Journal of the Meteorological Society of Japan. Ser. II, 1997
Difficulties in using conventional Fourier spectral analysis to explore the temporal variation of... more Difficulties in using conventional Fourier spectral analysis to explore the temporal variation of CO2 short-term fluctuations have indicated the need for some new statistical techniques. It is suggested here that the Multiresolution Fourier Transform (MFT) can be used for interpreting such fluctuations. The technique is adapted from wavelet theory in signal processing. To demonstrate the usefulness of this technique, some examples of analytic fluctuation are first examined. The examples suggest that this technique might be useful for analysis of fluctuations that exhibit locality in both frequency and time. MFT is then applied to study the CO2 fluctuations measured at Alert from 1988 to 1995. The results show that the CO2 concentration over Alert has two dominant regimes of quasi-periodic short-term fluctuation: 1)20-50 day intraseasonal fluctuation and 2) 6-14 day synoptic fluctuation. Both the amplitude and frequency of these fluctuations are strongly modulated by the seasonal cycle and the largest amplitude appears during winter time. In addition, these short-term fluctuations have significant interannual variability, especially for the synoptic fluctuation.
Agent or individual based modelling (IBM) is recognized as an important tool in biological modell... more Agent or individual based modelling (IBM) is recognized as an important tool in biological modelling for simulating animal behaviour and interactions with the environment at the level of the individual while maintaining a collective perspective. The method allows rules to be programmed for the interactions between like and unlike species, responses to geographic factors and impacts from human activities. By emphasizing the development of appropriate rules for the individual, one can avoid imposing ad hoc assumptions concerning the population as a whole and instead allow emergent phenomena to unfold at the larger scale. Here we report on preliminary results using IBM to simulate the movement and population changes of an idealized caribou herd in a Northern Canadian Arctic setting. A wolf population is included in the simulation to study how the predator-prey relations impact the fluctuations in total population. The simulations use GIS data to account for a varying landscape includin...
Monthly and annual component fluxes of the surface radiation and energy budgets for the two-decad... more Monthly and annual component fluxes of the surface radiation and energy budgets for the two-decade period from 1997 to 2016 are compared with the climate normal period (1981–2010) for the marine system consisting of James Bay, Hudson Bay, Hudson Strait and Foxe Basin using estimates from the North American regional reanalysis model. Reflected solar radiation has declined unevenly, primarily offshore of major rivers, in polynyas and along shore leads, both during earlier melt and later freeze up. Annually, net radiation increases are driven by albedo decreases during the summer. Over 94% of the increases in ocean heat gain during the melt season are due to increases in absorbed sunlight. Large enhanced oceanic heat losses in the late fall are almost entirely consumed by intensified convective losses of both sensible and latent heat. All the seas within the Hudson Bay Complex show a reduced rate of ocean warming over the past two decades. This outcome can be partially reconciled with ...
A measure of temperature variability was calculated using annual temperature records obtained fro... more A measure of temperature variability was calculated using annual temperature records obtained from 40 stations in the Canadian Arctic, records beginning between 1929 and 1958, and concluding for this study in 1983. Long-term trends in the frequency of extreme temperature conditions were obtained for eight regions in the Arctic. The results indicate that temperatures in the Canadian Arctic, as a whole, have not become more variable. In the last 15 to 20 years of the period considered in this study, the occurrence of extreme temperature conditions has increased only in three of the eight regions.
Journal of the Meteorological Society of Japan. Ser. II, 1996
A 3-dimensional dynamical regional atmospheric model was used to investigate the quantitative rel... more A 3-dimensional dynamical regional atmospheric model was used to investigate the quantitative relationship between the physical processes of long range CO2 transport from the emission region in Eurasia, characterized by a very strong inversion in the lower troposphere.
Journal of the Meteorological Society of Japan. Ser. II, 1991
Evidence of large temporal and spatial variability in the eddy fluxes of sensible heat in the low... more Evidence of large temporal and spatial variability in the eddy fluxes of sensible heat in the lower troposphere (100-50 kPa layer) in January, from 1946 to 1987, is presented. The January climatological (1946-87) spatial distribution of the meridional standing eddy heat flux is characterized by four main features, or "centers of action" : (1) a region north of Korea (extreme eastern Siberia), (2) northeastern Atlantic Ocean, (3) the Gulf of Alaska, and (4) a region over midwestern Canada. Even though the center just north of Korea is the most intense, much of the interannual variability of the meridional January standing eddy sensible heat transport is associated with the two centers over the northeastern Atlantic and the Gulf of Alaska. Spatial and temporal variability of these centers are correlated with the intensities of the Icelandic Low and the Aleutian Low, respectively. The standing eddy heat transport in the Greenland Sea is well correlated with the ice margin there during years of large abnormal heat transport by the standing eddy component. The long term variability of the heat transport over the period 1946-87 shows a clear interdecadal signal in the Gulf of Alaska. Over the North Atlantic, the variability is instead dominated by a large perturbation in the early 1970's. The January climatological spatial distribution of the meridional transient eddy heat flux is dominated by a center over the Aleutian Peninsula, and an elongated cell stretching from eastern United States to North Sea, with a center off Newfoundland and another over Iceland. The spatial pattern follows closely the climatological tracks of baroclinic disturbances, i. e., synoptic storms. The geographical distribution of the spatial and temporal variability of the January meridional transient eddy heat flux is less organized than the pattern associated with the standing eddy heat flux. Much of the variability is confined to the western hemisphere, from the mid-North Atlantic Ocean, across North America, to the eastern half of the North Pacific. The centers of variability are located at (1) Gulf of Alaska, (2) western and eastern Canada, and (3) southeastern United States.
Micro-scale/small wind turbines, unlike larger utility-scale turbines, produce electricity at a r... more Micro-scale/small wind turbines, unlike larger utility-scale turbines, produce electricity at a rate of 300 W to 10 kW at their rated wind speed and are typically below 30 m in hub-height. These wind turbines have much more flexibility in their costs, maintenance and siting owing to their size and can provided wind energy in areas much less suited for direct supply to the grid system. The small wind industry has been substantially slow to progress in Ontario, Canada, and there is much debate over their viability in a growing energy dependent economy. In an effort to diversify the energy sector in Canada, it is crucial that some preliminary research be conducted in regards to the relevance of changing winds as they impact small wind turbines; this study seeks to demonstrate the performance of two small wind turbines, and speculate on the potential power output and its trend over Ontario historically over the last 33 years using the North American Regional Reanalysis (NARR) data. We a...
Atmospheric modulation of surface heat fluxes at Ocean Weather Station P on a decadal time‐scale
Atmosphere-Ocean, 1993
Abstract A 30‐year record (1951–1980) of surface heat fluxes at Ocean Weather Station P in the no... more Abstract A 30‐year record (1951–1980) of surface heat fluxes at Ocean Weather Station P in the northeastern Pacific Ocean (50°N, 145°W) was examined for differences in the interdecadal variation between fail and winter. During the latter part of the 1950s and the early 1960s, the winter surface heat flux from the ocean to the atmosphere diminished significantly whereas the fall heat flux increased slightly This difference in the modulation of the winter heat flux from the fall heat flux during this period appears to be caused by the presence of an atmospheric circulation anomaly resembling that of the Pacific/North America (PNA) low‐frequency variability mode during the winter season.
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Papers by Kaz Higuchi