An estimate of the solar radiation incident at the top of Pluto's atmosphere

• Published in: Bulletin de la Classe des sciences
• Main Author: Van Hemelrijck, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Bruxelles : Académie Royale de Belgique 1982
• Subjects: envir; geo; South Pole; North Pole; South pole
• Online Access: https://doi.org/10.3406/barb.1982.63579; https://www.persee.fr/doc/barb_0001-4141_1982_num_68_1_63579

Calculations of the daily solar radiation at the top of the atmosphere of Pluto are presented in a series of figures giving the seasonal and latitudinal variation for three fixed values of the obliquity (e = 60, 75 and 90°). It is shown that the maximum daily insolation is incident at the poles at solar longitudes near 110 and 250° with values ranging from 11 to 13 cal cm-2 (day)-1 (North pole) and from 13.5 to 15.5 cal cm-2 (day) -1 (South pole). At the equator, maxima of the order of 6 cal cm-2 (day)-1 are found around autumnal equinox. The solar longitude intervals where the polar solar energy exceeds the equatorial one extend from 20 to 160° and from 200 to 340° respectively. The steady increase of the polar insolation with increasing obliquity is accompanied by a corresponding loss of the equatorial solar radiation. The large eccentricity of Pluto produces significant north-south seasonal asymmetries in the daily insolation, whereas the change in the obliquity causes mainly a global latitudinal redistribution, although the general pattern of the contour maps illustrating the variability of the daily solar radiation with lati¬ tude and season is nearly similar. It is also interesting to note that in the equatorial region summer and winter are, roughly speaking, repeated twice a year. In addition, we also numerically studied the latitudinal variation of the mean daily insolation. It is found that in summer if s varies from 60 to 90°, the mean summer insolation increases by about 15 % at the poles, remains approximately constant at a latitude of 20°, but decreases at the equator also by approximately 15 %. In winter, an increase of the obliquity yields a mean daily insolation which is reduced at all latitudes (maximally by about 20 % near the equator), the influence of e being of decreasing significance at polar region latitudes. As for Uranus, the equator receives less annual average energy than the poles the ratio of both insolations amounts to about 0.9, 0.7 and 0.6 for an obliquity equal to 60, 75 and ...