KENYA’s CLIMATE

BY

Mary Kilavi

Kenya

Position

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Kenya lies astride the equator, bounded by

longitudes 34oE to 42oE and latitudes

5.5oN to 5oS and hence enjoys a tropical

climate. It is hot and humid at the coast,

temperate inland and very dry in the north

and northeast parts of the country

Topography

1650 1350 1050 750 675 600 525 450 375 300 225 150 135 120 105 90 75 60 45 30 15 0

-2

2

34 38 42

Longitude (°E)

-4

36 40

Elevatio

n (m

etres)

4

0

Lati

tud

e (°

N)

It has complex

topography eg.

large lakes, Great

Rift Valley and

snow-capped

mountains which

influence circulation

and modify climate

of various parts of

the country.

INTRODUCTION

Kenya experiences two rainy seasons (bimodal), namely the long-rains (March to May) and the short-rains (October to December) seasons as the Inter-Tropical Convergence Zone (ITCZ) migrates through the equator from south to north, and vice versa lagging the overhead sun by about 3 to 4 weeks. However, some stations in the western and central parts of the Rift Valley experience tri-modal rainfall pattern

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Mean seasonal rainfall distribution during MAM over Kenya

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Mean seasonal rainfall distribution during OND over Kenya

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INTROD CONTI..

The western parts of the country do realise significant rainfall during the period June-August associated with influences from the tropical south Atlantic and incursions of moist Congo air mass when the meridional branch of ITCZ has maximum eastward displacement over the region.

Coastal is also wet during this period.

The January to February period is generally dry over most parts of the country.

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Mean seasonal rainfall distribution during JJA over Kenya

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65

194

104

514

565

12

143

85

0

26

18

22

621

702

24

5 649

319

486

328

47

157

78

8

353

4

264

48

70

286

457

67

17

165

359

220

99

128 714

74

42

206

28

10 BARA

COLCH

DAGO

ELDORET

ELGON

ELWAK

EMBU

GALO

GARB

GARI

ILERET

ISIOL

KAIS

KAKA

KATUMANI

KATZE KISI

I

KISUM

KITALE

LAMU

LODW

LOKICH

LOKOM

MAKI

MALI

MAND

MARL

MARS

MERU

MOMB

MONI

MOYA

MUTO

NAIV

NAKURU

NANY

NARO

NYER OLEN

G THIKA

TODEN

VANGA

VOI

WAJIR

34E 35E 36E 37E 38E 39E 40E 41E 42E

5S

4S

3S

2S

1S

0

1N

2N

3N

4N

5N

0MM

50MM

100MM

150MM

200MM

250MM

300MM

350MM

400MM

450MM

500MM

550MM

600MM

650MM

700MM

Mean annual total rainfall distribution over Kenya

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Annual Rainfall variability in Kenya

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Temperatures

Generally:

• Highest temperatures: January to Feb

• Lowest temperatures: June to August

The Lake Victoria Basin, Highlands west of the Rift Valley, Central and South Rift :

Max 22°C ( July) - 31°C (Feb)

Min 9°C (Sep) - 14 °C (April)

Narok and Nyandarwa counties experience the experience the lowest average minimum temperature in the country of about 6°C which on a number of occasions has dropped to close to freezing point

•

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Temperatures

The Northwestern counties: • Max > 35°C throughout much of the year except in June and July when

the maximum temperatures drop slightly to less than 34°C. The average High average minimum temperatures: 22°C - 25°C

Central highlands including, Nairobi area:

• Max 21°C (July) - to 24°C (Jan)

• Min 10°C (Jan)- 16°C ( April).

Northeastern counties:

• Maximum temperatures are very high all year round (> 34 °C)

June to August falls slightly to between 31°C to 33°C.

• The minimum temperatures average between 24°C during the hot months and 21°C during the cooler months except for points at high elevation like Marsabit

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Temperatures

Southeastern lowlands counties:

• These counties are characterized by hot temperatures and extreme

evaporation. Maximum temperatures range from 26°C in July to 31°C in March. Minimum temperatures range from 14°C in July to 18°C in March

The Coastal counties : • Generally hot with temperatures exceeding 22°C throughout the year.

• Max 27°C (July)- 33°C (March)

• Min 22°C( July) –25°C (April)

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The interannual variability of rainfall in Kenya results from complex interactions of forced and free atmospheric variations which include-

SST forcing,

Land-surface forcing,

Monsoon and trade winds,

Persistent mesoscale circulations,

Tropical cyclones,

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Subtropical anticyclones,

Easterly/westerly wave perturbations,

Extra-tropical weather systems,

Jet streams,

El Niño / Southern Oscillation (ENSO), QBO etc.

First example of a teleconnection between SSTs and

rainfall in East Africa:

El Niño Southern Oscillation (ENSO)

El Niño: Warm Episode Relationships (December - February)

60

40

20

0

-20

-40

-60

0 60 120 180 240 300

Longitude (°E)

La

titu

de

(°

N)

60

40

20

0

-20

-40

-60

0 60 120 180 240 300

Longitude (°E)

La

titu

de

(°

N)

First example of a teleconnection between SSTs and

rainfall in East Africa:

El Niño Southern Oscillation (ENSO)

La Niña: Cold Episode Relationships (December - February)

Second example of a teleconnection between SSTs and

rainfall in East Africa:

The Indian Ocean Dipole (IOD)

Positive Dipole Mode: (May - October)

Second example of a teleconnection between SSTs and

rainfall in East Africa:

The Indian Ocean Dipole (IOD)

Negative Dipole Mode: (May - October)

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Trends

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Minimum Temperature trend for Kisumu

Trend line equation:y = 0.0189x + 16.534

15.5

16.0

16.5

17.0

17.5

18.0

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

Time in years

Tem

pera

ture

(°C

)Increasing significant

temperature over most

locations

Rainfall decreasing during

MAM and increasing during

DJF over some locations

THANK YOU

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