38 MASS. EXPERIMENT STATION BULLETIN 402 



promising weather item being tested. A frost-warning service using these for- 

 mulas was started in 1920, the cranberry growers paying the telephone charges,^^ 

 and is still maintained. The formulas have been changed from time to time to 

 use new information and data. 



Observations were made in the towers of the forest fire service at Middleboro, 

 Bournedale, and Barnstable in 1927, 1928, and 1929, but they failed to provide 

 data useful in frost predicting. 



Observing was begun in the fall of 1924 at North Carlisle in Middlesex County, 

 at the bog of the Lowell Cranberry Company (elevation about 150 feet). As 

 data from this place improved the formulas for computing minimum bog tem- 

 peratures for Cape Cod, other stations were established as follows: 

 In Worcester, Worcester County, in May 1928, at home of Mr. Clifford L. Davis, 



Winter Hill Observatory, 805 Grove Street (elevation 625 feet). 

 In Holliston, Middlesex County, in September 1929, at home of Mrs. Evelyn 



Weston (elevation about 240 feet). 

 In East Gloucester, Essex County, in May 1931, at home of Rev. Ralph M. 



Barker (elevation 15 feet). 

 In North Harwich, Barnstable County, in June 1929, at home of Mrs. Mary 



Soutter. 

 In Fitchburg, Worcester County, in May 1931, at ofifice of city sewage plant 



(elevation 402 feet). 



Observing in the frost seasons was continued through 1942 at all these places 

 except the last two. 



Six localities have provided data useful in the final formulas. Marked on the 

 map (Map 2) by small circles, they are: East Wareham (5), Worcester (1), 

 East Gloucester (4), Milton'^^ (6), Paxton^e (3), and Carlisle (2), named in the 

 order of their value in this work. 



The formulas seem to be now in their final form. They are empirical and made 

 to show what minimum temperatures to expect under more or less ideal condi- 

 tions, when temperature fall during the night is least affected by cloudiness, wind, 

 or unusual special influences. They may be regarded as guides to experience. 

 While they are being used in frost predicting, they are presented here merely as a 

 study of the relations of noon and evening weather conditions to ensuing minimum 

 temperatures near the surface of lowlands in southeastern New England in the 

 cranberry frost seasons. 



The "minimum bog temperature" is the lowest temperature during the night 

 at the tops of cranberry vines.^^ Minimum temperatures vary on frosty nights 

 not only on different bogs but on different parts of the same bog.^^ The for- 

 mulas are made to show the minimum likely to occur 'over average areas of the 

 bogs in cooler-than-average locations. Growers with bogs in warm places can 

 allow for this. The variation in minimum bog temperatures in different parts of 

 the cranberry district is greatest on nights following evenings with large differ- 

 ences in the dew point at the various observing stations, probably because of the 

 movement and mingling of masses of air varying greatly in humidity and large 

 variation in local winds and cloudiness. 



2*The warnings were also given by radio in 1940 and 1941. 



2^Blue Hill Meteorological Observatory (elevation 640 feet). 



^^Observing station of the Yankee Network Weather Service (elevation 1395 feet). 



2^A11 bog temperatures mentioned in this paper are temperatures taken with unsheltered mini- 

 mum registering thermometers without radiation shields. Such thermometers, covered with dew 

 or frost as they nearly always are on frosty nights, are nearly full radiators (Schmidt, E., Refrig. 

 Engin. 28 (3): 152 and 156, 1934) and give only their own temperature, not that of the air around, 

 them. They reflect truly, however, the temperature of plants near them, also coated with dew or 

 frost and radiating as freely. 



2^Cox, op. cit., pp. 46-49; Franklin, op. cit., p. 28. 



