Scientific papers dedicated to Dr Anders Ångström

Abstract

1. Dr. Anders Ångström, 80 years on February 28, 1968

2. On the causes of climate variations

The problem of causes of climate variations at the present time and in the geological past has been considered. Physical explanation of the regularities of climale variations has been suggested which is based on the general ideas of factors determining the genesis of the Earth's climate.

3. Direct solar radiation and aerosol structure of the atmosphere from balloon measurements in the period of IQSY

The results of the actinometric balloon sounding V. 1962-XI. 66 are used to analyse the irregularity of extinction of the direct solar radiation in the troposphere and stratosphere. The beginning of this period is characterized by the great exlinction (up to 8 %) above the sounding level; later the influence of the "upper" extinction becomes somewhat less but there appears another source of extinction, that is, volcanic dust. The aerosol structure of the atmosphere up to the heights of 30 km and its relationship to the temperature profile are discussed. The solar constant for the period
studies is evaluated.

4. Experiments with automatic interpretation of meteorological forecast charts

A method has been tried for automatic translation of the information contained in prognostic charts into weather parameters such as surface wind, surface temperature and precipitation. The method is described and exemplified. Results from two test periods are presented.

5. Some observations of snow melt

By use of a recording snow melt-meter the hourly amount of melt water has been studied in relation to meteorological factors. In general there is a good agreement between theoretical and observed values. However, during strong isolation deviations have been found which call for further studies. The amount of liquid water in the melting snow is found to be only a few per cent of the mass of the snow layer when there is free drainage whereas in laboratory experiments without free drainage a percentage of 30 % or more can be obtained.

6. The radiation balance of earth-atmosphere system over both polar regions obtained from radiation measurements of the Nimbus II meteorological satellite

Measurements of the outgoing emitted longwave radiation and the reflected solar radiation were obtained for the first time over the entire globe from the Nimbus II metcorological satellite. These data were obtained during the period 16 May-28 July, 1966 and covered the onset and development of the summer and winter seasons in the Northern and Southern hemispheres, respectivcly. Nimbus Il carried a five-channel medium resolution radiometer, two channels of which received longwave radiation and reflected solar radiation in wideband spectral intervals from 5.0 to 30.0 microns and 0.2 to 4.0 microns, respectively. From these "filtered beam" measurements the oulgoing "unfiltered" radiation fluxes were calculated using empirical integration techniques. The method of WARK et al. (1962) was applied in principle to compute the outgoing flux of emitted longwave radiation. The
flux of reflected solar radiation was computed, utilizing empirically derived models of the dependence of the reflection properties of the earth-atmosphere system on the zenith angles of the sun and the measured beam and on the relative azimuth between the two.
The results of the outgoing longwave radiation, the albedo, and the radiation balance of the earth-atmosphere system were obtained as averages for five subperiods, each of a half month's length. As an example, results obtained for the period 1-15 July, 1966 over both polar regions are presented and discussed in the form of maps in this paper.
The albedo over the central Arctic north of 80° N diminished continuously from May to the end of July from 68 % to 50 % due to the melting of ice and snow surfaces. The radiation balance only during the first half of July became slightly positive ( +0.012 cal cm-2 min-1) there. During all other subperiods, it resulted in a net radiation flux toward space.
Over the Antarctic during this season the radiation balance is almost entirely determined by the outgoing longwave radiation flux.
The global albedo for all five subperiods was found lo be about 30 %. This value is considerably less than earlier accepted values ranging between 33 % and 43 %. The radiation balance over the entire globe resulted in a slight energy gain of + 0.002 cal cm-2 cm-1 during the second half of May and a deficit between -0.003 and -0.007 cal cm-2 min-1 during the other four subperiods.

7. Transmission of solar radiation in the spectral region 0.55 to 0.64 μm and the Ångström turbidity coefficient

Some hitherto unpublished measurements of solar radiation in the yellow-orange region of the spectrum, made in 1947/48/49 at Kew Observatory are examined in relation to the extinction by atmospheric aerosol, the Ångström turbidity coefficient, the visibility and the scale height of the aerosol distribution.

8. Studies on the effect of lake regulation on local climate

This is a brief report on the essential results achieved at the investigations which during the past twenty years have been performed by the Swedish Meteorological and Hydrological Institute on the subject mentioned in the heading. The temperature and humidity conditions are discussed. The most outstanding effect is the increase of fog frequency in winter when ice formation is prevented in the river because of increased stream velocily.

9. The temperature of physically well-defined bodies under the influence of various meteorological elements, particularly radiation

A knowledge of the temperature which a body may assume under the influence of solar radiation in air layers near the ground is of major significance in problems of heliotherapy. The attempt has here been made to explore these conditions with the aid of recordings extending over more than a year on solid copper spheres placed 10 cm and 160 cm above the ground. The results show that in the climatic conditions prevailing just south of the Alps very high temperatures may be attained which are of importance
from a physiological viewpoint.

10. Rayonnement (Tiros IV) et pluviosite au Congo1

From charts of daily precipitation, of the daily sum of global radiation and from infrared radiation in the region 8-12 μ (HRIR) measured by satellite TIROS IV, the meteorological evolution over Central Africa during the period 1st to 3rd May, 1962, is analyzed. Table 1 shows that a relalively strong correlation exists between radiation intensity in this range and precipitation. Even between the daily sum of global radiation from sun and sky and precipitation a similar relation exists (Table 2). A radiation chart taken from a satellite and distributed sufficiently fast may greatly facilitate the synoptic information.

11. A modified method to determine the annual precipitation in the Scandinavian mountains

Various methods have been applied earlier to determine the annual precipitation in Swedish mountain areas outgoing from measurements of precipitation and run-off as well as from estimates of evaporation. A modified method is described to map precipitation in the Scandinavian mountains based on a study of the relationship between calculated precipitation on the one hand and height above sea level and distance from the sea on the other. A map showing the annual precipitation is constructed with the aid of the relationship found.

12. Turbidity at Uppsala from 1909 to 1922 from Sjöström's solar radiation measurements1

In the course of investigations on attenuation by dust from violent volcanic eruptions, the blue filter measurements of direct solar radiation at Uppsala by Sjöström from 1908 to 1922 have been evaluated. For about 2,5 years, attenuation by the dust from the Katmai eruption (1912) was well above normal turbidity, while dust from weaker eruptions and from an Indonesian volcano was hardly detectable. Furthermore, the annual and daily courses of normal turbidity at Uppsala are compared with those at Stockholm in later years. There are also indications of an increase of turbidity by industrial activity in the course of the years.