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Clouds
Chapter 1
Clouds Clouds are pictures in the sky They stir the soul, they please the eye They bless the thirsty earth with rain, which nurtures life from cell to brain— But no! They’re demons, dark and dire, hurling hail, wind, flood, and fire Killing, scarring, cruel masters Of destruction and disasters Clouds have such diversity— Now blessed, now cursed, the best, the worst But where would life without them be? Vollie Cotton
1.1. INTRODUCTION Since the late 1940s, when the experiments by Langmuir (1948) and Schaefer (1948) suggested that seeding of certain types of clouds could release additional precipitation, there has been intensive investigation into the physics of clouds. The major focus of these studies has been on the microphysical processes involved in cloud formation and the production of precipitation. As the studies have unraveled much about the detailed microphysics of clouds, it has become increasingly apparent that these processes are affected greatly by macroscale dynamics and thermodynamics of the cloud systems. We have also learned to appreciate that the microphysical processes can alter the macroscale dynamic and thermodynamic structure of clouds. Thus, while the focus of this book is on the dynamics of clouds, we cannot neglect cloud microphysical phenomena. The title of this book implies a perspective from which we view the cloud or cloud system as a whole. From this perspective, cloud microphysical processes can be seen as a swarm or ensemble of particles that contribute collectively, and in an integrated way, to the macroscale dynamics and thermodynamics of the cloud. We take a similar perspective of small-scale air motions in clouds. Again, we will not use our highest power magnifying lens to view the smallest scale motions or turbulent eddies in clouds. We will instead examine the collective 1
Clouds Clouds are pictures in the sky They stir the soul, they please the eye They bless the thirsty earth with rain, which nurtures life from cell to brain— But no! They’re demons, dark and dire, hurling hail, wind, flood, and fire Killing, scarring, cruel masters Of destruction and disasters Clouds have such diversity— Now blessed, now cursed, the best, the worst But where would life without them be? Vollie Cotton
1.1. INTRODUCTION Since the late 1940s, when the experiments by Langmuir (1948) and Schaefer (1948) suggested that seeding of certain types of clouds could release additional precipitation, there has been intensive investigation into the physics of clouds. The major focus of these studies has been on the microphysical processes involved in cloud formation and the production of precipitation. As the studies have unraveled much about the detailed microphysics of clouds, it has become increasingly apparent that these processes are affected greatly by macroscale dynamics and thermodynamics of the cloud systems. We have also learned to appreciate that the microphysical processes can alter the macroscale dynamic and thermodynamic structure of clouds. Thus, while the focus of this book is on the dynamics of clouds, we cannot neglect cloud microphysical phenomena. The title of this book implies a perspective from which we view the cloud or cloud system as a whole. From this perspective, cloud microphysical processes can be seen as a swarm or ensemble of particles that contribute collectively, and in an integrated way, to the macroscale dynamics and thermodynamics of the cloud. We take a similar perspective of small-scale air motions in clouds. Again, we will not use our highest power magnifying lens to view the smallest scale motions or turbulent eddies in clouds. We will instead examine the collective 1