I was looking at the temperature plots in Nashik, India and noticed an intriguing trend.

screenshot from WeatherUnderground forecast

What could explain this trend? [screenshot from WeatherUnderground forecast] Shouldn't the plot be smoother? Other cities have significantly smoother plots.

To confirm that this was not an error in the app, result from Google Weather was tallied and matched.

  • $\begingroup$ ... bands of clouds? wind changing and bringing down gusts of higher, cooler air? $\endgroup$ – Daniel Griscom May 29 '16 at 2:01

Many possible mechanisms can create temperature fluctuations on the scale of an hour or two. First there is the met site itself. Are there trees or buildings that could provide partial shade, especially when the sun is low in the sky? Are there buildings that could reflect sunlight directly onto the instrumentation? Then there are local anomalies. Are there gully winds? Do cloud banks form in the mornings, or high cumulus towers build up in the afternoons (quite common in the Western Ghats of India)? Is there a local temperature inversion, and does it disperse daily? What kind of local wind patterns are there? Is there a lake nearby that could create local cooling if the winds are in the right direction? Conversely, is there a source of local heat anomalies - factories, power stations? On the larger scale, what is the area topography, and what local air circulation does it create? Is there some interaction between monsoonal air flow and continental air masses? What turbulence does this create? Some bizarre anomalies are also possible, like birds roosting on the instrumentation! Really, there is no short-cut answer. The only solution is to go there with an unbiased and inquiring mind, and check out what's going on. I'm guessing that for such a consistent fluctuation it will be something obvious.

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    $\begingroup$ Thanks! Are these factors capable of dropping the temperature so frequently? And by nearly 3-4 degrees Celsius everytime? $\endgroup$ – Raj May 29 '16 at 14:18
  • $\begingroup$ 3 to 4 degrees C is quite a lot, but not beyond the bound of possibility for such processes. Consider that, on an even smaller scale, a cone shaped flower can concentrate heat by + several degrees, thereby making this micro-climate attractive for bees. The 'art' of good meteorology is deploying the instrumentation such that the results are truly representative. This is not as easy as one might think. $\endgroup$ – Gordon Stanger May 31 '16 at 5:49

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