Electrochemical Concentration Cell Research Articles

Consistency evaluation of tropospheric ozone from ozonesonde and IAGOS (In-service Aircraft for a Global Observing System) observations: vertical distribution, ozonesonde types, and station–airport distance

Abstract. The vertical distribution of tropospheric O3 from ozonesondes is compared with that from In-service Aircraft for a Global Observing System (IAGOS) measurements collected at 23 pairs of sites between about 30° S and 55° N from 1995 to 2021. Profiles of tropospheric O3 from IAGOS are generally in good agreement with ozonesonde observations from electrochemical concentration cells (ECCs), Brewer–Mast sondes, and carbon–iodine sensors, with average biases of 2.58, −0.28, and 0.67 ppb and correlation coefficients (R) of 0.72, 0.82, and 0.66, respectively. Agreement between aircraft and Indian-sonde observations is poor, with an average bias of 15.32 ppb and an R value of 0.44. The O3 concentration observed by ECC sondes is, on average, 5 %–10 % higher than that observed by IAGOS, and the relative bias increases modestly with altitude. For other sonde types, there are some seasonal and altitudinal variations in the relative bias with respect to the IAGOS measurements, but these appear to be caused by local differences. The distance between the station and airport, when within 4° (latitude and longitude), has little effect on the comparison results. For the ECC ozonesondes, the overall bias with respect to the IAGOS measurements varies from 5.7 to 9.8 ppb when the station pairs are grouped by station–airport distances of <1° (latitude and longitude), 1–2°, and 2–4°. Correlations for these groups correspond to R=0.8, 0.9, and 0.7. These comparison results provide important information for merging ozonesonde and IAGOS measurement datasets. They can also be used to evaluate the relative biases of different sonde types in the troposphere, using the aircraft as a transfer standard.

Measurement report: The Palau Atmospheric Observatory and its ozonesonde record – continuous monitoring of tropospheric composition and dynamics in the tropical western Pacific

Abstract. The tropical western Pacific is recognized as an important region for stratosphere–troposphere exchange but lies in a data-sparse location that had a measurement gap in the global ozone sounding network. The Palau Atmospheric Observatory (PAO, approx. 7.3∘ N, 134.5∘ E) was established to study the atmospheric composition above the remote tropical western Pacific with a comprehensive instrumental setup. Since 2016, two laboratory containers in Palau host a Fourier transform infrared spectrometer; a lidar (micro-lidar until 2016, cloud and aerosol lidar from 2018); a Pandora 2S photometer; and laboratory space for weather balloon soundings with ozone, water vapor, aerosol, and radiosondes. In this analysis, we focus on the continuous, fortnightly ozone sounding program with electrochemical concentration cell (ECC) ozonesondes. The aim of this study is to introduce the PAO and its research potential, present the first observation of the typical seasonal cycle of tropospheric ozone in the tropical western Pacific based on a multiannual record of in situ observations, and investigate major drivers of variability and seasonal variation from January 2016 until December 2021​​​​​​​ related to the large-scale atmospheric circulation. We present the PAO ozone (O3) volume mixing ratios (VMR) and relative humidity (RH) time series complemented by other observations. The site is exposed to year-round high convective activity reflected in dominating low O3 VMR and high RH. In 2016, the impact of the strong El Niño is evident as a particularly dry, ozone-rich episode. The main modulator of annual tropospheric O3 variability is identified as the movement of the Intertropical Convergence Zone (ITCZ), with the lowest O3 VMR in the free troposphere during the ITCZ position north of Palau. An analysis of the relation of O3 and RH for the PAO and selected sites from the Southern Hemispheric Additional Ozonesondes (SHADOZ) network reveals three different regimes. Palau's O3 / RH distribution resembles the one in Fiji, Java and American Samoa but is unique in its seasonality and its comparably narrow Gaussian distribution around low O3 VMR and the evenly distributed RH. A previously found bimodal distribution of O3 VMR and RH could not be seen for the full Palau record but only during specific seasons and years. Due to its unique remote location, Palau is an ideal atmospheric background site to detect changes in air dynamics imprinted on the chemical composition of the tropospheric column. The efforts to establish, run and maintain the PAO have succeeded to fill an observational gap in the remote tropical western Pacific and give good prospects for ongoing operations. The ECC sonde record will be integrated into the SHADOZ database in the near future.

A Self-Charging Concentration Cell: Theory

Batteries are a key resource in the quest for sustainable energy. Here, the theoretical basis is presented for a new type of electrochemical concentration cell that might contribute to this enterprise. The cell, which has been successfully demonstrated in the laboratory, incorporates a chemically asymmetric membrane to drive anisotropic diffusion between two solution chambers; the resulting concentration difference powers the cell. In this study, the membrane’s operation is validated via three theoretical approaches: (i) traditional equilibrium thermodynamics; (ii) balancing drift and diffusion current densities; and (iii) the time-independent diffusion equation. The physical criteria for its operation are developed and its dimensionless variables identified. The cell’s maximum instantaneous power density might exceed 107 W/m3. Its self-charging capability should confer multiple advantages over traditional concentration cells (as well as over some voltaics), including improved thermodynamic efficiency, economy, and compactness. Commonalities with other electrochemical systems (e.g., liquid chromatography, metal corrosion, and solid state diodes) are discussed, and a physical instantiation of the cell is reviewed. Recent numerical simulations corroborate its essential processes.

Development of an automated pump-efficiency measuring system for ozonesondes utilizing an airbag-type flowmeter

Abstract. We report here on a system developed to automatically measure the flow rate characteristics (i.e., the pump efficiency) of pumps on ozonesondes under various pressure levels simulating upper-air conditions. The system consists of a flow measurement unit incorporating a polyethylene airbag, a pressure control unit that reproduces low-pressure environmental conditions, and a control unit that integrates and controls these elements to enable fully automatic measurement. The Japan Meteorological Agency (JMA) has operationally measured pump efficiency for electrochemical concentration cell (ECC) ozonesondes using the system since 2009, resulting in a significant amount of related data. Extensive measurements collected for the same ozonesonde pump over a period of around 12 years indicate the long-term stability of the system's performance. These long-term data also show that ozonesonde pump flow characteristics differed among production lots. Evaluation of the impacts of variance in these characteristics on observed ozone concentration data indicated that the influence on total ozone estimation was up to approximately 4 %, the standard deviation per lot was approximately 1 %, and the standard deviation among lots was approximately 0.6 %.

Water Vapor in the Upper Troposphere above Syowa Station in the Antarctic: Its Variations and Causes

An intensive balloon-borne observation was performed at Syowa Station in the Antarctic (69.0°S, 39.6°E) in July 2016 using Cryogenic Frostpoint Hygrometers (CFH) and Electrochemical Concentration Cell (ECC) ozonesondes. High water vapor concentration was observed in the upper troposphere in two out of five observations. Trajectory analysis and atmospheric reanalysis data showed that moist air was transported into the upper troposphere due to the upwelling in front of a trough. While only isentropic transport was dominant in one case, both the isentropic transport and diabatic heating contributed to the upward transport in the other case. In another case where the air parcels came over the Antarctic continent, the water vapor concentration in the upper troposphere was lower than in the other cases. These results suggest that transport of air parcels with different origins by synoptic-scale disturbances controls water vapor concentration in the Antarctic upper troposphere.

Effect of Synoptic‐Scale Dynamics on the Vertical Distribution of Tropospheric Ozone Over the Arabian Sea and the Indian Ocean During the Boreal Winter of 2018

AbstractOzone (O3) and relative humidity profiles obtained from in situ electrochemical concentration cell ozonesonde‐radiosonde observations over the Arabian Sea and the Indian Ocean from 16 January to 14 February 2018 during the Integrated Campaign for Aerosols gases and Radiation Budget cruise were analyzed. On the basis of the prevailing synoptic conditions during the cruise period, the cruise track was divided into three legs which were studied separately. The main objective of this study was to investigate the influence of prevailing synoptic scale dynamics and transport on the vertical distribution of ozone in the troposphere, especially in the tropical tropopause layer (TTL) region. Tropospheric ozone exhibits pronounced latitude variations over the Arabian Sea and the Indian Ocean with very high values (∼60–70 ppbv) above the marine boundary layer near the Indian landmass. Distinct ozone‐rich plume‐like structures are observed in the free troposphere around 1–3 and 4–5 km. At around 1–3 km, the ozone plume was maintained by the continental outflows from the Indian sub‐continent. The mid‐tropospheric (4–5 km) high ozone‐low water vapor layer is hypothesized to be associated with the equatorward return flow of the Hadley circulation. Enhanced (declined) ozone is observed below 12 km altitude in the descending (ascending) branch of Hadley circulation. The ozone distribution in the TTL shows distinct structures associated with the prevailing synoptic dynamics and transport during respective legs. Evidences of stratospheric intrusion and air mass transport from biomass burning locations are seen regarding upper tropospheric ozone enhancements.

An Examination of the Recent Stability of Ozonesonde Global Network Data

AbstractThe recent Assessment of Standard Operating Procedures for Ozonesondes 2.0 (WMO/GAW Report #268) addressed questions of homogeneity and long‐term stability in global electrochemical concentration cell (ECC) ozone sounding network time series. Among its recommendations was adoption of a standard for evaluating data quality in ozonesonde time series. Total column ozone (TCO) derived from the sondes compared to TCO from Aura's Ozone Monitoring Instrument (OMI) is a primary quality indicator. Comparisons of sonde ozone with Aura's Microwave Limb Sounder (MLS) are used to assess the stability of stratospheric ozone. This paper provides a comprehensive examination of global ozonesonde network data stability and accuracy since 2004 in light of the sudden post‐2013 TCO “dropoff” of ∼3%–4% that was reported previously at select stations (Stauffer et al., 2020, https://doi.org/10.1029/2019GL086791). Comparisons with Aura OMI TCO averaged across the network of 60 stations are stable within about ±2% over the past 18 years. Sonde TCO has similar stability compared to three other TCO satellite instruments, and the stratospheric ozone measurements average to within ±5% of MLS from 50 to 10 hPa. Thus, sonde data are reliable for trends, but with a caveat applied for a subset of dropoff stations in the tropics and subtropics. The dropoff is associated with only one of two major ECC instrument types. A detailed examination of ECC serial numbers pinpoints the timing of the dropoff. However, we find that overall, ozonesonde data are stable and accurate compared to independent measurements over the past two decades.

Analysis of Vertical Distribution of Ozone in Winter and Its Transport from Stratosphere to Troposphere in the Pearl River Delta Region of China

The vertical distribution of winter ozone in the Pearl River Delta in 2021 was analyzed using electrochemical concentration cell (ECC) ozonesonde and compared with the ozone Light detection and ranging (LiDAR) data. The transport of stratospheric ozone to the troposphere was also explored. The results show that (1) the maximum value of the stratospheric ozone layer was about 25 km. The stratospheric ozone profile is mainly unimodal, and the stratospheric ozone content was much higher than that of the troposphere. In the troposphere, the ozone content near the ground (0-2 km) was slightly higher than that between 5 and 15 km. The ozone profile in the upper and middle troposphere showed a peak structure, which was mainly divided into single peak (22%) and multipeak (77%) profiles. (2) In the middle and lower troposphere, the vertical profile of ozone detected by LiDAR is significantly different from that detected by sounding system. The difference between the two ranged from 10 ppb to 60 ppb at the same height. Ozone sounding can supplement the blind area of the near-ground layer by LiDAR ozone detection and can calibrate the inversion results of LiDAR. (3) On January 5, 2022, stratospheric ozone was transported to the troposphere. The stratospheric intrusion occurred due the high wind speed of the subtropical jet centre over Qingyuan and due to strong subsidence movement. When the stratospheric air mass moved to the troposphere, and subsidence airflow encountered, the ozone concentration near the ground was rapidly increased in a short time. It was identified as an “exceptional event.”

Impact of instrumental line shape characterization on ozone monitoring by FTIR spectrometry

Abstract. Retrieving high-precision concentrations of atmospheric trace gases from FTIR (Fourier transform infrared) spectrometry requires a precise knowledge of the instrumental performance. In this context, this paper examines the impact on the ozone (O3) retrievals of several approaches used to characterize the instrumental line shape (ILS) function of ground-based FTIR spectrometers within NDACC (Network for the Detection of Atmospheric Composition Change). The analysis has been carried out at the subtropical Izaña Observatory (IZO, Spain) by using the 20-year time series of the high-resolution FTIR solar absorption spectra acquired between 1999 and 2018. The theoretical quality assessment and the comparison to independent O3 observations available at IZO (Brewer O3 total columns and electrochemical concentration cell, ECC, sondes) reveal consistent findings. The inclusion of a simultaneous retrieval of the ILS parameters in the O3 retrieval strategy allows, on the one hand, a rough instrumental characterization to be obtained and, on the other hand, the precision of the FTIR O3 products to be slightly improved. The improvement is of special relevance above the lower stratosphere, where the cross-interference between the O3 vertical distribution and the instrumental performance is more significant. However, it has been found that the simultaneous ILS retrieval leads to a misinterpretation of the O3 variations on daily and seasonal scales. Therefore, in order to ensure the independence of the O3 retrievals and the instrumental response, the optimal approach to deal with the FTIR instrumental characterization is found to be the continuous monitoring of the ILS function by means of independent observations, such as gas cell measurements.

Homogenization of the Observatoire de Haute Provence electrochemical concentration cell (ECC) ozonesonde data record: comparison with lidar and satellite observations

Abstract. The Observatoire de Haute Provence (OHP) weekly electrochemical concentration cell (ECC) ozonesonde data have been homogenized for the period 1991–2021 according to the recommendations of the Ozonesonde Data Quality Assessment (O3S-DQA) panel. The assessment of the ECC homogenization benefit has been carried out using comparisons with other ozone-measuring ground-based instruments at the same station (lidar, surface measurements) and with colocated satellite observations of the O3 vertical profile by Microwave Limb Sounder (MLS). The major differences between uncorrected and homogenized ECC data are related to a change of ozonesonde type in 1997, removal of the pressure dependency of the ECC background current and correction of internal pump temperature. The original 3–4 ppbv positive bias between ECC and lidar in the troposphere is corrected with the homogenization. The ECC 30-year trends of the seasonally adjusted ozone concentrations are also significantly improved in both the troposphere and the stratosphere after the ECC homogenization, as shown by the ECC/lidar or ECC/surface ozone trend comparisons. A −0.19 % yr−1 negative trend of the normalization factor (NT) calculated using independent measurements of the total ozone column (TOC) at OHP disappears after homogenization of the ECC data. There is, however, a remaining −3.7 % negative bias in the TOC which is likely related to an underestimate of the ECC concentrations in the stratosphere above 50 hPa. Differences between TOC measured by homogenized ECC and satellite observations show a smaller bias of −1 %. Comparisons between homogenized ECC and OHP stratospheric lidar and MLS observations below 26 km are slightly negative (−2 %) or positive (+2 %), respectively. The comparisons with both lidar and satellite observations suggest that homogenization increases the negative bias of the ECC to values lower than −6 % above 28 km. The reason for this bias is still unclear, but a possible explanation might be related to freezing or evaporation of the sonde solution in the stratosphere.

Improved ozone monitoring by ground-based FTIR spectrometry

Abstract. Accurate observations of atmospheric ozone (O3) are essential to monitor in detail its key role in atmospheric chemistry. The present paper examines the performance of different O3 retrieval strategies from FTIR (Fourier transform infrared) spectrometry by using the 20-year time series of the high-resolution solar spectra acquired from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain) within NDACC (Network for the Detection of Atmospheric Composition Change). In particular, the effects of two of the most influential factors have been investigated: the inclusion of a simultaneous atmospheric temperature profile fit and the spectral O3 absorption lines used for the retrievals (the broad spectral region of 1000–1005 cm−1 and single micro-windows between 991 and 1014 cm−1). Additionally, the water vapour (H2O) interference in O3 retrievals has been evaluated, with the aim of providing an improved O3 strategy that minimises its impact and, therefore, could be applied at any NDACC FTIR station under different humidity conditions. The theoretical and experimental quality assessments of the different FTIR O3 products (total column (TC) amounts and volume mixing ratio (VMR) profiles) provide consistent results. Combining a simultaneous temperature retrieval with the optimal selection of single O3 micro-windows results in superior FTIR O3 products, with a precision of better than 0.6 %–0.7 % for O3 TCs as compared to coincident NDACC Brewer observations taken as a reference. However, this improvement can only be achieved provided the FTIR spectrometer is properly characterised and stable over time. For unstable instruments, the temperature fit is found to exhibit a strong negative influence on O3 retrievals due to the increase in the cross-interference between the temperature retrieval and instrumental performance (given by the instrumental line shape function and measurement noise), which leads to a worsening of the precision of FTIR O3 TCs of up to 2 %. This cross-interference becomes especially noticeable beyond the upper troposphere/lower stratosphere, as documented theoretically as well as experimentally by comparing FTIR O3 profiles to those measured using electrochemical concentration cell (ECC) sondes within NDACC. Consequently, it should be taken into account for the reliable monitoring of the O3 vertical distribution, especially over long-term timescales.

Fifty years of balloon-borne ozone profile measurements at Uccle, Belgium: a short history, the scientific relevance, and the achievements in understanding the vertical ozone distribution

Abstract. Starting in 1969 and comprising three launches a week, the Uccle (Brussels, Belgium) ozonesonde dataset is one of longest and densest in the world. Moreover, as the only major change was the switch from Brewer-Mast (BM) to electrochemical concentration cell (ECC) ozonesonde types in 1997 (when the emissions of ozone-depleting substances peaked), the Uccle time series is very homogenous. In this paper, we briefly describe the efforts that were undertaken during the first 3 decades of the 50 years of ozonesonde observations to guarantee the homogeneity between ascent and descent profiles, under changing environmental conditions (e.g. SO2), and between the different ozonesonde types. This paper focuses on the 50-year-long Uccle ozonesonde dataset and aims to demonstrate its past, present, and future relevance to ozone research in two application areas: (i) the assessment of the temporal evolution of ozone from the surface to the (middle) stratosphere, and (ii) as the backbone for validation and stability analysis of both stratospheric and tropospheric satellite ozone retrievals. Using the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) multiple linear regression model (SPARC/IO3C/GAW, 2019), we found that the stratospheric ozone concentrations at Uccle have declined at a significant rate of around 2 % per decade since 1969, which is also rather consistent over the different stratospheric levels. This overall decrease can mainly be assigned to the 1969–1996 period with a rather consistent rate of decrease of around −4 % per decade. Since 2000, a recovery of between +1 % per decade and +3 % per decade of the stratospheric ozone levels above Uccle has been observed, although it is not significant and is not seen for the upper stratospheric levels measured by ozonesondes. Throughout the entire free troposphere, a very consistent increase in the ozone concentrations of 2 % per decade to 3 % per decade has been measured since both 1969 and 1995, with the trend since 1995 being in almost perfect agreement with the trends derived from the In-service Aircraft for a Global Observing System (IAGOS) ascent/descent profiles at Frankfurt. As the number of tropopause folding events in the Uccle time series has increased significantly over time, increased stratosphere-to-troposphere transport of recovering stratospheric ozone might partly explain these increasing tropospheric ozone concentrations, despite the levelling-off of (tropospheric) ozone precursor emissions and notwithstanding the continued increase in mean surface ozone concentrations. Furthermore, we illustrate the crucial role of ozonesonde measurements for the validation of satellite ozone profile retrievals. With the operational validation of the Global Ozone Monitoring Experiment-2 (GOME-2), we show how the Uccle dataset can be used to evaluate the performance of a degradation correction for the MetOp-A/GOME-2 UV (ultraviolet) sensors. In another example, we illustrate that the Microwave Limb Sounder (MLS) overpass ozone profiles in the stratosphere agree within ±5 % with the Uccle ozone profiles between 10 and 70 hPa. Another instrument on the same Aura satellite platform, the Tropospheric Emission Spectrometer (TES), is generally positively biased with respect to the Uccle ozonesondes in the troposphere by up to ∼ 10 ppbv, corresponding to relative differences of up to ∼ 15 %. Using the Uccle ozonesonde time series as a reference, we also demonstrate that the temporal stability of those last two satellite retrievals is excellent.

A new method to correct the electrochemical concentration cell (ECC) ozonesonde time response and its implications for “background current” and pump efficiency

Abstract. The electrochemical concentration cell (ECC) ozonesonde has been the main instrument for in situ profiling of ozone worldwide; yet, some details of its operation, which contribute to the ozone uncertainty budget, are not well understood. Here, we investigate the time response of the chemical reactions inside the ECC and how corrections can be used to remove some systematic biases. The analysis is based on the understanding that two reaction pathways involving ozone occur inside the ECC that generate electrical currents on two very different timescales. The main fast-reaction pathway with a time constant of about 20 s is due the conversion of iodide to molecular iodine and the generation of two free electrons per ozone molecule. A secondary slow-reaction pathway involving the buffer generates an excess current of about 2 %–10 % with a time constant of about 25 min. This excess current can be interpreted as what has conventionally been considered the “background current”. This contribution can be calculated and removed from the measured current instead of the background current. Here we provide an algorithm to calculate and remove the contribution of the slow-reaction pathway and to correct for the time lag of the fast-reaction pathway. This processing algorithm has been applied to ozonesonde profiles at Costa Rica and during the Central Equatorial Pacific Experiment (CEPEX) as well as to laboratory experiments evaluating the performance of ECC ozonesondes. At Costa Rica, where a 1 % KI, 1/10th buffer solution is used, there is no change in the derived total ozone column; however, in the upper troposphere and lower stratosphere, average reported ozone concentrations increase by up to 7 % and above 30 km decrease by up to 7 %. During CEPEX, where a 1 % KI, full-buffer solution was used, ozone concentrations are increased mostly in the upper troposphere, with no change near the top of the profile. In the laboratory measurements, the processing algorithms have been applied to measurements using the majority of current sensing solutions and using only the stronger pump efficiency correction reported by Johnson et al. (2002). This improves the accuracy of the ECC sonde ozone profiles, especially for low ozone concentrations or large ozone gradients and removes systematic biases relative to the reference instruments. In the surface layer, operational procedures prior to launch, in particular the use of filters, influence how typical gradients above the surface are detected. The correction algorithm may report gradients that are steeper than originally reported, but their uncertainty is strongly influenced by the prelaunch procedures.

A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation

Abstract. The MetOp/Infrared Atmospheric Sounding Interferometer (IASI) instruments have provided data for operational meteorology and document atmospheric composition since 2007. IASI ozone (O3) data have been used extensively to characterize the seasonal and interannual variabilities and the evolution of tropospheric O3 at the global scale. SOftware for a Fast Retrieval of IASI Data (SOFRID) is a fast retrieval algorithm that provides IASI O3 profiles for the whole IASI period. Until now, SOFRID O3 retrievals (v1.5 and v1.6) were performed with a single a priori profile, which resulted in important biases and probably a too-low variability. For the first time, we have implemented a comprehensive dynamical a priori profile for spaceborne O3 retrievals which takes the pixel location, time and tropopause height into account for SOFRID-O3 v3.5 retrievals. In the present study, we validate SOFRID-O3 v1.6 and v3.5 with electrochemical concentration cell (ECC) ozonesonde profiles from the global World Ozone and Ultraviolet Radiation Data Centre (WOUDC) database for the 2008–2017 period. Our validation is based on a thorough statistical analysis using Taylor diagrams. Furthermore, we compare our retrievals with ozonesonde profiles both smoothed by the IASI averaging kernels and raw. This methodology is essential to evaluate the inherent usefulness of the retrievals to assess O3 variability and trends. The use of a dynamical a priori profile largely improves the retrievals concerning two main aspects: (i) it corrects high biases for low-tropospheric O3 regions such as the Southern Hemisphere, and (ii) it increases the retrieved O3 variability, leading to a better agreement with ozonesonde data. Concerning upper troposphere–lower stratosphere (UTLS) and stratospheric O3, the improvements are less important and the biases are very similar for both versions. The SOFRID tropospheric ozone columns (TOCs) display no significant drifts (<2.5 %) for the Northern Hemisphere and significant negative ones (9.5 % for v1.6 and 4.3 % for v3.5) for the Southern Hemisphere. We have compared our validation results to those of the Fast Optimal Retrievals on Layers for IASI (FORLI) retrieval software from the literature for smoothed ozonesonde data only. This comparison highlights three main differences: (i) FORLI retrievals contain more theoretical information about tropospheric O3 than SOFRID; (ii) root mean square differences (RMSDs) are smaller and correlation coefficients are higher for SOFRID than for FORLI; (iii) in the Northern Hemisphere, the 2010 jump detected in FORLI TOCs is not present in SOFRID.

Study on calculation and validation of tropospheric ozone by ozone monitoring instrument – microwave limb sounder over China

ABSTRACT Tropospheric ozone plays an important role in atmospheric processes. However, the acquisition of tropospheric ozone content from satellite observations is a crucial challenge for atmospheric pollution research. In this study, the 0.25° × 0.25° tropospheric ozone column products over China were determined from total ozone columns measured by the Ozone Monitoring Instrument (OMI) and ozone profiler of the Microwave Limb Sounder (MLS). Calculation results were then validated with similar satellite products, Electrochemical Concentration Cell (ECC) ozonesonde observations, and simulation results from the Regional Atmospheric Modelling System – Community Multiscale Air Quality Model (RAMS-CMAQ). Validations shows that OMI-MLS calculation results correlate well with ozonesonde data, the correlation coefficient reached to 0.92. Compared to RAMS-CMAQ, OMI-MLS presents consistent distribution and the correlation coefficients range from 0.52 to 0.82.

A Post‐2013 Dropoff in Total Ozone at a Third of Global Ozonesonde Stations: Electrochemical Concentration Cell Instrument Artifacts?

AbstractAn international effort to improve ozonesonde data quality and to reevaluate historical records has made significant improvements in the accuracy of global network data. However, between 2014 and 2016, ozonesonde total column ozone (TCO; O3) at 14 of 37 regularly reporting stations exhibited a sudden dropoff relative to satellite measurements. The ozonesonde TCO drop is 3–7% compared to satellite and ground‐based TCO, and 5–10% or more compared to satellite stratospheric O3 profiles, compromising the use of recent data for trends, although they remain reliable for other uses. Hardware changes in the ozonesonde instrument are likely a major factor in the O3 dropoff, but no single property of the ozonesonde explains the findings. The bias remains in recent data. Research to understand the dropoff is in progress; this letter is intended as a caution to users of the data. Our findings underscore the importance of regular ozonesonde data evaluation.

An automated method for preparing and calibrating electrochemical concentration cell (ECC) ozonesondes

Abstract. In contrast to the legacy manual method used to prepare, condition, and calibrate the electrochemical concentration cell (ECC) ozonesonde, an automated digital calibration bench similar to one developed by MeteoSwiss at Payerne, Switzerland, was established at NASA's Wallops Flight Facility and provides reference measurements of the same ozone partial pressure as measured by the ECC. The purpose of an automated system is to condition and calibrate ECCs before launching on a balloon. Operation of the digital calibration bench is simple and real-time graphs and summaries are available to the operator; all information is archived. The parameters of interest include ozone partial pressure, airflow, temperature, background current, response, and time (real and elapsed). ECCs, prepared with 1.0 % solution of potassium iodide (KI) and full buffer, show increasing partial pressure values when compared to the reference as partial pressures increase. Differences of approximately 5–6 % are noted at 20.0 mPa. Additional tests with different concentrations revealed the Science Pump Corp. (SPC) 6A ECC with 0.5 % KI solution and one-half buffer agreed closer to the reference than the 1.0 % cells. The information gained from the automated system allows a compilation of ECC characteristics, as well as calibrations. The digital calibration bench is recommended for ECC studies as it conserves resources.

The NASA Wallops Flight Facility Digital Ozonesonde Record: Reprocessing, Uncertainties, and Dual Launches

AbstractThe NASA Wallops Flight Facility (WFF; Wallops Is., VA, USA) is the longest continuously operating ozonesonde station in the continental United States (since 1970). The well‐established WFF ozonesonde system comprises a Science Pump Corporation (SPC) electrochemical concentration cell (ECC) ozone sensor with a 1% potassium iodide and phosphate buffer sensing solution type (SST), interfaced with a Lockheed Martin Sippican radiosonde that provides winds, GPS coordinates, pressure, temperature, and relative humidity. A major milestone has been achieved with the reprocessing of the WFF ozone profiles during the digital measurement era (since 1995) to remove known biases and improve overall accuracy. We present an overview of the reprocessing methods and evaluate the homogenized data set relative to the original records, colocated Dobson, and satellite overpasses. Reprocessing yields modest changes in total column ozone by up to 3%, affirming the high data quality of the original ozone records. First estimates of ozone uncertainty are summarized and found to be consistent with estimates from previous studies. WFF has a history of evaluating ozonesonde performance via dual sonde launches that have tested standard operating procedures and combinations of ECC sensors and SST formulae. This rich data set illustrates how various ECC/SST combinations affect the ozone measurement. Results from the dual launches reaffirm the World Meteorological Organization recommended standard operating procedures where the ozone agreement between the SPC/1% Buffer and EN‐SCI/0.5% Half Buffer pair is well within ±5% throughout the profile. Tests of the SST under field conditions reveal the high sensitivity of ozone measurements to the buffer strength.

Fabrication of the First Disposable Three‐dimensional Paper‐based Concentration Cell as Ammonia Sensor with a New Method for Paper Hydrophobization by Laser Patterned Parafilm®

AbstractA new, simple and low‐cost method for patterning hydrophobic barriers in porous support such as paper by Parafilm® has been introduced. This method is then used for electrochemical paper‐based ammonia sensor construction. Ammonia sensor is based on electrochemical concentration cell which ammonia reaction with electrolyte in halves cell caused in concentration gradient and therefore potential difference dependent on ammonia concentration. The effect of concentrations of the involved chemicals, time periods of the required processes, the presence of Faraday cage as well as the effects of different salts used in the salt bridge on the response of the sensor, were investigated in order to find the optimized conditions.

Ozonesonde Quality Assurance: The JOSIE-SHADOZ (2017) Experience.

The ozonesonde is a small balloon-borne instrument that is attached to a standard radiosonde to measure profiles of ozone from the surface to 35 km with ~100-m vertical resolution. Ozonesonde data constitute a mainstay of satellite calibration and are used for climatologies and analysis of trends, especially in the lower stratosphere where satellites are most uncertain. The electrochemical-concentration cell (ECC) ozonesonde has been deployed at ~100 stations worldwide since the 1960s, with changes over time in manufacture and procedures, including details of the cell chemical solution and data processing. As a consequence, there are biases among different stations and discontinuities in profile time-series from individual site records. For 22 years the Jülich [Germany] Ozone Sonde Intercomparison Experiment (JOSIE) has periodically tested ozonesondes in a simulation chamber designated the World Calibration Centre for Ozonesondes (WCCOS) by WMO. In October-November 2017 a JOSIE campaign evaluated the sondes and procedures used in SHADOZ (Southern Hemisphere Additional Ozonesondes), a 14-station sonde network operating in the tropics and subtropics. A distinctive feature of the 2017 JOSIE was that the tests were conducted by operators from eight SHADOZ stations. Experimental protocols for the SHADOZ sonde configurations, which represent most of those in use today, are described, along with preliminary results. SHADOZ stations that follow WMO-recommended protocols record total ozone within 3% of the JOSIE reference instrument. These results and prior JOSIEs demonstrate that regular testing is essential to maintain best practices in ozonesonde operations and to ensure high-quality data for the satellite and ozone assessment communities.