Ozone mini‐holes over Valencia (Spain) and their influence on the UV erythemal radiation

Abstract

Low ozone level episodes (also known as mini-holes) have been analysed over Valencia, Spain, during the period from 1 January 2000 to 31 December 2007. In this study, 24 episodes, lasting 1 or 2 days each, were detected. Most of them can be explained dynamically by the existence of an anticyclone over the Azores, which sends air masses coming from the Caribbean over the Iberian Peninsula. A positive anomaly in the vertical temperature profile in the high troposphere and one negative anomaly in the medium and low stratosphere are also observed in most of the analysed episodes. The total ozone column decrease is accompanied by a rise in the UV erythemal radiation levels. This increase is quantified at 1.29 times the decrease in the total ozone column. This is known as the radiation amplification factor (RAF) of UV erythemal radiation.

Are the small-sized plankton communities of oligotrophic ecosystems resilient to UVR and P pulses?

“…From our results, we suggest that only at depths free of UVR and under conditions without P-induced microalgae blooms, would cladoceran biomass generate a high flow of C through the food web, and that rapid phytoplankton turnover rates would be required to sustain this consumer growth (Jeppesen et al 2011). Overall, we conclude that essential ecological processes could be affected by brief (P pulses) and moderate (UVR changes) disturbances, which will occur with greater frequency under upcoming climatic changes foreseeable in the Mediterranean region and related to Saharan dust transport and ozone mini-holes (Alpert et al 2006, Martínez-Lozano et al 2011, Cabrerizo et al 2017. Moreover, our results show, or suggest, that the effect on such ecological processes will be evidenced by the food webs of the smallest members of oligotrophic freshwater systems.…”

“…We calculated individual planktonic biovolumes by the methods published by Hillebrand et al (2002) and converted biovolumes to biomass (lg C) following recommendations by (Menden-Deuer and Lessard 2000). We multiplied the biovolume of zooplankton by 1.1 to obtain wet mass, used a factor of 0.25 to convert wet mass to dry mass, and a factor of 0.40 to transform the dry mass to C content (Reiss and Schmid-Araya 2008, Martínez-Lozano et al 2011, Yvon-Durocher et al 2011).…”

UV Index experimental values on vertical surfaces

“…The aerosol optical depth and the atmospheric moisture are indeed two parameters of great importance for the UVB radiation (nearly as important as the stratospheric ozone), and the authors have analysed them in previous papers (e.g. Esteve et al, 2009Esteve et al, , 2010Martínez-Lozano et al, 2011). However, since the focus of this work is to present long-term measurements of the UVI on vertical planes, and it uses UVER values over vertical and horizontal planes measured simultaneously, we have considered that these effects are the same over both planes, not affecting the final relationship between the radiation for the fixed planes with different inclinations.…”

An assessment of ozone mini-hole representation in reanalyses over the Northern Hemisphere

“…James (1998a) used thresholds computed by subtracting 70 DU from zonally and meridionally averaged monthly means, while Iwao and Hirooka (2006) chose to subtract 80 DU. Koch et al (2005) defined a threshold based on monthly mean values minus 1 standard deviation, while Martínez-Lozano et al (2011) used monthly mean values minus 2 times the standard deviation. In addition to these thresholds, other constraints have been applied: Bojkov and Balis (2001) only considered as miniholes those events with area greater than 500 000 km 2 in the 40-65 • latitude regions, while James (1998a) only considered events found over at least a 5.533 • latitude by 5.625 • longitude region, that is, covering an area equivalent to the ones found by Bojkov and Balis (2001).…”