Atmos. Meas. techniques

The Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) – Part 1: Instrument description and level 1 radiances
Jonathan E. Murray, Laura Warwick, Helen Brindley, Alan Last, Patrick Quigley, Andy Rochester, Alexander Dewar, and Daniel Cummins
Atmos. Meas. Tech., 17, 4757–4775, https://doi.org/10.5194/amt-17-4757-2024, 2024
The Far INfrarEd Spectrometer for Surface Emissivity, FINESSE, is designed to measure the ability of natural surfaces to emit infrared radiation. FINESSE combines a commercial instrument with custom-built optics to view a surface from different angles with complementary views of the sky. Its choice of internal components means it can cover a wide range of wavelengths, extending into the far-infrared. We characterize FINESSE’s uncertainty budget and provide examples of its measurement capability.

The Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) – Part 2: First measurements of the emissivity of water in the far-infrared
Laura Warwick, Jonathan E. Murray, and Helen Brindley
Atmos. Meas. Tech., 17, 4777–4787, https://doi.org/10.5194/amt-17-4777-2024, 2024
We describe a method for measuring the emissivity of natural surfaces using data from the new Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) instrument. We demonstrate our method by making measurements of the emissivity of water. We then compare our results to the emissivity predicted using a model and find good agreement. The observations from FINESSE are novel because they allow us to determine surface emissivity at longer wavelengths than have been routinely measured before.

Global sensitivity analysis of simulated remote sensing polarimetric observations over snow
Matteo Ottaviani, Gabriel Harris Myers, and Nan Chen
Atmos. Meas. Tech., 17, 4737–4756, https://doi.org/10.5194/amt-17-4737-2024, 2024
We analyze simulated polarization observations over snow to investigate the capabilities of remote sensing to determine surface and atmospheric properties in snow-covered regions. Polarization measurements are demonstrated to aid in the determination of snow grain shape, ice crystal roughness, and the vertical distribution of impurities in the snow–atmosphere system, data that are critical for estimating snow albedo for use in climate models.

Drone CO2 measurements during the Tajogaite volcanic eruption
John Ericksen, Tobias P. Fischer, G. Matthew Fricke, Scott Nowicki, Nemesio M. Pérez, Pedro Hernández Pérez, Eleazar Padrón González, and Melanie E. Moses
Atmos. Meas. Tech., 17, 4725–4736, https://doi.org/10.5194/amt-17-4725-2024, 2024
Volcanic eruptions emit significant quantities of carbon dioxide (CO2) to the atmosphere. We present a new method for directly determining the CO2 emission from a volcanic eruption on the island of La Palma, Spain, using an unpiloted aerial vehicle (UAV). We also collected samples of the emitted CO2 and analyzed their isotopic composition. Together with the emission rate the isotopic data provide valuable information on the state of volcanic activity and the potential evolution of the eruption.

Impact and Optimization of Calibration Conditions for Air Quality Sensors in the Long-term Field Monitoring
Han Mei, Peng Wei, Meisam Ahmadi Ghadikolaei, Nirmal Kumar Gali, Ya Wang, and Zhi Ning
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-130,2024
Preprint under review for AMT (discussion: open, 0 comments)
Long-term field testing across diverse climatic environments is conducted to identify the optimized calibration conditions for NO2, NO, CO, and O3 electrochemical sensors. The results uncovered three factors that influence calibration performance: calibration period, concentration range, and time averaging. We developed a comprehensive framework for the best sensor calibration practices, which serves as a valuable reference for calibrating various sensor types used in air quality monitoring.

Improving the Gaussianity of radar reflectivity departures between observations and simulations using symmetric rain rates
Yudong Gao, Lidou Huyan, Zheng Wu, and Bojun Liu
Atmos. Meas. Tech., 17, 4675–4686, https://doi.org/10.5194/amt-17-4675-2024, 2024
A symmetric error model built by symmetric rain rates handles the non-Gaussian error structure of the reflectivity error. The accuracy and linearization of rain rates can further improve the Gaussianity.

A nitrate ion chemical-ionization atmospheric-pressure-interface time-of-flight mass spectrometer (NO3− ToFCIMS) sensitivity study
Stéphanie Alage, Vincent Michoud, Sergio Harb, Bénédicte Picquet-Varrault, Manuela Cirtog, Avinash Kumar, Matti Rissanen, and Christopher Cantrell
Atmos. Meas. Tech., 17, 4709–4724, https://doi.org/10.5194/amt-17-4709-2024, 2024
Calibration exercises are essential for determining the accuracy of instruments. We performed calibrations on a NO3¯ ToFCIMS instrument to determine its sensitivity and linearity for detecting various organic compounds. Our findings revealed significant variability, over several orders of magnitude, in the calibration factors obtained. The results suggest that relying on a single calibration factor from H2SO4 for the quantification of all compounds detected by this technique is not appropriate.

On the temperature stability requirements of free-running Nd:YAG lasers for atmospheric temperature profiling through the rotational Raman technique
José Alex Zenteno-Hernández, Adolfo Comerón, Federico Dios, Alejandro Rodríguez-Gómez, Constantino Muñoz-Porcar, Michaël Sicard, Noemi Franco, Andreas Behrendt, and Paolo Di Girolamo
Atmos. Meas. Tech., 17, 4687–4694, https://doi.org/10.5194/amt-17-4687-2024, 2024
We study how the spectral characteristics of a solid-state laser in an atmospheric temperature profiling lidar using the Raman technique impact the temperature retrieval accuracy. We find that the spectral widening, with respect to a seeded laser, has virtually no impact, while crystal-rod temperature variations in the laser must be kept within a range of 1 K for the uncertainty in the atmospheric temperature below 1 K. The study is carried out through spectroscopy simulations.

Evaluation of the effects of different lightning protection rods on the data quality of C-band weather radars
Cornelius Hald, Maximilian Schaper, Annette Böhm, Michael Frech, Jan Petersen, Bertram Lange, and Benjamin Rohrdantz
Atmos. Meas. Tech., 17, 4695–4707, https://doi.org/10.5194/amt-17-4695-2024, 2024
Weather radars should use lightning protection to be safe from damage, but the rods can reduce the quality of the radar measurements. This study presents three new solutions for lightning protection for weather radars and evaluates their influence on data quality. The results are compared to the current system. All tested ones have very little effect on data, and a new lightning protection system with four rods is recommended for the German Meteorological Service.

Limitations in wavelet analysis of non-stationary atmospheric gravity wave signatures in temperature profiles
Robert Reichert, Natalie Kaifler, and Bernd Kaifler
Atmos. Meas. Tech., 17, 4659–4673, https://doi.org/10.5194/amt-17-4659-2024, 2024
Imagine you want to determine how quickly the pitch of a passing ambulance’s siren changes. If the vehicle is traveling slowly, the pitch changes only slightly, but if it is traveling fast, the pitch also changes rapidly. In a similar way, the wind in the middle atmosphere modulates the wavelength of atmospheric gravity waves. We have investigated the question of how strong the maximum wind may be so that the change in wavelength can still be determined with the help of wavelet transformation.

Applicability of the inverse dispersion method to measure emissions from animal housings
Marcel Bühler, Christoph Häni, Albrecht Neftel, Patrice Bühler, Christof Ammann, and Thomas Kupper
Atmos. Meas. Tech., 17, 4649–4658, https://doi.org/10.5194/amt-17-4649-2024, 2024
Methane was released from an artificial source inside a barn to test the applicability of the inverse dispersion method (IDM). Multiple open-path concentration devices and ultrasonic anemometers were used at the site. It is concluded that, for the present study case, the effect of a building and a tree in the main wind axis led to a systematic underestimation of the IDM-derived emission rate probably due to deviations in the wind field and turbulent dispersion from the ideal assumptions.

A new non-linearity correction method for the spectrum from the Geostationary Inferometric Infrared Sounder on board Fengyun-4 satellites and its preliminary assessments
Qiang Guo, Yuning Liu, Xin Wang, and Wen Hui
Atmos. Meas. Tech., 17, 4613–4627, https://doi.org/10.5194/amt-17-4613-2024, 2024
Non-linearity (NL) correction is a critical procedure to guarantee that the calibration accuracy of a spaceborne sensor approaches a reasonable level. Different from the classical method, a new NL correction method for a spaceborne Fourier transform spectrometer is proposed. To overcome the inaccurate linear coefficient from two-point calibration influencing NL correction, an iteration algorithm is established that is suitable for NL correction of both infrared and microwave sensors.

Multi-decadal atmospheric carbon dioxide measurements in Hungary, central Europe
László Haszpra
Atmos. Meas. Tech., 17, 4629–4647, https://doi.org/10.5194/amt-17-4629-2024, 2024
The paper evaluates a 30-year-long atmospheric CO2 data series from a mid-continental central European site, Hegyhátsál (HUN). It presents the site-specific features observed in the long-term evolution of the atmospheric CO2 concentration. Since the measurement data are widely used in atmospheric inverse models and budget calculations all around the world, the paper provides potentially valuable information for model tuning and interpretation of the model results.

Performance evaluation of an online monitor based on X-ray fluorescence for detecting elemental concentrations in ambient particulate matter
Ivonne Trebs, Céline Lett, Andreas Krein, Erika Matsumoto Kawaguchi, and Jürgen Junk
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-134,2024
Preprint under review for AMT (discussion: open, 0 comments)
This study explores the effectiveness of the Horiba PX-375 monitor for analyzing the elemental composition of airborne particulate matter (PM). Understanding this composition of PM is important for identifying its sources, assessing potential health risks, and developing strategies to reduce air pollution. The PX-375 monitor proved to be a valuable tool for ongoing air quality monitoring studies and could be particularly useful as pollution levels and sources change in the future.

Reliable water vapour isotopic composition measurements at low humidity using frequency-stabilised cavity ring-down spectroscopy
Mathieu Casado, Amaelle Landais, Tim Stoltmann, Justin Chaillot, Mathieu Daëron, Fréderic Prié, Baptiste Bordet, and Samir Kassi
Atmos. Meas. Tech., 17, 4599–4612, https://doi.org/10.5194/amt-17-4599-2024, 2024
Measuring water isotopic composition in Antarctica is difficult because of the extremely cold temperature in winter. Here, we designed a new infrared spectrometer able to measure the vapour isotopic composition during more than 95 % of the year in the coldest locations of Antarctica, whereas current commercial instruments are only able to measure during the warm summer months in the interior.

Observing atmospheric rivers using multi-GNSS airborne radio occultation: system description and data evaluation
Bing Cao, Jennifer S. Haase, Michael J. Murphy Jr., and Anna M. Wilson
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-119,2024
Preprint under review for AMT (discussion: open, 0 comments)
This paper describes an Airborne Radio Occultation (ARO) observation system installed on reconnaissance aircraft that uses GPS signal refraction in the atmosphere to retrieve information about the temperature and moisture in the storm environment as far away as 400 km surrounding the flight track. The characteristics and quality of 1700 ARO refractivity profiles were assessed. These observations are collected to help understand atmospheric rivers and improve their forecasting.

Cloud phase estimation and macrophysical properties of low-level clouds using in-situ and radar measurements over the Southern Ocean during the SOCRATES campaign
Anik Das, Baike Xi, Xiaojian Zheng, and Xiquan Dong
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-124,2024
Preprint under review for AMT (discussion: open, 0 comments)
Understanding the cloud phase and macrophysical properties of Southern Ocean clouds is crucial to enhancing our understanding of the region. The cloud radar and in-situ probes during the SOCRATES aircraft campaign are used to develop a new method to determine cloud boundaries and dominant phase. Low clouds (<3km) are found to be the most dominant cloud type (~90%), with liquid being the most dominant phase type, followed by ice and mixed with a greater incidence of drizzle around the cloud base.

Cloud masks and cloud type classification using EarthCARE CPR and ATLID
Hajime Okamoto, Kaori Sato, Tomoaki Nishizawa, Yoshitaka Jin, Shota Ogawa, Hiroshi Ishimoto, Yuichiro Hagihara, EIji Oikawa, Maki Kikuchi, Masaki Satoh, and Wooosub Roh
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-103,2024
Preprint under review for AMT (discussion: open, 0 comments)
The article gives the descriptions of the Japan Aerospace Exploration Agency (JAXA) level 2 (L2) cloud mask and cloud particle type algorithms for CPR and ATLID onboard Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) satellite. The 355nm-multiple scattering polarization lidar was used to develop ATLID algorithm. Evaluations show the agreements for CPR-only, ATLID-only and CPR-ATLID synergy algorithms to be about 80%, 85% and 80%, respectively on average for about two EarthCARE orbits.

Quantitative Error Analysis on Polarimetric Phased Array Radar Weather Measurements to Reveal Radar Performance and Configuration Potential
Junho Ho, Zhe Li, and Guifu Zhang
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-118,2024
Preprint under review for AMT (discussion: open, 0 comments)
This study quantitatively analyzes and compares weather measurements from planar (PPPAR) and cylindrical polarimetric phased array radars (CPPAR). It examines data quality, potential problems, and clarifies misunderstandings between the configurations. The findings highlight 2D PPPAR’s challenges in making accurate weather measurements when the beam steers off broadside. CPPAR shows promise in obtaining high-quality polarimetric data because of its azimuthal scan invariant beam characteristics.

Time-resolved measurements of the densities of individual frozen hydrometeors and fresh snowfall
Dhiraj K. Singh, Eric R. Pardyjak, and Timothy J. Garrett
Atmos. Meas. Tech., 17, 4581–4598, https://doi.org/10.5194/amt-17-4581-2024, 2024
Accurate measurements of the properties of snowflakes are challenging to make. We present a new technique for the real-time measurement of the density of freshly fallen individual snowflakes. A new thermal-imaging instrument, the Differential Emissivity Imaging Disdrometer (DEID), is shown to be capable of providing accurate estimates of individual snowflake and bulk snow hydrometeor density. The method exploits the rate of heat transfer during the melting of a snowflake on a hotplate.