Human modification of the landscape has affected rainfall, generation of clouds, and the formation of tornadoes and thunderstorms. In another example of the effects of landscape on weather and climate, Pielke points to a burn map in a boreal forest in Canada in which 16 percent of the landscape is in a recently burned environment. The burned areas are darker, resulting in preferential development of thunderstorms nearby which in turn cause more fires, generating a positive feedback with climatic effects. In the Great Plains and the Texas Panhandle a correlation appears between heavily irrigated areas and tornadoes. A model run using the current landscape is compared to a model run using the natural landscape with the same meteorological conditions.
Results indicate that the tornado formation is related to the current landscape.
The implication of such research is that human modification of the landscape has affected rainfall, generation of clouds, and the formation of tornadoes and thunderstorms. Land use changes may also affect climate at larger scales, as the landscape has been fragmented and the type of vegetation has changed from tall grass prairie to crop land in states like Kansas. At the continental scale, Pielke reports that model simulations at 60-km grid spacing were used to compare U. S. climatic patterns under the conditions of estimated natural vegetation with the those of the current landscape in which huge changes in vegetation distributions are apparent. When this model is run for one month, forced with current conditions, changes at the scale of the United States are apparent. It was the change in the GCM-modeled thunderstorm activity, that resulted from the LAI change, that teleconnected to the higher latitudes and changed the polar jet flow.