CHAPTER 3 

 CLIMATOLOGY 



3.1 INTRODUCTION 



A classification system devised 

 by the National Weather Service 

 divides Florida into seven climatic 

 divisions, three of which influence 

 the study area (Figure 9). Each 

 zone encompasses an area within 

 which basic climatic variables, pri- 

 marily temperature and rainfall, are 

 generally consistent when averaged 

 over extended periods of record. 

 The boundary lines between climatic 

 divisions approximate lines of 

 change and do not depict radical 

 changes in climatic patterns. Like- 

 wise, station to station differences 

 occur within any one division, espe- 

 cially where coastal boundary influ- 

 ences are significant. In spite of 

 these limitations, the climatic 

 divisions offer a ready means of 

 organizing statewide and basin-wide 

 descriptions, and will be used in 

 much of the discussion to follow. 



Many meteorological measure- 

 ments are available from the three 

 first-order weather stations opera- 

 ted by the National Weather Service 

 that triangulate the study area 

 (Ft. Myers, Key West, and Miami). 

 An additional, more limited selec- 

 tion is available from numerous 

 other government agencies. These 

 measurements are collected for a 

 variety of applications, agriculture 

 and aviation being two of the more 

 important. Detailed meteorological 

 information is restricted to a few 

 of the available stations in the 

 basin, including Key West (Inter- 

 national Airport), Homestead AFB, 

 and the Key West Naval Air Station 

 (NAS). In addition to the Key West 

 station, two additional, primary 

 NOAA weather stations (Miami and 

 Ft. Myers) are included to complete 



the measurement of the basin. For a 

 more in-depth discussion of weather 

 stations adjacent to and within 

 the study areas see Parker et al. 

 (1955), Thomas (1970), Bradley 

 (1972), Thomas (1974), and MacVicar 

 (1981). 



• ^JACKSONVILLE 



FLORIDA CLIMATIC 

 DIVISIONS 



KEYS,.-'* 



KEY WEST woo . ' *' 



- — — — S'udy flreo 



US Deportment ( Commerce. I97Z 



Figure 9. Florida climatic divisions 

 (adapted from USDC 1972) 



3.2 RAINFALL 



The Everglades/Bay/Keys basin 

 has a tropical savanna climate char- 

 acterized by a relatively long and 

 severe dry season, and a wet season 

 (Hela 1952). The dry season, last- 

 ing from November to April (Riebsame 

 et al. 1974), generates between 

 18% to 33% of the annual rainfall 

 (Thomas 1974), primarily from large 

 scale (synoptic) winter frontal 



25 



