Precipitation 



Precipitation is generally well distributed throughout the year. 

 Precipitation from mid-latitude cyclones (northeasters) predominates in the 

 winter, whereas local convection (thunderstorms) accounts for most of the 

 summer rainfall. 



Measurement instruments 



Electronic rain gauge. A Belfort Instrument Company (Baltimore, 

 MD) 30-cm weighing rain gauge, located near the instrument shelter 47 m 

 behind the dune, measured daily precipitation. According to the manufacturer, 

 the instrument's accuracy was 0.5 percent for precipitation amounts less than 

 15 cm and 1.0 percent for amounts greater than 15 cm. 



The rain gauge was inspected daily; however, the analog chart recorder 

 was inoperable the entire year. 



Plastic rain gauge. An Edwards Manufacturing Company (Alberta 

 Lea, MN) True Check 15-cm-capacity clear plastic rain gauge with a 0.025-cm 

 resolution was used to monitor the performance of the weighing rain gauge. 

 This gauge was located near the weighing gauge, and the gauges were com- 

 pared on a daily basis. Very few discrepancies were identified during the year. 



Results 



DaUy and monthly average precipitation values are shown in Figure 5. 

 Statistics of total precipitation for each month during this year and average 

 totals for all years combined are presented in Table 2. 



Wind Speed and Direction 



Winds at the FRF are dominated by tropical maritime air masses that 

 create low to moderate, warm southern breezes; arctic and polar air masses that 

 produce cold winds from northerly directions; and smaller scale cyclonic, low 

 pressure systems, which originate either in the tropics (and move north along 

 the coast) or on land (and move eastward offshore). The dommant wind direc- 

 tion changes with the season, being generally from northern directions in the 

 fall and winter and from southern directions in the spring and simimer. It is 

 common for fall and winter storms (northeasters) to produce winds with 

 average speeds in excess of 15 m/sec. 



Chapter 2 Meteorology 



