E. Kyrölä | Finnish Meteorological Institute (original) (raw)

Papers by E. Kyrölä

Atmospheric Chemistry and Physics Discussions, 2013

Stratospheric ozone profile measurements from the Stratospheric Aerosol and Gas Experiment (SAGE)... more Stratospheric ozone profile measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II satellite instrument are combined with those from the Optical Spectrograph and InfraRed Imager System (OSIRIS) instrument on the Odin satellite (2001-Present) to quantify interannual variability and decadal trends in 5 stratospheric ozone between 60 • S and 60 • N. These data are merged into a multiinstrument, long-term stratospheric ozone record (1984-present) by analyzing the measurements during the overlap period of 2002-2005 when both satellite instruments were operational. The variability in the deseasonalized time series is fit using multiple linear regression with predictor basis functions including the quasi-biennial oscillation, 10 El Niño-Southern Oscillation index, solar activity proxy, and the pressure at the tropical tropopause, in addition to two linear trends (one before and one after 1997), from which the decadal trends in ozone are derived. From 1984-1997, there are statistically significant negative trends of 5-10 % per decade throughout the stratosphere between approximately 30-50 km. From 1997-present, a statistically significant recovery of 3-15 8 % per decade has taken place throughout most of the stratosphere with the notable exception between 40 • S-40 • N below approximately 22 km where the negative trend continues. The recovery is not significant between 25-35 km altitude when accounting for a conservative estimate of instrument drift. by 2050 at the earliest (WMO, 2011). Several recent studies have highlighted the need 7114

Atmospheric Chemistry and Physics Discussions, 2010

The GOMOS ozone profiles derived have been analyzed to evaluate the GOMOS ability to capture the ... more The GOMOS ozone profiles derived have been analyzed to evaluate the GOMOS ability to capture the long-term ozone evolution during its expected recovery phase. Version 5 of the GOMOS data has been compared with two of the longest ground-based instruments based on different techniques and already involved with many other previ-5 20 column is well adapted to monitor the potential increase of the solar UV irradiance, the distribution of the modifications as a function of altitude is crucial to better understand the processes involved and the climate impact of the ozone changes (WMO, 2007). The two longest records of ozone profiles from space are available from two different types of instrument: the Solar Backscatter Ultraviolet (SBUV(/2)) satellite instruments 25 and the Stratospheric Aerosol and Gas Experiment (SAGE I+II).

The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation t... more The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation technique for monitoring ozone and other trace gases in the stratosphere and mesosphere. The self-calibrating measurement principle of GOMOS together with a relatively simple data retrieval where only minimal use of a priori data is required, 5 provides excellent possibilities for long term monitoring of atmospheric composition.

Earth System Science Data, 2013

In this paper, we present a HARMonized dataset of OZone profiles (HARMOZ) based on limb and occul... more In this paper, we present a HARMonized dataset of OZone profiles (HARMOZ) based on limb and occultation measurements from Envisat (GOMOS, MIPAS and SCIAMACHY), Odin (OSIRIS, SMR) and SCISAT (ACE-FTS) satellite instruments. These measurements provide high-vertical-resolution ozone profiles covering the altitude range from the upper troposphere up to the mesosphere in years 2001-2012. HARMOZ has been created in the framework of the European Space Agency Climate Change Initiative project.

Journal of Geophysical Research, 1998

Geophysical Research Letters, 2004

Geophysical Research Letters, 2006

1] Using measurements from the MLS/Aura and GOMOS/Envisat instruments together with a 1-D ion and... more 1] Using measurements from the MLS/Aura and GOMOS/Envisat instruments together with a 1-D ion and neutral chemistry model we study the changes in odd hydrogen and ozone in the mesosphere during the January 2005 solar proton event. The unique observational data allow us for the first time to directly test the HO x production theory which involves complex ion chemistry. MLS measurements from the northern polar region show increases of OH concentrations by over 100% around the stratopause, and by up to one order of magnitude in the middle mesosphere after the onset of the SPE. GOMOS measurements indicate decreases in O 3 concentration throughout the lower and middle mesosphere, by up to 90%. The model predictions are in reasonable agreement with the observations. We point out that models using the so-called P HOx /Q parameterization to include the effects of ion chemistry could underestimate the HO x production and the resulting ozone depletion. Citation: Verronen, P. T.,

Atmospheric Chemistry and Physics, 2010

This paper presents a climatology of the mesospheric sodium layer built from the processing of 7 ... more This paper presents a climatology of the mesospheric sodium layer built from the processing of 7 years of GOMOS data. With respect to preliminary results already published for the year 2003, a more careful analysis was applied to the averaging of occultations inside the climatological bins (10 • in latitude-1 month). Also, the slant path absorption lines of the Na doublet around 589 nm shows evidence of partial saturation that was responsible for an underestimation of the Na concentration in our previous results. The sodium climatology has been validated with respect to the Fort Collins lidar measurements and, to a lesser extent, to the OSIRIS 2003-2004 data. Despite the important natural sodium variability, we have shown that the Na vertical column has a marked semi-annual oscillation at low latitudes that merges into an annual oscillation in the polar regions,a spatial distribution pattern that was unreported so far. The sodium layer seems to be clearly influenced by the mesospheric global circulation and the altitude of the layer shows clear signs of subsidence during polar winter. The climatology has been parameterized by time-latitude robust fits to al-Correspondence to: D. Fussen (didier.fussen@oma.be) low for easy use. Taking into account the non-linearity of the transmittance due to partial saturation, an experimental approach is proposed to derive mesospheric temperatures from limb remote sounding measurements.

Annales Geophysicae, 2004

In this work we discuss inclusion of a priori information about the smoothness of atmospheric pro... more In this work we discuss inclusion of a priori information about the smoothness of atmospheric profiles in inversion algorithms. The smoothness requirement can be formulated in the form of Tikhonov-type regularization, where the smoothness of atmospheric profiles is considered as a constraint or in the form of Bayesian optimal estimation (maximum a posteriori method, MAP), where the smoothness of profiles can be included as a priori information. We develop further two recently proposed retrieval methods. One of them -Tikhonov-type regularization according to the target resolution -develops the classical Tikhonov regularization. The second method -maximum a posteriori method with smoothness a priori -effectively combines the ideas of the classical MAP method and Tikhonov-type regularization. We discuss a grid-independent formulation for the proposed inversion methods, thus isolating the choice of calculation grid from the question of how strong the smoothing should be.

Advances in Space Research, 2004

GOMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O 3 , NO 2 , NO... more GOMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O 3 , NO 2 , NO 3 , neutral density, aerosols, H 2 O, and O 2 , in the stratosphere and mesosphere by detecting absorption of starlight in ultraviolet, visible and nearinfrared wavelengths. During bright limb conditions GOMOS will also observe scattered solar radiation. GOMOS will deliver ozone concentration profiles at altitudes 15-100 km with a vertical sampling better than 1.7 km and with a global coverage. As a selfcalibrating method stellar occultation measurements provide a basis for a long-term global monitoring of ozone profiles. We will present here the status of the GOMOS instrument and show samples of first results obtained in 2002.

Journal of Geophysical Research: Atmospheres, 2013

1] The link between stratospheric ozone decline and ultraviolet (UV) radiation increase at the Ea... more 1] The link between stratospheric ozone decline and ultraviolet (UV) radiation increase at the Earth's surface is well established. In the Northern Hemisphere extratropics, stratospheric ozone is accumulated from autumn to spring as a result of transport from its source region in the tropics. The amount of accumulated ozone varies from year to year due to natural dynamical variability and chemical destruction by natural and anthropogenic substances. Observational and modeling studies show that these total ozone anomalies persist in the extratropics from spring to summer. Here we analyze time series of ground-based UV measurements and satellite retrievals of total ozone and UV radiation and demonstrate that there is a strong link between springtime total ozone and summer UV anomalies in the Northern Hemisphere extratropics. In some regions, the interannual variability in springtime ozone abundance explains 20-40% of the summer UV variability, and this relation can be used for improving seasonal UV forecasts. Using chemistry transport models, we estimate the influence of polar chemical ozone loss on the summer UV north of 35°N. We estimate that the massive Arctic ozone depletion 2011 increased the March-August cumulative erythemal clear-sky UV dose in the Northern Hemisphere extratropics by 3-4% compared to the climatology, with about 75% of the increase accumulated after the breakup of the polar vortex. This result strongly suggests that the effect of seasonal ozone anomaly persistence should be included in the assessment of the impacts of polar ozone losses.