USA – Frostbelt / Sunbelt
Cloud distribution, thermal continentality and the prevailing meridional air mass and thus temperature exchange significantly control the number of days of sun and frost in the USA. The continent’s openness to the north requires a clear meridional differentiation according to the number of frost days or hours of sunshine per year.
SUNBELT
Most hours of sunshine are measured in the lee of the southern Cordilleras. The location of this space in the area of influence of the subtropical high pressure belt leads to an even stronger cloud dissolution than in the lee of the northern Cordilleras and thus to a corresponding increase in the duration of sunshine. Nevertheless, the number of frost days with up to 120 days in the sunbelt is far above the corresponding comparison values from Europe.
The theoretically possible duration of sunshine is sometimes longer in Boston and Chicago than in Arizona. The cloud cover in the north-west and north-east of the USA, however, greatly reduces the actual duration of sunshine – there are areas in the Cordillera and Appalachian reservoirs, which are characterized by western air currents all year round. The southwest and southeast of the USA, on the other hand, are under the influence of the subtropical high.
FROSTBELT
The regional differentiation of the frost days follows a north-south change in the intensity of solar radiation, the change in the degree of continentality and a change in altitude. The lowest number of frost days is therefore recorded in the southwest of the USA and on the coast of the Gulf of Mexico. The highest number of frost days can be observed in the north and in the Rocky Mountains.
Some of these areas coincide with those with the least amount of sunshine. Frostbelt and Sunbelt are spatially not mutually exclusive, because a high level of irradiation thanks to low cloud cover also means unhindered radiation – sometimes even frost, especially in the winter months. In the north of the USA, frost is mainly determined by inflowing arctic air masses, in the arid regions in the south of the USA the nocturnal radiation frost predominates. For more information about the continent of North America, please check businesscarriers.com.