A critical analysis of Eastern Mojave desert temperatures

Maximum and minimum temperatures in the Eastern Mojave Desert are primarily a function of elevation: lower elevations are warmer due to greater compression. Both mean maximums and minimun1s for July change about 8 kelvins per kilometer; January mean maximums about 6 kelvins per kilometer and its mean minimums only 60 percent of that. Inversions are common on clear and calm nights as shallow surface air is cooled through contact with the ground, plants, and other objects which rapidly lose heat to the sky. The basin bottoms and mountain hollows can be sinks of very cold air, as the inversion and terrain effectively disallow any mixing, especially in the cool season when air aloft is subsiding. Sunny mountain slopes, a kilometer higher than adjacent basins, can even have slightly warmer maximums than those basins when midwinter high pressure persists. Inversions are weaker and more infrequent in the warmer half of the year as the desert atmosphere becomes less stable and breezier at night. Secondary causes of local and regional temperature differences are due to contrasting exposures to wind and sun, different landform influences and surface covers, and moisture sources and weather. The dry atmosphere is responsible for allowing the occasionally large temperature anomalies: it responds quickly to radiational flux; but the general breeziness of the Mojave Desert tends to minimize mean differences not due to elevation. Desert towns, including Baker, apparently have slightly warmer maximums than nearby unobstructed environs, due to wind breaks and pavement, and well-irrigated places, oases and springs, like Zzyzx, are generally slightly cooler than their barren surroundings. For that reason and because of its atypical local wind patterns, Zzyzx hourly temperatures are considered to be only a fair and conservative representation of most Eastern Mojave Desert areas below about 600 meters elevation.