(1) Cloud Types

 

Clouds have a diverse morphology and wide distribution over the globe. It is necessary to examine the radiative effects from different cloud regimes. For instance, the high convective clouds can effectively reflect the incoming solar radiation, which exceeds their absorption of the Earth’s outgoing infrared (IR) radiation (net cooling effect). In contrast, the thin cirrus clouds at high altitude exert a net warming effect due to their poor albedo (very thin) and capability of trapping IR. Its downward emission of IR might even exert a net heating effect on the Arctic sea ice, as in polar regions, the altitudes of cirrus clouds become much lower. The lower stratocumulous clouds at mid-latitude reflect less solar radiation, while very good at trapping the outgoing IR radiation (very likely a net warming effect). Figure 7.4 (below) displays the various clouds regimes can be observed in two meridional (across different latitudes) transections.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 7.4 | Diverse cloud regimes reflect diverse meteorology.

(a) A visible-wavelength geostationary satellite image shows (from top to bottom) expanses and long arcs of cloud associated with extratropical cyclones, subtropical coastal stratocumulus near Baja California breaking up into shallow cumulus clouds in the central Pacific and mesoscale convec- tive systems outlining the Pacific Intertropical Convergence Zone (ITCZ). (b) A schematic section along the dashed line from the orange star to the orange circle in (a), through a typical warm front of an extratropical cyclone. It shows (from right to left) multiple layers of upper-tropospheric ice (cirrus) and mid-tropospheric water (altostratus) cloud in the upper-tropospheric outflow from the frontal zone, an extensive region of nimbostratus associated with frontal uplift and turbulence-driven boundary layer cloud in the warm sector. (c) A schematic section along the dashed line from the red star to the red circle in (a), along the low-level trade wind flow from a subtropical west coast of a continent to the ITCZ. It shows (from right to left) typical low-latitude cloud mixtures, shallow stratocumulus trapped under a strong subsidence inversion above the cool waters of the oceanic upwelling zone near the coast and shallow cumulus over warmer waters further offshore transitioning to precipitating cumulonimbus cloud systems with extensive cirrus anvils associated with rising air motions in the ITCZ.