﻿48 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  In 
  the 
  spring, 
  rising 
  temperature 
  produces 
  a 
  modification 
  and 
  

   shifting 
  of 
  pressure 
  systems, 
  the 
  winds 
  decreasing 
  in 
  velocity 
  and 
  

   their 
  direction 
  being 
  more 
  variable 
  than 
  in 
  winter. 
  The 
  frequent 
  

   showers 
  occurring 
  in 
  April 
  and 
  May 
  appear 
  to 
  be 
  due 
  more 
  than 
  

   at 
  any 
  other 
  time 
  to 
  the 
  effect 
  of 
  an 
  admixture 
  of 
  air 
  having 
  

   different 
  temperatures. 
  

  

  In 
  summer 
  the 
  Gulf 
  of 
  Mexico 
  and 
  the 
  Atlantic 
  ocean 
  con- 
  

   tribute 
  large 
  supplies 
  of 
  moisture 
  to 
  northward-moving 
  air 
  cur- 
  

   rents, 
  and, 
  although 
  cyclonic 
  depressions 
  are 
  less 
  frequent 
  than 
  

   at 
  any 
  other 
  season, 
  the 
  rainfall 
  accompanying 
  each 
  storm 
  is 
  

   heavy, 
  and 
  in 
  New 
  York 
  the 
  maximum 
  seasonal 
  precipitation, 
  

   amounting 
  as 
  an 
  average 
  for 
  the 
  whole 
  State 
  to 
  10.96 
  inches, 
  

   occurs 
  in 
  this 
  season. 
  

  

  As 
  regards 
  the 
  fall 
  months, 
  the 
  rainfall 
  of 
  September 
  is 
  usually 
  

   light 
  in 
  the 
  region 
  east 
  of 
  the 
  Great 
  Lakes, 
  while 
  in 
  October 
  the 
  

   maximum 
  general 
  rainfall 
  occurs. 
  As 
  regards 
  meteorological 
  

   conditions, 
  winter 
  may 
  be 
  considered 
  as 
  beginning 
  in 
  November. 
  

   A 
  study 
  of 
  the 
  data 
  shows 
  that 
  there 
  are 
  a 
  number 
  of 
  contend- 
  

   ing 
  forces 
  which 
  are 
  distinctively 
  operative 
  in 
  New 
  York, 
  and 
  

   which 
  by 
  modifying 
  one 
  another 
  tend 
  to 
  produce 
  numerous 
  irregu- 
  

   larities 
  of 
  the 
  rainfall. 
  So 
  irregular 
  indeed 
  is 
  the 
  precipitation 
  

   that 
  frequently 
  places 
  only 
  a 
  short 
  distance 
  apart 
  show 
  wide 
  

   variation. 
  

  

  In 
  a 
  general 
  way 
  it 
  may 
  be 
  said 
  that 
  the 
  amounts 
  of 
  annual 
  

   rainfall 
  in 
  different 
  sections 
  of 
  New 
  York 
  are 
  mainly 
  determined 
  

   by 
  proximity 
  to 
  sources 
  of 
  vapor 
  or 
  to 
  vapor-laden 
  air 
  currents, 
  

   and 
  by 
  the 
  character 
  of 
  the 
  local 
  topography. 
  As 
  regards 
  the 
  

   latter 
  statement, 
  a 
  more 
  definite 
  form 
  would 
  be 
  that 
  under 
  similar 
  

   conditions 
  the 
  precipitation 
  is 
  in 
  some 
  degree 
  proportionate 
  to 
  the 
  

   altitude. 
  This 
  rule, 
  while 
  generally 
  true, 
  does 
  not 
  apply 
  to 
  the 
  

   valley 
  of 
  the 
  Hudson 
  river, 
  where 
  the 
  upper 
  portion, 
  including 
  the 
  

   Champlain 
  valley, 
  receives 
  a 
  somewhat 
  deficient 
  rainfall 
  as 
  com- 
  

   pared 
  with 
  the 
  State 
  as 
  a 
  whole. 
  To 
  the 
  west, 
  the 
  Adirondack 
  

   plateau 
  receives 
  a 
  marked 
  increase 
  of 
  rainfall, 
  while 
  farther 
  north- 
  

   west 
  there 
  is 
  a 
  decrease 
  in 
  the 
  valley 
  of 
  the 
  St 
  Lawrence. 
  This 
  

   is 
  also 
  true 
  of 
  the 
  elevated 
  region 
  in 
  the 
  vicinity 
  of 
  Hemlock 
  lake, 
  

  

  