Cover Image
close this book Measuring drought and drought impacts in Red Sea Province
close this folder 3. Drowght, food stress, and the flood and rainfall record for Red Sea Province. Roy Cole
View the document Summary
View the document Introduction
View the document Precipitation In Red Sea Province
View the document Flood and rainfall records: problems and possibilities
View the document A definition of drought
View the document The flood record
View the document Drought and the flood record
View the document The rainfall record
View the document Drought and the rainfall record
View the document Conclusion
View the document Discussion
View the document Limitations of the study
View the document References
View the document Appendix 3.1. Annual floods for nine khors In Red Sea Province and Khor Gash in Kassala Province.
View the document Appendix 3.2. Annual flood 2 scores for nine khors in Red Sea Province and Khor Gash in Kassala Province.
View the document Appendix 3.3. Annual rainfall in mililmetres for 19 gauging stations in eastern region, Sudan.
View the document Appendix 3.4. Annual rainfall z scores for 19 gauging stations in eastern

Precipitation In Red Sea Province

Precipitation in Red Sea Province occurs in two seasons, summer and winter. Summer rainfall (July to September) occurs as a result of the northward movement of the Inter-Tropical Convergence Zone (ITCZ). This 600 kilometre wide zone of humid air moves seasonally across the entire Sudano-Sahelian zone of Africa and is the source of the precipitation in that zone; the heaviest rainfall occurs in the southern parts of the Sudano-Sahel and the least in the southern Sahara Precipitation during this season falls throughout the interior of the province to approximately the central ridge of the Red Sea Hills from the southern districts of Red Sea Province to central Halaib District in the north.

Coastal Red Sea Province, generally dry throughout the summer season, receives rainfall in the winter months from November to February and heavy dew up until the end of April. This season of precipitation is caused by the northeast Trade Winds (called the harmattan in West and Central Africa). They are dry winds that transport water vapour from the Red Sea and deposit it in the form of rain and dew along the coast and mountain areas of Red Sea Province. These winds blow all year long but achieve their maximum during the winter months. Consequently, rain or dew may occur at any time of the year along the coast in Red Sea Province.

The effect of the Red Sea Hills on precipitation in both seasons is important. The Hills increase the precipitation during the summer season by forcing moist air into cooler, upper elevations where it condenses and falls as rainfall or is deposited on the ground as dew. Regarding the coastal zone, it is doubtful whether there would be any precipitation during the winter season without the lifting effect of the mountains. Areas located in a central position along the north-south axis of the Red Sea Hills as well as the khors flowing to the coast or interior fed by these hills benefit from two rainy seasons. In the summer season heating by the sun can cause local instabilities (thermal convection), uplift of air parcels, and rainfall (see ElTom 1989).

Mahdi Amin El-Tom (1975) distinguishes five precipitation zones in Red Sea Province. Two periods of rainfall can be distinguished: November to January and July to September.

Table 3.1. El-Tom's rainfall zones for Red Sea Province.

Area

Rainy Season

Coastal Eritrea to Khor Arba'at delta

November to January

Coastal Khor Arba'at delta to Halaib

October

Mountain and coastal northern Red Sea Hills

November

Mountain northwest

July to August

Interior southwest

July to September