Inadvertent Weather and Precipitation Modification by Urbanization

Urban-industrial complexes produce measurable inadvertent modification of all weather conditions and specifically significant increases in the precipitation conditions of interest to hydrologists and urban planners. In, and immediately downwind of, major urban areas the annual precipitation may be increased from 5–30%, the annual thunderstorm frequency is increased 15–30%, the heavy (2-in.) daily rainstorm frequencies are increased by 20–40%. Increases in local runoff may be from 15–20%. Local crop yields may be increased 2–10% by this rain modification.