Nocturnal Wind Research Articles

Studies on Dew

The present paper deals with the characters of dew under winter-dry climate in southwest region of Taiwan (represented by Pingtung area). The dew amount was measured by means of weighing method with acrylic plate, and the time of dew formation start and dissipation were recorded by an improved Taylor type dew duration recorder. Records were analyzed for quantity and duration of dew and the dew amount were compared with precipitation and class A-pan evaporation. From November 1977 to May 1978 and October 1978 to May 1979, the observed records of dew were summarized as follows:(1) From November to May, the total number of dewy days were 149 in 1977 and 155 in 1978, while in the same periods the total dew amount were 25.9mm in 1977 and 26.2mm in 1978. The monthly average frequency of dewy day was 71%.(2) The maximum dew amount records were 4.2mg cm-2 hr-1, 43mg cm-2 day-1 and 6.57mm cm-2 month-1. The maximum value of duration was 13 hours and the average of that was 8.2 hours.(3) The daily dew amount can be calculated from the following equation with meteorological data, Y=9.3304X1+0.2358X2-0.1348X3+0.4167X4-20.3038, where, Y is the dew amount (mg cm-2 day-1), X1 the nocturnal cooling rate of air temperature in screen (°Chr-1), X2 the nocturnal relative humidity in screen (%), X3 the nocturnal wind speed at 1.5m height (cm s-1) and X4 the total nocturnal net radiation (ly).The proportion of calculated dew amount from regression equation was 79% to observed dew amount.(4) During the rainless month in winter season the dew amount was more than precipitation. The monthly average of dew amount was amount to 7% of precipitation and 4% of pan evaporation in normal year. The daily proportion of dew amount to pan evaporation which more than 10% was about 17% in total dewy days during the winter season.

Studies on Dew

The present paper deals with the characters of dew under winter-dry climate in southwest region of Taiwan (represented by Pingtung area). The dew amount was measured by means of weighing method with acrylic plate, and the time of dew formation start and dissipation were recorded by an improved Taylor type dew duration recorder. Records were analyzed for quantity and duration of dew and the dew amount were compared with precipitation and class A-pan evaporation. From November 1977 to May 1978 and October 1978 to May 1979, the observed records of dew were summarized as follows:(1) From November to May, the total number of dewy days were 149 in 1977 and 155 in 1978, while in the same periods the total dew amount were 25.9mm in 1977 and 26.2mm in 1978. The monthly average frequency of dewy day was 71%.(2) The maximum dew amount records were 4.2mg cm-2 hr-1, 43mg cm-2 day-1 and 6.57mm cm-2 month-1. The maximum value of duration was 13 hours and the average of that was 8.2 hours.(3) The daily dew amount can be calculated from the following equation with meteorological data, Y=9.3304X1+0.2358X2-0.1348X3+0.4167X4-20.3038, where, Y is the dew amount (mg cm-2 day-1), X1 the nocturnal cooling rate of air temperature in screen (°Chr-1), X2 the nocturnal relative humidity in screen (%), X3 the nocturnal wind speed at 1.5m height (cm s-1) and X4 the total nocturnal net radiation (ly).The proportion of calculated dew amount from regression equation was 79% to observed dew amount.(4) During the rainless month in winter season the dew amount was more than precipitation. The monthly average of dew amount was amount to 7% of precipitation and 4% of pan evaporation in normal year. The daily proportion of dew amount to pan evaporation which more than 10% was about 17% in total dewy days during the winter season.

Mesoscale nocturnal jetlike winds within the planetary boundary layer over a flat, open coast

Mesoscale nocturnal jetlike winds have been observed over a flat, open coast. They occur within the planetary boundary layer between 100 and 600 m. At times the wind shear may reach 15 m s-1 per 100 m. Unlike the common low-level jet that occurs most often at the top of the nocturnal inversion and only with a wind from the southerly quadrant, this second kind of jet exists between nocturnal ground-based inversion layers formed by the ‘cool pool’, or mesohigh, and the elevated mesoscale inversion layer over the coast. It occurs mostly when light % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiabgs% MiJkaaiwdacqGHsislcaaI2aGaaeyBaiaabccacaqGZbWaaWbaaSqa% beaacqGHsislcaaIXaaaaOGaaiykaaaa!3FCF!\[( \leqslant 5 - 6{\text{m s}}^{ - 1} )\] geostrophic winds blow from land to sea and when the air temperature over adjacent seas is more than 5 °C warmer than that over the coast. This phenomenon may be explained by combined Venturi and gravity-wind effects existing in a region from just above the area a few kilometres offshore to 100–600 m in height approximately 40–50 km inland because this region is ‘sandwiched’ between the aforementioned two inversion layers.

Conversion of sulfur dioxide to sulfate during the da vinci flights

Simultaneous measurements of atmospheric particulate sulfate and SO 2 were made by tandem filter sampling during manned balloon flights. The balloon permitted measurement of chemical species evolution while following a given air mass. On the June 8, 1976, flight, the balloon encountered a relatively stagnant air mass, remaining above St. Louis County for most of the day before being carried off by nocturnal winds. Concentrations of sulfate and SO 2 remained relatively constant during an eight-hour period. Processes responsible for concentration changes were examined to set bounds upon the oxidation rate of SO 2. The data are consistent with an oxidation rate as low as zero and no greater than 4% h −1.

Interpretation of Meteorological Pollutant Roses in Areas Subject to Nocturnal Drainage Winds

Interpretation of Meteorological Pollutant Roses in Areas Subject to Nocturnal Drainage Winds

Environment of a Costa Rican Forest

Wind speed and turbulence were measured at five heights simultaneously in a Costa Rican forest with non—stalling, heated—thermocouple anemometers. A persistent daytime stable thermal stratification of the air beneath the top canopy decreased small—scale turbulence, which may increase boundary—layer resistance of leaf—to—air transport of water vapor and CO2. Three CO2 source layers (ground level, trunk space, and above the top canopy) and two CO2 sink layers (top canopy and bottom canopy) were found in this forest. Low nocturnal wind speed allowed CO2 from respiration to accumulate at night.

Shelter effect of an old-established shelter block of European larch on a slope of mean gradient 1 in 4

The shelter effect of a larch shelter block situated on a steep slope is examined by a comparison of pre- and post-felling data. Trees gave negligible shelter to a lee slope falling 170 ft. in 700 ft., but they provided effective, if limited, shelter on the same slope when the wind direction was reversed. A lee slope of mean gradient 1 in 4 provided its own shelter and its response to small changes in the direction of downslope surface winds was not effectively reduced by trees planted along the contour. A small steep-slope block increased both the diurnal variation of hourly mean windspeed and the incidence of nocturnal calms at its immediate upslope and downslope margins. The occurrence of maximum hourly windspeed in sunny summer weather was advanced 2 h on a site at 1 h (20 ft.) from the downslope margin of the trees where the ratio of daytime to nocturnal wind speeds under identical surface winds, as recorded at standard height at the agrometeorological station, Fron Goch, was markedly increased above that associated with the position of the same site on the slope after clear-felling. These general influences on wind climate were more clear cut than the direct shelter effect and a windscreen on a steep slope gave effective shelter only against upslope winds, which arose from the protection given over an angular range of 100° or more either side of the direction of the line of greatest slope.

Nocturnal local winds in a drakensberg valley

Abstract The mountain wind in the Bushmans valley of the Drakensberg is shown to have distinctive spatial and temporal characteristics. The onset of the wind occurs as a pronounced surge of cool air. Thereafter surging continues as regular fluctuations in turbulent energy occur throughout the 12- to 15-hour period of the mountain wind. Horizontal velocity spectra show that the maximum contribution to total turbulent energy occurs in surges with periods 1-4 hours. A two-parameter parabolic model best describes the mean mountain wind profile. Departures from this profile may be pronounced during surges. The anti-mountain wind is shown to exhibit a regular parabolic variation of velocity with height on a number of occasions despite the lack of any topographic control at the height of its occurrence. Dissipation of the mountain winds is discussed and a model of nocturnal local winds in the Drakensberg foothills is presented.

Examples of Local Air Circulations Over Cato Ridge During July 1965

Summary Examples are given to illustrate the development of local valley and mountain winds into large-scale regional air movements towards and away from the Drakensberg mountains. Nocturnal winds, blowing from the Natal interior towards the coast, are shown to have distinctive temporal, spatial and thermal characteristics that distinguish them from gradient winds of the same direction and indicate that they are an important feature of the low-level atmospheric circulation over the Eastern Plateau slopes of Southern Africa.

Agricultural Meteorology in India

THE annual report of the Agricultural Meteorology Section, India Meteorological Department, for the year 1939-40 covers the last year during which the section was being financed by the Imperial Council of Agricultural Research, the Government of India having taken over the Section from April 1, 1940. The report describes a number of investigations, most of them concerned with the micro-climatology of crops, that is, with the climates experienced within growing crops, as distinct from the more artificial climate of the ordinary meteorological instrument enclosure which is of greater interest for comparisons between the climates of different countries. A number of new instruments have been developed, including several forms of portable but accurate galvanometer for use with thermocouples of copper and constantan for the measurement of temperature in micro-climatology. The recently completed 35-ft. tower at the Central Agricultural Meteorological Observatory at Poona has been found very useful for mounting thermographs, hygrometers and anemometers, for studies of the variations of temperature, humidity and wind with height, which are important in the control of the vertical exchange of heat and moisture between the soil and the overlying air. At Poona, insolation even in January is found to be so strong that the convective layer, with temperature decreasing with height, does not normally disappear during the night, and is generally still to be observed as a layer one or two feet thick at 6 a.m., when temperature in the lower layers is near its minimum. At that time it is generally coldest at a height of one or two feet, with temperature increasing upwards from that level for several hundred feet, the rise amounting already to about 3° C. on reaching the top of the 35-ft. tower. By April the greater insolation is more than counteracted in its tendency to maintain the convective layer by the effect of a higher average nocturnal wind speed, the net result being that the layer has almost disappeared by 6 a.m. The report includes a number of other studies relating to micro-climatology, among which is a table showing the average wind speed in the afternoon at various heights up to 8 ft. in eight different crops, expressed as a percentage of the wind at the same height above open ground. Up to 2 ft., wheat and sugar cane show the highest degree of sheltering, tobacco and suran the least.