What fraction of the sky is cloudy?
Depending on their altitude, structure and composition (ice or water) clouds will regulate energy differently. One cloud may trap heat by reflecting energy back to the surface. Another may reflect sunlight and cause the surface to cool. You may have noticed that a cloudless night can be much colder than a cloudy night. Without the heating of the sun and a layer of clouds to insulate us, the surface radiates more heat into space on cloudless nights, making them colder. To study these characteristics, researchers combine data from a variety of instruments to form a complete understanding of cloud radiative properties. Instruments used to study clouds include: MilliMeter Cloud Radar (MMCR) developed at PSD uses electromagnetic waves to determine the characteristics of cloud particles from radar reflectivity which is the strength of the signal reflected from the cloud particles. The MMCR can also measure particle velocity, which is determined from the Doppler shift that the particle motion
