Atmos. Meas. techniques

The GRAS-2 Radio Occultation Mission
Joel Rasch, Anders Carlström, Jacob Christensen, and Thomas Liljegren
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-60,2024
Preprint under review for AMT (discussion: open, 0 comments)
Soon the Metop Second Generation (Metop-SG) series of polar orbiting meteorological satellite will be launched. On these satellites the GRAS-2 instrument will be mounted. It will provide GNSS radio occultation measurements with unsurpassed accuracy. The occultation measurements are used routinely for numerical weather prognosis, i.e. predicting the weather. In this paper we describe the design of this new instrument and the novel methods developed to process the data.

Drone-based photogrammetry combined with deep learning to estimate hail size distributions and melting of hail on the ground
Martin Lainer, Killian P. Brennan, Alessandro Hering, Jérôme Kopp, Samuel Monhart, Daniel Wolfensberger, and Urs Germann
Atmos. Meas. Tech., 17, 2539–2557, https://doi.org/10.5194/amt-17-2539-2024, 2024
This study uses deep learning (the Mask R-CNN model) on drone-based photogrammetric data of hail on the ground to estimate hail size distributions (HSDs). Traditional hail sensors' limited areas complicate the full HSD retrieval. The HSD of a supercell event on 20 June 2021 is retrieved and contains > 18 000 hailstones. The HSD is compared to automatic hail sensor measurements and those of weather-radar-based MESHS. Investigations into ground hail melting are performed by five drone flights.

Mid-Atlantic Nocturnal Low-Level Jet Characteristics: A machine learning analysis of radar wind profiles
Maurice Roots, John T. Sullivan, and Belay Demoz
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-37,2024
Preprint under review for AMT (discussion: open, 0 comments)
This paper introduces a machine-learning approach to automatically isolate Nocturnal Low-Level Jets (NLLJs) using observations from Maryland’s Radar Wind Profiler (RWP) network. Initial findings identify 90 south-westerly NLLJs from May to September 2017–2021, showcasing core parameters and jet morphology. The research aims to establish a foundation for understanding the formation mechanisms of Mid-Atlantic NLLJs and their impact on air quality.

A global perspective on CO2 satellite observations in high AOD conditions
Timo H. Virtanen, Anu-Maija Sundström, Elli Suhonen, Antti Lipponen, Antti Arola, Christopher O'Dell, Robert R. Nelson, and Hannakaisa Lindqvist
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-77,2024
Preprint under review for AMT (discussion: open, 0 comments)
We find that small particles suspended in the air (aerosols) affect the satellite observations of carbon dioxide (CO2) made by the Orbiting Carbon Observatory -2 satellite instrument. The satellite estimates of CO2 appear too high for clean areas and too low for polluted areas. Our results show that the CO2 and aerosols are often co-emitted, and this is partly masked out in the current retrievals. Correctly accounting for the aerosol effect is important for CO2 emission estimates by satellites.

The Far-INfrarEd Spectrometer for Surface Emissivity (FINESSE) Part II: First measurements of the emissivity of water in the far-infrared
Laura Warwick, Jonathan Murray, and Helen Brindley
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-21,2024
Preprint under review for AMT (discussion: open, 0 comments)
We describe a method for measuring the emissivity of natural surfaces using data from the new 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.

The ALOMAR Rayleigh/Mie/Raman lidar: status after 30 years of operation
Jens Fiedler and Gerd Baumgarten
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-31,2024
Preprint under review for AMT (discussion: open, 0 comments)
This article describes the current status of a lidar installed in the ALOMAR observatory in Northern Norway. It investigates the Arctic middle atmosphere on a climatological basis since 30 years. We discuss major upgrades of the system implemented during recent years, including methods for reliable remote operation of this complex lidar. We also show examples that illustrate the performance of the lidar during measurements at different altitude ranges and time scales.

Characterization of dust aerosols from ALADIN and CALIOP measurements
Rui Song, Adam Povey, and Roy G. Grainger
Atmos. Meas. Tech., 17, 2521–2538, https://doi.org/10.5194/amt-17-2521-2024, 2024
In our study, we explored aerosols, tiny atmospheric particles affecting the Earth's climate. Using data from two lidar-equipped satellites, ALADIN and CALIOP, we examined a 2020 Saharan dust event. The newer ALADIN's results aligned with CALIOP's. By merging their data, we corrected CALIOP's discrepancies, enhancing the dust event depiction. This underscores the significance of advanced satellite instruments in aerosol research. Our findings pave the way for upcoming satellite missions.

The Far INfrarEd Spectrometer for Surface Emissivity (FINESSE). Part 1: Instrument description and level 1 radiances
Jonathan Ernest Murray, Laura Warwick, Helen Brindley, Alan Last, Patrick Quigley, Andy Rochester, Alexander Dewar, and Daniel Cummins
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-22,2024
Preprint under review for AMT (discussion: open, 0 comments)
We introduce a new instrument, FINESSE, designed to measure the ability of natural surfaces to emit infrared radiation. FINESSE combines a commercial instrument with custom-built optics which allow it to view a surface from different angles and obtain 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 characterise FINESSE’s uncertainty budget and provide examples of its measurement capability

Producing aerosol size distributions consistent with optical particle counters measurements using space-based measurements of aerosol extinction coefficient
Nicholas Ernest, Larry W. Thomason, and Terry Deshler
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-62,2024
Preprint under review for AMT (discussion: open, 0 comments)
We use balloon-borne measurements of aerosol size distribution (ASD) made by the University of Wyoming (UW) to derive distributions which are representative of the ASDs that underlie measurements made by the Stratospheric Aerosol and Gas Experiment II (SAGE II). A simple single mode log-normal distribution has in the past been used to derive ASD from SAGE II data; here we derive bimodal log-normal distributions. Reproducing median aerosol properties, however sometimes with wide variance.

An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production
Johan Mellqvist, Nathalia T. Vechi, Charlotte Scheutz, Marc Durif, Francois Gautier, John Johansson, Jerker Samuelsson, Brian Offerle, and Samuel Brohede
Atmos. Meas. Tech., 17, 2465–2479, https://doi.org/10.5194/amt-17-2465-2024, 2024
The solar occultation flux method retrieves ammonia gas columns from the solar spectrum. Emissions are obtained by multiplying the integrated plume concentration by the wind speed profile. The methodology for uncertainty estimation was established considering an error budget with systematic and random components, resulting in an expanded uncertainty in the range of 20 % to 30 %. The method was validated in a controlled release, and its application was demonstrated in different farms.

Large-scale automated emission measurement of individual vehicles with point sampling
Markus Knoll, Martin Penz, Hannes Juchem, Christina Schmidt, Denis Pöhler, and Alexander Bergmann
Atmos. Meas. Tech., 17, 2481–2505, https://doi.org/10.5194/amt-17-2481-2024, 2024
Exhaust emissions from combustion-based vehicles are negatively affecting human health and our environment. In particular, a small share (< 20 %) of poorly maintained or tampered vehicles are responsible for the majority (60 %–90 %) of traffic-related emissions. The emissions from vehicles are currently not properly monitored during their lifetime. We present a roadside measurement technique, called point sampling, which can be used to monitor vehicle emissions throughout their life cycle.

Application of Doppler sodar in short-term forecasting of PM10 concentration in the air in Krakow (Poland)
Ewa Agnieszka Krajny, Leszek Ośródka, and Marek Jan Wojtylak
Atmos. Meas. Tech., 17, 2451–2464, https://doi.org/10.5194/amt-17-2451-2024, 2024
The use of sodar data to support an air quality forecasting system is encouraging. The sodar model is a complement to forecasting methods because it is useful due to its simplicity and speed of calculations. It does not require emission data, for which it is difficult to quickly verify temporal and spatial variability. The use of simple formulas of regression models in forecasting, while maintaining their multivariate nature, facilitates the optimisation of the prediction process.

Assessment of the spectral misalignment effect (SMILE) on EarthCARE's Multi-Spectral Imager aerosol and cloud property retrievals
Nicole Docter, Anja Hünerbein, David P. Donovan, Rene Preusker, Jürgen Fischer, Jan Fokke Meirink, Piet Stammes, and Michael Eisinger
Atmos. Meas. Tech., 17, 2507–2519, https://doi.org/10.5194/amt-17-2507-2024, 2024
MSI is the imaging spectrometer on board EarthCARE and will provide across-track information on clouds and aerosol properties. The MSI solar channels exhibit a spectral misalignment effect (SMILE) in the measurements. This paper describes and evaluates how the SMILE will affect the cloud and aerosol retrievals that do not account for it.

Validation of Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) chlorodifluoromethane (HCFC-22) in the upper troposphere and lower stratosphere
Felicia Kolonjari, Patrick E. Sheese, Kaley A. Walker, Chris D. Boone, David A. Plummer, Andreas Engel, Stephen A. Montzka, David E. Oram, Tanja Schuck, Gabriele P. Stiller, and Geoffrey C. Toon
Atmos. Meas. Tech., 17, 2429–2449, https://doi.org/10.5194/amt-17-2429-2024, 2024
The Canadian Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) satellite instrument is currently providing the only vertically resolved chlorodifluoromethane (HCFC-22) measurements from space. This study assesses the most current ACE-FTS HCFC-22 data product in the upper troposphere and lower stratosphere, as well as modelled HCFC-22 from a 39-year run of the Canadian Middle Atmosphere Model (CMAM39) in the same region.

Response of protonated, adduct, and fragmented ions in Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS)
Fangbing Li, Dan Dan Huang, Linhui Tian, Bin Yuan, Wen Tan, Liang Zhu, Penglin Ye, Douglas Worsnop, Ka In Hoi, Kai Meng Mok, and Yong Jie Li
Atmos. Meas. Tech., 17, 2415–2427, https://doi.org/10.5194/amt-17-2415-2024, 2024
The responses of protonated, adduct, and fragmented ions of 21 volatile organic compounds (VOCs) were investigated with varying instrument settings and relative humidity (RH) in a Vocus proton-transfer-reaction mass spectrometer (PTR-MS). The protonated ions of most VOCs studied show < 15 % variation in sensitivity, except for some long-chain aldehydes. The relationship between sensitivity and PTR rate constant is complicated by the influences from ion transmission and protonated ion fraction.

Quantifying functional group compositions of household fuel-burning emissions
Emily Y. Li, Amir Yazdani, Ann M. Dillner, Guofeng Shen, Wyatt M. Champion, James J. Jetter, William T. Preston, Lynn M. Russell, Michael D. Hays, and Satoshi Takahama
Atmos. Meas. Tech., 17, 2401–2413, https://doi.org/10.5194/amt-17-2401-2024, 2024
Infrared spectroscopy is a cost-effective measurement technique to characterize the chemical composition of organic aerosol emissions. This technique differentiates the organic matter emission factor from different fuel sources by their characteristic functional groups. Comparison with collocated measurements suggests that polycyclic aromatic hydrocarbon concentrations in emissions estimated by conventional chromatography may be substantially underestimated.

Cancellation of cloud shadow effects in the absorbing aerosol index retrieval algorithm of TROPOMI
Victor J. H. Trees, Ping Wang, Piet Stammes, Lieuwe G. Tilstra, David P. Donovan, and A. Pier Siebesma
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-40,2024
Preprint under review for AMT (discussion: open, 0 comments)
Our study investigates the impact of cloud shadows on satellite-based aerosol index measurements over Europe by TROPOMI. Using a cloud shadow detection algorithm and simulations, we found that the overall effect on the aerosol index is minimal. Interestingly, we measured that cloud shadows are significantly bluer than their shadow-free surroundings, but the traditional algorithm already (partly) automatically corrects for this increased blueness.

Investigation of cirrus cloud properties in the tropical tropopause layer using high-altitude limb-scanning near-IR spectroscopy during NASA-ATTREX
Santo Fedele Colosimo, Nathaniel Brockway, Vijay Natraj, Robert Spurr, Klaus Pfeilsticker, Lisa Scalone, Max Spolaor, Sarah Woods, and Jochen Stutz
Atmos. Meas. Tech., 17, 2367–2385, https://doi.org/10.5194/amt-17-2367-2024, 2024
Cirrus clouds are poorly understood components of the climate system, in part due to the challenge of observing thin, sub-visible ice clouds. We address this issue with a new observational approach that uses the remote sensing of near-infrared ice water absorption features from a high-altitude aircraft. We describe the underlying principle of this approach and present a new procedure to retrieve ice concentration in cirrus clouds. Our retrievals compare well with in situ observations.

Identifying the seeding signature in cloud particles from hydrometeor residuals
Mahen Konwar, Benjamin Werden, Edward C. Fortner, Sudarsan Bera, Mercy Varghese, Subharthi Chowdhuri, Kurt Hibert, Philip Croteau, John Jayne, Manjula Canagaratna, Neelam Malap, Sandeep Jayakumar, Shivsai A. Dixit, Palani Murugavel, Duncan Axisa, Darrel Baumgardner, Peter F. DeCarlo, Doug R. Worsnop, and Thara Prabhakaran
Atmos. Meas. Tech., 17, 2387–2400, https://doi.org/10.5194/amt-17-2387-2024, 2024
In a warm cloud seeding experiment hygroscopic particles are released to alter cloud processes to induce early raindrops. During the Cloud–Aerosol Interaction and Precipitation Enhancement Experiment, airborne mini aerosol mass spectrometers analyse the particles on which clouds form. The seeded clouds showed higher concentrations of chlorine and potassium, the oxidizing agents of flares. Small cloud droplet concentrations increased, and seeding particles were detected in deep cloud depths.

Hailstorm events in the Central Andes of Peru: insights from historical data and radar microphysics
Jairo M. Valdivia, José Luis Flores-Rojas, Josep J. Prado, David Guizado, Elver Villalobos-Puma, Stephany Callañaupa, and Yamina Silva-Vidal
Atmos. Meas. Tech., 17, 2295–2316, https://doi.org/10.5194/amt-17-2295-2024, 2024
In this study, we explored hailstorms in the Central Andes of Peru. We used historical records and radar measurements to understand the frequency, timing, and characteristics of these hail events. Our research found a trend of decreasing hail frequency, probably due to anthropogenic climate change. Understanding these weather patterns is critical for local communities, as it can help improve weather forecasts and manage risks related to these potentially destructive events.