scholarly journals Methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) from ground-based FTIR at Addis Ababa: observations, error analysis and comparison with satellite data

2019 ◽  
Author(s):  
Temesgen Yirdaw Berhe ◽  
Gizaw Mengistu Tsidu ◽  
Thomas Blumenstock ◽  
Frank Hase ◽  
Gabriele P. Stiller
Keyword(s):  
Nitrous Oxide ◽  
Spectral Resolution ◽  
Lower Stratosphere ◽  
Addis Ababa ◽  
Negative Bias ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Ch4 And N2o

Abstract. A ground based high spectral resolution Fourier transform infrared (FTIR) spectrometer has been operational at Addis Ababa (9.0° N, 38.76° E, 2443 m a.s.l.) since May 2009 to obtain information on the total column abundances and vertical distribution of various constituents in the atmosphere. The retrieval strategy and the results on information content and corresponding full error budget evaluation for methane and nitrous oxide retrievals are presented. They reveal the high quality of FTIR measurements at Addis Ababa. The FTIR products of CH4 and N2O have been compared to coincident volume mixing ratio (VMR) measurements obtained from the reduced spectral resolution (Institute of Meteorology and Climate Research) IMK/IAA MIPAS satellite instrument (Version V5R_CH4_224 and V5R_N2O_224), the Microwave Limb Sounder on board of the Aura satellite (Aura/MLS) (MLS v3.3 of N2O and CH4 derived from MLS v3.3 products of CO, N2O and H2O) and the Atmospheric Infrared Sounder (AIRS). From comparison of FTIR CH4 and IMK/IAA MIPAS V5R_CH4_224, a statistically significant bias between −4.8 and +4.6 % in altitude ranges of the upper troposphere and lower stratosphere (15–27 km) are determined. The largest negative bias in FTIR CH4 is found in the altitude range of 11–19 km with a maximum difference of −0.08 ppmv (−4.8 %) at around 15 km, a positive bias of less than 0.14 ppmv (9 %) is found in the altitude range of 21 to 27 km with a maximum value at around 27 km with respect to AIRS. On the other hand, comparison of CH4 from ground based FTIR and MLS-derived CH4 (version 3.3) indicate existence of a significant positive bias of 2.3 % to 11 % in the altitude range of 20 to 27 km and a negative bias −1.7 % at 17 km. In the case of N2O derived from FTIR and MIPAS V5R_N2O_224 comparison, a significant positive bias of less than 15 % in the altitude range 22–27 km with a maximum value at around 25 km and a negative bias of −7 % have been found at 17 km. A positive bias of less than 18.6 % in FTIR N2O for the altitude below 27 km is noted when compared to MLS v3.3 N2O. Precision of ground based FTIR CH4 and N2O in the upper troposphere and lower stratosphere over Addis Ababa are better than 7.2 % and 9 %, respectively which are comparable to the bias obtained from the comparisons.

scholarly journals Methane and nitrous oxide from ground-based FTIR at Addis Ababa: observations, error analysis, and comparison with satellite data

2020 ◽  
Vol 13 (7) ◽  
pp. 4079-4096
Author(s):  
Temesgen Yirdaw Berhe ◽  
Gizaw Mengistu Tsidu ◽  
Thomas Blumenstock ◽  
Frank Hase ◽  
Gabriele P. Stiller
Keyword(s):  
Nitrous Oxide ◽  
Error Analysis ◽  
Spectral Resolution ◽  
Addis Ababa ◽  
Ftir Spectra ◽  
Negative Bias ◽  
Positive Bias ◽  
Altitude Range ◽  
Ch4 And N2o ◽  
Good Agreement

Abstract. A ground-based, high-spectral-resolution Fourier transform infrared (FTIR) spectrometer has been operational in Addis Ababa, Ethiopia (9.01∘ N latitude, 38.76∘ E longitude; 2443 m altitude above sea level), since May 2009 to obtain information on column abundances and profiles of various constituents in the atmosphere. Vertical profile and column abundances of methane and nitrous oxide are derived from solar absorption measurements taken by FTIR for a period that covers May 2009 to March 2013 using the retrieval code PROFFIT (V9.5). A detailed error analysis of CH4 and N2O retrieval are performed. Averaging kernels of the target gases shows that the major contribution to the retrieved information comes from the measurement. Thus, average degrees of freedom for signals are found to be 2.1 and 3.4, from the retrieval of CH4 and N2O for the total observed FTIR spectra. Methane and nitrous oxide volume mixing ratio (VMR) profiles and column amounts retrieved from FTIR spectra are compared with data from the reduced spectral resolution Institute of Meteorology and Climate Research/Instituto de Astrofísica de Andalucía (IMK/IAA) MIPAS (Version V5R_CH4_224 and V5R_N2O_224), the Microwave Limb Sounder (MLS) (MLS v3.3 of N2O and CH4 derived from MLS v3.3 products of CO, N2O, and H2O), and the Atmospheric Infrared Sounder (AIRS) sensors on board satellites. The averaged mean relative difference between FTIR methane and the three correlative instruments MIPAS, MLS, and AIRS are 4.2 %, 5.8 %, and 5.3 % in the altitude ranges of 20 to 27 km, respectively. However, the biases below 20 km are negative, which indicates the profile of CH4 from FTIR is less than the profiles derived from correlative instruments by −4.9 %, −1.8 %, and −2.8 %. The averaged positive bias between FTIR nitrous oxide and correlative instrument, MIPAS, in the altitude range of 20 to 27 km is 7.8 %, and a negative bias of −4 % at altitudes below 20 km. An averaged positive bias of 9.3 % in the altitude range of 17 to 27 km is obtained for FTIR N2O with MLS. In all the comparisons of CH4 from FTIR with data from MIPAS, MLS, and AIRS, sensors on board satellites indicate a negative bias below 20 km and a positive bias above 20 km. The mean error between partial-column amounts of methane from MIPAS and the ground-based FTIR is −5.5 %, with a standard deviation of 5 % that shows very good agreement as exhibited by relative differences between vertical profiles. Thus, the retrieved CH4 and N2O VMR and column amounts from Addis Ababa, tropical site, is found to exhibit very good agreement with all coincident satellite observations. Therefore, the bias obtained from the comparison is comparable to the precision of FTIR measurement, which allows the use of data in further scientific studies as it represents a unique environment of tropical Africa, a region poorly investigated in the past.

scholarly journals Retrieval of water vapor vertical distributions in the upper troposphere and the lower stratosphere from SCIAMACHY limb measurements

2011 ◽  
Vol 4 (5) ◽  
pp. 933-954 ◽  
Author(s):  
A. Rozanov ◽  
K. Weigel ◽  
H. Bovensmann ◽  
S. Dhomse ◽  
K.-U. Eichmann ◽  
...  
Keyword(s):  
Water Vapor ◽  
Solar Radiation ◽  
Lower Stratosphere ◽  
Water Vapor Content ◽  
Retrieval Algorithm ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Vertical Distributions ◽  
First Results ◽  
Scanning Imaging

Abstract. This study describes the retrieval of water vapor vertical distributions in the upper troposphere and lower stratosphere (UTLS) altitude range from space-borne observations of the scattered solar light made in limb viewing geometry. First results using measurements from SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) aboard ENVISAT (Environmental Satellite) are presented here. In previous publications, the retrieval of water vapor vertical distributions has been achieved exploiting either the emitted radiance leaving the atmosphere or the transmitted solar radiation. In this study, the scattered solar radiation is used as a new source of information on the water vapor content in the UTLS region. A recently developed retrieval algorithm utilizes the differential absorption structure of the water vapor in 1353–1410 nm spectral range and yields the water vapor content in the 11–25 km altitude range. In this study, the retrieval algorithm is successfully applied to SCIAMACHY limb measurements and the resulting water vapor profiles are compared to in situ balloon-borne observations. The results from both satellite and balloon-borne instruments are found to agree typically within 10 %.

scholarly journals Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

2010 ◽  
Vol 10 (1) ◽  
pp. 1457-1481
Author(s):  
N. Mze ◽  
A. Hauchecorne ◽  
H. Bencherif ◽  
F. Dalaudier ◽  
J.-L. Bertaux
Keyword(s):  
Southern Hemisphere ◽  
Satisfactory Agreement ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Stellar Occultation ◽  
Monthly Distribution

Abstract. In this paper, the stellar occultation instrument GOMOS is compared with ozonesondes from the SHADOZ network. We only used nighttime O3 profiles and a requirement selection at 8 Southern Hemisphere stations. 7 years of GOMOS datasets (GOPR 6.0cf and IPF 5.0) and 11 years of balloon-sondes are used in this study. A monthly distribution of GOMOS O3 mixing ratios is performed in the upper-troposphere and in the stratosphere (15–50 km). A comparison with SHADOZ is done in the altitude range from 15 km to 30 km. In the 21–30 km altitude range, a satisfactory agreement is observed between GOMOS and SHADOZ although some differences are observed depending on the station. The range for monthly differences is generally decreasing with increasing height and is within ±15%. It is found that the agreement between GOMOS and SHADOZ degrades below ~20 km. The median differences are nearly within ±5% particularly above 23 km. But a large positive bias is found below 21 km compared to SHADOZ.

scholarly journals Global HCFC-22 measurements with MIPAS: retrieval, validation, global distribution and its evolution over 2005–2012

2016 ◽  
Vol 16 (5) ◽  
pp. 3345-3368 ◽  
Author(s):  
M. Chirkov ◽  
G. P. Stiller ◽  
A. Laeng ◽  
S. Kellmann ◽  
T. von Clarmann ◽  
...  
Keyword(s):  
Time Series ◽  
Satellite Data ◽  
Lower Stratosphere ◽  
Positive Trend ◽  
Altitude Range ◽  
Quasi Biennial Oscillation ◽  
Near Surface ◽  
Upper Troposphere ◽  
The Tropics ◽  
Balloon Measurements

Abstract. We report on HCFC-22 data acquired by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in the reduced spectral resolution nominal observation mode. The data cover the period from January 2005 to April 2012 and the altitude range from the upper troposphere (above cloud top altitude) to about 50 km. The profile retrieval was performed by constrained nonlinear least squares fitting of modelled spectra to the measured limb spectral radiances. The spectral ν4-band at 816.5 ± 13 cm−1 was used for the retrieval. A Tikhonov-type smoothing constraint was applied to stabilise the retrieval. In the lower stratosphere, we find a global volume mixing ratio of HCFC-22 of about 185 pptv in January 2005. The rate of linear growth in the lower latitudes lower stratosphere was about 6 to 7 pptv year−1 in the period 2005–2012. The profiles obtained were compared with ACE-FTS satellite data v3.5, as well as with MkIV balloon profiles and cryosampler balloon measurements. Between 13 and 22 km, average agreement within −3 to +5 pptv (MIPAS – ACE) with ACE-FTS v3.5 profiles is demonstrated. Agreement with MkIV solar occultation balloon-borne measurements is within 10–20 pptv below 30 km and worse above, while in situ cryosampler balloon measurements are systematically lower over their full altitude range by 15–50 pptv below 24 km and less than 10 pptv above 28 km. MIPAS HCFC-22 time series below 10 km altitude are shown to agree mostly well to corresponding time series of near-surface abundances from the NOAA/ESRL and AGAGE networks, although a more pronounced seasonal cycle is obvious in the satellite data. This is attributed to tropopause altitude fluctuations and subsidence of polar winter stratospheric air into the troposphere. A parametric model consisting of constant, linear, quasi-biennial oscillation (QBO) and several sine and cosine terms with different periods has been fitted to the temporal variation of stratospheric HCFC-22 for all 10°-latitude/1-to-2-km-altitude bins. The relative linear variation was always positive, with relative increases of 40–70 % decade−1 in the tropics and global lower stratosphere, and up to 120 % decade−1 in the upper stratosphere of the northern polar region and the southern extratropical hemisphere. Asian HCFC-22 emissions have become the major source of global upper tropospheric HCFC-22. In the upper troposphere, monsoon air, rich in HCFC-22, is instantaneously mixed into the tropics. In the middle stratosphere, between 20 and 30 km, the observed trend is inconsistent with the trend at the surface (corrected for the age of stratospheric air), hinting at circulation changes. There exists a stronger positive trend in HCFC-22 in the Southern Hemisphere and a more muted positive trend in the Northern Hemisphere, implying a potential change in the stratospheric circulation over the observation period.

scholarly journals Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

2010 ◽  
Vol 10 (16) ◽  
pp. 8025-8035 ◽  
Author(s):  
N. Mze ◽  
A. Hauchecorne ◽  
H. Bencherif ◽  
F. Dalaudier ◽  
J.-L. Bertaux
Keyword(s):  
Southern Hemisphere ◽  
Satisfactory Agreement ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Stellar Occultation ◽  
Monthly Distribution ◽  
Made In

Abstract. In this paper, the stellar occultation instrument GOMOS is compared with ozonesondes from the SHADOZ network. We only used nighttime O3 profiles and selected 8 Southern Hemisphere stations. 7 years of GOMOS datasets (GOPR 6.0cf and IPF 5.0) and 11 years of balloon-sondes are used in this study. A monthly distribution of GOMOS O3 mixing ratios was performed in the upper-troposphere and in the stratosphere (15–50 km). A comparison with SHADOZ was made in the altitude range between 15 km and 30 km. In the 21–30 km altitude range, a satisfactory agreement was observed between GOMOS and SHADOZ, although some differences were observed depending on the station. The range for monthly differences generally decreases with increasing height and is within ±15%. It was found that the agreement between GOMOS and SHADOZ declines below ~20 km. The median differences are almost within ±5%, particularly above 23 km. But a large positive bias was found below 21 km, in comparison to SHADOZ.

scholarly journals Validation of version-4.61 methane and nitrous oxide observed by MIPAS

2009 ◽  
Vol 9 (2) ◽  
pp. 413-442 ◽  
Author(s):  
S. Payan ◽  
C. Camy-Peyret ◽  
H. Oelhaf ◽  
G. Wetzel ◽  
G. Maucher ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Positive Bias ◽  
Full Resolution ◽  
Processing Facility ◽  
Satellite Sensors ◽  
Ch4 And N2o ◽  
The Individual ◽  
Instrument Processing ◽  
Internal Error ◽  
Middle Stratosphere

Abstract. The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61, full resolution MIPAS data covering the period 9 July 2002 to 26 March 2004) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. In the middle stratosphere, no significant bias is observed between MIPAS and correlative measurements, and MIPAS is providing a very consistent and global picture of the distribution of CH4 and N2O in this region. In average, the MIPAS CH4 values show a small positive bias in the lower stratosphere of about 5%. A similar situation is observed for N2O with a positive bias of 4%. In the lower stratosphere/upper troposphere (UT/LS) the individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61 and the estimated errors of the correlative measurements.

scholarly journals MIPAS reference atmospheres and comparisons to V4.61/V4.62 MIPAS level 2 geophysical data sets

2007 ◽  
Vol 7 (4) ◽  
pp. 9973-10017 ◽  
Author(s):  
J. J. Remedios ◽  
R. J. Leigh ◽  
A. M. Waterfall ◽  
D. P. Moore ◽  
H. Sembhi ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Michelson Interferometer ◽  
Initial Guess ◽  
Data Sets ◽  
Upper Troposphere ◽  
Dynamic Representation ◽  
Ch4 And N2o ◽  
Key Aspects ◽  
The Tropics ◽  
Maximum Minimum

Abstract. Reliable reference profiles and estimates of variability are a necessity for a variety of processes relating to ENVISAT including the development of key aspects and inputs for the operational processor for the Michelson Interferometer for Passive Atmospheric Sounding. MIPAS reference atmospheres have therefore been produced in two forms, namely standard atmospheres for modelling and error analysis for typical atmospheric situations and the IG2 seasonal climatologies for initial guess profiles used as part of the operational processing. The reference states cover 36 species on a common altitude, pressure, and temperature grid from 0 to 120 km, and include both means and estimates of variability (maximum, minimum and one sigma values). This paper describes V3.1 of the standard atmospheres and V4.0 of the IG2 atmospheres which are the current versions of the reference atmospheres. Particular attention is paid to the MIPAS operational geophysical products (pressure/temperature, H2O, O3, CH4, N2O, HNO3 and NO2) and to CO2 whose mixing ratio is required for the retrieval of pressure and temperature. A dynamic representation of CO2 is presented which shows the presence of CO2 gradients in the troposphere and the lower stratosphere. Since these atmospheres have been produced independently of MIPAS data, it is also possible to compare the data to the MIPAS operational products and derive valuable information on both the reference atmospheres and on MIPAS data products themselves. This process has been performed for V4.61/V4.62 data from the year 2003 as part of the MIPAS validation activity. It is demonstrated that the agreement between the MIPAS mean data and the reference atmospheres is very good in mid-latitudes and the tropics, verifying these data to first order. There is also reasonable agreement in standard deviations between the IG2 atmospheres and the corresponding sigmas calculated from the MIPAS data. Knowledge of tropospheric concentrations of CH4 and N2O is used to examine the accuracy of the MIPAS data and their susceptibility to cloud effects. It is shown that for the highest accuracy, MIPAS data should be filtered with cloud index values of 2.5 for N2O and 3.5 for CH4. Once such filtering has been performed, the MIPAS data for these species appear to be accurate to within 10% in the upper troposphere. The use of cloud index data in combination with MIPAS data is recommended for studies of the polar winter stratosphere and the upper troposphere/lower stratosphere.

scholarly journals Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm

2007 ◽  
Vol 7 (6) ◽  
pp. 18043-18111 ◽  
Author(s):  
S. Payan ◽  
C. Camy-Peyret ◽  
H. Oelhaf ◽  
G. Wetzel ◽  
G. Maucher ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Positive Bias ◽  
Systematic Deviation ◽  
Processing Facility ◽  
Satellite Sensors ◽  
Ch4 And N2o ◽  
The Individual ◽  
Instrument Processing ◽  
Internal Error ◽  
Validation Experiments

Abstract. The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-bone, aircraft and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign of ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. The MIPAS-E CH4 values show a positive bias in the lower stratosphere of about 10%. In case of N2O no systematic deviation with respect to the validation experiments could be identified. The individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61.

scholarly journals Seasonal characteristics of chemical and dynamical transports into the extratropical upper troposphere/lower stratosphere

2018 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Lower Troposphere ◽  
Air Masses ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Chemical Tracers ◽  
Spatiotemporal Distributions ◽  
Seasonal Characteristics ◽  
Exchange Processes ◽  
Ch4 And N2o

Abstract. To investigate the seasonal characteristics of chemical tracer distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, mixing fractions of air masses originating in the stratosphere, tropical troposphere, mid-latitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 90-day backward trajectories calculated with European Centre For Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time-series of chemical tracers obtained from ground-based and airborne observations are incorporated into the estimated mixing fractions, thus reconstructing spatiotemporal distributions of chemical tracers in the ExUTLS. The reconstructed tracer distributions are analysed with the mixing fractions and the stratospheric age of air (AoA) estimated using a 10-year backward trajectory. The reconstructed distributions of CO and CO2 in the ExUTLS are affected primarily by tropospheric air masses because of the short chemical lifetime of the former and large seasonal variations in the troposphere of the latter. Distributions of CH4, N2O, and SF6 are controlled primarily by seasonally varying air masses transported from the stratosphere. For CH4 and N2O distributions, air masses transported via the deep branch of the Brewer–Dobson circulation are particularly important. This interpretation is qualitatively and quantitatively supported by the estimated spatiotemporal distributions of AoA.

scholarly journals Retrieval of water vapor vertical distributions in the upper troposphere and the lower stratosphere from SCIAMACHY limb measurements

2010 ◽  
Vol 3 (5) ◽  
pp. 4009-4057 ◽  
Author(s):  
A. Rozanov ◽  
K. Weigel ◽  
H. Bovensmann ◽  
S. Dhomse ◽  
K.-U. Eichmann ◽  
...  
Keyword(s):  
Water Vapor ◽  
Solar Radiation ◽  
Lower Stratosphere ◽  
Water Vapor Content ◽  
Retrieval Algorithm ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Vertical Distributions ◽  
First Results

Abstract. This study describes the retrieval of water vapor vertical distributions in the upper troposphere and lower stratosphere (UTLS) altitude range from space-borne observations of the scattered solar light made in limb viewing geometry and presents first results using measurements from SCIAMACHY. In the previous publications, the retrieval of water vapor vertical distributions has been achieved exploiting either the emitted radiance leaving the atmosphere or the transmitted solar radiation. In this study the scattered solar radiation is used as a new source of information on the water vapor content in the UTLS region. A recently developed retrieval algorithm utilizes the differential absorption structure of the water vapor in 1353–1410 nm spectral range and yields the water vapor content in 11–25 km altitude range. In this study the retrieval algorithm is successfully applied to SCIAMACHY limb measurements and the resulting water vapor profiles are compared to in situ balloon-borne observations. The results from both satellite and balloon-borne instruments are found to agree typically within 20%.

Sign in / Sign up

Export Citation Format

Share Document