We describe a huge planetary‐scale disturbance in the highest‐speed Jovian jet at latitude 23.5°N that was first observed in October 2016 during the Juno perijove‐2 approach. An extraordinary ...outburst of four plumes was involved in the disturbance development. They were located in the range of planetographic latitudes from 22.2° to 23.0°N and moved faster than the jet peak with eastward velocities in the range 155 to 175 m s−1. In the wake of the plumes, a turbulent pattern of bright and dark spots (wave number 20–25) formed and progressed during October and November on both sides of the jet, moving with speeds in the range 100–125 m s−1 and leading to a new reddish and homogeneous belt when activity ceased in late November. Nonlinear numerical models reproduce the disturbance cloud patterns as a result of the interaction between local sources (the plumes) and the zonal eastward jet.
Key Points
A planetary‐scale disturbance developed in the highest‐speed Jupiter jet at 23.5°N latitude during October and November 2016
Four “plumes” were involved in the outbreak moving with speeds between 155 and 175 m s−1, the fastest features at cloud level
Nonlinear numerical models reproduce the disturbance from the interaction between local sources (the plumes) and the zonal eastward jet
Aims. We provide measurements of the absolute reflectivity of Jupiter and Saturn along their central meridians in filters covering a wide range of visible and near-infrared wavelengths (from 0.38 to ...1.7 μm) that are not often presented in the literature. We also give measurements of the geometric albedo of both planets and discuss the limb-darkening behavior and temporal variability of their reflectivity values for a period of four years (2012–2016). Methods. This work is based on observations with the PlanetCam-UPV/EHU instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory (Spain). The instrument simultaneously observes in two channels: visible (VIS; 0.38–1.0 μm) and short-wave infrared (SWIR; 1.0–1.7 μm). We obtained high-resolution observations via the lucky-imaging method. Results. We show that our calibration is consistent with previous independent determinations of reflectivity values of these planets and, for future reference, provide new data extended in the wavelength range and in the time. Our results have an uncertainty in absolute calibration of 10–20%. We show that under the hypothesis of constant geometric albedo, we are able to detect absolute reflectivity changes related to planetary temporal evolution of about 5–10%.
We present zonal and meridional wind measurements at three altitude levels within the cloud layers of Venus from cloud tracking using images taken with the VIRTIS instrument on board Venus Express. ...At low latitudes, zonal winds in the Southern hemisphere are nearly constant with latitude with westward velocities of 105 ms−1 at cloud‐tops (altitude ∼ 66 km) and 60–70 ms−1 at the cloud‐base (altitude ∼ 47 km). At high latitudes, zonal wind speeds decrease linearly with latitude with no detectable vertical wind shear (values lower than 15 ms−1), indicating the possibility of a vertically coherent vortex structure. Meridional winds at the cloud‐tops are poleward with peak speed of 10 ms−1 at 55° S but below the cloud tops and averaged over the South hemisphere are found to be smaller than 5 ms−1. We also report the detection at subpolar latitudes of wind variability due to the solar tide.
•VMC on Mars Express has been successfully used to study aerosols at limb.•We report on 18 limb detections of layers of dust and clouds between 2007 and 2016.•We have measured the altitude, ...horizontal extent, location, Martian local time occurrence and seasonal epoch.•We analyze their nature from simultaneous MARCI Mars Reconnaissance Orbiter images and Mars Climate Database – LMD modeling.
The Visual Monitoring Camera (VMC) onboard the Mars Express (MEx) spacecraft is a simple camera aimed to monitor the release of the Beagle-2 lander on Mars Express and later used for public outreach. Here, we employ VMC as a scientific instrument to study and characterize high altitude aerosols events (dust and condensates) observed at the Martian limb. More than 21,000 images taken between 2007 and 2016 have been examined to detect and characterize elevated layers of dust in the limb, dust storms and clouds. We report a total of 18 events for which we give their main properties (areographic location, maximum altitude, limb projected size, Martian solar longitude and local time of occurrence). The top altitudes of these phenomena ranged from 40 to 85 km and their horizontal extent at the limb ranged from 120 to 2000 km. They mostly occurred at Equatorial and Tropical latitudes (between ∼30°N and 30°S) at morning and afternoon local times in the southern fall and northern winter seasons. None of them are related to the orographic clouds that typically form around volcanoes. Three of these events have been studied in detail using simultaneous images taken by the MARCI instrument onboard Mars Reconnaissance Orbiter (MRO) and studying the properties of the atmosphere using the predictions from the Mars Climate Database (MCD) General Circulation Model. This has allowed us to determine the three-dimensional structure and nature of these events, with one of them being a regional dust storm and the two others water ice clouds. Analyses based on MCD and/or MARCI images for the other cases studied indicate that the rest of the events correspond most probably to water ice clouds.
We study the 2018 Martian global dust storm (GDS 2018) over the Southern Polar Region using images obtained by the Visual Monitoring Camera (VMC) on board Mars Express (MEx) during June and July ...2018. Dust penetrated into the polar cap region but never covered the cap completely, and its spatial distribution was nonhomogeneous and rapidly changing. However, we detected long but narrow aerosol curved arcs with a length of ~2,000–3,000 km traversing part of the cap and crossing the terminator into the nightside. Tracking discrete dust clouds allowed measurements of their motions that were toward the terminator with velocities up to 100 m/s. The images of the dust projected into the Martian limb show maximum altitudes of ~70 km but with large spatial and temporal variations. We discuss these results in the context of the predictions of a numerical model for dust storm scenario.
Plain Language Summary
Dust storms of different scales (local, regional, etc.) are common on Mars. Some Martian years a regional storm activates secondary storms and dust encircles the planet, in a dust event usually called a global dust storm. The last global dust storm took place in 2018, and we are not currently able to predict when a new one will occur. Global dust storms affect the global dynamics of the Martian atmosphere, and the dynamics of the polar regions is a good proxy to the global situation. In this paper, we take advantage of the polar orbit of Mars Express to study the Southern Polar Region during 2018 global dust storm using the Visual Monitoring Camera onboard the spacecraft. We show how the dust penetrated into the polar cap, the apparition of aerosol arcs curved around the pole, and the presence of winds blowing up to 100 m/s, not following the usual patterns expected with no global dust storm.
Key Points
The 2018 global dust storm propagated unevenly over the South Polar Region, not covering it fully, and forming elongated narrow dust arcs
Overall, dust moved toward the terminator, reaching velocities up to 100 m/s in the morningside
During June–July 2018, the top altitude of dust showed both spatial and temporal variability, ranging from 10–70 km
The presence of dry fluvial river channels and the intense cloud activity in the south pole of Titan over the past few years suggest the presence of methane rain. The nitrogen atmosphere of Titan ...therefore appears to support a methane meteorological cycle that sculptures the surface and controls its properties. Titan and Earth are the only worlds in the Solar System where rain reaches the surface, although the atmospheric cycles of water and methane are expected to be very different. Here we report three-dimensional dynamical calculations showing that severe methane convective storms accompanied by intense precipitation may occur in Titan under the right environmental conditions. The strongest storms grow when the methane relative humidity in the middle troposphere is above 80 per cent, producing updrafts with maximum velocities of 20 m s-1, able to reach altitudes of 30 km before dissipating in 5–8 h. Raindrops of 1–5 mm in radius produce precipitation rainfalls on the surface as high as 110 kg m-2 and are comparable to flash flood events on Earth.
•Venus polar atmospheric temperature maps at cloud top resemble ∼5μm radiance images.•The vortex is squeezed by the cold collar between 55 and 67km but spreads out above ∼74km.•The South Polar ...Vortex’s thermal top limit is at ∼80km altitude on the night-side.•The cold collar is the most statically stable structure at nighttime polar latitudes.•Hot filaments within the vortex show lower stability values than their surroundings.
The Venus thermal radiation spectrum exhibits the signature of CO2 absorption bands. By means of inversion techniques, those bands enable the retrieval of atmospheric temperature profiles. We have analyzed VIRTIS-M-IR night-side data obtaining high-resolution thermal maps of the Venus south polar region between 55 and 85km altitudes. This analysis is specific to three Venus Express orbits where the vortex presents different dynamical configurations. The cold collar is clearly distinguishable centered at ∼62km (∼100mbar) altitude level. On average, the cold collar is more than 15K colder than the pole, but its specific temperature varies with time. In the three orbits under investigation the South Polar Vortex appears as a vertically extended hot region close to the pole and squeezed by the cold collar between altitudes 55 and 67km but spreading equatorwards at about 74km. Both the instantaneous temperature maps and their zonal averages show that the top altitude limit of the thermal signature from the vortex is at ∼80km altitude, at least on the night-side of the planet. The upper part of the atmosphere (67–85km) is more homogeneous and has long-scale horizontal temperature differences of about 25K over horizontal distances of ∼2000km. The lower part (55–67km) shows more fine-scale structure, creating the vortex morphology, with thermal differences of up to about 50K over the same altitude range and ∼500km horizontal distances. This lower part of the atmosphere is highly affected by the upper cloud deck, leading to stronger local temperature variations and larger uncertainties in the retrieval. From the temperature maps, we also study the vertical stability of different atmospheric layers for the three vortex configurations. The static stability is always positive (ST>0) in the considered altitude range (55–85km) and in the whole polar vortex. The cold collar is the most vertically stable structure at polar latitudes, while the vortex and sub-polar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex exhibit lower stability values than their surroundings. The layer between 62 and 67km resulted to be the most stable. These results are in good agreement with conclusions from previous radio occultation analyses.
We report Venus image observations around the two maximum elongations of the planet at 2015 June and October. From these images we describe the global atmospheric dynamics and cloud morphology in the ...planet before the arrival of JAXA's Akatsuki mission on 2015 December 7. The majority of the images were acquired at ultraviolet wavelengths (380-410 nm) using small telescopes. The Venus dayside was also observed with narrowband filters at other wavelengths (890 nm, 725-950 nm, 1.435 mu m CO2 band) using the instrument PlanetCam-UPV/EHU at the 2.2 m telescope in Calar Alto Observatory. In all cases, the lucky imaging methodology was used to improve the spatial resolution of the images over the atmospheric seeing. During the April-June period, the morphology of the upper cloud showed an irregular and chaotic texture with a well-developed equatorial dark belt (afternoon hemisphere), whereas during October-December the dynamical regime was dominated by planetary-scale waves (Y-horizontal, C-reversed, and psi-horizontal features) formed by long streaks, and banding suggesting more stable conditions. Measurements of the zonal wind velocity with cloud tracking in the latitude range from 50degreesN to 50degreesS shows agreement with retrievals from previous works.
We analyze Jupiter observations between December 2015 and August 2016 in the 0.38–1.7 μm wavelength range from the PlanetCam instrument at the 2.2 m telescope at Calar Alto Observatory and in the ...optical range by amateur observers contributing to the Planetary Virtual Observatory Laboratory. Over this time Jupiter was in a quiescent state without notable disturbances. Analysis of ground‐based images and Hubble Space Telescope observations in February 2016 allowed the retrieval of mean zonal winds from −74.5° to +73.2°. These winds did not change over 2016 or when compared with winds from previous years with the sole exception of intense zonal winds at the North Temperate Belt. We also present results concerning the major wave systems in the North Equatorial Belt and in the upper polar hazes visible in methane absorption bands, a description of the planet's overall cloud morphology and observations of Jupiter hours before Juno's orbit insertion.
Plain Language Summary
We present a characterization of Jupiter clouds and their dynamics prior to Juno's arrival. We present results based on observations with our own high‐resolution instrument PlanetCam, Hubble Space Telescope images acquired in February 2016, and analysis of high‐quality images provided by amateur astronomers using small telescopes. Before Juno's arrival to Jupiter its atmosphere behaved in a normal way without major convective outbreaks or changes in its usual belts and bands. Juno's first perijove characterized Jupiter at a time of usual behavior of the planet. Zonal winds were similar to previous years except for high values of the wind velocity at the most intense jet stream in the planet in the North Temperate latitudes which reached values of 157 m/s. We also study two systems of planetary‐scale waves in the planet: The first system is north to the equator in the North Equatorial Belt and is characterized by a regular pattern of large dark features in the planet. These are regions of reduced cloud content formed by an atmospheric wave. The second system is an undulatory pattern in the polar hazes that is best observed in the southern hemisphere. Both are characterized for later comparisons with results from the Juno mission.
Key Points
We present the overall cloud morphology of Jupiter over 2016 from images in the spectral range 0.38–1.7 micrometers
We characterize the equatorial hot spots and present snapshots of the polar regions providing context for observations from Juno
We measured zonal winds from December 2015 to June 2016 spanning the latitude range 74.5°S–73.2°N without variability over this period
Soil nitrogen mineralisation (N
), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net N
) ...varies with soil properties and climate. However, because most global-scale assessments of net N
are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net N
across 30 grasslands worldwide. We find that realised N
is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential N
only weakly correlates with realised N
, but contributes to explain realised net N
when combined with soil and climatic variables. We provide novel insights of global realised soil net N
and show that potential soil net N
data available in the literature could be parameterised with soil and climate data to better predict realised N
.
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