Seasonality in European Red Dust/“Blood” Rain Events
©2012 American Meteorological Society that most frequent dust-fall events occurred in the summer (Dessens 1990). Burt (1991) found that Great Britain red-rain observations increased from 1968 to 1990, which might be attributed to observational bias due to increasing awareness of the phenomenon. We have assembled a new, more comprehensive red-dust-rain event archive consisting of a listing of 549 colored-rain cases across all of Europe, including specific month/day/year occurrence. A total of 510 of these events occurred after 1900. These colored-rain cases were collected from three primary sources: (a) documented published papers; (b) images of known dust-transport events using satellite data by NASA’s Earth Observatory and other imagery; and (c) limited media accounts of such phenomena. Because we are particularly concerned with seasonality, we selected events linked to terminology such as “blood,” “red,” “dust,” “mud,” or “colored” rain for which existed specific dates and times of year (or, in some cases, simply the month and year of the occurrence). All data, together with the relevant references to each event, can be accessed at http://azclimate.asu.edu/bloodrain.php. Analysis of our spatially and temporally extensive dataset of 549 events suggests that colored-rain events can occur throughout the year across Europe (Fig. 1), but do demonstrate seasonality. Spain tends to receive the most red-dust-rain events due to its close proximity to the source dust from the Sahara. The maximum occurrence of colored-rain events for the Iberian Peninsula region is spring (MAM), but they can occur throughout the year, with winter (DJF) being the least active season for such phenomena. However, for most of Western Europe, red rains occur most frequently in the spring and most infrequently during the summer. An example of the meteorological conditions for summer red rains in Western Europe (particularly Spain, France, and Great Britain) can be seen (Fig. 2) using the NCEP/NCAR Reanalysis dataset for analysis of an event that occurred on 22 June 1988. For this June 1988 red-dust rainfall, the migratory 700-hPa height field (Fig. 2b) over southern Spain and northern Morocco on the day of this Seasonality in European Red Dust/“Blood” Rain Events