Holocene Paleoenvironmental Reconstruction From Mexico\u27s Pacific Coast-A Paleotempestological Investigation

This dissertation examines the paleoenvironments of four lagoons from Mexico’s Pacific coast, with the aim of retrieving sediment deposition from storm surge events to determine long-term tropical cyclone (TC) records. Lagoons Agua Dulce, Boquita, Mitla, and Nuxco are located along a 700 km stretch in states Jalisco and Guerrero. Roughly 70 meters of sediment were collected and subjected to multiple proxies, including loss-on ignition, a microfossil survey, and geochemical analysis. Nuxco’s dynamism is caused by intense and prolonged rainfall (largely from TCs), responsible for increasing water level, opening the tidal inlet, and draining the site (termed “blowouts”). High amounts of shell hash entering Nuxco’s nearshore from ~1280-~530 yrs BP suggests turbulent conditions, likely from recurrent blowouts caused by a wet climate and frequent TCs. A decrease in nearshore hash from ~530 yrs BP to present suggests a more stable environment from a drier climate and less TCs. Mitla and Boquita’s backbarrier environments were formed ~5200 yrs BP during a period of stabilizing sea level. The longest core extracted from Mitla reveals peat alternating with lagoonal clay layers, indicating limnic environments (inferred 4430-4220 yrs BP, 4080, 3950, 3680-3480, 3170-3080, 2990-2870, 1570-present) triggered by increases in precipitation. Limnic phases show good temporal correlation to wet periods determined from coastal and upland paleorecords, and long term El Niño records, a main cause of wet conditions, along with frequent and wetter eastern north Pacific TCs. Mitla’s cores lack overwash evidence from TCs and tsunamis, posing questions regarding the documented attribution of clastic deposition to extreme events here. Similar to Mitla, Boquita’s sediments indicate changes in water level. Namely, a desiccated blue clay section adjacent to gray clay with low water and organic contents, and high Cl concentration, suggests low water level and dry conditions from ~3150-1030 yrs BP. While Laguna Agua Dulce is the only site susceptible to overwash, individual events cannot be deciphered due to its sandy sediments and typical resuspension from strong currents. Findings from this dissertation shed light on the insensitivity of these lagoons to overwash processes from extreme events, while improving regional paleoclimatological and paleoenvironmental records and understanding

Ocean Wave-Coherent Temperature and Humidity Near-Surface Vertical Distributions and Their Effect on Radar Performance over the Ocean

Large knowledge gaps concerning the effect of ocean surface waves on near-surface vertical distributions of temperature and humidity in the marine atmospheric surface layer exist due to practical limitations and sensor fidelity challenges of direct measurements. Wave effects on these distributions between the wave trough and crest are least studied within the literature. These scalar distributions influence atmospheric refractivity, which can lead to anomalous propagation of electromagnetic energy. Measurements of temperature and humidity are classically made using rocket- or radiosondes and fixed weather stations, and can utilize tethered profiling systems. However, these measurement systems have limitations when obtaining measurements near the sea surface. Consequently, boundary layer similarity models (i.e., Monin Obuhkov (MO) theory) are commonly employed to fill in these near-surface measurement gaps despite the documented shortcomings of these models in this region. To address this observational gap, this research develops a novel near-surface wave-coherent instantaneous profiling system (NWIPS) to aid in enriching our current knowledge regarding the influence of waves on near-surface vertical scalar distributions. Eighty minutes of wave-coherent instantaneous vertical scalar distributions were measured by NWIPS in an unstable atmosphere. It is the first attempt to obtain high resolution, wave-coherent vertical distributions of temperature and humidity within the lowest 3 m of altitude. Utilizing these measurements, the variability of near-surface vertical scalar distributions is investigated. These results are discussed in the context of their impact on propagation loss predictions for X-band and K-band frequencies. Comparisons between classical MO theory profiles and NWIPS measured profiles showed disagreement below 4 m, whereas above this altitude, there was good agreement. Comparisons between PL predictions for the two refractivity profiles revealed lower propagation loss at long range for MO theory, and differences are most significant for K-band. Below 4 m, distinct, persistent, vertical structure in both ten-minute and 80-minute ensembles and 80-minute wave phase-averaged vertical scalar profiles were observed. The complex structure in the mean temperature vertical distribution near the surface is consistent with prior laboratory and numerical studies. Variations in refractivity over wave phase showed the primary difference between refractivity profiles at the crest, trough, upslope, and downslope was the vertical shifting of the profiles resulting from the shifting surface. The phase-averaged profiles were also found to be steady over the 80-minute experiment consistent with the similar wave conditions during this time. The differences in the refractivity profiles for the various wave phases are shown to be relatively insignificant to X-band propagation predictions, while for K-band some discrepancies are observed over both flat and wavy surfaces. The differences resulting from the duct height shifting in range and/or the introduction of a wavy surface causes larger differences in propagation predictions than do changes in the refractivity profile with phase

The global monsoon system: research and forecast

The main objective of this workshop was to provide a forum for discussion between researchers and forecasters on the current status of monsoon forecasting and on priorities and opportunities for monsoon research. WMO hopes that through this series of quadrennial workshops, the following goals can be accomplished: (a) to update forecasters on the latest reseach findings and forecasting technology; (b) to update researchers on monsoon analysis and forecasting; (c) to identify basic and applied research priorities and opportunities; (d) to identify opportunities and priorities for acquiring observations; (e) to discuss the approach of a web-based training document in order to update forecasters on developments of direct relevance to monsoon forecasting

How Does Indian Monsoon Regulate the Northern Hemisphere Stationary Wave Pattern?

The Northern Hemisphere summer climate isstrongly affected by a circumglobal stationary Rossby wave train, which can be manifested by the first EOF mode of the geopotential height at 200 hPa. Interannual variation of this Northern Hemisphere wave (NHW) pattern has a significant impact on remarkably warm surface temperature anomalies over the North Atlantic, Northeast Europe, East Asia to Central-North Pacific, and America, particularly in 2018 and 2010. The NHW pattern is likely generated by atmospheric diabatic heating and vorticity forcing: diabatic heating is mainly confined in the Indian summer monsoon (ISM) precipitation region, whereas the anti-cyclonic vorticity forcing is distributed in the globe. The ISM is a well-known diabatic heat source; however, the main source of vorticity forcing has not been established. In general, the tropical vorticity anomaly comes from diabatic heating-induced atmospheric waves and randomly generated inherent internal waves. The linear baroclinic model experiment reveals that the NHW pattern can be generated by the westward propagating tropical waves generated by the ISM diabatic heat forcing

A numerical and observational study of the genesis of concentric eyewall hurricanes

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999.Includes bibliographical references (p. 195-202).This work attempts to understand the dynamics of the genesis of concentric eyewall hurricanes. More specifically, we focus on the effects of external eddy forcing associated with upper-level wave asymmetries in the environment of tropical cyclones, and through what processes these effects can be achieved. Our approach is a combination of numerical modeling and observational case studies. We have made use of two numerical models, namely a simple two-layer model and a two-dimensional cloud resolving non-hydrostatic model. The latter is called the full physics model for short. Owing to the lack of direct measurements of upper-level atmospheric conditions, we choose to use reanalysis data from National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR) and European Center for Medium-Range Weather Forecasts (ECMWF). A somewhat lengthy evaluation suggests that both datasets are marginally suitable for case studies of tropical cyclones. Our major conclusions are as follows: ** Numerical simulations from the simple and full physics models suggest that the genesis of concentric eyewall hurricane results from finite-amplitude wind induced surface heat exchange (WISHE) instability of the tropical atmosphere. ** The results from the full physics model suggest that the role of the eddy forcing is like the catalyst in a chemical reaction. The forcing helps manifest internal finite-amplitude instabilities which themselves are driven by surface enthalpy fluxes. ** The results from our extensive case studies suggest that a causal relationship does not always exist between environmental forcing and genesis of a secondary eyewall. Some cases, for example, Hurricane Allen of 1980, Hurricane Elena of 1985 and Hurricane Opal of 1995, show a good and clear relationship between their eyewall replacement cycles and their external forcings. Some cases, for example, Hurricane Gilbert of 1998 and Hurricane Andrew of 1992, show some degree of causal relationship. Some cases, for example, Hurricane Emily of 1993 and Hurricane Gabrielle of 1989, show a weak or close to no causal relationship. ** With the results of Hurricane Frederic of 1979 and results from concentric eyewall hurricanes, we can conclude that the interaction between a tropical cyclone and its upper-level synoptic environment is neither sufficient nor necessary for the genesis and development of concentric eyewall cycles in reality. ** The maps of isentropic potential vorticity (PV) only provide qualitative information on the occurrence of the interaction. The strength of the interaction should be determined quantitatively by the eddy PV fluxes which should be calculated in a storm-moving coordinate system. The discrepancy between the numerical results and the case studies' results leads us to hypothesis two mechanisms of the genesis. One is the interaction between a hurricane and the ocean underneath. The other is the tilting of high PV inner core with the storm and followed up projection of cyclonic vorticity down to the ocean surface.by Shangyao Nong.Ph.D

Tropical Cyclogenesis in a Tropical Wave Critical Layer: Easterly Waves

The development of tropical depressions within tropical waves over the Atlantic and eastern Pacific is usually preceded by a "surface low along the wave" as if to suggest a hybrid wave-vortex structure in which flow streamlines not only undulate with the waves, but form a closed circulation in the lower troposphere surrounding the low. This structure, equatorward of the easterly jet axis, is identified herein as the familiar critical layer of waves in shear flow, a flow configuration which arguably provides the simplest conceptual framework for tropical cyclogenesis resulting from tropical waves, their interaction with the mean flow, and with diabatic processes associated with deep moist convection. The recirculating Kelvin cat's eye within the critical layer represents a sweet spot for tropical cyclogenesis in which a proto-vortex may form and grow within its parent wave. A common location for storm development is given by the intersection of the wave's critical latitude and trough axis at the center of the cat's eye, with analyzed vorticity centroid nearby. The wave and vortex live together for a time, and initially propagate at approximately the same speed. In most cases this coupled propagation continues for a few days after a tropical depression is identified. For easterly waves, as the name suggests, the propagation is westward. It is shown that in order to visualize optimally the associated Lagrangian motions, one should view the flow streamlines, or stream function, in a frame of reference translating horizontally with the phase propagation of the parent wave. In this co-moving frame, streamlines are approximately equivalent to particle trajectories. The closed circulation is quasi-stationary, and a dividing streamline separates air within the cat's eye from air outside

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

Modern Climatology - Full Text

Climatology, the study of climate, is no longer regarded as a single discipline that treats climate as something that fluctuates only within the unchanging boundaries described by historical statistics. The field has recognized that climate is something that changes continually under the influence of physical and biological forces and so, cannot be understood in isolation but rather, is one that includes diverse scientific disciplines that play their role in understanding a highly complex coupled “whole system” that is the Earth’s climate. The modern era of climatology is echoed in this book. On the one hand it offers a broad synoptic perspective but also considers the regional standpoint as it is this that affects what people need from climatology, albeit water resource managers or engineers etc. Aspects on the topic of climate change – what is often considered a contradiction in terms – is also addressed. It is all too evident these days that what recent work in climatology has revealed carries profound implications for economic and social policy; it is with these in mind that the final chapters consider acumens as to the application of what has been learned to date. This book is divided into four sections that cover sub-disciplines in climatology. The first section contains four chapters that pertain to synoptic climatology, i.e., the study of weather disturbances including hurricanes, monsoon depressions, synoptic waves, and severe thunderstorms; these weather systems directly impact humanity. The second section on regional climatology has four chapters that describe the climate features within physiographically defined areas. The third section is on climate change which involves both past (paleoclimate) and future climate: The first two chapters cover certain facets of paleoclimate while the third is centered towards the signals (observed or otherwise) of climate change. The fourth and final section broaches the sub-discipline that is often referred to as applied climatology; this represents the important goal of all studies in climatology–one that affects modes of living. Here, three chapters are devoted towards the application of climatological research that might have useful application for operational purposes in industrial, manufacturing, agricultural, technological and environmental affairs. Please click here to explore the components of this work.https://digitalcommons.usu.edu/modern_climatology/1014/thumbnail.jp

Impacts of climate change on fisheries and aquaculture

The 2015 Paris Climate Agreement recognizes the need for effective and progressive responses to the urgent threat of climate change, through mitigation and adaptation measures, while taking into account the particular vulnerabilities of food production systems. The inclusion of adaptation measures in the fisheries and aquaculture sector is currently hampered by a widespread lack of targeted analyses of the sector's vulnerabilities to climate change and associated risks, as well as the opportunities and responses available. This report provides the most up-to-date information on the disaggregated impacts of climate change for marine and inland fisheries, and aquaculture, in the context of poverty alleviation and the differential dependency of countries on fish and fishery resources. The work is based on model projections, data analyses, as well as national, regional and basin-scale expert assessments. The results indicate that climate change will lead to significant changes in the availability and trade of fish products, with potentially important geopolitical and economic consequences, especially for those countries most dependent on the sector