P3.4
Urban-Rural Humidity Variations in Phoenix, Arizona
Erinanne M. Saffell, Arizona State University, Tempe, AZ; and A. W. Ellis
Water vapor has recently advanced as a potential indicator of climate change, as any potential increase in air temperature potentially enhances the atmospheric component of the hydrological cycle. Variations in near-surface atmospheric moisture also have implications on human health and regional climate modification. As such, it has become important to gauge the variability of regional water vapor.
This study establishes a climatology of near-surface humidity during the decade of the 1990s in an arid, urban-rural region, relative to the overlying synoptic moisture regime. Fourteen meteorological stations in and surrounding Phoenix, Arizona, were assembled and stratified according to land cover classification as determined from remotely-sensed satellite imagery. A composite of synoptic (850 mb) atmospheric moisture over the region was also assembled for study.
The results demonstrate that while rural regions remain inherently moister than urban regions, urban moisture levels closely approximate or surpass rural moisture conditions at specific intervals during the annual and diurnal cycles. A monthly climatology suggests that transition months between the summer monsoon period and the passage of mid-latitude cyclones in winter are marked by the smallest urban–rural moisture gradient within the annual cycle. This is supported by a diurnal climatology that demonstrates an Urban Moisture Excess in the urban environment in late evening hours during these same transition periods (spring and fall). A case-study of extreme urban-rural gradients identifies the nature of the larger atmospheric events that set into motion extreme moisture results between the two settings, where drier atmospheres contribute to a smaller urban-rural gradient. A negative decadal trend in near-surface and synoptic-level humidity was noted qualitatively, although the results of the time-series analysis were not statistically significant to quantify any trend.
Poster Session 3, UHI and Urban Humidity
Wednesday, 22 May 2002, 3:00 PM-5:00 PM
Previous paper