The Agricultural Weather Service of Luxembourg's Ministry of Agriculture, Viticulture and Rural Development has published a statistical analysis of meteorological data collected throughout 2018, confirming that Luxembourg experience above-average temperatures and below-average rainfall in the summer of 2018.
The data has been collected from the network of 32 automatic weather stations from all regions across Luxembourg. This year's weather data from the four representative stations Asselborn (north), Clemency (south-west), Remich (Moselle valley) and Grevenmacher (Moselle valley) were compared with the averages of the reference period 1981-2010.
2018 was up to 1.9°C warmer than the long-term average of 1981-2010. The annual precipitation totals were similar to the long-term average of 1981-2010, but the distribution had a significant deficit in the summer months. In Remich and Grevenmacher the climatic water balance in July even fell to a record low.
The mean temperatures were 1.2°C at the Asselborn station, 1.3°C at Remich, 1.6°C at Clemency and 1.9°C higher at Grevenmacher than the long-term average. Graphs show that only the months of February and March were below the long-term values; in all other months the measured mean temperatures were higher than the mean for the reference period 1981-2010. The largest negative monthly deviation was recorded in Asselborn in February at -3.3°C. In January, the largest positive deviation was measured at + 4.2°C in Remich.
The precipitation totals of 2018 at all four stations were slightly below the averages of 1981-2010. Only in Asselborn was a significant deficit of -23% (-197 mm) measured. However, the distribution of monthly rainfall totals shows that rainfall was recorded at only the months of January, June, and December at all four stations compared to the long-term average of 1981-2010. The percentage maximum deviation was recorded with + 134% of the target in January in Remich. The months from July to November, however, showed negative deviations from the long-term values at all stations, except for the values in August in Grevenmacher, which are slightly positive due to local, heavy rainfall which led to floods. In Grevenmacher and Remich only 4 mm and 6 mm respectively were measured in July. These very low amounts of precipitation, in conjunction with the high temperatures, led to a drying out of the soil.
In order to be able to quantify this interaction between precipitation deficit and high temperatures, the climatic water balance was calculated, which results from the difference between the monthly totals of the precipitation and the monthly sum of the potential evaporation. In order to calculate the potential evaporation, in addition to the temperature, measurements of wind speed and the duration of sunshine are required. Since these are missing at the stations at Asselborn and Clemency, the nearby stations Reuler and Obercorn were used for this comparison. The graphs also show that, except in Obercorn, 2018 shows a negative water balance, so that the potential evaporation was higher than the fallen precipitation. A monthly analysis shows that at all four stations the water balance was negative from April to October, which explains the extremely dry soils into the autumn. Particularly noteworthy are the extremely negative values for July, which set a new record in Grevenmacher and Remich, since the record of the water balance in 2003, while in Reuler and Obercorn, only the July of 2006 had an even lower value.
All recorded data of the 32 ASTA stations can be accessed on http://agrimeteo.lu.
