Cities demonstrate higher nocturnal temperatures than surrounding rural areas, which is called “urban heat island” (UHI) effect. Climate change projections also indicate increase in the frequency and intensity of heat waves, which will intensify the UHI effect. As megacity Tehran is affected by severe heatwaves in summer, this study investigates its UHI characteristics and suggests some feasible mitigation strategies in order to reduce the air temperature and save energy. Temperature monitoring in Tehran shows clear evidence of the occurrence of the UHI effect, with a peak in July, where the urban area is circa 6 K warmer than the surrounding areas. The mobile measurements show a park cool island of 6-7 K in 2 central parks, which is also confirmed by satellite images. The effectiveness of three UHI mitigation strategies high albedo material (HAM), greenery on the surface and on the roofs (VEG), and a combination of them (HYBRID) has been studied using simulation with the microscale model ENVI-met. All three strategies show higher cooling effect in the daytime. The average nocturnal cooling effect of VEG and HYBRID (0.92, 1.10 K) is much higher than HAM (0.16 K), although high-density trees show a negative effect on nocturnal cooling.

Wood ticks, Ixodes ricinus L., serve as vectors for various pathogens and are ubiquitous throughout Central Europe. Survival and development of I. ricinus depend on biotic and abiotic factors. We examined whether relative humidity (RH), air (T ) and soil temperatures (T ), or snow depth during November through February affect the questing activity of ticks during their subsequent season of activity. We related the number of host-seeking nymphs to meteorological parameters measured in close proximity at minutely intervals over the period of 6 years (2010-2015) in an urban park in Berlin. We defined thresholds at which associations appeared strongest. Although the annual variations in RH, T , and snow depth were typical of the mid-latitudes, the questing activity of nymphs during their first peak of activity (March through July) varied among the 6 years more than threefold. The accumulated hours of RH below 77% in 2 m height during November through February affected the questing activity of nymphs during the following activity peak. In contrast to T , accumulated hours of T below -1 °C in 0.02 m depth or below -4 °C in 0.05 m depth during the preceding period significantly influenced the average number of nymphs questing during spring. Our observations suggest that RH, T , and snow cover during the preceding months affect the questing activity of nymphal I. ricinus during their first peak of activity. Snow cover serves as an insulator between the atmosphere and soil, which not only stabilizes T but also appears to protect ticks from exposure to frost and frequent temperature shifts.