Introduction

Various definitions of cirrus clouds exist in the scientific literature (Lynch et al. 2002). In this chapter, we define cirrus as clouds that primarily inhabit the global upper troposphere and tropopause region and which lack a liquid water phase that is, they are entirely composed of ice crystals. This is equivalent to a temperature criterion constraining the ice formation process, as liquid water droplets freeze spontaneously below 235 K, depending on their size. Upper tropospheric cirrus ice...

Diffusion Turbulence

Air-sea gas exchange Entrainment Shallow cumulus Teleconnections Stratocumulus Convective systems weeks Figure 12.1 Depiction of the continuum of relevant cloud-related processes across the full range of spatiotemporal scales, showing the underlying categorical behavior (gray text) from which processes emerge. scales (i.e., the microscale), or through global warming attributable to additional greenhouse gases. These perturbed clouds include possibly all tropospheric clouds, including contrails...

Introduction Clouds and Earths Radiation Budget

Clouds greatly impact the Earth's radiation budget (ERB) because they reflect solar or shortwave (SW) radiation back to space and restrict the emission of thermal or longwave (LW) radiation to space. One conventional measure of this radiative effect is cloud radiative forcing (CRF) that is, the difference between actual radiation flux and what it would be if clouds were absent (Ramanathan et al. 1989). A more proper term might be cloud radiative effect, since forcing is usually reserved for...

Current Understanding and Quantification of the Effects of Clouds in the Changing Climate System and Strategies to

Anthropogenic aerosols are thought to exert a significant indirect radiative forcing because they act as CCN in warm cloud formation and as ice nuclei in cold cloud-forming processes. Haywood et al. (Chapter 19) address this issue by comparing the radiative forcing from the indirect effect of aerosols with those from other radiative forcing components, such as that from changes in well-mixed greenhouse gases. They highlight problems in assessing the effect of anthropogenic aerosols upon clouds...

AOD 550nm

Figure 3.3 Mid-visible aerosol optical depth (AOD) at 550 nm wavelength. Comparison between annual maps from global modeling (M), the merged product (X), and sun photometer gridded samples (A). Deviations to model simulations suggest AOD underestimates in global modeling. Figure 3.3 Mid-visible aerosol optical depth (AOD) at 550 nm wavelength. Comparison between annual maps from global modeling (M), the merged product (X), and sun photometer gridded samples (A). Deviations to model simulations...

Importance of Small Cloud and ERB Changes and the Difficulties in Measuring Them

Global climate is very sensitive to even slight changes in clouds and radiation, hence requiring very precise measurements of variations in these parameters. For example, an instantaneous doubling of CO2 (100 increase) would produce about a 4 W m-2 reduction in outgoing radiation flux, which is less than 2 of the 235 W m-2 in global mean outgoing radiation. Since the trend in CO2 concentration over the span of a few decades is much smaller than a doubling, the trend in ERB is also...