Influence of Orography onRainfall Distribution and Water

Resourcesin Guadeloupe

Marc Morell - Institut de Recherche pour le DéveloppementPhilippe Palany – Météo-France

Dominique Rossignol, ORSTOM ✚

CARIBSAT Project

Berlin, EMS 2011

Canal des Saintes – Ouragan David - 28/08/1979 - M. Morell

WWW.CARIBSAT.COM

Summary

IntroductionThermic and Orographic PhenomenaMonthly and Yearly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water ResourcesClimate Changes EffectsComments

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Introduction – Location

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Caribbean sea

Guadeloupe

Landsat Satellite Image of Guadeloupe islands

Introduction - Geography

La Soufrière

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Introduction – Climate

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Monthly averages of temperatures and rainfalls

in Le Raizet (source Meteo-France)

Rainfalls Mini. Temperatures

Maxi. Temperatures

Cliamte changes effects

Berlin, EMS 2011 Hurricane Ivan – 7 September 2004

Guadeloupe

Introduction – Main studies

1978 – ORSTOM - Monographie des ressources en eau de surface de la Guadeloupe, Chaperon P. & al.

1990 – ORSTOM – Travaux de Dominique Rossignol, Physicien de l’Atmosphère & al.

1994 – ORSTOM – La Guadeloupe au fil de l’eau, Marc Morell & al.

1996 – METEO-France – Le régime pluviométrique de la Guadeloupe, N. Bleuse & C. Mandar

2010 – METEO-France – Analyse des sécheresses en Martinique, Philippe Palany, Projet CARIBSAT

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Introduction – Networks and Data ORSTOM, started to implement a

rainfall recording network in Basse-Terre mountains in 1960’

ORSTOM has completed its network with electronic stations equiped with ARGOS transmitters in 1984

In 1990, 35 stations were managed by ORSTOM, 2/3 of them at an elevation higher than 300 m

In 1990, around 4500 years/stations of rainfall daily data were available on Guadeloupe archipelago La Soufrière, Dent de l’Est – R. Calvez

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Summary

IntroductionThermic and Orographic PhenomenaMonthly and Yearly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water Resources AssessmentClimate Changes EffectsComments

Berlin, EMS 2011

Landsat Satellite Image of Guadeloupe islands

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Thermic and Orographic Phenomena

Thermic

Orographic

Thermic and Orographic Phenomena

Transect from Capesterre to Vieux-Habitants

Rainfall Gradient for 1 km :from 150 mm Upwind to 600 mm

Downwind

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11 m

EastWest

1 m 2.5 m

Short time steps Intensities

Nb Hours per year = 1,58 Altitude + 152 R2 .95 Yearly rainfall = 6,45 Altitude + 1234 R2 .92

100 200 300 400 500 600 700 800 900 1000

1100

1200

1300

1400

1500

0

2000

4000

6000

8000

10000

12000

Nb hoursYearly average

Altitude

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Summary

IntroductionThermic and Orographic PhenomenaYearly and Monthly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water Resources AssessmentClimate Changes EffectsComments

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Yearly and Monthly Variability

Annual precipitation distribution Berlin, EMS 2011

20 km

Soufrière

Yearly and Monthly Variability

7 homogeneous climatic areas were defined by ORSTOM in 1984

Regulation of Rainfall regimes by orographic effect on interannual variability on seasonal distribution

Homogeneous areas

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Yearly and Monthly VariabilityRatio Humid /Dry Year - Frequency

1/10

7 homogeneous climatic areas were defined by ORSTOM in 1984

Regulation of Rainfall regimes by orographic effect on interannual variability on seasonal distribution

Interannual Variability

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1.3

1.6-1.7

1.81.6-1.7

1.4-1.5

1.6-1.7

Yearly and Monthly Variability

7 homogeneous climatic areas were defined by ORSTOM in 1984

Regulation of Rainfall regimes by orographic effect on interannual variability on seasonal distribution

Seasonal distribution

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Yearly and Monthly VariabilityRatio Maximum/Minimum Monthly

Rainfall 7 homogeneous climatic

areas were defined by ORSTOM in 1984

Regulation of Rainfall regimes by orographic effect on interannual variability on seasonal distribution

Seasonal distribution

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Summary

IntroductionThermic and Orographic PhenomenaMonthly and Yearly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water Resources AssessmentClimate Changes EffectsComments

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Daily and Hourly Analysis

Maximum thermic effect on the North of Basse-Terre with pick in the early afternoon

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Daily and Hourly Analysis

Maximum thermic effect on the North of Basse-Terre with pick in the early afternoon

Maximum orographic effect on the top of the mountains in Basse-Terre with occurrence of rainfall during the night explained by the decrease of the temperature of the top of the clouds

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Summary

IntroductionThermic and Orographic PhenomenaYearly and Monthly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water Resources AssessmentClimate Changes EffectsComments

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Short time steps Intensities

Statistical Analysis of Intensities in one minuteImportant contribution of low intensities (< 10

mm/h) in the total amount of rainfall in mountainsIncreasing contribution of higher intensities on

the slopesNo orographic effect on the heaviest intensities

clearly linked with convective thermic phenomenaThe strongest rainfall intensities for duration from

5 mn to 3 hours are not related to hurricanes

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Short time steps IntensitiesInfluence of the wind on

the measurement of rainfall

Hurricane David – 28/08/1979 – M. Morell

Incidographe – Marc Morell 1985

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A

Short time steps Intensities

Duration 2 years 10 years 100 years6 mn 12 17 2315 mn 22 31 4230 mn 33 49 691 hour 45 63 856 hours 78 123 17912 hours 92 157 2391 day 105 189 294

Rainfall in mm in Le Raizetfor various time periods

Statistical analysis - METEO-France

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Summary

IntroductionThermic and Orographic PhenomenaMonthly and Yearly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water ResourcesClimate Changes EffectsComments

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Water Resources

ORSTOM Hydrometric network in Basse-Terre

Chutes du Carbet - M. Morell

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Basse-Terre = 95% of the WR ofthe Guadeloupe island

Water Cycle Balance

Water Cycle Variables

%

Rainfall 100 . Evapotranspiration

16

. Runoff 84Runoff 100

. Flash Floods 70

. Delayed flows 10 . Ground water 20

Yearly rainfall basis : 5000 mm

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Summary

IntroductionThermic and Orographic PhenomenaYearly and Monthly VariabilityDaily and hourly analysisShort time steps intensitiesWater Cycle and Water Resources AssessmentClimate Changes EffectsComments

Berlin, EMS 2011

Climate Changes effects

Climate changes will increase the vulnerability of the ecosystems and human population of the tropical islands : Anthropogenic activities (pollution, sedimentation),

increasing temperatures and acidification of ocean are impacting the marin ecosystems (mangrove destruction, coral bleaching, etc.)

Rising sea levels and disappearance of the coral reefs will lead coastal erosion processes, salt water intrusion, etc.

More frequent and longer dry periods and more frequent and intense meteo-marin events are expected during the next decades

Decreased water resources and higher atmosphere temperatures (2 to 3° in 2050) will induce serious consequences on agriculture, biodiversity and sanitary issues (vector diseases), etc.

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Climate Changes effects

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Increasing Number of Tropical Storms on North Atlantic Ocean 1966-2007

Source NHC Miami, Wind speed > 63 km/h

Average : 10,4/year mini 1983 : 4 max 2005 : 27

Climate Changes effects

In 1989, Dominique Rossignol studied the relationships between El nino and QBO occurrences and the yearly rainfall variability and its seasonal distribution.

Among the main results : 90% of El Nino events are followed by severe

droughts during the “Carême”, like in 1983 and 1987, and a predictive method must be implemented

Orography and elevation are significant local modifiers of sub-regional climate change

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Comments Guadeloupe appears as an ideal laboratory for studying

the rainfall distribution in tropical islands Specific thermic and orographic effects can be

analysed Long data series are available

In this presentation, we have reported on the main achievements obtained 20 years ago when the concept of climate changes was very new

In the present context of climate changes, water resources scarcity and biodiversity conservation, it is urgent to implement some monitoring networks at Caribbean scale which will provide the scientists with all necessary data to improve the knowledge on the dynamic of the

phenomena generating rainfall and water resources, and

to give a better accuracy to the downscaling of the regional climatic change models Berlin, EMS 2011

www.CARIBSAT.com

Grand-cul-de-sac-marin – 1979 - M. Morell

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