The McGill Paleoclimate Model (MPM) was used to simulate the past and future glacial inceptions. This model of intermediate complexity was first run between 122 and 80 kyr BP (Before Present). After some parameter tuning, the MPM simulated the last glacial inception at 119 kyr BP. The recent addition of a vegetation component in the model led to an improvement of the results, especially for the ice sheet distribution over Eurasia. / The MPM was then run to simulate projections of the climate for the next 100 kyr and possibly the next glacial inception. When forced by a constant atmospheric CO2 concentration, the model predicted three possible evolutions for the ice volume: an imminent glacial inception (low CO2 levels), a glacial inception in 50 kyr (intermediate CO2 levels) or no glacial inception during the next 100 kyr (CO2 levels of 370 ppm and higher). This is mainly due to the exceptional configuration of the future variations of the summer insolation at high northern latitudes. The MPM also responded realistically to rapid CO2 changes. If a global warming episode was included at the beginning of the 100-kyr run, the evolution of the climate was slightly different and the threshold over which no glacial inception occurred was lower (300 ppm).

A ground-based radar refractivity mapping technique is used to measure water vapor near the surface during the International H2O Project in May and June, 2002 (IHOP_2002). Radar-measured refractivity is compared with refractivity estimated from surface station observations during this field experiment. Bias in radar and station refractivity is found to occur often when humidity is high. Possible reasons for this difference between radar and station observations are discussed. Most of the biases were associated either with inaccurate humidity observations by stations or with the small height difference of the two measurements. With confirming this last observation further during these wet ground conditions, radar refractivity shows much better agreement with radiosonde sounding refractivity just above the surface than with station refractivity. / In addition, columnar water vapor is computed using the mixing ratios retrieved from radar and station refractivity and using the observed height of the convective boundary layer from a FM-CW radar. Surface moisture fluxes are computed as a residual of the columnar water vapor and compared with observations from flux-towers, which compute this using the eddy-covariance technique. Although the results show that the radar-based measurements may have some skill over longer time periods, the technique completely fails to reproduce observations over scales smaller than 1 hour.

Wildfires are a major part of the Mackenzie River Basin climate system, and most wildfires within the basin are lightning-caused. Thus, a study has been conducted that identifies the atmospheric circulation patterns associated with extreme lightning events. In addition, events are stratified according to the number of resultant large wildfires to determine why some extreme lightning events induce a large quantity of wildfires within the basin, and why others do not. / Extreme lightning events in the MRB are characterized by a strong, persistent upper-tropospheric ridge dominating the basin until event onset. The triggering mechanism of the majority of extreme lightning events is cyclogenesis in lee of the Rocky and Mackenzie Mountains. A Haines Index analysis has been used to show that lack of lower-tropospheric moisture and ample lower-tropospheric instability in advance of an extreme lightning event increase the probability of several resultant large wildfires. Furthermore, extreme lightning events with several induced large wildfires are characterized by a lack of moisture transport into the MRB from the northeast Pacific Ocean.

Thesis (Ph.D.)--The Ohio State University, 2007. / (UMI)AAI3247957. Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0342. Adviser: David H. Bromwich.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3849. Adviser: Larry Di Girolamo. Includes bibliographical references (leaves 109-116) Available on microfilm from Pro Quest Information and Learning.

To study stratospheric water vapor, a new trajectory model was created. The model is built from first principles specific to stratospheric motion and can run on any gridded dataset, making it more versatile than current solutions. The design of a new model was motivated by measurements of elevated stratospheric water vapor, which in situ isotopic measurements have determined to be tropospheric in origin. A moist stratosphere has substantial feedbacks in the climate system including radiative, chemical, and biological effects. Additionally, elevated stratospheric water vapor is theorized as an important coupling in the historical transition to the Eocene, 56 million years ago, as well as emergence from the Eocene 40 million years ago. This transition mirrors modern climate change, both in surface temperature and carbon dioxide increase. However, the historical transition became much more extreme and settled to a state of warm temperatures from the equator to the poles with little variation in between. The lack of latitudinal gradient in temperature is associated with a moist stratosphere, which provides additional motivation for thoroughly understanding the effects of adding water vapor to the stratosphere in a climatological context. The time evolution of water vapor enhancements from convective injection is analyzed by initializing trajectories over satellite-measured water vapor enhancements. The model runs show water vapor concentrations that remain elevated over the background concentrations for several days and often over a week, which is of the timescale that warrants concern over increased halogen catalyzed ozone loss and the subsequent risk to public health. By analyzing stratospheric winds during the summer months over North America using normalized angular momentum, a pattern of frequent stratospheric anticyclonic activity over North America emerges as a unique feature of the region. This provides a mechanism for the modeled persistent elevated water vapor and validates observations. In a climate like today's with increasing surface radiative forcing, the magnitude and frequency of convective injection may increase, with dramatic consequences on the climate system and human health. / Physics

The historical climate record is analyzed to determine trends and variability to develop possible scenarios for future climates. The study area is the Prescott-Russell United Counties and Stormont, Dundas and Glengarry United Counties of Eastern Ontario. Three data sets were used: the Canadian monthly climate data, the Historical Canadian Database Version 2: Monthly Rehabilitated Precipitation and Homogenized Temperature Data Sets and the Eastern Canada daily dataset. The ten warmest years of the past century occurred at the beginning and at the end of the century. However, the last decade (1990--1998) experienced four of the ten warmest years of the century, including the warmest year on record (1998), which was a full degree warmer than the second warmest (1953). Unlike the warmest year, the ten coldest years occurred in the early part of the century, between 1904--1943. The 1990s, although warm in the mean, had fewer extreme heat waves and fewer cold snaps. There is no clear relation between temperature and precipitation, suggesting that future climates may be wet or dry. From the mid 1960s to the present the growing season has started earlier, and since 1984 has been ending later than the long-term average. (Abstract shortened by UMI.)

This thesis examines the concentrations of persistent organic pollutants (POPs) in air and in selected lakes of the Canadian Rocky Mountains. Water was sampled from seven lakes spanning an elevation of 1430 meters from the Interior Plains to the Western Range of the Canadian Rocky Mountains. Air samples were taken at four of these sites, encompassing an altitudinal gradient of 1205 meters. Air and water samples were used to determine net air-water gas exchange fluxes of six POPs at these four sites. This study revealed that air and water concentrations of several persistent organic pollutants did not change significantly with elevation. However, spring pulses of hexachlorocyclohexanes (HCHs) in the lakes were found to coincide with snowmelt, and concentrations of POPs were highest at Bow Lake during the year with the highest snow pack. It was observed that temperature differences with altitude had little impact on the magnitude and direction of air-water gas exchange, indicating net fluxes of POPs were most sensitive to fluctuations in relative air and water concentrations. Air-water gas exchange was compared with the total lake inventory and with estimated losses by outflow. In general, it was revealed that deposition by air-water gas exchanges was an important source of POPs with lower Henry's law constants, such as alpha and gamma-HCH, and net volatilisation was an important loss for the compounds with higher Henry's law constants, (e.g. hexachlorobenzene (HCB) and dieldrin).

No description available.

In the Canadian High Arctic general patterns of temperature are poorly resolved at the meso-scale. This project addressed this issue in three stages. In the first stage a data set of non-standard weather observations was assembled and quality controlled The data set possessed approximately 58000 observations, including dry-bulb temperature, wind, visibility and cloud cover, from the spring and summer seasons of the years 1974--1993. Up to 10% of the data were unusable due to erroneous station information. The second part of the project consisted of a principal components analysis (PCA) of daily temperature data in the Canadian Arctic Archipelago (CAA). The PCA (1) demonstrated how the timing and extent of synoptic events could be tracked, (2) identified the major regional controls of temperature in the CAA, and (3) showed that the non-standard data exhibited general coherency with regional patterns yet were able to reveal zones of coherency at the meso-scale in temperature patterns. In the third stage of the project a model to estimate surface air temperature at the meso-scale was constructed, It was based on a 1 km resolution digital elevation model of the CAA. The effects on temperature due to site elevation and coastal proximity were selected for parameterization. The change in temperature with elevation was implemented in the model using derived environmental lapse rates. Advection effects were handled using resultant winds combined with air temperature above the ocean. Lapse rates and resultant wind estimates were obtained from upper air ascents. Model results for 14-day runs were compared to observed data. Residuals (n = 385) possessed a mean absolute error of 1.5°C. The model was sensitive to steep surface inversions and to low-level warming. Sensitivity analyses were performed on the model to determine response to alterations in lapse rate calculation, sea surface temperature, and wind field generation. The model was most sensitive to lapse rate calculation. The lowest mean absolute error (0.2) was obtained using a moderate lapse rate calculation, moderate wind field and variable sea-surface temperature.