312 



ENVIRONMENTAL CONDITIONS. 



half of our period considerable precipitation occurred. It is to be 

 noted, as is generally the case, that weeks with much precipitation are 

 characterized by low evaporation intensity. 



San Diego, California (fig. 4) : For this station the weekly rates of 

 evaporation show a striking uniformity for the period, with a minimum 

 of 119 c.c. and a maximum of 264 c.c. The period was nearly rainless. 



635 



S4I ^^3 



390 



IL 



d21 



.00 



•HI 



.00 



.00 



f^mNFilLL 



.00 



5S4 



460 



\iM 



.00\-04- 



293 



2S2 



S2L 



idL 



2.88\ 



42 



■08 



230 232 229 



^2^/.67 



322. 



L6n- 



£L 



216 



./9 



/mr £SJuMCl 8 IS 22 i9J'uiS6 13 £o £f/>us3 lo n 2-^ 3/ Sep"? /•* 



Fig. 5. — ^Weekly precipitation and evaporation indices, summmer of 1908, Tucson, Arizona. 



Tucson, Arizona (fig. 5) : From the beginning of the series to June 

 29 the intensity of evaporation rose rapidly to a maximum of 635 c.c. 

 for the week ending on the latter date. With the advent of the sum- 

 mer rainy season the rate then fell in 3 weeks to a magnitude of 206, 

 less than one-third of the maximum. During the remainder of the 

 series (ending September 14) the rates varied between 229 and 302. 

 This latter half of the summer is a season of relatively great precipita- 

 tion at this station, and the low evaporation intensity of the rainy 



