Summary
In the Northern Summer, Kenya is located under the influence of the divergent Indian monsoon flow, and therefore is dry except for two separate areas: the coastal strip and the western regions. Analysis of daily rainfall data for June–September 1982 to 1988 has revealed that, although there are many distinct rainfall events between the two regions, an out-of-phase relationship is also evident, rain on the Coast being frequently accompanied by a drop in the precipitation over the Rift Valley area. It is shown that two types of wind forcing accompany these patterns. Alternating westerly and easterly anomalies at the 700 hPa level are associated with persistent wet and dry conditions (respectively) in western Kenya, and the opposite along the Coast. Large speed increases of the cross-equatorial low-level jet over Mombasa are followed by short rain spells in this latter region. These observations are thought to reflect the importance of an influx of moist unstable air from the west, linked to the West African monsoon, to ensure heavy rainfall over the Highlands. Variations in the low-level jet speed, which cannot be easily followed downstream, also have a significant, but less persistent impact on rainfall in the two regions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Anyamba, E. K., 1983: On the monthly mean lower tropospheric circulation, and the anomalous circulation during the 1961/1962 floods in East Africa. M.Sc. thesis, Department of Meteorology, Nairobi University, Kenya. 240 pp.
Anyamba, E. K., 1988: Some aspects of the origin of rainfall deficiency in East Africa.WMO, T.M.R.P. Report Series 28, 196–198.
Anyamba, E. K., Kiangi, P. M. R., 1985: Mean motion field in East Africa at the level of the East African low level jet core.Arch. Met. Geoph. Biocl., Ser. B 36, 29–41.
Bannon, P. R., 1979: On the dynamics of the East African Jet.J. Atmos. Sci. 36, 2139–2168.
Bärring, L., 1988: Regionalization of daily rainfall in Kenya by means of common factor analysis.J. Climatol. 8, 371–389.
Beltrando, G., 1990: Variabilité interannuelle des précipitations en Afrique orientale (Kenya, Ouganda, Tanzanie) et relations avec la dynamique de l'atmosphère. Ph. D. thesis, Université d'Aix-Marseille II, 223 pp.
Beresford, A. K. C., 1982: Recent climatic change in East Africa: lake levels, rainfall and upper air flow. Ph.D. thesis, University of East Anglia, Norwich, U.K.
Cadet, D. L., Besbois, M., 1981: A case study of a fluctuation of the Somali Jet during the Indian Summer Monsoon.Mon. Wea. Rev. 109, 182–187.
Camberlin, P., 1995: June–September rainfall in north-eastern Africa and atmospheric signals over the Tropics: a zonal perspective.Int. J. Climatol. 15, 773–783
Davies, T. D., Vincent, C. E., Beresford, A. K. C., 1985: July–August rainfall in West-Central Kenya.J. Climatol. 5, 17–33.
Desai, B. N., Rangachari, N., Subramanian, S. K., 1976: Structure of low-level jet stream over the Arabian Sea and the peninsula as revealed by observations in June and July during MONEX 1973 and its probable origin.Indian J. Met. Hydrol. Geophys. 27(3), 263–274.
Findlater, J., 1968: The month to month variation of mean winds at low level over Eastern Africa. EAMD Technical Memorandum n° 12, 27 pp.
Findlater, J., 1969: A major low-level air current near the Indian Ocean during the northern summer.Quart. J. Roy. Meteor. Soc. 95, 362–380.
Findlater, J., 1972: Aerial explorations of the low-level cross-equatorial current over Eastern Africa.Quart. J. Roy. Meteor. Soc. 98, 274–289.
Findlater, J., 1974: An extreme wind speed in the low-level jet stream system.Meteor. Magazine. 103, 201–205.
Findlater, J., 1978: Observational aspects of the low-level cross-equatorial jet stream. In: Krishnamurti, T. N., (ed)Monsoon Dynamics. Basel: Birkhäuser, pp. 1251–1262.
Hills, R. C., 1979: The structure of the inter-tropical convergence zone in equatorial Africa and its relationship to East African rainfall.J. Inst. Brit. Geogr. 4, 3, 329–352.
Kiangi, P. M. R., Anyamba, E. K., 1987: Some monsoons of East Africa: why the low rainfall productivity? Proc. of the First Technical Conf. on Meteor. Research in Eastern and Southern Africa, KMD, Nairobi, 6–9 Jan. 1987, 61–70.
Kiangi, P. M. R., Temu, J. J., 1988: Equatorial westerlies in Kenya: are they always rain laden?WMO, T.M.R.P. Report Series 28, 212–213.
Kinuthia, J. H., 1992: Horizontal and vertical structure of the Lake Turkana jet.J. Appl. Meteor. 49, 1248–1274.
Kinuthia, J. H., Asnani, G. C., 1982: A newly found jet in North Kenya (Turkana Channel).Mon. Wea. Rev. 110, 1722–1727.
Nakamura, K., 1968: Equatorial westerlies over East Africa and their climatological significance.Geographical reports of Tokyo Metropolitan University 3, 43–61.
Nganga, J. K., Masumba, B. A. N., 1988: The land and sea breeze circulation and its influence on rainfall over Kenya's coastal areas.WMO, T.M.R.P. Report Series 28, 220–221.
Ngara, T., 1977: Some aspects of the East African low-level jet stream. M.Sc. thesis, Department of Meteorology, University of Nairobi, Kenya. 97 pp.
Nyenzi, B. S., 1988: Mechanisms of East African rainfall variability. Ph.D. thesis, Florida State University, Tallahassee, U.S.A. 184 pp.
Ogallo, L. J., 1985: Climatology of rainfall in East Africa. WMO Conference on GATE, WAMEX, Trop. Met., 10–14 Dec. 1985, Dakar.WMO T.M.R.P. 16, 96–102.
Ogallo, L. J., 1988: Relationships between seasonal rainfall in East Africa and the Southern Oscillation.J. Climatol. 8, 31–43.
Ogallo, L. J., 1989: The spatial and temporal patterns of the East African seasonal rainfall derived from principal component analysis.J. Climatol. 9, 145–167.
Ojany, F. F., Ogendo, R. B., 1988:Kenya: A Study in Physical and Human Geography. Nairobi: Longman Kenya, 225 pp.
Okeyo, A. E., 1982: A two-dimensional numerical model of the lake-land and sea-land breezes over Kenya. MSc. thesis, Nairobi University, Kenya. 244 pp.
Okoola, R. E., Asnani, G. C., 1982: Pressure surge in South-West Indian Ocean in relation to onset and activity of summer monsoon in South India. Intern. Conf. on the Scient. Results of the MONEX, Denpasar, Indonesia, 26–30 Oct. 1981. 1–13.
Parthasarathy, B., Kupa Kumar, P. M. R., Munot, A. A., 1991: Evidence of secular variation in Indian Monsoon rainfall circulation relationships.J. Climate 4(9), 927–938.
Tadesse, T., 1994: Summer monsoon seasonal rainfall of Ethiopia in ENSO episodic years. Proc. Int. Conf. on Monsoon Variability and Prediction, ICTP, Trieste, Italy, 9–13 May 1994. WMO, TD n° 619, 48–55.
Van de Boogaard, H. M. E., Rao, G. V., 1984: Mesoscale structure of the low-level flow near the Equatorial East African Coast.Mon. Wea. Rev. 112, 91–107.
Author information
Authors and Affiliations
Additional information
With 7 Figures
Rights and permissions
About this article
Cite this article
Camberlin, P. Intraseasonal variations of June–September rainfall and upper-air circulation over Kenya. Theor Appl Climatol 54, 107–115 (1996). https://doi.org/10.1007/BF00865153
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00865153