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Kirby J. Hanson

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KIRBY J. HANSON

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Solar and terrestrial radiation measurements that were obtained at Amundsen-Scott (South Pole) Station and on Ice Island (Bravo) T–3 are presented for representative summer and winter months. Of the South Polar net radiation loss during April 1958, approximately 20 percent of the energy came from the snow and 80 percent from the air. The actual atmospheric cooling rate during that period was only about 1/6 of the suggested radiative cooling rate. The annual net radiation at various places in Antarctica is presented. During 1958, the South Polar atmosphere transmitted about 73 percent of the annual extraterrestrial radiation, while at T–3 the Arctic atmosphere transmitted about 56 percent. The albedo of melting sea ice is discussed. Measurements on T–3 during July 1958 indicate that the net radiation is positive on both clear and overcast days but greatest on overcast days. Refreezing of the surface with clear skies, as observed by Untersteiner and Badgley, is discussed.

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Kirby J. Hanson

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The spectral transmission properties of glass, polyester film, polyvinyl-fluoride film, polystyrene film and polyethylene film are presented, based on laboratory determined spectrograms and field measurements of atmospheric infrared radiation.

Glass, polyvinyl-fluoride film and polystyrene film transmit about 0.88 of incident visible light; polyester and polyethylene transmit 0.81 and 0.73, respectively. For ultraviolet radiation, transmission values differ markedly between films.

The amount of protection provided by various plant covering materials against nocturnal net radiation (Rn) loss from plants has been determined and is expressed as a protection index (PI) in per cent by:

             PI = 102 · [1 − (R n(with cover)/R n(no cover))]

where PI ranges from zero (no protection) to 100 per cent (complete protection). Based on field measurements, PI values have been determined as follows: 1) window glass–93 per cent; 2) polyvinyl-fluoride film-90 per cent; 3) polyester film-87 per cent; 4) polystyrene film-63 per cent; and 5) polyethylene film-26 per cent.

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KIRBY J. HANSON and HERBERT J. VIEBROCK

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On Septemer 16, 1961, Eppley pyranometers mounted in a P2V–7 aircraft were used to measure the incoming and outgoing solar radiation fluxes at 7,500, 9,500 and 25,000 ft. along flight paths between Atlantic City, N.J., and Erie, Pa. Albedo values are determined from this information for the flight level. Simultaneous photographs and radiation values were obtained on the 25,000-ft. flight. The albedo for the high-level flight varied from 0.158 for no undereast to 0.538 for a complete altocumulus undereast. Two selected observations at 1722 GMT and 1737 GMT are further discussed. A solar radiation budget is prepared for the 1737 GMT measurement using the high-level flight data and ground data from Thornthwaite Laboratories near Elmer, N.J.

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Verner E. Suomi, Kirby J. Hanson, and Robert J. Parent

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This paper reports on a digital measurement (“chirp”) system which has application for a wide range of meteorological and earth satellite measurements.

The system employs a simple concept in which a voltage pulse, proportional to a sensor voltage, is used to generate a burst of pulses from a voltage controlled oscillator (VCO). A count of the high frequency oscillations which make up the “chirp” provides the digital measurement. The system is adapted to multiple sensor use with a multiplexer.

The system has the advantage in that one has the option of selecting an ac amplifier for low level signals in conjunction with a variety of multiplexers and VCO for the desired measurement. One particular combination of multiplexer and VCO was used to demonstrate its use as a digital radiosonde.

A flight test of the digital radiosonde was obtained. Results clearly show fine structural detail in the temperature profile without any need for subjective interpretation by the operator. Numerous isothermal and inversion layers less than 100 m in thickness were observed.

The digital radiosonde used conventional (U.S. Weather Bureau) temperature and humidity sensors. Temperature resolution is about 0.1C and relative humidity is about 0.1 per cent. The system resolution is 0.1 per cent.

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Kirby J. Hanson, James T. Peterson, Jerome Namias, Robert Born, and C. S. Wong

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The study presents an analysis of atmospheric CO2 measurements at Ocean Weather Station P (50°N, 145°W) and sea surface temperatures over the North Pacific for the period 1974–78. The results show that during 1976 and 1977 sea surface temperatures over the Northwest Pacific were significantly below normal and, coincidentally, atmospheric CO2 levels at Station P also were lower than expected. This indirect evidence does not prove but suggests that the Northwest Pacific (40–45°N) may have been a major sink for atmospheric CO2 during 1976 and 1977. However, a specific mechanism for this sink is not established. Broecker et al. (1979) presented direct evidence of a C02 sink at 40°N, 180°W in late 1973 and early 1974. In the future direct observations of pertinent parameters obtained at appropriate times could establish the significance of the North Pacific as a sink for atmospheric C02 and lead to studies of the mechanism for such a sink.

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KIRBY J. HANSON, THOMAS H. VONDER HAAR, and VERNER E. SUOMI

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This study describes a method for determining the reflection of sunlight to space and absorption by the earth and atmosphere, using low-resolution radiometer data from earth satellites. The method has been used with TIROS IV data together with radiation measurements at the ground to determine the reflection and absorption of sunlight over the United States during the spring of 1962.

The results indicate that for this region and time, 40 percent of the incident sunlight at the top of the atmosphere was reflected to space, 13 percent was absorbed by the atmosphere and clouds, and the remaining 47 percent was absorbed at the earth's surface. Atmospheric absorption of sunlight varied from over 20 percent in the moist air in southeastern United States to less than 10 percent over much of the dry mountainous west and northern plains.

When atmospheric absorption values determined from this study are compared with earlier studies of absorption in a cloudless atmosphere, there is good agreement at low values of atmospheric water vapor; however, the present study gives significantly higher absorption at high values of water vapor.

Based on this study, an empirical relationship is determined for fractional absorption of sunlight in an atmosphere with clouds as a function of optical pathlength of water vapor: qa=0.096+0.045(u*)½logeu*. The fractional absorption of sunlight, qa, is the fraction of the total amount incident at the top of the atmosphere. The optical pathlength, u*, is given in cm.: u*=u.sec ζ. Here, u is total precipitable water in a vertical column, given in cm., and ζ is the solar zenith angle.

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