Divergence structures associated with the spectrum of precipitating systems in the subtropics and midlatitudes are not well documented. A mesoscale model (MM5) is employed to quantify the relative importance different baroclinic environments have on divergence profiles for common storm types in southeast Texas, a subtropical region. Divergence profiles averaged over a 100 x 100 nested grid with 3-km grid spacing are calculated from the model-derived wind fields for each storm. The divergence profiles simulated for selected storms are consistent with those calculated from an S-band radar using the velocity-azimuth display (VAD) technique. Divergence profiles from well-modeled storms vary in magnitude and structure across the spectrum of baroclinicities and storm types common in southeast Texas. Barotropic storms more characteristic of the Tropics generate the most elevated divergence (and thus diabatic heating) structures with the largest magnitudes. As the degree of baroclinicity increases, stratiform area fractions increase while the levels of non-divergence (LNDs) decrease. However, some weakly baroclinic storms contain stratiform area fractions and divergence profiles with magnitudes and LNDs that are similar to barotropic storms, despite having lower tropopause heights and less deep convection. Additional convection forms after the passage of some of the modeled barotropic and weakly baroclinic storms that contain elevated divergence signatures, circumstantially suggesting that heating at upper-levels may cause diabatic feedbacks that help drive regions of persistent convection in the subtropics. Applying a two-dimensional stratiform-convective separation algorithm to MM5 reflectivity data generates realistic stratiform and convective divergence signals. Stratiform regions in barotropic storms contain thicker, more elevated mid-level convergence structures with larger magnitudes than strongly baroclinic storms, while weakly baroclinic storms have LNDs that fall somewhere in between with magnitudes similar to barotropic storms. Divergence profiles within convective regions typically become more elevated as baroclinicity decreases, although variations in magnitude are less coherent. These simulations suggest that MM5 adequately captures mass field perturbations within convective and stratiform regions, the latter of which produces diabatic feedbacks capable of generating additional convection. As a result, future research determining the climatological dynamic response caused by divergence profiles in MM5 may be feasible.

This dissertation establishes a precipitation climatology for common storm types and structures in southeast Texas, investigating diurnal, seasonal, and interannual rainfall variations in addition to climatological differences in raindrop size distributions and storm divergence profiles. Divergence profiles observed by an S-band, Doppler radar are compared to ensemble simulations of ten precipitating systems occurring in warm season, weakly baroclinic, and strongly baroclinic environments. Eight triply-nested mesoscale model simulations are conducted for each case using single- and double- moment microphysics with four convective treatments (i.e., two convective parameterizations and explicit vs. parameterized convection at 9 km). Observed and simulated radar reflectivities are objectively separated into convective, stratiform, and non-precipitating anvil columns and comparisons are made between ensemble mean echo coverages and levels of non-divergence (LNDs). In both the model and observations, storms occurring in less baroclinic environments have more convective rain area, less stratiform rain area, and more elevated divergence profiles. The model and observations agree best for well-organized, leading-line trailing stratiform systems. Excessive convective rain area and elevated LNDs are simulated for several less organized cases. Simulations parameterizing convection on the intermediate grid produced less elevated divergence profiles with smaller magnitudes compared to their explicit counterparts. In one warm season case, double-moment microphysics generated lower LNDs associated with variations in convective intensity and depth, detraining less ice to anvil and stratiform regions at midlevels relative to a single-moment scheme. Similarly, mesoscale convective vortex simulations employing an ensemble-based versus a single-closure convective parameterization produced the least elevated heating structures (closer to observed) resulting in the weakest midlevel vortices. Finally, this dissertation is unique in that some of the data collection and a portion of the analysis involved 95 undergraduates in a five-year research and education program, the Student Operational ADRAD Project (SOAP). In addition to documenting the program's structure and implementation, student-reported experiences, confidence, and interest in performing SOAP tasks are also analyzed. Students participating in SOAP for multiple years were significantly more confident in performing SOAP tasks, more likely to obtain science or meteorology-related employment upon graduation, and more likely to matriculate to graduate programs, suggesting programs like SOAP have a strong influence on students' career outcomes and self-efficacy.

Northwestern Mexico is characterized by different metallogenic provinces that are included along the Basin and Range, the Sierra Madre Occidental, and the Baja California geological provinces. With the purpose of contribute to the current understanding of the mineralizing processes, the present study focused on two important copper metallogenic provinces: the Cananea Porphyry District in Sonora, and the Sediment-hosted Stratiform Copper- and Mn-deposits in Baja California Sur. The U-Pb zircon ages from the mineralizing porphyries from Cananea district suggest a continued magmatic activity period of ~6 Ma. Also suggests a period of ~20 Ma for the entire magmatic activity in the district. The Re-Os molybdenite ages demonstrate five well-constrained mineralization events in the district; the main mineralization is constrained over a short period of time (~4 Ma). The new molybdenite age from the Pilar deposit documents the oldest mineralizing pulse, suggesting possibly the initiation of the Laramide mineralization in northern Sonora. A detailed study of Mariquita porphyry Cu and Lucy Cu-Mo deposits in the Cananea district was performed. Four hydrothermal stages were defined in Mariquita, whereas a single hydrothermal pulse characterizes Lucy. Emplacement depths between 1-1.2 km, and temperatures between 430-380ºC characterized the mineralization from Mariquita, whereas deeper emplacement depths and higher mineralization temperatures characterized Lucy. The stable isotope systematic and fluid inclusion data determined that the mineralizing fluids in Mariquita deposit are essentially magmatic during the earlier hydrothermal stages, whereas the last stage is the mixing between magmatic and winter meteoric-waters. The mineralizing fluids from Lucy deposit are magmatic in origin. A comprehensive study was performed in the Cu-Co-Zn-Mn ineralization of the Boléo District, and Mn-oxide mineralization along the eastern coast Baja California Sur. The REE and trace element in the Mn-oxides demonstrated the exhalative nature of the mineralizing hydrothermal fluids, and exclude the hydrogenous nature. The stable isotope systematic in ore and gangue minerals, along with the Cu-isotope data helped to decipher the nature of mineralizing and non-mineralizing fluids. The application of Pb, Sr and Re-Os isotope systems was applied to constrain the nature of the fluids involved during the mineralization processes and that the metal sources.

The Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) is a truck-mounted C-band, Doppler radar that was deployed during the Dynamics of the Madden-Julian Oscillation (DYNAMO) / Cooperative Indian Ocean Experiment on interseasonal variability in the year 2011 (CINDY2011) campaign on Addu Atoll, Maldives. One of SMART-R’s objectives was to provide continuous volume scans of precipitating clouds during all phases of the Madden-Julian Oscillation (MJO) for the full duration of the campaign. Data from SMART-R is available for 2 October 2011 through 9 February 2012. Every 10 minutes a full volume scan was produced, which was subsequently run through quality control algorithms that, among other filters, performed a calibration correction, noise filtering, and an attenuation correction. It was observed that data from SMART-R appeared to be slanted towards the WNW, and after analysis, a 0.75◦ tilt correction was applied towards azimuth 285◦. The data was then converted into Cartesian coordinates and an additional noise filter was applied. NETCDF files with radial velocities and corrected reflectivity were produced. From the reflectivity observations, a suite of products including rain maps, echo- top heights and convective/stratiform separations were produced. A modified version of the convective/stratiform separation was developed in an attempt to classify shallow and weak convection more correctly. The modified algorithm utilizes an isolation parameter set to 10 km to the north, south, east, and west, a 10-dBz echo-top height threshold set to 9 km, and a 16-dBz reflectivity threshold at 3 km to ensure only isolated, shallow, and weak rain originally classified as stratiform, is reclassified as convection. Analyses of these products clearly suggest two MJO events occurring in October and November as indicated by the Wheeler and Hendon Multivariate MJO index. While stratiform rain almost always encompassed a larger area of the radar domain, convective rain was the larger producer of rain with the exception of active MJO periods. In addition, echo-top height counts are observed to increase in both vertical structure and frequency as the MJO initiates and becomes active over the radar domain. Possible connections are also made between echo-top height data and humidity retrievals from soundings launched on Addu Atoll. It appears that during MJO initiation, convective echo tops lead the moistening of the mid troposphere, while during suppressed phases, the convective echo tops lag behind the moistening of the mid troposphere. Wind shear also appears to be weaker during an active MJO event, and increase as the active MJO exits the region. From these observations, as well as other rain statistics including the diurnal cycle, indicators for a localized MJO index are proposed that are based on local radar and sounding data, rather than satellite and reanalysis observations of wind and outgoing long-wave radiation.

Student Number : 0201438A - PhD thesis - School of Geosciences - Faculty of Science / This project focuses on the Upper Critical and Lower Main Zones in the eastern Bushveld Complex, South Africa. Lithological and stratigraphic information show that there are distinct differences at this level between the eastern and western limbs of the complex. Geochemical studies are centred on the Merensky and Bastard Cyclic Units in which the platiniferous Merensky Reef occurs. A major geochemical hiatus occurs in the Bushveld Complex at the level of the platiniferous Merensky Reef, close to the Critical/Main Zone boundary. The origin of this hiatus and its relation to mineralisation has not been fully resolved. Geochemical parameters are investigated that allow minerals in the Merensky and Bastard Cyclic Units to be classified as originating from either Critical or Main Zone magmas. Modelling of element ratios (Ni/Y, Cr/Ni, Cr/Co, Y/Co, Cr/V, Co/V and Cr/MgO) demonstrates the varying reliability of using ratios as geochemcial tools to constrain magma influxes within a chamber. However, it is shown that the Cr/MgO ratio is effective in determining real differences across the Critical/Main Zone boundary that are independent of lithology. In addition, initial Sr isotope ratios for plagioclase are significantly different in Critical and Main Zone rocks. Geochemical data through the Merensky and Bastard Cyclic Units indicate that orthopyroxene that originated from magma with composition like that of the Critical Zone magma sometimes occurs together with plagioclase that originated from Main Zone magma. In detail, in the pyroxenite at the base of the Merensky Unit, both plagioclase and orthopyroxene display Critical Zone signatures, but in the overlying part of the Merensky Cyclic Unit, plagioclase increasingly shows a Main Zone signature, whereas orthopyroxene continues to display a Critical Zone signature. Similarly, in the Bastard pyroxenite, Sr isotopes and absolute Sr in plagioclase display a range of values from Main Zone to Critical Zone, but orthopyroxene consistently displays Critical Zone affinity. These observations of mineral disequilibrium clearly show that the two major minerals in the Merensky and Bastard Cyclic Units were formed from two different, but coexisting, magmas. A model that accounts for this disequilibrium is proposed here. It invokes the influx of Main Zone magma at the level of the base of the Merensky unit that dispalced the Critical Zone magma upward, but the two magmas did not mix. The latter continued to crystallise orthopyroxene which sank through the Main Zone influx, due to its density contrast. These crystals collected on the crystal pile to form the Merensky pyroxenite. The Main Zone magma, into which the cumulus Critical Zone orthopyroxene accumulated, crystallised interstitial plagioclase that had a Main Zone Sr isotopic ratio. Whole-rock, major element geochemical data show that a variable proportion of the plagioclase in both the Merensky and Bastard pyroxenites is cumulus. It is inferred to have accumulated with orthopyroxene and has a Critical Zone initial Sr isotope ratio. Thus the two pyroxenites now yield a mixed Sr isotopic signature of Critical Zone cumulus and Main Zone intercumulus and possibly cumulus plagioclase that varies along strike. Above the two pyroxenites, the Sr signature of the norites and anorthosites of both cyclic units is dominated by cumulus plagioclase from the Main Zone magma. It is concluded that the variations in initial Sr isotope ratios do not result from mixing of magmas, but result from accumulation of orthopyroxene and plagioclase from a higher, isotopically distinct layer of magma into an underlying layer. The Merensky and Bastard Cyclic Units therefore display features of Critical or Main Zone magma characteristics depending upon which chemical parameter is considered. These cycles are therefore classified as a Transitional Unit.

Title: Frequency analysis of precipitation amounts Author: Mgr. Zuzana Rulfová Department: Department of Atmospheric Physics Supervisor: RNDr. Jan Kyselý, Ph.D., Institute of Atmospheric Physics CAS Abstract: This thesis deals with analysing characteristics of mean and extreme precipitation in observations and regional climate models (RCMs) with respect to their convective and stratiform origin. An algorithm for subdivision of precipitation amounts into predominantly convective and stratiform using station weather data is proposed and evaluated. The time series of convective and stratiform precipitation from the Czech Republic over 1982-2010 are used for analysing basic climatological characteristics of precipitation, including extremes, and evaluating RCMs from the ENSEMBLES project. Projected changes of convective and stratiform precipitation in Central Europe (the Czech Republic) are analysed using data from RCM simulations from the EURO-CORDEX project. The last part of the thesis introduces a new statistical model for analysing precipitation extremes. This model takes advantage from knowledge of origin of precipitation extremes. In future climate we could expect more convective and stratiform precipitation amounts in all seasons except summer, when climate models project decline in amounts of stratiform...

京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13202号 / 論理博第1561号 / 新制||理||1635(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 塩谷 雅人, 准教授 重 尚一, 教授 秋友 和典 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

The Madden-Julian Oscillation (MJO), a tropical phenomenon that exists on the time scale of 30-90 days, commonly initiates over the Indian Ocean and slowly propagates into the western Pacific as a series of convective events, which have time scales on the order of hours or days. These events and the overall MJO convective envelope may interact with convectively coupled waves such as Kelvin waves that propagate more rapidly eastward with time scales of 3-5 days. Radar and sounding data collected during the DYNAMO/AMIE/CINDY2011 field campaign from October 2011 to February 2012 in the central Indian Ocean are used to study the interaction between Kelvin waves and the MJO in terms of atmospheric and cloud properties. The focus is on characterizing the precipitation characteristics, convective cloud spectrum, and atmospheric profiles of Kelvin waves during the active and suppressed phases of the MJO to gain insight on MJO initiation. Characteristics of waves identified using different satellite thresholds and filtering methods are compared. Composites of the radar and sounding observations are calculated for a total of ten Kelvin waves and three MJO events that occurred during the field campaign. Analyzed radar products include convective-stratiform classification of rain rate, rain area, and echo-top heights, as well as cloud boundaries. Sounding data includes profiles of wind speed and direction and relative humidity. Kelvin waves that occur during the suppressed MJO are convectively weaker than Kelvin waves during the active MJO, but display previously documented structure of low-level convergence and a moist atmosphere prior to the wave passage. During the active MJO, Kelvin waves have stronger convective and stratiform rain, and the entire event is longer, suggesting a slower moving wave. The Kelvin wave vertical structure is somewhat overwhelmed by the convective envelope associated with the MJO. When the MJO is developing, the Kelvin wave displays a moisture-rich environment after the passage, providing deep tropospheric moisture that is postulated to be important for the onset of the MJO. The convective cloud population prior to MJO initiation shows increased moisture and a population of low- to mid-level clouds. The moisture precedes shallow convection, which develops into the deep convection of the MJO, supporting the discharge-recharge theory of MJO initiation. Additionally, enhanced moisture after the passage of the pre-MJO Kelvin wave could also support the frictional Kelvin-Rossby wave-CISK theory of MJO initiation. With a better understanding of the interaction between the initiation of the MJO and Kelvin waves, the relationships between the environment and the onset of the convection of the MJO can be improved.