RELATIVE INFLUENCE OF VEGETATION ON URBAN ENERGY BUDGETS AND SURFACE TEMPERATURES (Research Note) WERNER H. TERJUNG Department of Geography, University of California, Los Angeles, U.S.A. and PATRICIA A. O’ROURKE Department of Geography, California State University, Northridge, Cal., U.S.A (Received in final form 22 January, 1981) Abstract. Two deterministic models were combined: one for canopy leaf energy budgets and one for street canyon energy budgets. The effects of street parks and roof gardens in contrast to non-vegetated city blocks were examined by the use of four typical urban morphologies, which were exposed latitudin- ally to summer and winter simulations. A variety of increases and decreases in shortwave radiation, net radiation, sensible heat flux, and system reradiation resulted. These changes appear to represent the generalized limits of the possible responses to the addition of vegetation to non-vegetated city blocks. 1. Introduction The literature indicates that only a few studies have explored a city’s energy budget and surface temperatures as changed by the inclusion of parks and roof gardens (see, for example, the review by Chandler, 1970). A multi-layered canopy leaf energy budget model CANOPY was developed by Terjung and O‘Rourke (1980~) to be used in this context. This has been combined with URBAN 3, a model which makes use of the microscopic perspective of the energy budgets of urban places (Terjung and O‘Rourke, 1980a, b, c, and d). By using such a model, a city or parts of cities can be subdivided into street canyon systems enabling a block-by-block analysis of energy fluxes into or out of buildings. 2. A System of Urban Street Canyons Four characteristic urban building combinations were created in order to compare the resultant behavior of energy budgets of street parks and roof gardens with changing physical structures (Figure 1). These neighborhoods represent a conti- nuum between high-rise buildings and low structures, with combinations thereof. Half of the wall surfaces were occupied by windows. All buildings were constructed of concrete. The walls, roofs and windows had individualized albedos and emissiv- ities. The space between buildings 1 and 2 was occupied by a street park canopy (leaf area index LA1 = 4). Two climatic simulations were examined. First, a typical clear summer day in August was simulated with shelter-height air temperatures varying from 20 to 33.5C and wind speeds from 3.6 to 5.4m s-l (both peaked at 1300hr). The air temperatures Boundary-Layer Meteorology 21 (1981) 255-263. 0006-8314/81/0212-0255$01.35. Copyright 0 1981 by D. Reidel Publishing Co., Dordrecht, Holland, and Boston, U.S.A.