Crossing borders is always a challenge since it involves exploring unknown territory characterized by its own language, formulations, and means of expression. Even more important, crossing disciplines requires employing new ways of thinking and applying new approaches to the challenges of the investigation. However, all fears can be allayed if we are able to establish connections and build bridges. This book aims to create links among the disciplines of atmospheric dynamics and chemistry, surface processes, and the role of vegetation in the carbon cycle in order to identify their respective influences and feedbacks. As Figure 1.1 suggests, the aim of the book is to explore how and where these fields intersect.

We focus on the lower part of the atmosphere – the first kilometer in the troposphere – during daylight hours (diurnal) over land. During this part of the twenty-four hour cycle atmospheric motions are strongly influenced and controlled by surface and vegetation conditions, causing a very turbulent flow, in contrast to nighttime conditions normally characterized by a thermally stratified flow. In turn, atmospheric conditions such as wind, temperature, and humidity can also affect the physical properties of the land surface. The picture shown in Figure 1.2 is an illustration of how surface processes – in this particular case, vegetation – interact with the lower atmosphere to form and maintain clouds. A key process in this atmospheric region is the transport and exchange of energy, moisture, and momentum between the surface and the higher tropospheric regions. Scientists have traditionally studied the individual disciplines of atmospheric dynamics and chemistry, land characteristics, and the cycles of carbon or nitrogen compounds. As Figure 1.1 shows, our aim is to identify the relationships among these different disciplines. By retaining the essential components of each field, we can reach a better understanding and representation of their interactions. In other words, we move horizontally among the various subjects, while providing a solid basis for in-depth study of the specific fields. By linking them, we can take advantage of the well-established knowledge that we find in the textbooks of atmospheric dynamics, chemistry, vegetation, and soil and begin where they either end or have paid less attention to particular aspects of the lower-atmosphere phenomena.