1.9. Climate

Climate of the water area national sector and coastal land is determined by their geographical position, seasonal atmospheric circulation, peculiarities of land relief, heat influence of sea water mass and water-change between the North. Middle and South Caspian. The general influence of the mentioned factors forms the whole moderate warm climate of the region, approaching on the south to sea subtropics. At the same time the climate of semi-desert and dry steppes is typical for seaside line of Samur-Devechi and Pri-Caspian-Apsheron regions, and area of the Central Aran as well. Moderate warm climate with dry summer or even spread of precipitation is typical for the rest territory. Climate type is shown on Fig. 16.

The described region is characterized by great flow of sun light and heat the value of which varies within 1900-2500 h/y. for period of long standing, including Samur-Devechi and Lenkaran regions with the adjacent water area - 1900-2200 h/y., on the rest territory it is 2200-2500 h/y. Region location in relatively low latitudes causes an intensive income of sun radiation. It is shown by positive value of year radiation balance - 2730 MJ/m² on average offshore and 2100-2310 MJ/m² onshore. For the whole territory onshore and offshore the radiation balance is positive from March till October and has maximal values in June and July (462-504 MJ/m² in month). The negative balance is only in December - January -4.2 - 42 MJ/m².

Dates of transition of average daily air temperatures through the definite limits are accepted as the basic features determining the character and duration of climatic seasons. Within the coastal zone and water area the date of transition of air average daily temperature through 5⁰C is used as a sign of winter beginning and end. The temperature transition through 18-20⁰C is used for summer beginning and end. Proceeding from these criteria the average dates (date and month) of seasons' coming are somewhat differ from the calendar ones and vary due to the latitude. Spring - from 10.02 to 20.03; summer - from 10.05 to 31.05; autumn - from 30.09 to 30.10; winter - from 01.12 to 10.01. Summer is the most durable season - from 4.0-4.5 months on the north to 5.5-6.0 months on the south of the region. Thus, the winter season duration reduces from the north (2.5-3.0 months) to the south for a month. Accounting the fact that southward from Apsheron peninsula the air temperature usually is not 5⁰C below onshore and offshore areas as well, winter is practically absent in this region as a climatic season.

1.9.3. Air temperature

Atmospheric processes influence enough for temperature seasonal fluctuations. The Main Caucasian Ridge plays a great role in these processes formation. It blocks to pass the northern cold masses in the southern direction. Analysis of the average temperature change shows that the major part of year (late August till April) it is higher over the open sea than onshore, in the rest period (May-July) its distribution is inverse. Average annual air temperature of coastal zone is shown on Fig. 17.

Sea air temperature. In winter the thermal regime of air is corresponded to sea climate, there is a land influence only in shore narrow line. February is the coldest month. The temperature increase from March till July is even, but generally it is lower than onshore. The autumn cooling is more intensive than warming. Moreover, sea air colds down slower than onshore. The maximum of summer temperatures falls to July and late a little correspondingly to onshore temperature. In sea deep water part this maximum falls to August. Thus, the summer thermal regime of air is closer to continental one.

The typical feature of the South Caspian deep water part is higher temperatures of air n winter months. It is explained that they acquire an additional heat from great masses of sea water warmed in summer.

Average annual temperature of air varies from 13-14⁰C on the Middle Caspian to 14.5-15⁰C on Apsheron rapids and 15-17⁰C on the South Caspian. Average monthly temperatures of air over sea are given in Table 1-5. Maxima of summer temperature reach 27-30⁰C in July.

Table 1-5. Average monthly air temperature over the sea (⁰C)

Land air temperature. The thermal regime of and air (except the middle - high-mountains of the Greater Caucasus) is characterized by hot summer and warm winter. The maximum of summer temperatures falls to July-August, maximum of winter temperatures - to January-February as well. At the same time in autumn-winter period the seashore is distinguished by higher air temperature (for 1-2⁰C) than inner regions. Generally, the average annual temperature of air grows from the north to the south, it is 6-10⁰C in the middle - high-mountain zone of the Greater Caucasus and Talysh, 10-14⁰C in Samur-Devechi, Pri-Caspian-Apsheron, Gobustan regions and Talysh low-mountains, 14.0-14.5⁰C in coastal line of Gobustan foothills, inner part of the Central Aran and Lenkaran lowland, over 14.5⁰C in the coastal of the Central Aran. Minima of temperatures falls to the second half of July and the first half of August and reaches 40-43⁰C in the central Aran, Gobustan and on Apsheron, 35-40⁰C on the rest part of the territory.

Average monthly temperatures of air over land are given in Table 1-6.

Table 1-6. Average monthly air temperature over the land (⁰C)

Wind character over the land and sea is determined by large-scale influences of the atmosphere circulation and local baryc-circulatory and thermal conditions as well. The region is subdivided into regions with relatively stable regime of wind direction (Fig. 18). More distinctly such zones are distinguished during the main seasons of year - winter and summer. At the same time the south-eastern thoughs of the Greater Caucasus on the north and Talysh Mountains on the south influence actively upon the wind regime.

Wind direction. The northwestern flows (35-50% onshore and 25-35% offshore) have the most recurrence in autumn-winter period onshore and the adjacent water area of the region northern part. The southern winds have lesser recurrence (18-30% and 19-35% accordingly). Northern (25-35%) and southern (21%) winds prevail on Apsheron and surrounding water area; southward up to South-East Kultuk - north-eastern winds (20-25%); far southward in Lenkaran zone - the north-western (25-45% onshore and 20% offshore) winds. Besides, the western winds are frequent, their recurrence is 10-17%. In the central part of the South Caspian the wind activity is weak and unstable.

In spring the south-eastern and eastern winds prevail on the north - 20-25% onshore and 20-35% offshore. In Apsheron region the northern and southern winds (36 and 15% accordingly) are still there, and the south-astern winds (25-35%) on the region south as well.

In summer the wind regime changes suddenly. On the region north there is a prevalence of the north-western (30-40% offshore and 15-25% onshore) winds; in Apsheron region - of the northern (40-50%) winds; southward - of the north-eastern (25%) winds; near the shore of Lenkaran zone - of the western (30-45%) winds, and closer to the central part of the South Caspian - of the south-eastern (30%) winds.

Wind rate. In cold and warm periods as well the wind rate increases from the south to the north. In cold period of year the average rate on the Middle Caspian reaches 7-8 m/s, decreasing in its coastal line up to 4-6 m/s. In region of Apsheron peninsula and the adjacent water area the average wind rate is 6-8 m/s, on the South Caspian - 4-5 m/s in open sea and 2-3 m/s onshore. In warm period the high average wind rates keep on the Middle Caspian (5.5-6 m/s) and Apsheron region (6-10 m/s) and small rates on Lenkaran shore of the South Caspian - 2.5-2.7 m/s and 3-5 m/s in open sea.

In more distant regions onshore the average wind rates are lower, they are as 2-5 m/s in plain and foothill zone of Samur-Devechi regions, 2-3 m/s on the south-eastern submersion of the Greater Caucasus, 1.5-2.5 m/s in the Central Aran and Talysh Mountains.

On the Caspian shore the strong and storm winds are frequent, on the Apsheron peninsula their rate reaches 35-40 m/s ("baku north")

The yearly course of air humidity is like the yearly course of air temperature. The relative humidity of air over the sea increases towards the north and the south from the Apsheron trough, and towards the shore (from the west to the east) over the land. This is concerned to the average annual and average monthly indexes of relative humidity as well. Onshore the highest average annual indexes are in coastal line - 70-75% in Samur-Devechi and Lenkaran regions and 60-70% on the rest parts. As far from the shore these indexes decrease up to 55-60%. Within the water area the average annual indexes are 75-80% over Apsheron rapids and 80-85% over the Middle and the South Caspian.

The average monthly relative humidity of air is given in Table 1-7.

Table 1-7. Average monthly relative air humidity

On the coastal land the annual sums of evaporation vary within 400-1200 mm depending upon the territory vertical zonation (Fig. 19). The maximal value of evaporation (1000-1200 mm) are typical for the South-East Shirvan, Gobustan and Apsheron peninsula. The southern part of the Central Aran, Lenkaran lowland and coastal line of Samur-Devechi region up to latitude of Gilyazi Dili cape are characterized by evaporation within 800-1000 mm. As fat towards the water-division of the Greater Caucasus and Talysh Mountains the evaporation values decrease according to the exponential law, reaching 400-600 mm in the upper belt (to 3000 m). Generally the annual course of evaporation follows to the annual course of air temperature: the most values are observed in summer months (July-August); the least - in winter months as well (January-February).

The evaporation off sea surface is the main consume component of its balance. According to the actual area of sea surface, temperature regime and atmosphere circulation the annual evaporation off sea surface varied from 920 to 1040 mm of layer, 970 mm of layer of 375 km³ per year on average. The most internal annual change of evaporation is observed during sea warming and cooling. During the long-standing period the main volume of evaporation (70%) falls to the period from June to December. At the same time in the Middle and South Caspian the evaporation processes are more developed in August-September. According to data of hydrometeorological station "Neft Dashlary" the annual value of evaporation off sea is 1200-1300 mm for the 90s. The main part of evaporation falls to April-September (75%).

During the whole year the total cloud onshore is more than in open sea. At the same time on the western shore of the South Caspian the cloud is the most in all seasons, it is connected with the cyclic activity in this region.

Offshore the most cloud is observed in clod period, and less in summer. In winter its average quantity varies from 5.5 marks on the south to 7.5 on the north. In spring the range of average cloud change is from 4-5 to 6.5-6.8 marks with tendency of reduction in direction from the shore to the open sea. In summer the spread of average cloud is more even and varies within 2.4-3.8 marks. At the same time in autumn it is closer to the spring one varying from 4.5 to 6.7 marks. Onshore in winter the average cloud varies from 6.5 (Lenkaran) to 7.8 marks (Samur-Devechi), in spring and autumn these values decrease to 5.8-6.8 marks. The least cloud is observed in summer months (3.5-4.0 marks).

The main cloud type over the sea water area, plain, foothill and middle-mountains regions of the coastal zone are layer-cumulus clouds, and torn-cumulus clouds for the high-mountain regions. During a day the maximum of cloud falls to morning, minimal - to day and evening hours. Clear days are more from June till September, overcast days - from November till March.

Generally the precipitation regime depends upon the interaction of air masses with sea and relief of coastal zone. Here from 150 mm near Baku city and Gobustan region shore up to 300-600 mm in Samur-Devechi region and 1200-1700 mm in Lenkaran-Astara zone of precipitation fall during a year (Fig. 20). According to data of hydrometeorological station "Neft Dashlary" the annual sum of precipitation is 110 mm near Apsheron trough.

During the warm semi-year (April-September) the precipitation have their lesser quantity on Apsheron peninsula and the Central Aran - 75-110 mm. The coastal line of Samur-Devechi region, Gobustan and the north-eastern foothills of Talysh up to Gizilagach gulf are characterized by value of 100-250 mm. In direction from foothills to high-mountains the precipitation quantity increases from 200-300 mm to 400-600 mm on the Greater Caucasus and up to 400 mm in Talysh Mountains. At the same period in Lenkaran-Astara shore the precipitation fall in quantity of 600-800 mm and more.

During the cold semi-year (October-march) the most part of the Central Aran, foothill and coastal line of Gobustan and the southern part of Apsheron peninsula are still characterized by the lesser volume of precipitation total quantity. Here it is 150 mm and lesser and even 100 mm. Northward from these territories the precipitation quantity varies within 150-200 mm, southward there is a gradual increase of precipitation summary quantity up to 300-400 mm in Talysh Mountains, to 800-100 mm and more in lowland and foothill line of Lenkaran region.

The annual number of precipitant days >0.1 mm is 60-80 days in the Ccentral Aran and Gobustan, 70-90 days in Pri-Caspian-Apsheron part of Samur-Apsheron region and Talysh Mountains and 110-150 days on the shore and foothill line of Lenkaran region.

Fogs are typical for year cold half, especially for the spring period. According to average long-standing data the number of fog days is 32-38 days. The least number of fog days (10-13 days) falls to Apsheron peninsula. The most duration of one fog can reach 2-3 days. The prevalence of radiation figs (64-73%) is typical for the shore, they are formed when calm and weak-wind weather (1-2 m/s). Advective and advective-radiation fogs have a low recurrence.

1. Hydrometeorology and hydrochemistry of seas, v.VI, Caspian Sea, edit.1, Hydrometeorological conditions. – Saint-Petersburg; Gidrometeoizdat, 1992.

2. Hydrometeorological conditions of shelf zones of the USSR seas, v.2, Caspian Sea. – Leningrad; Gidrometeoizdat, 1986.

3. Caspian Sea. Hydrology and climate. – Moscow; "Nauka", 1986.

4. Azerbaijan climate. – Baku; Publishers of Academy of Sciences of Azerbaijan SSR, 1968.

5. Reports of the State Committee of Hydrometeorology for 1990-2000.

INTRODUCTION

SECTION 1

SECTION 2

SECTION 3

SECTION 4

SECTION 5

APPENDIX 15

APPENDIX 16

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