A Raman lidar tropospheric water vapour climatology and height-resolved trend analysis over Payerne, Switzerland

Abstract

Abstract. Water vapour is the strongest greenhouse gas in our atmosphere, and its strength and its dependence on temperature lead 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 tens of metres, making height-resolved trend analyses possible. Raman water vapour lidars have not typically been used for trend 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 an 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. The climatology shows that the highest water vapour specific-humidity concentrations are in the summer months and the lowest in the winter months. We have also calculated the geophysical variability of water vapour. The percentage of variability of water vapour in the free troposphere is larger than in the boundary layer. We have also determined water vapour trends from 2009 to 2019. We first calculate precipitable water vapour (PWV) trends for comparison with the majority of water vapour trend studies. We detect a nighttime precipitable water vapour trend of 1.3 mm per decade using RALMO measurements, which is significant at the 90 % level. The trend is consistent with a 1.38 ∘C per 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. We compare the nighttime RALMO PWV trend to daytime and nighttime PWV trends using operational radiosonde measurements and find them to agree with each other. We cannot detect a bias between the daytime and nighttime trends due to the large uncertainties in the trends. For the first time, we show height-resolved increases in water vapour through the troposphere. We detect positive tropospheric water vapour trends ranging from a 5 % change in specific humidity per decade to 15 % specific humidity per decade depending on the altitude. The water vapour trends at five layers are statistically significant at or above the 90 % level.

Integrated Water Vapor during Rain and Rain-Free Conditions above the Swiss Plateau

“…Payerne is also a reference site of the Global Climate Observing System (GCOS) (https://www.gruan.org accessed on 10 June 2021). The IWV data of SRS-C50 agree with coincident data of the GCOS Reference Upper-Air Network (GRUAN)-certified radiosondes Vaisala RS92 at Payerne: the mean difference and the standard deviation are 0.8 ± 3.7% [13].…”

“…The radiosondes were launched every day at 11:00 and 23:00 UTC. Until January 2017, the Swiss RadioSonde SRS-C34 was used and later it changed to SRS-C50 [13]. The SRS-C34 is manufactured by MeteoLabor and is equipped with a Sippican hygristor measuring the relative humidity with an accuracy of 2% [14].…”

Evaluation of Arctic Water Vapor Profile Observations from a Differential Absorption Lidar

“…Raman lidars make use of weak inelastic scattering to determine the water vapor mixing ratio (WVMR) [6,7], whereas DIAL systems measure the difference in absorption between two laser wavelengths centered on and off water vapor absorption lines [8]. Raman lidars are a mature technology that have been used for measurements of several atmospheric gases such as water vapor, ozone, carbon dioxide, and various aerosol properties [7,[9][10][11][12]. DIAL technology was accelerated during the NASA Langley DIAL program [13] and it has also been used to measure aerosol properties and several trace gases, including water vapor [14][15][16][17][18][19][20][21].…”

Profiling of Aerosols and Clouds over High Altitude Urban Atmosphere in Eastern Himalaya: A Ground-Based Observation Using Raman LIDAR

“…In another study, automated algorithms were used to retrieve aerosol and humidity parameters along with temperature from Raman LIDAR and radiosonde measurement [50][51][52][53]. The large changes in temperature and water vapor were detected in the first-ever decade-long WVMR profiling performed in Switzerland, Payrene area [54], where the variation in precipitable water vapor was found to be strongly correlated with surface relative humidity.…”