Cloudy Nights Research Articles

Variation the in relationship between urban tree canopy and air temperature reduction under a range of daily weather conditions

Mitigating heat is a vital ecosystem service of trees, particularly with climate change. Land surface temperature measures captured at a single time of day (in the morning) dominate the urban heat island literature. Less is known about how local tree canopy and impervious surface regulate air temperature throughout the day, and/or across many days with varied weather conditions, including cloud cover. We use bike-mounted air temperature sensors throughout the day in New Haven, Connecticut, USA, from 2019 to 2021 and generalized additive mixed models across 156 rides to estimate the daily variation in cooling benefits associated with tree canopy cover, and warming from impervious surface cover in 90 m buffers surrounding bike observations. Cooling is inferred by subtracting the bicycle-observed temperature from a reference station. The cooling benefits from tree canopy cover were strongest in the midday (11:00–14:00, −1.62 °C), afternoon (14:00–17:00, −1.19 °C), and morning (8:00–11:00, −1.15 °C) on clear days. The cooling effect was comparatively smaller on cloudy mornings −0.92 °C and afternoons −0.51 °C. Warming from impervious surfaces was most pronounced in the evening (17:00–20:00, 1.11 °C) irrespective of clouds, and during cloudy nights (20:00–23:00) and cloudy mornings 1.03 °C 95 % CI [1.03, 1.04]. Among the hottest observed days (top 25th percentile of reference station daily maxima), tree canopy was associated with lower temperatures on clear afternoons −1.78 °C [-1.78, −1.78], cloudy midday −1.17 °C [-1.19, −1.15], clear midday −1.12 °C [-1.12, −1.11]. We add a broader spectrum of weather conditions by explicitly including clouds, and greater temporal resolution by measuring throughout the day to bike-based urban heat research. Future mobile sampling campaigns may broaden the spatial extent with more environmental variation, representing an opportunity for public science and engagement.

Effect of hydration state on locomotor performance and water searching behavior of the terrestrial lungless salamander Bolitoglossa ramosi

AbstractBolitoglossa ramosi is a terrestrial plethodontid salamander particularly active during cloudy nights with high relative humidity in the environment. In this work, we tested the hypotheses that: (1) the hydration state of B. ramosi directly affects its locomotor performance; (2) dehydrated salamanders spend less time to find a water source than hydrated salamanders and (3) dehydrated salamanders find a water source in fewer attempts than hydrated individuals. To evaluate these hypotheses, salamanders at different levels of body hydration were used for an experiment of maximum locomotor performance, and a behavioral assessment test for searching a water source that was randomly located in one of the eight arms of a labyrinth. We found that salamanders hydrated at 95% had a greater locomotor performance (speed) than those hydrated at 85% and 75%. On the other hand, salamanders hydrated at 75% found the water source faster than those hydrated at 95%, although there was not a significant difference between these two groups of salamanders tested in the number of arms visited to find the water source. According to our results, we propose that dehydration in salamanders could be a causal factor for the inactivity of these animals during low levels of environmental humidity, and can also motivate a faster response to find a water source. In addition, we postulate that B. ramosi seems to use a random searching behavior to locate a water source as both hydrated and dehydrated salamanders find it after several attempts.

Skyglow relieves a crepuscular bird from visual constraints on being active

Artificial light at night significantly alters the predictability of the natural light cycles that most animals use as an essential Zeitgeber for daily activity. Direct light has well-documented local impacts on activity patterns of diurnal and nocturnal organisms. However, artificial light at night also contributes to an indirect illumination of the night sky, called skyglow, which is rapidly increasing. The consequences of this wide-spread form of artificial night light on the behaviour of animals remain poorly understood, with only a few studies performed under controlled (laboratory) conditions. Using animal-borne activity loggers, we investigated daily and seasonal flight activity of a free-living crepuscular bird species in response to nocturnal light conditions at sites differing dramatically in exposure to skyglow. We find that flight activity of European Nightjars (Caprimulgus europaeus) during moonless periods of the night is four times higher in Belgium (high skyglow exposure) than in sub-tropical Africa and two times higher than in Mongolia (near-pristine skies). Moreover, clouds darken the sky under natural conditions, but skyglow can strongly increase local sky brightness on overcast nights. As a result, we find that nightjars' response to cloud cover is reversed between Belgium and sub-tropical Africa and between Belgium and Mongolia. This supports the hypothesis that cloudy nights reduce individual flight activity in a pristine environment, but increase it when the sky is artificially lit. Our study shows that in the absence of direct light pollution, anthropogenic changes in sky brightness relieve nightjars from visual constraints on being active. Individuals adapt daily activities to artificial night-sky brightness, allowing them more time to fly than conspecifics living under natural light cycles. This modification of the nocturnal timescape likely affects behavioural processes of most crepuscular and nocturnal species, but its implications for population dynamics and interspecific interactions remain to be investigated.

RMetS Meteorological Masterclass Series: Anticipating floods, droughts and heatwaves

<scp>RMetS M</scp>eteorological <scp>M</scp>asterclass <scp>S</scp>eries: Anticipating floods, droughts and heatwaves

Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)

Context. Ultra-hot Jupiters are the hottest exoplanets that have been discovered so far. Observations begin to provide insight into the composition of their extended atmospheres and their chemical day/night asymmetries. Both are strongly affected by cloud formation. Aims. We explore trends in cloud properties for a sample of five giant gas planets: the hot gas giant WASP-43b and the four ultra-hot Jupiters (UHJs) WASP-18b, HAT-P-7b, WASP-103b, and WASP-121b. This provides a reference frame for cloud properties for the JWST targets WASP-43b and WASP-121b. We further explore chemically inert tracers to observe geometrical asymmetries of UHJs and if the location of the inner boundary of a 3D global circulation model (3D GCM) matters for the clouds that form. Methods. A homogeneous set of 3D GCM results was used as input for a kinetic cloud formation code to evaluate the cloud opacity and gas parameters such as C/O, mean molecular weight, and degree of ionisation. We cast our results in terms of integrated quantities to enable a global comparison between the sample planets. Results. The large day/night temperature differences of UHJs cause the following chemical asymmetries: cloud-free days but cloudy nights, atomic versus molecular gases and their different mean molecular weights, deep thermal ionospheres versus low-ionised atmospheres, and undepleted versus enhanced C/O. WASP-18b, as the heaviest planet in the sample, has the lowest global C/O. Conclusions. The global climate may be considered as similar amongst UHJs, but different to that of hot gas giants. The local weather, however, is individual for each planet since the local thermodynamic conditions, and hence the local cloud and gas properties, differ. The morning and the evening terminator of UHJs will carry signatures of their strong chemical asymmetry such that ingress and egress asymmetries can be expected. An increased C/O ratio is a clear sign of cloud formation, making cloud modelling a necessity when utilising C/O (or other mineral ratios) as a tracer for planet formation. The changing geometrical extension of the atmosphere from the day to the nightside may be probed through chemically inert species such as helium. Ultra-hot Jupiters are likely to develop deep atmospheric ionospheres which may impact the atmosphere dynamics through magneto-hydrodynamic processes.

Cloud cover amplifies the sleep-suppressing effect of artificial light at night in geese.

In modern society the night sky is lit up not only by the moon but also by artificial light devices. Both of these light sources can have a major impact on wildlife physiology and behaviour. For example, a number of bird species were found to sleep several hours less under full moon compared to new moon and a similar sleep-suppressing effect has been reported for artificial light at night (ALAN). Cloud cover at night can modulate the light levels perceived by wildlife, yet, in opposite directions for ALAN and moon. While clouds will block moon light, it may reflect and amplify ALAN levels and increases the night glow in urbanized areas. As a consequence, cloud cover may also modulate the sleep-suppressing effects of moon and ALAN in different directions. In this study we therefore measured sleep in barnacle geese (Branta leucopsis) under semi-natural conditions in relation to moon phase, ALAN and cloud cover. Our analysis shows that, during new moon nights stronger cloud cover was indeed associated with increased ALAN levels at our study site. In contrast, light levels during full moon nights were fairly constant, presumably because of moonlight on clear nights or because of reflected artificial light on cloudy nights. Importantly, cloud cover caused an estimated 24.8% reduction in the amount of night-time NREM sleep from nights with medium to full cloud cover, particularly during new moon when sleep was unaffected by moon light. In conclusion, our findings suggest that cloud cover can, in a rather dramatic way, amplify the immediate effects of ALAN on wildlife. Sleep appears to be highly sensitive to ALAN and may therefore be a good indicator of its biological effects.

Contrasting Influence of Natural Nighttime Illumination on Capture Rates of the American Burying Beetle and Roundneck Burying Beetle (Coleoptera: Silphidae)

Abstract The nocturnal American burying beetle (Nicrophorus americanus Olivier, 1790; Silphidae), once widely distributed in the eastern United States, is currently listed as endangered by the US Fish and Wildlife Service. The factors driving its decline remain largely unknown. Curiously, a closely related and ecologically similar burying beetle, the roundneck burying beetle (Nicrophorus orbicollis Say, 1825), remains abundant and widespread. We used two sets of trapping data from Nebraska and Oklahoma, USA to examine the effects of moon phase and weather on capture rates of the two species. We found that on nights with few clouds, increasing moonlight levels reduced captures of American burying beetles in baited pitfall traps at both sites. In Nebraska, cloud cover reversed the association between moon phase and capture rate (regression line slope became slightly positive). In contrast, in Oklahoma fewer American burying beetles were caught on cloudy nights for all moon phases. We hypothesize this to be ...

Seasonal patterns of nocturnal singing by ovenbirds and white-throated sparrows

AbstractRecent research suggests that many diurnal songbirds also sing at night. The functions of nocturnal singing by diurnally active birds are not well understood. We used automated recorders to record nocturnal singing from May through July 2014. We examined how date, temperature, wind, weather, and lunar phase influenced nocturnal vocal behaviour. We found that nocturnal singing by ovenbirds and white-throated sparrows was related to date with clear seasonal patterns that did not mirror the dawn chorus. Nocturnal singing rates declined seasonally, but peaked earlier for white-throated sparrows than for ovenbirds. Both species sang less often on nights with a full moon or precipitation. Ovenbirds also sang fewer songs on cold and windy nights while white-throated sparrows sang less often on cloudy nights. We show that nocturnal song is shaped by environmental factors and shows a seasonal pattern that may be useful for gaining insights into functions of nocturnal song.

Zernike power spectra of clear and cloudy light-polluted urban night skies

The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V, and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to -3 for clear nights and -2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained on clear nights, is described in the Zernike space.

Svjetlosno onečišćenje grada Zagreba u periodu prosinac 2010. - srpanj 2011.

Svjetlosno onečišćenje povećanje je prirodne vrijednosti osvjetljenja okoliša kao posljedica ljudskog djelovanja. U uvodu članka dajemo pregled uzroka i posljedica svjetlosnog onečišćenja te opisujemo tri osnovne metode mjerenja utjecaja umjetnog osvjetljenja na okolinu. Istraživačka grupa s RGN fakulteta odabrala je jednu od tih metoda kako bi razradila metodologiju mjerenja i obrade rezultata, korisnost mjerenja i stekla uvid u očekivane rezultate budućih mjerenja. Iznosimo opis i rezultat preliminarnog mjerenja osvjetljenja noćnog neba tokom osmomjesečnog perioda, napravljenog instrumentom postavljenim na zgradi Rudarsko-geološko-naftnog fakulteta.

Temporal and environmental influences on the vocal behaviour of a nocturnal bird

Temporal and environmental variation in vocal activity can provide information on avian behaviour and call function not available to short‐term experimental studies. Inter‐sexual differences in this variation can provide insight into selection effects. Yet factors influencing vocal behaviour have not been assessed in many birds, even those monitored by acoustic methods. This applies to the New Zealand kiwi (Apterygidae), for which call censuses are used extensively in conservation monitoring, yet which have poorly understood acoustic ecology. We investigated little spotted kiwi Apteryx owenii vocal behaviour over 3 yr, measuring influences on vocal activity in both sexes from time of night, season, weather conditions and lunar cycle. We tested hypotheses that call rate variation reflects call function, foraging efficiency, historic predation risk and variability in sound transmission, and that there are inter‐sexual differences in call function. Significant seasonal variation showed that vocalisations were important in kiwi reproduction, and inter‐sexual synchronisation of call rates indicated that contact, pair‐bonding or resource defence were key functions. All weather variables significantly affected call rates, with elevated calling during increased humidity and ground moisture indicating a relation between vocal activity and foraging conditions. A significant decrease in calling activity on cloudy nights, combined with no moonlight effect, suggests an impact of light pollution in this species. These influences on vocal activity provide insight into kiwi call function, have direct consequences for conservation monitoring of kiwi, and have wider implications in understanding vocal behaviour in a range of nocturnal birds.

Better in the dark: two Mediterranean amphibians synchronize reproduction with moonlit nights

Abstract. In Amphibians, both positive and negative correlations between activity and full moon phase have been observed. In this study, we present data for two anuran species (Hyla intermedia and Rana dalmatina) studied in a hilly Mediterranean area of central Italy. We analysed, in a two-year survey, the relationships between the number of egg clutches laid each night and the moon phases by means of circular statistics. Moreover, the studied species exhibited clear oviposition site selection behaviour influenced, at least in H. intermedia, by moon phases. We observed the occurrence of an avoidance effect by amphibians for oviposition and specific egg-laying behaviour during moon phases around the full moon. This apparent lunar phobia was evident in both species when yearly data were pooled. On the other hand, while this pattern continued to be also evident in H. intermedia when single years were considered, in R. dalmatina it stood just in one year of study. Nonetheless, during cloudy nights, when moonlight arriving on the ground was low, the frogs' behaviour was similar to that observed in new moon phases. We interpreted the observed pattern as an anti-predatory strategy. Overall, comparisons between our own study and previous research suggest that there was insufficient evidence to establish any unequivocal patterns and that further research in this regard is needed.

Atmospheric extinction properties above Mauna Kea from the Nearby SuperNova Factory spectro-photometric data set

We present a new atmospheric extinction curve for Mauna Kea spanning 3200–9700 Å. It is the most comprehensive to date, being based on some 4285 standard star spectra obtained on 478 nights spread over a period of 7 years obtained by the Nearby SuperNova Factory using the SuperNova Integral Field Spectrograph. This mean curve and its dispersion can be used as an aid in calibrating spectroscopic or imaging data from Mauna Kea, and in estimating the calibration uncertainty associated with the use of a mean extinction curve. Our method for decomposing the extinction curve into physical components, and the ability to determine the chromatic portion of the extinction even on cloudy nights, is described and verified over the wide range of conditions sampled by our large dataset. We demonstrate good agreement with atmospheric science data obtain at nearby Mauna Loa Observatory, and with previously published measurements of the extinction above Mauna Kea.

Nocturnal Continental Low-Level Stratus over Tropical West Africa: Observations and Possible Mechanisms Controlling Its Onset

Abstract Some spatiotemporal characteristics and possible mechanisms controlling the onset of the widespread, low-level nocturnal stratiform clouds that formed during May–October 2006 over southern tropical West Africa are investigated using cloudiness observations from surface weather stations, data from various satellite platforms, and surface-based remote sensing profiles at Nangatchori in central Benin. It is found that the continental stratus is lower than the maritime stratus over the Gulf of Guinea and persists well into the noon hours. For the study period, a clear seasonal cycle was documented, as well as a dependence on latitude with the cloudiest zone north of the coastal zone and south of approximately 9°N. It is also shown that nonprecipitating clear and cloudy nights observed at Nangatchori in central Benin often reflect clearer and cloudier than normal conditions over a wide region of southern West Africa. At Nangatchori, on average the stratus developed at 0236 UTC (about local time) with an extremely low cloud base at 172 m (above ground level) when averaged over all cloudy nights. About 2–3 h before cloudiness onset, a distinct nighttime low-level jet formed that promoted static destabilization and a low Richardson number flow underneath it. The ensuing vertical upward mixing of moisture that accumulated under the near-surface inversion after sunset caused the cloud formation. It is argued that a strong shear underneath the nighttime low-level jet is the major process for cloud formation, but the low-level static stability and the time scale of the shear-driven mixing are other potential factors.

Studies on the bionomics of male Anopheles gambiae Giles and male Anopheles funestus Giles from southern Mozambique

Little is known about the fitness of wild male mosquitoes, the females of which are vectors of malaria. The problem of studying male biology has been exacerbated by difficulties associated with catching them. In southern Mozambique, however, almost the entire adult population of An. funestus and An. gambiae s.l. rest inside houses. They leave in a dusk exodus, which makes them easy to collect. In 8,348 exit collections from a village from 2003 to 2009, 567,195 male An. funestus and 34,591 male An. gambiae s.l. were collected. During the study, numbers of An. funestus increased but numbers of An. gambiae s.l. declined to the point of extinction. Overall numbers of An. gambiae s.l. were positively correlated with temperature, whilst the relationship between temperature and numbers of An. funestus changed from an initially positive one in the first three years of the study to a negative one in the last three years. Marked males were recaptured up to 300 m from the release site, with most recaptures occurring within 150 m. Estimated mean daily survival of male An. funestus was 0.86 (95% C.I. 0.869-0.850). For the years 2003-2007, estimated mean daily survival of male An gambiae s.l. was 0.660 (95% C.I. 0.682-0.638). For either species, there was no relationship between mean weekly temperature and estimated daily survival. These results imply that males of An. funestus live as long as females but have a relatively short flight range. They are discussed in the light of possible release strategies of sterile or genetically modified mosquitoes.

Temperature and Cloud Cover, but Not Predator Urine, Affect Winter Foraging of Mice

AbstractAlthough homeotherms likely experience costs of both predation risk and thermoregulation while foraging, it is unclear how foragers contend with these costs. We used foraging trays placed in sheltered microsites to determine whether temperature, a direct cue of predator presence (predator urine) and an indirect cue of predation risk (cloudy nights) affect foraging of white‐footed mice, Peromyscus leucopus, in winter. Mice were presented with urine from bobcats, Lynx rufus, red foxes, Vulpes vulpes, and coyotes, Canis latrans, an herbivore (whitetailed deer, Odocoileus virginianus), and a water control. To measure rodent foraging, we used seeds of millet mixed with sand to quantify giving‐up densities (the number of seeds left in each foraging tray). Giving‐up density was not affected by predator urine. Rather, rodent foraging was affected by an interaction of temperature and weather. On overcast nights, when predation risk was likely lower, mice foraged more when soil temperature was higher, presumably reducing thermoregulatory costs. On clear nights, foraging was low regardless of soil temperature, presumably because foraging was more risky. These results suggest that mice consider thermoregulatory costs and predation risk when making foraging decisions, and that the indirect cue afforded by weather, rather than the direct cue of predator urine, is among the cues used to make foraging decisions. Moreover, these results suggest that sensitivity to a particular cue is likely to be context‐dependent.

Nocturnal stratiform cloudiness during the West African monsoon

An analysis of METEOSAT satellite images and synoptic reports from Parakou, Benin suggests that those nights that lack deep convection during the West African monsoon are often either completely clear or completely overcast at low levels. Using radiosonde observations gathered at Parakou during the IMPETUS field campaign of the summer of 2002 and ECMWF operational analyses, the composite structure of the atmosphere for both cloudy and clear nights is presented. Cloudy nights are found to occur when turbulent processes result in large-scale speed convergence in the boundary layer and a positive net moisture flux convergence. Conversely, the clear conditions occur when a nocturnal inversion decouples the boundary layer from the surface. The cloudy and clear conditions are also shown to be related to large-scale changes in the configurations of the African Easterly Jet and the Tropical Easterly Jet, although the nature of this relationship remains unclear.

Mathematical models of dependence of surface temperatures of exposed metal plates on environmental parameters

The present paper sets out the mathematical models that control the surface temperature of metal plates during atmospheric exposure. Heat transfer can be modelled by a series of heat transfer coefficients for different thermal processes, i.e. conduction, natural convection, forced convection, radiative heat losses to the sky, radiative heat transfer to or from the ground, incoming solar radiation, and evaporation and condensation. The model is applied to predict the surface temperature of near horizontal galvanised steel plates. Undercooling of a galvanised plate relative to the ambient air, i.e.the extent to which the temperature of the plate falls below that of its surroundings, is calculated for both clear and cloudy nights, with and without a slight breeze. It is found that breezes and clouds significantly decrease the extent of undercooling. The temperature differences between the plate and the ambient air after sunrise are also calculated. It is found that the prime factors controlling the post-sunrise temperature difference are whether the plate is wet or dry, whether the sky is cloudy or clear, and the wind speed. Under certain conditions, the increase in plate temperature relative to the surrounding air may be substantially suppressed. The time for wetted salts and aerosols to dry on plates post-sunrise is calculated and, under those conditions where the rise in temperature difference is suppressed, it may take a number of hours for aerosols to dry out. Estimates of temperature difference are compared with experimental data, and parametric equations for estimating surface temperature are presented. The relevance of the results to models of atmospheric corrosion is discussed.

Air-shower spectroscopy at horizons

Downward cosmic rays are mostly revealed on the ground by their air-showers diluted and filtered secondary μ + μ − traces and/or by their (Cerenkov - Fluorescent) light because of the high altitude numerous and luminous electromagnetic e + e − , γ shower component. Horizontal and upward air-showers are even more suppressed by deeper atmosphere opacity and by the Earth shadows. In such noise-free horizontal and upward directions rare Ultra High Cosmic rays and rarer neutrino induced air-showers may shine, mostly mediated by resonant PeV ν e ̄ + e − → W − interactions in air or by higher energy tau air-showers originated by ν τ skimming the Earth. At high altitude (mountains, planes, balloons) the air density is so rarefied that nearly all common air-showers might be observed at their maximal growth at a tuned altitude and direction. The arrival angle samples different distances and the corresponding most probable primary cosmic ray energy. The larger and larger distances (between observer and C.R. interaction) make wider and wider the shower area and it enlarges the probability of being observed (up to three orders of magnitude more than vertical showers); the observation of a maximal electromagnetic shower development may amplify the signal by two–three orders of magnitude (with respect to a suppressed shower at sea level); the peculiar altitude–angle range (ten–twenty km height and ≃ 8 0 ∘ – 9 0 ∘ zenith angle) may disentangle at best the primary cosmic ray energy and composition. Even from existing mountain observatories the up-going air-showers may trace, above the horizons, PeV–EeV high energy cosmic rays and, below the horizons, PeV–EeV neutrino astronomy: their early signals may be captured in already existing gamma telescopes such as Magic at Canarie, while facing the Earth edges during (useless) cloudy nights.

The Relationship between Urban-Rural Water Vapor Pressure Differences and the Population Sizes of Settlements in Saku, Nagano, Japan

This paper presents the relationship between urban-rural vapor pressure differences and population size for six settlements in Saku, Nagano Prefecture, Japan, from April 1998 to March 1999. Data were collected using a circuit-type, automobile-based travel method. The water vapor pressure in urban areas was less than that in rural areas almost year-round. The mean value of urban-rural vapor pressure differences was -1.4 hPa on fine days, which was twice larger than values for cloudy and fine nights. The regression line of mean urban-rural vapor pressure differences to settlement population size for cloudy nights was similar to that for fine nights. The mean value of the urban-rural water vapor pressure difference in summer was -1.7 hPa, a value nearly twice that in winter. Mean urban-rural water vapor pressure differences for fine days, fine nights, and cloudy nights related to the logarithm of the settlement population size. Regression line slopes for cloudy and fine nights showed no differences. However, the slope for fine days was twice that of fine and cloudy nights. Finally, the relationship between the annual maximum urban-rural water vapor pressure difference and the logarithm of population size was remarkably steady with R2 > 0.77.