The Earth Observing System Microwave Limb Sounder measures several atmospheric chemical species (OH, HO/sub 2/, H/sub 2/O, O/sub 3/, HCl, ClO, HOCl, BrO, HNO/sub 3/, N/sub 2/O, CO, HCN, CH/sub 3/CN, volcanic SO/sub 2/), cloud ice, temperature, and geopotential height to improve our understanding of stratospheric ozone chemistry, the interaction of composition and climate, and pollution in the upper troposphere. All measurements are made simultaneously and continuously, during both day and night. The instrument uses heterodyne radiometers that observe thermal emission from the atmospheric limb in broad spectral regions centered near 118, 190, 240, and 640 GHz, and 2.5 THz. It was launched July 15, 2004 on the National Aeronautics and Space Administration's Aura satellite and started full-up science operations on August 13, 2004. An atmospheric limb scan and radiometric calibration for all bands are performed routinely every 25 s. Vertical profiles are retrieved every 165 km along the suborbital track, covering 82/spl deg/S to 82/spl deg/N latitudes on each orbit. Instrument performance to date has been excellent; data have been made publicly available; and initial science results have been obtained.

https://aura.gsfc.nasa.gov/science/publications/Waters_Froidevaux_Harwood_IEEE2006.pdf

The Earth observing system microwave limb sounder (EOS MLS) on the aura Satellite

TROPOMI on the ESA Sentinel-5 Precursor: A GMES mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications

Solitary electrostatic structures involving density depletions have been observed in the upper ionosphere by the Freja satellite [Dovner et al., 1994]. If these are interpreted as ion sound solitons, the difficulty arises that the standard Korteweg-de Vries description predicts structures with enhanced rather than depleted density. Here we show that the presence of non-thermal electrons may change the nature of ion sound solitary structures and allow the existence of structures very like those observed.

Electrostatic solitary structures in non‐thermal plasmas

We present an overview of the theoretical and algorithmic aspects of the Ozone Monitoring Instrument (OMI) aerosol and surface UV algorithms. Aerosol properties are derived from two independent algorithms. The nearUV algorithm makes use of OMI observations in the 350-390 nm spectral region to retrieve information on the absorption capacity of tropospheric aerosols. OMI-derived information on aerosol absorption includes the UV Aerosol Index and absorption optical depth at 388 nm. The other algorithm makes use of the full UV-to-visible OMI spectral coverage to derive spectral aerosol extinction optical depth. OMI surface UV products include erythemally weighted daily dose as well as erythemal dose rate and spectral UV irradiances calculated for local solar noon conditions. The advantages and limitations of the current algorithms are discussed, and a brief summary of several validation and evaluation analysis carried out to assess the current level of uncertainty of these products is presented. Copyright 2007 by the American Geophysical Union. U7 - Export Date: 2 August 2010 U7 - Source: Scopus U7 - Art. No.: D24S47

https://aura.gsfc.nasa.gov/science/publications/Torres_Tanskanen_Veihelmann_JGR2007.pdf

Aerosols and surface UV products from Ozone Monitoring Instrument observations: An overview

Chemical ozone destruction occurs over both polar regions in local winter–spring. In the Antarctic, essentially complete removal of lower-stratospheric ozone currently results in an ozone hole every year, whereas in the Arctic, ozone loss is highly variable and has until now been much more limited. Here we demonstrate that chemical ozone destruction over the Arctic in early 2011 was—for the first time in the observational record—comparable to that in the Antarctic ozone hole. Unusually long-lasting cold conditions in the Arctic lower stratosphere led to persistent enhancement in ozone-destroying forms of chlorine and to unprecedented ozone loss, which exceeded 80 per cent over 18–20 kilometres altitude. Our results show that Arctic ozone holes are possible even with temperatures much milder than those in the Antarctic. We cannot at present predict when such severe Arctic ozone depletion may be matched or exceeded. Since its emergence in the 1980s, the Antarctic ozone hole, the near-complete loss of lower-stratospheric ozone, has occurred every year. The possibility that a similar effect might occur in the Northern Hemisphere has been debated, but despite considerable variation in ozone levels in the Arctic, they had not reached the extremes seen in the south. Until this year. Observations made in the late winter and early spring of 2011 reveal ozone loss far outside the range previously observed over the Northern Hemisphere, comparable to some Antarctic ozone holes. The formation of the hole was driven by an unusually long cold snap and a high level of ozone-destroying chlorine. Although this effect is dramatic, it is difficult to predict whether similar Arctic ozone holes will develop in future.

Unprecedented Arctic ozone loss in 2011

We have used data from the Freja satellite, with an apogee of 1700 km over the auroral oval, to make a statistical analysis of mesoscale auroral plasma density cavities. Such cavities are defined to be regions in the auroral zone with size scales between discrete arcs and inverted-V events in which the plasma density abruptly drops to less than 50% of the ambient plasma density. We present occurrence distributions by magnetic activity, local time, and magnetic latitude. It is found that cavity occurrence does not depend on magnetic activity. In contrast to earlier studies, we find cavities at all local times; however, a dawn-dusk asymmetry is found in the distribution. There is likewise a weak dawn-dusk asymmetry in the latitudinal distribution. Since our data cover a full year, seasonal dependence of cavity occurrence can also be investigated. We find a small seasonal trend, with cavities found more commonly during the dark season, but the trend is not quite statistically significant. We also study several plasma depletion processes that could be responsible for cavities at this altitude. The results suggest that more than one process is compatible with the distributions we find.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JA00212

Observations of mesoscale auroral plasma cavity crossings with the Freja satellite

Solitary electrostatic waves (SWs) were frequently observed by the Viking satellite in the auroral plasma. Previously, Malkki et al. [1993] reported occurrence statistics and voltage data for these structures. In this paper, we make a detailed study of the measurement process in order to establish what further knowledge can be extracted from the data. The possibilities that SWs are spacecraft-generated pulses or signatures of rectification of hypothetical wave packets are investigated and rejected. We analyze Langmuir probe data from several SW events and show that densities are at least as low as previously reported (a few cm−3). In order to assess the quality of the SW observations in this very tenuous plasma, we use a semiempirical model of the complete probe-spacecraft-plasma system, including nonlinearities in the probe sheaths. The usefulness of the model is shown by its ability to model details in the measured fluctuations. It is found that the errors in the voltage (electric field) measurements of solitary waves are very small, while the density fluctuation estimates may be severely affected by spurious signals. Therefore details in the shape of the observed probe current signature cannot be used to study the detailed shape of the density depletion. This limits the possibility of identifying weak double layer (WDL) characteristics in SWs, as effects of time evolution result in signatures similar to those of net potential drops.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96JA02728

A statistical survey of auroral solitary waves and weak double layers: 2. Measurement accuracy and ambient plasma density

[1] The Dutch-Finnish Ozone Monitoring Instrument (OMI) is on board the NASA's Earth Observing System (EOS) Aura satellite. The Aura satellite has a so-called direct broadcast (DB) capability to broadcast the measurements to ground stations at the same time as the measurements are being stored in the spacecraft's memory for later transmission to Earth. The Finnish Meteorological Institute's very fast delivery (VFD) processing system utilizes this direct broadcast to produces maps of total ozone and ultraviolet radiation over Europe within 15 min after the satellite overpass Sodankyla ground station in northern Finland. The VFD products include maps of total ozone, ultraviolet index, and ultraviolet daily dose. The aim of this service is to provide up-to-date information on the ozone and ultraviolet situation for the general public and snapshots of the current situation for scientists. The accuracy of the VFD products compares well with standard off-line OMI ozone products as well as ground-based Brewer measurements. After the VFD update in May 2006, the differences with Brewer measurements are −1.0 ± 7.2 DU for Sodankyla and −0.6 ± 8.0 DU for Jokioinen. Differences to OMDOAO3 and OMTO3 products are 2.1 ± 3.3 DU and 1.6 ± 6.6 DU for Sodankyla and 1.7 ± 2.0 DU and 0.0 ± 6.1 DU for Jokioinen, respectively. Between the VFD and Brewer measured UV daily dose products the relative error is generally less than 30%, which compares well to the global off-line OMUVB product.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2007JD008784

Description and validation of the OMI very fast delivery products

Auroral Weak Double Layers: a Critical Assessment

The Ozone Monitoring Instrument (OMI) operates onboard the National Aeronautics and Space Administration's Earth Observing System Aura satellite, which was launched in July 2004. Like its sister spacecraft Terra and Aqua, Aura's capabilities include direct broadcast (DB), i.e., the ability to broadcast data at the same time as they are being measured and stored in the spacecraft's memory for later transmission to Earth. The Finnish Meteorological Institute's Satellite Data Centre at Sodankyla/spl uml/ in Finnish Lapland is exploiting this capability to receive OMI data while Aura is in sight of the receiver, which enables nearly immediate production of OMI data products for a region that includes a large part of Europe, stretching from the North Pole to the Italian Alps. The current OMI Very Fast Delivery (VFD) products include maps of surface UV-B, ozone columns, and cloud coverage.

https://aura.gsfc.nasa.gov/science/publications/Leppelmeier_Aulamo_Hassinen_IEEE2006.pdf

A. Malkki

Papers

Observations of mesoscale auroral plasma cavity crossings with the Freja satellite

A statistical survey of auroral solitary waves and weak double layers: 2. Measurement accuracy and ambient plasma density

Description and validation of the OMI very fast delivery products

Auroral Weak Double Layers: a Critical Assessment

OMI very fast delivery and the Sodankyla/spl uml/ Satellite Data Centre