, future global missions will observe environments with high aerosol and water vapor loadings. This work addresses the gap with diverse scenes from NASA's Next Generation Airborne Visible Infrared Imaging Spectrometer (AVIRIS-NG) India campaign. We refine atmospheric models to represent variable aerosol optical depths and properties. We quantify retrieval accuracy and information content for both reflectance and aerosols over different surface types, comparing results to in situ and remote references. Additionally, we assess uncertainty of maximum a posteriori solutions using linearized estimates as well as sampling-based inversions that more completely characterize posterior uncertainties. Principled uncertainty quantification can combine multiple spacecraft data products while preventing local environmental biases in future global investigations.
•We validate Optimal Estimation (OE) atmospheric correction for challenging conditions.•Linearized and MCMC estimates provide rigorous uncertainty quantification.•OE with aerosol and H2O vapor estimation significantly improves reflectance accuracy.•Retrieved aerosol properties are consistent with in-situ and remote space-based data.
We develop method of characteristics schemes based on explicit Runge–Kutta and pseudo‐Runge–Kutta third‐ and fourth‐order solvers along the characteristics. Schemes based on Runge–Kutta solvers are ...found to be strongly unstable for certain physics‐motivated models. In contrast, schemes based on pseudo‐Runge–Kutta solvers are shown to be only weakly unstable for periodic boundary conditions and essentially stable for the more physically relevant nonreflecting boundary conditions. Our implementation of nonreflecting boundary conditions does not rely on interpolation.
Direct detection of dark energy or modified gravity may finally be within reach due to ultrasensitive instrumentation such as atom interferometry capable of detecting incredibly small scale ...accelerations. Forecasts, constraints and measurement bounds can now too perhaps be estimated from accurate numerical simulations of the fifth force and its Laplacian field at solar system scales. The cubic Galileon gravity scalar field model (CGG), which arises in various massive gravity models including the Dvali-Gabadadze-Porrati (DGP) braneworld model, describes modified gravity incorporating a Vainshtein screening mechanism. The nonlinear derivative interactions in the CGG equation suppress the field near regions of high density, thereby restoring general relativity (GR) while far from such regions, field enhancement is comparable to GR and the equation is dominated by a linear term. This feature of the governing equation poses some numerical challenges for computation of the scalar potential, force and Laplacian fields even under stationary conditions. Here we present a numerical method based on finite differences for solution of the static CGG scalar field for a 2D axisymmetric Sun-Earth system and a 3D Cartesian Sun-Earth-Moon system. The method relies on gradient descent of an integrated residual based on the normal attractive branch of the CGG equation. The algorithm is shown to be stable, accurate and rapidly convergent toward the global minimum state. We hope this numerical study, which can easily be extended to include smaller bodies such as detection satellites, will prove useful to future measurement of modified gravity force fields at solar system scales.
Photonic technologies offer numerous functionalities that can be used to realize astrophotonic
instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large
...Telescope in Chile that combines the light-gathering power of four 8 m telescopes through a
complex photonic interferometer. Fully integrated astrophotonic devices stand to offer critical
advantages for instrument development, including extreme miniaturization when operating at the
diffraction-limit, as well as integration, superior thermal and mechanical stabilization owing to the
small footprint, and high replicability offering significant cost savings. Numerous astrophotonic
technologies have been developed to address shortcomings of conventional instruments to date,
including for example the development of photonic lanterns to convert from multimode inputs to
single mode outputs, complex aperiodic fiber Bragg gratings to filter OH emission from the
atmosphere, complex beam combiners to enable long baseline interferometry with for example,
ESO Gravity, and laser frequency combs for high precision spectral calibration of spectrometers.
Despite these successes, the facility implementation of photonic solutions in astronomical
instrumentation is currently limited because of (1) low throughputs from coupling to fibers,
coupling fibers to chips, propagation and bend losses, device losses, etc, (2) difficulties with scaling
to large channel count devices needed for large bandwidths and high resolutions, and (3) efficient
integration of photonics with detectors, to name a few. In this roadmap, we identify 24 key areas
that need further development. We outline the challenges and advances needed across those areas
covering design tools, simulation capabilities, fabrication processes, the need for entirely new
components, integration and hybridization and the characterization of devices. To realize these
advances the astrophotonics community will have to work cooperatively with industrial partners
who have more advanced manufacturing capabilities. With the advances described herein,
multi-functional integrated instruments will be realized leading to novel observing capabilities for
both ground and space based platforms, enabling new scientific studies and discoveries.
We perform a joint analysis of the cosmic microwave background (CMB) and Galactic emission from the WMAP 7 year temperature data. Using the Commander code, based on Gibbs sampling, we simultaneously ...derive the CMB and Galactic components on scales larger than 1degrees with improved sensitivity over previous work. We conduct a detailed study of the low-frequency Galactic foreground, focusing on the "microwave haze" emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse Galactic emission when including Haslam 408 MHz data and when jointly modeling the spinning and thermal dust emission. We examine whether the hypothetical Galactic haze can be explained by a spatial variation of the synchrotron spectral index, and find that the excess of emission around the Galactic center is stable with respect to variations of the foreground model. Our results demonstrate that the new Galactic foreground component-the microwave haze-is indeed present.
ABSTRACT In addition to primary fluctuations, cosmic microwave background (CMB) temperature maps contain a wealth of additional information in the form of secondary anisotropies. However, secondary ...effects that can be identified with individual objects, such as the thermal and kinetic Sunyaev-Zel'dovich (TSZ-KSZ) effects due to galaxy clusters, are difficult to unambiguously disentangle from foreground contamination and the primary CMB. We develop a Bayesian formalism to rigorously characterize anisotropies that are localized on the sky, taking the TSZ and KSZ effects as an example. Using a Gibbs sampling scheme, we are able to efficiently sample from the joint posterior distribution for a multi-component model of the sky with many thousands of correlated physical parameters. The posterior can then be exactly marginalized to estimate the properties of the secondary anisotropies, fully taking into account degeneracies with the other signals in the CMB map. We show that this method is computationally tractable using a simple implementation based on the existing Commander component separation code and discuss how other types of secondary anisotropy can be accommodated within our framework.
This paper examines several problematic issues in the presentation of information related to earnings per share (EPS) that are common to college textbooks and popular investment websites. U.S. ...generally accepted accounting principles (GAAP) require disclosure of EPS for all publicly listed firms. In fact, EPS is the only financial ratio required by GAAP and it is the only financial ratio with a formula specified by GAAP. Despite these facts, many college textbooks and investment websites present incorrect formulas for the computation of EPS. Furthermore, many textbooks and investment websites either explicitly or implicitly encourage students and investors to interpret EPS incorrectly. This paper discusses these issues and contrasts proper EPS computation and interpretation with the most common errors in computation and interpretation.
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