moisturetransport

Moisture transport refers to the movement of water vapor and, to a lesser extent, liquid water within the Earth's atmosphere by winds and turbulent processes. It is a central aspect of the global hydrological cycle, redistributing moisture from ocean sources toward landmasses and from low to high latitudes, thereby shaping weather and climate patterns. The primary carrier is water vapor; cloud formation and precipitation modify transport through vertical motions and phase changes.

Quantities and mechanisms are described using moisture fluxes. The horizontal moisture flux is F_q = q v, where q is specific humidity and v is the horizontal wind vector. The evolution of atmospheric moisture in a column is often expressed by a budget that includes evaporation (E), precipitation (P), and the divergence of the horizontal moisture flux (∇·F_q): ∂W/∂t = E − P − ∇·F_q, where W denotes precipitable water. Moisture convergence, the negative of the flux divergence, is a key driver of precipitation in many regions. Vertical transport and convection also play important roles, moving moisture rapidly upward and contributing to intense rainfall events.

Major transport pathways arise from large-scale atmospheric circulation and organized convective systems. Notable manifestations of concentrated moisture transport include atmospheric rivers, which carry large amounts of water vapor over long distances, often delivering heavy rainfall when they encounter orographic lifting or frontal systems, and the seasonal monsoons that bring extensive tropical moisture to subtropical regions.

Measurement and modeling rely on observations of humidity and wind, as well as reanalysis products and climate models. Moisture transport is evaluated through flux diagnostics, moisture budgets, and water vapor transport tendencies, informing weather forecasting, drought and flood assessment, and climate research.