Eighth Symposium on the Urban Environment
Boundary Layers and Turbulence Committee
Special Symposium on Measurements in the Urban Environment and Observations


A Preliminary Study on the Response of Land Surface Temperatures to Changing Ocean Temperature Gradients along the New York City Area

J.E. Gonzalez, Santa Clara Univ., Santa Clara, CA; and A. Greenbaum and A. Bharth

This paper addresses a climatological study of surface temperatures trends in the coastal urban environments along the Northeast of the U.S.A. The work follows recent studies along the west coast of the United States which yielded evidence of Diurnal Asymmetrical Warming (DAW). These studies for the western Pacific coast showed that average land based minimum temperatures have been rising at rates comparable to sea surface temperatures, while trends in maximum temperatures indicated a decrease in coastal locations. The current study explored how surface temperatures react to increasing regional sea surface temperatures for the coastal urban environment of New York City. Summer time (June, July, August) maximum and minimum temperatures were obtained from 27 separate weather stations in the area of 39-42N and 75-69W; the data was of monthly averaged for the time period of 1950-2005. The data was sorted into two time periods, 1950-1971 and 1972-2005, to account for the climatic change observed between 1971 and 1972. It was observed that approximately 17 stations in the region show a generally greater increase for minimum temperatures than for maximum temperatures between 1972 and 2005. At least five of the remaining stations (more rural/coastal) exhibited maximum temperatures increasing faster than minimum temperatures. Farther inland in NY and NJ it was observed that there was a decrease of both maximum and minimum temperatures. Only 3 stations showed a decrease in minimum temperatures. Alternately, one location, Wantagh Cedar Creek, Long Island, exhibited intense and significant increases in temperatures for both maximums and minimum even though they were located in a coastal and relatively rural location; minimum temperatures increased by 1.78F per decade (p<.01) while maximum temperatures increased by 1.198F per decade (p<.01). This is attributed to a relatively recent suburban development of Long Island in the past half century. Overall, decreases in minimum temperatures were never observed in the New York City Region, and remained for the most part in more rural inland areas. Decreases in maximum temperatures were often observed along the coast. Outside of land surface trends, sea surface temperature (SST) trends showed only increases over time from 1981-2005 for mean temperatures around the Northeast U.S. coast. As an average of all land data, minimum temperatures showed a .296F/decade increase (p<.01), while maximum temperatures showed a lower .117F/decade increase (p>.1). Both values were higher for the period of time after 1972; a .564F/decade increase was observed for minimum temperatures (p<.01) and .32F/decade for maximum temperatures (p>.1). It is important to note that low significance was observed more frequently in the maximum temperature plots; however, the maximum temperatures showed reoccurring and expected trends at most locations. This may suggest other external phenomena, such as sea breeze flow patterns. In general, this research has set the stage for further study into larger coastal areas, wind speeds, humidity, population density, and other factors that may explain the observed trends.

Joint Poster Session 1, Measurements in the Urban Environment
Tuesday, 13 January 2009, 9:45 AM-11:00 AM, Hall 5

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