﻿618 
  F. 
  W. 
  Very 
  — 
  Solar 
  Radiation. 
  

  

  nomenon 
  of 
  " 
  inversion 
  "* 
  discovered 
  by 
  Bigelow, 
  whicli 
  com- 
  

   plicates 
  the 
  meteorological 
  problem 
  still 
  more. 
  Into 
  this 
  prob- 
  

   lem 
  enter 
  : 
  (a) 
  the 
  solar 
  constant 
  whose 
  estimation 
  can 
  not 
  be 
  

   made 
  without 
  hypotheses, 
  and 
  whose 
  variation 
  remains 
  uncer- 
  

   tain 
  ; 
  (b) 
  changes 
  in 
  the 
  solar 
  spectrum 
  which 
  synchronize 
  

   with 
  the 
  sun-spot 
  cycle 
  and 
  show 
  an 
  alteration 
  in 
  at 
  least 
  the 
  

   quality 
  of 
  the 
  solar 
  radiation 
  ; 
  (c) 
  variations 
  in 
  the 
  solar 
  

   corona 
  in 
  the 
  11-year 
  period, 
  which 
  may 
  affect 
  the 
  earth 
  by 
  a 
  

   solar 
  emission 
  of 
  kathode 
  rays 
  or 
  by 
  some 
  other 
  process 
  differ- 
  

   ent 
  from 
  the 
  ordinary 
  radiation 
  ; 
  (d) 
  climatic 
  cycles 
  which 
  are 
  

   of 
  opposite 
  nature 
  in 
  different 
  parts 
  of 
  the 
  earth 
  and 
  of 
  several 
  

   periods 
  (including 
  the 
  11-year 
  period). 
  No 
  climatic 
  theory 
  can 
  

   be 
  considered 
  complete 
  which 
  does 
  not 
  consistently 
  harmonize 
  

   these 
  details. 
  

  

  Many 
  attempts 
  have 
  been 
  made 
  to 
  derive 
  formulas 
  connect- 
  

   ing 
  the 
  absorption 
  of 
  solar 
  radiation 
  with 
  the 
  aqueous 
  vapor 
  of 
  

   the 
  atmosphere, 
  but 
  with 
  snch 
  small 
  success 
  that 
  the 
  effort 
  has 
  

   been 
  generally 
  abandoned. 
  Nevertheless, 
  the 
  total 
  omission 
  of 
  

   a 
  vapor 
  factor 
  in 
  the 
  computation 
  of 
  the 
  solar 
  constant 
  must 
  

   be 
  remedied, 
  for 
  it 
  is 
  certain 
  that 
  atmospheric 
  moisture 
  has 
  a 
  

   depleting 
  action 
  on 
  the 
  incoming 
  as 
  well 
  as 
  on 
  the 
  outgoing 
  

   radiation. 
  This 
  may 
  be 
  known 
  because 
  (1) 
  the 
  form 
  of 
  the 
  

   diurnal 
  curve 
  of 
  solar 
  radiation 
  changes 
  from 
  a 
  symmetrical 
  

   shape 
  with 
  relative 
  freedom 
  from 
  fluctuations 
  in 
  cold, 
  dry 
  

   winter 
  weather, 
  to 
  a 
  flattened 
  and 
  unsymmetrical 
  shape 
  beset 
  

   with 
  sinuosities 
  in 
  summer. 
  (2) 
  The 
  total 
  solar 
  radiation 
  

   through 
  identical 
  masses 
  of 
  air 
  is 
  smaller 
  in 
  moist, 
  summer 
  

   weather 
  than 
  in 
  cold 
  and 
  dry 
  winter 
  weather, 
  and 
  this 
  diminu- 
  

   tion 
  of 
  intensity 
  in 
  summer 
  is 
  associated 
  not 
  only 
  with 
  increase 
  

   of 
  the 
  aqueous 
  absorption-bands 
  in 
  the 
  infra-red 
  spectrum, 
  but 
  

   with 
  an 
  increased 
  depletion 
  of 
  the 
  shorter 
  waves 
  of 
  the 
  visible 
  

   and 
  ultra-violet 
  parts 
  of 
  the 
  spectrum. 
  (3) 
  As 
  a 
  result 
  of 
  the 
  

   last-named 
  depletion, 
  red 
  sunsets 
  are 
  characteristic 
  of 
  the 
  

   tropics 
  and 
  summer, 
  or 
  of 
  the 
  approach 
  of 
  hot 
  waves 
  and 
  

   increased 
  atmospheric 
  moisture, 
  while 
  the 
  fading 
  of 
  the 
  dawn 
  

   and 
  sunset 
  tints 
  implies 
  a 
  widely 
  prevalent 
  dryness 
  in 
  the 
  

   atmosphere, 
  associated 
  with 
  cold 
  because 
  the 
  terrestrial 
  radia- 
  

   tion 
  also 
  escapes 
  through 
  the 
  atmosphere 
  more 
  freely 
  at 
  such 
  

   times. 
  (4) 
  If 
  we 
  compare 
  the 
  solar 
  radiation 
  with 
  equal 
  air 
  

   masses 
  we 
  shall 
  find 
  that 
  (a) 
  in 
  the 
  morning 
  and 
  afternoon 
  of 
  

   the 
  same 
  day, 
  the 
  afternoon 
  measurement 
  will 
  usually 
  be 
  the 
  

   smaller 
  because, 
  in 
  general, 
  evaporation 
  of 
  surface 
  moisture 
  

   has 
  increased 
  the 
  vapor 
  content 
  of 
  the 
  air 
  in 
  the 
  afternoon, 
  and 
  

   (b) 
  that 
  of 
  simultaneous 
  measures 
  at 
  different 
  altitudes 
  on 
  a 
  

  

  * 
  Inversion 
  of 
  temperature 
  consists 
  not 
  merely 
  in 
  a 
  general 
  synchronous 
  

   opposition 
  of 
  thermal 
  changes 
  in 
  different 
  parts 
  of 
  the 
  earth, 
  but 
  includes 
  

   minor 
  details 
  in 
  the 
  distribution 
  and 
  amplitude 
  of 
  the 
  thermal 
  fluctuations. 
  

  

  