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Net photosynthesis and leaf angle in spring wheat (Triticum aestivum L.). The effect of leaf angle on plot photosynthetic rates was investigated with two genotypes of spring wheat (Triticum aestivum L.) differing in their leaf angle. One genotype was a semidwarf with droopy leaves and the other was a mutant derived from it and characterized by upper leaves at the time of ear emergence. At that time, when the difference in angles between the two varieties was at its most the droopy genotype had higher photosynthetic rates, on clear days around noon. One week or so later the difference was smaller, and on an overcast day the two genotypes differed little, whereas on a clear day and when sun angles were low, the erect variety presented somewhat higher photosynthetic rates., Ledent Jean-François. Photosynthèse nette et angle foliaire chez le froment de printemps (Triticum aestivum L.). In: Bulletin de la Classe des sciences, tome 60, 1974. pp. 961-972.

SUMMARY Measurements were made at eighteen sites within a beechwood on a calm, uniformly overcast day in August, 1971. The sites varied in total incoming radiation (visible plus infra-red), being placed at various points on a light gradient from a clearing to deep canopy shade. Readings of spectral intensity were recorded from 380 nm to 1100 nm both inside and outside the wood. Transmission curves were then plotted for all sites. These showed a relative increase in transmission in the green (550 nm) and far red/near infra-red (beyond 700 nm) wavebands. When normalised, the transmission increment beyond 700 nm was shown to vary between sites, becoming less marked as total incoming radiation increased.

Autumn nocturnal bird migration was investigated using radar and visual observations. Multivariate analyses assessed the influence of environmental variables on orientation. Two categories of birds were distinguished: (1) shorebirds and waterfowl migrating in flocks; and (2) passerine birds flying singly. These two classes of migrants employ different orientation mechanisms. Landbirds selectively flew with the wind, regardless of its direction or speed or whether the skies were clear or overcast. Shorebirds and waterfowl flew in directions independent of wind in light or moderate winds. The accuracy of passerine orientation was not correlated with any of the variables examined. The passerine orientation observed cannot be accounted for by stellar orientation, but is explicable via orientation on the basis of wind direction.

Incoming air from an ocean may either supply heat to a land area or serve as an energy sink. A marked example of the energy sink phenomenon occurs in a coastal valley of California. Advective cooling resulted in much lower evapotranspiration than amounts reported for interior locations during the two months studied, July and September. Evapotranspiration from irrigated ryegrass was equivalent to about 2/3 of net radiation on clear days. This ratio is lower than the 8/10 or 9/10 commonly observed in humid interior areas and is much lower than amounts reported for interior desert conditions. Overcast days having low net radiation did not produce amounts of evapotranspiration that were proportionally as low. This observation indicated that there was a trade off beween radiation and advection under these coastal conditions where a critical balance existed between air and surface temperatures.

Direct observations of the long-wave radiative flux were made over the ocean east of Trinidad using an aircraft mounted radiometer. The response of the radiometer was such that the measurements were running averages of the flux received over 4 miles. The measurements were made at selected levels in the lower troposphere during sky conditions ranging from clear to overcast. From these data values of the means and extremes were selected and the radiative cooling was calculated. A heat budget of the subcloud layer was constructed from which it was determined that the air in this region was warming about 1°C per day. A description of the construction and performance of the radiometer is given in the first part of the paper.

Many model studies using artificial skies have been made in this country and overseas for the prediction of daylight conditions of interiors. Using artificial skies is preferable for model studies to working under the natural sky. The conditions of the natural sky with the specific luminance and luminance pattern can be obtained with the artificial model which has the advantage of remaining stable for long periods of time.R. Kittler has reviewed the development of artificial skies from 1914 to 1957, but most of these are not satisfactory for the advanced studies of the day. J. Longmore and D. C. Croghan have been discussing artificial skies recently constructed in England such as a rectilinear box type by the Building Research Station (1963), a reflecting dome type by Pilkington Brothers Limited (1962), and a transilluminated dome type by the Cambridge University (1962). These are representative of the three types of artificial skies which are currently being used in any country.An artificial sky was constructed at the Building Research Institute in Tokyo in 1966. In designing the new sky the following conditions were satisfied as a as possible.1. The sky surface is adjustable for the luminance distribution of the C. I. E. standard overcast sky.2. It has the average sky luminance of more than 2000 asb (640cd/m2).3. Visually, it gives to observers the appearance of the natural sky.4. A ground surface of known reflection factor can be placed.5. A model room about 0.8m at is width can be used, minimizing the horizon error.6. The working space is large enough to conduct an experiment.7. High temperatures in the working space because of the radiation from lamps should be avoidecd8. The conditions of an experiment can be easily understood by laymen. The new sky belongs to a transilluminated dome type, but the dome is set in a four-cornered room.The size of the room is 7.9m wide and 5.5m deep with a 3.3m ceiling. The sky is represented with the hemispherical F. R. P.(fibre reinforced polyester) plastic dome. The dome consists of six pieces which are joined so as not to reveal the joint. The diameter of the dome is limited to 4.1m because of the limitation of the space, and the dome is fitted with 40 cm tall steel legs. As it is considered that the proper width of a model should be less than 1/5 of the dome diameter, a model which is 0.8 m at is width can be used.All lamps are installed on the ceiling surface. They are one hundred and twenty-two 1.2m, 40W‘white’ fluorescent lamps (4500°K), ten 150W spot type PAR lamps, ten 150W flood type PAR lamps, ten 150W spot type reflector lamps. The electric source is 100V50c/s. The total bare lamp output is 441, 400lm. All these lamps are divided into seven blocks, each being adjusted separately. Fluorescent lamps give direct light mainly to the upper part of the dome while incandescent lamps give indirect light mainly to the lower part by reflection from the wall. The window surface and the exposed side of the dome are coverd with white curtains. In this way the dome can provide the luminance surface which is equivalent to the C. I. E. standard overcast sky, and the average sky luminance reaches more than 2000 asb (640 cd/m2).This sky has the following special advantages.1. As the dome is uniform and the graded luminance distribution and the slight changes of color are seen, this sky bears a close resemblance to the real sky. Therefore using this sky is effective for the subjective appraisal of watching the conditions of the sky through the model window.2. This is made in an ordinary-size square room and consists of a simple set such as the light sources on the ceiling, the reflection walls, and the plastic dome put on the floor. These matters have the advantages of simple design and low cost.

ON the drizzly overcast afternoon of 24 October 1965 approximately 35 small birds landed aboard the U. S. Coast Guard Cutter "Hollyhock" between 1400 and 1800 hours. The ship's position was 76? 20' N, 210 40' W, or some 10 to 20 miles off the northeast coast of Cuba. Among the birds landing on the ship were 27 western Palm Warblers (Dendroica p. palmarum) that were captured and frozen by J. C. Dickinson, Jr. and Neil Payne of the Florida State Museum. These specimens, ultimately given to the author, provided needed data relating to bioenergetics of avian flight, fat deposits, and fat utilization. The geographic position, prevailing winds, and season indicated that the birds were on the verge of completing an extended overwater flight from the north. This appears to be the first unequivocal postflight sample of birds available for detailed fat studies, because samples heretofore reported in the literature as presumed postflight birds contained individuals that might have been aground for some time prior to collection (Odum, 1960; Odum et al., 1964; Kuroda, 1964; Johnston and McFarlane, 1966). Unfortunately, because of the geographic location of the ship sample, it is impossible to state precisely where the overwater flight originated. These birds could have come directly from southern Florida or from any points along the Atlantic seaboard, perhaps via the Bahama Islands. Nonetheless, comparing body weights, fat quantities, and other characteristics of the ship sample with similar data from migrating Palm Warblers collected at Florida television towers during fall migration should help to clarify certain problems relating to flight bioenergetics and fat utilization.

SUMMARY South American leaf blight caused by Dothidella ulei occurs only in tropical America, on both indigenous and cultivated Hevea spp. The conidium (Fusicladium macrosporum) is a 1-septate, dry, air-borne spore about 40 × 7 μ, occurring on the abaxial surface of dry leaves in dense, powdery, olive-green masses, and with one or both cells collapsed. The conidia adhere to the surface of water droplets, becoming turgid, and are disseminated in splash droplets. A Hirst volumetric trap, placed within a prepared source in north-west Trinidad, showed a diurnal periodicity of conidial production, with a maximum at 10.00 h and minima at night or in the early morning. On rainless days there was also a minor peak at 20.00 h. Transient increases occurred after rain, most of which fell around noon. On wet days almost equal numbers of conidia were dispersed between 10.00 and 12.00 h. Large increases occurred in 87% of all rain showers between 09.00 and 13.00 h. After 13.00 h fewer rain showers caused such increases; the lowest (36%) was between 21.00 and 01.00 h. Twice as many were trapped on sunny days (> 9 h sun) at 09.00 h when there was full sunshine, compared with overcast days (< 5 h sun). A more clearly defined morning maximum occurred on relatively windy days, compared with calmer ones. Conidial sporulation became very low, or ceased, where rain fell below a mean of 3–4 mm per day for at least 20 days. Abundant sporulation occurred with a daily rainfall about twice this amount. The results support the belief that if Dothidella ulei appeared in Malaysia its spread would be rapid and its effects damaging.

An evaluation was made of the combined effects on airborne radiation thermometer (Art) readings in the 8–14 μm region of the emissivity of the water whose surface temperature is being measured, the infrared radiation from water vapor and carbon dioxide in the optical path, and the radiation reflected from the surface of the water. The water vapor and carbon dioxide in the optical path beneath the aircraft contributed 10–25% of the measured radiation; gaseous radiation reflected from the water contributed 0.1–0.6%. Radiation emitted from an overcast cloud layer (other than cirrus) and reflected from the water increased the Art reading by 0.5°C. The environmental adjustment reduced the root-mean-square difference between Art readings and a ship bucket thermometer from 1.7 to 0.6°C for 27 cases. A simple rapid graphic method based on the theoretical model was used on 51 cases at different aircraft heights and widely varying meteorologic conditions and produced a similar improvement.

Energy exchange at the surface of an annual sea ice sheet was computed for five days, during the winter of 1959, from values of the following energy components: radiant flux, conducted flux, sensible flux and latent flux. These were obtained by measurement and by application of the theories of Priestley and Crawford. The latter performed well in adverse changing weather conditions, over the stability range of Richardson's numbers between −0·053 and +0·140. The energy components for a relatively cloudless day were compared with those for an overcast day, demonstrating significant changes in the total net radiation at the ice surface due to cloud cover. It was found that open leads forming in the ice release large amounts of energy from the ocean to the atmosphere. This energy is then transmitted to other areas, modifying the weather in those areas. The energy component with the largest uncertainty is the latent flux. All hourly measured values of latent energy were compared with the flux as determined by the remainder method. This comparison was used as an indication of the total energy balance error.

Highest and lowest diurnal air and leaf temperatures in a corn canopy were compared with daily maximum and minimum temperatures in a standard thermometer shelter. Differences in temperature between canopy and shelter were related to general weather parameters. The main parameters governing the canopy-shelter differences in maximum temperature were insolation and time since the last rainfall. On bright, sunny days with low moisture, warmest leaves were 10°F (5.6°C) or more above shelter maxima, while air temperatures in the canopy were as much as 4°–6°F (2.2°–3.3°C) above shelter values. With lower insolation and/or recent rainfall, the differences decreased. Differences in minimum temperature between canopy and shelter were primarily a function of night-time radiation conditions. With atmospheric conditions favorable for radiational cooling, air minima were 2°–3°F (1.1°–1.7°C) below shelter minima, while lowest leaf temperatures were 4°–5°F (2.2°–2.8°C) below shelter values. When atmospheric moisture was high or overcast conditions existed the differences in minimum temperature between canopy and shelter were less. Tabular methods for estimating canopy-shelter temperature differences were developed, based on categories of the estimator parameters.

Radar observations often show nocturnal migrants well oriented under opaque layers of cloud, and perhaps even inside or between cloud layers. Some homing pigeons can orient towards home from unfamiliar territory under overcast skies. In searching for non-visual sensory capabilities of birds it is important to consider not only their sensory physiology but also the atmospheric ecology of migration when neither sky nor ground is visible. Either inertial naviation or orientation to the earth's magnetic field requires considerably greater sensitivity than any yet demostrated in birds. Natural or artificial sounds from the surface, or even ground echoes of flight calls, might facilitate orientation under some conditions. Birds communicating by flight calls might detect the differential wind drift experienced by upper and lower members of a flock, and thus determine the direction of wind shear. Under many meteorological conditions such patterns of air movement as roll vortices or internal gravity waves produce ...

The water relations of the inundated forest of the Rio Negro in the Amazon have been investigated. The sap pressure in trees and bushes standing in several meters of water was found to average between -15 and -20 atm in sunshine. and above -10 in overcast. In rainy weather and at night. the pressure would remain close to ambient. Submerged leaves had ambient or sometimes very slightly positive pressure. Pinnate leaves of legumes folded when the pressure rose above a critical level characteristic of the species. Dehydration curves from full turgor to negative turgor showed 3 characteristic phases: A) a steep decline in pressure when the turgor disappeared; B) a linear decline at zero turgor proportional to the increase in osmotic pressure; and C) a steep decline as negative turgor (intracellular packing) developed. The tensions in the drowned forests were similar to those found in inundated plants of temperate lakes. and hence like many plants in a humid forest. However, in the daytime many flooded plants of the Amazon reached zero turgor without any external sign of wilting.

By means of a network of 14 miniature net radiometers, net radiation was measured above and at two heights within field plots of oats, beans, sunflower and corn. From the measurements, net radiation expenditure within the top and middle layer of the foliage canopies could be evaluated for clear and overcast days. The resulting data indicated that, in accordance with recent theoretical approaches, extinction coefficients within the uppermost canopy layer were not constant with time of day on clear days for the species with an erectophile leaf distribution (corn, oats). This diurnal trend did not occur on days with mainly diffuse radiation or at a greater depth within the canopy where net radiation is also more omnidirectional. Net radiation extinction with depth into the canopy was found to deviate from Beer's law. The vertical distribution of net radiation within a corn crop was approximated very closely by an equation of the following form: $$(Rn)_z /(Rn)_h = e^{ - K_1 L + K_2 L^2 } $$ where (Rn) z /(Rn) h is the fraction of net radiation at the top (h) of the canopy transmitted at a given levelz,K1 andK2 are extinction coefficient constants andL is the downward cumulative leaf area index.

both during the day and at night. The cues guiding these flights of passing waterfowl have been the subject of considerable speculation and discussion in recent years. Hochbaum (1955) has clearly shown that the topographic configuration of the surface of the earth channels the flights of waterfowl, at least in certain areas. These observations in themselves do not, however, give evidence that features of the terrain establish the basic course of flight but only that passing birds respond to topography. The possibility that topographic configuration plays a secondary role was recognized long before we had any conclusive evidence that celestial orientation among birds was a reality. Lucanus (1922) stated this possibility, and Schenk (1924) suggested that some means of maintaining a fixed flight direction was "primary," whereas responses to visible terrestrial landmarks might be "secondary." Recently Bellrose (1958b) reported that Mallards (Anas platyrhynchos) and other species of waterfowl (Bellrose, in press) captured along waterways of central Illinois and released in open fields nearby take a predictable course away from the point of release. For the Mallard the course is northerly. Using small lights attached to the legs of Mallards, Bellrose was able to establish that this response was directionally the same at night as during the day. The response persists unchanged in the period of normal spring and fall migration. This northerly trend is only manifest under clear skies, either during the day or at night. Under overcast skies, flights scattered. It seems implicit that celestial cues are involved in the orientation process. These findings for waterfowl are in general agreement with a considerable body of experimental evidence for various other species of birds. Under experimental conditions that test spontaneous migratory orientation, and for birds in free flight returning to a familiar area, the correlation persists, that is, oriented behavior is observed under clear skies, whereas disoriented behavior occurs when skies are completely overcast. For spontaneous migratory activity during the day this correlation has been established for the Starling, Sturnus vulgaris (Kramer, 1952), and at night for three species of European garden warblers, Sylvia atricapilla, S. borin, S. communis (Sauer, 1957) the Whitecrowned Sparrow, Zonotrichia leucophrys (Mewaldt and Rose, 1960), and the Bobolink, Dolichonyx oryzivorus (personal observation). The Starling can respond differentially on the basis of the sun's position or to an area of sky of something under 450 on either side of it. Direct visibility of the sun itself is apparently not necessary (Kramer, op. cit.). For birds in free flight, homeward orientation during the day under clear skies has been established for the homing pigeon, Columba livia (Kramer, 1952; Matthews, 1953a), and Manx Shearwater, Procellaria pufinus (Matthews, 1953b). Other species seem to respond in a manner similar to that reported by Bellrose (1958b), that is, they take a fixed course under clear skies. Under clear daytime skies this response is made

Radiation balance components have been measured over field polts of oats, beans, sunflower and corn. Daytime variations of incoming short-wave radiation, net radiation, net long-wave radiation and the reflection coefficient are discussed. Linear regression equations relating measurements of hourly averages of net radiation on incoming short-wave radiation and net short-wave radiation, for each crop and for all crops grouped in cloudless and in overcast days, were highly significant:r 2>0.98. Daily totals of net radiation, reflected short-wave radiation and net long-wave radiation, as a percentage of incoming short-wave radiation, were nearly the same for each crop as well for cloudy as for cloudless days. About 25% of the daily total of incoming short-wave radiation was reflected, 18% was lost as long-wave radiation and net radiation amounted to 58%. The diurnal variation of the reflection coefficient was very important on cloudless days. There was an almost linear increase of the reflection coefficient with decreasing solar elevation. Calculations of a heating coefficient on cloudless days gave values around 0.25.

The degree of organization and the size of the cloud patterns in TIROS pictures of tropical disturbances are good indicators of the maximum wind speed as observed by airplanes. The organization varies from unorganized bright cloud patterns, to highly organized spiral arrays of clouds with additional characteristic features, such as the sharp edge of cirrus clouds. Poorly organized clouds are associated with weak disturbances, the most highly organized ones with intense storms. In addition, within each category a relationship exists between the size of the cloud pattern and the maximum wind speed. Both the organization category and the size of the overcast cloud pattern are related statistically to the maximum wind speed, so that the maximum wind speed can be estimated from the picture of the storm alone. Tests with independent data show that a useful relationship has been obtained. Theoretical justification for the results obtained is necessary but is not yet available.

does not appear. First page follows. Introduction The failure of tomatoes to set fruit on the early flower clusters is a common complaint of California growers who produce for the spring and summer market. Poor fruit-set is usually ascribed to low temperatures. (Went (1944)) has suggested that night temperatures in particular have an important influence on fruit-set. In each spring-market area, after the danger of winter frost, there follows a period of 6 weeks to 3 months when day temperatures are conducive to good vegetative growth, but night temperatures may drop too low for proper setting. The cool period in the Imperial and Coachella valleys occurs in late February and early March, but by late March night temperatures usually are satisfactory. In the Tulare district, night temperatures may run too low during early and mid-April, but normally no trouble in setting is experienced after May first. In the coastal districts, which are influenced by cool breezes from the ocean, low night temperatures may occur well into June; in the San Francisco Bay district they occur even into July. In each district the earliest fruit generally brings the best market price. Failure of the early clusters to set fruit may mean a delayed harvest period; even, perhaps, a short one because of competition from districts which produce for a later market. Fruit-set for the canning crop is satisfactory in most years. Early production is less important. Only in the San Francisco Bay district do growers frequently complain of poor fruit-set of this crop. In the northern United States, where fruit-set on greenhouse tomatoes is poor during the short overcast days of winter, growth-regulating substances have proved effective for increasing yields. In California, where no commercial field tests had been reported, experiments were begun in 1945 to determine if growth substances would increase fruit-set under field conditions.

Judging by the personal reports received by the author from lighthouse keepers in various parts of Japan, the following may be suggested as possible behaviour of night migrants, particularly the Passrines. 1) The passage of night migrants is noticed offshore rather than ashore where there are islands and capes to avoid, and they fly low close to the seasurface. 2) As generally said, they migrate in clear nights, but when the sky suddenly became overcast or rainy, they may be lost and if a lighthouse were close enough its dim light may attract them. In such cases, some of them die struck at the lighthouse and others spend the night nearby to start again in the next favourable evening. In clear night this never happens. 3) The second case of migrant destruction at lighthouses occurs when the weather was good during the day and became cloudy or rainy towards evening. On such a day, migrants gathering around lihthouse at a cape where there are usually good cover for rest, become restless to start for night flight, but the sudden overcast condition urges them only to fly around the light and some or numbers of them will strike at it. 4) Stronger the light the more migrants are attracted from greater distances and the lighthouse at more unstable weather condition is responsible for more migrant victims. 5) In recent years, however, the birds struck at lighthouses has become extrmely fewer, owing possibly to: a) the genereal decrease of bird numbers and b) increase of coastal village lights and lights of fishing boats on the coastal seasurface.

Some of the TIROS satellites measured several bands of radiation from which characteristics of the atmosphere can be inferred. In this study, the 8–12μ band of window radiation data from TIROS II, III and IV were used in raw and modified form. The data were segregated into four groups, representing measurement of surface temperatures on land and sea by day and night. A three-day period (10–12 February 1962), when a “Shanghai low” predominated over Korea and Japan, was chosen for the detailed discussion. Results were tested for the United States in summer and applied to estimations of cloud top temperatures, cloud top heights, and vertical motion in overcast areas, and inversion top temperatures in areas of clear skies. Analysis of the modified data indicated good correlation with sky conditions, 700-mb vertical motion, and 500-mb vorticity advection. The resolution of the radiometer was investigated for cloudy areas. Satellite radiation data can provide an additional source of valuable synoptic i...

Three simple and typical cases of radiation fluxes measured by the TIROS III meteorological satellite are presented and discussed. These cases deal with emitted earth radiation received in three infrared channels and reflected solar radiation received in two visible channels over the tropical Atlantic, the eastern United States, and the North African desert. Each of the measurements is accompanied by results from a wide-field radiometer and photographs from TV cameras flown in the same satellite. The cases over the Atlantic Ocean and the African desert were in almost cloudless sides, while the case over the United States included regions ranging from heavily clouded to clear. Results show that the measurements from the various instruments and in the various channels are internally consistent. Maximum albedo values over the overcast arms were determined to be approximately 55 per cent. Over the ocean, albedos were near 7 per cent, and over land and clear skies the albedo varied from about 15 per c...

1. The River Severn is 320 km long from its source to the sea. It is warmed in its lower-middle reaches by the cooling-water from Ironbridge \ldA\rd power station. 2. Hourly records of natural river temperature have been collected for 20 years. Temperatures in the river 2 km downstream of the cooling water outfalls were measured using a continuous recorder in 1966. Surveys showed that complete mixing of warm and cold water occurred at the recorder. 3. The Severn at Ironbridge is fairly swift, and shallow, turbulent rapids (A, C and E on Fig. 1) alternate with slower, deeper reaches. Current velocities varied from 0.5 to 0.8 m/sec. Daily flow rates during the period from January 1965 \2- June 1967 varied from 5.6 cu m/sec. to 480 cu m/sec. The power station normally circulated between 5% and 50% of the available river flow. 4. Records of natural temperature from January 1965 \2- June 1967 are analysed with respect to seasonal and short-term changes in weather conditions. Data obtained from the recorder are used to compute an equation from which \lddownstream\rd temperatures were calculated for periods when the recorder was not in use. 5. Four natural \ldseasons\rd are described covering periods of \ldlow\rd, \ldrising\rd, \ldhigh\rd and \ldfalling\rd temperatures. The rate of change varied from year to year but a mean weekly temperature of 10\dgC was reached in the same week (week 18) in 1965, 66 and 67. Lowest water temperatures were recorded in December and January, the highest in June, July or August. Winter temperatures varied from 0\dg to 8\dg with a mean around 4\dgC. Highest temperature over ten years was 22.8\dgC in 1957, 59 and 60, but the maximum during 1965\2-67 was 20.6\dg in 1965. 6. Mean air and water temperature move generally in the same direction, but in summer water temperature is consistently the higher. 7. Daily records show that there is a regular diurnal variation in water temperature on sunny days in early summer, probably due to the direct warming influence of the sun. No variation occurs in winter. The largest single daily increase was 2.5\dgC, though summer rainfall caused a fall in temperature of 3.5\dgC. This was due to a direct localized cooling effect of the rain. Steady river temperatures were associated with overcast skies and mean air temperatures close to that of the water. 8. Water temperature followed the trends of air temperature during the equinoxes, with some time lag. Other weather conditions during spring and autumn were similar. 9. The effect of a short summer spate was to depress the normal diurnal variation without causing a sharp change in river temperature. 10. Compared with small streams and a Lake District tarn, the temperature of the Severn is relatively stable, with less weekly and diurnal variation. Of the three types of water body, the tarn was generally warmer in summer and cooler in winter. Of the running waters the Severn was slightly warmer in summer and cooler in winter. Maximum stream temperatures were almost always lower than 20\dgC. 11. The short term effects of the cooling water on the river were to exaggerate normal summer diurnal variation by up to 100% and to establish diurnal patterns in other seasons when these were not found naturally. The greatest daily rise 2 km downstream of the station was 7.2\dgC above ambient. More normally the daily increase was 0.5\dgC to 3.5\dgC above ambient. Maximum downstream temperature was 24.5\dgC in the summer of 1965. 12. Long term effects were to produce certain river temperatures, e.g., 10\dgC for short periods some weeks before they occurred naturally, though during the night downstream temperatures fell to ambient. If degree-hours above 0\dgC were totalled over the year there were increases in the downstream reaches of some 29% in 1965 and 11% in 1966. Arbitrary total numbers of degree hours could be reached some 2\2-5 weeks earlier downstream than upstream. The rate of accumulation of degree hours varied with season and the effects of the cooling water on this \ldrate\rd were more marked in winter than in summer. 13. The stability of the natural water temperature in the River Severn compared with that of Hodson's Tarn and small streams, means that single daily measurements or weekly maximum and minimum recordings can be of considerable value in determining temperature patterns.

(1) In the rainy season (from June 15th to the end of September) the Weather Was less settled and there were thunder storms and heavy showers of rain. There was a considerable disturbance in the sea and the water was mixed over great depths during this period. In the remaining part of the year the winds were lighter and the mixing of water less pronounced. The sky was overcast with clouds for the most part of the. rainy season and there was a bright sun light from October to the end of May 1945. (2) The temperature of Water varied between 24° C. and 32.5° C. The maximum temperature of air was recorded as 103.1° F. on 24th March, 1945. (3) The salinity was low in the rainy season.—23.56‰ on 17th July, 1944 and high in the summer—38.4‰ on 21st May, 1945. (4) The range of Hydrogen-ion concentration was 7.8 to 8.35. (5) Phosphates were found in quantities varying between 13.04mg./m3 and 37.8mg./m3. It was as high as 51.9mg./m3 in one sample. (6) The amount of dissolved silica was greater than any other chemical constituents recorded here. The lowest value was 315mg./m3 and the highest 1953mg./m3. (7) The minimum and maximum quantities for nitrite were 4.60mg./m3 and 167.1 mg./m3 and for ammonia 9.84mg./m3 and 156.3 mg./m3 respectively.

Studies in the region of Baie Comeau, Quebec, from 1954 to 1956, showed that black flies were most active in the morning 1 to 2 hours after dawn and in the evening [Formula: see text] to 1 hour before sunset. Flight activity appeared to depend on light intensity if the temperature was not below 45° F, the wind velocity not above 2 m.p.h., and the relative humidity not below 50%. In the morning, activity was greatest at higher levels of light intensity, i.e., 20 ft-c, than in the evening, 5 ft-c. Activity increased before thunderstorms and rain and the increase appeared related more to the change in light intensity than to changes in atmospheric pressure or humidity. At night, black flies moved to resting places in the tops of the trees, probably because of the more suitable light intensity at the higher levels just before dark. Oviposition commenced in the late afternoon and continued until dark except on overcast days, when it commenced in early afternoon. Simulium (Simulium) venustum Say bit man mainly on the back of the neck.

An analysis is presented of possible changes in the radiative terms of the Polar Ocean energy budget. Theoretical polar atmospheres are discussed with various changes in the radiation balance. It is concluded that the atmosphere is, at present, adjusted in the best possible way for the conservation of energy. Radiation budgets are presented, for various assumed conditions. The optimum surface conditions would occur with winter overcast and summer clear sky. The earth-atmosphere radiation budget is presented for an open Polar Ocean. Relatively minor variations in any term can result in a complete freeze-over or complete melting. The atmospheric advection required with an open Polar Ocean would decrease significantly from the present. It might even become, in winter, a heat export from the Polar Ocean.

A series of photometric measurements are presented which were made in November 1958 in transit to and in the McMurdo Sound area, Antarctica. Included are luminance distributions of clear and overcast skies, several measurements of air clarity, the diffuse/total illuminance ratio, and luminances of ice and sea surface details under a typical condition of weather and lighting. A photographic technique is described for measuring meteorological range or air clarity. A value of 73.9 nautical miles for a contrast transmittance of 0.02 on a clear, cloudless day was found. Applications of Fritz's theory to the overcast sky data are discussed.

Various methods of estimating atmospheric radiation including the use of radiation charts and six empirical formulas are examined, using micrometeorological data collected at Davis, Calif. The Bolz method for adjusting the clear-sky estimates of atmospheric radiation from empirical formulas for cloudy, conditions is studied using observed cloud conditions and measured atmospheric radiation. This method works well for overcast low-cloud conditions. However, in high-cloud conditions with less than complete sky coverage, it is less satisfactory, perhaps due to problems in analytically representing the cloud conditions.

TIROS II measured the emission from the planet Earth in the atmospheric water-vapor window near 10 microns. During carefully selected times, when no clouds were present near sunrise or near noon, the measurements served to estimate the change in temperature of the ground. Under these conditions, although the change in transmittance of the atmosphere can be neglected for the purpose of computing the ground temperature change, the transmittance through the atmosphere must still be evaluated. During cloudless sky conditions over Wisconsin on 23 November 1960, the change in ground temperature from sunrise to noon was about 24C as estimated from satellite measurements. The change in shelter air temperature was less than 15C over the same time interval. In overcast areas, the movement and development of the clouds determine the variation of the energy measured by the satellite.

The possibilities of the wilting process have been investigated, with the ultimate object of determining its effect on the quality of farm silage. Attention has been confined mainly to mild or partial wilting, rather than severe wilting, since the danger of ensiling excessively dry material, especially when it is not chopped, is well recognised. Preliminary field tests were conducted to determine the rate and extent of the fall in moisture content in long and in bruised herbage, wilted for periods not exceeding 24 hours. Subsequently the wilted silages were made in experimental silos and, finally, in trench silos on a farm scale. This first paper deals with the field trials. Results show that important reductions in moisture content can be obtained in all but very poor weather. In good weather, moisture content may easily fall from the 80% to the 70% level; in poor weather (cool, overcast, with occasional showers) moisture loss still occurs.

The rectangular light source is more frequently encountered in engineering practice than any other form. Thus, both for artificial lighting and natural lighting, it is desirable to have convenient methods of obtaining the light distributions produced by rectangular sources. We have attempted to supply this need by calculating pharosage from sources of uniform helios and also for the non-uniform sources representing average overcast skies. Figures 5 to io are found to be particularly convenient in the visualization of light distributions. The results of these graphs are readily extended to any point and to surfaces tilted at any angle, provided that the plane of the illuminated surface does not cut the source. In conclusion, we wish to express our appreciation of the careful work of the computers: Messrs. L. S. Castlemann M. S. Cettei, J. C. Gibbs, A. L. Keller, G. J. Laurent, V. Lippitt, J. M. Margolskee, L. Mautner, J. Topalian.

ARECENT study1 was made of the effect of daily weather on the daily total store sales and the daily sales of three departments of Younker Bros., Inc., Des Moines, Iowa. The period covered in the study was the seven weeks before Easter, I940-48 inclusive. In this article only the relationship between the weather and the total sales of the store will be discussed. Many studies have been made of the effects of weather on various kinds of business activity in recent years. Studies have been made of weather's effect on gas consumption, electrical consumption, agricultural production, electrical power failures, etc. But little has been done on the subject of weather's effects on the retail sale of merchandise. Weather affects gas consumption mainly through the effect of temperature on people. In cities in which gas is used for household heating the relation between temperature and gas consumption is rather obvious. The relation between gas consumption and humidity and wind velocity is not so apparent but there probably is one. With respect to electrical consumption, cloudiness as well as other weather elements affect consumption. When the sky is overcast and the clouds are thick people will turn on their lights. Agricultural production is affected by many weather elements, but the time and amount of precipitation are probably the most important to most crops.

No Abstract Available. [Reprinted from Physical Review, 1908, 28: 122–131.] June, 1908

During the midwinter months the general airflow over N. Greenland is southwesterly, but near the surface of the ice sheet, which is cooled by radiation in the polar night, katabatic winds flow from the higher parts of the ice sheet towards the coast. At sheltered places on or near the coast pools of cold stagnant air collect in fine weather when the pressure gradient is weak. Analysis of the 700 mb charts for two midwinter seasons shows that breaks in the predominantly fine weather were caused by depressions and their associated fronts which crossed the inland ice. There were about 15 disturbances per month which affected N. Greenland, but only a few of these caused precipitation. Most of the fronts were weak and the snowfall slight. During the first period of two midwinter months under consideration the only considerable fall of snow occurred when a deep depression remained almost stationary over S. Greenland for three days and drew moist air from the N. Atlantic over N. Greenland. The onset of the strong northwesterly wind on the coast after a period of calm is generally associated with the passage of a cold front. There is normally an inversion in the lowest layers above the ice sheet and the air temperature on the inland ice varies with the wind speed and the air mass. It is estimated that the temperature difference between the bottom and top of the inversion varies from around 0°C in overcast conditions with a strong wind to around 25°C in clear and calm conditions. Warm air is sometimes carried in the southwesterly circulation over the inland ice : the highest temperature measured on the ice sheet in the midwinter months was −18°C in a warm sector, and the lowest was −66°C in fine and almost calm weather. On the coast the onset of the northwesterly wind is marked by a sudden rise of temperature and fall of humidity : when the wind falls to calm the temperature falls rapidly at first, but within 24 hours reaches a value from which it differs little during the period of several days before the next onset of the northwesterly wind. There is a fairly close relationship between the height and intensity of drift snow, the wind speed and the visibility. Snow does not begin to drift until the wind speed reaches 10 kt; the snow drift is moderate with a visibility of about 2 km when the wind speed is 17 kt and is heavy with a visibility of about 200 m when the wind speed is 27 kt. After a spell of fine weather over N. Greenland drift snow was absent on the inland ice even with a wind speed of 21 kt. Drift snow was observed in the coastal area only after a fall of snow. A comparison of the mean pressures and precipitation totals for the midwinter months under review with mean charts and mean monthly precipitation totals for other stations in the area for different years suggests that the two Januarys studied were normal months, but the two Decembers were abnormal.

The variation in the transmission of diffuse solar radiation was measured over the floor area of a 30 ft wide E.-W. glasshouse of metal construction without purlin posts, glazed with diffusing glass. The measurements were made on overcast days during the period of construction and the effects of the different components of the structure separated. On a cloudless summer day, simultaneous measurements of the proportion of diffuse radiation outside and the total of direct and diffuse radiation both outside and inside the glasshouse enabled the transmission of the direct component to be calculated. There was a high transmission of both direct and diffuse radiation, although the latter decreased near the edges of the house. The use of diffusing glass did not cause any appreciable loss in transmission, but the steel structure caused as much obstruction as that in another clear-span house of twice the width.

In an attempt to learn more about the so-called “map” component in pigeon navigation, nine series of tests comprising 34 test releases were performed at a release site, 89 miles NNE of Ithaca, New York, where Cornell pigeons regularly depart nonrandomly but with a large clockwise deviation from the true home direction. The tests included releases of: (1) experienced pigeons new to the site, under sun; (2) pigeons with previous experience at the site, under sun; (3) experienced pigeons new to the site, under total overcast; (4) pigeons with previous experience at the site, under total overcast; (5) first-flight youngsters, under sun; (6) directionally trained pigeons; (7) pigeons from two other Ithaca-area lofts; (8) pigeons from two more distant lofts; (9) Bank Swallows from an Ithaca colony; (10) clock-shifted pigeons; (11) radio- and airplane-tracked pigeons.

Typhoon Billie exhibited mesoscale warm-core characteristics and developed winds of typhoon intensity without ever forming a wall cloud around the eye. Clouds that swirled into the storm center were flattened cumulus and stratocumulus with cloud tops at 4,000 to 5,000 ft. It was clear of all higher cloudiness in the area of the eye. The storm center lay on the northern edge of major overcast cloudiness and its appearance was similar to that of an intense Stage C tropical cyclone. Satellite pictures together with conventional analyses and information gathered by the author as a pilot on reconnaissance missions into the storm indicate that Billie intensified to typhoon strength as a result of mesoscale changes in the area of the eye. It is suggested that Billie represents a type of typhoon whose maximum wind speeds are limited because of failure to develop an encircling wall cloud.

The accumulated data of a long series of homing experiments carried out with young pigeons is examined in statistical detail. Bico-ordinate navigation can only be demonstrated in sunny conditions, and with overcast skies the birds scatter at random. This holds for a number of different experimental situations. The hypothesis that pigeons use a form of sun-navigation, deriving latitude and longitude from the sun position alone is re-examined in detail. None of the requirements are outside the theoretical range of the organ concerned, or beyond the bounds of possibility. Examination of the errors made under sunny conditions shows that their nature and variation are as expected on the basis of the hypothesis. So also is the variation in error with the length of time of observation. By excluding sun and sky for a number of days before release a re-orientation away from home was obtained. This could only be explained if the birds were failing to correct for the seasonal variation in the sun’s altitude, and deriving their latitude from altitude measurements. Radical changes in accustomed release times produced some increase in longitude errors. After treatment aimed at desynchronizing any internal chronometer a disorientation was obtained in the field. It is therefore very probable that longitude determination is on a time basis, as proposed in the hypothesis. Future lines of research in this problem are indicated.

It is said that deep scattering layer (DSL) in the sea is caused by the reflection of sonic waves propagated into the sea from pycnocline or layers of small organisms. This study deals with the topics mentioned in the title as a step in the study of ecology of salmon in the high-sea region of the northern North Pacific. The observations were carried out on board the Hokkomaru, research boat of Fisheries Agency, Ministry of Agriculture, in the northwestern area of the North Pacific during the period from July 11 to Aug. 5, 1964. Two kinds of ultrasonic finders, 200 KC and 28 KC respectivety, were used by attaching them outside the hull of the ship. The results of the observations are summarized as follow: 1) It was overcast throughout the period of observations. The daylight intensity at the sea surface averaged (4-6)×102 lux at the time of sunrise as well as at sunset, while it was (8-10)×104 lux at noon. 2) The transparency of water was 15m. The depth at which the submarine illumination was as much as one lux corresponded to 62-64m at the time of sunrise and sunset and 123-125m at noon. 3) One or two layers of DSL were usually observed. These layers (1st and 2nd layers) changed their depth diurnally. Somtimes a third layer was found, but it did not shift vertically. 4) When two ultrasonic finders were operated at the same time, both the 1st and 2nd layers of DSL were recorded by the 200 KC finder. While only the 1st one was recorded by the 28 KC finder. 5) In order to observe difference in reflection loss of 200 KC and 28 KC sonic waves with the form of plankters, a test was made using a water tank. It was found that difference in reflection loss of Euphausia pacifica between 200 KC and 28 KC was ca. 5 db, and that of copepods such as Calanus plumchrus and Calanus cristatus was ca. 10 db. Such a difference may have been caused by difference in the size of organisms. The specific gravity of Euphausia pacifica, Calanus plumchrus, Calanus cristaus and Themisto sp. is almost same, i. e. ca. 1.06. 6) Organisms collected from the 1st-3rd layers of DSL by horizontal towing of a plankton net, 60cm diameter, 32 mesh/inch, mesh opening 0.53mm, were mainly euphausiids, copepods, amphipods, etc.

Apparatus and method to measure the soil biota respiration was described. Daily production rates of a tropical pond community were measured and classified into different types. High production rates of hydrophytes were associated with low amounts of plant biomass both in the field and under experimental conditions on bright and overcast days. Decrease in the production rates on overcast days was 2 to 3 fold up to 353.75 g/m3. Highly turbid pond water was twofold less productive than clear waters. Summer pulse in the production rates was recorded. Plankton as well as soil biota respiratory rates were higher during summer due to higher tropical temperatures. The efficiency ratios of individuals and trophic levels compared favourably with those reported earlier. The high respiration efficiency ratios for herbivores may be due to high temperatures. The input and output of energy of the tropical pond community were measured and the energy flow diagram was constructed. The community metabolism of the tropical pond community was much higher than the communities whose metabolism has been studied else where.

Extensive covers of cpilithic diatoms seldom develop on intertidal substrates in southern Oregon in the prcscnce of grazing animals and macroscopic algae. If an area is cleared, however, a brown coating of diatoms often appears in 2 to 3 weeks, but the density depends on the season and the local conditions during tidal emergence. I have attempted to evaluate the effects of exposure on the vertical distribution of diatoms in the absence of grazers and macrophytes. The differences in exposure to insolation were emphasized. Vertical transects in the same block, facing north, east, west, and south (

Measurements of incoming global, diffuse and reflected radiation at a tower site in Lake Ontario are used to evaluate components of surface albedo. Albedo for diffuse radiation lies between 0.074 and 0.082 and a coefficient for backscatter from sub-surface water layers shows little deviation from a mean of 0.017. Direct beam albedo for a calm surface follows the Fresnel law. Waves increase direct-beam albedo particularly at higher solar zenith angles. A pronounced dependence of albedo upon zenith angle for clear skies decreases with increasing cloud amount and becomes undetectable in overcast conditions. On a daily basis, albedo ranged between 0.07 in early July to 0.11 in mid-November. Day-to-day scatter is within ±1% of the mean seasonal trend.

Laboratory, greenhouse and seed-bed trials of copper and organic fungicides for the control of Colletotrichum tabacum on tobacco were made in Southern Rhodesia. In the seed-bed trials the best control was obtained by sprays of maneb, thiram, zineb and captan. During the hot, dry weather in the early part of the season little damage was caused by the disease and it was easier to control than later, when rain and overcast weather were more frequent. Mixtures of zineb and copper compounds gave better control than either component alone. When seed-beds were covered with light cloth for shade, they suffered greater damage from the disease than when a thin grass mulch was used.

With a new continuous measurement method, the radon content of the atmosphere at different levels above ground between 0.5 and 4 m was recorded at Aachen, Germany. Evaluation of simultaneous measurements of the radon daughters with a stepwise progressive filter (Schrittfilter) showed a close relation between radon and its daughters and the meteorological factors at the measuring place. Questions discussed in the paper include the daily variations of the radon concentration in relation to the exchange (Austausch), the radioactive equilibrium of radon and its daughters at different heights, and influences of the wind direction. It was found that during temperature inversions the concentration of radon and its daughters was enlarged whilst on overcast days the mean daily variation of both the radon and the radon daughter concentration was smaller. Moreover, the radon and thoron daughters were correlated with the dust content of the air. DOI: 10.1111/j.2153-3490.1966.tb00280.x

Summary 1. ‘Light’ covers a variety of related measures of radiant energy: the particular usage must be defined for each investigation. 2. Light in the open varies in intensity and spectral composition, both with time and over space. These variations can usually be formulated mathematically and used to predict conditions in plant communities. 3. Light may be measured directly with radiometric instruments, responding equally to all wavelengths within a certain waveband, or with photometric instruments, whose response approximates to that of the human eye. The use of the former is desirable whenever possible, as it simplifies subsequent interpretation of the results. 4. Photographs covering an entire hemisphere can be used to estimate the contribution of diffuse and direct light separately under many circumstances. They are a great help with the interpretation of many forms of measurement. 5. If the percentage of light transmitted by a plant community is to be treated as constant, diffuse and direct light must be treated separately. Even so, it is only the average transmission over considerable periods that is reasonably constant. The pattern of diffuse light distribution in the community is very different on clear and on cloudy days. 6. In general, most diffuse light penetrates the plant community near the zenith. However, on clear days the aureole of light near the sun shining through a low-altitude canopy gap may entirely alter this relationship. 7. The distribution of direct light can be analysed from tracing the path of the sun across the canopy. The sun shines unobstructed through gaps of an angular width greater than 1/2. 8. In some herbaceous communities the logarithm of relative intensity of diffuse light inside and outside the community is approximately proportional to the cumulative leaf area per unit area of ground above the level investigated. The relation varies with the angle of incidence of direct sunlight. The relation is not valid in all communities, and the errors involved in the assumption of its validity require further investigation. 9. The leafy plant community reflects and transmits light selectively. It is important to allow for the interaction of changed spectral composition on the spectral sensitivity of the instrument when making estimates of albedo or percentage light transmission. 10. Although the spectral characteristics of reflexion and transmission of individual leaves are nearly identical, this is not so for plant communities with a highly inhomo-geneous structure. 11. The percentage of total light transmitted usually increases with increasing cloud cover of the sky. The absolute intensity of diffuse light in the stand is usually higher when the sky is partly overcast than when the sky is entirely covered or clear. This is due to the increase of total light in the open with decrease of cloud cover, while the proportion of diffuse light in the total decreases with decrease in cloud cover. Provided the stand transmits more diffuse than direct light, the percentage transmission of the total will therefore fall as the total increases. 12. Daily variation of diffuse light generally follows that in the open. 13. In deciduous woods a light phase before leaf expansion and a shade phase after it can be distinguished. Each phase is characterized by a fairly constant percentage of diffuse light: that of direct light depends on daily and seasonal variation of solar altitude, increasing with increasing altitude. 14. Light measurements given as percentages of that in the open may disguise important features of the variation of absolute amounts of light. Wherever possible these absolute quantities should be calculated. Where no direct meteorological data exist, it is often possible to make reasonable assumption from other data. The precise time, place and cloud conditions should be given for each measurement, 15. Because of the great variety of instruments and techniques used, often inadequately described, comparison of results is nearly impossible. A thorough examination of the magnitude of the errors of each technique is badly needed.

Many and various methods have been employed at different times for the measurement of light in ecological habitats, and these methods have already been critically reviewed by the writer ('25). In the same paper a new method and instrument were set forth, and later ('27) a land model of this instrument was described, with illustrations. These instruments, which have hitherto had no name, except that of ecological photometer, and which I now refer to, for the sake of brevity, as the ecophotomteter, aquatic model, and ecophotometer, land model, have been employed in making many measurements, and have continued to perform satisfactorily. The land model has been used, not only in various habitats, but in measuring the light in a single habitat at sunset, in the gloaming, in moonlight, and in starlight. This instrument has also been calibrated in terms of total light energy, as measured by a Moll-Richard-Gorczynski pyrheliometer, and the accompanying graph (Fig. I) gives the results of this comparison. It will be seen that a practically " straight-line " relationship exists for full sunlight, for faint sunlight, and for the light from a " cloudy-bright " sky, but that the slope of the lines is different for the different light conditions. This is exactly what was to be expected, because in bright sunlight the red and yellow rays, which have the greatest heating effect, predominate, while they are less in the case of faint sunlight (that is, sunlight which just casts a faint shadow), and least in the light from an overcast, but bright, sky. The comparison for the light from a dull sky could not be made, because the pyrheliometer did not respond at all to such low intensities. It is thus clear that the " photic effect," as distinct from the " thermic effect," is measured far more efficiently by the panchromatic plate than by the pyrheliometer, as the shorter wave-lengths (which include the near ultra-violet, violet and blue) which have a decided influence on many important processes in plants and animals, are adequately recorded. In connection with this graph it should be stated that: (I) full noon sunlight, on July 12th, latitude 450 north, sea level, was taken as standard (ioo per cent) ; (2) that the photometer was in all cases inclined so as to be at rioht angles to the incident radiation, so as to be in the same position as the receiving disc of the pyrheliometer; (3) that two batches of panchromatic plates were used; and (4) that each plate was developed separately. The last two facts are mentioned because they show that no

Cloud amount and duration of sunshine are generally used to estimate direct and diffuse solar radiation income at the ground, where radiation instruments are not available. This method has serious drawbacks and a consideration of cloud type is also necessary. The different elements required for the calculation of radiation income at the ground are discussed. Such calculation can give only general results, and measured values of radiation in the Arctic, with different cloud types, are therefore examined and presented. The magnitude is discussed of the values in the Arctic of albedo of cloud tops, ground albedo, and the effect of composite cloud types. From the results it is possible to construct tables which show the depletion factor with 10/10 could cover for different combinations of cloud type frequencies. These tables make it possible to obtain approximate radiation income with mean overcast conditions, provided that the clear key radiation is known. The results are applicable to the Polar Oce...

The widely held view that in cold weather one feels colder when the atmosphere is damp than when it is dry was investigated on clothed subjects. Subjective coldness and dampness, determined by a panel of six people who walked about half a mile in the open in winter, were compared with measurements of temperature, relative humidity, and other meteorological variables. The panellists comments showed that when the weather is cold, people think it is damp when the sky is overcast, irrespective of relative humidity. However, when this factor has been allowed for there still appears to be some correlation between subjective dampness and relative humidity. Relative humidity does appear to have an effect on how cold one feels at low temperatures, but only to a limited extent, and in the opposite direction to popular belief.

From April 2 to 7, 1960, the meteorological satellite Tiros I televised the Alps and the surrounding area. The Alpine mountains were snow covered but the river valleys and lakes were readily discernible in the pictures under clear sky conditions. The pictures show marked differences when the area was overcast as compared to times when the area was clear or partly cloudy. These differences are discussed with the aid of satellite pictures and surface cloud cover maps.

The transmission of solar radiation was measured at various positions in a 63 ft wide glasshouse orientated E.-W. The obstruction to diffuse radiation caused by the various components of the structure was found by making measurements on overcast days during the course of construction. Measurements were made on sunny days at three periods of the year in the completed house, and simultaneous measurements of the proportion of diffuse radiation outdoors made it possible to calculate separately the transmission of the direct component. The mean daily transmission of the direct component was 57% in summer and 68% in winter; that of the diffuse component was 69%. During winter, the transmission of direct and diffuse radiation combined was much greater than in a 30 ft vinery house having a N.-S. orientation. The south half of the house compared favourably with a narrow E.-W. orientated propagation house. Changes in shape could lead to improvements in the transmission, particularly in that of direct radiation.

Relationships between net radiation (QN) and global solar radiation (QS) and between the ratios of QS and solar radiation at the top of the atmosphere (QS/QA) and duration of bright sunshine and daylength (n/N) were determined by regression analysis at Guelph, Ontario, Canada. The data used were recorded at the Guelph O.A.C. climatological station from March, 1964 to February, 1969. Results showed that during the spring, summer, and autumn seasons, QS alone can be used to estimate QN satisfactorily. Daily values of QN are about 50% of QS. The relationship derived for estimating QS from duration of bright sunshine (n) showed good agreement with findings of previous workers. QS varies between 20 and 80% of QA for overcast to cloudless days. The relationships derived in this study can be used to estimate net and solar radiation on a daily basis when these measurements are unavailable.