ABSTRACTLand cover changes (LCCs) play an important role in the climate system. Research over recent decades highlights the impacts of these changes on atmospheric temperature, humidity, cloud cover, circulation, and precipitation. These...
moreABSTRACTLand cover changes (LCCs) play an important role in the climate system. Research over recent decades highlights the impacts of these changes on atmospheric temperature, humidity, cloud cover, circulation, and precipitation. These impacts range from the local‐ and regional‐scale to sub‐continental and global‐scale. It has been found that the impacts of regional‐scale LCC in one area may also be manifested in other parts of the world as a climatic teleconnection. In light of these findings, this article provides an overview and synthesis of some of the most notable types of LCC and their impacts on climate. These LCC types include agriculture, deforestation and afforestation, desertification, and urbanization. In addition, this article provides a discussion on challenges to, and future research directions in, assessing the climatic impacts of LCC.
Although the use of mathematical models and quantitative methods in geography accelerated in earnest with the development of quantitative geography and regional science in the late 1950s, such techniques had already made their way into...
moreAlthough the use of mathematical models and quantitative methods in geography accelerated in earnest with the development of quantitative geography and regional science in the late 1950s, such techniques had already made their way into the mainstream of physical geography much earlier. Today, mathematical models and quantitative methods are used in a number of subfields in geography with their proliferation being aided, in part, by the widespread use of remote sensing, geographic information systems (GIS), and computer-based technology. As a consequence, geography as a whole has witnessed a new growth in the development of models and quantitative methods over the last decade, and it is this growth that we seek to elucidate here. Highlighting the advances in the use of models and methods in geography is a difficult undertaking. Such techniques are so widely used in GIS and remote sensing that many developments in these areas also could be considered in this chapter. Moreover, modeling and quantitative techniques are so strongly integrated within some geographic subfields (e.g. climatology and geomorphology, economic and urban geography, regional science) that it is often difficult to separate technique development from application. This is illustrated by the fact that many members of the Association of American Geographers who frequently use and develop quantitative techniques and models are not active participants in the Mathematical Models and Quantitative Methods Specialty Group, choosing instead to favor specialty groups with a more topical, rather than methodological, focus. In a very real sense, the quantitative revolution has been completed in many subfields of geography, with the goals and aims of the revolutionaries having long since passed into the mainstream. Furthermore, geographers who are involved with quantitative methods and mathematical models are extremely diverse in their interests and applications— they contribute to an extremely wide variety of disciplines. While they excel at spreading the geographic word to other disciplines, summarizing their multifarious contributions is nearly impossible. The rather trite statement, “Geography is what geographers do,” seems to apply strongly here. Geographers are largely a collection of individuals who, although united by their interest in spatial models and methods, are unique in the ways that they make contributions to various fields.
Previously published claims of large regional (northern vs southern states) differences in risks of fatality associated with tornadoes in the United States are reexamined. This new study extends earlier claims to include 1) data from a...
morePreviously published claims of large regional (northern vs southern states) differences in risks of fatality associated with tornadoes in the United States are reexamined. This new study extends earlier claims to include 1) data from a much longer time frame, 2) injuries as well as fatalities, and 3) more precise estimates of meteorological features of tornado events (specifically, a precise calculation of daytime vs nighttime and pathlength). The current study also includes formal mediation analyses involving variables that might explain regional differences. Results indicate that significant increases in the risk of fatality and injury do occur in southern states as compared with northern states. Mediation models show that these regional differences remain significant when meteorological factors of nocturnal occurrence and pathlength are included. Thus, these meteorological factors cannot explain regional differences in risk of fatality and injury, a failure that is unlikely to re...
In order to evaluate how much Total Solar Irradiance (TSI) has influenced Northern Hemisphere surface air temperature trends, it is important to have reliable estimates of both quantities. Sixteen different estimates of the changes in TSI...
moreIn order to evaluate how much Total Solar Irradiance (TSI) has influenced Northern Hemisphere surface air temperature trends, it is important to have reliable estimates of both quantities. Sixteen different estimates of the changes in TSI since at least the 19th century were compiled from the literature. Half of these estimates are “low variability” and half are “high variability”. Meanwhile, five largely-independent methods for estimating Northern Hemisphere temperature trends were evaluated using: 1) only rural weather stations; 2) all available stations whether urban or rural (the standard approach); 3) only sea surface temperatures; 4) tree-ring widths as temperature proxies; 5) glacier length records as temperature proxies. The standard estimates which use urban as well as rural stations were somewhat anomalous as they implied a much greater warming in recent decades than the other estimates, suggesting that urbanization bias might still be a problem in current global temperatu...
In the Arctic, gage-based measurements of precipitation contain significant systematic biases. These biases include wind-induced undercatch, wetting losses, and evaporative losses. In addition, trace amounts of precipitation are not...
moreIn the Arctic, gage-based measurements of precipitation contain significant systematic biases. These biases include wind-induced undercatch, wetting losses, and evaporative losses. In addition, trace amounts of precipitation are not routinely counted in daily precipitation totals although they can contribute significantly to precipitation in dry locations in the high latitudes. Thus, gage-based measurements of Arctic precipitation substantially underestimate actual (true) precipitation. Accurate precipitation data from the Arctic are required to realistically simulate runoff from Arctic watersheds and model the global water balance (Serreze et al. 2003). This study addresses the need for accurate Arctic precipitation data by applying the systematic bias adjustments that have been developed from experimental studies (e.g., Sevruk 1982; Groisman et al. 1991; Goodison et al. 1998) to gagemeasured precipitation. Bias adjustments were applied to 9 years of daily data (1994–2002) from nea...
Various environmental factors influence the outbreak and spread of epidemic or even pandemic events which, in turn, may cause feedbacks on the environment. The novel coronavirus disease (COVID-19) was declared a pandemic on 13 March 2020...
moreVarious environmental factors influence the outbreak and spread of epidemic or even pandemic events which, in turn, may cause feedbacks on the environment. The novel coronavirus disease (COVID-19) was declared a pandemic on 13 March 2020 and its rapid onset, spatial extent and complex consequences make it a once-in-a-century global disaster. Most countries responded by social distancing measures and severely diminished economic and other activities. Consequently, by the end of April 2020, the COVID-19 pandemic has led to numerous environmental impacts, both positive such as enhanced air and water quality in urban areas, and negative, such as shoreline pollution due to the disposal of sanitary consumables. This study presents an early overview of the observed and potential impacts of the COVID-19 on the environment. We argue that the effects of COVID-19 are determined mainly by anthropogenic factors which are becoming obvious as human activity diminishes across the planet, and the im...
Observed changes in Northern Hemisphere snow cover from satellite records were compared to those predicted by all available Coupled Model Intercomparison Project Phase 5 (“CMIP5”) climate models over the duration of the satellite’s...
moreObserved changes in Northern Hemisphere snow cover from satellite records were compared to those predicted by all available Coupled Model Intercomparison Project Phase 5 (“CMIP5”) climate models over the duration of the satellite’s records, i.e., 1967–2018. A total of 196 climate model runs were analyzed (taken from 24 climate models). Separate analyses were conducted for the annual averages and for each of the seasons (winter, spring, summer, and autumn/fall). A longer record (1922–2018) for the spring season which combines ground-based measurements with satellite measurements was also compared to the model outputs. The climate models were found to poorly explain the observed trends. While the models suggest snow cover should have steadily decreased for all four seasons, only spring and summer exhibited a long-term decrease, and the pattern of the observed decreases for these seasons was quite different from the modelled predictions. Moreover, the observed trends for autumn and win...
The purpose of this work was to quantify the variation of subcanopy spatiotemporal light dynamics over the course of a year and to link it to the physiological ecology of the understory shrub, Lindera benzoin L. Blume (northern...
moreThe purpose of this work was to quantify the variation of subcanopy spatiotemporal light dynamics over the course of a year and to link it to the physiological ecology of the understory shrub, Lindera benzoin L. Blume (northern spicebush). Covering all seven phenoseasons of a deciduous forest, this work utilized a line quantum sensor to measure the variation in subcanopy light levels under all sky conditions at different times of the day. A total of 4,592 individual subcanopy measurements of photosynthetic photon flux density (PPFD, μmol m-2 s-1) were taken as 15-second spatially-integrated one-meter linear averages to better understand the dynamism of light exposure to L. benzoin. Both open (n = 2, one continuous and one instantaneous) and subcanopy location (n = 25) measurements of PPFD were taken on each sampling date in and near the forested plot (Maryland, USA). In addition, we explored the effect of four photointensity-photoperiod combinations on the growth of L. benzoin under...
Summary Precipitation regionalization techniques alternatively advocated by Johnston [15] and Willmott [30] are reviewed and compared. An implementation by Johnston [15] of the information theory or entropy method was determined to have...
moreSummary Precipitation regionalization techniques alternatively advocated by Johnston [15] and Willmott [30] are reviewed and compared. An implementation by Johnston [15] of the information theory or entropy method was determined to have limited applicability —principally owing to its inability (1) to describe periodicies that are inherent in the seasonal cycle and (2) to account for differences between time-series of precipitation with
This report addresses the potential impact of a doubling of atmospheric carbon dioxide (CO2) concentrations on the precipitation climate of the Southernn Great Plains. Daily precipitation data from 610 National Weather Service first-order...
moreThis report addresses the potential impact of a doubling of atmospheric carbon dioxide (CO2) concentrations on the precipitation climate of the Southernn Great Plains. Daily precipitation data from 610 National Weather Service first-order and cooperative stations were used to quantify mean seasonal precipitation as well as precipitation frequency and intensity. This observed precipitation climatology was then compared to the present-day simulations of precipitation obtained from the Goddard Institute for Space Studies and the Canadian Climate Centre general circulation models to determine each model`s ability to reproduce the observed precipitation climate. Results from the doubled CO2 model simulations were then used to assess the effect of climate change on mean precipitation and precipitation frequency and intensity. Magnitudes of the signal-to-noise ratio (the ratio of climate change to climatic variability) also were estimated.
January and July surface air temperature fields simulated by the GFDL, OSU, GISS, and UKMO general circulation models (GCMs) are compared to the global surface air temperature climatology compiled by Legates and Willmott. Legates and...
moreJanuary and July surface air temperature fields simulated by the GFDL, OSU, GISS, and UKMO general circulation models (GCMs) are compared to the global surface air temperature climatology compiled by Legates and Willmott. Legates and Willmott's climatology was selected as the verification standard because it provides better spatial and temporal coverage than its predecessors, such as the frequently employed RAND
... Unpublished Ph.D. dissertation, Department of Geography, Univer-sity of Oklahoma, Norman, OK. DeLiberty, TL and Legates, DR (2003) Interannual and seasonal variability of modeled soil moisture in Oklahoma. International Journal of...
more... Unpublished Ph.D. dissertation, Department of Geography, Univer-sity of Oklahoma, Norman, OK. DeLiberty, TL and Legates, DR (2003) Interannual and seasonal variability of modeled soil moisture in Oklahoma. International Journal of Climatology, Vol. 23, 1057–1086. ...
... temporal harmonic of the average monthly air temperatures (°C). Amplitude is proportional to the length of the arrow (measured from the center of the scale/dial) while the occurrence of the maxima in time is given by its directions...
more... temporal harmonic of the average monthly air temperatures (°C). Amplitude is proportional to the length of the arrow (measured from the center of the scale/dial) while the occurrence of the maxima in time is given by its directions (edge of the scale/dial) Page 9. DR Legates and ...
Figure 4. (a) Additive term image, (b) First harmonic amplitude image, te) Second harmonic amplitude image, (d) First harmonic phase image, (e) Second harmonic phase image, (f) First harmonic variance image, (g) Second harmonic variance...
moreFigure 4. (a) Additive term image, (b) First harmonic amplitude image, te) Second harmonic amplitude image, (d) First harmonic phase image, (e) Second harmonic phase image, (f) First harmonic variance image, (g) Second harmonic variance image. planted in corn and alfalfa, while ...