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<br />nearby rural network to help evaluate
<br />the apparent urban affected precipita-
<br />tion pattern obtained over the urban
<br />area. The precipitation increase in
<br />Urbana could result eith~r from urban
<br />effects or from natural variations of
<br />precipitation. Raingauge exposures
<br />were a problem in the evaluation of th~
<br />effects. To instrument an urban area
<br />for this purpose is difficult and ex-
<br />pensive.
<br />
<br />CHANGNON, S.A. 1969: -Increased precipita-
<br />tion from urban industrial effects".
<br />ASCE Annu~l and ~nvironmenta1 Enainc~r-
<br />iog ~ccting, Chicago. ASCE Conierence
<br />Preprint lClS, New York, NY.
<br />
<br />Key words: weather modification.
<br />
<br />Urban-prOduced precipitation increases
<br />of four midwest cities and two large
<br />eastern cities range from 5 to 16 per-
<br />cent in annual precipitation and rain
<br />days, with 7 to 22 percent increases in
<br />summer thunderstorm days. Within the
<br />past 25 years, in an area downwind from
<br />Chicago, incr~ases 1n precipitat10n
<br />were 31 to 246 percent. In Chicago,
<br />St. touis, and Champaign-Urbana, dis-
<br />trict m~xima were centred in or east of
<br />the cities. This supports the theory
<br />of urban-produced increases in the pre-
<br />vailing eastward moving precipitation
<br />systc~~. Similar increases in preci?i-
<br />tation were not~d in Tulsa, washington,
<br />D.C., New York City, and much greater
<br />increases in La Porte, Ind.
<br />
<br />CHANGNON, S.A. 1969: -Recent studies of
<br />urban effect on precipitation in the
<br />United States-. American Met. Soc.
<br />Bulletin, Vol.S0(6), p41l-421.
<br />
<br />Key words:
<br />environmental
<br />effects.
<br />
<br />weather
<br />effects;
<br />
<br />modification;
<br />air pollution
<br />
<br />Urban produced increases in precipita-
<br />tion range from 5 to 16 percent, and
<br />increases in number of thunderstorm
<br />days range from 7 to 20 percent. Even
<br />greater increases in precipitation have
<br />been observed downwind from major steel
<br />mill complexes. These Changes have
<br />been credited to urban-induced nuclei
<br />concentrations and urban thermal ef-
<br />fects. The results of these studies
<br />may indicate the effectiveness of
<br />ground-based seeding, the possibility
<br />of successful increases in all seasons,
<br />the likelihood of thunderstorm and ha-
<br />ilstone increases with rainfall incre-
<br />ases, and the need for dense raingauge
<br />networks to adequately determine the
<br />area and amount of increase.
<br />
<br />CHANGNON, S.A. 1973: .Urban-industrial ef-
<br />fects on clouds and precipitation-.
<br />In, Proceedings from a workshop on in-
<br />advertent weather modification, Utah
<br />State University, rogan: plll-139.
<br />
<br />Key words:
<br />ification;
<br />turbidity;
<br />
<br />urbani sat ion; weather mod-
<br />air pollution effects:
<br />urban runoff; streamflow.
<br />
<br />Man through modifications of the biOS-
<br />phere has been affecting the atmosphere
<br />
<br />~
<br />
<br />36
<br />
<br />on local and regional scales for many
<br />years. These a1ter~tions have been
<br />produced by urban-industrial centres,
<br />non-urban industrial centres, landusc
<br />changes in rural areas (deforestation,
<br />crop changes, drainage etc.) and marine
<br />areas. A major means whereby man has
<br />affected weather has been through his
<br />urban environment. The increase in ur-
<br />banisation that began 200 years ago
<br />with the industrial revolution has len
<br />to relatively significant local ann me-
<br />soscale changes in the weather in and
<br />near urban locales. Since urban areas
<br />first proliferated in Europe, consider-
<br />able scientific attention ha~ been di-
<br />rected to this problem in the Europedn
<br />area during the last 1~9 years. Mow
<br />that major urban-industrial comp1ex~s
<br />are prevalent in many countries, world-
<br />wide attention to this problem has
<br />grown rapidly in the last 2n years, an~
<br />the developm~nt of megalopolises in th~
<br />united States during the past 30 years
<br />has brought with it increasing public
<br />and scientific aWar~ness of the degree
<br />and the seriousness of urban effects on
<br />mesoscale weather and climate.
<br />
<br />.
<br />
<br />.
<br />
<br />CHANGNON, S.A. 1973: -Study of urban ~f-
<br />fects on precipitation and severe
<br />weather at St. Louis. Annual report
<br />March 1970 - February 1973-. Illinois
<br />State Water Survey, urbana; 54pp.
<br />
<br />Key words: weather modification.
<br />
<br />The general goal of the Water Survey
<br />program involving ~ETROMEX (Metropoli-
<br />tan Meteorological Experiment) consists
<br />of the deline?tion of any anomalies in
<br />the precipitation and severe weather
<br />p~tterns and frequencies in St. Louis
<br />and environs, the quantification of the
<br />causes for any such ano~alies, investi-
<br />gations of the relevance of these find-
<br />ings to the local area and to other
<br />urban-agriculture areas of Illinois,
<br />and the transmission-of these findings
<br />to potential users in the scientific
<br />community and to the public of Illi-
<br />nois.
<br />
<br />,
<br />
<br />CHANGNON, S.A. 1973: -Inadvertent weather
<br />and precipitation modification by ur-
<br />banisation-. J. Irrigation and Drain-
<br />age Division, Proc. ASCE, Vol.99fIR1):
<br />p21-41.
<br />
<br />Key words: urbanisation, weather mod-
<br />ification; urban hydrology; air pol-
<br />lution effects.
<br />
<br />urban-industrial complexes produce
<br />measurable modification of all weathpr
<br />conditions. particularly significant
<br />are increases in the precipitation con-
<br />ditions of interest to hydrologists and
<br />urban planners. In and immediately
<br />downwind of major urban areas, the an-
<br />nual precipitation may be increased
<br />from 5-30 percent, the annual thunder-
<br />storm frequency is incr~ased 15-30 per-
<br />cent, the heavy daily rainstorm fre-
<br />quencies are increased by 20-40 per-
<br />cent. Increases in local runoff may be
<br />from 15-20 percent. toeal crop yieldS
<br />may be increased 2-10 percent by this
<br />rain modification.
<br />
<br />,
<br />
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