In studies of the general circulation and of tropical convection, he always extolled the importance of vertical mixing by cumulonimbus convection, and became known for his catch-phrase "up moist-down dry," referring to the upward motion in a convective core following a moist adiabat, and the large-scale downward motion in the Hadley Cell and trade wind regions following the
dry adiabat. There was also the famous expression known as "the Bill Gray question," where after a theoretical or dry presentation, he would congratulate the author on his insights, enthusiasm, and hard work, but would ask, "But what does it all mean?"