Showing papers in "Atmosphere-ocean in 1986"
TL;DR: In this article, a review of hydrologic processes in the permafrost regions of northern North America is presented, with the focus on the effects of permafrocessing on the water cycle.
Abstract: This paper reviews hydrologic processes in the permafrost regions of northern North America. Much work has recently been done at specific experimental plots to parallel the progress in laboratory investigations, improving our understanding of the heat and water fluxes in thawed and frozen grounds, infiltration in frozen soils, evaporation in a cold environment, interaction between snow and its frozen substrate, and the dynamics of storage in the active layer. Field research on permafrost slopes and in northern research basins adds to our knowledge of permafrost groundwater hydrology, runoff generating processes, river freeze‐up and breakup processes and allows more precise definition of basin water balance. Sufficient hydrometric data are now available to analyse the streamflow characteristics in an area with permafrost, and more work should be done along this line. It is urged that process studies be continued to gain a better understanding of the effect of permafrost upon the hydrologic cycle. ...
212 citations
TL;DR: The literature supporting significant water deposition directly from cloud and fog to the earth's surface is reviewed and previous aircraft and surface measurements of the acidity of this water are summarized as discussed by the authors, and an overview of recent work on forest decline is given and an American (Mountain Cloud Chemistry Project) and Canadian (Chemistry of High Elevation Fog) program to look at the chemical deposition by clouds to high elevation forests, is described.
Abstract: The literature supporting significant water deposition directly from cloud and fog to the earth's surface is reviewed and previous aircraft and surface measurements of the acidity of this water are summarized. An overview of recent work on forest decline is given and an American (Mountain Cloud Chemistry Project) and Canadian (Chemistry of High Elevation Fog) program to look at the chemical deposition by clouds to high elevation forests, is‐described. Preliminary measurements in late 1985 on two mountains in Quebec indicate that fog (cloud on the mountain) water pH values (≈3.8) near the summits (850–970 m) are much lower than precipitation pH values (≈ 4.3) at the same location; the summits are estimated to be in cloud 44% of the year with lower percentages at lower elevations; an estimate of total annual fog water deposition (77 cm) near the summit is similar to the average annual precipitation in Quebec; the estimated fog water hydrogen ion deposition (135 meq m−2) is about three times that fr...
88 citations
TL;DR: In this paper, the linearized non-divergent barotropic vorticity equation in one dimension is used for the study of a problem associated with the specification of lateral boundaries in limited area models.
Abstract: The linearized non‐divergent barotropic vorticity equation in one dimension is used for the study of a problem associated with the specification of lateral boundaries in limited area models This problem presents itself in the form of a “pillow” that builds up near the inflow boundary of the model Linear analysis shows that this pillow can easily be eliminated Linear integrations carried out with a corrector seem to be reasonably accurate Similar integrations with the linearized shallow water equations in one dimension also produce a pillow and the same corrector gives improved results Additional runs are performed in order to show that some commonly used nesting strategies do not control this computational problem in a satisfactory manner It seems that these strategies could be improved with an appropriate corrector
59 citations
TL;DR: In this article, a simple gravity wave drag parametriiation over mountainous terrain is tested for its ability to reduce the systematic errors of medium-range weather forecasts, showing that wave drag is as effective as envelope orography in reducing the systematic error.
Abstract: A simple gravity wave drag parametriiation over mountainous terrain is tested for its ability to reduce the systematic errors of medium‐range weather forecasts. Following Boer et al. (1984), this parametrization is a function of the low‐level wind speed and stability, the local Froude number, and the variance of the subgrid‐scale orographie features. A comparison study of ten 7‐day forecasts obtained with envelope orography, wave drag or standard orography, shows that wave drag is as effective as envelope orography in reducing the systematic errors. A further comparison where the combined effects of the wave drag and that of a complementary enhanced orography (that is one that includes only the subgrid‐scale elements not treated separately by wave drag) are taken into account shows this latter approach to be the most promising in reducing orographically‐related systematic errors.
47 citations
TL;DR: In this article, a two-layer model of internal Kelvin waves propagating around the perimeter of an elongated bay and forced by a spatially uniform wind stress is presented, and the observations support several features of the model response to wind forcing.
Abstract: Analysis of current measurements taken between June and October 1984 at four moorings in Trinity Bay, Newfoundland, is discussed. The alongshore component of current exhibits baroclinic fluctuations coherent with the along‐bay component of wind stress at periods between 3 and 7 days. A two‐layer model of internal Kelvin waves propagating around the perimeter of an elongated bay and forced by a spatially uniform wind stress is presented. The observations support several features of the model response to wind forcing. Along the side of the bay on which Kelvin waves are incoming, the amplitude of the response increases into the bay and decreases with increasing frequency. Along the outgoing side of the bay the amplitude of the response generally shows a maximum at a frequency between 0.2 and 0.3 cpd. The phase lag between current and wind is consistent with a forced response. An example is given of upwelling and downwelling on opposite sides of the bay in agreement with the model behaviour.
26 citations
TL;DR: In this article, the composition, timing and duration of winter lake cover are shown to produce significant spatial and temporal variations in the radiation received at the surface of the water column, and are linked to the timing and rate of oxygen depletion of a temperate lake.
Abstract: The composition, timing and duration of winter lake cover are shown to produce significant spatial and temporal variations in the radiation received at the surface of the water column, and are linked to the timing and rate of oxygen depletion of a temperate lake. In particular, the first snowfall to accumulate on the ice cover reduces radiation input to nearly zero and coincides with the initiation of the linear phase of oxygen depletion. Ablation of the snow cover in spring results in increased radiation receipts and oxygen levels. A simple model shows that the conversion of snow to white ice, which normally occurs during the midwinter period, increases radiation receipts and oxygen levels. Manipulation of the cover by artificially induced slushing is suggested as a management technique in the control of winter oxygen deficits.
26 citations
TL;DR: In this paper, a bonne concordance d'ensemble est observee entre le modele ainsi obtenu et divers resultats theoriques et experimentaux.
Abstract: Resume En se limitant au cas du ciel clair, la luminance energetique de courtes longueurs d'onde en un point du ciel a ete parametrisee empiriquement en fonction de l'angle zenithal du soleil (ou de la masse atmospherique) et du coefficient de turbidite d'Angstrom, apres normalisation par l'eclairement diffus au sol. Dans la zone circumsolaire situee a moins de 3° d'arc du soleil, les mesures experimentales du Lawrence Berkeley Laboratory ont ete utilisees. Il apparait que la luminance normalisee est fortement fonction de la turbidite dans cette zone. Pour le reste du ciel, une autre parametrisation a ete obtenue a partir de differentes series de mesures. La radiance normalisee est alors tres peu fonction de la turbidite. Une bonne concordance d'ensemble est observee entre le modele ainsi obtenu et divers resultats theoriques et experimentaux. Dans le cas d'un angle de diffusion inferieur a 10° environ, le modele manque encore de precision puisqu'il ne prend pas en consideration les proprietes optiques de...
22 citations
TL;DR: In this paper, the authors presented the climatology of the sulphur dioxide column over Thessaloniki derived from three years of observation with the Brewer spectrophotometer.
Abstract: This work presents the climatology of the sulphur dioxide column over Thessaloniki derived from three years of observation with the Brewer spectrophotometer. The SO2 column averages 2.5 m atm‐cm and the shielding of UV‐B by SO2 is investigated and compared with the changes in shielding resulting from an anticipated ozone reduction. Columnar and surface SO2 concentrations over Thessaloniki appear to be typical of those in major industrial‐urban regions of the world. It is concluded that, for urban regions, predictions of changes in UV‐B as a result of man's activities must consider projections of changes in the SO2 column as well as ozone.
21 citations
TL;DR: In this article, a static decision-analytic method is used to investigate the economic value of bivariate seasonal forecasts of the form currently issued by the U.S. National Weather Service.
Abstract: A static decision‐analytic method is used to investigate the economic value of bivariate ‐ precipitation and temperature ‐ seasonal forecasts of the form currently issued by the U.S. National Weather Service. This method is applied to a corn versus spring wheat choice‐of‐crop decision‐making problem by considering a transect of four counties across the northwestern margin of the North American corn belt. Numerical results indicate that seasonal forecasts of current quality can be of appreciable value (≥$1/ha) for some locations when the optimal action chosen on the basis of climatological information is only marginally preferred to another action. Increases in forecast value follow from hypothetical increases in the quality of both the precipitation and temperature components of the forecasts in the spring wheat region, whereas forecast value increases primarily as a function of the quality of the precipitation forecasts alone in the corn belt region. The results are very sensitive to absolute an...
15 citations
TL;DR: Using the sum of latent and sensible heat fluxes and back radiation between the ocean and the atmosphere to express the total heat transfer, Q(T), the annual and interannual variations of QT over the North Pacific were calculated and analyzed as discussed by the authors.
Abstract: Using the sum of latent and sensible heat fluxes and back radiation between the ocean and the atmosphere to express the total heat transfer, Q(T), the annual and interannual variations of QT over the North Pacific were calculated and analysed The total heat transfer is positive (atmosphere gains heat from the ocean) for all seasons and all regions of the North Pacific and there is a close relationship with the main ocean currents The area of maximum heat transfer is the Kuroshio area with an annual variation mainly determined by the Asian monsoon circulation The maximum heat transfer is in January and the minimum, in June Conversely, the maximum total heat transfer to the air over the Gulf of Alaska occurs in October This follows from the interaction of the annual cycle of the oceanic thermal content (which is a maximum in late summer) and the occurrence of stormy conditions in the late fall The QT over the California Current area is about 70% of that over the Kuroshio at the same latitude on the other side of the basin The spectrum of the anomalies from the 30-year mean annual cycle show low frequency variations of period about 5 years in the Kuroshio area and about 2 years in the Alaska and California areas After filtering out the monthly fluctuations, it was found that the Kuroshio area heat transfer was correlated with variations across the central North Pacific to about 170 degrees W The remainder of the basin, including the area of the North Equatorial Current, was correlated with heating variations in both the California and Alaska Current regions
14 citations
TL;DR: In this article, the authors used a simple parametrization of the diffuse sky radiance to improve the estimates of the direct irradiance for slopes not directly facing the equator and found that the difference between measured and estimated irradiances is non-systematic in nature and is therefore reduced through temporal averaging.
Abstract: Irradiance data obtained over a long period at Vancouver and Toronto, Canada, and covering a range of slope orientations are used to validate four models that estimate either the direct or diffuse solar irradiances for inclined surfaces. Evaluations are initially performed for daily and hourly time integrals. A simple parametrization of the diffuse sky radiance dramatically improves estimates of the diffuse irradiance. Both of the direct irradiance models have difficulty accommodating the diurnal characteristics of the irradiance, and consequently modelling errors are substantial for slopes not directly facing the equator. For equator‐facing slopes a saving in data requirements and computational effort through the use of daily integrals can be achieved with little additional error. A substantial portion of the differences between the measured and estimated irradiances is non‐systematic in nature and is therefore reduced through temporal averaging.
TL;DR: In this article, a model that provided a good fit with the oil sightings over a 30-day period following the spill utilizes a vector addition of the residual circulation and 3% of the wind, combined with radially symmetric lateral diffusion determined graphically using rate constants taken from the published literature.
Abstract: The spill of Bunker‐C oil from the tanker Kurdistan into the waters and ice of the Cabot Strait in March 1979, combined with wind and air pressure observations throughout the period, archived oceanographic and meteorological data, and a better than usual oil sighting data base in the weeks following the accident, provided an opportunity to develop and test a relatively simple oil movement and spread model. A model that provided a good fit with the oil sightings over a 30‐day period following the spill utilizes a vector addition of the residual circulation and 3% of the wind, combined with radially symmetric lateral diffusion determined graphically using rate constants taken from the published literature. An error estimate for the modelled movement and spread of the oil is included. Although a small quantity of oil became mixed with the ice moving out of the Gulf of St Lawrence, the bulk remained in open water. Over the 30‐day period following the spill, four wind events were of paramount importan...
TL;DR: In this paper, a vertical automatic profiling system (EVAPS) was deployed for three days in August 1980 to collect continuous vertical temperature and velocity profiles from the water column of Lake Erie.
Abstract: As part of an extensive survey of the temperature and currents of Lake Erie, a vertical automatic profiling system (EVAPS) was deployed for three days in August 1980. This system consisted of acoustic current meters, temperature sensors and a pressure gauge. The buoyant sensor package was winched from the bottom up and down through the water column. The system collected essentially continuous vertical temperature and velocity profiles. From these profiles, the barotropic component of the flow was extracted; it shows the presence of longitudinal seiche and lunar tidal motions and demonstrates favourable agreement with a numerical model. An experimental momentum balance allows the identification of the important terms (Coriolis force, pressure gradient and local acceleration) and the crude estimation of the numerical value of the wind drag coefficient. The baroclinic part of the flow was decomposed into the three lowest order empirically‐computed internal wave modes. The first and second modes coul...
TL;DR: In this paper, the authors investigated the influence of surface fluxes and convective precipitation for two 36-hour periods of cyclogenesis over the northeastern Pacific Ocean and concluded that the CISK mechanism plays an important role in extratropical cyclogenesis.
Abstract: The influences of surface fluxes and convective precipitation are investigated for two 36‐h periods of cyclogenesis over the northeastern Pacific Ocean. Three methods are tested of specifying the fraction of moisture supply that produces convective precipitation in a modified form of Kuo's (1974) parametrization scheme using an 8‐level primitive equations model. When convection is included, precipitation amounts are greater and the cyclone deepening is better predicted than when convection is not included. Predicted cyclogenesis is very sensitive to sea temperature. As the low moves over warmer water, the effect of sensible heating is to increase the moisture convergence in the atmospheric boundary layer. This increases the precipitation rates and accelerates deepening. It is concluded that the CISK mechanism plays an important role in extratropical cyclogenesis.
TL;DR: In this paper, a model for the number density of bubbles near the ocean surface when there is an active production of bubbles by entrainment in a breaking wind-wave field is proposed.
Abstract: A model is proposed for the number density of bubbles near the ocean surface when there is an active production of bubbles by entrainment in a breaking wind‐wave field. It is argued that the total number density is directly proportional to the work done by the atmosphere on the ocean surface to cause the bubbling and inversely proportional to the volume of the largest cavities. A hypothesis that asserts that all possible configurations of bubble energy distributed with bubble size are equiprobable is shown to be equivalent to assuming that the bubble shattering rate is proportional to individual bubble area. The resulting Weibull distribution for bubble number density is shown to fit available data sets adequately. To account for the depth invariance of the observed maximum number density a scale‐dependent but depth‐invariant turbulent diffusivity is proposed.
TL;DR: A comparison of an infrared radiometric technique for measuring cloud cover with standard eye observation and sunshine-derived methods of estimating cloud cover shows the radiometric approach to be a viable alternative to the other two methods as mentioned in this paper.
Abstract: A comparison of an infrared radiometric technique for measuring cloud cover with standard eye observation and sunshine‐derived methods of estimating cloud cover shows the radiometric technique to be a viable alternative to the other two methods The comparison was made between standard weather station records of cloud cover and sunshine duration and radiometer cloud cover over a period of 20 months A strong correlation was found between opacity and radiometer cloud cover, 088 (day) and 083 (night); with a weaker correlation between total cloud amount and radiometer cloud cover, 075 (day) and 078 (night) Advantages of the radiometric technique are stressed with suggestions for future developments relevant to weather observations
TL;DR: In this paper, a model for the production and enrichment of aerosols is presented for scavenging and transport of particles to the surface of a bubble, where the bubble's skin is enveloped into the ejected aerosol, leading to significant enrichment.
Abstract: A model is presented for the production and enrichment of aerosols. Bubbles distributed in size by fragmentation scavenge particles and transport them to the surface. In the collapse process at the surface the bubble's skin is enveloped into the ejected aerosol leading to significant enrichment. For no mass accumulation at the surface in foam the flux due to scavenging equals that for resuspension leading to an estimate of the enrichment. The model results compare favourably with observations of artificial and wind‐generated enrichment if it is assumed that during the scavenging the bubble's clean and mobile surface during the initial stages collects most of its particle load. Further scavenging by the encrusted bubble surface, while significant, is not as dramatic. Other observations of the wind dependency of the process support the model.
TL;DR: In this paper, the ability of a satellite-based model to resolve the mesoscale variability of solar irradiance over the lower Fraser Valley is assessed and the estimated and observed irradiances are found to have a similar spatial coherence.
Abstract: The ability of a satellite‐based model (Gautier et al., 1980) to resolve the mesoscale variability of solar irradiance over the lower Fraser Valley is assessed. The estimated and observed irradiances are found to have a similar spatial coherence. The estimates do not reproduce the anisotropy associated with mountain‐lowland variations in cloudiness. This discrepancy occurs as a result of spatial averaging inherent in the satellite‐based methodology. Large errors of estimate of the hourly solar irradiance induce large errors of optimal interpolation. However, over the long‐term, errors are small and results suggest that differences in interpolated irradiances determined from observed and estimated data may be minor.
TL;DR: In this article, the authors analyzed the radar reflectivity patterns of three large, long-lasting Alberta thunderstorms to determine the precipitation content and the outflow rate as functions of time.
Abstract: Radar reflectivity patterns of three large, long‐lasting Alberta thunderstorms were analysed to determine the precipitation content and the outflow rate as functions of time. These quantities were then used to calculate the rate at which precipitation is generated and the characteristic time of the precipitation process, as functions of time. The maximum hourly‐average precipitation content was approximately 0.5 Tg for one storm (Storm A) and 1 Tgfor each of the other two. The maximum hourly‐average outflow rate was approximately 0.5 Gg s−1 for Storm A and 0.8 Gg s−1 for the others. Each storm had two fairly well defined periods of peak precipitation production lasting about half an hour and separated by about 45 min. The characteristic time, defined as the ratio of the instantaneous precipitation content to the outflow rate, was somewhat longer on the average for one storm than for the other two, but in no case was far from 20 min, which is approximately the time required for rain to develop in ...
TL;DR: In this article, a simple and readily-computed index for diagnostic and numerical weather prediction studies of heat waves and other persistent anomalies has been developed, which takes into account the two important factors of intensity and persistence and it is highly correlated to the surface air temperature on a variety of time-scales.
Abstract: A simple and readily-computed index for diagnostic and numerical weather prediction studies of heat waves and other persistent anomalies has been developed. The index takes into account the two important factors of intensity and persistence and it is highly correlated to the surface air temperature on a variety of time-scales. The utilization of this index for investigating the severe, summer 1980 U.S. heat wave and drought results in an instructive description of the spatial and temporal development of the phenomenon. An assessment of the skill of the Goddard Laboratory for Atmospheres (GLA) model in forecasting the initiation and breakdown of the heat wave in terms of the index is also illustrated.
TL;DR: In this paper, the wind-driven motion of a frictionless object in a rotating reference frame is discussed and a simple energy argument shows that the usual undamped inertial oscillations decay when a more realistic wind stress is used.
Abstract: The wind‐driven motion of a frictionless object in a rotating reference frame is discussed. A simple energy argument shows that the usual undamped inertial oscillations decay when a more realistic wind stress is used. The predicted decay rate depends linearly on wind speed but it is considerably smaller than that found in most oceanic observations. However, there are situations where the mechanism may be a significant source of damping.
TL;DR: An intercomparison of the Vaisala MicroCora system used in the Automated Shipboard Aerological Program (ASAP) and the Atmospheric Environment Service upper air system (GMD/ADRES) was conducted in May-June 1983 as mentioned in this paper.
Abstract: An intercomparison of the Vaisala MicroCora system used in the Automated Shipboard Aerological Program (ASAP) and the Atmospheric Environment Service upper‐air system (GMD/ADRES) was conducted in May‐June 1983. Thirty‐three paired ascents were made. The ASAP system dry‐bulb temperatures averaged 0.3°C warmer. For the lowest 100 mb, the dew‐point temperature difference (ASAP ‐ GMD/ADRES) was near ‐1°C whereas for the 780–500 mb layer, the difference was 1°C. The wind component mean differences averaged were small but with a 4 m s−1 standard deviation.
TL;DR: The first substantial radiative effects of the El Chichon volcanic cloud were observed in Fairbanks in the winter of 1982/83 as discussed by the authors, with the greatest density of the volcanic cloud expected to be around the 20mb level.
Abstract: The first substantial radiative effects of the El Chichon volcanic cloud were observed in Fairbanks in the winter of 1982/83. Winter is the time when stratospheric temperatures can vary widely owing to sudden stratospheric warmings, and interannual variations are large. Mean monthly temperatures of the stratosphere were analysed for the 50‐, 40‐, 30‐, 25‐, 20‐, 15‐, and 10‐mb levels, with the greatest density of the volcanic cloud expected to be around the 20‐mb level. For the four winter months, December 1982 to March 1983, an increase in temperature was observed. This increase was not only observed in Fairbanks, but also for two other stations (McGrath and Anchorage) close by, for which we also analysed the stratospheric temperatures. Further, the interdiurnal variation of temperature (the radiosonde ascents are made at 0200 and 1400 local time) showed marked and significant increases for all three stations. This can be explained by the fact that during daytime the volcanic cloud is warmed by a...