climatic zones of Sri Lanka. , for students

Sri Lanka is a tropical country. there are 4 seasons according to the monsoonal rain.
This equally important for high national diploma students an undergraduate students.

1. Principles of Crop Production Title :-Climatic zones of Sri Lanka By H.M.N.M.Watagodakumbura

2. Sri Lanka has tropical and quite hot climate. Sri L anka is between 5 and 10 north latitude. Due to that it has year-round warm weather. The mean temperature ranges from a low of 16 °C in Nuwara Eliya in the Central Highlands to a high of 32 °C in Trincomalee on the northeast coast.

3. The average annual temperature - ranges from 28 to 30 °C Day and night temperatures difference(diurnal temperature) may vary from 4 °C to 7 °C . January is the coolest month, night temperatures may fall up to 5 °C . May is the hottest period month

4. Rainfall is Influenced by the monsoon winds of the Indian Ocean and Bay of Bengal There are four seasons according to that. Season 1 Mid-May to October- winds originate in the southwest, bringing moisture from the Indian Ocean. – creates heavy rains on the mountain slopes and the southwestern sector of the island., including Colombo, Galle, Matara , and Ratnapura . Rainfall amount is (2,500 mm ) per month but the northeast slope receive little rain. The second season occurs in October and November, inter monsoonal months. periodic squalls occur and sometimes tropical cyclones rains to the southwest, northeast, and eastern parts of the island THE RAINFALL PATTERN

5. Season 2

6. Season 3 December to March, monsoon winds come from the northeast, bringing moisture from the Bay of Bengal. The northeastern slopes of the mountains may be inundated with up to 1,250 mm of rain during these months. Another inter monsoonal period occurs from March- mid-May, with light, variable winds and evening thundershowers.

7. Season 4

8. Typically higher in the southwest and mountainous areas and depends on the seasonal patterns of rainfall. At Colombo, daytime - above 70% all year, rising to almost 90 % during the monsoon season in June. Anuradhapura - daytime low of 60% during the inter monsoonal month of March, but a high of 79% during the November and December rains. In the highlands, Kandy's daytime humidity usually ranges between 70 and 79% Humidity

9. DRY ZONE AND WET ZONE OF SRI LANKA The mountains and the southwestern part of the country are known as the "wet zone,“ and receive ample amount of rainfall (an annual average of 2500 mm). Most of the southeast, east, and northern parts of the country comprise the "dry zone, which receives between 1200 and 1900mm of rain annually. Much of the rain in these areas falls from October to January; during the rest of the year there is very little precipitation. The arid northwest and southeast coasts receive the least amount of rain—600 to 1200 mm per year—concentrated within the short period of the winter monsoon.

10. According to Rainfall distribution in Sri Lanka has three climatic zones; "Wet Zone, "Dry Zone" and "Intermediate Zone" running between the other two zones. In differentiating of three climatic zones land use, forestry, rainfall and soils have been widely used. The Wet Zone - mean annual rainfall over 2,500 mm without pronounced dry periods.

11. The Dry Zone - mean annual rainfall of less than 1,750 mm with a distinct dry season from May to September. The Intermediate Zone receives a mean annual rainfall between 1,750 to 2,500 mm with a short and less prominent dry season. As low temperature is an important climatic factor affecting plant growth in the Wet and Intermediate Zones of Sri Lanka.

12. According to the elevation there are 3 main areas Up country-above 900m elevation Mid country- 300-900m elevation Low country- below 300m elevation Both Wet and Intermediate Zones spread across all three categories of elevation while the Dry Zone is confined to the Low-country resulting seven agro-climatic zones covering the entire island.

13. SEVEN AGRO-CLIMATIC ZONES Low country wet zone Mid country wet zone Up country wet zone Low country intermediate zone Mid country intermediate zone Up country intermediate zone Low country dry zone

14. TWENTY FOUR AGRO-ECOLOGICAL ZONES T hese seven agro climatic zones have further been divided in to 24 agro-ecological regions in 1979 . Wet Zone differentiation by differences in rainfall distribution. Dry Zone differentiation by the nature of the soil In the Intermediate Zone differentiation by rainfall distribution and soil type According to this map, there are 10 agro-ecological regions in the Wet Zone, 9 in the Intermediate Zone and 5 in the Dry Zone

15. FOURTY SIX AGRO-ECOLOGICAL ZONES Availability of more data, and advancement of GIS technology 24 agro-ecological divided into 46 agro-ecological sub-regions in 2002. The main distinguishing characteristics of each agro-ecological region are denoted by a 4-character code consisting of letters and a number. Three major climatic zones are indicated by the first upper case letter of the code (W, I and D). The second upper case letter of the code (L, M and U) denotes three categories of elevation.

16. AGRO-ECOLOGICAL REGIONS OF SRI LANKA THREE CLIMATIC ZONES Wet Zone Intermediate Zone Dry Zone SAMARY

17. 46 AGRO-ECOLOGICAL REGIONS WET ZONE Wet Zone Up Country 4 Regions Wet Zone Mid Country 6 Regions Wet Zone Low Country 5 Regions

18. Intermediate Zone Intermediate Up Country 7 Regions Intermediate Mid Country 8 Regions Intermediate Low Country 5 Regions

19. Dry Zone Dry Zone Low Country 11 Regions

20. Thank you