December 2010 Douro Insider

For fans of wintery weather, the last month of the year did not disappoint.  It started with much of Europe still in the grip of extremely cold conditions, as the unusually reversed conveyor (mentioned in the last report) started drawing in air from Siberia with predictable consequences.  There was plenty of snow and the usual closure of roads across many parts of the country.  Again, our relatively southerly position worked to our favour and, from a European perspective, we escaped lightly by comparison with other nations.  Elsewhere much of the continent was thrown into what can only be described as travel chaos, and all forms of transport were badly affected including (infamously) most of Britain’s major airports.  The deep frosts were even felt in Porto, with car doors and windows freezing shut overnight around this time.  Given the city’s position on the coast, its weather is influenced by the prevailing ocean currents which are primarily from the southwest and comparatively warm. It was therefore obviously something of a surprise to feel such cold. 

By the end of the first week the incoming weather had moved round to the southeast and a warm, damp and highly unstable mass of air moved in over Iberia.  As a result it turned very wet indeed and several days were lost in the vineyards when it was simply raining too much to work.  The olive picking in particular was badly compromised.  Then suddenly an actual tornado burst out from the middle of all this confusion, smashing into the Tomar area on the 7th and damaging in excess of 400 buildings.  Dozens of people were injured too but fortunately there were no fatalities.  It might be all very well for some countries but we certainly don’t expect that kind of nonsense to happen here.

After this the heavens almost appeared remorseful, and we enjoyed a few days of comparatively warm weather; most importantly of all is that it stayed dry.  This calm period meant that we were able to catch up with some of the work that had been lost through the snow, rain and the two public holidays at the start of the December.  Good weather at this time of the year can never be taken for granted though, and true to form this respite was short-lived.  The middle of the month was marked by a return of the frosts (including down in Porto and Gaia again) but the days were lovely and sunny, and the air was still, if chilly.  But another cold snap was just about all that happened here, so relatively speaking we were really quite lucky as yet again Portugal found itself on the benign periphery of a much more violent weather system.  This was, of course, December’s second wave of cold: the one that paralysed much of Europe’s transport network all over again with roads, runways and railways badly affected by snow once more.  This went on right up until Christmas.

The festive season itself was not particularly festive as far as the atmospheric conditions went.  On the contrary, it was precisely the kind of cold and wet weather we had over Christmas that made one grateful for blazing hearths and comforting glasses of port.  There were dramatic downpours in both Lisbon and Porto leading to localised flooding, and café tables and chairs were swept off the pavements and washed away.  And then finally, in the dying days of the year, it warmed up a little and also dried out but still remained greyish.  On balance, the weather this December was really pretty terrible, even by December’s usual unappealing standards.  As we shall see, it was both much colder and much wetter than we had the right to expect based on the experience of past years.

A glance at the figures reveals that this was a month of extremely high rainfall.  Total precipitation in Pinhão was 171 mm, the highest monthly total since December of 2009.  This is more than double the average amount for this time of the year (85 mm).  Predictably, it was drier further east (usually rainfall decreases moving upriver) and in this case quite dramatically so.  Some quintas closer to Foz Côa had less than a third of Pinhão’s total, illustrating perfectly the dramatic difference that a few kilometres makes in the Douro.  Likewise, those properties further to the west and in the lee of the Marão were even wetter.

The usual precipitation graph shows clearly that December was the wettest month this year (note the height of the green bar) and therefore 2010’s cumulative total (the orange line) yet again extends its lead over the mean (the red line).  It is interesting to see that at no point this year did we suffer a precipitation deficit relative to the cumulative mean, in spite of the bone-dry summer.  At the year’s end our total rainfall figure for Pinhão is 859 mm which is nearly 30 % higher than the average annual amount (675 mm).

We have already seen that it was quite a bit colder than average, but by turning our attention to the temperature graph it becomes apparent that December was actually the third consecutive month with an average temperature more than a whole degree below the long-term mean.  This obviously represents a significant and prolonged cold period.  Our mean temperature in Pinhão this month was just 7.3º C which compares poorly with the long-term average of 8.6º.  In all, there were seven frosts with the temperature dropping to -2º at one point.  However, it is perhaps surprising to hear that most properties had top temperatures very close to 20º C and it is also true to say that it was really quite pleasant to be outside on the few occasions when the sun was out.  At higher altitudes, away from the insulating effect of the river, the monthly averages as well as the absolute maximum and minimum temperatures were considerably lower of course.

Curiously enough 2010 had five below-average months in terms of temperature, and all of them were more than one degree below the mean.  But we probably shouldn’t complain, because it is worth commenting again on how lucky we actually were in comparison with the other European countries that were also influenced by the same broad-scale climatic patterns this month.  In Britain as a whole, for example, it turned out to be the coldest December for 120 years; in the Douro it was only the coldest since 2006.

What is interesting about both these graphs, now that they are complete, is that they illustrate a clear polarisation of both temperatures and rainfall, with extremes of one during the summer and an overflow of the other during the winter.  Six consecutive summer months, from April to September, all registered above average temperatures.  Most of them were drier than average too.  Just as well then that the winter had already brought plenty of rain – with the first four months of the year (not to mention the last three of the year before) wetter than expected.

Climate change scientists at both NASA and the NOAA pronounced 2010 the hottest year on record globally, and it seems that the tendency towards extreme events (heat waves or freezes, droughts and flooding etc.) are considered to be classic symptoms of global warming.  But in the Douro records do not bear this out.  Not only were the winter months wetter, but they were also colder than average in general; sufficiently so as to cancel out the effect of the very hot summer when it came to calculating the average temperature over the course of the year.  The final figure came in at 15.88º which is actually fractionally cooler than the long-term figure of 15.94º.

If there is one viticultural report in the year when it feels like the quickest way to sum up the work in the quintas would be to write ‘see last month’ then December’s is surely the one.  Very few new jobs are undertaken, and few of the ongoing activities come to an end.  We kept on pruning (and prepruning) much as we have been doing for some time now, and by the end of the year one would hope to have broken the back of it in the majority of quintas.  When the tractors have finished using the prepruner they normally swap it for a triturador (cane shredder).  This consists of a rapidly rotating cylinder, its surface covered with flailing blades or ‘hammers’, which is pulled behind the tractor just in contact with the surface of the ground.  The hammers make short work of the prunings, and a single pass is sufficient to turn them into little more than short bundles of plant fibre.  This is easily reincorporated into the soil, thereby increasing the level of organic matter.  The only vineyards in which we cannot use the triturador are the vinhas velhas where there is no access for machinery.  In these cases the canes are collected up by hand and burnt.

If soil corrections are to be carried out in any particular blocks we obviously need to shred the canes first so that the selected fertilisers can be ploughed in more effectively, and often we will add some lime too to increase the pH of the soil, depending on analyses.  Douro soils are generally very acidic although there is a tendency for the pH to increase moving upriver.  Low pHs restrict the vines’ uptake of macronutrients so often our fertility problems can be addressed from two different angles – both by adding more of the elements that are in short supply and by making those that are present (albeit in limited quantities) more readily available to the plants by swinging the pH in their favour.  In the old vineyards, where there is no access for tractors, the ploughing is still carried out in the sure-footed traditional fashion.

Olive picking also continued this month in a restricted number of quintas.  Generally speaking it is a good idea to finish picking the olives before Christmas as often the holidays coincide with plenty of rain and wind, as was the case this year.  This usually means that by January there are far fewer olives still left clinging to the trees.  As with grapes, when yields are high picking is more productive so basically the later one waits to collect the olives the lower the returns on a day’s work are.  With margins so thin at the moment it is clearly important to make sure that any time spent on the olive harvest is used as efficiently as possible.  In any quintas where the vineyards are certified organic, the olive groves are also covered by this chemical-free guarantee and prices are therefore somewhat higher.  The subsidies that are paid out are higher too, but there is a condition attached: at least 500 kg of olives per hectare must be picked each year – an amount that probably corresponds to somewhere between 80 and 90 L of olive oil.

When weather permitted, the surribas continued.  There is a large area of vineyard being reconverted this winter so it promises to be a busy time for the next few weeks, if only the rain holds off.  Two much mud means that the machinery gets bogged down, and in any case it is very difficult to properly break up and turn over the top layer of soil if it is all sticking together in heavy clumps.  Lots of rain can be something of a double-edged sword: it slows down the terrain preparation and forces us to plant the rootlings later.  This might reduce their chances of taking, especially if the buds have started to burst on the young vines whilst they are still in storage prior to planting.  On the other hand it will mean that the soil clearly has plenty of humidity in it after the winter, and with any luck we won’t need to water the new plantations so soon or so often.