Cold Air Lake Research Articles

A new personalized environment control system for hospital beds with design optimization by Taguchi-based grey relational analysis

The current ward environments consume excessive energy and fail to meet the personal comfort and health needs of patients. A promising solution is to create a personalized bed micro-environment and then extend the ward set-point temperature range. However, there is currently no suitable bed environment control system. This study proposes a novel bedside integrated system with three perforated panels that supplies conditioned air from different directions and prevents direct airflow towards the patient's head region. The system design was optimized using Taguchi-based grey relational analysis (GRA), with predicted mean vote (PMV), draft risk (DR), and personal exposure effectiveness (PEE) considered as response variables. The design variables included supply air temperature, airflow rate, and supply air angles. Taguchi's L16 (44) orthogonal array was employed for the experimental design. The results demonstrate that a low-velocity cold air lake can form above the bed, with the maximum velocity near the patient's head at only 0.2 m/s. In a 28 °C ward, the PMV, maximum DR, and PEE at the bed micro-environment are 0.13, 14.1 %, and 0.67, respectively. This implies that the proposed bed environment control system has the potential to provide both comfort and health benefits while reducing energy consumption. After optimization, the optimal supply air temperature, airflow rate, angles of top panel and side panels are 22 °C, 25 L/s, 0° and 45°, respectively, with an improvement of 5.8 % in the grey relational grade. This study provides a new solution for creating a comfortable and healthy ward environment in an energy-efficient manner.

Climate Patterns Affecting Cold Season Air Pollution of Ulaanbaatar City, Mongolia

Many studies have been conducted on air pollution in Ulaanbaatar city. However, most have focused on the sources of pollutants and their characteristics and distribution. Although the location of the city subjects it to unavoidable natural conditions where air pollution accumulates during the cold season, nature-based solutions have not yet been considered in the projects implemented to mitigate air pollution levels. Therefore, this study aims to determine the combined influence of geography and atmospheric factors on cold season air pollution. The spatiotemporal variations in the variables were investigated using meteorological observation data from 1991 to 2020 in the different land-use areas. Then, atmospheric stagnation conditions and air pollution potential parameters were estimated from daily radiosonde data. Subsequently, the temporal variations in air pollutants were studied and correlated with estimates of the above parameters. In the Ulaanbaatar depression, the stable cold air lake (colder than −13.5 °C), windless (34–66% of all observations), and poor turbulent mixing conditions were formed under the near-surface temperature inversion layer in the cold season. Moreover, due to the mountain topography, the winds toward the city center from all sides cause polluted air to accumulate in the city center for long periods. Air pollution potential was categorized as very high and high (<4000 m2·s−1), in the city in winter, indicating the worst air quality. Thus, further urban planning policy should consider these nature factors.

Cave ventilation and rainfall signals in dripwater in a monsoonal setting – a monitoring study from NE India

Detailed monitoring of subterranean microclimatic and hydrological conditions can delineate factors influencing speleothem-based climate proxy data and helps in their interpretation. Multi-annual monitoring of water stable isotopes, air temperature, relative humidity, drip rates and PCO2 in surface, soil and cave air gives detailed insight into dripwater isotopes, temperature and ventilation dynamics in Mawmluh Cave, NE India.Water isotopes vary seasonally in response to monsoonal rainfall. Most negative values are observed during late Indian Summer Monsoon (ISM), with a less than one-month lag between ISM rainfall and drip response. Two dry season and two less-well distinguishable wet season dynamic ventilation regimes are identified in Mawmluh Cave. Cave air temperatures higher than surface air result in chimney ventilation during dry season nights. Dry season days show reduced ventilation due to cool cave air relative to surface air and cold-air lake development. Both, high water flow and cooler-than-surface cave air temperatures result in air inflow during wet season nights. Wet season daytime ventilation is governed by river flow, but is prone to stagnation and development of cold air lakes. CO2 monitoring indicates that PCO2 levels vary at diurnal to annual scale. Mawmluh Cave seems to act as CO2 sink during part of the dry season. While very likely, additional data is needed to establish whether wet season cave air CO2 levels rise above atmospheric values. Drip behavior is highly nonlinear, related to effective recharge dynamics, and further complicated by human influence on the epikarst aquifer.

Contrastes térmicos nocturnos e acumulação de ar frio em áreas urbanas do Sul da Península de Lisboa

NOCTURNAL THERMAL PATTERNS AND COLD AIR LAKES IN THE URBAN AREAS OF THE SOUTH OF LISBON PENINSULA - A methodology based on a GIS (Idrisi) is presented in a study in orther to recognise some nocturnal thermal patterns in anticyclonic nights in the south of the Lisbon peninsula. A multiple regression model was used to evaluate which topoclimatic variables are responsible for the thermal variation. The results are presented in table I and figure 5. The areas with high probability of ocurrence of cold air lakes during clear and calm anticyclonic nights were identified. It was estimated that 35% of these suburbs are in the areas where cold air lakes can occur. Night temperatures in the valleys, occupied by urban areas are, on avarage, 1ºC lower than in all the other areas. This leads to an increase of disconfort and cunsumption of energy because these areas have been densely developed and populated in the last decades and the buildings are not usually prepared for cold conditions. Several maps are intended to contribute to the urban planning of Lisbon peninsula.

Drenagem e acumulação de ar frio em noites de arrefecimento radiativo. Um exemplo no vale de Barcarena (Oeiras)

THE COLD AIR DRAINAGE DURING CALM CLEAR NIGHTS: AN EXAMPLE IN HE BARCARENA VALLEY (OEIRAS, PORTUGAL) - The cold air drainage system is a recent climatological field research in Portugal. In the valley of Barcarena, a few kilometres westward from Lisbon, it was possible to detect the intermittent flow of the cold air drainage during two calm clear nights. We came to the conclusion that the cold air lakes are formed in situ by the irradiation process and also by the accumulation of the cold air drained along the valley slopes. The rugosity of the surface and the slow down of the cold air along the slope could be responsible for the oscillations of the cold air lakes thickness

Study of Local Climate in Mountainous District by Airborne MSS Thermal IR data: Development of Cold Air Lakes

A low cost personal computer and image processing S/W were empolyed to derive Digtal Elevation Model(DEM) of tidal flat from multitemporal LANDSAT TM images, and to create three-dimensional(3D) perspective views of the tidel flat on Komso bay in west coasts of Korea. The method for generation of Digital Elevation Model(DEM) in tidal flat was considered by overlapping techniques of multitemporal LANDSAT TM images and interpolations. The boundary maps of tidal flat extracted from multitemporal images with different water high were digitally combined in x, y, z space with tide in formation and used as an inputcontour data to obtain an elevation model by interpolation using spline function. Elevation errors of less than 0.1m were achived using overlapping techniques and a spline interpolation approach, respectively. The derived DEM allows for the generation of a perspective grid and drape on the satellite image values to create a realistic terrain visualization model so that the tidal flat may be viewed from and desired direction. As the result of this study, we obtained elevation model of tidal flats which contribute to characterize of topography and monitoring of morphological evolution of tidal flats. Moreover, the modal generated here can be used for simulation of innudation according to tide and support other studies as a supplementary data set.

Climatological and Geographical Characteristics within Inversion Layers in the Presence of High NO2 Concentration

High concentrations of NO2 may accumulate in the upper regions of the atmospheric inversion layers. In this study, the climatological and geographical characteristics of two cases where a high nighttime NO2 concentration appeared in the inversion layer were studied, one on a slope on the Seto Inland Seacoast and in the Saijo Basin. On the Seto Inland Seacoast, the inversion layer appeared at 160 m a.s.l. There were remarkable differences in the concentration of NO2 and saturation deficit across the boundary of the inversion layer. In Saijo Basin, the inversion layer covered almost the whole basin up to 500 m a.s.l. The cold air lake appearing below 290 m contained an especially high level of humidity and NO2 concentration. In conclusion, it appears that the inversion layer plays a significant role as a cover preventing atmospheric NO2 from diffusing outside the layer. In both cases, it seemed that the water vapor pressure almost reached saturation in the high NO2 concentration zone.

八ヶ岳連峰稲子岳の凹地内における暖候期の冷気湖形成

八ヶ岳連峰稲子岳の凹地内における暖候期の冷気湖形成

ジャガラモガラ風穴・盆地の地形，気象および植生の特徴

An investigation was carried out at the Jagaramogara basin in Tendo, Yamagata from 1996 to 1997. Obtained results are as follows:(1) There are wind caves or holes with changeable wind direction, blowing out cool air from the holes in summer half year of May to October and drawing in cold air in winter half year of November to April at the basin bottoms of Ohjigoku and Shimojigoku in Jagaramogara. The author found that the entrances of wind in summer and exits of wind in winter are the stone holes from the region below the cliff of Amayobari west slope to the region fallen down on upper Murakumonoike, and also found that the same regions mentioned above are the entrance in summer and the exit in winter including with the upper holes of the sloped area at Shimojigoku basin.(2) The hole air temperature was observed 0°C at the end of May, 2 to 3°C with relative humidity of 100% and wind speed of 1.5m/s from July to August, maximum of 5.3°C in the middle ten days of October and minimum of -5.4°C in the last ten days of January. There are ices in the wind cave at least until June. The air temperature of blowing wind from the hole in summer is low based on the conduction heat contacted from the ice to air and by cooling of sublimation, fusion and evaporation heats.(3) Inversion of air temperature frequently appeared at night from autumn to spring and is fairly even at the daytime in summer. Strong cooling continued for a long period by adding to the cold air lake with temperature inversion and to cold air blowing out from the holes of basin bottom under a proper condition.(4) The cold air current being relatively dry and warm is observed and typical wind speed is fairly strong of 2.0 to 2.5m/s. The air current starts to blow from the elevation 760m on Amayobari Mt., slides down on the slope and joins in the basin. The cold air lake is developed by radiation cooling. The thermal belt appeared at the elevation of 560 to 570m.(5) The plant profile indicates the reverse distribution to elevation which the semi-alpine plants of dwarfing with cold-drought resistance are found near the lower part of basin. There are many plant species, but the number of holes were decreased recently.

A Biometeorological Study of the Relationship between the Appearance of a Cold Air Lake and the Decline of Red Pine (Pinus densiflora) Forests in Saijo Basin, Hiroshima

A Biometeorological Study of the Relationship between the Appearance of a Cold Air Lake and the Decline of Red Pine (<I>Pinus densiflora</I>) Forests in Saijo Basin, Hiroshima

冷気流と冷気湖の動的相互作用に関する実測的研究

Field investigations of the dynamic interaction between nocturnal drainage winds and a cold-air lake were conducted in a hilly area near Fukuoka City, Japan. It was found that nocturnal drainage winds can be classified into two types according to where they occur, that is, below or above the surface of the cold-air lake. The nocturnal drainage wind which contributes to the development of the cold-air lake over a basin and flows down into the surface layer of the lake is one type of nocturnal drainage wind (NDW I). This type of flow, in general, has a thickness of more than 1O m, and a speed which oscillates with periods ranging from 30 to 60 minutes, though the cause of the periodicity has yet to be determined. Within the cold-air lake, that is, on the hillside buried in the lake, another type of drainage wind (NDW II) can be found, the thickness of which is less than about 10 m. Winds of this type also oscillate, with periods of 20 to 30 minutes and of about 40 minutes. These periods agree fairly well with those of internal gravity waves induced in the cold-air lake, suggesting that the periodic behavior of the NDW II type is associated with the wave-like movement of cold air in the lake. Although cold air is produced over the entire ground surface, nocturnal drainage winds, which are the flow of cold air down the sloping surfaces, exhibit different characteristics according to whether the slope is located above or beneath the surface of the cold-air lake.

斜面温暖帯に関する実測的研究

A thermal belt or a warm zone on a hillside, developing under calm weather conditions during the night, is one of the well-known local climatic phenomena. Although many models describing its fundamental concept have been constructed, very little observational data exists to support the models directly.The difficulty in studying local climatic phenomena lies mainly in collecting data. In the present study, an infrared radiation thermometer installed on the roof of a high building was used to obtain data for analyzing the air temperature structure in complex terrain. The altitude data set (Digital National Land Information, Japan) also was utilized to examine the dependence of air temperature on topography by applying multiple regression analysis.It is confirmed by observation that a thermal belt on a hillside is produced by nocturnal drainage winds and by a cold-air lake which is formed over the basin by the drainage wind and radiative cooling. The height and intensity of a thermal belt are subject to local and temporal variations due to topographical environments and weather conditions, and can vary from hill to hill, even in situations where they are located face to face. These results show that a thermal belt is a phenomenon produced dynamically by the movement of cold air.

四国地域を対象にした熱画像情報による冬期・放射冷却条件下の気温分布の把握

Using the thermal images offered by the infra-red thermometer and the LANDSAT, the air temperature distribution over mountainous regions were estimated under conditions of nocturnal radiative cooling in the winter season. The thermal image analyses by using an infra-red thermometer and the micrometeological observation were carried out around Zentsuji Kagawa prefecture. At the same time, the thermal image analyses were carried out by using the LANDSAT data. The LANDSAT data were taken on Dec. 7, 1984 and Dec. 5, 1989. The scenes covered the west part of Shikoku, southwest of Japan.The results were summarized as follows:Values of the surface temperature of trees, which were measured by an infra-red thermometer, were almost equal to the air temperature. On the other hand, DN values detected by LANDSAT over forest area were closely related with air temperature observed by AMeDAS. Therfore, it is possible to evaluate instantaneously a spatial distribution of the nocturnal air temperature from thermal image.The LANDSAT detect a surface temperature over Shikoku area only at 21:30. When radiative cooling was dominant, the thermal belt and the cold air lake were already formed on the mountain slopes at 21:30. Therfore, it is possible to estimate the characteristic of nocturnal temperature distribution by using LANDSAT data.It became clear that the temperature distribution estimated by thermal images offered by the infra-red thermometer and the LANDSAT was useful for the evaluation of rational land use for winter crops.

Turbulent dissipation of cold air lake in a basin

Problems of turbulent dissipation of a cold air lake (CAL) and the inversion layer bordering CAL on the upper boundary are presented and studied with the compound model. In wintertime such cold air lakes can persist for days even if rather strong winds are blowing above them. The required conditions for CAL dissipation are removed processes of its formation or maintenance, as well as a sufficiently strong invasion of turbulence in the inversion layer from above down-wards. By this, the inversion layer at first becomes stronger and dissipation is stopped, until the increase of turbulent kinetic energy of the upper flow enables further dissipation. Such turbulent dissipation process is shown by the model for typical conditions and for different initial values of the relevent variables.

A cold air lake formation in a basin ? a simulation with a mesoscale numerical model

Summary A formation of a cold air lake in a basin is studied with a mesometeorological model. A dynamic Boussinesq hydrostatic mesoscale numerical model is developed in a staggered orthogonal grid with a horizontal resolution of 1 km and with a varying vertical grid. The topography is presented in a block shape so that computation levels are horizontal. The mesometeorological model is tested in three idealized topography cases (a valley, a single mountain, a basin) and test results are discussed. In an alpine basin surrounded by mountains and plateaus the air is supposed to be stagnant at the beginning of the night. Due to differences in radiation cooling an inversion layer is formed in the basin and local wind circulation is studied by model simulations.

Heat island of a small city and its influences on the formation of a cold air lake and radiation fog in Xishuangbanna, Tropical China

In Xishuangbanna, Yunnan Province, China, cold air lakes and radiation fog are formed in basins at frequencies of 70–90% of winter days. In January, 1989, mobile observations were carried out in order to clarify the urban effects on these local climatic phenomena. The small city, Jinghong, is located in the northwestern part of the Jinghong basin. The basin bottom has an area of about 76 km2. The city had a population of about 40 000 in 1988. Heat islands with an intensity higher than 1 °C were clearly observed in the city. The formation of radiation fog was also observed simultaneously on the slope located in the northeastern part of the basin. It was found that radiation fog was formed first in an air layer at a height of several tens of meters above the city and then it spread over the whole basin within about one hour. It disappeared from the northwestern part of the basin, where the city is located. The mechanism of the urban effect on radiation fog is discussed.On the other hand, some previous studies have pointed out that the local climate in Xishuangbanna has been changing; it has become drier, sunshine duration has increased, and the number of fog-days and the duration of fog at night have decreased. By comparing the meteorological data in the 1960s, when the population of the city was less than 10 000, and in the 1980s, when it was about 40 000, the effects of urbanization and deforestation on the local climate phenomena, such as cold air lakes and radiation fog, are analyzed.

香川県高瀬盆地周辺における冬季の晴天日の局地気象特性の観測

The local meteorological observation was carried out at Takase Basin and the south west slope of Osa Mountain, Kagawa Prefecture on clear-fine day in winter, Jan. 19-21, 1988.The cold air lake was observed at the bottom of Takase Basin and the thermal belt observed at the slopes of 100-500m of Osa Mountain and 100-200m of Asahi Mountain. The vertical differences of both air and surface temperatures for the typical inversion layer were 6-7°C and about 10°C, respectively, and the thickness of the inversion layer was 80-100m at the basin bottom. In the case of small cold air current, the cooling seemed to be larger, because the air current was easy to stand on the gentle slope. The pan-type distribution of isotherm was recognized at the basin.The change of wind direction and the frequency of weak wind of 1m/s were higher at the basin bottom. The cold air current of 1 to 3m/s was observed at the slope and its wind speed was relatively heigher at the lower region of the slope. The cold air current seemed to blow from the elevation of about 400m. The stronger the wind speed of the air current was, the higher the air temperature was at the foot of the mountain, however, the air temperature seemed to be constant in the case of wind speed over 3m/s.The relative humidity and the appearance frequencies of dew and frost were higher at the basin bottom, but lower at the slope and the foot of the mountain in the case of cold air current. The air was dry and its temperature was high at the observation base of 160m in the blowing period of cold air current. The amounts of dew and frost were few, and the latent heat flux by evapotranspiration was occasionally released from the soil surface even at night. As the cold air current blowing from the thermal belt is the warmer wind at the slope and supplies the sensible heat to the crop at the foot of the mountain, its utility is high as meteorological resources along with the thermal belt.

Heat Budget Analysis of Nocturnal Cooling and Daytime Heating in a Basin

Abstract Nocturnal cooling and daytime heating in a basin were studied on clear and calm days by means of heat budget observations. In the nighttime, drainage flow occurs along the basin sideslope and advects cold air to the boundary layer over the basin bottom (BBL), intensifying the cooling rate of the layer. A nocturnal cold air lake develops in the basin, attaining a depth nearly equal to the topographical depth of the basin. Heat budget analysis of the whole basin surface shows that net radiative flux closely balances with sensible heat flux and ground heat conduction. In the daytime, the BBL is warmed not only by sensible heat flux from the surface of the basin bottom, but also by local subsidence heating. This local subsidence above the basin bottom depresses development of the convective boundary layer until the nocturnal cold air lake vanishes completely. The subsidence velocity increases with time after sunrise. Over the whole basin surface, net radiative flux closely balances with sensible and ...

愛媛県西条市のホウレンソウ栽培地域に吹く局地風アラセの特性解明

In order to make clear the meteorological characteristics of local wind “Arase” in Saijo City, Ehime Prefecture, the observations were carried out in the large spinach cultivation area of 2×4km2 during the winter from 1986 to 1987.(1) In the clear-fine night, the thermal belt and the cold air lake were observed on a slope at the middle zone of the mountain and the low flat ground, respectively. The wind with the direction of S to SW blowing down from the Ishizuchi mountain range to the foot of Takatoge mountain was recognized as the katabatic wind or cold air current, however, the wind blew little at the low flat ground. According to the observations, the local wind “Arase” was concluded as a katabatic wind.The relative humidity was low at the mountain foot and high at the low flat ground. Neither dew nor frost was not observed at the foot, but both were observed at the flat ground. The frost occurred at the northern range of the low flat ground and the dew between the foot and the northern range. On Jan. 29, 1987, 10-min-mean maximum wind speed was 4.8m/s (6.5m/s at 4m height), wind direction SSW, air temperature 5.7°C and relative humidity 41% at the height of 1m at the observation base, on the contrary at the east side point of mobile observation, 0.1m/s, calm, -1.2°C and 77%, respectively. Surface temperature at the 150m height slope and at the low flat ground was 5.8°C and -1.9°C, respectively. The typical katabatic wind seemed to be developed under the conditions of potential temperature difference 5K, elevation difference 1400m and slope length 12km.The katabatic wind at night on a fine day was a warm and dry wind for a spinach crop transferring the sensible heat from the wind, the condensations of dew and frost on a crop being small. Therefore, the mountain foot region of Takatoge was suitable for a spinach cultivation. On the other hand, the frequency of the warm wind blown decreased gradually from the mountain foot to the northern low flat ground, and the air temperature was low due to radiation cooling, particularly significant at the area surrounded with banks. The humidity was high at the area of high groundwater level causing the crop desease and pest. Consequently, this low flat region was not suitable for spinach cultivation resulting in the relatively worse quality and lower quantity.(2) During the clear-fine daytime, the air temperature was generally high at the mountain foot and low at the low flat ground and vice versa for the humidity. The wind was strong at the northern region by sea breeze and monsoon, and weak at the mountain foot, reversely at the nighttime. The northerly wind blew in the case of the circulation of land and sea breeze, but the westerly wind in the case effected by monsoon.(3) At the flat ground, the spatial differences of meteorological phenomena were not only small on a rainy day but also rather small at the daytime on cloudy and fine days. Therefore, the meteorological condition at the nighttime on a fine day had a most important effect on the spinach growth.

Thermal belt and cold air drainage on the mountain slope and cold air lake in the basin at quiet, clear night

This paper reviews results of recent observations on the thermal belt, cold air drainage and cold air lake, which are striking in local climatic phenomena in mountain areas.