Climate Impact Indices (CII) are used to describe the characteristics of climate change, especially changes in the extremes. Here we present a selection from the 27 ETCCDI climate change indices for 2014. A overview of the 27 indices from 1950 until now is presented in ECA&D
Number of wet days R1mm
R1m is defined as the number of days where the daily precipitation sum exceeds 1mm. Although the annual R1mm is rather low, the spring anomaly (right) shows strong regional variations. The Balkans has seen up to 10 more days is spring with precipitation, while Northeastern France and parts of western Russia have seen less rainy days.
Figure 1: Maps of anomalous spring (left) and annual (right) wet days index R1mm.
Total Wet-days Precipitation (Prcptot)
Spring has been very wet in Serbia, Bosnia and Herzegovina, FYROM and parts of Romania and Bulgaria. In mid-May 2014 Serbia and Bosnia and Herzegovina saw some of the worst floods in 120 years.
Figure 2: Total wet-days precipitation spring (left) and annual anomaly (right).
Very Heavy Precipitation days (R20mm)
Maps below show the annual and spring anomaly of the number of days where the daily accumulated precipitation exceeds 20mm. Slight increases in the annual number of these days is seen along the Adriatic coast and southern Norway, with slight decreases in western Scotland.
In spring, the increase over Serbia and Bosnia and Herzegovina stands out, with the strongest decreases over southeast Norway, West Scotland, northwestern Spain and Portugal and northwest Italy.
Figure 3: Maps of very heavy precipitation days anomalies for annual (left) and spring (right).
Extremely wet days (R99p)
By calculating, for each position on the map, the daily precipitation threshold at which the 1% heaviest precipitation occurs for the climatological period, it is possible to diagnose the increase in the number of days with such extreme precipitation. The figures below show the increase or decrease in the number of extreme precipitation days for spring and summer 2014, with respect to the climatology.
The large amounts of rain in Serbia and Bosnia and Hercegovina, as well as on the boundary of Austria and Italy stand out in spring. In summer, excessive amounts of rain in Northern Italy, which have lead to local flooding, and along the Adriatic coast are observed.Eastern Europe and Sweden experienced a decrease in the amount of extreme precipitation over the summer.
Figure 4: Maps of extreme wet days spring (left) and summer anomaly (right).
Consecutive Wet (CWD) and Dry Days (CDD)
By distinguishing the dry and wet days using the 1 mm threshold, the maximum number of consecutive wet days and the maximum number of consecutive dry days can be determined. It shows that the maximum length of the period with only wet days has been shorter in 2014 compared to the climatology, especially at the Norwegian Atlantic coast.
The maximum length of a dry spell has generally decreased over western Europe and increased in eastern Europe. Exceptions are the inland of Spain, northeast France, and north Scandinavia which have seen longer dry spells than usual.
The changes in the maximum length of a dry spell for 2014 are not consistent with observed trends observed in [station data] and appear to be unrelated to a climate change signal.
Figure 5: Annual anomalies of consecutive wet (left) and dry days (right).
Total Precipitable Water
The total amount of precipitable water over Central Europe has reached very high levels in 2014. The left graph shows the seasonal cycle in the total amount of precipitable water over central Europe for the years 2001-2011 in grey, with the mean value stippled and the 10th and 90th percentiles dashed. In July 2014 and since September of this year, the amount of precipitable water in the atmosphere is at or above the 90th percentile. The high amount of precipitable water suggests a relation between the high temperatures over Europe and the amount of moisture in the atmosphere. Autumn is a period with sustained high levels of total amount of precipitable water, showing high levels of the anomalous values in excess of 3 times the standard deviation, in an area covering northern Italy, Croatia, Hungary, the Czech Republic and parts of Germany and Poland.
Figure 6: Averaged (left) and Standardized autumn anomaly (right) of total precipitable water over Central Europe.
Frost days (FD) and Tropical nights (TR)
FD is defined as the number of days in a given period where: TN < 0°C, while TR is defined as: TN > 20°C. A decrease in the number of Frost Days is observed in Southern Scandinavia, southeast France, the Alpine region, northern Italy and countries on the Adriatic coast. For the rest of Europe there are no distinct deviations from the climatology. The annual anomaly in the number of Tropical Nights suggest a decrease in the frequency of TR in southwest Iberian peninsula and north Italy. Similar to FD anomaly, TR for almost the entire Europe does not present strong deviations from the average.
Figure 7: Annual anomaly of frost days (left) and tropical nights (TR).
Ice Days (ID)
ID is defined as the number of days where the maximum temperature drops below 0°C. The number of ice days in 2014 is below-average in most Scandinavia and some parts of eastern Europe. A similar behaviour is present in the Alpine region, south Germany, Austria, Czech Republic, Slovakia, Romania and a southeastern zone from Croatia towards Bulgaria and Turkey.
Figure 8: Annual anomaly of ice days.