Current Issue

Baghdad, the capital governorate city, is located in central Iraq including surrounding metropolitan area. It extends along both banks of the Tigris River, see Fig. 1 and occupies an area of 894.3 km² and is in the heart of ancient Mesopotamia. The terrain of Baghdad and its surrounding areas is a roughly flat and low-lying land adjacent to a stream alluvial plain (Al-Jiboori et al., 2020). Geographical coordinates are of latitude 33°12′-33°29′ N, longitude 44°10′–44°30′ E and 34 m above mean sea level. Baghdad had a population of a 6.974 million in 2019 and forms one of the populous urban agglomerations of the Middle East.

From build-up area of about of about 10 km² at the beginning of the 20th century, Baghdad has expanded into a bustling metropolis with suburbs spreading north and south along the river and east and west onto the surrounding plains (Britannica.com/place/Baghdad, 2020). Baghdad has about 12 bridges spanning the river-joining the east and west of the city and has multiple small Mesopotamian Marshes. It has a prosperous and sophisticated city whose rich cultural life can be measured by its many museum universities and institutes and by myriad scholars and literature. The architecture of the city ranges from traditional two- or three-story brick houses to modern steel, glass and concrete structures. The Köppen climate classification for Baghdad features is BWH, semiarid, extremely hot, dry summer and damp winter (Roth, 2007). Baghdad has an average temperature 25°C and average rainfall per year is approximately 140 mm with no rain at summertime. The readers can refer to the reference (Al-Jiboori et al., 2020) for more details.

Based on Equation (2) adapted in this paper, the resultant binary images were extracted with positive values for the built-up and barren pixel and negative values for non-urban-up (or other land cover types) these pixels are mapped automatically for each year of 2008, 2013 and 2019, as shown in Fig. 4. A comparative analysis of BUI extraction in these years is made to monitor and detect the land change in Baghdad city. Total number of pixels is 993743 (each pixel is 30 m 30 m in dimension) the changes in land use/land cover in terms of BUI are ultimately increased during the period 2008-2019. The occupied areas by built-up and nonbuilt-up with their ratios respect to the total area are reported in Table 2.

Fig. 4. 
Built-up area extraction in terms of built-up index for (a) 2008, (b) 2013 and (c) 2019.

From Table 2, built-up areas and their ratios are increased from 621.7 to 727.3 km² with adding 105.6 km² with ratio 11.9% during the period study. The great addition in built-up area (84.6 km² with 9.5%) occurred from 2008 to 2013. Inversely, there is reduction in nonbuilt-up area from 272.6 to 167 km² from 2008 to 2019 with large ratio in 2013. In general, eastern side of Baghdad has more resident houses with high populous density than that for the opposite site. In 2019, the extension in eastern side of Baghdad as shown in Fig. 4c is approximately limited because of oldest area with high populous density. The evolution patterns in urban agglomerations for western side in 2019 can reveal the urban footprints since 2008. This can visualize the spatial expansion of this side by increasing the traffic infrastructure, paved roads, new settlements, vertical resident groups, gardens inside the houses and large supermarket malls. In both sides, so many small barren lands have been transformed to building such as settlement, small stadiums for footballs especially in northern part of Baghdad where so many vegetation have been altered to built-up since 2013. This occurred due to the continuous increasing in populous growth rates as will be showed later in Table 3subsection 4. 3.

The accuracy of each BUI map was spatially assessed by selecting many point samples and comparing them with the ground truth using a field knowledge and Google Earth at main places, and road intersections. For the assessment of accuracy at the entire area, nearly 100 pixels of the objects were identified by visual interpretation from the mapped results. These pixels were distributed as 70 pixels for the built-up land and 32 pixels for the other land cover (nonbuilt-up). The result of these verification points was 63 and 28 were correctly mapped as urban and nonurban area with overall accuracy of 94%.

In this subsection, it discusses the impact of expanded and increased area of built-up index over time for the years 2008, 2013 and 2019 on the intensity of CHUI as described in subsection 4.1. Before explaining this, it should notice that BUI areas strongly depended upon land uses produced by numerous number of individuals in any urban city. Therefore, statistics of the population and population density (in simple terms, defined as the midyear number of population living in a land area per square kilometer (Clark, 1951)) were added to achieve this analysis, whereas the relationship between these statistics and urban heat island intensity has been fixedly documented by several researchers (Golroudbary et al., 2018; Oke, 1973). Population density (PD) of Baghdad were computed from the database of population available at the central statistical organization, Planning of Ministry.

Using seasonal means of CUHI (i.e. ΔT_u-r) reported in the previous subsection, annual means of ΔT_u-r with their SD were calculated at each year. The results for CUHI intensity and its dependency on both BUI areas and PD were investigated for the years of 2008, 2013 and 2019. All of the values of these results are reported in Table 3. The linear increasing in population and PD was also associated with the corresponding increase in the areas of BUI. This means that the continuous increasing in PD and BUI with the years shown in Table 3 explores positive extreme signs of urbanization warmth, especially in the eastern part of the city which describes with high PD (Alsamaw and Zboon, 2009).

Also in the recent decade, most ground housing units with more than 100 m² have been divided to small ones even small gardens inside the houses which have been also transformed settlement units. The city’s population growth was not only causing exceeding the BUI areas but also rising the level of anthropogenic heat emissions. All of the increases produced warmth in the air canopy layer of Baghdad with annual mean of ΔT_u-r=1.5°C for both years 2008 and 2013, but more seriously in 2019 with 2.5°C.

Now we attempt to study the physical behaviors among the three parameters PD, BUI and CUHI (or ΔT_u-r) with falling out the time (years). The values of these parameters were drawn together in 3D graph presented in Fig. 7. The relations (ΔT_u-r vs. PD), (ΔT_u-r vs. BUI), and (PD vs. BUI) show nonlinear increases of ΔT_u-r dependent on the human modifications in PD and BUI. Dashed-solid line represents the values resulting from PD and BUI (i.e. ΔT_u-r is function of both PD and BUI: CUHI=ƒ (PD,BUI)). The SD values denoted by the red vertical lines shows the largest diffusion in CUHI values (±0.9°C) from the seasonal means for the last 2019 year. In concluding, the continuous population growth came from various parts of Iraq (i.e. internal immigration) and even the numerous numbers of new births has been a mixed effect on local thermal climate of canopy Baghdad environment.

Fig. 7. 
Variation of ΔT_u-r with PD and BUI area. The lines with dots , and are ΔT_u-r vs. BUI, ΔT_u-r vs. PD and PD vs. BUI, respectively.