scholarly journals Intercomparison of atmospheric water vapour measurements in the Canadian high Arctic

2016 ◽  
Author(s):  
Dan Weaver ◽  
Kimberly Strong ◽  
Matthias Schneider ◽  
Penny M. Rowe ◽  
Chris Sioris ◽  
...  
Keyword(s):  
Water Vapour ◽  
Microwave Radiometer ◽  
Correlation Coefficients ◽  
High Arctic ◽  
Atmospheric Water ◽  
Canadian High Arctic ◽  
Solar Absorption ◽  
Atmospheric Water Vapour ◽  
Retrieval Technique ◽  
Good Agreement

Abstract. Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian high Arctic research site. Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform spectrometers (FTSs). Good agreement is observed between all combination of datasets, with correlation coefficients ≥ 0.90 showing high correlations. A variety of biases and calibration issues are revealed and discussed for all instruments. A new FTS dataset, resulting from the MUSICA (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique, is shown to offer accurate measurements of water vapour total columns; however, measurements show a small wet bias of approximately 6 %. A new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is also shown to provide accurate water vapour measurements, which usefully enables measurements to be taken during day and night (especially valuable during Polar Night). In addition, limited profile comparisons are conducted using radiosonde and ground-based FTS measurements. Results show MUSICA FTS profiles were within 15 % of radiosonde measurements throughout the troposphere.

scholarly journals Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site

2017 ◽  
Vol 10 (8) ◽  
pp. 2851-2880 ◽  
Author(s):  
Dan Weaver ◽  
Kimberly Strong ◽  
Matthias Schneider ◽  
Penny M. Rowe ◽  
Chris Sioris ◽  
...  
Keyword(s):  
Water Vapour ◽  
Global Climate ◽  
Microwave Radiometer ◽  
Correlation Coefficients ◽  
High Arctic ◽  
Atmospheric Water ◽  
Canadian High Arctic ◽  
Solar Absorption ◽  
Atmospheric Water Vapour ◽  
Ftir Spectrometer

Abstract. Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian High Arctic research site (Eureka, Nunavut). Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform infrared (FTIR) spectrometers. Close agreement is observed between all combination of datasets, with mean differences  ≤  1.0 kg m−2 and correlation coefficients  ≥  0.98. The one exception in the observed high correlation is the comparison between the microwave radiometer and a radiosonde product, which had a correlation coefficient of 0.92.A variety of biases affecting Eureka instruments are revealed and discussed. A subset of Eureka radiosonde measurements was processed by the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) for this study. Comparisons reveal a small dry bias in the standard radiosonde measurement water vapour total columns of approximately 4 %. A recently produced solar absorption FTIR spectrometer dataset resulting from the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique is shown to offer accurate measurements of water vapour total columns (e.g. average agreement within −5.2 % of GRUAN and −6.5 % of a co-located emission FTIR spectrometer). However, comparisons show a small wet bias of approximately 6 % at the high-latitude Eureka site. In addition, a new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is shown to provide accurate water vapour measurements (e.g. average agreement was within 4 % of GRUAN), which usefully enables measurements to be taken during day and night (especially valuable during polar night).

Supplementary material to "Intercomparison of atmospheric water vapour measurements in the Canadian high Arctic"

2016 ◽  
Author(s):  
Dan Weaver ◽  
Kimberly Strong ◽  
Matthias Schneider ◽  
Penny M. Rowe ◽  
Chris Sioris ◽  
...  
Keyword(s):  
Water Vapour ◽  
High Arctic ◽  
Atmospheric Water ◽  
Canadian High Arctic ◽  
Atmospheric Water Vapour ◽  
Supplementary Material

scholarly journals MAX-DOAS observations of the total atmospheric water vapour column and comparison with independent observations

2013 ◽  
Vol 6 (1) ◽  
pp. 131-149 ◽  
Author(s):  
T. Wagner ◽  
M. O. Andreae ◽  
S. Beirle ◽  
S. Dörner ◽  
K. Mies ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Water Vapour ◽  
Satellite Observations ◽  
Shielding Effect ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Water ◽  
Near Surface ◽  
Atmospheric Water Vapour ◽  
Independent Observations ◽  
Good Agreement

Abstract. We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so-called geometric approximation and does not depend on explicit a priori information for individual observations, extensive radiative transfer simulations, or the construction of large look-up tables. Disturbances of the radiative transfer due to aerosols and clouds are simply corrected using the simultaneously measured absorptions of the oxygen dimer, O4. We applied our algorithm to MAX-DOAS observations made at the Max Planck Institute for Chemistry in Mainz, Germany, from March to August 2011, and compared the results to independent observations. Good agreement with Aerosol Robotic Network (AERONET) and European Centre for Medium-Range Weather Forecasting (ECMWF) H2O vertical column densities (VCDs) is found, while the agreement with satellite observations is less good, most probably caused by the shielding effect of clouds for the satellite observations. Good agreement is also found with near-surface in situ observations, and it was possible to derive average daily H2O scale heights (between 1.5 km and 3 km). MAX-DOAS measurements use cheap and simple instrumentation and can be run automatically. One important advantage of our algorithm is that the H2O VCD can be retrieved even under cloudy conditions (except clouds with very high optical thickness).

scholarly journals Validation of middle atmospheric campaign-based water vapour measured by the ground-based microwave radiometer MIAWARA-C

2013 ◽  
Vol 6 (1) ◽  
pp. 1311-1359 ◽  
Author(s):  
B. Tschanz ◽  
C. Straub ◽  
D. Scheiben ◽  
K. A. Walker ◽  
G. P. Stiller ◽  
...  
Keyword(s):  
Water Vapour ◽  
Random Error ◽  
Microwave Radiometer ◽  
Incident Radiation ◽  
Temporal Variations ◽  
The Arctic ◽  
Atmospheric Water ◽  
Data Set ◽  
Atmospheric Water Vapour ◽  
Measurement Campaigns

Abstract. Middle atmospheric water vapour can be used as a tracer for dynamical processes. It is mainly measured by satellite instruments and ground-based microwave radiometers. Ground-based instruments capable of measuring middle atmospheric water vapour are sparse but valuable as they complement satellite measurements, are relatively easy to maintain and have a long lifetime. MIAWARA-C is a ground-based microwave radiometer for middle atmospheric water vapour designed for use on measurement campaigns for both atmospheric case studies and instrument intercomparisons. MIAWARA-C's retrieval version 1.1 (v1.1) is set up in a way to provide a consistent data set even if the instrument is operated from different locations on a campaign basis. The sensitive altitude range for v1.1 extends from 4 hPa (37 km) to 0.017 hPa (75 km). MIAWARA-C measures two polarisations of the incident radiation in separate receiver channels and can therefore provide two independent measurements of the same air mass. The standard deviation of the difference between the profiles obtained from the two polarisations is in excellent agreement with the estimated random error of v1.1. In this paper, the quality of v1.1 data is assessed during two measurement campaigns: (1) five months of measurements in the Arctic (Sodankylä, 67.37° N/26.63° E) and (2) nine months of measurements at mid-latitudes (Zimmerwald, 46.88° N/7.46° E). For both campaigns MIAWARA-C's profiles are compared to measurements from the satellite experiments Aura MLS and MIPAS. In addition, comparisons to ACE-FTS and SOFIE are presented for the Arctic and to the ground-based radiometer MIAWARA for the mid-latitudinal campaign. In general all intercomparisons show high correlation coefficients, above 0.5 at altitudes above 45 km, confirming the ability of MIAWARA-C to monitor temporal variations on the order of days. The biases are generally below 10% and within the estimated systematic uncertainty of MIAWARA-C. No consistent wet or dry bias is identified for MIAWARA-C. In addition, comparisons to the reference instruments indicate the estimated random error of v1.1 to be a realistic measure of the random variation on the retrieved profile.

scholarly journals MAX-DOAS observations of the total atmospheric water vapour column and comparison with independent observations

2012 ◽  
Vol 5 (5) ◽  
pp. 6241-6283 ◽  
Author(s):  
T. Wagner ◽  
M. O. Andreae ◽  
S. Beirle ◽  
S. Dörner ◽  
K. Mies ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Water Vapour ◽  
Satellite Observations ◽  
Shielding Effect ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Water ◽  
Near Surface ◽  
Atmospheric Water Vapour ◽  
Independent Observations ◽  
Good Agreement

Abstract. We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so called geometric approximation and does not depend on a-priori information, extensive radiative transfer simulations, or the construction of large look-up tables. Disturbances of the radiative transfer due to aerosols and clouds are simply corrected using the simultaneously measured absorptions of the oxygen dimer, O4. We applied our algorithm to MAX-DOAS observations made at the Max Planck Institute for Chemistry in Mainz, Germany, from March to August 2011 and compared the results to independent observations. Good agreement with Aerosol Robotic Network (AERONET) and European Centre for Medium-Range Weather Forecasting (ECMWF) H2O vertical column densities (VCDs) is found, while the agreement with satellite observations is less good, most probably caused by the shielding effect of clouds for the satellite observations. Good agreement is also found with near-surface in-situ observations, and it was possible to derive average daily H2O layer heights (between 1.5 km and 3 km). MAX-DOAS measurements use cheap and simple instrumentation and can be run automatically. One important advantage of our algorithm is that the H2O VCD can be retrieved even under cloudy conditions (except clouds with very high optical thickness).

scholarly journals Comparison of ground-based and satellite measurements of water vapour vertical profiles over Ellesmere Island, Nunavut

2018 ◽  
Author(s):  
Dan Weaver ◽  
Kimberly Strong ◽  
Kaley A. Walker ◽  
Chris Sioris ◽  
Matthias Schneider ◽  
...  
Keyword(s):  
Water Vapour ◽  
Atmospheric Chemistry ◽  
Global Climate ◽  
Correlation Coefficients ◽  
High Arctic ◽  
Satellite Measurements ◽  
Solar Absorption ◽  
Comparison Results ◽  
Mean Differences ◽  
Dry Bias

Abstract. Improving measurements of water vapour in the lower stratosphere and upper troposphere (UTLS) is a priority for the atmospheric science community. In this work, UTLS water vapour profiles derived from Atmospheric Chemistry Experiment (ACE) satellite measurements are assessed with coincident ground-based measurements taken at a high Arctic observatory at Eureka, Nunavut, Canada. Additional comparisons to satellite measurements taken by AIRS, MIPAS, MLS, SCIAMACHY, and TES are included to put the ACE-FTS and ACE-MAESTRO results in context. Measurements of water vapour profiles at Eureka are made using a Bruker 125HR solar absorption Fourier transform infrared spectrometer at the Polar Environment Atmospheric Research Laboratory (PEARL) and radiosondes launched from the Eureka Weather Station. Radiosonde measurements used in this study have been processed with software developed by the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) to account for known biases and calculate uncertainties in a well-documented and consistent manner. ACE-FTS measurements were within 11 ppmv (13 %) of 125HR measurements between 6 and 14 km. Between 8 and 14 km ACE-FTS profiles showed a small wet bias of approximately 8 % relative to the 125HR. ACE-FTS water vapour profiles had mean differences of 13 ppmv (32 %) or better when compared to coincident radiosonde profiles at altitudes between 6 and 14 km; mean differences were within 6 ppmv (12 %) between 7 and 11 km. ACE-MAESTRO profiles showed a small dry bias relative to the 125HR of approximately 7 % between 6 and 9 km and 10 % between 10 and 14 km. ACE-MAESTRO profiles agreed within 30 ppmv (36 %) of the radiosondes between 7 and 14 km. ACE-FTS and ACE-MAESTRO comparison results show closer agreement with the radiosondes and PEARL 125HR overall than other satellite datasets – except AIRS. Close agreement was observed between AIRS and the 125HR and radiosonde measurements, with mean differences within 5 % and correlation coefficients above 0.83 in the troposphere between 1 and 7 km. Comparisons to MLS at altitudes around 10 km showed a dry bias, e.g., mean differences between MLS and radiosondes were −25.6 %. SCIAMACHY comparisons were very limited due to minimal overlap between the vertical extent of the measurements. TES had no temporal overlap with the radiosonde dataset used in this study. Comparisons between TES and the 125HR showed a wet bias of approximately 25 % in the UTLS and mean differences within 14 % below 5 km.

scholarly journals Validation of middle-atmospheric campaign-based water vapour measured by the ground-based microwave radiometer MIAWARA-C

2013 ◽  
Vol 6 (7) ◽  
pp. 1725-1745 ◽  
Author(s):  
B. Tschanz ◽  
C. Straub ◽  
D. Scheiben ◽  
K. A. Walker ◽  
G. P. Stiller ◽  
...  
Keyword(s):  
Water Vapour ◽  
Random Error ◽  
Microwave Radiometer ◽  
Incident Radiation ◽  
Temporal Variations ◽  
The Arctic ◽  
Atmospheric Water ◽  
Random Measurement Error ◽  
Data Set ◽  
Atmospheric Water Vapour

Abstract. Middle atmospheric water vapour can be used as a tracer for dynamical processes. It is mainly measured by satellite instruments and ground-based microwave radiometers. Ground-based instruments capable of measuring middle-atmospheric water vapour are sparse but valuable as they complement satellite measurements, are relatively easy to maintain and have a long lifetime. MIAWARA-C is a ground-based microwave radiometer for middle-atmospheric water vapour designed for use on measurement campaigns for both atmospheric case studies and instrument intercomparisons. MIAWARA-C's retrieval version 1.1 (v1.1) is set up in a such way as to provide a consistent data set even if the instrument is operated from different locations on a campaign basis. The sensitive altitude range for v1.1 extends from 4 hPa (37 km) to 0.017 hPa (75 km). For v1.1 the estimated systematic error is approximately 10% for all altitudes. At lower altitudes it is dominated by uncertainties in the calibration, with altitude the influence of spectroscopic and temperature uncertainties increases. The estimated random error increases with altitude from 5 to 25%. MIAWARA-C measures two polarisations of the incident radiation in separate receiver channels, and can therefore provide two measurements of the same air mass with independent instrumental noise. The standard deviation of the difference between the profiles obtained from the two polarisations is in excellent agreement with the estimated random measurement error of v1.1. In this paper, the quality of v1.1 data is assessed for measurements obtained at two different locations: (1) a total of 25 months of measurements in the Arctic (Sodankylä, 67.37° N, 26.63° E) and (2) nine months of measurements at mid-latitudes (Zimmerwald, 46.88° N, 7.46° E). For both locations MIAWARA-C's profiles are compared to measurements from the satellite experiments Aura MLS and MIPAS. In addition, comparisons to ACE-FTS and SOFIE are presented for the Arctic and to the ground-based radiometer MIAWARA for the mid-latitude campaigns. In general, all intercomparisons show high correlation coefficients, confirming the ability of MIAWARA-C to monitor temporal variations of the order of days. The biases are generally below 13% and within the estimated systematic uncertainty of MIAWARA-C. No consistent wet or dry bias is identified for MIAWARA-C. In addition, comparisons to the reference instruments indicate the estimated random error of v1.1 to be a realistic measure of the random variation on the retrieved profile between 45 and 70 km.

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