Watching Rainfall in the Douro

If you are wondering where January’s Douro Insider is… it will be here shortly.  I checked in with Miles for an update, and while I was at it, got a brief lesson in weather stations and rainfall tracking.

SFE has five weather stations at various quintas around the Douro, including one at Graham’s Quinta dos Malvedos.  For Douro Insider purposes we rely on the statistics from Pinhão (Quinta do Bomfim) as being both central for the region and also the one location for which we have over 40 years of data.

Three of the weather stations, including the one in Pinhão, are quite high tech indeed – solar powered, they electronically transmit a steady stream of data including high, low and average temperatures daily, rainfall tracking, wind speed and direction, and measures of sunlight, relative humidity and evapo-transpiration (water evaporating from the soil).  Miles can log into a private website at any time and watch the data coming in, and of course download everything he needs to do his analysis and create his temperature and rainfall graphs.

But High Tech is no match for Mother Nature.  It seems occasionally a bird will perch on the edge of the pluviometer (that cup-like device at the top that catches and measures rainfall) and leave a little something behind that jams the device, and disrupts our data flow, as happened this month.  But never fear, Miles has other means of getting his statistics, so the graphs will go on.

Miles can review his statistics and with just a few keystrokes generate a graph like this one, which shows each month’s rainfall (green bars), the 41-year mean for each month (blue bars), as well as the annual cumulative total, both current year (yellow line) and 41-year mean (red line).  The means are based on statistics at Pinhão from 1967 to 2007.

But long before there we had computers and spreadsheets (long before we had Miles!), we maintained painstaking records of rainfall.  At the SFE offices in Gaia there is a meticulously drawn and documented chart of rainfall, comparing statistics for the Douro (brown vertical bars) with Porto (the black bars) over the course of 20 years, from 1901 to 1920.  On the left are recorded the precise figures, in inches and millimetres for rainfall in Porto, on the right, for the Douro.  As you can see, we get substantially more – nearly twice as much – rain here as in the Douro.

Let’s see what Miles’s next graph tells us about how 2011 is getting started for rainfall in the Douro.  Stay tuned.

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