High-frequency Temperature Variability Research Articles

Impact of the Tibetan Plateau on Global High-frequency Temperature Variability

Abstract The Tibetan Plateau’s (TP) topography has long been recognized for its impact on climate. However, recognition of the influence of the TP on global weather variability remains insufficient. Therefore, this study used numerical simulations to demonstrate the influences of the TP and its mechanical and thermal forcing on global high-frequency temperature variability and eddy kinetic energy (EKE). Despite local influences, the TP influenced the high-frequency temperature variability in far-flung regions like North America. In summer, the TP’s influence on high-frequency temperature variability showed dipole patterns in Eurasia and tripole patterns in North America, which were mainly induced by TP thermal forcing. In winter, the TP’s influence on high-frequency temperature variability was dominated by mechanical forcing and was less significant for remote regions than in summer. Mechanical forcing dominated EKE in both summer and winter. Furthermore, the horizontal temperature advection dominated the TP’s influence on high-frequency temperature variability for both its thermal effect in summer and its mechanical effect in winter, wherein EKE, as the dynamical factor, determined the horizontal temperature advection rather than the thermodynamical factor, the temperature gradient. Our findings suggest that the TP, via its mechanical and thermal forcing, may have an impact on temperature-related weather extremes around the world.

Oceanic productivity and high-frequency temperature variability—not human habitation—supports calcifier abundance on central Pacific coral reefs

Past research has demonstrated how local-scale human impacts—including reduced water quality, overfishing, and eutrophication—adversely affect coral reefs. More recently, global-scale shifts in ocean conditions arising from climate change have been shown to impact coral reefs. Here, we surveyed benthic reef communities at 34 U.S.-affiliated Pacific islands spanning a gradient of oceanic productivity, temperature, and human habitation. We re-evaluated patterns reported for these islands from the early 2000s in which uninhabited reefs were dominated by calcifiers (coral and crustose coralline algae) and thought to be more resilient to global change. Using contemporary data collected nearly two decades later, our analyses indicate this projection was not realized. Calcifiers are no longer the dominant benthic group at uninhabited islands. Calcifier coverage now averages 26.9% ± 3.9 SE on uninhabited islands (compared to 45.18% in the early 2000s). We then asked whether oceanic productivity, past sea surface temperatures (SST), or acute heat stress supersede the impacts of human habitation on benthic cover. Indeed, we found variation in benthic cover was best explained not by human population densities, but by remotely sensed metrics of chlorophyll-a, SST, and island-scale estimates of herbivorous fish biomass. Specifically, higher coral and CCA cover was observed in more productive waters with greater biomass of herbivores, while turf cover increased with daily SST variability and reduced herbivore biomass. Interestingly, coral cover was positively correlated with daily variation in SST but negatively correlated with monthly variation. Surprisingly, metrics of acute heat stress were not correlated with benthic cover. Our results reveal that human habitation is no longer a primary correlate of calcifier cover on central Pacific island reefs, and highlight the addition of oceanic productivity and high-frequency SST variability to the list of factors supporting reef builder abundance.

Urbanization effects on high-frequency temperature variability over South China

While previous studies mainly focused on low-frequency variabilities of mean or extreme temperature, it remains unclear how the high-frequency variability (HFV) of temperature changes within few days and to what degree local urbanization contributes to these changes. In this study, we examine the changes of temperature HFVs over South China and quantify their urbanization effects. We find that the HFV there shows a discernible spatial dependence with higher values in northern inland and lower in southern coastal regions. The study area has experienced increasing HFV trends since the 1980s, and these trends are especially stronger in highly developed regions, e.g., the Pearl River Delta. We further estimate that urbanization induces additional intensifying effects of 0.06, 0.10, and 0.10 °C/100 yr for HFV at the time scales of 1, 2, and 5 days, respectively, and these urbanization effects contribute to 46.2%, 43.5%, and 37.0% of the total trends of HFV in the urban areas. Our findings are helpful for mitigating the increasing threats of HFV and promoting sustainable development in populated urban areas.

Effects of high-frequency temperature variabilities on the morbidity of chronic obstructive pulmonary disease: Evidence in 21 cities of Guangdong, South China

BackgroundWhile temperature changes have been confirmed as one of the contributory factors affecting human health, the association between high-frequency temperature variability (HFTV, i.e., temperature variation at short time scales such as 1, 2, and 5 days) and the hospitalization of chronic obstructive pulmonary disease (COPD) was rarely reported. ObjectivesTo evaluate the associations between high-frequency temperature variabilities (i.e., at 1, 2, and 5-day scales) and daily COPD hospitalization. MethodsWe collected daily records of COPD hospitalization and meteorological variables from 2013 to 2017 in 21 cities of Guangdong Province, South China. A quasi-Poisson regression with a distributed lag nonlinear model was first employed to quantify the effects of two HFTV measures, i.e., the day-to-day (DTD) temperature change and the intraday-interday temperature variability (IITV), on COPD morbidity for each city. Second, we used multivariate meta-analysis to pool the city-specific estimates, and stratified analyses were performed by age and sex to identify vulnerable groups. Then, the meta-regression with city-level characteristics was employed to detect the potential sources of the differences among 21 cities. ResultsA monotonic increasing curve of the overall exposure-response association was observed, suggesting that positive HFTV (i.e., increased DTD and IITV) will significantly increase the risk of COPD admission. Negative DTD was associated with reduced COPD morbidity while positive DTD elevated the COPD risk. An interquartile range (IQR) increase in DTD was associated with a 24% (95% CI: 12–38%) increase in COPD admissions. An IQR increase in IITV0-1 was associated with 18% (95% CI: 7–27%) increase in COPD admissions. Males and people aged 0–64 years appeared to be more vulnerable to the DTD effect than others. Potential sources of the disparity among different cities include urbanization level, sex structure, industry structure, gross domestic product (GDP), health care services, and air quality. ConclusionsThe increases of DTD and IITV have significant adverse impacts on COPD hospitalization. As climate change intensifies, precautions need to be taken to mitigate the impacts of high-frequency temperature changes.

A Regional Approach for Investigation of Temporal Precipitation Changes

Climatic variability is one of the fundamental aspects of the climate. Our scope of knowledge of this variability is limited by unavailable long-term high-resolution spatial data. Climatic simulations indicate that warmer climate increases extreme precipitations but decreases high-frequency temperature variability. As an important climatologic variable, the precipitation is reported by the IPCC to increase in mid and high altitudes and decrease in subtropical areas. On a regional scale, such a change needs spatio-parametric justification. In this regard, a regionalization approach relying on frequency characteristics and parameters of heavy precipitation may provide better insight into temporal precipitation changes, and thus help us to understand climatic variability and extremes. This study introduces the “index precipitation method”, which aims to define hydrologic homogeneous regions throughout which the frequency distribution of monthly maximum hourly precipitations remains the same and, therefore, investigate whether there are significant temporal precipitation changes in these regions. Homogenous regions are defined based on L-moment ratios of frequency distributions via cluster analysis and considering the spatial contiguity of gauging sites via GIS. Regarding the main hydrologic characteristics of heavy precipitation, 12 indices are defined in order to investigate the existence of regional trends by means of t- and Mann–Kendall tests for determined homogenous regions with similar frequency behaviors. The case study of Japan, using hourly precipitation data on 150 gauges for 1991–2010, shows that trends that statistically exist for single-site observations should be regionally proved. Trends of heavy precipitation have region-specific properties across Japan. Homogenous regions beneficially define statistically significant trends for heavy precipitation.

Night-Time Temperature Reprieves Enhance the Thermal Tolerance of a Symbiotic Cnidarian

Responses of cnidarian-Symbiodiniaceae associations to warming are determined, in part, by high-frequency temperature variability. Yet, the role of such variability in determining specific maximum temperature thresholds of cnidarian holobionts (the ecological units comprised of cnidarian hosts and associated microorganisms, including Symbiodiniaceae) remains untested. Here we contrasted the thermal resilience (that is the ability to resist stress) of a model symbiotic cnidarian from the Red Sea (jellyfish of the genus Cassiopea) under stable and diel oscillating temperature conditions that provide night-time reprieves from daily maximum temperatures. Holobionts were subjected to two thermal trajectories; one that increased but plateaued at 2 °C below identified bleaching thresholds and another that increased incrementally until holobionts bleached. We used behavior, growth, photochemical efficiency, Symbiodiniaceae (symbiont) cell density, and total chlorophyll cell content to characterize thermal resilience and examined Symbiodiniaceae community composition responses at 1 and 13 days of exposure, and post-bleaching. Lower night-time temperatures, resulting in lower daily mean temperatures, allowed holobionts to withstand daily maximum temperatures close to their bleaching thresholds for two extra days than those under stable maximum temperature conditions. Lower night-time temperatures increased the bleaching threshold of the holobionts, whereby holobionts exposed to night-time thermal reprieves tolerated a more extreme daily mean temperature of 40.6 oC and reached a daily thermal maxima 4 oC higher than those under stable temperature conditions. However, post-bleaching observations indicate that night-time temperature reprieves did not prevent symbiont cell or pigment loss. Symbiodiniaceae communities were unaffected by lower night-time temperatures and no directional changes indicative of symbiont shuffling/ selection of thermally tolerant lineages were observed. We show that stable experimental treatments may fail to accurately identify maximum thermal thresholds of non-calcifying cnidarians and limit their relevance to in situ environments that are often characterized by high levels of temperature fluctuations.

High frequency temperature variability reduces the risk of coral bleaching

Coral bleaching is the detrimental expulsion of algal symbionts from their cnidarian hosts, and predominantly occurs when corals are exposed to thermal stress. The incidence and severity of bleaching is often spatially heterogeneous within reef-scales (<1 km), and is therefore not predictable using conventional remote sensing products. Here, we systematically assess the relationship between in situ measurements of 20 environmental variables, along with seven remotely sensed SST thermal stress metrics, and 81 observed bleaching events at coral reef locations spanning five major reef regions globally. We find that high-frequency temperature variability (i.e., daily temperature range) was the most influential factor in predicting bleaching prevalence and had a mitigating effect, such that a 1 °C increase in daily temperature range would reduce the odds of more severe bleaching by a factor of 33. Our findings suggest that reefs with greater high-frequency temperature variability may represent particularly important opportunities to conserve coral ecosystems against the major threat posed by warming ocean temperatures.

High-frequency temperature variability mirrors fixed differences in thermal limits of the massive coral Porites lobata.

Spatial heterogeneity in environmental characteristics can drive adaptive differentiation when contrasting environments exert divergent selection pressures. This environmental and genetic heterogeneity can substantially influence population and community resilience to disturbance events. Here, we investigated corals from the highly variable back-reef habitats of Ofu Island in American Samoa that thrive in thermal conditions known to elicit widespread bleaching and mortality elsewhere. To investigate the relative importance of acclimation versus site of origin in shaping previously observed differences in coral tolerance limits at Ofu Island, specimens of the common Indo-Pacific coral Porites lobata from locations with differing levels of thermal variability were acclimated to low and high thermal variation in controlled common garden aquaria. Overall, there were minimal effects of the acclimation exposure. Corals native to the site with the highest level of daily variability grew fastest, regardless of acclimation treatment. When exposed to lethal thermal stress, corals native to both variable sites contained elevated levels of heat shock proteins and maintained photosynthetic performance for 1-2 days longer than corals from the stable environment. Despite being separated by <5 km, there was significant genetic differentiation among coral colonies (FST=0.206, P<0.0001; nuclear ribosomal DNA), whereas Symbiodiniaceae were all Cladocopium sp. (ITS type C15). Our study demonstrates consistent signatures of adaptation in growth and stress resistance in corals from naturally thermally variable habitats, suggesting that differences in the amount of thermal variability may be an important contributor to adaptive differentiation in reef-building corals.

Influence of freshwater discharges and tides on the abundance and distribution of larval and juvenile Munida gregaria in the Baker river estuary, Chilean Patagonia

Zooplankton time series collected with different temporal resolution and coverage were examined to characterize seasonal and diel patterns in the abundance of Munida gregaria larvae and juveniles in the Baker river estuary. Zoeae were more abundant in late winter and spring, coinciding with the season of lower sediment transport and higher primary production in the region. The occurrence of juveniles was exclusively in summer. There was a significant correlation between the abundance of zoeae and high-frequency temperature variability near the pycnocline over periods of 7–20 and 26–30 days prior to each plankton sampling. These time scales of correlation suggest that internal motions may be a proximal environmental cue for lunar rhythms in larval hatching, rather than directly causing the aggregation of larvae at the sampling area. To characterize shorter-term patterns in larval abundance and vertical distribution, stratified samples were collected every 3h over a full late-spring day (November 2008) near one of the monitoring stations. Zoeae were significantly more abundant at 10–25m depth (p=0.039), and changes in depth-integrated abundance of both zoea and megalopae were strongly associated with the tidal cycle. Together, these results suggest that the spatial structure and population dynamics of M. gregaria in this region may respond to the combined forcing of seasonal changes in freshwater inputs, tidally-driven processes such as lateral transport of larvae and juveniles, and internal-wave mediated changes in local conditions.

Temperature variability at Dürres Maar, Germany during the Migration Period and at High Medieval Times, inferred from stable carbon isotopes of &amp;lt;i&amp;gt;Sphagnum&amp;lt;/i&amp;gt; cellulose

Abstract. This paper presents a high resolution reconstruction of local growing season temperature (GST) anomalies at Dürres Maar, Germany, spanning the last two millennia. The GST anomalies were derived from a stable carbon isotope time series of cellulose chemically extracted from Sphagnum leaves (δ13Ccellulose) separated from a kettle-hole peat deposit of several metres thickness. The temperature reconstruction is based on the Sphagnum δ13Ccellulose/temperature dependency observed in calibration studies. Reconstructed GST anomalies show considerable centennial and decadal scale variability. A cold and presumably wet phase with below-average temperature is reconstructed between the 4th and 7th century AD which is in accordance with the so called European Migration Period, marking the transition from the Late Roman Period to the Early Middle Ages. At High Medieval Times, the amplitude in the reconstructed temperature variability is most likely overestimated; nevertheless, above-average temperatures are obvious during this time span, which are followed by a temperature decrease. On the contrary, a pronounced Late Roman Climate Optimum, often described as similarly warm or even warmer as medieval times, could not be detected. The temperature signal of the Little Ice Age (LIA) is not preserved in Dürres Maar due to considerable peat cutting that takes place in the first half of the 19th century. The local GST anomalies show a remarkable agreement to northern hemispheric temperature reconstructions based on tree-ring datasets and are also in accordance with climate reconstructions on the basis of lake sediments, glacier advances and retreats, and historical datasets. Most notably, e.g., during the Early Middle Ages and at High Medieval Times, temperatures were neither low nor high in general. Rather high frequency temperature variability with multiple narrow intervals of below- and above-average temperatures at maximum lasting a few decades are reconstructed. Especially the agreements between our estimated GST anomalies and temperature reconstructions derived from tree-ring chronologies indicate the great potential of Sphagnum δ13Ccellulose time series from peat deposits for palaeoclimate research. This is particularly the case, given that a quantitative δ13Ccellulose/temperature relationship has been found for several Sphagnum species. Although the time resolution of Sphagnum δ13Ccellulose datasets certainly wouldn't reach the annual resolution of tree-ring data, reconstructions of past temperature variability on the basis of this proxy hold one particular advantage: often due to relatively high peat accumulation rates, especially in kettle-hole bogs accumulated on temperate latitudes over periods of up to several millennia, they allow extending temperature reconstructions based on tree-ring series into the past to enhance our knowledge of natural climate variability during the Holocene.

Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence

Future climate change will likely influence the frequency and intensity of weather extremes. As such events are by definition rare, long records are required to understand their characteristics, drivers, and consequences on ecology and society. Herein we provide a unique perspective on regional-scale temperature extremes over the past millennium, using three tree-ring maximum latewood density (MXD) chronologies from higher elevations in the European Alps. We verify the tree-ring-based extremes using documentary evidences from Switzerland, the Czech Republic, and Central Europe that allowed the identification of 44 summer extremes over the 1550–2003 period. These events include cold temperatures in 1579, 1628, 1675, and 1816, as well as warm ones in 1811 and 2003. Prior to 1550, we provide new evidence for cold (e.g., 1068 and 1258) and warm (e.g., 1333) summers derived from the combined MXD records and thus help to characterize high-frequency temperature variability during medieval times. Spatial coherence of the reconstructed extremes is found over Switzerland, with most signatures even extending across Central Europe. We discuss potential limitations of the tree-ring and documentary archives, including the ( i) ability of MXD to particularly capture extremely warm temperatures, ( ii) methodological identification and relative definition of extremes, and ( iii) placement of those events in the millennium-long context of low-frequency climate change.

Intermittent upwelling and subsidized growth of the scleractinian coral Madracis mirabilis on the deep fore-reef slope of Discovery Bay, Jamaica

A 1 yr study was conducted across a 45 m depth gradient on the north shore of Jamaica to explore the hypothesis that depth-specific variability associated with thermocline oscillations effects growth rates of the scleractinian coral Madracis mirabilis. Multiple periods of high-frequency temperature variability were detected at 30 to 55 m depth, indicative of vertical transport of subther- mocline water onto the reef slope at semidiurnal and shorter intervals. Cooling, expressed as cumu- lative degree-days below the depth-averaged daily temperature increased from 1.6°C d at 10 m to 50°C d at 45 and 55 m depth. The sum of the daily temperature variance increased almost 3-fold from 3.7 to 9.9°C 2 from 10 to 55 m. Coral growth rates showed a bimodal distribution as a function of depth, with fastest growth (3.86 to 4.12 g yr -1 ) at 10 and 30 m, reduced growth (2.46 to 3.21 g yr -1 ) at 20 and 45 m, and slowest growth (0.97 g yr -1 ) at 55 m. To assess possible differences among sites differing with respect to the intensity of internal-wave forcing, growth rates of M. mirabilis were compared at 20 and 30 m depth in Jamaica with previous results from the Florida Keys. Overall growth rates were greater in Florida than in Jamaica, corresponding to greater internal-wave activity in Florida, and a similar effect of enhanced growth at 30 m was observed at both sites. Vertical oscillations of the thermocline are a widespread phenomenon, and may contribute to patterns of coral growth in a variety of deep reef environments.

High frequency variability in recent climate and the north atlantic oscillation

¶High-frequency temperature variability was investigated in the temperature time series measured at Prague-Sporilov (Czech Republic) between 1994–2001. The calculations were performed for time series of surface air temperature averaged for 6-hour intervals. Variability was detected by the method of absolute difference of temperature anomalies between two adjacent discrete time periods. The results indicated a frequency dependence of variability. For 24-hour intervals the variability exhibits an irregular character and decreases with time in the eight-year observation period. Variability time series calculated for the 6-hour intervals did not reveal any significant trend, however, apparent quasi-seasonal oscillations exist. A significant correlation between the North Atlantic Oscillation (NAO) activity and temperature variability can be observed. Higher NAO-index values at all frequencies tend to be associated with higher variability.

Trends in high-frequency climate variability in the twentieth century

HIGH-FREQUENCY climate variability is a fundamental aspect of climate. Understanding climate change demands attention to changes in climate variability and extremes1, but knowledge of the recent behaviour of these variables has been limited by the unavailability of long-term high-resolution data. Climate simulations incorporating increased greenhouse-gas concentrations2-9 indicate that a warmer climate could result in a decrease in high-frequency temperature variability (analogous to the decrease in variability observed from the poles to the tropics, and from winter to summer10) and an increase in the proportion of precipitation occurring in extreme events. Here we analyse high-frequency temperature and precipitation data from hundreds of sites spread over Australia, China, the former Soviet Union and the United States over the past 30 to 80 years. Day-to-day temperature variability is seen to have decreased in the Northern Hemisphere, and-at least within the United States-the proportion of total precipitation contributed by extreme, one-day events has increased significantly. We find that although the notion of a recent increase in interannual temperature variability is supported by data from the past few decades11, the longer data records indicate that this trend is an aberration.