• Location
• Topography
• Climate
• Orographic Scheme of Tbilisi
  
  

  Location.Tbilisi is the capital of Georgia, with the population of over 1.5 million and total area of 200 sq.km, build up area from which is almost 70 sq.km.

Tbilisi is located at 44 ⁰,80' longitude and 41 ⁰,69' latitude of the Eastern Hemisphere, at eastern part of Georgia. City is built in the bottom of the Mtkvari river depression, which is the main hydrological artery of the city. The Mtkvari depression geologically represents an inter-mountain ravine, with moderate wet and dry types of subtropical climate. Attitude of the river bottom within the city is 200m above sea level.

  Topography.Tbilisi Gorge geographic province occupies valley of the Mtkvari river from Zemo Avchala to the eastern edge of the Teletri Range. The area is bordered on the east by the left side of the Kakheti Highland, on the west by the eastern edge of Trtialeti Range foothills (850-900 m above sea level), on the south, by the very sloppy Teleti Range and on the north by the southern slope of Saguramo Range (see orographical scheme of Tbilisi).

Topography of the Tbilisi Gorge is very diverse. The reason for that are very complex geological structure, as well as erosion-denudation and accumulation processes. The morphological diversity of the Tbilisi Gorge is a result of the asymmetrical positions of the left and right banks of the gorge (Maruashvili, 1964). The left bank is hypsometrically higher and has steeper slopes. Surface there is characterised by numerous small rivers and ravines. At the right side of the gorge, alluvial sediments cover tectonic structure and, therefore, surface is softer. It is slightly disturbed by dry ravines. In this part of Tbilisi the major features of relief are river terraces. Between these two morphologically completely different parts of the gorge, in the lowest part of the city, the Mtkvari river flows.

The Mtatsminda Range, geologically an anticline, dominates the city from the south. To the west it is connected with the Trialeti Range. Top of the range, where city's Central Park Mtatsminda is located, is flat. The largest point here is Mt. Udzo (1418 m).

Between the Mtatsminda and Lisi ranges on Saburtalo syncline is situated one of the largest residential districts of the city. On the right side of the Mtkvari river, in the western part of Tbilisi, is located another large residential district, Didi Digomi, which was built on the Digomi valley (see the map). It is a completely flat valley with an altitude of 440 m above sea level. In the west it rises slightly (550 m) and gradually transfers to the southern foothills of Saguramo Range (Ukleba, 1968).

The last anticline of the right side of river Mtkvari towards the north is the Mtskheta anticline, which continues to the left side of the river and then goes Northeast towards the Gldani district and Mamkoda and Norio villages. On a right side of Mtkvari it embodies by southern slope of Armazi range and bordered on the left side by the bottom of Saguramo-Ialno Range.

 Climate.As a result of atmospheric circulation processes and the complex physical-geographical environment, year-round climatic conditions in Tbilisi Gorge are very diverse. High ranges, located to the west of the city, prevent the penetration of western air masses into the gorge. Therefore the influence of western (wetter) winds here is very weak, and they reach the city with much less moisture than when they started. This is the main cause of dryness of air and low precipitation. When very cold air masses from the west penetrate the city, temperatures drop and precipitation increases. Dry air masses blowing from the east, are responsible for little amount of precipitation on a bottom of the gorge. However, in a higher zone on foothills average amount of precipitation is notably more. The temperature drops rapidly if there is a penetration of Arctic air masses from the East.

Relief forms have a significant influence on climatic conditions here, as the city is surrounded by mountains on three sides. Only the eastern part is comparatively low and open towards the Caspian Sea. The difference between highest and lowest points here is about 500 m. This causes some climatic 'vertical zonation': both steppe and forest climate types are found (Ukleba, 1968).

Mean annual temperatures within the region vary from 10.8⁰ to 12.6⁰. In the low zone the annual temperature is higher than on surrounding mountains and foothills. The coldest month in Tbilisi Gorge is January with a temperature of 0.5⁰ on a bottom and -0.7 ⁰ on hills and mountains. The warmest month is July, when the temperature varies from 21.5⁰ to 24.2⁰. On hills and mountains the warmest month of the year is August (21.6⁰ to 22.1 ⁰). The maximum temperatures within the city sometimes reach 38⁰ (July-August). The absolute minimum temperature here falls down below -20⁰ (Javakhishvili, 1988).

Distribution of precipitation on the bottom, foothills and mountains of the gorge is not the same. Mean annual precipitation is 510 mm in the city centre, only 450 mm in Digomi Valley, and 525 mm in Ortachala. Generally the eastern part of the city is drier (440 mm annually). Maximum precipitation is in May with the following distribution: in the city centre - 88 mm., in Vaziani (eastern edge of Tbilisi) - 93 mm., in Digomi - 79 mm., in Karsani (foothills of Trialeti Range) - 104 mm. Another maximum is usually in September, when monthly amounts of average precipitation are almost half of May levels. The driest months are January (10-26 mm.) and August.

Distribution of cloudy days does not coincide with maximum precipitation periods. It more depends on orographical circumstances and common circulation processes. The maximum cloudiness is in February (67 %), the minimum in August (46 %) (Ukleba, 1968).

The general wind direction in East Georgia is from west to east, although high mountains around the city and other topographic characteristics sometimes changes them. In Tbilisi major wind directions during the year are Northwest (27 %) and north (26 %). Southeast winds are less. The average annual speed of wind in the lower zone is 2-3 m/sec. The heaviest winds usually blow in March and April (3-3.5 m/sec.), and the lightest in the second half of autumn and beginning of winter (2-2.5 m/sec). The Northwest winds are stronger (with 3.5-6 m/sec mean speed) than northern ones. The maximum wind speed within the city sometimes reaches 25-30 m/sec. (Kordzakhia, 1961).

 References

1. Javakhishvili, Sh. (1988). Monthly Characteristic of Climate Types of Georgia. Tbilisi.
2. Kordzakhia, M. (1961). Climate of Georgia. Tbilisi.
3. Maruashvili, L. (1964). Physical Geography of Georgia. Tbilisi.
4. Ukleba, D. (1968). Physical Geographical Division of Eastern Georgia. Metsniereba. Tbilisi.