Spelling suggestions: "subject:"moins convection""
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Simulations of moist convection using the quasi-elastic equationsBopape, M.M. (Mary-Jane Morongwa) January 2013 (has links)
Cloud Resolving Models use microphysics parameterisation schemes for the simulation
of clouds. The thesis reports on the introduction of two single-moment
Bulk Microphysics Parameterisation (BMP) schemes in the Nonhydrostatic -
coordinate Model (NSM). The rst BMP is known as the PURDUE-LIN scheme,
and can be used with ve (excluding graupel) or six (including graupel) classes
of the water substance. The second scheme was developed using the PURDUELIN
scheme as a starting point, and is known as SBU-YLIN. Graupel and snow
share a category and processes in the latter scheme. Simulations of two hours
in length are made, with convection initiated through inserting a warm thermal
into a cooler environment, using a six-class and ve-class PURDUE-LIN and the
SBU-YLIN BMPs. The simulations are performed at various horizontal resolutions
of 500 m, 1 km and 2 km. The six-class PURDUE-LIN scheme simulates
more rainfall than the ve-class PURDUE-LIN and the SBU-YLIN schemes.
The SBU-YLIN scheme generally rains the least, looses the least water vapour
to hydrometeors and warms up the least. The PURDUE-LIN schemes simulate
two convective cells in a no shear environment. The maximum updrafts
associated with the rst cell (triggered by the warm perturbation) are similar
in all the simulations. The second cell is triggered by a cold pool. While the cold pool is stronger in the six-class PURDUE-LIN scheme simulations, the updrafts
in the second cell are stronger in the ve-class PURDUE-LIN simulation.
The SBU-YLIN scheme generally simulates just one cell because of a weak cold
pool. Simulations were also made for three di erent periods dominated by suppressed
convection with deep convection at the beginning and end of the three
periods, forced with large scale tendencies observed during the Tropical Ocean
Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA
COARE). The NSM is able to capture di erences in the suppressed and deep
convection periods. Qualitatively, the simulations provide new insight into the
interplay between cloud microphysics and cloud dynamics, and points out the
potential for better describing the uncertainty range associated with projections
of future climate change, through the improvement and stochastic application
of cloud microphysics schemes. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Geography, Geoinformatics and Meteorology / unrestricted
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Numerical study on the self-aggregation of moist convection in radiative-convective equilibrium / 放射対流平衡下における湿潤対流の自己集合化に関する数値的研究Yanase, Tomoro 23 March 2022 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第23712号 / 理博第4802号 / 新制||理||1687(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 竹見 哲也, 准教授 重 尚一, 教授 榎本 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
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NUMERICAL SIMULATIONS OF ATMOSPHERIC DYNAMICS ON THE GIANT PLANETSLian, Yuan January 2009 (has links)
The giant planets exhibit banded zonal jet streams that have maintained theirstructures over decades. There are long-standing questions: how deep the windstructures extend? What mechanisms generate and maintain the observed winds?Why are the wind structures so stable? To answer these questions, we performedthree-dimensional numerical simulations of the atmospheric flow using the primitiveequations.First, we use a simple Newtonian cooling scheme as a crude approach to gener-ate atmospheric latitudinal temperature differences that could be caused by latentheating or radiation. Our Jupiter-like simulations show that shallow thermal forcingconfined to pressures near the cloud tops can produce deep zonal winds from thetropopause all the way down to the bottom of the simulated atmosphere (a fewhundred bars). These deep winds can attain speeds comparable to the zonal jetspeeds within the shallow, forced layer; they are pumped by Coriolis accelerationacting on a deep meridional circulation driven by the shallow-layer eddies.Next, we explicitly include the transport of water vapor and allow condensationand latent heating to occur whenever the water vapor is supersaturated. Our simu-lations show that large-scale moist convection associated with condensation of watervapor can produce multiple zonal jets similar to those on the gas giants (Jupiterand Saturn) and ice giants (Uranus and Neptune). For plausible water abundances(3-5 times solar on Jupiter/Saturn and 30 times solar on Uranus/Neptune), oursimulations produce about 20 zonal jets for Jupiter and Saturn and 3 zonal jetson Uranus and Neptune. Moreover, these Jupiter/Saturn cases produce equatorialsuperrotation whereas the Uranus/Neptune cases produce equatorial subrotation,consistent with the observed equatorial jet direction on these planets. Sensitiv-ity tests show that the water abundance is the controlling factor; modest waterabundances favor equatorial superrotation, whereas large water abundances favorequatorial subrotation. This provides a possible mechanism for the existence ofequatorial superrotation on Jupiter and Saturn and the lack of superrotation onUranus and Neptune.
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Characteristics of deep moist convection and rainfall in cut-off lows over South AfricaMuofhe, Tshimbiluni Percy 20 September 2019 (has links)
MENVSC / Department of Geography and Geo-Information Sciences / Out of all rain-producing weather systems, cut-off lows (COLs) are linked with the occurrence
of high impact rainfall and in some cases short-lived floods which can last for 24 hours over
South Africa. This study examined the characteristics associated with the present occurrence
of the severe COL systems over South Africa from 2011 to 2017. The accuracy of the 4.4 km
Unified Model (UM) which is currently in use for simulating areas of deep moist convection in
South Africa was evaluated. The UM simulated geopotential height at 500 hPa as well as the
associated 24 hours precipitation which were compared against the daily fields of geopotential
height and 6-hourly precipitation from the European Centre for Medium-Range Weather
Forecasts (ECMWF). COL events were categorized and analyzed according to the associated
surface circulation patterns at 850 hPa. The seasonal distribution and duration of the systems
over northern (10°E-33°E //22°-32°S) and southern (10°E-33°E //32°-35°S) regions of the
study area were also analyzed. Results show COL systems shifting with season towards the
north eastern parts of the country, with an increased number of events during the austral winter
season during the study period. Systems which lasted for long time were observed during the
austral winter and spring seasons. The UM tends to simulate areas of heavy precipitation
accurately with poor simulation during the initial stages of the systems. The UM provided a
more realistic-looking closed geopotential height and rainfall fields for systems which are
coupled with a cold front at the surface. Application of the knowledge about the evolution in
the characteristics of COL events from this study can improve the operational forecasting of
these weather systems over the country. / NRF
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