**1.1. The climate of cities and the urban scales**

The urban climate refers to the specific climatic conditions in cities that differ from the surrounding areas, as an effect of the urban development. Urbanization tremendously changes the form of the natural landscape causing changes in the local climate, not only compared to the surrounding areas, but also inside the city. While some climatic elements differ only slightly from one city district to the other, like the precipitation for example, others differ significantly, like the temperature and the wind conditions.

In the case of conventional meteorological elements (temperature, humidity, wind, and precipitation), it is not as easy to establish the magnitude of modulation of the atmospheric boundary layer by a city, and it is even more challenging to assign causes for the observed changes. One of the main difficulties is the geographical setting of cities. The setting of a city is barely random and settlements are usually developed for specific reasons. Riverbeds, for example, offered good communications in earlier years; coastal cities were developed near natural harbors; others near to natural resources. In many developed countries, settlement sites were also selected because they were more readily defensible than others. In the majority of cases, the topography is rather complex and there were micro- and meso-climatic differences between the settlement sites and the surroundings even before the cities ever sprung up [1].

With the construction of buildings, parking lots, and houses, urban areas dramatically change the smoothness of a surface, the thermal conductivity, the hydraulic conductivity, the albedo, the emissivity, and the fraction of vegetation cover. Thus, urban regions behave a lot different from natural ones and they cause unique physical processes, depending on many parameters like the heat retaining capacity of the construction materials, the sealing of the soil, a modified water balance and the waste heat. As a result, urban landscapes modify the original physical processes that govern any natural land surface, and also add new, unique biogeophysical and biogeochemical processes into the land surface–atmosphere, such as the storage heat flux, the canyon effect, and the anthropogenic heat flux [2].

than the surrounding non-urban areas, because of the higher heat absorption and the relatively limited cooling associated with vegetation and permeable surfaces. Urban areas suffer from air pollution, which is exacerbated by high temperatures. In conjunction with these existing issues, the impacts of climate change on cities will depend on the actual changes in

The cities need to adapt and the climate change needs to be considered in all development plans and investments, local, national, and international. Local policy makers tend to see climate change as an environmental issue of global scale that is not of their concern. The majority of climate change specialists focus on reducing greenhouse emissions, without practically helping cities to learn how to change and adapt. Climate change science mainly deals with global and regional impacts, and it is less able to provide reliable assessments for the cities. Datasets from Earth observation (EO) satellites are crucial for measuring key parameters relevant to the climate change. The use of satellites to observe the Earth provides the data necessary to improve our understanding of the Earth system and help predict future change. The satellite data and products may form the understanding of climate change and the quantitative estimates of its effects form the basis for policy-makers to build effective strategies for adapting to and mitigating the effects of a changing climate. Although EO data and products are mainly used for global and regional research studies, there is great potential in their use for monitoring the urban climate and thus allow cities to adapt to a changing

The urban climate refers to the specific climatic conditions in cities that differ from the surrounding areas, as an effect of the urban development. Urbanization tremendously changes the form of the natural landscape causing changes in the local climate, not only compared to the surrounding areas, but also inside the city. While some climatic elements differ only slightly from one city district to the other, like the precipitation for example, others differ

In the case of conventional meteorological elements (temperature, humidity, wind, and precipitation), it is not as easy to establish the magnitude of modulation of the atmospheric boundary layer by a city, and it is even more challenging to assign causes for the observed changes. One of the main difficulties is the geographical setting of cities. The setting of a city is barely random and settlements are usually developed for specific reasons. Riverbeds, for example, offered good communications in earlier years; coastal cities were developed near natural harbors; others near to natural resources. In many developed countries, settlement sites were also selected because they were more readily defensible than others. In the majority of cases, the topography is rather complex and there were micro- and meso-climatic differences between the settlement sites and the surroundings even before the cities ever

With the construction of buildings, parking lots, and houses, urban areas dramatically change the smoothness of a surface, the thermal conductivity, the hydraulic conductivity, the albedo,

climate, such as increased temperatures and rainfall.

126 Multi-purposeful Application of Geospatial Data

**1.1. The climate of cities and the urban scales**

significantly, like the temperature and the wind conditions.

climate.

sprung up [1].

The urban surface and morphology results in cities being relatively warmer than the rural surroundings, a phenomenon called urban heat island (UHI). The warmer city climate can have fatal consequences such as those witnessed during the summer heatwave of 2003 in Central Europe [3]. There are different kinds of UHIs, displaying different characteristics and controlled by different assemblages of energy exchange processes. These possess different scale manifestations and result from different processes. Air temperature varies with height, a phenomenon much complicated in the urban environments and the different atmospheric layers. Thermal remote sensing permits definition of an UHI named ground or surface UHI, which refers to the skin or surface temperature difference between the city and its surrounding areas.

The concept of scale is fundamental in the understanding of the surface-atmosphere interactions when it comes to urban environments. In building scale, for example, the walls and roof facets have different time-varying exposure to solar radiation, net longwave radiation exchange, and ventilation. Horizontal ground-level surfaces are a patchwork of elements, such as irrigated gardens and lawns, non-irrigated greenspace, and paved areas with contrasting radiative, thermal, aerodynamic and moisture properties, frequently including trees. These different surface elements possess diverse energy budgets that generate contrasts in surface characteristics (e.g., skin temperature), and lead to mutual interactions by radiative exchange and small-scale advection. These fundamental units may be aggregated hierarchically, as illustrated in **Figure 1**.

Distinctive energy balances characterize each scale that generally do not represent the areaweighted average of the budgets of individual elements. This happens because each unit interacts with adjacent ones in the same scale by advection. While spatial scale increases, the

**Figure 1.** Graphical illustration of the different scales in the city. The urban canyon scale includes building walls and elements between buildings. The city block scale includes a number of urban canyons and roofs of buildings. The neighborhood scale refers to a number of city blocks, while the land use scale refers to larger areas including many similar neighborhoods.

spatial variability is likely to be reduced and less difference is expected among two land-use classes in a city for example, than between a north and south-facing wall of an individual building. Urban climatology studies this heterogeneity and complexity, either explicitly, in terms of detailed mapping of urban morphology, or in interpreting observations at aggregate scales [4].

parameters essential for urban studies. The great number of EO data from satellite and airborne systems presents an opportunity to extract a great wealth of information via remote sensing, relevant to the urban and peri-urban environments at various spatial, temporal, and spectral scales. With recent innovations in sensor technologies, urban applications of remote sensing, i.e., urban remote sensing, has rapidly gained popularity among a wide variety of

Earth Observation for Urban Climate Monitoring: Surface Cover and Land Surface Temperature

http://dx.doi.org/10.5772/intechopen.71986

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Environmental scientists are increasingly relying upon EO data to derive, for example, urban land cover information as a primary boundary condition used in many spatially distributed models [7]. The climate change community has also recognized remote sensing as an enabling and acceptable technology to study the spatiotemporal dynamics and consequences of urbanization as a major form of global changes [8]. Lately, more urban researchers are also using remote sensing to extract information for studying the urban surface and geometry [9, 10]. Finally, urban and regional planners are increasingly using EO data to derive information on cities in a timely, detailed, and cost-effective way to accommodate various planning and

Urban remote sensing can help improve our understanding of cities and many benefits of using EO data for urban studies that can be identified. The largest benefit of remote sensing, its capability of acquiring images that cover a large area, applies also for urban studies, where synoptic views allow identifying objects, patterns, and human-land interactions. Identifying the urban processes that operate over a rather large area and quantifying the differences in an intra-urban level is essential for understanding the urban environment. Remote sensing provides a great asset on information gathering on the entire mosaic of an urban phenomenon, while knowledge and expertise from multiple disciplines can lead to full understanding and

Remote sensing holds an advantage as well, and complements the field measurements. Field measurements in most cases in urban sites do not represent the broader area. To cover large areas a lot of field measurements are needed, dense in both temporal and spatial terms and this can become prohibitively expensive in most cases. Moreover, data collected from field surveys and measurements can suffer from biases in the sampling design. Remote sensors can collect data in an unbiased and cost-effective way and thus provide better insights on the spatial and temporal evolution of processes. Field measurement can complement the remote sensing ones and combined methods and products hold great potential in terms of accuracy,

A framework of monitoring, synthesis, and modeling in the urban environment can be achieved with synergies of EO data integrated with relevant geospatial technologies, like spatial analysis and dynamic modeling. This framework can then be used to support the development of a spatio-temporal perspective of the urban processes and phenomena across scales and also to relate the different human and natural variables for understanding the direct and

Last, remote sensing is ideal for connecting different scales for urban studies. Urban science disciplines have their own preferred scales of analysis. For example, urban planners tend to

communities.

management activities [11].

modeling the urban processes.

spatial, and temporal coverage.

indirect drivers of urbanizations.
