Bernard Goldberg

Spectral ultraviolet‐B radiation fluxes at the Earth's surface: Long‐term variations at 39°N, 77°W

Precision Measurements of UVB global irradiance in 5-nm-wide spectral bands centered from 290 to 320 nm were made continuously from September 1975 through December 1990. The spectral radiometer was calibrated at roughly monthly intervals. Annual maximum monthly means for total daily radiation, radiation at solar noon, and clear sky radiation at small secants all were observed to be significantly higher during the period from 1983 through 1989. The maximum monthly mean of integrated 295–320 nm total daily radiation in 1986 was 29% above the long-term mean, 47% above the maximum in 1982, and 54% above the mean maxima for 1979–1982. These interannual changes were largest for the shorter wavelengths but were significant for all spectral bands. Interannual variations in clear sky radiation were largest at small secants. For maximum monthly means of integrated 295–320 nm flux, the secant 1.2 maximum in 1989 was 19% above the long-term mean and the average of the maxima during 1983–1989 was 13% above the long-term mean.

A comparison of some simple models used to predict solar irradiance on a horizontal surface

Four simple models for predicting the amount of solar radiation available at any location are compared to show how well they can predict solar insolation on a horizontal surface. The most significant result of these comparisons is that average daily values of yearly insolation can be determined reasonably well by the use of simple models. (SPH)

Variations in the spectral distribution of daylight at various geographical locations on the earth's surface☆

Abstract Three locations, Barrow, Alaska at 71°N, Rockville, Maryland at 39°N and the Pacific end of the Panama Canal at 9°N, are the sites used for solar radiation data comparisons in this paper. Data collected by precision pyranometers over the years 1968–1974 show, with great clarity, that one cannot compute the daily insolation on a horizontal surface with variations of less than 50 per cent from some mean value. The spectral quality of daylight is not the same at all places, nor is the rate of change in the spectral quality the same at all locations. The greatest variations in the spectral quality occur in the peak response region for silicon, 600–800 nm. The blue, 400–500 nm, also shows large variations, but, like the red bands, most of these variations are due to local atmospheric conditions. Of the three sites, Rockville shows the greatest amount of variation from year to year, as well as during the year. Because of the large variability in daily totals at Rockville, it appears that it will be necessary to monitor daily amounts of solar radiation to evaluate the performance of heating and cooling systems for buildings using solar energy in this area. One other trend has also been noted in Rockville: a small but steady decline in the amount of solar energy falling on a horizontal surface. Between 1971 and 1974 the decline in energy was approximately 4.5 per cent.

A model for determining the spectral quality of daylight on a horizontal surface at any geographical location

Abstract Using solar irradiance data gathered over 8 yrs (1968–1976) a very simple model for determining daily and hourly totals of solar irradiance has been derived. The simplified model works extremely well for broad spectral regions, i.e. the total irradiance, the visible (400 nm–700 nm), and the total IR (800 nm–2800 nm). Smaller regions (100 nm bands) are not computed with the same accuracy because of the spectral dependency of such parameters as the albedo, water vapor and ozone. Also, this model does not give good results around sunrise and sunset. The computational accuracy of the model of daily totals and hourly totals on clear days is within ±10% when compared to values obtained from Eppley precision pyranometers. The accuracy for 100 nm bands is considerably less being greater than ±10 per cent on clear days and cloud corrections will increase the errors to ±25 per cent.

THE ACTION SPECTRUM OF DAPHNIA MAGNA (CRUSTACEA) PHOTOTAXIS IN A SIMULATED NATURAL ENVIRONMENT

Abstract— The action spectrum of phototaxis in Daphnia magna (Crustacea) was measured in a chamber which simulated a natural angular distribution of underwater light. A 17% step‐down in irradiance was used to stimulate the phototactic response at all wavelengths and irradiances tested. Peaks in the spectral response curves depended on the fluence rate to which the zooplankton were acclimated. The wavelength of maximum response (Zmax) shifted from yellow‐green at the highest acclimation fluence rate (5.1 × 10−2 Wm−2) to blue‐violet at moderate rates. At low acclimation fluence rates, the blue‐violet maximum was retained and another maximum developed in the red. At the lowest fluence rate (1.6 × 10−5 Wm−2), the blue‐violet and red maxima were lost and another maximum developed in the near ultraviolet. The action spectrum indicates the presence of three, and possibly four, photopigments with Zmax, at ∼405, 440, 570 and 690nm. The 440 and 690nm maxima may belong to the same photopigment; however, this was not tested. Changes in zooplankton swimming speed, caused either by large changes in irradiance or by mechanical stimuli, were accompanied by changes in the strength of the phototactic response to the −17% stimulus at any irradiance level for white and monochromatic light, and indicated the presence of a mechanism connecting swimming speed and photosensitivity.

A laboratory method for studying zooplankton swimming behaviors

A laboratory method is presented for studying zooplankton swimming behaviors such as phototaxis and photokinesis. The method attempts to standardize laboratory conditions and to minimize the effects of several phenomena which modify zooplankton behavior. The role of angular light distribution in zooplankton behavior is discussed, and an apparatus which simulates a natural underwater light environment is described. The procedure minimizes the fluctuations in zooplankton swimming speed and vertical distribution that are caused by large light stimuli, noise, food deprivation, endogenous rhythms, and other factors. The experimental animals were viewed remotely with the aid of a light amplifier and video camera. A mathematical equation and computer program for calculating three-dimensional swimming speeds of zooplankton from video recordings are described in detail.

Instrumentation for the measurement of the variation, quantity and quality of Sun and sky radiation

Abstract Many biological responses, such as reproduction, differentiation and morphological development are regulated by radiant energy in particular wavelengths of the solar spectrum. Biologists are concerned with the influence of the spectral quality of natural daylight on these biological responses. Data, concerning spectral quality of daylight over a sufficient time period, required by biologists are usually not available. The described system will provide the information with sufficient accuracy and precision to discern small but significant changes. To produce such a monitoring system, a standardization program was evolved using the original Smithsonian solar standards and instruments. These were compared to each other and finally to commercial units which were used in the monitoring system. The system was designed so that data would be accurate at 0.01 ly min −1 and could be automated to give high precision readings every 3 min with errors less than 2 per cent.

Solar radiation changes at Mt. St. Katherine after forty years

Abstract Between 1933 and 1937 Dr. Abbot and his co-workers from the Smithsonian Institution made normal incidence measurements atop Mt. St. Katherine in the Sinai. The observations made at that time indicated a very clean atmosphere prevailed on clear days. Measurements made forty years later with newer instruments and one of the original silver disks used by Dr. Abbot indicates a loss of some 10 per cent of the solar energy contained in the direct beam.

A SIMPLIFIED MODEL FOR DETERMINING THE SPECTRAL QUALITY OF DAYLIGHT AND THE AVAILABILITY OF SOLAR ENERGY AT ANY LOCATION1

ABSTRACT Using solar irradiance data gathered over the past eight years (1968-1976) a very simple model for determining daily and hourly totals of solar irradiance has been derived. The simplified model works extremely well for broad spectral regions, i.e., the total irradiance, the visible (400 nm - 700 nm), and the total IR (800 nm to 2800 nm). Smaller regions (100 nm bands) are not computed with the same accuracy because of the spectral dependency of such parameters as the albedo, water vapor and ozone. Also, this model does not give good results around sunrise and sunset. The computational accuracy of the model of daily totals and hourly totals on clear days is within ± 10% when compared to values obtained from Eppley precision pyranometers. The accuracy for 100 nm bands is considerably less being greater than ± 10% on clear days and cloud corrections will increase the errors to ± 25%.

Radiometric Measurements in the UV-B Region of Daylight

The Smithsonian Radiation Biology Laboratory has developed a low level light-monitoring device which can be operated in the natural environment with little maintenance. Such a device has been functioning for over four years at Rockville and for about a year and a half at NASA-Langley in Virginia. The device at Rockville is an original analog version of the integrating digital unit used at Langley. These units are monitoring solar ultraviolet radiation from 280–325 nm in 5 nm bands, using interference filters in pairs. These filters are centered at 285, 290, 300, 305, 310, 315, and 320 nm.