LIDAR Measurements of Stratospheric Aerosols in the Arctic

1992 ◽  
Vol 96 (3) ◽  
pp. 350-353 ◽  
Author(s):  
R. Neuber ◽  
G. Beyerle ◽  
O. Schrems
Keyword(s):  
The Arctic ◽  
Lidar Measurements ◽  
Stratospheric Aerosols

scholarly journals Lidar Measurements of Tropospheric Ozone in the Arctic

2016 ◽  
Vol 119 ◽  
pp. 20003
Author(s):  
Jeffrey Seabrook ◽  
James Whiteway
Keyword(s):  
Tropospheric Ozone ◽  
The Arctic ◽  
Lidar Measurements

scholarly journals Year-round stratospheric aerosol backscatter ratios calculated from lidar measurements above northern Norway

2019 ◽  
Vol 12 (7) ◽  
pp. 4065-4076 ◽  
Author(s):  
Arvid Langenbach ◽  
Gerd Baumgarten ◽  
Jens Fiedler ◽  
Franz-Josef Lübken ◽  
Christian von Savigny ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Stratospheric Aerosol ◽  
New Method ◽  
The Arctic ◽  
Correction Function ◽  
Aerosol Layer ◽  
Radiative Balance ◽  
Northern Norway ◽  
Lidar Measurements ◽  
Aerosol Backscatter

Abstract. We present a new method for calculating backscatter ratios of the stratospheric sulfate aerosol (SSA) layer from daytime and nighttime lidar measurements. Using this new method we show a first year-round dataset of stratospheric aerosol backscatter ratios at high latitudes. The SSA layer is located at altitudes between the tropopause and about 30 km. It is of fundamental importance for the radiative balance of the atmosphere. We use a state-of-the-art Rayleigh–Mie–Raman lidar at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) station located in northern Norway (69∘ N, 16∘ E; 380 m a.s.l.). For nighttime measurements the aerosol backscatter ratios are derived using elastic and inelastic backscatter of the emitted laser wavelengths 355, 532 and 1064 nm. The setup of the lidar allows measurements with a resolution of about 5 min in time and 150 m in altitude to be performed in high quality, which enables the identification of multiple sub-layers in the stratospheric aerosol layer of less than 1 km vertical thickness. We introduce a method to extend the dataset throughout the summer when measurements need to be performed under permanent daytime conditions. For that purpose we approximate the backscatter ratios from color ratios of elastic scattering and apply a correction function. We calculate the correction function using the average backscatter ratio profile at 355 nm from about 1700 h of nighttime measurements from the years 2000 to 2018. Using the new method we finally present a year-round dataset based on about 4100 h of measurements during the years 2014 to 2017.

scholarly journals Heterogeneous chlorine activation on stratospheric aerosols and clouds in the Arctic polar vortex

2012 ◽  
Vol 12 (22) ◽  
pp. 11095-11106 ◽  
Author(s):  
T. Wegner ◽  
J.-U. Grooß ◽  
M. von Hobe ◽  
F. Stroh ◽  
O. Sumińska-Ebersoldt ◽  
...  
Keyword(s):  
Surface Area ◽  
Reaction Rates ◽  
Satellite Observations ◽  
The Arctic ◽  
Good Representation ◽  
Heterogeneous Chemistry ◽  
Annual Variability ◽  
In Situ Observations ◽  
Stratospheric Aerosols

Abstract. Chlorine activation in the Arctic is investigated by examining different parameterizations for uptake coefficients on stratospheric aerosols, high-resolution in-situ measurements and vortex-wide satellite observations. The parameterizations for heterogeneous chemistry on liquid aerosols are most sensitive to temperature with the reaction rates doubling for every 1 K increase in temperature. However, differences between the currently available parameterizations are negligible. For Nitric Acid Trihydrate particles (NAT) the major factors of uncertainty are the number density of nucleated particles and different parameterizations for heterogeneous chemistry. These two factors induce an uncertainty that covers several orders of magnitude on the reaction rate. Nonetheless, since predicted reaction rates on liquid aerosols always exceed those on NAT, the overall uncertainty for chlorine activation is small. In-situ observations of ClOx from Arctic winters in 2005 and 2010 are used to evaluate the heterogeneous chemistry parameterizations. The conditions for these measurements proved to be very different between those two winters with HCl being the limiting reacting partner for the 2005 measurements and ClONO2 for the 2010 measurements. Modeled levels of chlorine activation are in very good agreement with the in-situ observations and the surface area provided by Polar Stratospheric Clouds (PSCs) has only a limited impact on modeled chlorine activation. This indicates that the parameterizations give a good representation of the processes in the atmosphere. Back-trajectories started on the location of the observations in 2005 indicate temperatures on the threshold for PSC formation, hence the surface area is mainly provided by the background aerosol. Still, the model shows additional chlorine activation during this time-frame, providing cautionary evidence for chlorine activation even in the absence of PSCs. Vortex-averaged satellite observations by the MLS instrument also show no definite connection between chlorine activation and PSC formation. The inter -and intra-annual variability of vortex-average HCl and HNO3 based on MLS observations is examined for the Arctic winters 2004/2005 to 2010/2011. These observations show that removal of HCl and HNO3 from the gas-phase are not correlated. HNO3 loss exhibits great inter-annual variability depending on prevailing temperatures while HCl loss is continuous through December without considerable inter- or intra-annual variability. Only the recovery of HCl in late winter depends on the level of denitrification. Hence, the occurrence of HNO3 containing PSC particles does not seem to have a significant effect on the speed of initial chlorine activation on a vortex-wide scale.

scholarly journals Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere

2012 ◽  
Vol 5 (3) ◽  
pp. 4123-4156 ◽  
Author(s):  
J. Hildebrand ◽  
G. Baumgarten ◽  
J. Fiedler ◽  
U.-P. Hoppe ◽  
B. Kaifler ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
The Arctic ◽  
Horizontal Wind ◽  
Small Scale ◽  
Wind Component ◽  
Lower Altitude ◽  
Wind Speeds ◽  
Lidar Measurements ◽  
Wind Measurements ◽  
Good Agreement

Abstract. During a joint campaign in January 2009 the Rayleigh/Mie/Raman (RMR) lidar and the sodium lidar at the ALOMAR Observatory (69° N, 16° E) in Northern Norway were operated simultaneously for more than 40 h, collecting data for wind measurements in the middle atmosphere from 30 up to 110 km altitude. At the upper (lower) altitude range where the RMR (sodium) lidar can operate, both lidars probe the same sounding volume, allowing to compare the derived wind speeds. We present the first simultaneous common volume wind measurements in the middle atmosphere using two different lidar instruments. The comparison of winds derived by RMR and sodium lidar is excellent for long integration times of 10 h as well as shorter ones of 1 h. Combination of data from both lidars allows identifying wavy structures between 30 and 110 km altitude, whose amplitudes increase with height. We have also performed lidar measurements of the same wind component using two independent branches of the RMR lidar and found a good agreement of the results but also identified inhomogeneities in the horizontal wind at about 55 km altitude of up to 20 ms−1. Such small scale inhomogeneities in the horizontal wind field are an essential challenge when comparing data from different instruments.

scholarly journals Radiative fluxes in the High Arctic region derived from ground-based lidar measurements onboard drifting buoys

2021 ◽  
Author(s):  
Lilian Loyer ◽  
Jean-Christophe Raut ◽  
Claudia Di Biagio ◽  
Julia Maillard ◽  
Vincent Mariage ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Optical Depth ◽  
High Arctic ◽  
The Arctic ◽  
Acquisition Time ◽  
Transfer Model ◽  
Cloud Optical Depth ◽  
Lidar Measurements ◽  
Drifting Buoys

Abstract. The Arctic is facing drastic climate changes that are not correctly represented by state-of-the-art models because of complex feedbacks between radiation, clouds and sea-ice surfaces. A better understanding of the surface energy budget requires radiative measurements that are limited in time and space in the High Arctic (> 80° N) and mostly obtained through specific expeditions. Six years of lidar observations onboard buoys drifting in the Arctic Ocean above 83° N have been carried out as part of the IAOOS (Ice Atmosphere arctic Ocean Operating System) project. The objective of this study is to investigate the possibility to extent the IAOOS dataset to provide estimates of the shortwave (SW) and longwave (LW) surface irradiances from lidar measurements on drifting buoys. Our approach relies on the use of the STREAMER radiative transfer model to estimate the downwelling SW scattered radiances from the background noise measured by lidar. Those radiances are then used to derive estimates of the cloud optical depths. In turn, the knowledge of the cloud optical depth enables to estimate the SW and LW (using additional IAOOS measured information) downwelling irradiances at the surface. The method was applied to the IAOOS buoy measurements in spring 2015, and retrieved cloud optical depths were compared to those derived from radiative irradiances measured during the N-ICE (Norwegian Young Sea Ice Experiment) campaign at the meteorological station, in the vicinity of the drifting buoys. Retrieved and measured SW and LW irradiances were then compared. Results showed overall good agreement. Cloud optical depths were estimated with a rather large dispersion of about 47 %. LW irradiances showed a fairly small dispersion (within 5 W m−2), with a corrigible residual bias (3 W m−2). The estimated uncertainty of the SW irradiances was 4 %. But, as for the cloud optical depth, the SW irradiances showed the occurrence of a few outliers, that may be due to a short lidar sequence acquisition time (no more than four times 10 mn per day), possibly not long enough to smooth out cloud heterogeneity. The net SW and LW irradiances are retrieved within 13 W m−2.

scholarly journals Chlorine activation on stratospheric aerosols: uncertainties in parameterizations and surface area

2012 ◽  
Vol 12 (8) ◽  
pp. 20561-20591 ◽  
Author(s):  
T. Wegner ◽  
J.-U. Grooß ◽  
M. von Hobe ◽  
F. Stroh ◽  
O. Sumińska-Ebersoldt ◽  
...  
Keyword(s):  
Surface Area ◽  
Reaction Rates ◽  
Satellite Observations ◽  
The Arctic ◽  
Good Representation ◽  
Heterogeneous Chemistry ◽  
Annual Variability ◽  
In Situ Observations ◽  
Stratospheric Aerosols

Abstract. Chlorine activation in the Arctic is evaluated by examining the different parameterizations for uptake coefficients on stratospheric aerosols, high-resolution in-situ measurements and vortex-wide satellite observations. The parameterizations for heterogeneous chemistry on liquid aerosols are most sensitive to temperature with the reaction rates doubling for each Kelvin increase in temperature. However, differences between the parameterizations are negligible. For Nitric Acid Trihydrate particles (NAT) the major factors of uncertainty are the number density of nucleated particles and different parameterization choices. These two factors induce an uncertainty that covers several orders of magnitude on the reaction rate. But as predicted reaction rates on liquid aerosols always exceed those on NAT the overall uncertainty is small. In-situ observations of ClOx from Arctic winters in 2005 and 2010 are used to validate the heterogeneous chemistry parameterizations. The ambient conditions for these measurements proved to be very different between those two winters with HCl being the limiting reacting partner for the 2005 measurements and ClONO2 for the 2010 measurements. Modeled levels of chlorine activation are in very good agreement with the in-situ observations and the surface area provided by Polar Stratospheric Clouds (PSCs) has only a limited impact on modeled chlorine activation. This indicates that the parameterizations give a good representation of the processes in the atmosphere. Back-trajectories started on the location of the observations in 2005 indicate temperatures on the threshold for PSC formation, hence the surface area is mainly provided by the background aerosol. Still, the model shows additional chlorine activation during this time-frame, providing cautionary evidence for chlorine activation even in the absence of PSCs. Vortex-averaged satellite observations also show no definite connection between chlorine activation and PSC formation. The inter- and intra-annual variability of vortex-average HCl and HNO3 based on MLS observations is examined for the Arctic winters 2004/2005 to 2010/2011. These observations show that removal of HCl and HNO3 from the gas-phase are not correlated. HNO3 loss exhibits great inter-annual variability depending on prevailing temperatures while HCl loss is continuous through December without considerable inter- or intra-annual variability. Only the recovery of HCl in late in winter depends on the level of denitrification. Hence, the occurrence of HNO3 containing PSC particles does not seem to have a significant effect on the speed of initial chlorine activation on a vortex-wide scale.

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