Trends in surface radiation and cloud radiative effect at four Swiss sites for the 1996–2015 period

Nyeki, S.; Wacker, Stefan; Aebi, Christine; Gröbner, Julian; Martucci, Giovanni; Vuilleumier, Laurent

doi:10.5194/acp-2018-1096

Cited by 3 publications

(12 citation statements)

References 23 publications

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“…The 950 hPa temperature trend was statistically significant at 95% with a slope of 1.38±1.41 • C per decade. The temperature trend we measure is larger than that measured by Morland et al (2009) andNyeki et al (2019). However, the percent change in water vapour per degree for all PWV trend values is between 5 -10%, which is consistent with the expected change assuming relative 5 humidity is conserved.…”

Section: Precipitable Water Vapour Trendssupporting

confidence: 83%

“…The RALMO trend is sig-10 nificant above 90% while the radiosonde trends are significant above 95% (Table 1). The trend calculated using all available nighttime radiosonde measurements is slightly smaller than the RALMO PWV trend, but slightly larger than previously calculated trends for Payerne and the region (Morland et al, 2009;Wang et al, 2016;Nyeki et al, 2019).…”

Section: Precipitable Water Vapour Trendscontrasting

confidence: 74%

“…Lidars are well-suited to height-resolved trend measurements and the authors hope that this is the first of many similar studies which will appear over the next few years. We can compare our surface specific humidity trends to the surface water vapour trends measured in Nyeki et al (2019). They measured surface specific humidity trends in Payerne, during cloud-free conditions, of 0.18 and 0.23 g/kg (depending on the method).…”

mentioning

confidence: 97%

“…Morland et al (2009)'s trends were all positive, but no larger than 0.6 mm/decade. Hocke et al (2011) found no trends in water vapour using microwave radiometer PWV measurements from 2004. Nyeki et al (2019 measured temperature and PWV trends from four locations in Switzerland, including the Payerne and Jungfraujoch research stations, with GPS measurements from 1996-2015.…”

mentioning

confidence: 99%

“…We 5 also saw a similar drop in trend magnitude when including all-sky conditions in the radiosonde PWV trend with a change in trend value from 1.34 mm/decade to 1.08 mm/decade. Unlike our analysis which only included nighttime measurements, Nyeki et al (2019) used both daytime and nighttime measurements for the water vapour and temperature trends. Despite this difference, our PWV trends agree within 1σ.…”

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confidence: 99%

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A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

Hicks–Jalali¹,

Sica²,

Haefele³

et al. 2020

Preprint

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Abstract. Water vapour is the strongest greenhouse gas in our atmosphere and its strength and its dependence on temperature leads to a strong feedback mechanism in both the troposphere and the stratosphere. Raman water vapour lidars can be used to make high vertical resolution measurements, on the order of 10s of meters, making height-resolved trend analyses possible. Raman water vapour lidars have not typically been used for trends analyses, primarily due to the lack of long enough time series. However, the RAman Lidar for Meteorological Observations (RALMO), located in Payerne, Switzerland, is capable of making operational water vapour measurements and has one of the longest ground-based and well-characterized data sets available. We have calculated a 11.5-year water vapour climatology using RALMO measurements in the troposphere. Our study uses nighttime measurements during mostly clear conditions, which creates a natural selection bias. We have also calculated the geophysical variability of water vapour. The climatology shows that the highest water vapour specific humidity concentrations are in the summer months, and the lowest in the winter months. The percent variability of water vapour in the free troposphere is larger than of the boundary layer. We have also determined water vapour trends from 2009&#8211;2019. We first calculate precipitable water vapour trends for comparison with the majority of water vapour trend studies. We detect a precipitable water vapour trend of 2.1&#8201;mm/decade using RALMO measurements, which is significant at the 90&#8201;% level. The trend is consistent with a 1.38&#8201;&#176;C/decade surface temperature trend detected by coincident radiosonde measurements under the assumption that relative humidity remains constant;however, it is larger than previous water vapour trend values. For the first time, we show height-resolved increases in water vapour through the troposphere. We detect positive tropospheric water vapour trends ranging from 5% change in specific humidity per decade to 15% specific humidity per decade depending on the altitude. The water vapour trends at 5 layers are statistically significant at or above the 90% level.

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Section: Precipitable Water Vapour Trendssupporting

confidence: 83%

Section: Precipitable Water Vapour Trendscontrasting

confidence: 74%

mentioning

confidence: 97%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

Hicks–Jalali¹,

Sica²,

Haefele³

et al. 2020

Preprint

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

Bernet¹,

Bröckmann²,

Clarmann³

et al. 2020

Preprint

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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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Long-term energy balance measurements at three different mountain permafrost sites in the Swiss Alps

Hoelzle

Hauck

Mathys

et al. 2022

Earth Syst. Sci. Data

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Abstract. The surface energy balance is a key factor influencing the ground thermal regime. With ongoing climate change, it is crucial to understand the interactions of the individual heat fluxes at the surface and within the subsurface layers, as well as their relative impacts on the permafrost thermal regime. A unique set of high-altitude meteorological measurements was analysed to determine the energy balance at three mountain permafrost sites in the Swiss Alps (Murtèl–Corvatsch, Schilthorn and Stockhorn), where data have been collected since the late 1990s in the framework of the Swiss Permafrost Monitoring Network (PERMOS). All stations are equipped with sensors for four-component radiation, air temperature, humidity, and wind speed and direction, as well as ground temperatures and snow height. The three sites differ considerably in their surface and ground material composition, as well as their ground ice contents. The energy fluxes were calculated based on two decades of field measurements. While the determination of the radiation budget and the ground heat flux is comparatively straightforward (by the four-component radiation sensor and thermistor measurements within the boreholes), larger uncertainties exist for the determination of turbulent sensible and latent heat fluxes. Our results show that mean air temperature at Murtèl–Corvatsch (1997–2018, 2600 m a.s.l.) is −1.66 ∘C and has increased by about 0.8 ∘C during the measurement period. At the Schilthorn site (1999–2018, 2900 m a.s.l.) a mean air temperature of −2.60 ∘C with a mean increase of 1.0 ∘C was measured. The Stockhorn site (2003–2018, 3400 m a.s.l.) recorded lower air temperatures with a mean of −6.18 ∘C and an increase of 0.5 ∘C. Measured net radiation, as the most important energy input at the surface, shows substantial differences with mean values of 30.59 W m−2 for Murtèl–Corvatsch, 32.40 W m−2 for Schilthorn and 6.91 W m−2 for Stockhorn. The calculated turbulent fluxes show values of around 7 to 13 W m−2 using the Bowen ratio method and 3 to 15 W m−2 using the bulk method at all sites. Large differences are observed regarding the energy used for the melting of the snow cover: at Schilthorn a value of 8.46 W m−2, at Murtèl–Corvatsch 4.17 W m−2 and at Stockhorn 2.26 W m−2 are calculated, reflecting the differences in snow height at the three sites. In general, we found considerable differences in the energy fluxes at the different sites. These differences help to explain and interpret the causes of a warming atmosphere. We recognise a strong relation between the net radiation and the ground heat flux. Our results further demonstrate the importance of long-term monitoring to better understand the impacts of changes in the surface energy balance components on the permafrost thermal regime. The dataset presented can be used to improve permafrost modelling studies aiming at, for example, advancing knowledge about permafrost thaw processes. The data presented and described here are available for download at the following site: https://doi.org/10.13093/permos-meteo-2021-01 (Hoelzle et al., 2021).

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Trends in surface radiation and cloud radiative effect at four Swiss sites for the 1996–2015 period

Cited by 3 publications

References 23 publications

A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

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

Long-term energy balance measurements at three different mountain permafrost sites in the Swiss Alps

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