Ozonvertikalverteilungen aus UV/Vis-Nadirspektren des Satelliteninstrumentes GOME:Optimierung und Sensitivitätsstudien zur Nutzung der achtjährigen Messreihen

The stratospheric ozone layer protects the biosphere from the effects of harmful ultraviolet radiation and is responsible for the temperature structure of the stratosphere. The severe changes of the ozone layer during the last decades clarified the need to monitor the variation of ozone concentrations.The Global Ozone Monitoring Experiment (GOME) which was launched in April 1995 onboard ESA´s second European Remote Sensing Satellite (ERS-2) enables us to investigate height resolved ozone distributions. The grating spectrometer measures direct and backscattered radiances in the ultraviolet and visible spectral range. The inversion algorithm FURM (FUll Retrieval Method) was developed to retrieve ozone vertical distributions from these spectral data using an Advanced Optimal Estimation approach.Internal broadband calibration corrections in the former standard versions of the FURM algorithm were forced by the increasing degradation of the optical components of GOME. Additional observed high frequency structures that inhibited the use of wavelengths below 290 nm resulted in a very weak stratospheric sensitivity above 35 km. Especially the profile retrieval in the low latitude range was affected by these deficiencies and motivated the development of a new calibration correction. The promising results encouraged further investigations of the higher latitude range. Here an additional modification of the broadband calibration correction is required to account for the low differential structure of ozone. Therefore a second approach is developed which leads in combination with the low latitude method to a significantly improved stratospheric ozone profile retrieval. These results make it now possible to investigate tropospheric ozone absorption structures which are otherwise dominated by any remaining stratospheric ozone feature. For the first time this new retrieval algorithm can now be used to retrieve longterm trends of ozone profiles on a global scale

Venus Atmospheric Thermal Structure and Radiative Balance

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Validation of the IPSL Venus GCM Thermal Structure with Venus Express Data

General circulation models (GCMs) are valuable instruments to understand the most peculiar features in the atmospheres of planets and the mechanisms behind their dynamics. Venus makes no exception and it has been extensively studied thanks to GCMs. Here we validate the current version of the Institut Pierre Simon Laplace (IPSL) Venus GCM, by means of a comparison between the modelled temperature field and that obtained from data by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) and the Venus Express Radio Science Experiment (VeRa) onboard Venus Express. The modelled thermal structure displays an overall good agreement with data, and the cold collar is successfully reproduced at latitudes higher than +/−55°, with an extent and a behavior close to the observed ones. Thermal tides developing in the model appear to be consistent in phase and amplitude with data: diurnal tide dominates at altitudes above 102 Pa pressure level and at high-latitudes, while semidiurnal tide dominates between 102 and 104 Pa, from low to mid-latitudes. The main difference revealed by our analysis is located poleward of 50°, where the model is affected by a second temperature inversion arising at 103 Pa. This second inversion, possibly related to the adopted aerosols distribution, is not observed in data

Mosaic: A Satellite Constellation to Enable Groundbreaking Mars Climate System Science and Prepare for Human Exploration

The Martian climate system has been revealed to rival the complexity of Earth\u27s. Over the last 20 yr, a fragmented and incomplete picture has emerged of its structure and variability; we remain largely ignorant of many of the physical processes driving matter and energy flow between and within Mars\u27 diverse climate domains. Mars Orbiters for Surface, Atmosphere, and Ionosphere Connections (MOSAIC) is a constellation of ten platforms focused on understanding these climate connections, with orbits and instruments tailored to observe the Martian climate system from three complementary perspectives. First, low-circular near-polar Sun-synchronous orbits (a large mothership and three smallsats spaced in local time) enable vertical profiling of wind, aerosols, water, and temperature, as well as mapping of surface and subsurface ice. Second, elliptical orbits sampling all of Mars\u27 plasma regions enable multipoint measurements necessary to understand mass/energy transport and ion-driven escape, also enabling, with the polar orbiters, dense radio occultation coverage. Last, longitudinally spaced areostationary orbits enable synoptic views of the lower atmosphere necessary to understand global and mesoscale dynamics, global views of the hydrogen and oxygen exospheres, and upstream measurements of space weather conditions. MOSAIC will characterize climate system variability diurnally and seasonally, on meso-, regional, and global scales, targeting the shallow subsurface all the way out to the solar wind, making many first-of-their-kind measurements. Importantly, these measurements will also prepare for human exploration and habitation of Mars by providing water resource prospecting, operational forecasting of dust and radiation hazards, and ionospheric communication/positioning disruptions

Ozone Vertical Distributions from UV/Vis-Nadirspectra: Optimisation and Sensitivity Studies for the Use of the Long-Term Series of GOME-Measurements

The stratospheric ozone layer protects the biosphere from the effects of harmful ultraviolet radiation and is responsible for the temperature structure of the stratosphere. The severe changes of the ozone layer during the last decades clarified the need to monitor the variation of ozone concentrations.The Global Ozone Monitoring Experiment (GOME) which was launched in April 1995 onboard ESA´s second European Remote Sensing Satellite (ERS-2) enables us to investigate height resolved ozone distributions. The grating spectrometer measures direct and backscattered radiances in the ultraviolet and visible spectral range. The inversion algorithm FURM (FUll Retrieval Method) was developed to retrieve ozone vertical distributions from these spectral data using an Advanced Optimal Estimation approach.Internal broadband calibration corrections in the former standard versions of the FURM algorithm were forced by the increasing degradation of the optical components of GOME. Additional observed high frequency structures that inhibited the use of wavelengths below 290 nm resulted in a very weak stratospheric sensitivity above 35 km. Especially the profile retrieval in the low latitude range was affected by these deficiencies and motivated the development of a new calibration correction. The promising results encouraged further investigations of the higher latitude range. Here an additional modification of the broadband calibration correction is required to account for the low differential structure of ozone. Therefore a second approach is developed which leads in combination with the low latitude method to a significantly improved stratospheric ozone profile retrieval. These results make it now possible to investigate tropospheric ozone absorption structures which are otherwise dominated by any remaining stratospheric ozone feature. For the first time this new retrieval algorithm can now be used to retrieve longterm trends of ozone profiles on a global scale

Atmospheric structure and diurnal variations at low altitudes in the Martian Tropics

We are using radio occultation measurements from Mars Express, Mars Reconnaissance Orbiter, and Mars Global Surveyor to characterize the diurnal cycle in the lowest scale height above the surface. We focus on northern spring and summer, using observations from 4 Martian years at local times of 4-5 and 15-17 h. We supplement the observations with results obtained from large-eddy simulations and through data assimilation by the UK spectral version of the LMD Mars Global Circulation Model. We previously investigated the depth of the daytime convective boundary layer (CBL) and its variations with surface elevation and surface properties. We are now examining unusual aspects of the temperature structure observed at night. Most important, predawn profiles in the Tharsis region contain an unexpected layer of neutral static stability at pressures of 200-300 Pa with a depth of 4-5 km. The mixed layer is bounded above by a midlevel temperature inversion and below by another strong inversion adjacent to the surface. The narrow temperature minimum at the base of the midlevel inversion suggests the presence of a water ice cloud layer, with the further implication that radiative cooling at cloud level can induce convective activity at lower altitudes. Conversely, nighttime profiles in Amazonis show no sign of a midlevel inversion or a detached mixed layer. These regional variations in the nighttime temperature structure appear to arise in part from large-scale variations in topography, which have several notable effects. First, the CBL is much deeper in the Tharsis region than in Amazonis, owing to a roughly 6-km difference in surface elevation. Second, large-eddy simulations show that daytime convection is not only deeper above Tharsis but also considerably more intense than it is in Amazonis. Finally, the daytime surface temperatures are comparable in the two regions, so that Tharsis acts as an elevated heat source throughout the CBL. These topographic effects are expected to enhance the vertical mixing of water vapor above elevated terrain, which might lead to the formation and regional confinement of nighttime clouds

Sulfuric acid vapor and sulfur dioxide in the atmosphere of Venus as observed by VeRa

&amp;lt;p&amp;gt;The main Venus clouds, covering the entire planet between approx. 50 and 70 km altitude, are believed to consist mostly of liquid sulfuric acid. Below the clouds, the temperature is high enough to evaporate those droplets into gaseous sulfuric acid forming a haze layer which extends to altitudes as deep as 35 km. H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) is the main absorber of radio waves as was observed in Mariner, Pioneer Venus, Magellan and Venera radio occultation measurements. Radio wave absorption measurements can be used to derive the amount of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; as well as to estimate upper limits of SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in Venus&amp;amp;#8217; atmosphere. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2014 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. Thanks to the orbit of VEX, a wide range of latitudes and local times was covered so that a global picture of the H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) ditribution was obtained. We present H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) profiles as well as upper limits of sulfur dioxide near the cloud base derived from the X-band radio signal from the entire Venus Express mission. More than 600 H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) profiles show the global sulfuric acid vapor distribution covering the northern and southern hemisphere on the day- and night side of the planet. A distinct latitudinal&amp;amp;#160;H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) and SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; variation and a southern northern symmetry are clearly visible. Observations over 8 years allow to study also long-term variations. Indications for temporal H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) and SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; variations are found, at least at northern polar latitudes. The results shall be compared with observations retrieved by other experiments onboard Venus Express. Additionally, the observed H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;(g) distribution will be compared with results obtained from a mass transport model.&amp;lt;/p&amp;gt;</jats:p

Sulfuric acid vapor and sulfur dioxide in the atmosphere of Venus as observed by the Venus Express Radio Science Experiment VeRa

&amp;lt;p&amp;gt;The main cloud deck within Venus' atmosphere, which covers the entire planet between approx. 50 and 70 km altitude, is believed to consist mostly of liquid sulfuric acid. The temperature below the main clouds is high enough to evaporate the H2SO4 droplets into gaseous sulfuric acid forming a haze layer which extends to altitudes as deep as 35 km. Gaseous sulfuric acid in Venus&amp;amp;#8217; lower atmosphere is responsible for a strong absorption of radio waves as seen in Mariner, Pioneer Venus, Magellan and Venera radio science observations. Radio wave absorption measurements can be used to derive the amount of H2SO4 in Venus&amp;amp;#8217; atmosphere. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2014 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. The orbit of the Venus Express spacecraft allowed to sound the atmosphere over a wide range of latitudes and local times providing a global picture of the sulfuric acid vapor distribution. We present the global H2SO4(g) distribution derived from the X-band radio signal attenuation for the time of the entire Venus Express mission. The observation is compared with results obtained from a 2-D transport model. The VeRa observations were additionally used to estimate the abundance of SO2 near the cloud bottom. The global distribution of SO2 at these altitudes is presented and compared with results obtained from other experiments. Eight years of VEX observation allow to study the long-term evolution of H2SO4 and SO2. The latter is presented for the northern polar region.&amp;lt;/p&amp;gt;</jats:p

Vertical Wavenumber Spectra of Gravity Waves in the Venus Atmosphere Obtained from Venus Express Radio Occultation Data: Evidence for Saturation

Abstract By using the vertical temperature profiles obtained by the radio occultation measurements on the European Space Agency (ESA)’s Venus Express, the vertical wavenumber spectra of small-scale temperature fluctuations that are thought to be manifestations of gravity waves are studied. Wavenumber spectra covering wavelengths of 1.4–7.5 km were obtained for two altitude regions (65–80 and 75–90 km) and seven latitude bands. The spectra show a power-law dependence on the high-wavenumber side with the logarithmic spectral slope ranging from −3 to −4, which is similar to the features seen in Earth’s and Martian atmospheres. The power-law portion of the spectrum tends to follow the semiempirical spectrum of saturated gravity waves, suggesting that the gravity waves are dissipated by saturation as well as radiative damping. The spectral power is larger at 75–90 km than at 65–80 km at low wavenumbers, suggesting amplitude growth with height of unsaturated waves. It was also found that the wave amplitude is larger at higher latitudes and that the amplitude is maximized in the northern high latitudes. On the assumption that gravity waves are saturated in the Venusian atmosphere, the turbulent diffusion coefficient was estimated. The diffusion coefficient in the Venusian atmosphere is larger than those in Earth’s atmosphere because of the longer characteristic vertical wavelength of the saturated waves.</jats:p