Azerbaijan is situated on the northern extremity of the subtropical zone, south-eastern Caucasus, and north-western part of Iran plateau. Its climatic diversity is caused by the complicated geographical location and landscape, the proximity of the Caspian Sea, the effect of the sun's radiation, air masses of different origins, etc.
Landscape
As a predominantly mountainous country, Azerbaijan is surrounded by the Major Caucasus, Minor Caucasus, Talysh, and North Iranian Mountains. The Kur lowland between the Major and Minor Caucasus stretches to the Caspian Sea in the eastern part of the country. The Major Caucasus, situated in the north of the country and stretching from the north-west to the south-east, protects the country from direct influences of cold air masses, coming from the north. That leads to the formation of subtropical climate on most foothills and plains of the country. Other mountain chains, surrounding the country also have a great impact on air circulation. The complexity of a landscape causes the nonuniform formation of climatic zones and creates vertical climate zones, etc.
Solar Radiation
Plains and foothills are characterized by high solar radiation rates. The sun shines for 2200-2400 hours a year on the Kur-Araz lowland, Apsheron peninsula, and other plains and foothills, while the indicator totals 2600-2800 in the plains around Araz in the Nakhichevan Autonomous Republic. Due to increased cloudiness in the mountainous regions, only 1900-2200 hours per year are the sun shining. The sun is bright during 2200-2500 hours a year at an altitude of over 3,000 meters. The total annual radiation equals 128-132 kcal per 1 sq. cm. It declines towards the mountains (down to 120-124 kcal-cm2, at a height of 500-600 meters above sea level), then gradually increases and reaches 140-150 kcal-cm2 at a height above 3000 meters of Major and Minor Caucasus. The total amount of solar radiation affecting Araz plains in Nakhichevan totals 148-150 kcal-cm2, it increases in mountains and reaches 152-160 kcal-cm2. The radiation on the country's plains and foothills amounts to 40-50 kcal-cm2 (in Lankaran -50-60 kcal-cm2, in mountains-15-25 kcal-cm2).
Circulation of air masses
The formation of climate in Azerbaijan is influenced by cold air masses of arctic (Kara and Scandinavian anticyclones) and temperate (Siberian anticyclones) and maritime (Azores maximum), hot air masses of tropical zones (subtropical anticyclone and southern cyclones), Central Asian anticyclones and local weather conditions. Regarding landscape diversity in Azerbaijan, air masses have different ways to enter the country. Thus, cold continental and maritime air masses though not preventing the hot masses from entering the country from the south yet cause changes in some properties of hot air masses and influence the dynamics of atmospheric conditions.