Spatiotemporal Inhomogeneity of Trends in Dry and Moist Heatwave Across Northern Hemisphere: Regional Variability and Driving Mechanisms

The response of the atmospheric winter circulation in both hemispheres to changes in the meridional gradient of sea surface temperature (SST) is examined in an atmospheric general circulation model. Climatological SSTs are employed for the control run. The other runs differ in that a zonally symmetric component is added to or subtracted from the climatological SST field. The meridional structure of the variation in SST gradient is based on the observed change in zonally averaged SST over the last century. The SST trend has maxima of about 1 K at high latitudes of both hemispheres. Elsewhere, the increase in SST over the last century is fairly uniform at about 0.5 K. In both hemispheres the response to decreased SST gradients is decreased baroclinity in the lower troposphere and increased baroclinity in the upper troposphere, with the reverse response when the SST gradient is increased. Because the cases with decreased SST gradients correspond to warmer SSTs everywhere, they are accompanied by an increase in moisture and a general expansion of the troposphere. The warming cases in the Northern Hemisphere (NH) winter are marked by greatly increased tropical convection, a stronger subtropical jet that is shifted upward and equatorward, and a robust stationary-wave response. Many aspects of the response are remarkably consistent among the different warming experiments, both in pattern and amplitude. The storm-track response is weaker but still consistent among the different warming experiments. Despite general decrease in storm-track activity, there is a tendency for the upper-level NH storm tracks to strengthen at their downstream end and to weaken at their upstream and northward end. When the zonally symmetric SST anomaly field is subtracted from the climatological SST (resulting in lower SST with increased latitudinal gradient), the response is different in many fields and is considerably weaker. In the winter Southern Hemisphere the change in baroclinity of the low-level flow plays a greater role in the response than in the winter NH. The response in the storm track is zonal with a decrease in midlatitude storm-track activity in the warming cases and an increase in the case that has an increased SST gradient (and cooler SST). There is close correspondence between the pattern of response in all the experiments, irrespective of the sign of the SST anomaly field.

The primary focus of this paper is the analysis of the roles of long-term increases in carbon dioxide (CO2) and sea surface temperatures (used as indicators of climate change) and man-made halocarbons (indicators of chemical ozone depletion linked to halogens) in explaining the observed trend of ozone in the tropical lower stratosphere and implications for related variables including temperature and tropopause height. Published estimates indicate a decrease of approximately 10% in observed ozone concentrations in this region between 1979 and 2005. Using a coupled chemistry–climate atmosphere model forced by observed sea surface temperatures and surface concentrations of long-lived greenhouse gases and halocarbons, the authors show that the simulations display substantial decreases in tropical ozone that compare well in both latitudinal and vertical structure with those observed. Based on sensitivity simulations, the analysis indicates that the decreases in the lower stratospheric (85–50 hPa) tropical ozone distribution are mostly associated with increases in CO2 and sea surface temperatures, in contrast to those at higher latitudes, which are largely driven by halocarbon increases. Factors influencing temperature trends and tropopause heights in this region are also probed. It is shown that the modeled temperature trends in the lower tropical stratosphere are also associated with increases in CO2 and sea surface temperatures. Following the analysis of lower stratospheric tropical temperature trends, the secondary focus of this paper is on related changes in tropopause height. Much of the simulated tropopause rise in the tropical zone as measured by tropopause height is found to be linked to increases in sea surface temperatures and CO2, while increases in halocarbons dominate the tropopause height changes in the subtropics near 30°; both drivers thus affect different regions of the simulated changes in the position of the tropopause. Finally, it is shown that halocarbon increases dominate the changes in the width of the region where modeled total ozone displays tropical character (as indicated by low values of the column abundance). Hence the findings suggest that climate changes and halocarbon changes make different contributions to different metrics used to characterize tropical change.

The critical consequence of climate change resulting from global warming is the increase in temperature. In combined cycle power plants (CCPPs), the Electric Power Output (PE) is affected by changes in both Ambient Temperature (AT) and Sea Surface Temperature (SST), particularly in plants utilizing seawater cooling systems. As AT increases, air density decreases, leading to a reduction in the mass of air absorbed by the gas turbine. This change alters the fuel–air mixture in the combustion chamber, resulting in decreased turbine power. Similarly, as SST increases, cooling efficiency declines, causing a loss of vacuum in the condenser. A lower vacuum reduces the steam expansion ratio, thereby decreasing the Steam Turbine Power Output. In this study, the effects of increases in these two parameters (AT and SST) due to global warming on the PE of CCPPs are investigated using various regression analysis techniques, Artificial Neural Networks (ANNs) and a hybrid model. The target variables are condenser vacuum (V), Steam Turbine Power Output (ST Power Output), and PE. The relationship of V with three input variables—SST, AT, and ST Power Output—was examined. ST Power Output was analyzed with four input variables: V, SST, AT, and relative humidity (RH). PE was analyzed with five input variables: V, SST, AT, RH, and atmospheric pressure (AP) using regression methods on an hourly basis. These models were compared based on the Coefficient of Determination (R2), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), and Root Mean Square Error (RMSE). The best results for V, ST Power Output, and PE were obtained using the hybrid (LightGBM + DNN) model, with MAE values of 0.00051, 1.0490, and 2.1942, respectively. As a result, a 1 °C increase in AT leads to a decrease of 4.04681 MWh in the total electricity production of the plant. Furthermore, it was determined that a 1 °C increase in SST leads to a vacuum loss of up to 0.001836 bara. Due to this vacuum loss, the steam turbine experiences a power loss of 0.6426 MWh. Considering other associated losses (such as generator efficiency loss due to cooling), the decreases in ST Power Output and PE are calculated as 0.7269 MWh and 0.7642 MWh, respectively. Consequently, the combined effect of a 1 °C increase in both AT and SST results in a 4.8110 MWh production loss in the CCPP. As a result of a 1 °C increase in both AT and SST due to global warming, if the lost energy is to be compensated by an average-efficiency natural gas power plant, an imported coal power plant, or a lignite power plant, then an additional 610 tCO2e, 11,184 tCO2e, and 19,913 tCO2e of greenhouse gases, respectively, would be released into the atmosphere.

Abstract. Temperature and ozone changes in the upper troposphere and lower stratosphere (UTLS) are important components of climate change. In this paper, variability and trends of temperature and ozone in the UTLS are investigated for the period 2002–2017 using high-quality, high vertical resolution Global Navigation Satellite System radio occultation (GNSS RO) data and improved merged satellite data sets. As part of the Stratosphere-troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP), three reanalysis data sets, including the ERA-I, MERRA2 and the recently released ERA5, are evaluated for their representation of temperature and ozone in the UTLS. The recent temperature and ozone trends are updated with a multiple linear regression (MLR) method and related to sea surface temperature (SST) changes based on model simulations made with NCAR's Whole Atmosphere Community Climate Model (WACCM). All reanalysis temperatures show good agreement with the GNSS RO measurements in both absolute value and annual cycle. Interannual variations in temperature related to Quasi-Biennial Oscillation (QBO) and the El Niño–Southern Oscillation (ENSO) processes are well represented by all reanalyses. However, evident biases can be seen in reanalyses for the linear trends of temperature since they are affected by discontinuities in assimilated observations and methods. Such biases can be corrected and the estimated trends can be significantly improved. ERA5 is significantly improved compared to ERA-I and shows the best agreement with the GNSS RO temperature. The MLR results indicate a significant warming of 0.2–0.3 K per decade in most areas of the troposphere, with a stronger increase of 0.4–0.5 K per decade at midlatitudes of both hemispheres. In contrast, the stratospheric temperature decreases at a rate of 0.1–0.3 K per decade, which is most significant in the Southern Hemisphere (SH). Positive temperature trends of 0.1–0.3 K per decade are seen in the tropical lower stratosphere (100–50 hPa). Negative trends of ozone are found in the Northern Hemisphere (NH) at 150–50 hPa, while positive trends are evident in the tropical lower stratosphere. Asymmetric trends of ozone can be found in the midlatitudes of two hemispheres in the middle stratosphere, with significant ozone decrease in the NH and increase in ozone in the SH. Large biases exist in reanalyses, and it is still challenging to do trend analysis based on reanalysis ozone data. According to single-factor-controlled model simulations with WACCM, the temperature increase in the troposphere and the ozone decrease in the NH stratosphere are mainly connected to the increase in SST and subsequent changes of atmospheric circulations. Both the increase in SSTs and the decrease in ozone in the NH contribute to the temperature decrease in the NH stratosphere. The increase in temperature in the lower stratospheric tropics may be related to an increase in ozone in that region, while warming SSTs contribute to a cooling in that area.

Abstract. Changes in snow water equivalent (SWE) over Northern Hemisphere (NH) landmasses are investigated for the early (2016–2035), middle (2046–2065) and late (2080–2099) 21st century using a multi-model ensemble from 20 global climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The multi-model ensemble was found to provide a realistic estimate of observed NH mean winter SWE compared to the GlobSnow product. The multi-model ensemble projects significant decreases in SWE over the 21st century for most regions of the NH for representative concentration pathways (RCPs) 2.6, 4.5 and 8.5. This decrease is particularly evident over the Tibetan Plateau and North America. The only region with projected increases is eastern Siberia. Projected reductions in mean annual SWE exhibit a latitudinal gradient with the largest relative changes over lower latitudes. SWE is projected to undergo the largest decreases in the spring period where it is most strongly negatively correlated with air temperature. The reduction in snowfall amount from warming is shown to be the main contributor to projected changes in SWE during September to May over the NH.

Influences of replacing dietary fish meal by Antarctic krill meal on growth performance, immunity and muscle quality of white shrimp Litopenaeus vannamei

To describe age and time trends in added sugar, free sugar and total sugar intake among German 3-18-year-olds. Overall, 10,761 3-day dietary records kept between 1985 and 2016 by 1312 DONALD participants (660 boys, 652 girls) were analysed (%E) using polynomial mixed-effects regression models. TS intake decreased with age (♂: linear, quadratic and cubic trend all p < 0.0098; ♀: linear trend p < 0.0001). While the oldest children had the lowest FS intake (linear, quadratic trend: p < 0.0001), the youngest children had the lowest AS intake (linear, quadratic trend p < 0.0001, cubic trend p = 0.0004). In terms of time trends, TS (♂: cubic trend p = 0.0052; ♀: quadratic trend p = 0.0608, cubic trend p = 0.0014) and FS (quadratic trend p = 0.0163, cubic trend p < 0.0001) intake increased between 1985 and 2005 and decreased thereafter, most notably since 2010. AS intake decreased between 1985 and 1995, increased slightly until 2005 and decreased thereafter, most notably since 2010 (linear, quadratic, cubic trend p < 0.0001). FS intake exceeded 10%E/day throughout the 30-year study period. Our results do not support the common assumptions that sugar intake is on the rise and generally higher among adolescents than among younger children. Of note, TS, AS and FS intakes have decreased in the last decade among all age groups. Nevertheless, FS intake still exceeds the intake level recommended by the WHO.

A suite of semiidealized numerical experiments are conducted to investigate the sensitivity of tropical cyclone (TC) intensity to changes of sea surface temperature (SST) over different radial extents. It is found that the increase of inner SST within the range 1.5–2.0 times the radius of maximum wind (RMW), defined as the effective radius (ER), contributes greatly to the increase of TC intensity and the reduction of TC inner‐core size, whereas the increase of outer SST (defined as SST outside the ER) reduces TC intensity and increases TC inner‐core size. Further analysis suggests that the effects of SST inside and outside the ER on TC intensity rely on the factors that influence the TC development. As the SST increases inside the ER, more surface enthalpy flux enters the TC eyewall and less enters the outer spiral rainbands. This will decrease the RMW, leading to a smaller eyewall radius where strong latent heating is released. As a result, the central pressure of the TC deepens with stronger radial pressure gradient. Meanwhile, the difference between SST and upper tropospheric temperature increases. All factors above contribute to TC intensification as the inner SST increases. The opposite happens as the SST increases outside the ER. How TC intensity responds to the change of the entire SST depends on the competitive and opposite effects of inner and outer SST. Moreover, understanding the mechanisms is vital to the forecast of variations in TC intensity and inner‐core size when a TC comes across an ocean cold or warm pool.

The relative abundance of summer flounder (Paralichthys dentatus) differs over space and time with changes in environmental factors, such as depth, bottom temperature, sea surface temperature (SST) and bottom salinity. We use the integrated nested Laplace approximation (INLA) approach to account for the random effects arising from either over-dispersion, or spatial and temporal autocorrelation. We explore how the different assumptions in the spatial temporal models result in varying model predictions. The results indicate that the distribution of summer flounder is correlated with depth, regional increases in bottom temperature, SST and bottom salinity. We find that in the Fall relative abundance increased 10–15% with a 1∘C increase in SST, by 12% with each 1∘C increase in bottom temperature and 3–4% with each meter increase in depth across all models. In the spring, relative abundance increased by about 30% with each 1∘C increase in SST with an upper preferred temperature between 10-20∘C. Our study also shows that models that include spatio-temporally correlated variables can inadvertently be over parameterized when including higher order interaction terms between spatial and temporal random effects. This can lead to inflated variances in the estimates and predictions as well as lengthening model convergence times. Therefore, care should be taken in identifying the level of model complexity given the indirect implications of these results on fisheries management and marine ecology.

Based on the analysis of satellite data from 1982 to 2021 with a spatial resolution of about 0.05° × 0.05°, the total increase in the Black Sea surface temperature was confirmed. Annual temperature averaged over the entire Black Sea rises with the rate of about 0.6°C/10 years. The annual temperature increment due to the linear trend is at a maximum in May–June. In these months of the hydrological spring, the rate of increase in sea surface temperature (SST) is about one and a half times greater than in October–November. For most of the year, the general warming of the surface water layer is not accompanied by a significant increase in the intra-monthly SST variance. Such an increase is observed only in some months of the transition seasons, especially during the hydrological spring, when the absolute magnitude of extreme thermal anomalies and their area significantly increases. The maximum amplitudes of interannual variations of SST are confined to the northwestern part of the Black Sea. Changes in atmospheric pressure and wind fields significantly impact on the spatiotemporal SST structure of the. Long-term trends of driving pressure above the Black Sea indicate an intensification of regional cyclonic activity in the atmosphere (especially pronounced since 2009), which leads to increased generation of the negative SST anomalies of significant amplitude. Such anomalies occur mainly in the warm half-year (especially in May and October) due to the development of wind-driven upwelling. The May and October negative SST anomalies from the range of –(6–5)°C are characterized by maximum areas. Warm anomalies are also most often recorded in May and (to a lesser extent) in October. They are generated by abnormal heat fluxes on the sea surface, including in shallow areas of the shelf and spread to open areas of the Black Sea due to horizontal advection of mainly wind origin. The described patterns of spatio-temporal SST variability and their causes are illustrated by a case-study of extreme thermal anomalies using comprehensive analysis of wind and SST fields of high spatial resolution.

Effects of varying protein and lipid levels, with or without the addition of L-carnitine supplementation on growth performance and nutrient utilization of Asian Seabass (Lates calcarifer) reared in recirculating aquaculture system

Seasonal prediction of heat wave variability is a scientific challenge and of practical importance. This study investigates the heat wave frequency (HWF) variability over North America (NA) during the past 53 summers (1958–2010). It is found that the NA HWF is dominated by two distinct modes: the interdecadal (ID) mode and the interannual (IA) mode. The ID mode primarily depicts a HWF increasing pattern over most of the NA continent except some western coastal areas. The IA mode resembles a tripole HWF anomaly pattern with three centers over the northwestern, central, and southern NA. The two leading modes have different dynamic structures and predictability sources. The ID mode is closely associated with the prior spring sea surface temperature anomaly (SSTA) in the tropical Atlantic and tropical western Pacific that can persist throughout the summer, whereas the IA mode is linked to the development of El Niño–Southern Oscillation. A simplified general circulation model is utilized to examine the possible physical mechanism. For the ID mode the tropical Atlantic SSTA can induce a Gill‐type response which extends to NA, while the northwestern Pacific SSTA excites a Rossby wave train propagating eastward toward NA. These two flow patterns jointly contribute to the formation of the large‐scale circulation anomalies associated with the ID mode. For the IA mode the corresponding circulation anomalies are basically similar to a Pacific‐North America pattern. The subsidence associated with high‐pressure anomalies warms and dries the boundary layer, inhibiting cloud formation. The resulting surface radiative heating further warms the surface. For the low‐pressure anomalies the situation is just opposite. Through such processes these SSTAs can exert profound influences on the HWF variability over NA.

Surface temperature of the Black Sea increased due to climate change during the 20th century and continues to rise. Here we present by in situ data‐corrected remote‐sensed SST data covering a 34‐year period (1982–2015). Using a linear black box model, we predicted the Black Sea surface temperature (SST) up to 2100. During the 34‐year study period, we detected a 0.64 °C increase in SST per decade. The largest monthly fluctuations in SST were during late summer (August) and autumn (November). The rate of SST increase has almost caught up with the worst climate change scenario for the future. At the end of this century, the relative increase in average Black Sea SST is predicted to be 5.1 °C. In summary, our data show sea surface warming during recent decades, and we predict that this warming is likely to continue under the present environmental condition. The warming of the sea seems to also influence the amount of caught anchovies in the Black Sea. After 1993, the amount of captured anchovies in the southern Black Sea was drastically decreased with increased SST.

The paper discusses air (Ta) and sea surface temperature (SST) year-to-year variability due to warming of the Kara Sea, using the data from regular observations at the meteorological stations Roshydromet (GMS) in 1978–2017, NOAA optimum interpolation and reanalysis data. We use the methods of cluster, correlation analysis and Empirical Orthogonal Functions (EOF). We investigate possible cause and effect relationships of these changes with the variations of the wind field components, climatic indices and the sea ice concentration field. The cluster analysis of the three main EOF components has allowed us to identify four areas on the basis of the nature of changes of the water temperature anomalies field. The climatic changes in these areas, in the coastal and island zones of the Kara Sea have manifested themselves in the steady increase of the annual air temperature at GMS from 0,47–0,77 °C/10 years on the southwest coast to 1,33–1,49 °C/10 years in the north of the sea. This is equivalent to warming from 1,9 to 6,0 °C in the last 40 years. For the open sea the value of the Ta trend is about 1,22 °C/10 years, which corresponds to an increase in the average Ta by 4,9 °C in the last 40 years. This value is approximately 3 times greater than that for all the Northern hemisphere for the same period.Annualy, the maximal trend was observed in November and April mainly and exceeded 2–3 °C/10 years at some of the stations. We identify anomalously warm (2016 and 2012) and anomalously cold (1978, 1979, 1992 and 1998) years: the warmest year was 2012, the coldest — 1979. Positive SST trends were observed over all the sea area during the warm period of year (to 1 °C/10 years). SST increased to 2,4 °C, which is approximately 1,5 times greater than the corresponding SST values for the Northern hemisphere. The maximum SST trend (0,4 °C/10 years) was observed in the northwest and southwest parts of the sea. From June to August the trends of SST exceed the annual ones 1,5–2 times. Interannual SST and Ta variations are characterized by close correlation links. Until approximately 1998–2004 the warming was rather insignificant, and after that the growth rate of Ta and SST increased many fold. Apparently it indicates changes in the mode and the large-scale atmospheric circulation in the early 2000s. We also observed a trend of strengthening of the southern wind during the cold period of the year and the northern one — in the warm period (0,5–0,6 m/s in 40 years). It is shown that there is a close correlation between the Ta increase and the changes in the meridional component of the wind speed during the cold period of the year for all the sea areas. For the warm period it is statistically insignificant both for Ta and SST. For the cold season we observed a contribution of the large-scale mode of atmospheric circulation into the variability of V component of the wind speed. The conribution was expressed through the indeces NAO, SCAND, Pol/EUR, AZOR, ISL and the differences of ISLSIB. For the warm season this contribution is expressed through the NAO, SCAND and AO only. For the warm period we showed statistically significant correlation between the increase in SST, Ta and the processes parametrized by the AMO, EA/WR and AZOR indeces. For the cold period the indeces are AMO, Pol/Eur, SIB and ISL SIB. The interannual variations of the sea ice concentration field are characterized by close correlation with Ta changes both in the annual cycle and during the periods of ice cover formation and evolution (R = –0,7... –0,9). For these periods we showed statistically significant relationships between the first EOF mode fluctuations and two climatic indeces — AMO (R = 0,5) and Pol/Eur (R = 0,4). The relationships between the temporary variability of the sea ice concentration and the wind field characteristics are weaker and statistically significant only for the meridional component of the wind speed (R = –0,4).

[1] The effects of sea surface temperature (SST) and greenhouse gas (GHG) changes on the mean age-of-air and water vapor are investigated using a state-of-the-art general circulation model (GCM), and general characteristics of tracer transport between the stratosphere and troposphere are analyzed. Downward tracer transport in the northern midlatitude stratosphere is found to be faster than at southern midlatitudes. The global mean downward transport to the troposphere from stratosphere mainly occurs during northern winter and the downward cross-tropopause transport is weakest from August to October. The maximum troposphere mean (TM) age-of-air, derived from an age tracer released near the stratopause (around 1 hPa), can reach 13 years and is much larger than the maximum stratosphere mean (SM) age-of-air derived from an analogous age tracer released in the troposphere, with the SM age-of-air in the Northern Hemisphere being younger than in the Southern Hemisphere. Increased SSTs tend to accelerate upward transport through the stratosphere and slow downward transport in midlatitudes and the tropical stratosphere. In the context of effects of GHG increases and the associated SST increases on the stratosphere mean age-of-air, the GHG effects dominate, i.e., changes in the stratospheric mean age-of-air caused by SST increases only are smaller than those caused by combined changes in SSTs and GHGs. An increase in SSTs enhances the upward Eliasen-Palm (EP) flux in the extratropics. A 7.7% enhancement of tropical upwelling can be caused by a uniform 1.5 K SST increase. When both SST and GHG values are increased to the 2100 conditions, the meridional heat flux decreases in both winter hemispheres (and statistically significantly in the Southern Hemisphere). Meanwhile, the EP flux in the Northern Hemisphere increases significantly and the tropical upwelling is enhanced by 15% compared to the present-day conditions.