3. 1 Weather systems 



In winter, polar-continental air dominates the region resulting 

 in many clear, dry and bright days. Daily mean temperatures are generally 

 below freezing from mid-December through early March except for a shorter 

 period along the shore. Pacific air masses frequently reach the area during 

 the winter resulting in somewhat higher temperatures and humidities. Occa- 

 sionally tropical air reaches the Sound area in the winter. Because of its 

 lower density the tropical air usually overrides the colder air from the 

 north but at times it reaches the surface causing the well known "January 

 thaw." 



In summer, air from the Gulf of Mexico and the tropical Atlantic 

 brings high temperature and humidity. In crossing the Sound from the south- 

 west this air mass may be cooled from below creating pollution-trapping 

 inversions along the Connecticut shore. The hazy skies may clear up after 

 midday if the inversion is destroyed, but when the sea breeze prevails or if 

 the flow is more southerly stable conditions may remain into the evening 

 and longer. Air of Pacific origin traveling eastward from the Canadian north- 

 west brings bright skies and relief from haze and pollution associated with 

 the tropical air. 



North Atlantic source region air also reaches the area in the 

 summer resulting in cooler temperatures and frequently steady light precipi- 

 tation. Polar continental air, modified by intense solar heating, occa- 

 sionally moves into the area in summer while hot dry continental air from 

 Arizona and New Mexico infrequently reaches the area during this season. 

 Spring and autumn are periods of transition characterized by rapid alterna- 

 tion of air masses and fast changes in weather patterns. 



Winter storms frequently move into the region from the area near 

 Cape Hatteras, N.C. During the remainder of the year storms develop further 

 east and north over the Atlantic Ocean and further north over the Great 

 Lakes. The period August through November is characterized by occasional 

 tropical disturbances. 



Air masses undergo temperature and humidity changes when they 

 move over the Ocean and Sound, travel over snow covered ground or are lifted 

 over hilly terrain. The presence of the Sound provides one of the major 

 climatic controls for the area in that it acts as a vast reservoir for the 

 storage and subsequent exchange of heat energy with the atmosphere. 



3.2 Availability of cl imatoloqical records 



Reliable records date back to 1778 at New Haven, Connecticut and 

 for shorter periods elsewhere in the Long Island Sound Regional Study Area. 

 Comprehensive analysis of cl imatological data for selected time periods are 

 available in: The Climate of Connecticut (3.)", The Precipitation Regime of 

 Long Island, N.Y. (J2) ; The Climatic Guide for New York City, N.Y. and Near- 

 by Areas (U6) ; and Climates of the States, New York (kj) . 



