scholarly journals A fully Automated Dobson Sun Spectrophotometer for total column ozone and Umkehr measurements

2020 ◽  
Author(s):  
René Stübi ◽  
Herbert Schill ◽  
Jörg Klausen ◽  
Eliane Maillard Barras ◽  
Alexander Haefele
Keyword(s):  
Global Network ◽  
Automated Control ◽  
Total Column Ozone ◽  
Manual Operation ◽  
Clear Sky ◽  
Technical Details ◽  
Column Ozone ◽  
Sky Conditions ◽  
Ozone Column ◽  
Dobson Spectrophotometer

Abstract. The longest ozone column measurements series are based on the Dobson sun spectrophotometers developed in the 1920s by Prof. G. B. W. Dobson. These ingenious and robustly designed instruments still constitute an important part of the global network presently. However, the Dobson sun spectrophotometer needs manual operation which leads to the discontinuation of its use at many stations. To overcome this problem, MeteoSwiss developed a fully automated version of the Dobson spectrophotometer. The description of the data acquisition and automated control of the instrument is presented here with some technical details. The results of different tests performed regularly to control the instrument good working operation are illustrated and discussed. Compared to manual operation, the automation results in higher frequency measurements with lower random error and additional housekeeping information to characterise the measuring conditions. The automated Dobson instrument allows a continuous observation of the ozone column with a resolution of ~1 DU unit under clear sky conditions.

scholarly journals A fully automated Dobson sun spectrophotometer for total column ozone and Umkehr measurements

2021 ◽  
Vol 14 (8) ◽  
pp. 5757-5769
Author(s):  
René Stübi ◽  
Herbert Schill ◽  
Jörg Klausen ◽  
Eliane Maillard Barras ◽  
Alexander Haefele
Keyword(s):  
Global Network ◽  
Automated Control ◽  
Total Column Ozone ◽  
Manual Operation ◽  
Clear Sky ◽  
Technical Details ◽  
Column Ozone ◽  
Sky Conditions ◽  
Ozone Column

Abstract. The longest ozone column measurement series are based on the Dobson sun spectrophotometers developed in the 1920s by Prof. G. B. W. Dobson​​​​​​​. These ingenious and robustly designed instruments still constitute an important part of the global network presently. However, the Dobson sun spectrophotometer requires manual operation, which has led to the discontinuation of its use at many stations, thus disrupting long-term records of observation. To overcome this problem, MeteoSwiss developed a fully automated version of the Dobson spectrophotometer. The description of the data acquisition and automated control of the instrument is presented here with some technical details. The results of different tests performed regularly to assess the instrument's good working conditions are illustrated and discussed. Compared to manual operation, automation results in a higher number of daily measurements with lower random error and additional housekeeping information to characterize the measuring conditions. The automated Dobson instrument allows for continuous observation of the ozone column with a resolution of ∼ 1 DU under clear-sky conditions.

scholarly journals Possible values of UV index in Serbia

2008 ◽  
Vol 136 (11-12) ◽  
pp. 640-643 ◽  
Author(s):  
Milorad Letic
Keyword(s):  
Uv Radiation ◽  
The Sun ◽  
Total Column Ozone ◽  
Uv Index ◽  
Clear Sky ◽  
Expected Values ◽  
June July ◽  
Column Ozone ◽  
Ozone Column

INTRODUCTION UV Index is an indicator of human exposure to solar ultraviolet (UV) rays. The numerical values of the UV Index range from 1-11 and above. There are three levels of protection against UV radiation; low values of the UV Index - protection is not required, medium values of the UV Index - protection is recommended and high values of the UV Index - protection is obligatory. The value of the UV Index primarily depends on the elevation of the sun and total ozone column. OBJECTIVE The aim of the study is to determine the intervals of possible maximal annual values of the UV Index in Serbia in order to determine the necessary level of protection in a simple manner. METHOD For maximal and minimal expected values of total column ozone and for maximal elevation of the sun, the value of the UV Index was determined for each month in the Northern and Southern parts of Serbia. These values were compared with the forecast of the UV Index. RESULTS Maximal clear sky values of the UV Index in Serbia for altitudes up to 500m in May, June, July and August can be 9 or even 10, and not less than 5 or 6. During November, December, January and February the UV Index can be 4 at most. During March, April, September and October the expected values of the UV Index are maximally 7 and not less than 3. The forecast of the UV Index is within these limits in 98% of comparisons. CONCLUSION The described method of determination of possible UV Index values showed a high agreement with forecasts. The obtained results can be used for general recommendations in the protection against UV radiation.

scholarly journals Uncertainty analysis of total ozone derived from direct solar irradiance spectra in the presence of unknown spectral deviations

2018 ◽  
Vol 11 (6) ◽  
pp. 3595-3610 ◽  
Author(s):  
Anna Vaskuri ◽  
Petri Kärhä ◽  
Luca Egli ◽  
Julian Gröbner ◽  
Erkki Ikonen
Keyword(s):  
Solar Irradiance ◽  
Total Ozone ◽  
Monte Carlo Model ◽  
Spectral Irradiance ◽  
Total Column Ozone ◽  
Column Ozone ◽  
Ozone Column ◽  
Total Column ◽  
Local Noon ◽  
Good Agreement

Abstract. We demonstrate the use of a Monte Carlo model to estimate the uncertainties in total ozone column (TOC) derived from ground-based direct solar spectral irradiance measurements. The model estimates the effects of possible systematic spectral deviations in the solar irradiance spectra on the uncertainties in retrieved TOC. The model is tested with spectral data measured with three different spectroradiometers at an intercomparison campaign of the research project “Traceability for atmospheric total column ozone” at Izaña, Tenerife on 17 September 2016. The TOC values derived at local noon have expanded uncertainties of 1.3 % (3.6 DU) for a high-end scanning spectroradiometer, 1.5 % (4.4 DU) for a high-end array spectroradiometer, and 4.7 % (13.3 DU) for a roughly adopted instrument based on commercially available components and an array spectroradiometer when correlations are taken into account. When neglecting the effects of systematic spectral deviations, the uncertainties reduce by a factor of 3. The TOC results of all devices have good agreement with each other, within the uncertainties, and with the reference values of the order of 282 DU during the analysed day, measured with Brewer spectrophotometer #183.

scholarly journals Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: comparison with coincident satellite and aircraft measurements

2005 ◽  
Vol 5 (8) ◽  
pp. 2035-2054 ◽  
Author(s):  
J. M. Livingston ◽  
B. Schmid ◽  
P. B. Russell ◽  
J. A. Eilers ◽  
R. W. Kolyer ◽  
...  
Keyword(s):  
Research Center ◽  
Total Column Ozone ◽  
Solar Occultation ◽  
Latitudinal Transect ◽  
Validation Experiment ◽  
Satellite Sensors ◽  
Langley Research Center ◽  
Column Ozone ◽  
Ozone Column ◽  
Total Column

Abstract. During the 2003 SAGE (Stratospheric Aerosol and Gas Experiment) III Ozone Loss and Validation Experiment (SOLVE) II, the fourteen-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14) was mounted on the NASA DC-8 aircraft and measured spectra of total and aerosol optical depth (TOD and AOD) during the sunlit portions of eight science flights. Values of ozone column content above the aircraft have been derived from the AATS-14 measurements by using a linear least squares method that exploits the differential ozone absorption in the seven AATS-14 channels located within the Chappuis band. We compare AATS-14 columnar ozone retrievals with temporally and spatially near-coincident measurements acquired by the SAGE III and the Polar Ozone and Aerosol Measurement (POAM) III satellite sensors during four solar occultation events observed by each satellite. RMS differences are 19 DU (7% of the AATS value) for AATS-SAGE and 10 DU (3% of the AATS value) for AATS-POAM. In these checks of consistency between AATS-14 and SAGE III or POAM III ozone results, the AATS-14 analyses use airmass factors derived from the relative vertical profiles of ozone and aerosol extinction obtained by SAGE III or POAM III. We also compare AATS-14 ozone retrievals for measurements obtained during three DC-8 flights that included extended horizontal transects with total column ozone data acquired by the Total Ozone Mapping Spectrometer (TOMS) and the Global Ozone Monitoring Experiment (GOME) satellite sensors. To enable these comparisons, the amount of ozone in the column below the aircraft is estimated either by assuming a climatological model or by combining SAGE and/or POAM data with high resolution in-situ ozone measurements acquired by the NASA Langley Research Center chemiluminescent ozone sensor, FASTOZ, during the aircraft vertical profile at the start or end of each flight. Resultant total column ozone values agree with corresponding TOMS and GOME measurements to within 10-15 DU (~3%) for AATS data acquired during two flights - a longitudinal transect from Sweden to Greenland on 21 January, and a latitudinal transect from 47° N to 35° N on 6 February. For the round trip DC-8 latitudinal transect between 34° N and 22° N on 19-20 December 2002, resultant AATS-14 ozone retrievals plus below-aircraft ozone estimates yield a latitudinal gradient that is similar in shape to that observed by TOMS and GOME, but resultant AATS values exceed the corresponding satellite values by up to 30 DU at certain latitudes. These differences are unexplained, but they are attributed to spatial and temporal variability that was associated with the dynamics near the subtropical jet but was unresolved by the satellite sensors. For selected cases, we also compare AATS-14 ozone retrievals with values derived from coincident measurements by the other two DC-8 based solar occultation instruments: the National Center for Atmospheric Research Direct beam Irradiance Airborne Spectrometer (DIAS) and the NASA Langley Research Center Gas and Aerosol Monitoring System (GAMS). AATS and DIAS retrievals agree to within RMS differences of 1% of the AATS values for the 21 January and 19-20 December flights, and 2.3% for the 6 February flight. Corresponding AATS-GAMS RMS differences are ~1.5% for the 21 January flight; GAMS data were not compared for the 6 February flight and were not available for the 19-20 December flight. Line of sight ozone retrievals from coincident measurements obtained by the three DC-8 solar occultation instruments during the SAGE III solar occultation event on 24 January yield RMS differences of 2.1% for AATS-DIAS and 0.5% for AATS-GAMS.

scholarly journals Quality assessment of Dobson spectrophotometers for ozone column measurements before and after automation at Arosa and Davos

2020 ◽  
Author(s):  
René Stübi ◽  
Herbert Schill ◽  
Eliane Maillard Barras ◽  
Jörg Klausen ◽  
Alexander Haefele
Keyword(s):  
Standard Deviation ◽  
Developed Countries ◽  
Global Network ◽  
Manual Operation ◽  
Operation Procedure ◽  
Before And After ◽  
Mean Differences ◽  
Automated Data Acquisition ◽  
And Control ◽  
Ozone Column

Abstract. The longest ozone column measurements series are based on the Dobson sun spectrophotometers developed in the 1920s by Prof. G. B. W. Dobson. These instruments still constitute an important part of the World Meteorological Organization's global network due to their optical qualities and ruggedness. The primary drawback of this instrument is the effort needed for its manual operation. In industrialized and some lesser developed countries, most stations have made the choice to replace the Dobson by the automated Brewer sun spectrophotometers but some are still relying on the Dobson instrument. One of them is the Arosa station where both instrument types are run in parallel. Here, an automated version of the Dobson instrument was developed and implemented recently. In the present paper, the results of the analysis of simultaneous measurements from pairs of Dobson instruments that were either collocated at Arosa or Davos, or operated one at each location, are presented for four distinct time periods: – 1992–2012 : Manual vs. Manual operation of Collocated Dobson instruments (MMC) – 2012–2013 : Manual vs. Automated operation of Collocated Dobson instruments (MAC) – 2012–2019 : Automated vs. Automated operation of Collocated Dobson instruments (AAC) and – 2016–2019 : Automated vs. Automated operation of Distant Dobson instruments (AAD) The direct comparison of two instruments using the standard operation procedure during the MMC period gives a metric necessary to validate the automated version of Dobson instruments. The direct comparison of two collocated instruments using the standard manual operation procedure reveals random differences of coincident observations with a standard deviation of ∼0.45 % and monthly mean differences between −1.0 and +0.8 %. In most cases the observed biases are not statistically significant. The same analysis of two automated Dobson instruments yields significantly smaller standard deviation of ∼0.25 % and biases of between −0.7 % and 0.8 %. This demonstrates that the repeatability has improved with the automation while the systematic differences are only marginally smaller. The description of the automated data acquisition and control of the Dobson instrument is presented in a separate paper (Stübi et al. , 2020).

scholarly journals Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 1: Analysis of parameter influence

2010 ◽  
Vol 10 (3) ◽  
pp. 6797-6827 ◽  
Author(s):  
M. Antón ◽  
V. E. Cachorro ◽  
J. M. Vilaplana ◽  
C. Toledano ◽  
N. A. Krotkov ◽  
...  
Keyword(s):  
Companion Paper ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Solar Elevation ◽  
Uv Irradiance ◽  
Ozone Monitoring ◽  
Absorbing Aerosols ◽  
Column Ozone ◽  
Sky Conditions

Abstract. The main objective of this study is to compare the erythemal UV irradiance (UVER) and spectral UV irradiances (at 305, 310 and 324 nm) from Ozone Monitoring Instrument (OMI) onboard NASA EOS/Aura polar sun-synchronous satellite (launched in July 2004, local equator crossing time 01:45 p.m.) with ground-based measurements from the Brewer spectroradiometer #150 located at El Arenosillo (South of Spain). The analyzed period comprises more than four years, from October 2004 to December 2008. The effects of several factors (clouds, aerosols, ozone and the solar elevation) on OMI-Brewer comparisons were analyzed. The proxies used for each factor were: OMI Lambertian Equivalent Reflectivity (LER) at 360 nm (clouds), the Aerosol Optical Depth (AOD) at 440 nm measured from the ground-based Cimel sun-photometer (http://aeronet.gsfc.nasa.gov), OMI total column ozone, and solar elevation at OMI overpass time. The comparison for all sky conditions reveals positive biases (OMI higher than Brewer) 12.3% for UVER, 14.2% for UV irradiance at 305 nm, 10.6% for 310 nm and 8.7% for 324 nm. The OMI-Brewer Root Mean Square Error (RMSE) is reduced when cloudy cases are removed from the analysis, (e.g., RMSE ~20% for all sky conditions and RMSE smaller than 10% for cloud-free conditions). However, the biases remain and even become more significant for the cloud-free cases with respect to all sky conditions. The mentioned overestimation is clearly documented as due to aerosol extinction influence. The differences OMI-Brewer typically decrease with increasing the Solar Zenith Angle (SZA). The seasonal dependence of the OMI-Brewer difference for cloud-free conditions is driven by aerosol climatology. To account for the aerosol effect, a first evaluation in order to compare with previous TOMS results (Anton et al., 2007) was performed. This comparison shows that the OMI bias is between +14% and +19% for UVER and spectral UV irradiances for moderately-high aerosol load (AOD>0.25). The OMI bias is decreased by a factor of 2 (the typical bias varies from +8% to +12%) under cloud-free and low aerosol load conditions (AOD<0.1). More detailed analysis of absorbing aerosols influence on OMI bias at our station is presented in a companion paper (Cachorro et al., 2010).

scholarly journals Monte Carlo method for determining uncertainty of total ozone derived from direct solar irradiance spectra: Application to Izaña results

2018 ◽  
Author(s):  
Anna Vaskuri ◽  
Petri Kärhä ◽  
Luca Egli ◽  
Julian Gröbner ◽  
Erkki Ikonen
Keyword(s):  
Monte Carlo ◽  
Total Ozone ◽  
Monte Carlo Model ◽  
Spectral Irradiance ◽  
Total Column Ozone ◽  
Solar Spectral Irradiance ◽  
Irradiance Data ◽  
Column Ozone ◽  
Ozone Column ◽  
Total Column

Abstract. We demonstrate a Monte Carlo model to calculate the uncertainties of total ozone column, TOC, derived from ground-based directional solar spectral irradiance measurements. The model takes into account effects that correlations in the spectral irradiance data may have on the results. The model is tested with spectral data measured with three different spectroradiometers at an intercomparison campaign of the research project Traceability for atmospheric total column ozone at Izaña, Tenerife on 17 September 2016. The TOC values derived at noon have expanded uncertainties of 1.3 % for a high-end scanning spectroradiometer, 1.3 % for a high-end array spectroradiometer, and 3.3 % for a roughly adopted instrument based on commercially available components and an array spectroradiometer. The level of TOC measured with reference Brewer spectrophotometer #183 is of the order of 282 DU during the analysed day and in agreement with the results of the two former instruments.

scholarly journals Are there urban signatures in the tropospheric ozone column products derived from satellite measurements?

2010 ◽  
Vol 10 (11) ◽  
pp. 5213-5222 ◽  
Author(s):  
J. Kar ◽  
J. Fishman ◽  
J. K. Creilson ◽  
A. Richter ◽  
J. Ziemke ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Lower Troposphere ◽  
Data Sets ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
Ratio Distribution ◽  
Total Column Ozone ◽  
Scanning Imaging ◽  
Column Ozone ◽  
Ozone Column

Abstract. In view of the proposed geostationary satellite missions to monitor air quality from space, it is important to first assess the capability of the current suite of satellite instruments to provide information on the urban scale pollution. We explore the possibility of detecting urban signatures in the tropospheric column ozone data derived from Total Ozone Mapping Spectrometer (TOMS)/Solar Backscattered Ultraviolet (SBUV) and Ozone Monitoring Instrument (OMI)/Microwave Limb Sounder (MLS) satellite data. We find that distinct isolated plumes of tropospheric ozone near several large and polluted cities around the world may be detected in these data sets. The ozone plumes generally correspond with the tropospheric column NO2 plumes around these cities as observed by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument. Similar plumes are also seen in tropospheric mean ozone mixing ratio distribution after accounting for the surface and tropopause pressure variations. The total column ozone retrievals indicate fairly significant sensitivity to the lower troposphere over the polluted land areas, which might help explain these detections. These results indicate that ultraviolet (UV) measurements may, in principle, be able to capture the urban signatures and may have implications for future missions using geostationary satellites.

scholarly journals Total column ozone measurements by the Dobson spectrophotometer at Belsk (Poland) for the period 1963–2019: homogenization and adjustment to the Brewer spectrophotometer

2021 ◽  
Vol 13 (9) ◽  
pp. 4425-4436
Author(s):  
Janusz W. Krzyścin ◽  
Bonawentura Rajewska-Więch ◽  
Janusz Jarosławski
Keyword(s):  
Weather Conditions ◽  
Total Column Ozone ◽  
Long Term Stability ◽  
Ultraviolet Range ◽  
Brewer Spectrophotometer ◽  
World Standard ◽  
Column Ozone ◽  
Total Column ◽  
Dobson Spectrophotometer

Abstract. The total column ozone (TCO3) measurements by the Dobson spectrophotometer (serial no. 84) have been carried out at Belsk station (51∘50′ N, 20∘47′ E), Poland, since 23 March 1963. In total, ∼115 000 intraday manual observations were made by 31 December 2019. These observations were performed for different combinations of double wavelength pairs in the ultraviolet range and observation types, i.e., direct sun (DS), zenith blue (ZB), and zenith cloudy (ZC) depending on weather conditions. The long-term stability of the instrument was supported by frequent (almost every 4 years) intercomparisons with the world standard spectrophotometer. Trend analyses, based on the monthly and yearly averaged TCO3, can be carried out without any additional corrections to the intraday values. To adjust these data to the Brewer spectrophotometer observations, which were also performed at Belsk, a procedure is proposed to account for less accurate Dobson observations under low solar elevation, presence of clouds, and the temperature dependence of ozone absorption. The adjusted time series shows that the Brewer–Dobson monthly averaged differences are in the range of about ±0.5 %. The intraday TCO3 database, divided into three periods (1963–1979, 1980–1999, and 2000–2019), is freely available at https://doi.org/10.1594/PANGAEA.919378 (Rajewska-Więch et al., 2020).

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