Diurnal Variation Of Air Temperature Research Articles

Forecasting diurnal variations in meteorological parameters for predicting fire behaviour

Empirical models for predicting diurnal variations in air temperature, wind speed, and relative humidity, given daily maximum and minimum values, latitude, and Julian date, have been developed. Solar heating during the daytime is quantitatively depicted using a truncated sine function, and nighttime cooling is characterized by an exponential decay function. Daily wind-speed trends echo diurnal temperature patterns, and relative humidity is modelled as a function of temperature by assuming that absolute humidity remains constant throughout the day. The time of occurrence of daily maxima and minima in temperature and wind speed varies seasonally according to changes in day length. Maximum temperature and wind speed typically occur later in the day than the maximum solar insolation. The magnitude of this lag depends on both time of year and latitude. The models were parameterized for two locations in Australia and observed, and modelled variations in temperature, relative humidity, and wind speed were used to forecast diurnal trends in fire behaviour. Predicted fire behaviour compared favourably in the two cases considering the very simple modelling approach employed.

Diurnal variation of air temperature across the north pacific

Diurnal variations of air temperature and four other weather variables are presented for an oceanographic cruise that sailed along 35°N from California to Japan during March and April, 1976. The data were sampled every two hours for 35 days. Air temperature shows a double maximum, one before and one after a noon minimum, on several individual days and in the average over all days. A similar phenomenon was described 30 years ago for air temperaturesfrom two weather ships in the western Pacific. The only existing explanation, adiabatic heating due to the semidiurnal pressure variation, is shown to be too small to account for the morning maximum in the present temperature data. No alternative explanation is offered at this time.

Diurnal variations of wind speeds at a shortgrass prairie site — a model

Comparison of the mean monthly diurnal variation of wind speed and air temperature (2 m) shows that they have the same pattern and that these patterns change seasonally in the same manner. A model for stimulated diurnal variation in air temperature was used to represent diurnal variations of surface wind speeds at a shortgrass prairie site. Inputs for the model are latitude, Julian date and daily wind travel. The important assumptions for the model are (1) the maximum wind speed occurs during the afternoon period, (2) the minimum wind speed occurs sometime around sunrise, (3) during the day the wind speeds can be described with a truncated sine function, and (4) during the night the wind speeds can be described with an exponential function. Reasonable approximations of long-term hourly mean diurnal variations in wind speed were simulated; however, the model was less accurate for individual days. The wind speed model has potential application in estimating wind statistics when wind power calculations are required, and as abiotic data input for research and application models.

Studies on the Diurnal Course of Air Temperature

1. The author proposed the model of diurnal course of air temperature which is required to analyze a crop growth. The relationship between air temperature (x) and time (t) is shown by the following “modified sine-curve (MS-curve)”, x=f(t, A, B, H, k)=(B-A)sin2(πt/2H)+A+k(B-A)sin2(πt/H), for |k|≤1/4 (1)where A is the minimum air temperature, B the maximum one, H the period between emergence times of A and B, and k the modification coefficient which shows the ratio of deviation from sine-curve.The two models of diurnal course of air temperature were devised from MS-curve. The one is “two-half cycle model” which simulates the rising course of the air temperature in a day by the half cycle of x=f(t, A1, B, H, k1) and the descending course by that of x=f(24-t, A2, B, 24-H, k2). The other is “one-half cycle model” which expresses the mean diurnal variation of air temperature by the half cycle of x=f (t, A, B, 24, km). In these equations, A1 and A2 are the morning minimum air temperature and that of the next day, and k1 and k2 are the modification coefficients to the periods A1 to B and B to A2, respectively, km is the daily mean modification coefficient shown by km={k1H+k2(24-H)}/24.2. The air temperature in 1968-1977 at Morioka in Japan was analyzed using these models. The following seasonal values were obtained;k1=-0.01-0.08, k2=-0.20-0.10, km=-0.13-0.05, H=8.4-10.0 hours, and tA=4.2-5.5, where tA is the emergence time of minimum air temperature. It was found that k1 and k2 values investigated for instance at Sapporo, Tokyo and Fukuoka were roughly similar to those values at Morioka. Then, the emergence time periods of classified air temperature, which were calculated from the reverse function of MS-curve using these coefficient values, agreed very well with the observed values.3. The daily mean air temperature θm which is estimated from the integration of MS-curve is shown as follows;θm=(A+B)/2+km(B-A)/2. (2)On the other hand, the daily mean air temperature θn which is obtained from the observations of several times a day is shown as follows;θn=(A+B)/2+lm(B-A), (3)where (A+B)/2 is the average air temperature and lm the coefficient of diurnal range of air temperature to convert (A+B)/2 into θn. The convenient equations of km and θm at Morioka were obtained from Eq. (2). Eq. (3), and the values observed at intervals of three hours as shown below, km=2lm-0.034, and (4)θm=(A+B)/2+(lm-0.017)(B-A). (5)

Microhabitat, water relations, and photosynthesis of a desert fern, Notholaena parryi.

Interrelationships between morphology, microhabitat, water relations, and photosynthesis of a xeric fern, Notholaena parryi D.C. Eat. (Pteridaceae), were examined in the western Colorado desert. In its typical microhabitat rock outcroppings protected N. parryi from direct sunlight and moderated the diurnal variations in air temperature. For example, frond temperature at noon in late winter was 15.3° C, which was 7.3° C cooler than an energy budget simulation predicting frond temperature at an exposed site. The lowest soil water potential leading to daytime stomatal opening was about-1.5 MPa (-15 bars). Rainfall runoff that was channeled to the periphery of the rocks caused Ψsoil near the fern roots to rise above-1.5 MPa even after light rainfalls, and it remained above-1.5 MPa longer after rainfall than in non-rocky sites.The water potential gradient along the stipe necessary to support the observed rates of transpiration was about-10 MPa m-1; such a large gradient reflected the small conducting area in the xylem. The water vapor conductance decreased as the frond temperature was raised, an effect that became proportionally greater as the soil dried out. The daytime water-use efficiency (mass CO2 fixed/mass water transpired) was 0.0058 for a spring day. Individual fronds reached 90% of light saturation for photosynthesis at only 100 μEinsteins m-2 s-1, a photosynthetically active radiation similar to that from the diffuse sunlight incident on the generally north-facing microhabitat of the fern. Below 50 μE m-2 s-1 the quantum requirement was 13 Einsteins absorbed/mole CO2 fixed. The ratio of chlorophyll to P700 was 552, indicating a fairly large photosynthetic unit that is characteristic of plants adapted to shaded habitats. The temperature optimum for net photosynthesis shifted from 13° C in midwinter (mean daily air temperature of 11° C) to 19° C in early fall (air temperature of 23° C).

Averaging errors in monthly evaporation estimates

The problem of computing evaporation from monthly mean values of temperature, relative humidity, and wind is considered with specific reference to a Dalton‐type evaporation formula. Leading contributions due to nonlinearities, covariances, and their interactions are identified separately by expanding saturation vapor pressure as a Taylor series in temperature using the Clausius‐Clapeyron equation. A truncated form of the expansion is tested by using observations from a land station. A crude model of diurnal variations in air temperature, relative humidity, and wind speed is used to predict nonlinearity and covariance evaporation errors from monthly mean observations at 2 times per day. The model appears to be accurate to within ±5% in warm season months but fails in winter when diurnal variability is negligible in comparison with air mass changes in weather elements at mid‐latitude continental locations. Covariance and nonlinearity errors do not compensate each other in winter with the result that averaging errors can reach 20–25%.

Air-Sea Transfer of Momentum, Heat and Water Determined from Profile Measurements During BOMEX

Abstract One hundred forty-one simultaneous wind speed, temperature and humidity profiles measured during the Barbados Oceanographic and Meteorological Experiment (BOMEX) are analyzed. The observations were from heights 2–11 m above MSL and were made from the R/V Flip, a research vessel specially designed to be stable at sea. The wind measurements are corrected for the interference of Flip's hull with the air flow. Evaporation estimates from the profiles are in fair agreement with simultaneous estimates by the eddy-correlation method. However, the heat fluxes estimated by the two methods are in poor agreement. There appear to be diurnal variations in air temperature, sea surface temperature and stress. The flux of latent heat is large, averaging 17 mW cm−2, while the flux of sensible heat is always upward and ∼1 mW cm−2.

The Influence of Sea Breeze on the Distribution of the Air Temperature in Summer in Miyagi Prefecture

Concerning the distribution of the air temperature in summer in Miyagi prefecture, the author found many exmaples of the pattern as is shown in the Figure, with lower temperature in the coastal region. And the temperature gradient form the coast toward the inland was investigated in relation to the diurnal changes. The author observed diurnal variation of air temperature at several places in summer 1964. In the coastal region, the air temperature first rises by a few degrees, then remains constant after the breeze begins to blow. This temperature continues as long as the sea breeze blows. Therefore, the air temperature becomes higher according to the distance from the coast, because the sea breeze is later to advance toward inland.Thus, the gradient twoards inland mentioned above can be understood from the view-point of the regional difference of diurnal variation of the air temperature.

Diurnal variation of Atmospheric Electric Potential Gradient at Colaba (Bombay) examined for the Universal Component and relationship with meteorological elements

The atmospheric electric potential gradient (P.G.) data of Colaba (Bombay) are averaged over the period 1936 to 1955 to obtain the mean diurnal variation for the different months of the year. The diurnal variations are regular and for large amplitude only for the winter months of November to February. The diurnal variations for these months are harmonically analysed to see if the universal component of the diurnal variation found for the ocean areas as well as some land stations by Mauchly (1923), is manifested in the variations at Colaba. The phase of the 24-hourwave is found to differ from that found by Mauchly by 5 to 10 hours. It is concluded that
 the universal component of the diurnal variation in P .G .does not readily manifest itself at Colaba.
 
 The relationships between diurnal variation of P .G. and those of the meteorological elements, barometric pressure, air temperature and relative humidity are next examined. The statistical correlation coefficient between P.G. and barometric pressure variations is +0.71, that between P.G. and air temperature variations -0.67 and the value between P.G. and relative humidity is +0.57.
 
 A confirmation of the relationships is sought for in the phase relationships of the significant harmonic components of the diurnal variations of P .G. and the meteorological elements for the winter months. For the P .G. diurnal variation both the 24:hour wave and the 12-hour wave are almost equally significant. For barometric {16a) pressure it is the 12-hour component which is significant, while the 24-hour components predominate in the diurnal variations of air temperature and relative humidity. It is found that the 12-hour waves of P.G. and barometric pressure variations are very nearly in phase. The 24-hour waves of P.G. and air temperature are in antiphase while
 those of P.G. and relative humidity are nearly in phase.
 
 Assuming the electrical state of the atmosphere to be in quasi-static eqnilibrium an attempt is made to examine possible ways by which meteorological elements can influence P.G.

Type of Diurnal Variations of Air Temperature during Summer Season in Japan

In order to analyse the relationship of air temperature to the growth of crops, the classificatory constitution of air temperature during the growth stages of crops should be clarified. But the assumption of such classification from the recording paper is troublesome and collection of recording papers from various places is difficult. From these reasons, the writer tried to obtain the classificatory constitution by calculation through the typification of diurnal variations of air temperature.Assuming that θmin shows minimum air temperature and that R represents diurnal range of air temperature, θt showing air temperature at the time of t becomes as follows:θt=θmin+atR (1)where at is the coefficient of diurnal range of air temperature. Through the same procedure, θ0 showing mean daily air temperature follows asθ0=θmin+aDR (2)where aD shows the average of at.The average air temperature θm otained from the daily maximum and the minimum is as follows:θm=θmin+0.50R (3)From formulas (2) and (3) aD is obtained:aD=0.50-Δθ/R (4)where Δθ=θm-θ0.The monthly average values of aD calculated from (4) by use of the data from the main stations in Japan are shown in Fig. 1.The distribution of annual variation of aD classified as A1, A2, B and C types is shown in Fig. 3. The average aD ranging from May to August becomes 0.45 in Japan (Fig. 3). By drawing both diurnal variation curves of air temperatures having various aD values (Fig. 4) and the curve (C-curve) put the case that the emergence times of the maximum and the minimum points on a sine-curve are distorted as 5a.m. and 2p.m., Δt showing the difference of emergible time more than constant at obtaind from both diurnal variation curve of air temperature having certain aD value and C-curve was obtained (Fig. 5). Δt was ascertained to be -1.3 hours in the case of aD=0.45 and at=0.1-0.9. As the emergible time of C-curve at the case of more thanconstant at value is equal to the case of sine-curve, it is probable to obtain the emergible time by the calculation and the curve for aD=0.45 can be obtained by adjusting Δt, -1.3 hours (Fig. 7, S-curve). An example for the diurnal variation S-curve of air temperature was shown in Fig. 4 (full line). Such S-curve will be taken as a typical diurnal variation curve of air temperature during summer season in Japan. By using S-curve, the emergible times of classificatory air temperatures will be easily obtained from Fig. 6, when the air temperature is substituted by at in a formula (1).

On a New Expression for the Diurnal Variation of Air Temperature

On a New Expression for the Diurnal Variation of Air Temperature

東京に於ける氣温の日變化に就いて

東京に於ける氣温の日變化に就いて

THE INFLUENCE OF ENVIRONMENTAL CONDITIONS ON THE DEVELOPMENT OF THE ANGULAR LEAF‐SPOT DISEASE OF COTTON

SUMMARY.1. Experiments on the influence of variations in the environmental conditions on the bacterial disease of cotton plants caused by Bacterium malvacearum are described.2. A regular diurnal variation in soil temperature is shown to have the same effect on primary infection of seedlings as a constant temperature near the mean of the fluctuations.3. The mean soil temperature at the time of sowing and for the first few days of germination is the chief controlling factor in primary infection, other factors being equal. Subsequent variations in the soil temperature have little effect on the incidence of the disease.4. The amount of disease resulting from infection of the seed, i.e. primary infection, is higher at soil moisture contents approaching saturation than at normal moisture contents in a given type of soil.5. The amount of primary infection at a given soil temperature and moisture content varies with the type of soil.6. A regular diurnal variation of air temperature has the same effect on secondary infection resulting from spray‐inoculation of young plants as a constant temperature near to, or slightly above, the mean of the variations.7. Other things being equal, the amount of infection resulting from spray‐inoculation depends upon the mean temperature prevailing during the incubation period of the disease, the actual temperature at the time of inoculation being unimportant.8. Atmospheric humidity is a conditioning factor in secondary infection only during a short period (less than 48 hours) following inoculation. Its importance lies in its control of the time during which the infection droplets persist. Once penetration of the tissues has been effected variations in the external humidity have little direct effect.9. Plants kept in total darkness are relatively resistant to infection.10. Plants grown in continuous light are no more susceptible than those grown under a daily period of 17 hours' illumination of approximately 1200 foot‐candles.11. The time of inoculation in relation to the period of illumination does not appear to have any marked effect on the amount of infection.12. The relations of the whole series of experiments on the influence of environmental conditions are discussed.