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The climatic and agroclimatic characterization of summer 

on the territory of Moldova

 

The beggining of the summer season is considered conventionally the transition of the daily average air temperature through 15ºC, observed in  Moldova  between 8 May (Cahul)  and 19 May (Briceni). In some years, depending on the characteristics of synoptic processes, summer limits may deviate essentially from the norm. The earliest summer during the entire period of observations started in the third decade of April (1968), and the latest in the first decade of June (1955, 1991).

The long term average air temperature during summer constitutes +18,5..+21,0ºC. The hottest was the summer of 2007, the average temperature during this season was +22..+25ºC, which is 3-4ºC above normal. The coldest was the summer of 1976 and 1984, when the average temperature was +16..+19ºC, which is below normal by 2º C. The hottest summer month is July, its monthly average temperature represents in the territory +19 .. +21º C. The highest temperature for the season +41.5 º C (Kamenka, 21 July, 2007) was also observed in July. The long term average temperature of the soil surface in July is +24 .. +27º C and the maximum can reach on some days +74º C (Leova, 19July, 2007). The total number of days with high temperatures (30º C and above) for the season is between 8-27, the biggest number - 60 days (2007). Summer minimum temperatures do not drop below +1,6 º C (Briceni, 1 June, 1955), on the soil surface to -0,4 º C (Briceni, 1 June, 1990).

In summer, compared to other seasons, rainfall varies greatly. The amount of precipitations per season - 170-235 mm, but in some years, it ranged from 37 mm (Cahul, 1924) to 531 mm (Chisinau, 1948). Daily maximum rainfall for the season ranges from 70 mm to 220 mm.

Short showers are frequent in summer, the number of days with precipitation averages across 25-35 days. Heavy rains are often accompanied by thunderstorms (average 17-25 days per season) and hail (to an average of 3-9 days). The number of days with fog is reduced compared with the spring to an average of 1-6 days.

For the summer season, the greatest danger is represented by heavy rainfall and intense hail, which are observed annually. Strong winds can average once every 2 years, and vortexes - once every 10 years. In addition, extreme damage to national economy is caused by severe droughts that occur in Moldova once every 5 years.

The summer agrometeorological conditions on the territory of Moldova are generally satisfactory for the growth and development of crops.

According to long term data, the period from 20 May to 3 June marks the flowering of winter wheat.  The winter wheat moisture supply in the moment of flowering is observed all aver the republic. The average long term moisture reserves in the soil layer of 1 meter depth constitutes in this period 80-130 mm, and only in several districts from SE, they do not exceed 60-75 mm. According to long term data, flowering of winter wheat is observed at the beginning of June (3-9 June). The milk ripeness of grains occurs in the second half of June. In Moldova, the period of winter wheat grain filling (flowering and milk ripeness of winter wheat) lasts in average 15 days.  Moisture supply for grain filling of winter wheat is satisfactory and its contents in one meter layer of soil can vary from 90 to 120 mm in the Northern districts of the republic and 60-110 mm in Southern regions. Wax ripeness begins at the end of June first decade of July. Harvesting of winter wheat is done, in general, in the first part of July. Intermittent showers do not create long-term disruption. Almost annually one can observe lodging of crops because of heavy rains and strong winds.

The process of intense growth of maize leaves begins after the formation of the fifth leaf, i.e. in the first decade of June. Moisture supply of maize (1 meter soil layer) during the growing season in the Southern part of the Republic does not exceed 45-50 % from the optimal quantity, in the Northern and Central parts 60-70 % from the optimal. Therefore, for the successful cultivation of maize on the territory of Moldova, irrigation is necessary. In July, according to long term data, one can observe the formation and flowering of maize panicle. The daily average air temperature of +19..+210C and the sufficient precipitations quantity allows the normal development of maize. In August, there is observed the milk and wax ripeness of maize grains. In this period the plants need moisture, the average long-term reserves of productive moisture meter layer of soil in this period amount to 70-100 mm.

The second decade of June marks inflorescences of sunflower. Long term average of productive moisture reserves in a half-meter layer of soil in this period is of 50-60 mm, which is sufficient for the normal growth and development of sunflower. In July, at sunflowers one can observe stem growth and flower formation. During flowering and seed ripening in the northern regions of the country in one meter soil layer it is contained about 100 mm of moisture, and in the central and southern regions the moisture content is lower and is within 50-75 mm. Ripening sunflower in the northern regions of the country happens in late August - early September, and in the central and southern regions - in the middle of August. At the end of ripening the need for moisture is sharply reduced: rainfall at this time could adversely affect the crop, and excess moisture can cause rotting of the basket of sunflower.

June marks the beginning of root growth of sugar beet. Favorable conditions for the growth of sugar beet are created when the moisture in a meter layer of soil passes over 100 mm. In the areas of industrial beet growth in early July, the stocks of productive moisture in a meter layer of soil are good (130-170 mm) and are retained sufficiently in most areas until the end of the month. Starting from the third decade of August, the sugar beet yellowing of outer leaves is noted. By the end of August the need of sugar beets in water is greatly reduced, and productive moisture reserves are generally of 65-85 mm.

According to long term average data, in the first part of June the grapes are flowering. July is marked by an increase in fruit orchards and by ripening of apricot, peach, plum and summer varieties of apples and pears. In July, grapes are growing and at the end of the month early varieties usually reach technical maturity. In the southern areas in late August occurs grape maturity. Optimal moisture conditions in the period from the beginning of flowering to ripening grapes are created when stocks of productive moisture in a meter layer of soil are about 130-160 mm (70-90% field capacity). Actual moisture reserves in most parts of the republic in this period are 100-140 mm.

During the summer growing season vineyards are damaged by unfavorable phenomena such as hail and strong winds that cause mechanical damage to vines and grapes.

 

Chief MCMC                   T. Bugaeva   

Chief AFC                      T. Mironova