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Global retrievals of upper-tropospheric phosphine from the Cassini/CIRS Jupiter encounterParrish, Paul David January 2004 (has links)
On December 30th 2000, the Cassini-Huygens spacecraft reached the perijove milestone in its continuing journey to the Saturnian system. During an extended six-month encounter, the Composite Infrared Spectrometer (CIRS) returned spectra of the Jovian atmosphere, rings and satellites from 10 to 1400 cm^-1 (1000 to 7 µm) at a programmable spectral resolution of 0.5 to 15 cm^-1. The improved spectral resolution of CIRS over previous infrared instrument-missions to Jupiter, the extended spectral range and higher signal-to-noise performance provide significant advantages over previous data-sets. Both optimal-estimation retrieval and radiance-differencing are used to investigate the global variation of upper-tropospheric temperature, ammonia, phosphine and cloud opacity between ± 60˚ latitude. The analysis methods are shown to successfully reproduce Jovian conditions with results consistent with previous investigations. The composition results in particular are well characterised and suggest an important role played by mixing and transport within the upper-troposphere. Interpretation and validation of the retrieved results is conducted via the construction of a simple dynamic model incorporating transport, diffusion and (photo)chemistry.
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Heat waves in South Africa: Observed variabilty, structure and trendsMbokodo, Innocent Lifa 18 May 2017 (has links)
MENVSC (Climatology) / Department of Geography and Geo-Information Sciences / Heat waves are warm extreme temperature events that have environmental and socio-economic impacts in many regions across the world. Negative impacts of warm extreme temperatures over South Africa necessitate the need to study the nature of heat waves. Observations and satellite datasets are analysed in the investigation of the nature and trends of heat waves over South Africa in the present (1983-2012) and future (2010-2039, 2040-2069, 2070-2099) climates. Case study and composite analysis of National Centers for Environmental Prediction datasets were done using the Grids Analysis and Display Systems to get an in-depth understanding of the structure of heat waves in South Africa. Future climate model output obtained from the Conformal Cubic Atmospheric Model was used for future heat wave trends in South Africa. The simulations were made using the Representative Concentration Pathways 4.5 and 8.5. Heat waves are unusual events in the present climate (1983-2012) over much of the country, with 20 of the selected 24 stations experiencing an average of less than one heat wave per season. Heat waves are also more frequent and last longer during warm phase of El Niño-Southern Oscillation (ENSO) than in cool phase of ENSO with the north-east being the most prone region. Composite analysis of 500 hPa omega indicates subsidence over the interior of South Africa in both phases of ENSO. Heat waves in South Africa are localized and associated with a middle level high pressure system that persists over the interior inducing anticyclonic flow and subsidence. The anticyclonic circulation over a region experiencing heat wave weakens with decreasing height over land areas which may be due to frictional forces at the surface and the high is placed further south-east at the surface. Advection of dry continental northerly winds also contributes to high maximum temperatures during heat waves in the interior. Maximum temperatures are expected to increase drastically from the present-day climate to the 2070 – 2099 period, with an average increment of about 8°C during DJF in much of the central interior. As a result, heat wave occurrences are expected to be higher in the future warmer climates when climate change signal is higher. Most increases are expected for heat waves lasting for a week than those lasting for over 2 weeks. CCAM outputs also indicated that heat waves in South Africa are expected to last longer and become more intense during the future warmer climates. Longer lasting and more intense heat waves are expected over the Karoo than in other parts of the country.
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