On the clouds and ammonia in Jupiter’s upper troposphere from Juno JIRAM reflectivity observations

ABSTRACT We analyse spectra measured by the Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission) in the 3150–4910 cm−1 (2.0–3.2 μm) range during the perijiove passage of 2016 August. Despite modelling uncertainties, the quality and the relative uniformity of the data set allow us to determine several parameters characterizing the Jupiter’s upper troposphere in the latitude range of 35°S–30°N. Ammonia relative humidity at 500 millibars varies between 5 per cent to supersaturation beyond 100 per cent for about 3 per cent of the processed spectra. Ammonia appears depleted over belts and relatively enhanced over zones. Local variations of ammonia, arguably associated with local dynamics, are found to occur in several locations on the planet (Oval BA, South Equatorial Belt). Cloud altitude, defined as the level where aerosol opacity reaches unit value at 3650 cm−1 (2.74 μm), is maximum over the Great Red Spot (>20 km above the 1 bar level) and the zones (15 km), while it decreases over the belts and towards higher latitudes. The aerosol opacity scale height suggests more compact clouds over zones and more diffuse clouds over belts. The integrated opacity of clouds above the 1.3-bar pressure level is found to be minimum in regions where thermal emission of the deeper atmosphere is maximum. The opacity of tropospheric haze above the 200-mbar level also increases over zones. Our results are consistent with a Hadley-type circulation scheme previously proposed in literature for belts and zones, with clear hemisphere asymmetries in cloud and haze.

Equatorial belt vapour measurements in the upper TTL under superpressure balloon during STRATEOLE 2 pre-campaign: tape recorder effect, role of waves and deep convection.

<p>STRATEOLE 2 is a French-American project based on superpressure balloon borne measurements to study dynamics and processes in the TTL and the lower stratosphere of equatorial regions. One single flight of these balloons (of a duration of about 80 days) can make several turns of the Earth.</p><p>Here we present water vapour measurements by the Pico-SDLA infrared laser spectrometer on-board the TTL 2 gondola. The float altitude was of about 19 km during the technical campaign of STRATEOLE 2, providing measurements at the top of the TTL or the lower stratosphere. In this presentation, we analyse the tape recorder signal at a constant altitude during the 80 days of flight. We compute an anomaly of the <em>in situ</em> water vapour measurements with respect to a regional/temporal satellite-borne mean climatology from Aura MLS. It allows to analyse the local measurements by Pico-SDLA with respect to what is expected at a given position and a given time. The obtained contrast allows the positioning of observations with respect to local climatology and therefore, the identification of singular events responsible for modulation of the local water vapour content. Our analysis shows that a long wet anomaly above the Pacific Ocean is explained by the balloon “surfing” on a warm perturbation of a Kelvin wave. Concurrently, a dry anomaly is put to the fore over the Indian Ocean, associated to a packet of gravity waves cold perturbations. The balloon has flown twice above the Maritime Continent. For each passage, a short scale succession of dry and wet anomalies is shown, indicating a possible influence of local deep convection. This influence is studied further using satellite borne cloud top data.</p>

Long-term Cycles of Variability of Jupiter’s Atmosphere from Ground-based Infrared Observations

<p>Jupiter’s atmosphere displays some of the most dramatic weather of any planet in our Solar System, with cycles of activity changing the upper tropospheric and stratospheric temperatures, aerosols, and cloud structures through physical processes that are not yet well understood. In the troposphere, Jupiter’s banded structure undergoes dramatic planetary-scale disturbances that can evolve over short timescales changing its appearance completely at a range of altitudes, from the cloud tops (~500 mbar) to the deeper levels (1-4 bar). Some of these tropospheric variations seem to occur randomly, like the impressive fading and revival of the South Equatorial Belt at 7°-17° S (planetocentric latitude), while others follow a periodic pattern, like the North Equatorial Belt expansions at 7°-17° N (with a ~4.5-year periodicity), the Equatorial Zone disturbances (~7-year period) within ±7° of the equator (Antuñano et al. 2018 doi:  https://doi.org/10.1029/2018GL080382) and the convective outbreaks at 21° N in the North Temperate Belt (~5-year period) (Antuñano et al., 2019 doi: https://doi.org/10.3847/1538-3881/ab2cd6). In the stratosphere, Jupiter’s equatorial and off-equatorial temperature and winds at 10-20 mbar exhibit a remarkable 4-5-year periodic oscillation with height forced by waves produced from tropospheric meteorological activity at the equatorial latitudes.</p> <p>Here we use almost 40 years (more than 3 jovian years) of ground-based infrared observations captured at NASA’s Infrared Telescope Facility (IRTF), the Very Large Telescope (VLT) and Subaru between 1980 and 2019 in a number of filters spanning from 7.9 to 24.5 µm.  These filters sample upper tropospheric and stratospheric temperatures and aerosols via collision-induced hydrogen and helium absorption, and emission from stratospheric hydrocarbons.  This long-term time series is used to (i) understand the impact of the previously mentioned tropospheric activity on the periodicity of the stratospheric temperature oscillations, (ii) characterize the long-term variability of Jupiter’s atmosphere at different altitudes in the upper troposphere and stratosphere, and (iii) investigate the long-term thermal, chemical and aerosol changes in Jupiter’s troposphere. In particular, we generate Lomb-Scargle periodograms and apply a Wavelet Transform analysis to our dataset to look for potential periodicities on the brightness temperature variability in different filters and compare them to previously reported cyclic activity at visible wavelengths (sensing the ammonia cloud top at ~500 mbar) and 5 µm (sensing the 1-4 bar pressure level). Finally, a Principal Component Analyses (PCA) is also performed to analyse the correlation of the brightness temperature variations at different belts and zones.</p>

Two new species of Luisia (Vandeae, Orchidaceae) from the Andaman and Nicobar Islands, India

The Andaman and Nicobar Islands are the largest archipelago system in the Bay of Bengal, consisting of 572 islands and islets. Being situated between two major biodiversity hotspots, namely the Indo-Burma and Sundaland Biodiversity Hotspots, endows it with an unmatched distribution of plants with representatives of the Indian, Myanmar, Malaysian and Indonesian floras (Balakrishnan & Ellis 1996). Nearly 2100 species of angiosperms have been reported from the islands, of which about 11% are strictly endemic (Balakrishnan & Ellis 1996). As these islands are situated in the Equatorial belt and are exposed to marine impacts having a warm and humid tropical climate, the entire area is suitable for growth of orchids. The Andaman and Nicobar Islands harbour about 158 species of orchids, of which 23 species are endemic (Karthigeyan et al. 2014, Singh et al. 2019).

A reduced stochastic model of core surface dynamics based on geodynamo simulations

SUMMARYWe make use of recent geodynamo simulations to propose a reduced stochastic model of the dynamics at the surface of Earth’s core. On decadal and longer periods, this model replicates the most energetic eigen directions of the geodynamo computation. Towards shorter timescales, it proposes a compensation for weaknesses of these simulations. This model furthermore accounts for the signature, in the geomagnetic secular variation, of errors of representativeness associated with unresolved processes. We incorporate the reduced stochastic model into a geomagnetic data assimilation algorithm—an augmented state ensemble Kalman filter—and apply it to re-analyse magnetic field changes over the period 1880–2015. Errors of representativeness appear to be responsible for an important fraction of the observed changes in the secular variation, as it is the case in the dynamo simulation.Recovered core surface motions are primarily symmetric with respect to the equator. We observe the persistence of the eccentric westward gyre over the whole studied era and vortices that partly follow isocontours of the radial magnetic field at the core surface. Our flow models provide a good fit to decadal changes in the length-of-day and predict its interannual variations over the period 1940–2005. The largest core flow acceleration patterns are found in an equatorial belt below 10° in latitude and are associated with non-axisymmetric features. No systematic longitudinal drift of acceleration patterns is found, even over the past decades where satellite data are available. The acceleration of the high-latitude westward jet in the Pacific hemisphere is, during the satellite era, a factor 5 smaller than previously reported and its structure shows some evidence for equatorial asymmetry. The era of continuous satellite records provides enhanced contrast on the rapid core flow variations. The proposed assimilation algorithm offers the prospect of evaluating Earth-likeness of geodynamo simulations.

Global Assessment of Climate-Driven Susceptibility to South American Leaf Blight of Rubber Using Emerging Hot Spot Analysis and Gridded Historical Daily Data

South American leaf blight (SALB) of Para rubber trees (Hevea brasiliensis Muell. Arg.) is a serious fungal disease that hinders rubber production in the Americas and raises concerns over the future of rubber cultivation in Asia and Africa. The existing evidence of the influence of weather conditions on SALB outbreaks in Brazil has motivated a number of assessment studies seeking to produce risk maps that illustrate this relationship. Subjects with dynamic and cyclical spatiotemporal features need to embody sufficiently fine spatial resolution and temporal granulation for both input data and outputs in order to be able to reveal the desired patterns. Here, we apply emerging hot spot analysis to three decades of gridded daily precipitation and surface relative humidity data to depict their temporal and geographical patterns in relation to the occurrence of weather conditions that may lead to the emergence of SALB. Inferential improvements through improved handling of the uncertainties and fine-scaled temporal breakdown of the analysis have been achieved in this study. We have overlaid maps of the potential distribution of rubber plantations with the resulting dynamic and static maps of the SALB hot spot analysis to highlight regions of distinctly high and low climatic susceptibility for the emergence of SALB. Our findings highlight the extent of low-risk areas that exist within the rubber growing areas outside of the 10° equatorial belt.