Danube Delta: A lost paradise

The climate of the Danube Delta. The Danube Delta combines the temperature semi-arid climate space typical of the Pontic steppes. The aquatic very wide plane spaces differently covered by vegetation and interrupted by sandy islands of the marine fields, make up an active area specific to the delta and to the adjacent lagoons but totally different from the belonging to the Pontic steppes. This active area reacts upon the total radiation intercepted by the general circulation of the atmosphere resulting in a mosaic of microclimates. The total radiation varies from a minimum of 3,5 kcal/cm2 recorded in winter and a maximum of 17 kcal/cm2, in July. In accordance with the intensity of the main barometric centers activity, specific weather conditions settle in: mild winter days (when the north-eastern barometric European center intensifies), frosty winter days, with heavy winds (when the tropical anticyclone intensify), rainy summer days (when the air in the Mediterranean basin interacts with the cold air in the north-west of Europe. The duration of the brightness of the sun is long the multiannual average is the Mediterranean basin interacts with the cold air in the northwest of Europe. The duration of the brightness of the sun is long, the multianual average is 2250 hours and it can reach 2600 hours in years with reduced nebulousness. The temperature is not-uniformly distributed on the area of the delta. The multianual averages indicate the temperature increases from the west to the east. At the top of the delta (Tulcea), the medium annual temperature is 10.96 degrees C, in the coast (Sulina) it is 11.05 degrees Celsius, and on the high sees of the Black Sea (The Gloria Platform) it is 11.86 degrees C. The daily medium altitude show major differences due to the nature of the active area: at Govora it varies from a maximum of 9 degrees C in July and a minimum of 3.8 degrees in December, at Sulina it varies from 2.8 degrees C in July and 1.4 degrees C in November, and at Gloria station from 2.3 degrees C in July and 1 degree C in December and February. The total annual sums of the medium daily actual temperatures are almost 1600 degrees C. The air humidity registers the highest values on the Romanian territory. The relative air humidity varies in winter from 88 to 84 % at Govora and from 89 to 85% at Sulina and Sfantu Gheorghe. Precipitation is reduced in amount and they decrease from the north to the south owing to the influence both of the active area specific to the delta and the Black Sea. At the front side of the Danube Delta (Tulcea) a medium multiannual amount of precipitations of 450 mm is registered, and at Sulina, the amount registered is 360 mm. On most of the Delta the amount of rainfall is 350-400 mm, and on the deltaic littoral and most of the lagoons, the amount is below 350 mm. The snow layer is thin and it does not last for long periods of time, except the period of severe winters. This is what happened in 1928 -1929, 1953-1954, 1941-1942, 1984-1985, when the sea was frozen for 40-60 days by the coast. The dominant winds blow from the northern sector alternating with the southern sectors the severest wind acceleration are recorded in winter and in transition seasons. Seasons are not uniformly distributed in the Danube Delta. At the front side of the Delta, in Tulcea, the average for 90 years reveal that there are 142 summers days and only 15 winter days, springs are longer (122) than autumns (83 days).