Tropospheric water vapour above Switzerland over the last 12 years

Abstract. Integrated Water vapour (IWV) has been measured since 1994 by the TROWARA microwave radiometer in Bern, Switzerland. Homogenization techniques were used to identify and correct step changes in IWV related to instrument problems. IWV from radiosonde, GPS and sun photometer (SPM) was used in the homogenisation process as well as partial IWV columns between valley and mountain weather stations. The average IWV of the homogenised TROWARA time series was 14.4 mm over the 1996–2007 period, with maximum and minimum monthly average values of 22.4 mm and 8 mm occurring in August and January, respectively. A weak diurnal cycle in TROWARA IWV was detected with an amplitude of 0.32 mm, a maximum at 21:00 UT and a minimum at 11:00 UT. For 1996–2007, TROWARA trends were compared with those calculated from the Payerne radiosonde and the closest ECMWF grid point to Bern. Using least squares analysis, the IWV time series of radiosondes at Payerne, ECMWF, and TROWARA showed consistent positive trends from 1996 to 2007. The radiosondes measured an IWV trend of 0.45±0.29%/y, the TROWARA radiometer observed a trend of 0.39±0.44%/y, and ECMWF operational analysis gave a trend of 0.25±0.34%/y. Since IWV has a strong and variable annual cycle, a seasonal trend analysis (Mann-Kendall analysis) was also performed. The seasonal trends are stronger by a factor 10 or so compared to the full year trends above. The positive IWV trends of the summer months are partly compensated by the negative trends of the winter months. The strong seasonal trends of IWV on regional scale underline the necessity of long-term monitoring of IWV for detection,understanding, and forecast of climate change effects in the Alpine region.

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Tropospheric water vapour above Switzerland over the last 12 years

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-7239-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 7239-7271 ◽

Cited By ~ 3

Author(s):

J. Morland ◽

M. Collaud Coen ◽

K. Hocke ◽

P. Jeannet ◽

C. Mätzler

Keyword(s):

Water Vapour ◽

Grid Point ◽

Microwave Radiometer ◽

Negative Trend ◽

Positive Trend ◽

Significant Positive Trend ◽

Significant Negative Trend ◽

Integrated Water Vapour ◽

Weather Stations ◽

Homogenisation Process

Abstract. Integrated Water vapour (IWV) has been measured since 1994 by the TROWARA microwave radiometer in Bern, Switzerland. Homogenization techniques were used to identify and correct step changes in IWV related to instrument problems. IWV from radiosonde, GPS and SPM was used in the homogenisation process as well as the IWV differences calculated between mountain and valley weather stations. The average IWV of the homogenised TROWARA time series was 14.4 mm over the 1996–2007 period, with maximum and minimum monthly average values of 22.4 mm and 8 mm occurring in August and January, respectively. A weak diurnal cycle in TROWARA IWV was detected with an amplitude of 0.32 mm, a maximum at 21:00 UT and a minimum at 11:00 UT. For 1996–2007, TROWARA trends were compared with those calculated from the Payerne radiosonde and the closest ECMWF grid point to Bern. The radiosonde midnight trend of +0.087 (standard error 0.046) mm/y was significant at the 90% level. The radiosonde trend for all measurement times, +0.098 (0.061) mm/y, and the TROWARA midday trends, 0.068 (0.043) mm/y, were significant at the 89% level. Seasonal Mann Kendall analysis revealed a significant positive trend in July of +0.19 (0.14) to +0.34 (0.25) mm/y for all three datasets. In December, the Payerne radiosonde showed a non-significant negative trend of −0.12 (0.13) mm/y, whilst ECMWF and TROWARA indicated a significant negative trend of −0.20 (0.14) and −0.36 (0.24) mm/y, respectively.

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Interpreting the time variability of world-wide GPS and GOME/SCIAMACHY integrated water vapour retrievals, using reanalyses as auxiliary tools

10.5194/acp-2018-1170 ◽

2018 ◽

Author(s):

Roeland Van Malderen ◽

Eric Pottiaux ◽

Gintautas Stankunavicius ◽

Steffen Beirle ◽

Thomas Wagner ◽

...

Keyword(s):

Time Series ◽

Linear Regression ◽

Multiple Linear Regression ◽

Water Vapour ◽

Southern Oscillation ◽

Linear Trend ◽

Time Variability ◽

The North ◽

Integrated Water Vapour

Abstract. This study investigates different aspects of the Integrated Water Vapour (IWV) variability at 118 globally distributed Global Positioning System (GPS) sites, using additionally UV/VIS satellite retrievals by GOME, SCIAMACHY and GOME-2 (denoted as GOMESCIA below), and ERA-Interim reanalysis output at these site locations. Apart from some spatial representativeness issues at especially coastal and island sites, those three datasets correlate rather well, the lowest correlation found between GPS and GOMESCIA (0.865 on average). In this paper, we first study the geographical distribution of the frequency distributions of the IWV time series, and subsequently analyse the seasonal IWV cycle and linear trend differences among the three different datasets. Finally, both the seasonal behaviour and the long-term variability are fitted together by means of a stepwise multiple linear regression of the station’s time series, with a selection of regionally dependent candidate explanatory variables. Overall, the variables that are most frequently used and explain the largest fractions of the IWV variability are the surface temperature and precipitation. Also the surface pressure and tropopause pressure (in particular for higher latitude sites) are important contributors to the IWV time variability. All these variables also seem to account for the sign of long-term trend in the IWV time series to a large extent, when considered as explanatory variable. Furthermore, the multiple linear regression linked the IWV variability at some particular regions to teleconnection patterns or climate/oceanic indices like the North Oscillation index for West USA, the El Niňo Southern Oscillation (ENSO) for East Asia, the East Atlantic (associated with the North Atlantic Oscillation, NAO) index for Europe.

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Quantifying the value of redundant measurements at GCOS Reference Upper-Air Network sites

Atmospheric Measurement Techniques ◽

10.5194/amt-7-3813-2014 ◽

2014 ◽

Vol 7 (11) ◽

pp. 3813-3823 ◽

Cited By ~ 3

Author(s):

F. Madonna ◽

M. Rosoldi ◽

J. Güldner ◽

A. Haefele ◽

R. Kivi ◽

...

Keyword(s):

Time Series ◽

Water Vapour ◽

Global Climate ◽

Microwave Radiometer ◽

Raman Lidar ◽

Mutual Correlation ◽

Random Uncertainty ◽

Lidar Measurements ◽

Integrated Water Vapour ◽

Microwave Radiometers

Abstract. The potential for measurement redundancy to reduce uncertainty in atmospheric variables has not been investigated comprehensively for climate observations. We evaluated the usefulness of entropy and mutual correlation concepts, as defined in information theory, for quantifying random uncertainty and redundancy in time series of the integrated water vapour (IWV) and water vapour mixing ratio profiles provided by five highly instrumented GRUAN (GCOS, Global Climate Observing System, Reference Upper-Air Network) stations in 2010–2012. Results show that the random uncertainties on the IWV measured with radiosondes, global positioning system, microwave and infrared radiometers, and Raman lidar measurements differed by less than 8%. Comparisons of time series of IWV content from ground-based remote sensing instruments with in situ soundings showed that microwave radiometers have the highest redundancy with the IWV time series measured by radiosondes and therefore the highest potential to reduce the random uncertainty of the radiosondes time series. Moreover, the random uncertainty of a time series from one instrument can be reduced by ~ 60% by constraining the measurements with those from another instrument. The best reduction of random uncertainty is achieved by conditioning Raman lidar measurements with microwave radiometer measurements. Specific instruments are recommended for atmospheric water vapour measurements at GRUAN sites. This approach can be applied to the study of redundant measurements for other climate variables.

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Trends of atmospheric water vapour in Switzerland from ground-based radiometry, FTIR and GNSS data

10.5194/acp-2020-77 ◽

2020 ◽

Author(s):

Leonie Bernet ◽

Elmar Brockmann ◽

Thomas von Clarmann ◽

Niklaus Kämpfer ◽

Emmanuel Mahieu ◽

...

Keyword(s):

Water Vapour ◽

Microwave Radiometer ◽

Regional Scale ◽

Satellite System ◽

Reanalysis Data ◽

Temperature Relation ◽

Integrated Water Vapour ◽

Projected Changes ◽

Global Navigation Satellite ◽

Gnss Data

Abstract. Vertically integrated water vapour (IWV) is expected to increase globally in a warming climate. To determine whether IWV increases as expected on a regional scale, we present IWV trends in Switzerland from ground-based remote sensing techniques and reanalysis models, considering data for the time period 1995 to 2018. We estimate IWV trends from a ground-based microwave radiometer in Bern, from a Fourier Transform Infrared (FTIR) spectrometer at Jungfraujoch, from reanalysis data (ERA5 and MERRA-2) and from Swiss ground-based Global Navigation Satellite System (GNSS) stations. Using a straightforward trend method, we account for jumps in the GNSS data, which are highly sensitive to instrumental changes. We found that IWV generally increased by 2 to 5 % per decade, with deviating trends at some GNSS stations. Trends were significantly positive at 23 % of all GNSS stations, which often lie at higher altitudes (between 850 and 1700 m above sea level). Our results further show that IWV in Bern scales to air temperature as expected (except in winter), but the IWV–temperature relation based on reanalysis data in whole Switzerland is not everywhere clear. In addition to our positive IWV trends, we found that the radiometer in Bern agrees within 5 % with GNSS and reanalyses. At the high altitude station Jungfraujoch, we found a mean difference of 0.26 mm (15 %) between the FTIR and coincident GNSS data, improving to 4 % after an antenna update in 2016. In general, we showed that ground-based GNSS data are highly valuable for climate monitoring, given that the data have been homogeneously reprocessed and that instrumental changes are accounted for. We found a response of IWV to rising temperature in Switzerland, which is relevant for projected changes in local cloud and precipitation processes.

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Trends of atmospheric water vapour in Switzerland from ground-based radiometry, FTIR and GNSS data

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11223-2020 ◽

2020 ◽

Vol 20 (19) ◽

pp. 11223-11244 ◽

Cited By ~ 1

Author(s):

Leonie Bernet ◽

Elmar Brockmann ◽

Thomas von Clarmann ◽

Niklaus Kämpfer ◽

Emmanuel Mahieu ◽

...

Keyword(s):

Water Vapour ◽

Microwave Radiometer ◽

Regional Scale ◽

Satellite System ◽

Reanalysis Data ◽

Temperature Relation ◽

Integrated Water Vapour ◽

Projected Changes ◽

Global Navigation Satellite ◽

Gnss Data

Abstract. Vertically integrated water vapour (IWV) is expected to increase globally in a warming climate. To determine whether IWV increases as expected on a regional scale, we present IWV trends in Switzerland from ground-based remote sensing techniques and reanalysis models, considering data for the time period 1995 to 2018. We estimate IWV trends from a ground-based microwave radiometer in Bern, from a Fourier transform infrared (FTIR) spectrometer at Jungfraujoch, from reanalysis data (ERA5 and MERRA-2) and from Swiss ground-based Global Navigation Satellite System (GNSS) stations. Using a straightforward trend method, we account for jumps in the GNSS data, which are highly sensitive to instrumental changes. We found that IWV generally increased by 2 % per decade to 5 % per decade, with deviating trends at some GNSS stations. Trends were significantly positive at 17 % of all GNSS stations, which often lie at higher altitudes (between 850 and 1650 m above sea level). Our results further show that IWV in Bern scales to air temperature as expected (except in winter), but the IWV–temperature relation based on reanalysis data in the whole of Switzerland is not clear everywhere. In addition to our positive IWV trends, we found that the radiometer in Bern agrees within 5 % with GNSS and reanalyses. At the Jungfraujoch high-altitude station, we found a mean difference of 0.26 mm (15 %) between the FTIR and coincident GNSS data, improving to 4 % after an antenna update in 2016. In general, we showed that ground-based GNSS data are highly valuable for climate monitoring, given that the data have been homogeneously reprocessed and that instrumental changes are accounted for. We found a response of IWV to rising temperature in Switzerland, which is relevant for projected changes in local cloud and precipitation processes.

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Drifting Effects of NOAA Satellites on Long-Term Active Fire Records of Europe

Remote Sensing ◽

10.3390/rs11040467 ◽

2019 ◽

Vol 11 (4) ◽

pp. 467 ◽

Cited By ~ 3

Author(s):

Helga Weber ◽

Stefan Wunderle

Keyword(s):

Time Series ◽

Explicit Knowledge ◽

Regional Scale ◽

Error Sources ◽

Fire Cycle ◽

Active Fire ◽

Maximum Delay ◽

Orbital Drift ◽

The Impact

Explicit knowledge of different error sources in long-term climate records from space is required to understand and mitigate their impacts on resulting time series. Imagery of the heritage Advanced Very High Resolution Radiometer (AVHRR) provides unique potential for climate research dating back to the 1980s, flying onboard a series of successive National Oceanic and Atmospheric Administration (NOAA) and Meteorological Operational (MetOp) satellites. However, the NOAA satellites are affected by severe orbital drift that results in spurious trends in time series. We identified the impact and extent of the orbital drift in 1 km AVHRR long-term active fire data. This record contains data of European fire activity from 1985–2016 and was analyzed on a regional scale and extended across Europe. Inconsistent sampling of the diurnal active fire cycle due to orbital drift with a maximum delay of ∼5 h over NOAA-14 lifetime revealed a ∼90% decline in the number of observed fires. However, interregional results were less conclusive and other error sources as well as interannual variability were more pronounced. Solar illumination, measured by the sun zenith angle (SZA), related changes in background temperatures were significant for all regions and afternoon satellites with major changes in −0.03 to −0.09 K deg − 1 for ▵ B T 34 (p ≤ 0 . 001). Based on example scenes, we simulated the influence of changing temperatures related to changes in the SZA on the detection of active fires. These simulations showed a profound influence of the active fire detection capabilities dependent on biome and land cover characteristics. The strong decrease in the relative changes in the apparent number of active fires calculated over the satellites lifetime highlights that a correction of the orbital drift effect is essential even over short time periods.

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Water vapour retrieval using the Precision Solar Spectroradiometer

Atmospheric Measurement Techniques ◽

10.5194/amt-11-1143-2018 ◽

2018 ◽

Vol 11 (2) ◽

pp. 1143-1157 ◽

Cited By ~ 4

Author(s):

Panagiotis-Ioannis Raptis ◽

Stelios Kazadzis ◽

Julian Gröbner ◽

Natalia Kouremeti ◽

Lionel Doppler ◽

...

Keyword(s):

Water Vapour ◽

Single Channel ◽

Microwave Radiometer ◽

Coefficient Of Determination ◽

High Temporal Resolution ◽

Spectral Approach ◽

Spectral Measurements ◽

Data Set ◽

Integrated Water Vapour ◽

Relative Differences

Abstract. The Precision Solar Spectroradiometer (PSR) is a new spectroradiometer developed at Physikalisch-Meteorologisches Observatorium Davos – World Radiation Center (PMOD–WRC), Davos, measuring direct solar irradiance at the surface, in the 300–1020 nm spectral range and at high temporal resolution. The purpose of this work is to investigate the instrument's potential to retrieve integrated water vapour (IWV) using its spectral measurements. Two different approaches were developed in order to retrieve IWV: the first one uses single-channel and wavelength measurements, following a theoretical water vapour high absorption wavelength, and the second one uses direct sun irradiance integrated at a certain spectral region. IWV results have been validated using a 2-year data set, consisting of an AERONET sun-photometer Cimel CE318, a Global Positioning System (GPS), a microwave radiometer profiler (MWP) and radiosonde retrievals recorded at Meteorological Observatorium Lindenberg, Germany. For the monochromatic approach, better agreement with retrievals from other methods and instruments was achieved using the 946 nm channel, while for the spectral approach the 934–948 nm window was used. Compared to other instruments' retrievals, the monochromatic approach leads to mean relative differences up to 3.3 % with the coefficient of determination (R2) being in the region of 0.87–0.95, while for the spectral approach mean relative differences up to 0.7 % were recorded with R2 in the region of 0.96–0.98. Uncertainties related to IWV retrieval methods were investigated and found to be less than 0.28 cm for both methods. Absolute IWV deviations of differences between PSR and other instruments were determined the range of 0.08–0.30 cm and only in extreme cases would reach up to 15 %.

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Statistical analyses and correlation between tropospheric temperature and humidity at Dome C, Antarctica

Antarctic Science ◽

10.1017/s0954102013000564 ◽

2013 ◽

Vol 26 (3) ◽

pp. 290-308 ◽

Cited By ~ 4

Author(s):

P. Ricaud ◽

F. Carminati ◽

Y. Courcoux ◽

A. Pellegrini ◽

J.-L. Attié ◽

...

Keyword(s):

Water Vapour ◽

Pearson Correlation ◽

Microwave Radiometer ◽

Weather Forecast ◽

Tropospheric Temperature ◽

Infrared Sensors ◽

Atmospheric Infrared Sounder ◽

Medium Range Weather Forecast ◽

Integrated Water Vapour ◽

Highly Correlated

AbstractThe Dome C (Concordia) station in Antarctica (75°06′S, 123°21′E, 3233 m above mean sea level) has a unique opportunity to test the quality of remote-sensing measurements and meteorological analyses because it is situated well inside the Eastern Antarctic Plateau and is less affected by local phenomena. Measurements of tropospheric temperature and water vapour (H2O) together with the integrated water vapour (IWV) performed in 2010 are statistically analysed to assess their quality and to study the yearly correlation between temperature and H2O over the entire troposphere. The statistical tools include yearly evolution, seasonally-averaged mean and bias, standard deviation and linear Pearson correlation. The datasets are made of measurements from the ground-based microwave radiometer H2O Antarctica Microwave Stratospheric and Tropospheric Radiometer (HAMSTRAD), radiosonde, in situ sensors, the space-borne infrared sensors Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A platform and the Atmospheric InfraRed Sounder (AIRS) on the Aqua platform, and the analyses from the European Centre for Medium-Range Weather Forecast (ECMWF). Despite some obvious biases within all these datasets, our study shows that temperature and IWV are generally measured with high quality whilst H2O measurement quality is slightly worse. The AIRS and IASI measurements do not have the vertical resolution to correctly probe the lowermost troposphere, whilst HAMSTRAD loses sensitivity in the upper troposphere-lower stratosphere. Within the entire troposphere over the whole year, it is found that the time evolution of temperature and H2O is highly correlated (> 0.8). This suggests that, in addition to the variability of solar radiation producing an obvious diurnal cycle in the planetary boundary layer in summer and an obvious seasonal cycle over the year, the H2O and temperature intra-seasonal variabilities are affected by the same processes, e.g. related to the long-range transport of air masses.

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Analysis of global water vapour trends from satellite measurements in the visible spectral range

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-11761-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 11761-11796 ◽

Cited By ~ 2

Author(s):

S. Mieruch ◽

S. Noël ◽

H. Bovensmann ◽

J. P. Burrows

Keyword(s):

Time Series ◽

Water Vapour ◽

Statistical Significance ◽

Visible Spectral Range ◽

Optical Absorption Spectroscopy ◽

Data Set ◽

Factors Affecting ◽

Scanning Imaging ◽

Global Water

Abstract. Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME) flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data, on Metop. Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O contents and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes of water vapour columns distributed over the whole globe.

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A multi-site techniques intercomparison of integrated water vapour observations for climate change analysis

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-1075-2014 ◽

2014 ◽

Vol 7 (2) ◽

pp. 1075-1151 ◽

Cited By ~ 3

Author(s):

R. Van Malderen ◽

H. Brenot ◽

E. Pottiaux ◽

S. Beirle ◽

C. Hermans ◽

...

Keyword(s):

Climate Change ◽

Water Vapour ◽

Dominant Role ◽

Satellite System ◽

International Gnss Service ◽

Change Analysis ◽

Integrated Water Vapour ◽

Sun Photometer ◽

The Impact

Abstract. Water vapour plays a dominant role in the climate change debate. However, observing water vapour over a climatological time period in a consistent and homogeneous manner is challenging. At one hand, networks of ground-based instruments allowing to retrieve homogeneous Integrated Water Vapour (IWV) datasets are being set up. Typical examples are Global Navigation Satellite System (GNSS) observation networks such as the International GNSS Service (IGS), with continuous GPS (Global Positioning System) observations spanning over the last 15+ yr, and the AErosol RObotic NETwork (AERONET), providing long-term observations performed with standardized and well-calibrated sun photometers. On the other hand, satellite-based measurements of IWV already have a time span of over 10 yr (e.g. AIRS) or are being merged in order to create long-term time series (e.g. GOME, SCIAMACHY, and GOME-2). The present study aims at setting up a techniques intercomparison of IWV measurements from satellite devices (in the visible, GOME/SCIAMACHY/GOME-2, and in the thermal infrared, AIRS), in-situ measurements (radiosondes) and ground-based instruments (GPS, sun photometer), to assess the applicability of either dataset for water vapour trends analysis. To this end, we selected 28 sites worldwide at which GPS observations can directly be compared with coincident satellite IWV observations, together with sun photometer and/or radiosonde measurements. We found that the mean biases of the different techniques w.r.t. the GPS estimates vary only between −0.3 to 0.5 mm of IWV, but the small bias is accompanied by large Root Mean Square (RMS) values, especially for the satellite instruments. In particular, we analysed the impact of the presence of clouds on the techniques IWV agreement. Also, the influence of specific issues for each instrument on the intercomparison is investigated, e.g. the distance between the satellite ground pixel centre and the co-located ground-based station, the satellite scan angle, daytime/nighttime differences, etc. Furthermore, we checked if the properties of the IWV scatter plots between these different instruments are dependent on the geography and/or altitude of the station. We could only detect a clear dependency of the RMS, for all considered instruments, on latitude or mean IWV: the RMS of the IWV observations w.r.t. the GPS IWV retrievals decreases with increasing latitude and decreasing mean IWV.

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