Frost pockets in the Santa Monica Mountains

Includes bibliographical references (pages 56-65)In the fall of 1964 a survey was initiated in the Cold Canyon\ud drainage basin of the Santa Monica Mountains, Los Angeles County,\ud California, to observe temperature variations in protected valleys.\ud The area is located approximately 3 to 4 miles from the Pacific Ocean, in a region genera11y thought of as possessing a mild climate. After\ud preliminary work showed lowest minimum temperatures in valley bottoms,\ud five shelters with recording thermometers were located at various exposures within the area. Previous studies have related frost pockets primarily to the drainage of cold air down hillsides. This factor is felt to be of less significance then strong outgoing radiation, inversion strength, and the absence of wind. Variations of minimum and maximum temperatures, daily range, and inversion strength are analyzed for the five locations. Results show that frosts occur frequently in and around two valleys but are almost entirely absent at a nearby slope and mountain peak. maximum temperatures are fairly uniform except at the mountain site. Following from this, daily ranges are abnormally high in the valleys and subdued at elevated exposures. Minimum temperature inversions between valleys and hills are correlated with clear and cloudy weather. The strongest inversions occur during clear, calm, and dry conditions