Fog Spatial Distributions over the Central Namib Desert - An Isotope Approach

Fog is a characteristic feature of the Namib Desert and is essential to life in this fog dependent system. It is often acknowledged that advective fog from the ocean is the dominant fog type over the Namib Desert fog-zone but recent evidence suggests that other fog types occur in this area. Knowledge of the existence and spatial distribution of different fog types will enhance the mechanistic understanding of fog formation and potential changes in this region, but such knowledge is limited in literature. In this study, we investigated fog spatial variations within the Namib Desert fog-zone by applying stable isotope (δ18O and δ2H) techniques to differentiate various fog types and identify their source waters. Isotope based results showed that at least three types of fog (advective, radiation and mixed) occurred in this region and what appears as a single fog event may include all three types. Results suggest that radiation fog was the dominant fog type during our study period. The results also suggest that advective fog (with Atlantic Ocean origins) either dissipated 30–50 km inland and the residual humidity combined with locally derived moisture to form mixed fog or advective fog incorporated local moisture along its trajectory inland resulting in mixed fog. Fog in the Namib Desert was consistently depleted in 18O and 2H compared to rainfall and this was attributed to sub-cloud evaporation of the rainfall as well as different sources of fog and rainfall. Sub-cloud evaporation led to enrichment of 18O and 2H in rainfall beyond that of the first stage condensate, fog. Advective fog is often considered the architect of the fog-zone in the Namib Desert, but our results demonstrated multiple dominant fog types during the study period, suggesting knowledge of both fog frequency and fog type is needed to better predict climate change impacts on the fog-zone

Thermoregulatory behavior and high thermal preference buffer impact of climate change in a Namib Desert lizard

Knowledge of the thermal ecology of a species can improve model predictions for temperature‐induced population collapse, which in light of climate change is increasingly important for species with limited distributions. Here, we use a multi‐faceted approach to quantify and integrate the thermal ecology, properties of the thermal habitat, and past and present distribution of the diurnal, xeric‐adapted, and active‐foraging Namibian lizard Pedioplanis husabensis (Sauria: Lacertidae) to model its local extinction risk under future climate change scenarios. We asked whether climatic conditions in various regions of its range are already so extreme that local extirpations of P. husabensis have already occurred, or whether this micro‐endemic species is adapted to these extreme conditions and uses behavior to mitigate the environmental challenges. To address this, we collected thermoregulation and climate data at a micro‐scale level and combined it with micro‐ and macroclimate data across the species’ range to model extinction risk. We found that P. husabensis inhabits a thermally harsh environment, but also has high thermal preference. In cooler parts of its range, individuals are capable of leaving thermally favorable conditions—based on the species’ thermal preference—unused during the day, probably to maintain low metabolic rates. Furthermore, during the summer, we observed that individuals regulate at body temperatures below the species’ high thermal preference to avoid body temperatures approaching the critical thermal maximum. We find that populations of this species are currently persisting even at the hottest localities within the species’ geographic distribution. We found no evidence of range shifts since the 1960s despite a documented increase in air temperatures. Nevertheless, P. husabensis only has a small safety margin between the upper limit of its thermal preference and the critical thermal maximum and might undergo range reductions in the near future under even the most moderate climate change scenarios

Probing the Fog Life Cycles in the Namib Desert

An intensive observation period was conducted in September 2017 in the central Namib, Namibia, as part of the project Namib Fog Life Cycle Analysis (NaFoLiCA). The purpose of the field campaign was to investigate the spatial and temporal patterns of the coastal fog that occurs regularly during nighttime and morning hours. The fog is often linked to advection of a marine stratus that intercepts with the terrain up to 100 km inland. Meteorological data, including cloud base height, fog deposition, liquid water path, and vertical profiles of wind speed/direction and temperature, were measured continuously during the campaign. Additionally, profiles of temperature and relative humidity were sampled during five selected nights with stratus/fog at both coastal and inland sites using tethered balloon soundings, drone profiling, and radiosondes. This paper presents an overview of the scientific goals of the field campaign; describes the experimental setup, the measurements carried out, and the meteorological conditions during the intensive observation period; and presents first results with a focus on a single fog event