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Physical Sciences and Mathematics Commons™

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Oceanography and Atmospheric Sciences and Meteorology

University of Massachusetts Amherst

2011

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

On The Retrieval Of The Beam Transverse Wind Velocity Using Angles Of Arrival From Spatially Separated Light Sources, Shiril Tichkule Jan 2011

On The Retrieval Of The Beam Transverse Wind Velocity Using Angles Of Arrival From Spatially Separated Light Sources, Shiril Tichkule

Masters Theses 1911 - February 2014

For optical propagation through the turbulent atmosphere, the angle of arrival (AOA) cross-correlation function obtained from two spatially separated light sources carries information regarding the transverse wind velocity averaged along the propagation path. Two methods for the retrieval of the beam transverse horizontal wind velocity, v_t, based on the estimation of the time delay to the peak and the slope at zero lag of the AOA cross-correlation function, are presented. Data collected over a two week long experimental campaign conducted at the Boulder Atmospheric Observatory (BAO) site near Erie, CO was analyzed. The RMS difference between 10 s estimates of …

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Climate Change In Central America And Mexico: Regional Climate Model Validation And Climate Change Projections, Ambarish V. Karmalkar, Raymond S. Bradley, Henry F. Diaz Jan 2011

Climate Change In Central America And Mexico: Regional Climate Model Validation And Climate Change Projections, Ambarish V. Karmalkar, Raymond S. Bradley, Henry F. Diaz

Raymond S Bradley

Central America has high biodiversity, it harbors high-value ecosystems and it’s important to provide regional climate change information to assist in adaptation and mitigation work in the region. Here we study climate change projections for Central America and Mexico using a regional climate model. The model evaluation shows its success in simulating spatial and temporal variability of temperature and precipitation and also in capturing regional climate features such as the bimodal annual cycle of precipitation and the Caribbean low-level jet. A variety of climate regimes within the model domain are also better identified in the regional model simulation due to …

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Where Do We Stand On Global Warming?, Raymond S. Bradley Jan 2011

Where Do We Stand On Global Warming?, Raymond S. Bradley

Raymond S Bradley

Global temperatures have risen by ~0.8°C since the end of the 19th century. This increase has not been linear, as there have been periods when temperatures were stable for short periods before rising once again. The reasons for these changes in the rate of temperature rise are related to anthropogenic factors (sulphate aerosol pollution versus greenhouse gas inputs to the atmosphere) as well as to natural factors (volcanic eruptions, solar irradiance variations, El Ni.o/Southern Oscillation [ENSO] fluctuations, etc). Over the last decade or so, temperatures have not risen at the same rate as in previous decades, and this has led …

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Natural Archives, Changing Climates, Raymond S. Bradley Jan 2011

Natural Archives, Changing Climates, Raymond S. Bradley

Raymond S Bradley

Climatic changes have occurred throughout human history, but instrumental measurements do not provide us with a very long perspective on climate variations. In many regions, instrumental records only extend back a century or two. To understand the longer-term variability of the climate system, we rely on natural archives— sediments, ice caps, peat bogs, cave deposits, banded corals and tree rings—in which a record of past changes in climate has been preserved. They are a treasure trove of the climatic and environmental history of the planet and provide information about factors that may have caused the climate to change, such as …

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High-Resolution Paleoclimatology, Raymond S. Bradley Jan 2011

High-Resolution Paleoclimatology, Raymond S. Bradley

Raymond S Bradley

High resolution paleoclimatology involves studies of natural archives as proxies for past climate variations at a temporal scale that is comparable to that of instrumental data. In practice, this generally means annually resolved records, from tree rings, ice cores, banded corals, laminated speleothems and varved sediments. New analytical techniques offer many unexplored avenues of research in high resolution paleoclimatology. However, critical issues involving accuracy of the chronology, reproducibility of the record, frequency response to forcing and other factors, and calibration of the proxies remain. Studies of proxies at high resolution provide opportunities to examine the frequency and magnitude of extreme …

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A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke Jan 2011

A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke

Raymond S Bradley

This study takes a comprehensive approach to characterizing the isolation sequence of Heimerdalsvatnet, a coastal lake in the Lofoten Islands, northern Norway. We use established methods and explore new techniques to assess changes in marine influence. Bathymetric and sub-bottom profiles were acquired to examine basin-wide sedimentation and a 5.8 m sediment core spanning the last 7800 cal yr BP was analyzed. We measured magnetic susceptibility, bulk organic matter properties, molecular biomarkers, diatom assemblages, and elemental profiles acquired by scanning X-ray fluorescence. These characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively …

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