Illustrated in Figure 15 are 

 isotherms developed for south Flor- 

 ida (Thomas 1970) describing mean 

 annual temperature (Figure 15a), and 

 the mean monthly temperature for 

 the coolest month (January, Figure 

 15b) and the warmest month (August, 

 Figure 15c). Differences between 

 coastal/keys areas and inland re- 

 gions are highlighted by the fact 

 that the isotherm contours follow 

 the coastline (Figure 15). The 



Figure 15. Isotherms for study 

 area annually, and in 

 January and August 

 (adapted from Thomas 

 1970). 



coastal/keys areas reflect a mari- 

 time influence, exhibiting low daily 

 ranges of temperature and rapid 

 warming of cold air masses which 

 pass to the east of the state (USDC 

 1981a, 1981b). Inland locations 



generally display a greater range of 

 temperatures due to the more rapid 

 heating and cooling of ground sur- 

 faces (Gerrish 1973, Dames and Moore 

 1978). For example, the average 

 daily range of temperature is 5.5°C 

 (10°F) at Miami Beach and Key West, 

 while well inland in the Everglades 

 the average daily range is near 10°C 

 (18°F) (USDC 1981a, 1981b). Another 

 example of this temperature differ- 

 ential between coastal and inland 

 areas appears in the annual number 

 of days with temperatures reaching 

 32°C (90°F) or above. Miami Beach 

 reports less than 15 days per year 

 as compared to inland stations re- 

 porting approximately 60 days per 

 year (USDC 1981a) . The minimum tem- 

 peratures reported for coastal/ keys 

 and inland sites repeat this trend. 



3.5 RELATIVE HUMIDITY 



A simple statistical represen- 

 tation of relative humidity is dif- 

 ficult for many locations because of 

 large diurnal and seasonal varia- 

 tions (USDC 1981a, 1981b, 1981c). 

 In Florida, and more so in south 

 Florida, the situation is less com- 

 plex because of the abundance of 

 moisture throughout the year (Dames 

 and Moore 1978). Table 6 summarizes 

 the mean monthly relative humidity 

 for 0100, 0700, 1300, 1900 hours at 

 the Miami, Ft. Myers, and Key West 

 first-order weather stations. 



Combining all hours of the day 

 and all months into a single aver- 

 age, the mean annual relative humid- 

 ity is quite uniform throughout the 

 basin, averaging about 75% (USDC 

 1981a, 1981b, 1981c). Relative 



humidities are generally highest 

 during the early morning hours. 



35 



