Abstract
It is now well known that coastal urban local climate has been showing changing pattern due to global climate change. This communication attempts to explore fluctuating pattern of urban average monthly wind speed during past 50 years (1961-2010). It shows peculiar results taking Karachi (24?53'N, 67?00'E), a coastal mega-city of Pakistan, as a case study. Mann-Kendall trend test shows that March, April and October and both summer and winter seasons show positive trends for the average monthly wind speed during the whole study period (1961-2010). For the earlier 25 years data, it has been found that January, March, May, August, November and December and annual wind speed data have shown the negative trends. Only summer season has shown the positive trend for the wind speed. Similarly, for the most recent 25 years data it has been found that January, February, March, April, May, June, October, November and December and annual and both summer and winter wind speed data have shown the positive trends showing some degree of change in wind speed pattern. Probabilistic analysis reveals that average monthly wind speed data sets follow lognormal, logistic, largest extreme value, and Weibull (two-and three-parameters) probability distributions. Change point analysis has also confirmed the change in the pattern of observed average monthly wind speed data near 1992. The analysis performed reveals the effect of global warming on the local urban wind speed which appears to be temporal non-stationary.
Highlights
We know that the climate system involves the interaction of the biosphere, air, sea, ice and land, with solar radiation providing the energy that drives it
For the most recent 25 years data it has been found that January, February, March, April, May, June, October, November and December and annual and both summer and winter wind speed data have shown the positive trends showing some degree of change in wind speed pattern
This section develops trend models to serve as a guide in the assessment of impact of the global climate change on urban wind speed pattern
Summary
We know that the climate system involves the interaction of the biosphere, air, sea, ice and land, with solar radiation providing the energy that drives it. Analysis shows that there exists a positive trend in the frequency of Arabian sea tropical cyclones in the past 120 years [7]. Arabian sea water temperature data sets near Karachi coast reveal increasing trend [9]. Researches have shown that with the increase of sea surface temperature, the wind speed over sea surface is increasing [15,16]. This communication attempts to investigate the changing pattern of urban monthly wind speed by analyzing past 50 years data taken at 50 meters height at the Quaid-i-Azam International Airport of Karachi.
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