Th is report was prepared as an acco un t o f w or k spon so red by an agency o f the U nited Sta... more Th is report was prepared as an acco un t o f w or k spon so red by an agency o f the U nited States Govern me nt. Nei t her the U nited Stat es Go vernment nor any agency thereof, nor any of their employees, m akes an y warranty, express or impl ied, or ass umes any legal lia bility or respo n sibility for the accuracy, co mp leteness, or usefuln ess of any in for mati on , appara tus, p roduct , or process disclosed, or represe nts that its use w o ul d not i nfri nge p riva tely owned rights. Re ference herein to an y sp ecif ic co m m erci al pro duct, pro cess, or service by trade n ame, trademark , man ufactu re r, o r o therwi se, does not ne cessarily con stitute or i m pl y its endorse m ent, reco m men d ation , or favor in g by the U ni ted Sta tes Go ve rn me n t o r any age n cy t hereo f. Th e views and opi nio n s of authors exp ress ed herei n do not necess arily state o r re flect those of the Un ited State s Gove rn me nt o r any agen cy t hereof.
In this paper we describe a field measurement program for the evaluation of plume depletion model... more In this paper we describe a field measurement program for the evaluation of plume depletion models using simultaneously released, depositing and nondepositing tracers. The testing of such models requires at least three kinds of information: a description of the meteorology that governs atmospheric transport and diffusion, an estimate of how rapidly the material of interest deposits to the surface, and a measurement of the airborne concentration distributions that result from the atmospheric diffusion and deposition of this material. The second requirement is particularly troublesome, since estimates of deposition rates vary over several orders of magnitude. Data were obtained from six dual-tracer releases during moderately stable to near-neutral conditions. The behavior of the nondepositing tracer was used to deduce the diffusion meteorology, while both tracers were used to determine C/sub d//C/sub o/, the ratio of the crosswind-integrated, depositing and nondepositing tracer concentrations. The deposition velocity of the depositing tracer was also obtained from the dual-tracer concentrations, using a novel method based on the surface depletion model of Horst (1977). The measured values of C/sub d//C/sub o/, were then compared to the predicted values for each of four Gaussian plume-depletion models.
Abstract : Turbulence characteristics of wind and temperature fields in drainage flows over a sim... more Abstract : Turbulence characteristics of wind and temperature fields in drainage flows over a simple slope were studied. Data was collected on a simple, nearly two-dimensional mountain ridge with little vegetation. Anemometers, thermistors, and thermometers were used to collect mean and turbulent wind and temperature data 150 m below the ridgeline. Evidence for katabatically driven winds was found for a wide range of ambient conditions whenever a surface inversion was formed. When a velocity jet characteristic of good slope flows was present, the vertical profiles of turbulence were found to differ significantly from those over flat terrain, with the turbulent kinetic energy no longer a monotonically decreasing function of height. Richardson number profiles revealed a value well in excess of critical values in the region of the jet. The existence of an internal mixing layer, found by other investigators in deeper drainage flows, was not confirmed. Calculations of turbulent kinetic energy budgets showed a close balance between shear production and viscous dissipation, with buoyancy forces playing a relatively minor role. Above the jet, the contribution from the vertical heat flux was only a few percent of the shear production term and resulted from a near-calculation of the contributions from the heat flux normal to the sloping surface and flux parallel to the surface. In this region, the heat flux parallel to the slope was upslope, resulting in an energy production term, while below the jet it was downslope, resulting in an energy loss. Keywords: Complex terrain.
The treatment of subgrid-scale variations of surface properties and the resultant spatial variati... more The treatment of subgrid-scale variations of surface properties and the resultant spatial variations of sensible and latent heat fluxes has received increasing attention in recent years. Mesoscale numerical simulations of highly idealized conditions, in which strong flux contrasts exist between adjacent surfaces, have shown that under some circumstances the secondary circulations induced by land-use differences can significantly affect the properties of the planetary boundary layer (PBL) and the region of the atmosphere above the PBL. At the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site, the fluxes from different land-surface types are not expected to differ as dramatically as those found in idealized simulations. Although the corresponding effects on the atmosphere should thus be less dramatic, they are still potentially important. From an ARM perspective, in tests of single column models (SCM's) it would be useful to understand the effects of the lower bo...
In this paper we discuss the use of rotating shadowband radiometers and microwave radiometers to ... more In this paper we discuss the use of rotating shadowband radiometers and microwave radiometers to find shortwave cloud optical depth and cloud effective radius at two Arctic sites. These sites are the SHEBA ice camp site (a field study undertaken in 1997 and 1998) and the ARM Barrow (AK) site. Special measures are necessary to process the data from the SHEBA site to account for the harsh environment in which the instruments reside. The analysis shows that, over the summer of 1998, the median cloud optical depth at the SHEBA site is greater than the median cloud optical depth at the Barrow site. The cloud droplet effective radius is less at the SHEBA site than the Barrow site.
A suite of three sonic anemometers, two minisodars, and a laser scintillometer were used at four ... more A suite of three sonic anemometers, two minisodars, and a laser scintillometer were used at four locations in the Atmospheric Boundary Layer Experiments (ABLE) facility during the Cooperative Atmosphere Surface Exchange Study 1999 (CASES99) to study the spatial and temporal evolution of intermittent turbulence during very stable conditions. Two locations were within the main CASES99 site at Leon, KS, separated by roughly 1 km; the remaining sites were about 15 km east (Beaumont) and 20 km south (Smileyburg). Sudden increases from an otherwise quiescent signal of downward heat flux (as measured by sonic anemometers and lasers scintillometer) or temperature structure parameter correlation with vertical velocity (from minisodars) were used to define intermittent turbulence. It was generally found that there was little or no one-to-one correlation among turbulent episodes at Leon, Beaumont, and Smileyburg. Within the Beaumont and Leon sites, there were multiple instances of near-simultaneous bursts as observed with sonic - minisodar and scintillometer - minisodar comparisons separated by 20 - 100 m, perhaps indicating that the spatial extent of nocturnal bursts of turbulence varies from a few meters to greater than 1 km but rarely extends beyond 10 km. There were several well defined events, such as microfronts and/ormore » density currents, that were observed at all four sites, generally with a time delay. During the 30 day experimental period, there were only 6 nights with largely quiescent conditions punctuated by periods of intermittent turbulence; the remaining nights were characterized by nearly continuous significant downward heat fluxes, forced by strong winds aloft. The six nights were characterized by relatively light winds and predominantly northerly wind directions. The overall character of the turbulence in terms of duration, frequency of occurrence, and range of turbulence intensity was similar at all sites. However, there were significant differences between overall turbulence intensities between sites on individual nights.« less
In recent years, the problem of characterizing turbulent fluxes of heat, momentum, and moisture o... more In recent years, the problem of characterizing turbulent fluxes of heat, momentum, and moisture over inhomogeneous surfaces has received increasing attention. This issue is relevant to the performance of general circulation models (GCMs), in which a single grid element can encompass a variety of surface and topographical features. Although considerable progress has been made in describing the energy balance at a surface partially covered by vegetation, less is known about how to treat adjacent regions of sharply contrasting surface characteristics. One difficulty is the scarcity of suitable data sets with which to study the problem, particularly on scales of tens to hundreds of kilometers.
This report was prepared as an account of work sponsored by the Uni ted St ates Governmen t. N ei... more This report was prepared as an account of work sponsored by the Uni ted St ates Governmen t. N either the United States nor the Department of Energy, nor an y of thei r employees. nor any o f their contractors. su bcontractors. or their emp lo yees. makes any w arrant y. express or imp lied. or assumes an y legal liabil ity o r respons ibility for the accuracy. co mpleteness or use fu lness of any in formation , apparatu s, prod u ct or process disclosed. or represents that its use wou ld not in fringe pri vately owned rig hts. The views. opinions and conclusions contained in t his report are those of the contractor and do not necessar ily represent those of the United States Government or t he United States Depart ment of Energy.
The radiation balance in the Arctic is widely understood to be a major control for global climate... more The radiation balance in the Arctic is widely understood to be a major control for global climate, and because of the routine occurrence of clouds, cloudradiative interactions are a prominent part of that balance. Curry et al. cited studies that indicated the cloud fraction in the Arctic is a minimum in winter (4070%) and reaches a maximum of approximately 90% in summer. Parameterizations for the interaction between clouds and radiation are generally given in terms of liquid water path (LWP) and droplet or ice crystal effective radius. We have analyzed three years of radiation and radiatively important cloud properties, such as liquid water path and cloud optical thickness, from Alaskas North Slope to see what role surface interactions may play in establishing cloud radiative characteristics. We have focused on summer (warm) clouds, since at that time liquid water clouds provide the strongest radiative forcing and surface interactions are likely to be most important. In this paper, ...
The magnetization of Ag-Mn alloys containing 100 ppm-4 ppm of Mn has been measured from 0.5 K dow... more The magnetization of Ag-Mn alloys containing 100 ppm-4 ppm of Mn has been measured from 0.5 K down to 10 mK. For the high concentrations, ordering sets in at a temperature proportional to impurity concentration; there is no evidence for a spin-compensated Kondo state.
Journal of Geophysical Research: Atmospheres, 2000
Data collected in a measurement campaign in February and March 1997 showed that the Mexico Basin ... more Data collected in a measurement campaign in February and March 1997 showed that the Mexico Basin (also called the Valley of Mexico), located atop the Mexican plateau, fails to develop the strong nocturnal inversions usually associated with basins and does not exhibit diurnally reversing valley wind systems. Data analyses, two-and three-dimensional numerical simulations with the Regional Atmospheric Modeling System (RAMS), and a Lagrangian particle dispersion model are used to interpret these observations and to examine the effects of topography and regional diurnal circulations on boundary layer evolution over the Mexico Basin and its surroundings during fair weather periods in the winter dry season. We show that the boundary layer evolution in and above the basin is driven primarily by regional diurnal circulations that develop between the air above the Mexican Plateau and the generally cooler surrounding coastal areas. A convective boundary layer (CBL) grows explosively over the plateau in the late morning to reach elevations of 2250 m agl (4500 rn rnsl) by noon, and a strong baroclinic zone forms on the edges of the plateau separating the warm CBL air from its cooler surroundings. In early afternoon the rates of heating and CBL growth are slowed as cool air leaks onto the plateau and into the basin through passes and over low-lying plateau edges. The flow onto the plateau is retarded, however, by the strongly rising branch of a plain-plateau circulation at the plateau edges, especially where mountains or steep slopes are present. An unusually rapid and deep cooling of the air above the plateau begins in late afternoon and early evening when the surface energy budget reverses, the CBL decays, and air accelerates onto the plateau through the baroclinic zone. Flow convergence near the basin floor and the associated rising motions over the basin and plateau produce cooling in 3 hours that is equivalent to half the daytime heating. While the air that converges onto the plateau comes from elevations at and above the plateau, it is air that was modified earlier in the day by a cool, moist coastal inflow carried up the plateau slopes by the plainplateau circulation.
Measurements from the Southern Great Plains Cloud and Radiation Testbed site, which is situated i... more Measurements from the Southern Great Plains Cloud and Radiation Testbed site, which is situated in Oklahoma and Kansas and extends over an area approximately 300 km ϫ 350 km in extent, are combined with results from a three-dimensional mesoscale model to study the sensitivity of boundary layer properties to spatially varying surface sensible and latent heat fluxes. Four cloud parameterization schemes are used to estimate the fractional cloudiness expected over the site on three case study days with settled weather conditions during the summer of 1994. Comparisons between observations and model predictions show good qualitative agreement. Although local responses to varying surface fluxes can be found, the replacement of the spatially varying surface conditions with uniform ones makes little difference in the simulated cloud cover or the vertical profiles of potential temperature and water vapor mixing ratio when these are averaged over the full site. Spatial variations in the ambient meteorology were found to be more important than variations in surface fluxes in determining cloud amount and areas of preferred cloud formation. This conclusion is supported by additional simulations in which both the ambient meteorology and surface conditions are averaged over scales ranging from 6.25 km to 300 km. The results call into question the importance of mesoscale fluxes (i.e., fluxes arising from secondary circulations induced by heating contrasts over different surfaces) in coarse-resolution models such as general circulation models, at least for settled weather conditions similar to those considered in this study.
A short description of the so-called øresund experiment is given. The project studies the atmosph... more A short description of the so-called øresund experiment is given. The project studies the atmospheric dispersion process and modifications in the wind field across the 20-km wide øresund strait between Denmark and Sweden. The meteorological observational network extended over a 80-km wide cross section through the øresund. The dispersion process was investigated by carrying out SF6 tracer experiments. Wind and
Eichinger et al. (1993) discuss the use of a Raman lidar for measurements of water vapor fluxes a... more Eichinger et al. (1993) discuss the use of a Raman lidar for measurements of water vapor fluxes and suggest that the method is superior to the use of standard micrometeorological point sensor measurements. Although the lidar shows considerable promise for some purposes, we believe that their criticisms of point sensors are not warranted; that there are difficulties with their application of dissipation techniques to extract fluxes; and that they misinterpret the existence of plume structures as statistically significant spatial variations of turbulent fluxes.
The article discusses the main features of the urban architecture of Krasnoyarsk, the specifics o... more The article discusses the main features of the urban architecture of Krasnoyarsk, the specifics of public transport and the availability of urban space for residents, the problems of public safety in the city; features of parks and public recreation areas; the peculiarity of urban management and the involvement of citizens in the processes of city management. The study is based on modern approaches to the consideration of the urban environment as a result of the interaction of residents and city government. The article is based on a wide range of sources: modern studies of the urban environment in Russia and abroad, official sites of the administration and city services, statistics, modern studies of the urban environment of Krasnoyarsk conducted by scientists of the Siberian Federal University. The results of the study reveal the transitional state of the urban environment of Krasnoyarsk, its rich potential and indicate the main problems and prospects for further development.
Journal of Geophysical Research: Atmospheres, 2002
We have examined differences in cloud liquid water paths (LWPs) at a coastal (Barrow) and an inla... more We have examined differences in cloud liquid water paths (LWPs) at a coastal (Barrow) and an inland (Atqasuk) location on the North Slope of Alaska using microwave radiometer (MWR) data collected by the U.S. Department of Energy's Atmospheric Radiation Measurement Program for the period June-September 1999. Revised retrieval procedures and a filtering algorithm to eliminate data contaminated by wet windows on the MWRs were employed to extract high-quality data suitable for this study. For clouds with low base heights (<350 m), the LWPs at the coastal site were significantly higher than those at the inland site, but for clouds with higher base heights the differences were small. Air-surface interactions may account for some of the differences. Comparisons were also made between observed LWPs and those simulated with the European Centre for Medium-Range Weather Forecasts model. The model usually successfully captured the occurrence of cloudy periods, but it underpredicted the LWPs by approximately a factor of 2. It was also unsuccessful in reproducing the observed differences in LWPs between Barrow and Atqasuk. Some suggestions on possible improvements in the model are presented.
Th is report was prepared as an acco un t o f w or k spon so red by an agency o f the U nited Sta... more Th is report was prepared as an acco un t o f w or k spon so red by an agency o f the U nited States Govern me nt. Nei t her the U nited Stat es Go vernment nor any agency thereof, nor any of their employees, m akes an y warranty, express or impl ied, or ass umes any legal lia bility or respo n sibility for the accuracy, co mp leteness, or usefuln ess of any in for mati on , appara tus, p roduct , or process disclosed, or represe nts that its use w o ul d not i nfri nge p riva tely owned rights. Re ference herein to an y sp ecif ic co m m erci al pro duct, pro cess, or service by trade n ame, trademark , man ufactu re r, o r o therwi se, does not ne cessarily con stitute or i m pl y its endorse m ent, reco m men d ation , or favor in g by the U ni ted Sta tes Go ve rn me n t o r any age n cy t hereo f. Th e views and opi nio n s of authors exp ress ed herei n do not necess arily state o r re flect those of the Un ited State s Gove rn me nt o r any agen cy t hereof.
In this paper we describe a field measurement program for the evaluation of plume depletion model... more In this paper we describe a field measurement program for the evaluation of plume depletion models using simultaneously released, depositing and nondepositing tracers. The testing of such models requires at least three kinds of information: a description of the meteorology that governs atmospheric transport and diffusion, an estimate of how rapidly the material of interest deposits to the surface, and a measurement of the airborne concentration distributions that result from the atmospheric diffusion and deposition of this material. The second requirement is particularly troublesome, since estimates of deposition rates vary over several orders of magnitude. Data were obtained from six dual-tracer releases during moderately stable to near-neutral conditions. The behavior of the nondepositing tracer was used to deduce the diffusion meteorology, while both tracers were used to determine C/sub d//C/sub o/, the ratio of the crosswind-integrated, depositing and nondepositing tracer concentrations. The deposition velocity of the depositing tracer was also obtained from the dual-tracer concentrations, using a novel method based on the surface depletion model of Horst (1977). The measured values of C/sub d//C/sub o/, were then compared to the predicted values for each of four Gaussian plume-depletion models.
Abstract : Turbulence characteristics of wind and temperature fields in drainage flows over a sim... more Abstract : Turbulence characteristics of wind and temperature fields in drainage flows over a simple slope were studied. Data was collected on a simple, nearly two-dimensional mountain ridge with little vegetation. Anemometers, thermistors, and thermometers were used to collect mean and turbulent wind and temperature data 150 m below the ridgeline. Evidence for katabatically driven winds was found for a wide range of ambient conditions whenever a surface inversion was formed. When a velocity jet characteristic of good slope flows was present, the vertical profiles of turbulence were found to differ significantly from those over flat terrain, with the turbulent kinetic energy no longer a monotonically decreasing function of height. Richardson number profiles revealed a value well in excess of critical values in the region of the jet. The existence of an internal mixing layer, found by other investigators in deeper drainage flows, was not confirmed. Calculations of turbulent kinetic energy budgets showed a close balance between shear production and viscous dissipation, with buoyancy forces playing a relatively minor role. Above the jet, the contribution from the vertical heat flux was only a few percent of the shear production term and resulted from a near-calculation of the contributions from the heat flux normal to the sloping surface and flux parallel to the surface. In this region, the heat flux parallel to the slope was upslope, resulting in an energy production term, while below the jet it was downslope, resulting in an energy loss. Keywords: Complex terrain.
The treatment of subgrid-scale variations of surface properties and the resultant spatial variati... more The treatment of subgrid-scale variations of surface properties and the resultant spatial variations of sensible and latent heat fluxes has received increasing attention in recent years. Mesoscale numerical simulations of highly idealized conditions, in which strong flux contrasts exist between adjacent surfaces, have shown that under some circumstances the secondary circulations induced by land-use differences can significantly affect the properties of the planetary boundary layer (PBL) and the region of the atmosphere above the PBL. At the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site, the fluxes from different land-surface types are not expected to differ as dramatically as those found in idealized simulations. Although the corresponding effects on the atmosphere should thus be less dramatic, they are still potentially important. From an ARM perspective, in tests of single column models (SCM's) it would be useful to understand the effects of the lower bo...
In this paper we discuss the use of rotating shadowband radiometers and microwave radiometers to ... more In this paper we discuss the use of rotating shadowband radiometers and microwave radiometers to find shortwave cloud optical depth and cloud effective radius at two Arctic sites. These sites are the SHEBA ice camp site (a field study undertaken in 1997 and 1998) and the ARM Barrow (AK) site. Special measures are necessary to process the data from the SHEBA site to account for the harsh environment in which the instruments reside. The analysis shows that, over the summer of 1998, the median cloud optical depth at the SHEBA site is greater than the median cloud optical depth at the Barrow site. The cloud droplet effective radius is less at the SHEBA site than the Barrow site.
A suite of three sonic anemometers, two minisodars, and a laser scintillometer were used at four ... more A suite of three sonic anemometers, two minisodars, and a laser scintillometer were used at four locations in the Atmospheric Boundary Layer Experiments (ABLE) facility during the Cooperative Atmosphere Surface Exchange Study 1999 (CASES99) to study the spatial and temporal evolution of intermittent turbulence during very stable conditions. Two locations were within the main CASES99 site at Leon, KS, separated by roughly 1 km; the remaining sites were about 15 km east (Beaumont) and 20 km south (Smileyburg). Sudden increases from an otherwise quiescent signal of downward heat flux (as measured by sonic anemometers and lasers scintillometer) or temperature structure parameter correlation with vertical velocity (from minisodars) were used to define intermittent turbulence. It was generally found that there was little or no one-to-one correlation among turbulent episodes at Leon, Beaumont, and Smileyburg. Within the Beaumont and Leon sites, there were multiple instances of near-simultaneous bursts as observed with sonic - minisodar and scintillometer - minisodar comparisons separated by 20 - 100 m, perhaps indicating that the spatial extent of nocturnal bursts of turbulence varies from a few meters to greater than 1 km but rarely extends beyond 10 km. There were several well defined events, such as microfronts and/ormore » density currents, that were observed at all four sites, generally with a time delay. During the 30 day experimental period, there were only 6 nights with largely quiescent conditions punctuated by periods of intermittent turbulence; the remaining nights were characterized by nearly continuous significant downward heat fluxes, forced by strong winds aloft. The six nights were characterized by relatively light winds and predominantly northerly wind directions. The overall character of the turbulence in terms of duration, frequency of occurrence, and range of turbulence intensity was similar at all sites. However, there were significant differences between overall turbulence intensities between sites on individual nights.« less
In recent years, the problem of characterizing turbulent fluxes of heat, momentum, and moisture o... more In recent years, the problem of characterizing turbulent fluxes of heat, momentum, and moisture over inhomogeneous surfaces has received increasing attention. This issue is relevant to the performance of general circulation models (GCMs), in which a single grid element can encompass a variety of surface and topographical features. Although considerable progress has been made in describing the energy balance at a surface partially covered by vegetation, less is known about how to treat adjacent regions of sharply contrasting surface characteristics. One difficulty is the scarcity of suitable data sets with which to study the problem, particularly on scales of tens to hundreds of kilometers.
This report was prepared as an account of work sponsored by the Uni ted St ates Governmen t. N ei... more This report was prepared as an account of work sponsored by the Uni ted St ates Governmen t. N either the United States nor the Department of Energy, nor an y of thei r employees. nor any o f their contractors. su bcontractors. or their emp lo yees. makes any w arrant y. express or imp lied. or assumes an y legal liabil ity o r respons ibility for the accuracy. co mpleteness or use fu lness of any in formation , apparatu s, prod u ct or process disclosed. or represents that its use wou ld not in fringe pri vately owned rig hts. The views. opinions and conclusions contained in t his report are those of the contractor and do not necessar ily represent those of the United States Government or t he United States Depart ment of Energy.
The radiation balance in the Arctic is widely understood to be a major control for global climate... more The radiation balance in the Arctic is widely understood to be a major control for global climate, and because of the routine occurrence of clouds, cloudradiative interactions are a prominent part of that balance. Curry et al. cited studies that indicated the cloud fraction in the Arctic is a minimum in winter (4070%) and reaches a maximum of approximately 90% in summer. Parameterizations for the interaction between clouds and radiation are generally given in terms of liquid water path (LWP) and droplet or ice crystal effective radius. We have analyzed three years of radiation and radiatively important cloud properties, such as liquid water path and cloud optical thickness, from Alaskas North Slope to see what role surface interactions may play in establishing cloud radiative characteristics. We have focused on summer (warm) clouds, since at that time liquid water clouds provide the strongest radiative forcing and surface interactions are likely to be most important. In this paper, ...
The magnetization of Ag-Mn alloys containing 100 ppm-4 ppm of Mn has been measured from 0.5 K dow... more The magnetization of Ag-Mn alloys containing 100 ppm-4 ppm of Mn has been measured from 0.5 K down to 10 mK. For the high concentrations, ordering sets in at a temperature proportional to impurity concentration; there is no evidence for a spin-compensated Kondo state.
Journal of Geophysical Research: Atmospheres, 2000
Data collected in a measurement campaign in February and March 1997 showed that the Mexico Basin ... more Data collected in a measurement campaign in February and March 1997 showed that the Mexico Basin (also called the Valley of Mexico), located atop the Mexican plateau, fails to develop the strong nocturnal inversions usually associated with basins and does not exhibit diurnally reversing valley wind systems. Data analyses, two-and three-dimensional numerical simulations with the Regional Atmospheric Modeling System (RAMS), and a Lagrangian particle dispersion model are used to interpret these observations and to examine the effects of topography and regional diurnal circulations on boundary layer evolution over the Mexico Basin and its surroundings during fair weather periods in the winter dry season. We show that the boundary layer evolution in and above the basin is driven primarily by regional diurnal circulations that develop between the air above the Mexican Plateau and the generally cooler surrounding coastal areas. A convective boundary layer (CBL) grows explosively over the plateau in the late morning to reach elevations of 2250 m agl (4500 rn rnsl) by noon, and a strong baroclinic zone forms on the edges of the plateau separating the warm CBL air from its cooler surroundings. In early afternoon the rates of heating and CBL growth are slowed as cool air leaks onto the plateau and into the basin through passes and over low-lying plateau edges. The flow onto the plateau is retarded, however, by the strongly rising branch of a plain-plateau circulation at the plateau edges, especially where mountains or steep slopes are present. An unusually rapid and deep cooling of the air above the plateau begins in late afternoon and early evening when the surface energy budget reverses, the CBL decays, and air accelerates onto the plateau through the baroclinic zone. Flow convergence near the basin floor and the associated rising motions over the basin and plateau produce cooling in 3 hours that is equivalent to half the daytime heating. While the air that converges onto the plateau comes from elevations at and above the plateau, it is air that was modified earlier in the day by a cool, moist coastal inflow carried up the plateau slopes by the plainplateau circulation.
Measurements from the Southern Great Plains Cloud and Radiation Testbed site, which is situated i... more Measurements from the Southern Great Plains Cloud and Radiation Testbed site, which is situated in Oklahoma and Kansas and extends over an area approximately 300 km ϫ 350 km in extent, are combined with results from a three-dimensional mesoscale model to study the sensitivity of boundary layer properties to spatially varying surface sensible and latent heat fluxes. Four cloud parameterization schemes are used to estimate the fractional cloudiness expected over the site on three case study days with settled weather conditions during the summer of 1994. Comparisons between observations and model predictions show good qualitative agreement. Although local responses to varying surface fluxes can be found, the replacement of the spatially varying surface conditions with uniform ones makes little difference in the simulated cloud cover or the vertical profiles of potential temperature and water vapor mixing ratio when these are averaged over the full site. Spatial variations in the ambient meteorology were found to be more important than variations in surface fluxes in determining cloud amount and areas of preferred cloud formation. This conclusion is supported by additional simulations in which both the ambient meteorology and surface conditions are averaged over scales ranging from 6.25 km to 300 km. The results call into question the importance of mesoscale fluxes (i.e., fluxes arising from secondary circulations induced by heating contrasts over different surfaces) in coarse-resolution models such as general circulation models, at least for settled weather conditions similar to those considered in this study.
A short description of the so-called øresund experiment is given. The project studies the atmosph... more A short description of the so-called øresund experiment is given. The project studies the atmospheric dispersion process and modifications in the wind field across the 20-km wide øresund strait between Denmark and Sweden. The meteorological observational network extended over a 80-km wide cross section through the øresund. The dispersion process was investigated by carrying out SF6 tracer experiments. Wind and
Eichinger et al. (1993) discuss the use of a Raman lidar for measurements of water vapor fluxes a... more Eichinger et al. (1993) discuss the use of a Raman lidar for measurements of water vapor fluxes and suggest that the method is superior to the use of standard micrometeorological point sensor measurements. Although the lidar shows considerable promise for some purposes, we believe that their criticisms of point sensors are not warranted; that there are difficulties with their application of dissipation techniques to extract fluxes; and that they misinterpret the existence of plume structures as statistically significant spatial variations of turbulent fluxes.
The article discusses the main features of the urban architecture of Krasnoyarsk, the specifics o... more The article discusses the main features of the urban architecture of Krasnoyarsk, the specifics of public transport and the availability of urban space for residents, the problems of public safety in the city; features of parks and public recreation areas; the peculiarity of urban management and the involvement of citizens in the processes of city management. The study is based on modern approaches to the consideration of the urban environment as a result of the interaction of residents and city government. The article is based on a wide range of sources: modern studies of the urban environment in Russia and abroad, official sites of the administration and city services, statistics, modern studies of the urban environment of Krasnoyarsk conducted by scientists of the Siberian Federal University. The results of the study reveal the transitional state of the urban environment of Krasnoyarsk, its rich potential and indicate the main problems and prospects for further development.
Journal of Geophysical Research: Atmospheres, 2002
We have examined differences in cloud liquid water paths (LWPs) at a coastal (Barrow) and an inla... more We have examined differences in cloud liquid water paths (LWPs) at a coastal (Barrow) and an inland (Atqasuk) location on the North Slope of Alaska using microwave radiometer (MWR) data collected by the U.S. Department of Energy's Atmospheric Radiation Measurement Program for the period June-September 1999. Revised retrieval procedures and a filtering algorithm to eliminate data contaminated by wet windows on the MWRs were employed to extract high-quality data suitable for this study. For clouds with low base heights (<350 m), the LWPs at the coastal site were significantly higher than those at the inland site, but for clouds with higher base heights the differences were small. Air-surface interactions may account for some of the differences. Comparisons were also made between observed LWPs and those simulated with the European Centre for Medium-Range Weather Forecasts model. The model usually successfully captured the occurrence of cloudy periods, but it underpredicted the LWPs by approximately a factor of 2. It was also unsuccessful in reproducing the observed differences in LWPs between Barrow and Atqasuk. Some suggestions on possible improvements in the model are presented.
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