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The multiannual global mean of aerosol optical depth at 550 nm (AOD550) over land is ~0.19, and that over oceans is ~0.13. About 45 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions. We present an inherently calibrated retrieval (i.e., no need for radiance calibration) to simultaneously measure AOD and the aerosol phase function parameter, g, based on measurements of azimuth distributions of the Raman scattering probability (RSP), the near-absolute rotational Raman scattering (RRS) intensity. We employ radiative transfer model simulations to show that for solar azimuth RSP measurements at solar elevation and solar zenith angle (SZA) smaller than 80°, RSP is insensitive to the vertical distribution of aerosols and maximally sensitive to changes in AOD and g under near-molecular scattering conditions. The University of Colorado two-dimensional Multi-AXis Differential Optical Absorption Spectroscopy (CU 2-D-MAX-DOAS) instrument was deployed as part of the Two Column Aerosol Project (TCAP) at Cape Cod, MA, during the summer of 2012 to measure direct sun spectra and RSP from scattered light spectra at solar relative azimuth angles (SRAAs) between 5 and 170°. During two case study days with (1) high aerosol load (17 July, 0.3 < AOD430 < 0.6) and (2) near-molecular scattering conditions (22 July, AOD430 < 0.13) we compare RSP-based retrievals of AOD430 and g with data from a co-located CIMEL sun photometer, Multi-Filter Rotating Shadowband Radiometer (MFRSR), and an airborne High Spectral Resolution Lidar (HSRL-2). The average difference (relative to DOAS) for AOD430 is +0.012 ± 0.023 (CIMEL), -0.012 ± 0.024 (MFRSR), -0.011 ± 0.014 (HSRL-2), and +0.023 ± 0.013 (CIMELAOD - MFRSRAOD) and yields the following expressions for correlations between different instruments: DOASAOD = - (0.019 ± 0.006) + (1.03 ± 0.02)×CIMELAOD (R2 = 0.98), DOASAOD = -(0.006 ± 0.005)+(1.08 ± 0.02)×MFRSRAOD (R2 = 0.98), and CIMELAOD=(0.013 ± 0.004)+(1.05 ± 0.01)× MFRSRAOD (R2=0.99). The average g measured by DOAS on both days was 0.66 ± 0.03, with a difference of 0.014 ± 0.05 compared to CIMEL. Active steps to minimize the error in the RSP help to reduce the uncertainty in retrievals of AOD and g. As AOD decreases and SZA increases, the RSP signal-to-noise ratio increases. At AOD430 ~ 0.4 and 0.10 the absolute AOD errors are ~ 0.014 and 0.003 at 70° SZA and 0.02 and 0.004 at 35°SZA. Inherently calibrated, precise AOD and g measurements are useful to better characterize the aerosol direct effect in urban polluted and remote pristine environments.

This paper presents the global project Network for Observation of Volcanic and Atmospheric Change (NOVAC), the aim of which is automatic gas emission monitoring at active volcanoes worldwide. Data from the network will be used primarily for volcanic risk assessment but also for geophysical research, studies of atmospheric change, and ground validation of satellite instruments. A novel type of instrument, the scanning miniaturized differential optical absorption spectroscopy (Mini‐DOAS) instrument, is applied in the network to measure volcanic gas emissions by UV absorption spectroscopy. The instrument is set up 5–10 km downwind of the volcano under study, and typically two to four instruments are deployed at each volcano in order to cover different wind directions and to facilitate measurements of plume height and plume direction. Two different versions of the instrument have been developed. Version I was designed to be a robust and simple instrument for measurement of volcanic SO2 emissions at high time resolution with minimal power consumption. Version II was designed to allow the best possible spectroscopy and enhanced flexibility in regard to measurement geometry at the cost of larger complexity, power consumption, and price. In this paper the project is described, as well as the developed software, the hardware of the two instrument versions, measurement strategies, data communication, and archiving routines. As of April 2009 a total of 46 instruments have been installed at 18 volcanoes worldwide. As a typical example, the installation at Tungurahua volcano in Ecuador is described, together with some results from the first 21 months of operation at this volcano.

Adapting Educational and Psychological Tests for Cross-Cultural Assessment critically examines and advances new methods and practices for adapting tests for cross-cultural assessment and research. The International Test Commission (ITC) guidelines for test adaptation and conceptual and methodological issues in test adaptation are described in detail, and questions of ethics and concern for validity of test scores in cross-cultural contexts are carefully examined. Advances in test translation and adaptation methodology, including statistical identification of flawed test items, establishing equivalence of different language versions of a test, and methodologies for comparing tests in multiple languages, are reviewed and evaluated. The book also focuses on adapting ability, achievement, and personality tests for cross-cultural assessment in educational, industrial, and clinical settings. This book furthers the ITC's mission of stimulating research on timely topics associated with assessment. It provides an excellent resource for courses in psychometric methods, test construction, and educational and/or psychological assessment, testing, and measurement. Written by internationally known scholars in psychometric methods and cross-cultural psychology, the collection of chapters should also provide essential information for educators and psychologists involved in cross-cultural assessment, as well as students aspiring to such careers. Contents: Preface. Part I: Cross-Cultural Adaptation of Educational and Psychological Tests: Theoretical and Methodological Issues. R.K. Hambleton, Issues, Designs, and Technical Guidelines for Adapting Tests Into Multiple Languages and Cultures. F.J.R. van de Vijver, Y.H. Poortinga, Conceptual and Methodological Issues in Adapting Tests. T. Oakland, Selected Ethical Issues Relevant to Test Adaptations. S.G. Sireci, L. Patsula, R.K. Hambleton, Statistical Methods for Identifying Flaws in the Test Adaptation Process. S.G. Sireci, Using Bilinguals to Evaluate the Comparability of Different Language Versions of a Test. L.L. Cook, A.P. Schmitt-Cascallar, Establishing Score Comparability for Tests Given in Different Languages. L.L. Cook, A.P. Schmitt-Cascallar, C. Brown, Adapting Achievement and Aptitude Tests: A Review of Methodological Issues. Part II: Cross-Cultural Adaptation of Educational and Psychological Tests: Applications to Achievement, Aptitude, and Personality Tests. C.T. Fitzgerald, Test Adaptation in a Large-Scale Certification Program. C.Y. Maldonado, K.F. Geisinger, Conversion of the Wechsler Adult Intelligence Scale Into Spanish: An Early Test Adaption Effort of Considerable Consequence. N.K. Tanzer, Developing Tests for Use in Multiple Languages and Cultures: A Plea for Simultaneous Development. F. Drasgow, T.M. Probst, The Psychometrics of Adaptation: Evaluating Measurement Equivalence Across Languages and Cultures. M. Beller, N. Gafni, P. Hanani, Constructing, Adapting, and Validating Admissions Tests in Multiple Languages: The Israeli Case. P.F. Merenda, Cross-Cultural Adaptation of Educational and Psychological Testing. C.D. Spielberger, M.S. Moscoso, T.M. Brunner, Cross-Cultural Assessment of Emotional States and Personality Traits.

In this article, the error metrics used for evaluating the performance of direction of arrival (DoA) estimation are thoroughly investigated to recommend the most suitable one. This investigation highlights the lack of consensus in the literature regarding the selection and definition of these metrics. We show that this disparity is particularly serious in 2D DoA estimation, an aspect often overlooked by many authors. Notably, certain widely accepted error metrics can yield inaccurate and misleading results. Therefore, this article advocates for the adoption of a specific error metric that ensures accurate and meaningful assessments of 2D DoA estimation. A set of numerical and experimental results is presented to demonstrate the potential of the proposed error metric compared to other well-known metrics. Unlike other metrics, our proposed error definition is frame-independent. Finally, practical use cases are briefly discussed to highlight the pervasive impact of this fundamental definition.

Accurately forecasting runoff is vital for balancing human water demands, mitigating flood risks, and safeguarding ecological integrity. However, the nonlinear and non-stationary characteristics of hydrological processes pose significant challenges for conventional models. To address these issues, this study proposes a novel hybrid DOA-PSO-LSSVM model, which integrates the Dream Optimization Algorithm (DOA) for global exploration, Particle Swarm Optimization (PSO) for local refinement, and Least Squares Support Vector Machine (LSSVM) for nonlinear learning. Instead of relying on signal decomposition or manual parameter tuning, the proposed framework directly optimizes LSSVM hyperparameters through a hybrid global–local search strategy, effectively reducing mode mixing, subjectivity in parameter selection, and computational burden. Using 30 years of hydro-meteorological data from the upper Heihe River Basin, China, the hybrid model was compared with LSSVM, PSO-LSSVM, and DOA-LSSVM. Results demonstrate that DOA-PSO-LSSVM consistently achieved the highest predictive accuracy, with RMSE reductions of 4–23% and correlation coefficients (r) above 0.95 across stations. Beyond accuracy, the model exhibits robustness across different meteorological input scenarios and shows strong capability in simulating peak flows and water balance. This study advances hyperparameter optimization in runoff prediction and provides practical implications for sustainable water management and disaster prevention.

Direction-of-arrival (DOA) estimation is the preliminary stage of communication, localization, and sensing. Hence, it is a canonical task for next-generation wireless communications, namely beyond 5G (B5G) or 6G communication networks. Both massive multiple-input multiple-output (MIMO) and millimeter wave (mmW) bands are emerging technologies that can be implemented to increase the spectral efficiency of an area, and a number of expectations have been placed on them for future-generation wireless communications. Meanwhile, they also create new challenges for DOA estimation, for instance, through extremely large-scale array data, the coexistence of far-field and near-field sources, mutual coupling effects, and complicated spatial-temporal signal sampling. This article discusses various open issues related to DOA estimation for B5G/6G communication networks. Moreover, some insights on current advances, including arrays, models, sampling, and algorithms, are provided. Finally, directions for future work on the development of DOA estimation are addressed.

Previous efforts to measure atmospheric iodine have focused on marine and coastal regions. We report the first ground‐based tropospheric iodine monoxide (IO) radical observations over the central continental United States. Throughout April 2022, IO columns above Storm Peak Laboratory, Colorado (3,220 m.a.s.l.) ranged from 0.7 ± 0.5 to 3.6 ± 0.5 × 1012 (average: 1.9 × 1012 molec cm−2). IO was consistently elevated in air masses transported from over the Pacific Ocean. The observed IO columns were up to three times higher and the range was larger than predicted by a global model, which warrants further investigation into iodine sources, sinks, ozone loss, and particle formation. IO mixing ratios increased with altitude. At the observed levels, iodine may be competitive with bromine as an oxidant of elemental mercury at cold temperatures typical of the free troposphere. Iodine‐induced mercury oxidation is missing in atmospheric models, understudied, and helps explain model underestimation of oxidized mercury measurements. Plain Language Summary Halogens such as chlorine, bromine, and iodine are highly reactive gases that participate in atmospheric chemistry, including ozone destruction, particle formation, modification of greenhouse gas lifetime (i.e., methane, dimethylsulfide), and the oxidation of elemental mercury. Iodine mainly enters the atmosphere from oceans; therefore, past measurements of atmospheric iodine have focused on marine and polar regions. This study describes the first lower atmospheric measurements of iodine monoxide (IO) radicals at a remote mountaintop site in the central continental United States. These measurements indicate that the concentration of IO radicals showed a large range over the course of 1 month and reached levels up to three times higher than predicted by a global atmospheric chemistry model. These observations suggest that our understanding of the iodine sources and sinks to the free troposphere may be incomplete. Moreover, we suggest that iodine's contribution to ozone destruction and mercury chemistry may be underestimated; in particular, iodine may be competitive with bromine in the oxidation of elemental mercury in the free troposphere. Key Points Measurements of iodine monoxide radicals at Storm Peak Laboratory are up to three times higher than predicted by GEOS‐Chem IO tropospheric column variability is significant and highlights a need to better understand sources and sinks of tropospheric iodine Iodine may rival bromine as a tropospheric mercury oxidant; iodine‐mercury chemistry is understudied and missing in atmospheric models

Sparse arrays can increase the array aperture, thereby enhancing angular resolution. However, this also introduces additional computational complexity. This letter proposes a symmetric sparse array structure, where subarrays with different inter‐element spacings sample distinct spatial domain signals, analogous to the use of mother wavelets at different scales in wavelet theory to process various frequency components of a signal. The root‐MUSIC method can be directly applied to the proposed method, and the simulations demonstrate that it achieves direction‐of‐arrival estimation performance comparable to that of super‐nested arrays while maintaining lower computational complexity.

With the rapid development of communication, radar, sonar and many other fields, angle measurement has become a very important field in signal processing. Super resolution angle measurement, compared with the traditional angle measurement, has more advantages in accuracy, so it is widely used in practical production. Super resolution angle measurement includes MUSIC algorithm and ESPRIT algorithm. This paper firstly compares the MUSIC algorithm and ESPRIT algorithm, then elaborates the ESPRIT algorithm and deduces the process. In this paper, DOA estimation based on ESPRIT algorithm is carried out for three different number of input signal sources, and the errors are analysed according to different SNR (signal to noise ratio) values. Finally, based on the simulation results, the effectiveness of ESPRIT algorithm is evaluated.

In a traditional antenna array direction finding system, all the antenna sensors need to work or shut down at the same time, which often leads to signal crosstalk, signal distortion, and other electromagnetic compatibility problems. In addition, the direction-finding algorithm in a traditional system needs a tremendous spectral search, which consumes considerable time. To compensate for these deficiencies, a reconfigurable antenna array direction finding system is established in this paper. This system can dynamically load part or all of the antennas through microwave switches (such as a PIN diode) and conduct a fast direction of arrival (DOA) search. First, the hardware structure of the reconfigurable antenna is constructed. Then, based on the conventional spatial domain search algorithm, an improved transform domain (TD) search algorithm is proposed. The effectiveness of the system has been proven by real experiments, and the advantage of the system has been verified by detailed simulations.