a Polytechnic School/ Department of Energy, University of Antsiranana, Madagascar
b Polytechnic School/ Department of Informatic, University of Antsiranana, Madagascar
Human being intensify global warming as we are the reason for higher temperature level and lower precipitation rate. Phenomena such as flood and drought are just few consequences of climate change. This sudden change affects health and wellbeing of mankind. In this paper, the analysis of outdoor climate and forecast on precipitation and radiation intensity has been carried out in two regions of Cameroon. General Circulation Model (INCM3) and scenario A2 were used. The results show that as air temperature and radiation increase, precipitation quantity decreases. There is a great concentration of precipitation for the cooling period of year (rainy season) and the decrease of annual precipitation by the amount of 15.23mm for future period. The radiation intensity rises faster in the warm region, Douala than the wet region, Yaounde. Meanwhile, in wet region, precipitation's concentration decreases faster than that of warm region. Moreover, the analysis of all data show that radiation increases 5% every year in wet and hot climate, Douala.
Keywords: climate change, precipitation, radiation, scenario, equatorial area
The global awareness about climate change is now a fact some. Long confined to the scientific community, at ecological progress, it has emerged since few years at government level with recently the signing of many protocols. The main effect of climate change may be the increase of earth's temperature which is called global warming. Increasing global surface temperatures are very likely to lead changing in precipitation, sunshine and atmospheric moisture. A warmer atmosphere can hold more moisture, and globally water vapour increases of 7% for every degree centigrade of warming. How this will translate into changes in global precipitation is less clear cut but the total volume of precipitation is likely to increase of 1-
2. Materials and methods
2.1 Study case
The study area is constituted of five climatic zones. This study was carried out in warm and wet zone in sub-
Douala is the economic capital of Cameroon, the main business centre and one of the largest cities in the country. It is the most industrialized city in central Africa. It is proven that the industries, the cars, and the buildings emit more than 60% of the total CO2 in the atmosphere. Douala's port is the main place of entry of cars not only in Cameroon, but also in Chad, and in Republic of central Africa (RCA). This city is located on the Atlantic Ocean coast, from 4◦ to 4◦4N of latitude and from 9◦40to 9◦48E of longitude, with an area of nearly 210 km2. Climate in Douala is tropical wet and hot, characterized by temperatures between 18° and 34 °C, accompanied by heavy precipitation, especially during the rainy season from June to October. The air almost always records 99% relative humidity during the rainy season, and about 80% during the dry season from October to May.
Yaounde is the Cameroon political capital and is located approximately 300 km from the Atlantic coast and enjoys a sub-
2.2 Climate data
Outdoor daily data of the last 30 years of temperature (minimum and maximum), precipitation and sunshine was taken in five meteorological stations within the study area. Some outdoor data are given in table 1. The various data are measured from 3 to 10 m in height from the ground and with a frequency of 10-
Table 1. Characteristics of location and observed climatic data for Douala and Yaounde
City Douala Yaounde Total Both types
Latitude (°N) 4.01-
Longitude (°E) 9.40-
Altitude(m) 10 600—800 -
Available data (years) 1961-
Maximum 35.7 35.5 35.7
Minimum 17.3 14.7 14.7
Relative humidity (%)
Maximum 100 98 100
Minimum 49 55 49
Maximum 7.34 7.54 7.54
Minimum 0.24 0.33 0.24
Mean yearly 3870.2 1530.7 2700.0
Area (Km2) 210 180 -
In selected weather stations, data like the relative and absolute humidity, wind speed, and evaporation are also available. The mentioned stations are selected because their administrative staff was qualified, measuring devices were reliable and also installed in a place far from any type of hindrance. Measurement errors on the temperature and relative humidity are estimated to be ± 0.1 °C and 1%, respectively.
2.3 Climate change models
In the present research, 14 GCM models and three scenarios have been used (B1, A2, A1B). The most significant input of these models is the rate of emission of greenhouse gases in the future eras. However, a precise final determination is not possible. Accordingly, different emission scenarios with a variety of gas qualities in future have been offered. On the other hand, to define the effect of global warming by means of the rise in global temperature, it was necessary to employ a LARS-
3. Results and Discussions
The variation of temperature every year in different regions is given in following figure.
Figure 1. Annual temperature increment for Douala and Yaounde
In figure 1, it is seen that the temperature varies more in hot region (Douala) than in humid region (Yaounde). The following equations have been established after analysis of the evolution of different temperatures:
So, during the next 50 years, the outdoor air temperature of Douala will can to vary of (2°C) and Yaounde of (1.4°C). According to IPCC (at the time of COP21), a variation of more than 2°C will to observe in Africa if nothing is doing now for struggle against climate change.
Figure 2 showed the comparison of the observed and estimated annual mean precipitation and radiation. The average and standard deviation values of both observed and estimated data for the period 1985-
The above figures also show a fast increase of radiation in tropical region (Douala) compare to equatorial climate (Yaoundé). Precipitation decreases rapidly in tropical region.
Figure 3 shows simulated precipitation with the observational data in Douala. We can observe that the precipitation varied according to the periods. In the past (1975-
In figure 5 between 2040 and 2065, the radiation should be from 3.8 to 6.8 Kwh/m2 (standard deviation, SD=0.93), with 4.72 Kwh/m2, as average during all this period. Moreover, between 2010 and 2035, radiation varied from 3.4 to 6.4 Kwh/m2 (SD=0.47), with an average of 4.41 Kwh/m2, Meanwhile, between 1985 and 2000, radiation varied from 3.2 to 5.3 Kwh/m2 (SD=0.67). An analysis of all the data showed that radiation increases of 5% every year in wet and hot climate(Douala). In equatorial climate (Yaounde), see figure6, radiation is also very important, particularly in dry season from November to March. Between 1975 and 2000, sunshine varied from 4.2 to 5.6 Kwh/m2 (SD=0.51), with average of 4.71 Kwh/m2. On the other hand, 5.3 Kwh/m2 will be the average for the period (2010-
The figures (7, 8 and 9) showed the frequency of precipitation during three periods in different cities. Between 1975 and 2000, the months with the most rain are July (19.97%), August (17.99%), September (14.37%) and October (10.35%) in Douala, meanwhile, in Yaounde, intensity of rain is the highest on October (18.54%). It also rains abundantly in September (15.31%), May (12.78%) and April (11.12%). The months the least rainy are December and January with an average of 0.74% and 1.2% respectively in Douala and Yaounde. Moreover, between 2010 and 2035, the month with the most rain staying July and October for Douala and Yaounde, but with a decrease of 3% and 1% compare to last period (1975-
The rate shall be stay higher on October. Figures 10, 11 and 12 show frequency of radiation on three periods studied. January, February and December were and will be still the months the hottest in the two regions (Roshan et al., 2014), have rather found an increase of annual precipitation by the amount of 20.62mm for future period.
This result shows that the consequences of climate change vary according to regions and their geographic situation. In (2040-
This research investigates and predicts the intensity of precipitation and sunshine of cities in Cameroon. The underlying data (the minimum, maximum temperature minimal, precipitation and sunshine) is collected from five weather stations in Cameron for past 30 years. The results were analyzed, interpreted, and integrated. It is concluded that in the past (1975-
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