[Show abstract][Hide abstract] ABSTRACT: We present high-resolution measurements of water vapour, aerosols and
clouds in the Arctic stratosphere in January and February 2010 carried
out by in-situ instrumentation on balloon-sondes and high-altitude
aircraft combined with satellite observations. The measurements provide
unparalleled evidence of dehydration and rehydration due to
gravitational settling of ice particles. An extreme cooling of the
Arctic stratospheric vortex during the second half of January 2010
resulted in a rare synoptic-scale outbreak of ice PSCs (polar
stratospheric clouds) detected remotely by the lidar aboard the CALIPSO
satellite. The widespread occurrence of ice clouds was followed by
sedimentation and consequent sublimation of ice particles, leading to
vertical redistribution of water inside the vortex. A sequence of
balloon and aircraft soundings with chilled mirror and Lyman-α
hygrometers (CFH, FISH, FLASH) and backscatter sondes (COBALD) conducted
in January 2010 within the LAPBIAT and RECONCILE campaigns captured
various phases of this phenomenon: ice formation, irreversible
dehydration and rehydration. Consistent observations of water vapour by
these independent measurement techniques show clear signatures of
irreversible dehydration of the vortex air by up to 1.6 ppmv in the
20-24 km altitude range and rehydration by up to 0.9 ppmv in a 1
km-thick layer below. Comparison with space-borne Aura MLS water vapour
observations allow the spatiotemporal evolution of dehydrated air masses
within the Arctic vortex to be derived and upscaled.
[Show abstract][Hide abstract] ABSTRACT: The international research project RECONCILE has addressed central questions regarding polar ozone depletion, with the objective to quantify some of the most relevant yet still uncertain physical and chemical processes and thereby improve prognostic modelling capabilities to realistically predict the response of the ozone layer to climate change. This overview paper outlines the scope and the general approach of RECONCILE, and it provides a summary of observations and modelling in 2010 and 2011 that have generated an in many respects unprecedented dataset to study processes in the Arctic winter stratosphere. Principally, it summarises important outcomes of RECONCILE including (i) better constraints and enhanced consistency on the set of parameters governing catalytic ozone destruction cycles, (ii) a better understanding of the role of cold binary aerosols in heterogeneous chlorine activation, (iii) an improved scheme of polar stratospheric cloud (PSC) processes that includes heterogeneous nucleation of nitric acid trihydrate (NAT) and ice on non-volatile background aerosol leading to better model parameterisations with respect to denitrification, and (iv) long transient simulations with a chemistry-climate model (CCM) updated based on the results of RECONCILE that better reproduce past ozone trends in Antarctica and are deemed to produce more reliable predictions of future ozone trends. The process studies and the global simulations conducted in RECONCILE show that in the Arctic, ozone depletion uncertainties in the chemical and microphysical processes are now clearly smaller than the sensitivity to dynamic variability.
[Show abstract][Hide abstract] ABSTRACT: Stratospheric chemistry and denitrification are simulated for the Arctic
winter 2009/2010 with the Lagrangian Chemistry and Transport Model
ATLAS. A number of sensitivity runs is used to explore the impact of
uncertainties in chlorine activation and denitrification on the model
results. In particular, the efficiency of chlorine activation on
different types of liquid aerosol versus activation on nitric acid
trihydrate clouds is examined. Additionally, the impact of changes in
reaction rate coefficients, in the particle number density of polar
stratospheric clouds, in supersaturation, temperature or the extent of
denitrification is investigated. Results are compared to satellite
measurements of MLS and ACE-FTS and to in-situ measurements onboard the
Geophysica aircraft during the RECONCILE measurement campaign. It is
shown that even large changes in the underlying assumptions have only a
small impact on the modeled ozone loss, even though they can cause
considerable differences in chemical evolution and denitrification. In
addition, it is shown that chlorine activation on liquid aerosols alone
is able to explain the observed magnitude and morphology of the mixing
ratios of active chlorine, reservoir gases and ozone.
[Show abstract][Hide abstract] ABSTRACT: Abstract. The atmospheric ozone plays an important role in understanding of the processes occurring in the atmosphere and changes in the climate. Total ozone observations in Siberia were performed by Brewer MKIV No. 049 spectrophotometer in Tomsk, Western Siberia and SAOZ UV-Vis spectrometers deployed along the Arctic Circle in Salekhard aerological station since 1998 and Zhigansk aerological station in Eastern Siberia since 1991. We also use 2Z-ECC ozonesondes for ozone profile observations in winter–spring period at the Salekhard aerological station at the in Western Siberia and ECC-6A sondes at the drifting North Pole station NP-38 in the Central Arctic area. During the winter–spring season in 2011, Arctic ozone in the 19–21 km altitude region was observed to be more than 70% less that typical values. In the winter–spring of 2012, on the other hand, Arctic conditions were overall much warmer than in 2011, and no evidence of significant ozone loss was seen above the Asiatic regions of Russian Federation.
[Show abstract][Hide abstract] ABSTRACT: This paper describes a fluorescence hygrometer for measuring the microconcentration of water vapor in the stratosphere. The vacuum ultraviolet sources to be used in the hygrometer are considered. Questions of the temperature dependence of the characteristics of hydrogen and krypton glow-discharge lamps are discussed, as well as the operation of the lamps in the modulation regime. The results of laboratory and field tests of the hygrometer are presented.
Journal of Optical Technology c/c of Opticheskii Zhurnal 08/2012; 79(8). DOI:10.1364/JOT.79.000515 · 0.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: SAOZ (Systeme d'Analyse par Observation Zenitale) is a UV-visible diode
array spectrometer developed at the Service d'Aeronomie, CNRS, France in
the late 80s for monitoring stratospheric ozone (O3) and nitrogen
dioxide (NO2). It is now manufactured at the Laboratory for Atmospheric
Research (LATMOS) for measuring total atmospheric ozone, nitrogen
dioxide and some other atmospheric trace gases (BrO, O4). The
spectrometer uses the technique of measurements in the ultraviolet and
visible wavelengths of sun in the registration of the zenith sky. The
wavelength range of the SAOZ instrument is in Chappuis band of ozone
absorption, with a spectral resolution of 1 nm for version V-1024, and
0.7 nm for the new Mini-SAOZ version V-2048. Measurement accuracy is 6%
for total ozone and 10% for nitrogen dioxide. Data for the atmospheric
content of O3 and NO2 measured by SAOZ spectrometers are available at
the World SAOZ database, http://saoz.obs.uvsq.fr/SAOZ-RT.html, since
1988 from Dumont d'Urville station in the Southern Hemisphere, since
1989 from the Sodankyla observatory in Finland, and from additional SAOZ
stations in 1990-1991. The first Asiatic SAOZ station started operation
in 1991 at Zhigansk, East Siberia, Russia. A SAOZ spectrometer has been
operating at Salekhard station, West Siberia, Russia since 1997. The new
SAOZ UV-visible instrument is used to measure atmospheric trace gases in
the polar area of the Russian Far East for the first time. The resulting
total ozone and nitrogen dioxide measurements from the new model V-2048
Mini-SAOZ UV-visible spectrometer at the Hydrometeorological observatory
Anadyr in all seasons of 2011 will be shown and discussed.
[Show abstract][Hide abstract] ABSTRACT: The dynamical evolution of the relatively warm stratospheric winter season 2002–2003 in the Northern Hemisphere was studied and compared with the cold winter 2004–2005 based on NCEP-Reanalyses. Record low temperatures were observed in the lower and middle stratosphere over the Arctic region only at the beginning of the 2002–2003 winter. Six sudden stratospheric warming events, including the major warming event with a splitting of the polar vortex in mid-January 2003, have been identified. This led to a very high vacillation of the zonal mean circulation and a weakening of the stratospheric polar vortex over the whole winter season. An estimate of the mean chemical ozone destruction inside the polar vortex showed a total ozone loss of about 45 DU in winter 2002–2003; that is about 2.5 times smaller than in winter 2004–2005. Embedded in a winter with high wave activity, we found two subtropical Rossby wave trains in the troposphere before the major sudden stratospheric warming event in January 2003. These Rossby waves propagated north-eastwards and maintained two upper tropospheric anticyclones. At the same time, the amplification of an upward propagating planetary wave 2 in the upper troposphere and lower stratosphere was observed, which could be caused primarily by those two wave trains. Furthermore, two extratropical Rossby wave trains over the North Pacific Ocean and North America were identified a couple of days later, which contribute mainly to the vertical planetary wave activity flux just before and during the major warming event. It is shown that these different tropospheric forcing processes caused the major warming event and contributed to the splitting of the polar vortex.
[Show abstract][Hide abstract] ABSTRACT: The participation of Russian specialists in the international programs on balloon investigations of the ozone layer in the
Arctic and in midlatitudes has been carried out since 1991. The specialists of Roshydromet took part in the organization and
implementation of investigations in the Arctic and in midlatitudes within 11 projects as well as in tropical balloon campaigns.
During this period, 42 balloon flights of different types were organized on the territory of Russia for the purpose of the
measurement of atmospheric characteristics, of the validation of satellite device data, of the test of prototypes of future
satellite meters. Besides, the investigations of ozone, water vapor, and aerosol content were carried out in various geographical
zones (Hayes and Dickson islands, Salekhard, Yakutsk) using the small-volume balloons. The optical fluorescent hygrometer
of the Central Aerological Observatory (CAO) is considered as one of the best instruments to measure the atmospheric humidity.
Taking account of the reliability and accuracy of the measurements carried out, the values of the water vapor mixing ratio
in the winter polar cyclone obtained with this hygrometer can be considered as the reference data.
[Show abstract][Hide abstract] ABSTRACT: A multi-platform field measurement campaign involving aircraft and balloons took place over West Africa between 26 July and 25 August 2006, in the frame of the concomitant AMMA Special Observing Period and SCOUT-O3 African tropical activities.
Specifically aiming at sampling the upper troposphere and lower stratosphere, the high-altitude research aircraft M55 Geophysica was deployed in Ouagadougou (12.3° N, 1.7° W), Burkina Faso, in conjunction with the German D-20 Falcon, while a series of stratospheric balloon and sonde flights were conducted from Niamey (13.5° N, 2.0° E), Niger.
The stratospheric aircraft and balloon flights intended to gather experimental evidence for a better understanding of large scale transport, assessing the effect of lightning on NOx production, and studying the impact of intense mesoscale convective systems on water, aerosol, dust and chemical species in the upper troposphere and lower stratosphere. The M55 Geophysica carried out five local and four transfer flights between southern Europe and the Sahel and back, while eight stratospheric balloons and twenty-nine sondes were flown from Niamey.
These experiments allowed a characterization of the tropopause and lower stratosphere of the region. We provide here an overview of the campaign activities together with a description of the general meteorological situation during the flights and a summary of the observations accomplished.
[Show abstract][Hide abstract] ABSTRACT: Climate change manifests itself not only near the earth’s surface but also in a significant range of atmospheric heights.
A number of the most important climate change-related trends in Russian and foreign studies of dynamic and chemical processes
in the troposphere, stratosphere, and mesosphere are considered in this article.
Herald of the Russian Academy of Sciences 02/2010; 80(1):47-56. DOI:10.1134/S1019331610010065 · 0.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The results of measurements of water-vapor vertical profiles in the upper troposphere and stratosphere on board a meteorological
balloon with a FLASH-B optical fluorescent hygrometer (Russia) are presented. These data were obtained during two international
field campaigns in West Africa (August 2006) and Central America (August 2007). Eleven high-resolution water-vapor vertical
profiles measured in the course of these works make it possible to characterize the processes controlling humidity in the
tropical tropopause region. Layers with increased humidity are detected in the lower stratosphere over West Africa to the
level of the potential temperature 450 K. An analysis of satellite maps of the brightness temperature, balloon ozone measurements,
and aerosol scattering, as well as trajectory modeling, display the relation between the observed layers with increased humidity
and the phenomena of convective overshooting of the tropopause, as a result of which cold and ozone-depleted air penetrates
into the lower stratosphere together with ice particles, which, rapidly sublimating, locally increase the water-vapor concentration.
A comparison of the humidity data obtained in West Africa in 2006 and in Central America in 2007 reveals substantial distinctions
in values and vertical structures of water vapor, both in the tropopause region and in the middle stratosphere.
[Show abstract][Hide abstract] ABSTRACT: Airborne in-situ observations of ClO in the tropics
were made during the TROCCINOX (Aracatuba, Brazil,
February 2005) and SCOUT-O3 (Darwin, Australia, November/ December 2005) field campaigns. While during most flights significant amounts of ClO (10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed
in air masses of a more tropospheric character. Most
of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation
in the tropical upper troposphere lower stratosphere
(UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the
observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.
[Show abstract][Hide abstract] ABSTRACT: Processes of mass exchange through the tropopause at extratropical latitudes are studied. For this purpose, balloon data on
ozone and water vapor obtained during the LAUTLOS field campaign were analyzed and a trajectory model was used to analyze
the origin of air masses and to calculate fluxes through the tropopause. The results of observations and trajectory modeling
showed that tropospheric air masses penetrated into the stratosphere by no more than ∼2.5 km above the tropopause level during
the campaign. Both tropospheric and stratospheric particles are present in this mixing layer. Backward trajectories showed
that, at the anticyclone boundary, tropospheric air penetrates into the stratosphere in the form of fine fibrous structures
(filaments). The fluxes through the tropopause were also quantitatively estimated by the Wei method with the use of forward
and backward trajectories. The spatial structure of the fluxes through the tropopause coincides with the regions of the tropopause
inclination and its folds. The absolute values of the fluxes calculated with the use of the Wei method decrease, depending
on the length of trajectories at the expense of the filtering-out of a shallow reversible exchange. It is shown that the exchange
depth can be controlled by both vertical fluxes in the troposphere and changes in the level of the tropopause itself. The
use of isentropic and three-dimensional trajectories made it possible to estimate the contribution of nonadiabatic processes
to the stratosphere-troposphere exchange.
[Show abstract][Hide abstract] ABSTRACT: First, we present a detailed intercomparison of the ground based
microwave radiometers for middle atmospheric water vapor of the Network
for the Detection of Atmospheric Composition Change, NDACC. For this
purpose the retrievals of all microwave systems have been adapted as
much as possible using the temperatures measured by EOS MLS and using
the same set of spectroscopic parameters. The EOS MLS water vapor record
has then been used as reference and allowed to perform an
intercomparison of the ground based radiometers. The agreement between
the ground based systems is better than 5% in a pressure range between 1
and 0.03 hPa. Second, we focus on the water vapor time series at 10 hPa
as measured by the Middle Atmospheric WAter vapor RAdiometer, MIAWARA,
over Switzerland. A total of 6 coincident balloon soundings with a FLASH
hygrometer on board are evaluated revealing good consistency between the
in situ and the remote sensing measurements. We further analyze the
variability of the 10 hPa time series in the context of the polar vortex
and sudden stratospheric warmings that are accompanied by an increase of
water vapor at 10 hPa.
[Show abstract][Hide abstract] ABSTRACT: Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System (AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). In the stratosphere there is no clear indication of a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. The results of χ2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the χ2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.
[Show abstract][Hide abstract] ABSTRACT: The possible impact of deep convective overshooting over land has been explored by six simultaneous soundings of water vapour, particles and ozone in the lower stratosphere next to Mesoscale Convective Systems (MCSs) during the monsoon season over West Africa in Niamey, Niger in August 2006. The water vapour measurements were carried out using a fast response FLASH-B Lyman-alpha hygrometer. The high vertical resolution observations of the instrument show the presence of accumulation of enhanced water vapour layers between the tropopause at 370 K and the 420 K level. Most of these moist layers are shown connected with overshooting events occurring upwind as identified from satellite IR images over which the air mass probed by the sondes passed during the three previous days. In the case of a local overshoot identified by echo top turrets above the tropopause by the MIT C-band radar also in Niamey, tight coincidence was found between enhanced water vapour, ice crystal and ozone dip layers indicative of fast uplift of tropospheric air across the tropopause. The water vapour mixing ratio in the enriched layers exceeds frequently by 1–3 ppmv the average 6 ppmv saturation ratio at the tropopause and by up to 7 ppmv in the extreme case of local storm in coincidence with the presence of ice crystals. The presence of such layers strongly suggests hydration of the lower stratosphere by geyser-like injection of ice particles over overshooting turrets. The pile-like increase of water vapour up to 19 km seen by the high-resolution hygrometer during the season of maximum temperature of the tropopause, suggests that the above hydration mechanism may contribute to the summer maximum moisture in the lower stratosphere. If this interpretation is correct, hydration by ice geysers across the tropopause might be an important contributor to the stratospheric water vapour budget.