Fluid and Energy Laboratory, University of Antsiranana, Madagascar
The warming of the planet is a big threat to humanity. The consequences vary depending on the geographical position of each country. Anthropogenic activities continue to emit potential greenhouse gases (GHG) into the atmosphere leading to a warmer climate. According to the World Meteorological Organization, Madagascar Island is one of the world's most vulnerable regions on earth. This research aims to study the variation in outdoor climate in some regions of Madagascar and also to assess the global warming impact on energy demands in 16 regions in Madagascar. A meticulous analysis of the current pressure of environment on human health has been completed. Several general circulation models (GCMs) (BCCRBCM2, INMCM-
Keywords: Outdoor, environment, climate change, Madagascar
Man, thanks to his intelligence, acted on the environment to improve his lifestyle. This human action on the environment has improved the lives of billions of people, but it has also changed the nature of the ecosystem. The global climate system is an integral part of all processes necessary to sustain life. In many parts of the globe, a sudden change in climate, with a high degree of heating has been observed from 1950. The consequences of global warming are many and vary from region to region (IPPC, 2007; IPPC, 2001; Zhang et al., 2007; Webster et al., 2005; Tadross et al., 2005). The consequences of this phenomenon have stayed positive in some countries of Asia and America, but in a majority of the cases, they are negative. The climate has always had a powerful impact on the health and well-
2. Materials and methods
2.1 Study area
Located between 20°00 S and 47°00 E, Madagascar is almost entirely within the tropics. It is an island in the Indian Ocean with an area of 592.000 km². It is the fourth largest island in the world. It is separated from Africa by the Mozambique Channel, about 400 km away. A mountainous spine between 1200 m and 1500 m runs through the island from north to south along its length. This geographic landform, the maritime influence and the wind condition are the cause for the very varied climatic conditions encountered on this island. There are basically two seasons in Madagascar: the dry season from May to October and the rainy season from November to April. Two short seasons, with a duration of approximately one month each, separate these two seasons. From May to October the climate is conditioned by an anticyclone to the Indian Ocean level that directs a wind regime of South-
2.2 Climatic data
In accordance with Rabefitia et al., 2008 and Tadross et al., 2008, outdoor daily data of temperature (minimum and maximum), precipitation and sunshine for the last 44 years (between 1961 and 2005) was taken in many meteorological stations. The various data were measured from 3 m to 10 m in height from the ground and with a frequency of 10-
In Madagascar, the annual average temperature is between 14°C and 27.5°C. On the coast, it depends on the latitude and ranges from 27°C in the North and 23°C in the South. The west coast is warmer than the east coast (1°C to 3°C). On the plateaus, the average annual temperature ranges between 14°C and 22°C. The average temperature reaches its minimum in July across the country; the maximum occurs in January and February for most regions, except for a few places in the Highlands and the Northwestern region, where it is observed in November. In year 2000, the level of warming in the southern part of Madagascar was more significant than in the North. The dry sequences lie on the Central Highlands and the East Coast. On the Highlands, this is due to the decline of the rainy season. The changes in precipitation in Madagascar vary from one region to another. Rainfall becomes a lot more intense on the western part. Over the past 100 years, the level of rainfall in Madagascar has shown great variability. In the southern part, rainfall increases with temperature. In the northern part, precipitation increases with decreasing temperature. The quantity of annual precipitation decreases 5% per year, except from December to February, where we noticed an increase between 3% and 8%. In East and West, a maximum of 3700 mm per year was saved and from north to south a minimum of 350 mm per year. The seasonal increase is along the same direction -
2.3 Climate change models
Many models and scenarios can be used to simulate the variation of air temperature and precipitation. In the present research, 13 GCMs (BCCRBCM2, INMCM-
2.4 Energy consumption
To quantify the real outdoor warming energy in different seasons the methodology of IPPC, 2001 was used. This method is based on Eq. (1), which expresses the energy consumption required to maintain a comfortable outdoor environment. This equation depends on the ventilation mass flow rate, that is, the increase or decrease in outdoor air enthalpy required in terms of the desired indoor conditions, as shown in Eq. (2), and the period of time during which this difference exists.
3. Results and Discussions
The original temperature increment had been assessed at the start of 1950 and 1970, which represented the years where the air temperature started to increase in the North and South of Madagascar. It was found that precipitation increased, while the temperature decreased in the North. However, in the South, precipitation increased with temperature. The minimum and maximum temperatures did not always remain constant. Sometimes, they showed a similar trend. Furthermore, the maximum temperature was changing faster than the minimum temperature. The minimum and maximum annual temperature in the northern region increased from 0.4 to 3.7°C and ranged between -
The Mean Partial Vapour Pressure difference is greater in the months of June, July and August, in all climate zones, except the humid zone. This may be because this region of Madagascar is regularly affected by cyclones and storms. A standard deviation (SD) of 112 is noticed in the semi-
Figure 3 shows the outdoor air enthalpy in Madagascar in different climates. In the arid climate, in year 1975, the enthalpy varied from 44 to 65 KJ/Kg, with SD = 7.4. On the other hand, in the years 2000 and 2025we saw different mean values of enthalpy -
Figure 4 shows the enthalpy differences between outdoor conditions and ideal outdoor ambience in some regions of Madagascar. In the arid climate, the enthalpy differences decrease from January to May. Between June and September, the energy demand is very weak, but by October this energy demand increases very fast, to reach 4.8 KJ/Kg in December. Globally, in 1975, the mean monthly enthalpy differences were 0.43 KJ/Kg. After 25 years (in year 2000), the mean monthly enthalpy difference was already around 1 KJ/Kg; in 2025, if the pressure on environment stays the same, the mean monthly enthalpy difference will be 1.671 KJ/Kg. In a transitional climate, the enthalpy difference should be the highest in 2025. It will be same between June and September, with no energy demand, however in October, the enthalpy difference will increase till December. In addition, in a humid climate (see Figure 5), during April the enthalpy difference will increase up to December, after which it will seem to decrease.
Figure 6 shows the humidex index increment in several types of climate in Madagascar. It was found that in transitional tropical climate regions (Figure 6a) and humid tropical climate regions (Figure 6b), the environment was uncomfortable, because the humidex value was between 30 and 40. In a tropical transitional climate, the environment was acceptable between January and May, and then between September and December. During these months, the humidex index varied from 14 to 20. In June, July and August, the environment was uncomfortable as it was "too cool". In all types of climate, the humidex value would be the highest in the year 2025. It could be a consequence of global warming. In fact, the humidex value changed the functions of air temperature and relative humidity. For air temperature greater than 27°C and relative humidity above 60%, the middle uncomfortable, because of the high degree of heat. At the same humidity values, if the air temperature ranged from 10°C to 18°C, the medium would still be uncomfortable, but this would be because of the very high degree of cold. The outdoor environment would be really uncomfortable in the future, according to National Weather of Madagascar (Tadross, 2008). In 2099, the air temperature would have increased from 0.5°C to 3°C, with an average rise of 0.5°C every 20 years. As for rainfall, annual rainfall would decrease to 5% at the end of the century in the whole island. It has nevertheless provided an increase of 5% to 10% of precipitation between December and February. Overall, the environment is acceptable or comfortable, when the air temperature ranges between 22°C and 26°C, with humidity between 35% and 65%. This comfort range established for different types of climate in Madagascar is very close to that established by some standard norms (ISO7730, 2006; ISO 10551, 2002; ASHRAE55, 2004), (air temperature from 23°C to 26°C and relative humidity between 30% and 60%).
In all the regions, during the rainy season, the humidex concentration increases, however, in winter (in Central Madagascar), the humidex concentration is very low due to a very low degree of humidity and very high air speeds, sometimes reaching 6.5 to 8.0 m/s (Kameni et al., 2015).
In this research, we have studied the variation of outdoor climate in some regions of Madagascar and also assessed the global warming impacts on energy demands in 16 regions in Madagascar. Several GCMs were combined with several scenarios to screen the Climate Change outside and to assess the state of comfort of the environment. Finally, we used the General Circulation Model INCM3 combined with scenario A2 to carry out the forecasting. The cooling energy demand will increase to 10% over the next 25 years in 90% of the studied regions in Madagascar. The partial vapour pressure values are not stable, sometimes they reach 250 pa in a semi-
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