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An Astrobee D rocket carrying a dual-channel radiometer (1.40- to 1.65-μm and 1.85- to 2.12-μm spectral band passes) was launched on March 6, 1972, at 0200 LT from Poker Flat, Alaska. The spectral band passes were chosen so that the lower (ν = 2, 3, 4, 5) and upper (ν = 7, 8, 9) vibrational levels of OH in the Δν = 2 sequence could be monitored simultaneously. Launch criteria were established from ground-based radiometric observations that indicated a steady night airglow of 240 kR in the 1.40- to 1.65-μm band pass 2 hours prior to and throughout the flight. Altitude profiles of OH emission were derived from data from both channels and show OH to be layered, peak volume emissions occurring at 83.5 km. Under the assumption that H + O3 → OH‡ + O2 is the principal production mechanism, synthetic spectra were integrated over the instrument spectral response characteristics of the two radiometer channels. At altitudes above 83 km, quenching due to the reaction OH‡ + O → O2 + H is evident, which requires an atomic oxygen concentration of 1011 cm−3 at 83 km, increasing to 8 × 1011 cm−3 at 88 km.

The optimum signal processing to follow a given radiometer front-end is derived when it is desired to estimate, with smallest rms error, the temperature of a radio source. We find, for the important special case of small sources, that the optimum radiometer is implemented by the use of a compensating filter followed by square-law detection and integration. We consider two examples of receiver front-end gain characteristics, the Lorentzian and Gaussian shapes. Improvement over conventional radiometer performance is shown to be possible.

Schmidt and Leppert (1970) have reported experimental and analytical heat-transfer data for partially ionized argon flowing in a circular tube. The finite-difference model used, which was based on the then best available information, considerably underpredicted the total heat flux to the wall in the first few tube diameters. The present study has developed a new finite-difference program, based on the Spalding-Patankar GEN program, which predicts local heat transfer for a partially ionized argon plasma flowing in a cooled, circular tube. The equilibrium radiation model incorporated in the program has been refined to include the effects of the geometry of the radiating flow field. Experiments were conducted, using a newly developed annular radiometer, which showed the total radiation incident on the walls of the tube to be much higher than predicted. It is concluded that the discrepancy earlier reported was due to a 50 per cent underprediction of the radiative heat transfer. Non-equilibrium radiation appears to be the cause of this behavior.

Several rocket pay loads designed for coordinated auroral measurements have included 1.27-μ radiometers to monitor the emission from the infrared atmospheric system of molecular oxygen. The rockets were flown under a variety of auroral conditions. Profiles of O2(¹Δg) were determined, based on the assumption that the 1.27-μ radiation came from this species. The resulting profiles show a layer at about 90 km. In some cases the measured emission was independent of viewing direction, whereas in others a definite horizontal asymmetry was observed. This asymmetry is attributed to auroral enhancement of the O2(¹Δg) species. Under these conditions an appreciable portion of the enhanced radiation is seen to come from altitudes above 90 km.

We have described an instrument intended to measure the atmospheric transmission through the windows between 300 and 3000 μm. The radiometer operates automatically, scanning the sky in steps of 0.7° from the horizon to the zenith, with the time constant as selected by the operator. The spectral distribution of the radiation is measured using a Michelson interferometer with an optical path difference of ± 10 cm. Using a 77°K reference blackbody, the atmospheric transmission can be measured with an accuracy better than 1 per cent. Some preliminary results are described, obtained at the Alpine station of Testa Grigia (3500 m above sea level).

A filter‐wheel solar radiometer has been developed for monitoring the atmospheric optical depth at multiple narrow‐wavelength intervals in the visible and near ir regions of the spectrum. Measurements of the direct solar radiations are converted to a digital format and stored in punched tape for eventual analysis by a computer. During stable clear weather condition, the instrument is capable of providing monochromatic optical depths to an estimated rms accuracy of 0.005.

The Nimbus 4 infrared interferometer spectrometer (IRIS) measured the thermal emission of the earth's atmosphere and surface from 400-1600/cm with an apodized spectral resolution of 2.8/cm. A comparison of theoretical radiances, computed from in-situ measurements and using a direct integration slant path atmospheric transmittance model, with the observed IRIS radiances has been made to verify the radiometeric and spectral performance of the instrument and to assess the accuracy of the atmospheric transmittances. The radiance comparison has indicated a relatively constant difference of less than 5% in the water vapor continuum in the 425-550/cm and 750-1200/cm atmospheric window regions while in the 667/cm CO2 band the difference was 5-10%. The absolute accuracy was found to be approximately 5-10% for each of the parameters; measured radiances, in-situ measurements, and the atmospheric transmittances, thus it is not possible to uniquely specify the degree of error arising from each parameter in the total resultant difference.

Nimbus 4 data (11.5-micron) channel and ATS 3 digitized data were analyzed for three days during April and May 1970. Cloud-top temperature, as measured by the 11.5-micron channel of the satellite radiometer, shows a close negative correlation with cloud brightness measured by the ATS 3 satellite. This is especially true in well-developed cumulonimbus clouds. An estimate of cloud heights corresponding to cloud-top temperature was obtained by using radiosonde data and radar images, and the relationships between the cloud thickness and brightness counts were derived for the cumulonimbus clouds.

The ability of a 3.3-mm radiometer to produce thermal images with a 10 arc-minutes resolution on a real-time display has been proved. The influence of the terrain and of the atmosphere on a picture taken from a ground-based antenna has been investigated. The range of zenith sky noise temperatures measured (40–240 degrees K) is so large that a well recognizable object at low sky noise temperature (object on a natural terrain) may disappear completely for a heavy cloud cover. It is shown that the uniquely high angular resolution of this microwave radiometer permits the display of thermograms which approach the visual impression of optical images even under Fresnel conditions.

Two different blood-gas analyzers were tested to determine the effects on blood pH measurement of changing the reference bridge solution from saturated KCl to normal saline (0.16 mol of NaCl per liter). This change, which necessitated the preparation of modified buffers equimolal in NaCl with respect to blood, virtually eliminated salt depletion of the bridge solution and improved the stability of the liquid-junction potential between the bridge solution and the sample. The instruments we used were the Corning 165 pH Blood Gas Analyzer and the Radiometer E5021 pH Electrode with PHM72 Acid Base Analyzer. Comparison of results on clinical blood samples indicates that performance with the modified bufferbridge system is the same as that obtained with the conventional scheme. Analytical performances of the Corning and Radiometer instruments for PO2 and PCO2, as well as for pH, were comparable.

The construction of 10, 3 and 1 mb contour charts using thicknesses derived from Nimbus 4 selective chopper radiometer (SCR) measurements is described. Examples of such charts during the 1972 stratospheric warming period are given. Heights and deduced gradient winds obtained from these charts were compared with radio-sonde and rocket observations. At 10 mb the average heights using satellite measurements exceeded those from radio-sondes by 5 dam in a ‘quiet’ period and by 14 dam in the warming period, the greatest difference occurring in the area of warming. Rocket data showed the average height difference increased upwards to some 40 dam at 1 mb. Consideration of derived gradient winds supported the impression that the shape of contours is better than the spacing. Though there is evidence of increased error on the occasion of major warmings it is concluded that the method described produces realistic charts.

A computer program is developed which predicts the vertical distribution of an absorbing species in an isotropically-scattering, finite planetary atmosphere from measurements of the upwelling band radiance determined by a vertically traversing 2-channel radiometer. Comparison is made with experiment.

A radiometer for the remote measurement of sea surface temperature is described. Two requirements are necessary for the attainment of an absolute accuracy of 1 or 2 K in molecular temperature. Although the first is inappropriate for discussion here, it is clear that corrections must be developed to account for perturbations caused by surface effects (roughness, foaming, and salinity changes) and for atmospheric effects (absorption and scattering). The second requirement, namely, the development of an instrument capable not only of high relative accuracy (i.e., resolution) but also of high absolute precision, is the subject of this paper. The concepts underlying the design of an instrument capable of an absolute accuracy of a few tenths degrees Kelvin in the measurement of brightness temperature at S band are described. The role of the antenna is discussed and the importance of high ohmic and beam efficiencies is stressed. The hardware itself is fully described, along with an outline on the design of a unique cryogenically cooled termination used to calibrate the whole radiometer, including antenna. Finally, some test results are presented that show that the design goals for the instrument have been closely approached.

Noise measurements in the frequency regions 5-200 HZ and 5.2 x 10/sup -4/ -8.3 x 10/sup -3/ Hz have been performed in the wavelength region between 300 and 3000 mu m from the high altitude observatory of Tests Grigia, Italy (3.500 m). In the high frequency region a specially designed Ge bolometer operating in background-limited-infrared-photoconductor conditions matched to a 1.5-m telescope has been used, while at low frequency a radiometer designed for atmospheric transmittance measurements was employed. In both regions no excess noise with respect to the photon noise relative to 300-K blackbody has been detected.

A new radiometer is described for remote sounding of the temperature of the stratosphere and mesosphere (40-90 km) from a satellite platform. In order to select radiation emitted from close to the centres of CO2lines in the 15 pm infrared band, included in the optical system is a cell containing CO2gas whose pressure can be modulated at a frequency of ca. 15 Hz. The parts of the emission lines selected can be altered by two methods known as pressure scanning and Doppler scanning. A two-channel instrument for the Nimbus F satellite is described in detail.

Microwave radiometry has been used for the remote sensing of soil moisture in a series of aircraft flights over an agricultural test area in the vicinity of Phoenix, Arizona, The radiometers covered the wavelength range 0.8–21 cm. Ground truth in the form of gravimetric measurements of the soil moisture in the top 15 cm were obtained for 200 fields at this site. The results indicate that it is possible to monitor soil moisture variations with airborne radiometers. The emission is a function of the radiometer wavelength and the distribution of the moisture in the soil. At a wavelength of 1.55 cm there is little or no variation in the emission for soil moisture values below 10 or 15% moisture content by weight. Above this value there is a linear decrease in the emission with a slope of approximately 3°K for each percentage point increase in soil moisture. On the other hand, the emission was observed to be a linear function of soil moisture over the range 0–35% at a wavelength of 21 cm. Results of calculations using a layered model are presented that indicate the importance of the surface moisture in determining the emission from the soil.

A method for developing and constructing a cloud cover indicator system is described. The method involves pointing an IR radiometer vertically downward to a movable mirror and measuring the reflected sky radiation by comparing the difference in thermal radiance between clouds and the sky. To determine cloud cover it is only important to have a threshold value for the clear sky. A value for the coverage is produced by a sunning system summation of all signal lengths of one cycle.

The Nimbus 3 and 4 Iris spectral data in the 11- to 13-μm water vapor window region are analyzed to determine the sea surface temperature (SST). The high spectral resolution data of Iris are averaged over approximately 1-μm-wide intervals to simulate channels of a radiometer to measure the SST. In the present exploratory study, three such channels in the 775- to 960-cm−1 (12.9–10.5 μm) region are utilized to measure the SST over cloud-free oceans. However, two of these channels are sufficient in routine SST determination. The differential absorption properties of water vapor in the two channels enable one to determine the water vapor absorption correction without detailed knowledge of the vertical profiles of temperature and water vapor. The feasibility of determining the SST is demonstrated globally with Nimbus 3 data, where cloud-free areas can be selected with the help of albedo data from the medium resolution infrared radiometer experiment on board the same satellite. The SST derived from this technique agrees with the measurements made by ships to about 1°C.

Infra-red radiometry from an earth satellite is becoming an important technique for the determination of the three-dimensional temperature structure of the atmosphere on a global scale. In this paper a quantitative expression for the information content of the data from a temperature sounding radiometer is derived. A simple model for the 15 μm CO2 absorption band is used to find radiometer configurations which give maximum information. The spectral bandwidths corresponding to these optimum configurations are considerably broader than those specified in the past for radiometers of this type. The technique of selective chopping in which the radiometer contains absorbing cells filled with CO2 is shown to make a significant increase in the information content.

Meterological measurements from a satellite in near-polar orbit cover the entire globe twice per day, providing adequate data for the first time over the poles and oceans. The selective chopper radiometer on Nimbus 4, launched in April 1970, has monitored the three-dimensional atmospheric temperature field continuously for over two years. In this paper we examine the data for the one-year period June 1970 to May 1971. A spectral analysis of the satellite data in time is shown to be equivalent to an analysis of the temperature pattern in both longitude and time. Analyses of the stratospheric temperatures for the four latitudes 60 degrees N, 20 degrees N, 20 degrees S and 60 degrees S demonstrate the presence of both static and travelling waves. The variation of the amplitudes and phases of these waves with latitude, height and season are described. Strong wave activity occurred in the polar regions during winter and spring seasons, the energy being predominantly in the first three wavenumbers.

The thermal emission of the lunar surface has been mapped by an infrared scanner from lunar orbit. Samples from approximately 250,000 scans reveal the full range of lunar temperatures from 80 to 400 K. The temperature resolution was 1 K with about plus or minus 2 K absolute precision. Spatial resolution was approximately 2 km over most of the horizon-to-horizon scan. The total mapped area amounted to approximately 30% of the lunar surface. The data currently available confirms the large population of nighttime thermal anomalies in western Oceanus Procellarum predicted by earth-based observations. Most of these 'hot spots' are associated with fresh impact features or boulder fields. Also seen in the data are 'cold spots' where the local nighttime temperature is depressed relative to the general soil background. Such regions exhibiting low surface conductivity are inferred to be relatively young, nonimpact features.

A hot-film anemometer was used in a wind flume to measure the size and number of water droplets over the air-water interface. Experiments were conducted both with and without mechanically generated waves and each with both freshwater and saltwater. The effects of wind speed and wave height on the vertical distribution of spray were investigated. The mechanism of spray generation was explored. The results of this study indicate that the vertical distribution of the total horizontal flux of droplets can be expressed by a logarithmic distribution. The drop size distribution (drop size spectrum) at a fixed elevation can be described by a negative power law of drop diameter. The droplet production mechanism by bursting bubbles suggested by Blanchard (1963) is found to account for only a portion of the total production. The effect of spray on the remote sensing of the air-sea interface is evaluated. The spray is found to affect strongly the measurements obtained from a radiometer.

Extant techniques for remotely sensing the earth with instruments operating at microwave frequencies are surveyed. Microwave sensors can provide day-night operation and almost an all-weather capability due to higher transmission through clouds at microwave than at visible or infrared wavelengths. Passive (radiometers), active (radars, altimeters, and scatterometers), and composite (passive-active) microwave sensors are in use or planned for such diverse applications as measuring ocean surface dynamics, Ocean salinity, soft moisture content, atmospheric temperature and atmospheric constituents; detecting sea ice, oil slicks, and storm cells; and identifying agricultural crops. These measurements have been taken with sensors located in towers, aircraft, and most recently satellites.

Two years of infrared data received by the uppermost channel of the selective chopper radiometer, flown on Nimbus 4, are used for a description of the main features of the temperature distribution in the upper stratosphere, with emphasis on differences between the hemispheres. In the upper stratosphere the southern summer is warmer, and the early southern winter colder at all latitudes than the corresponding northern seasons. The largest differences, however, are found in late winter and spring, when the Antarctic is about 20°K warmer than the Arctic, whereas the middle southern latitudes remain colder than the northern. The transition from winter to summer has already started over Antarctica in early July, but a late winter cooling in high northern latitudes, caused by dynamic processes and typical of the northern winter, delays the transition to a summer pattern for about 2 months. The results are also compared with the hemispheric differences in the lower stratosphere.

During 1970 and 1971 the characteristics of a diversity satellite-to-ground communication link were measured using the ATS-5 15.3 GHz downlink. These data were gathered at two ground receiving terminals spaced 4 km apart during 1970 and 8 km apart during 1971 in the vicinity of Columbus, Ohio. These data have been subsequently analyzed to determine the improvement in link performance resulting from the use of space diversity. The results of this analysis have shown that substantial improvements in link performance may be gained through the use of space diversity on satellite-to-ground paths. For example, the durations of fades having depths exceeding 10 dB were reduced by more than two orders of magnitude for both the 4 and 8 km site separation distances.

This work investigates the performance of an all-digital, total-power radiometer (TPR), consisting of RF, mixer, and IF stages followed by an analog-to-digital converter (ADC). Square-law detection and smoothing is performed in a digital computer. A figure of merit, the degradation factor, is defined which compares the digital TPR with an ideal analog TPR. Exact results are obtained which include the effects of saturation, finite step size, and finite sampling rate of the ADC. A good approximation is developed which compares favorably with the exact results under certain conditions. The use of a general digital filter for smoothing is considered. A new parameter, the ?equivalent summation number?, is shown to be analogous to the equivalent integration time of an analog TPR.

A theoretical analysis of high spectral resolution (

Recent high-altitude aircraft, balloon and spacecraft measurements of the extraterrestrial solar irradiances indicate that the earlier integral wavelength value was too high and that the spectral data derived from ground-based techniques were uncertain. Standard values are proposed here with a summary of the supporting evidence.

The output of a radiometer passing over a field of varying emittance or reflectance will not, in general, provide a faithful reproduction of the variations. The space-weighted averaging effect of the radiometer's hemispherical view plus the distortion produced by the first-order response of the radiometer sensor will result in low-pass filtering of the data. By means of a simplified model of the moving radiometer system, this paper provides guidelines for the interpretation of information from such systems. Faithful reproduction requires instruments with a fast time constant, operating close to the surface with a relatively slow speed of translation.

Inversion of satellite radiometer measurements to yield values of atmospheric parameters is expected to be an important source of data within the next few years. A review of inversion methods, based in part on a recent workshop, is presented to outline their present status. General considerations indicate that fine structure will not be resolved, and that the number of parameters determined may be less than the number of measurements. Using infrared data, temperature profiles appear to be inferable with an accuracy of about ±3K, and water vapor distributions may be obtained, over clear skies or broken cloud. Microwave measurements appear to allow temperature determinations with similar accuracy which are less affected by underlying cloud. Water vapor and cloud liquid water content can also be determined, although there are engineering problems. Inversion of visible and ultraviolet data is not as far advanced, but may yield ozone distributions, cloud top heights and information on aerosols. A few of the present problem areas are mentioned.

An interference modulation technique for microwave radiometry is described. Use of the technique is considered for the development of a radiometer for tuning over a wide range of frequencies, a radiometric device for determining the absolute sensitivity of detectors over a wide range of frequencies, and a means for determining the power level of coherent sources as a function of frequency. A device using this technique does not require the use of a coherent source, and the technique is applicable to wavelengths well into the low millimeter region. A tunable radiometer using interference modulation has been operated as a measurements system within the 50-90 Gc region. Successful performance required the use of a sensitive detector which consisted of a barretter operated in an evacuated atmosphere. A noise source having known temperature was used as the source of microwaves for determining the sensitivity of detectors as a function of frequency. It has been found that the sensitivity of barretters is greatly improved by a reduction in air pressure and that, when evacuated, a commercially available barretter will provide a sensitivity of approximately 6 x 10/sup -11/ watts for an audio bandwidth of one cycle per second. The technique discussed provides the opportunity for developing a calibrated power meter for millimicrowatt levels from coherent sources.

In order to test the design and functioning of a selective chopper radiometer for remote sounding of atmospheric temperature, a balloon-borne radiometer has been built and flown. Temperatures measured with radiometers employing techniques of ( a ) selective absorption, ( b ) selective chopping, compared satisfactorily with temperatures predicted from radiosonde information.

Measurements of the electron cyclotron radiation emitted from the plasma of the Alice system were made using a synchronous detection microwave radiometer in the range of 10.2 - 11.6 GHz. Both sidebands were used to samle radiation from two nested closed shells within the plasma. For a tenuous plasma this radiation is proportional to the product of the electron density and the electron temperature. Since measurements of the plasma density were available from other detectors, relative values of the electron temperature were obtained using the measured radiation intensity.

We measured penetration of solar radiation into snow at various times of the year with a spectral radiometer. We found that light absorption obeys a y = axn law where n varies from 0.71 to 2.10. The absorption coefficient n decreases with increasing snow density. The 1% of surface value of total energy occurs at a snow depth of approximately 18 cm in winter, increasing to a maximum of 110 cm in late summer when snow density is near its maximum. Penetration of 0.1% of the surface radiation is shown to coincide with the approximate date and depth of snow pack for the first spring bloom of snow algae, implying that increasing light penetration may initiate germination of overwintering stages.

Measurements were made from aircraft of the 1.55-cm microwave emission from the North Sea and North Atlantic at surface wind speeds ranging from less than 5 to 25 m sec−1. Brightness temperatures in the nadir direction increased almost linearly with wind speed from 7 to 25 m sec−1 at a rate of about 1.2C (m sec−1)−1. At 70° from nadir the rate was 1.8C (m sec−1)−1. This increase was directly proportional to the occurrence of white water on the sea surface. At wind speeds

Anisotropic solar reflectance over white sand, snow and stratus clouds using Nimbus F-3 radiometer and silicon cell pyranometer on Piper Twin Comanche

The blackbody temperature and the albedo of a planet, and the variation of both parameters with latitude, longitude, and time, are of great value in understanding the climatic and meteorological conditions of the planet. An unchopped radiometer with a wide but restricted field of view is capable of such temperature and albedo measurements. Coated thermistors mounted in highly reflective cones serve as detectors. Their performance as sensor elements is analyzed in detail herein to prove the feasibility of the measurement. The simplicity of the instrumentation and the low information bandwidth required make the experiment equally attractive for earth satellites and space probes.

The method consists of the application of the Crookes and Osborne Reynolds radiometers to the measurement of the R.M.S. values of electric currents. Two types of apparatus are descirbed. In the first of these the heat generated by the passage of the current through a nichrome resistance causes the deflection of a light mica vane attached to the extremity of a suspended beam. In the second type the deflection of a fine fibre is employed. Tables and curves are given connecting the indications of the instruments with the current and with the degree of evacuation.

The equation for the molecular radiometric force and moment on a body with convex surface enclosed by an arbitrary closed system in the Knudsen regime has been presented based on the revised theory of thermal transpiration established recently by Wu. Two exact solutions of the molecular vane-radiometers in a cylindrical tube and rectangular duct have been obtained in closed forms and calculated through numerical computation. These solutions reduce to the classical theory developed by Knudsen in the limit of infinitely large containers. (Author)

While working at another subject I evolved a very simple piece of apparatus which on trial was found to be very sensitive to the penetrating rays of radioactive substances, so I have recently diverted my work from its original direction to study and improve this piece of apparatus. The principle of the action of the instrument is not new, as it depends on the fact discovered by Professor C. T. R. Wilson, that ions in air supersaturated with water vapour become centres of condensation when the supersaturation is sufficiently great.

The principles of operation of broad-band microwave radiometers are discussed. Formulas are given for the performance of various receiver configurations, and the effects of variations in stability of gain, noise figure, and reference signal are discussed. A range equation is formulated showing the interrelationships among the various system parameters of a typical airborne mapping radiometer. Figures of merit are defined and discussed for the targets, antenna, receiver, and flight conditions.

Radiation from the planets, Venus, Mars, and Jupiter, has been measured at a wavelength of 3.15 cm using the Naval Research Laboratory 50-foot reflector and a narrow-band radiometer. The apparent blackbody temperatures for Mars and Jupiter derived from the radio measurements agree reasonably well with the results of infrared radiometric measurements. For the case of Venus, the apparent blackbody temperature derived from the 3.15-cm measurements is about a factor of two higher than the value derived from the infrared measurements. A measurement of the radiation from Venus at 9.4-cm wavelength was made using the same antenna. The apparent blackbody temperature derived from this measurement agreed well with the value derived from the 3.15-cm measurement, but the accuracy of the 9.4-cm result was low because of the small flux density of radiation and the small number of observations.

Summary. Radiative divergence in the atmosphere was measured during 1964 at Point Barrow, Alaska, at a location 2.5 km inland from the Arctic Ocean. C. S. I. R. O.-radiometers were used in the two observational techniques employed: 1) A radiometer was mounted on the vertically traveling boom of a specially designed tower, measurements being taken at 1, 2, 3, 4 and 5 m, and 2) A gimbalized radiometer was suspended from a moored "kytoon", measurements being taken at levels up to 250 m. Tower data comprise approximately 80 hours of observations over snowcovered tundra, in the temperature range of --4 to --300 C. Kytoon data comprise observations of six flights of 2 to 3 hours duration, all but one being over grassy tundra, in the temperature range of --5 to 5 o C. The sign of the measured divergence was usually negative, and the maximum convergences occurred during clear, calm weather, and in the lowest layers. The absolute magnitude of calculated divergences (FuNK'S method) was consistently less than that of the measured values. More accurate temperature and humidity measurements are necessary to explain the poor agreement of calculated and measured radiative divergences. Zusammenfassung. Es wird fiber Messungen der Strahlungsstromdivergenz an einer Station 2,5 km landeinw/irts yon der Kfiste des Arktischen Ozeans in der N/ihe von Point Barrow (Alaska) berichtet. C.S.I.R.O.-Strah lungsbilanzmesser wurden in zweierlei Weise verwendet: 1. Der Bilanzmesser wurde an einem speziell konstruierten Turin auf einem vertikal beweglichen Arm montiert und erm6glichte Messungen der Strahlungsbilanz in 1, 2, 3, 4 und 5 m H6he fiber dem Boden. 2. Der Bilanzmesser wurde in kardanischer Aufh~ingung an einem

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.