High-latitude Summer Research Articles

High- and low-latitude forcings on regional hydroclimate variability in Northeast China during Marine Isotope Stage 2

The scarcity of well-dated, highly temporally resolved, paleoclimate records during the Marine Isotope Stage (MIS) 2 in Northeast (NE) China limits our understanding of the hydroclimate history in East Asian monsoon (EAM) region under different boundary conditions and the prediction of future hydroclimate changes. Meanwhile, it has not been comprehensively investigated how high- and low-latitude forcings, as crucial driving factors of global climate change, impact regional hydroclimate on various timescales during the MIS 2. This study applies phytolith-based principal component 1 scores, sum proportions of grain size-based end-members 2 and 3, and values of loss-on-ignition at 550 °C from the Dadong profile, to provide new evidence of hydroclimate changes during the MIS 2 in NE China. The results suggest that the regional humidity was low during the Last Glacial Maximum, and gradually increased during the subsequent Last Deglaciation. Additionally, the typical climate pattern of “warm-humid/cold-dry” in the EAM region was showed during a series of millennial oscillations. Combined with multiple records from NE China, it is observed that the orbital-scale hydroclimate changes during the MIS 2 were relatively consistent in different regions, and were mainly regulated by the ice sheet extents under the control of Northern Hemisphere high-latitude summer insolation. On the millennial scale, however, the hydroclimate changes suggested significant asynchrony or even anti-phase, indicating that the climate pattern may not always be similar to the typical EAM pattern. We propose that a series of sea-land-air interactions under the coupling of North Atlantic Deep Water activities in high latitudes and El Niño-Southern Oscillation in low latitudes, may be responsible for this complicated pattern. This study provides new insights into the climate evolution in NE china and its relationship with the high- and low-latitude forcings, which is beneficial for the explanation of mechanisms behind climate variability in this region.

Seasons, Shorelines, and Their Effects on the Tropical Circulation and Hydrological Cycle

Abstract This work is a direct continuation of McKinney et al., who attempted to create a planet with Earth-like temperatures and physical properties but with precipitation and circulation patterns that were Titan-like. McKinney et al. attempted to do so by changing only three basic planetary parameters: the ratio of dry land to ocean on the surface, the rotation period, and the volatility of the condensable. Each of these parameters is varied from an Earth-like value to a Titan-like one to analyze the climate transition between these two planetary archetypes. In this work, we expand on McKinney et al. by including a seasonal cycle and increasing the number of diagnostic criteria for determining Titan-like dynamics. The simulations use Earth-like obliquity and an Earth-like solar constant. We find that the presence of a dry land strip extending to at least 55°N/S is most effective at creating Titan-like climatic conditions on an otherwise Earth-like planet, such as high-latitude summer precipitation maxima and a low-humidity equator. In contrast, slow rotation and high atmospheric vapor abundance have minimal climatic impacts despite being characteristic features of Titan. Our experiments show that it is not difficult to produce distinctly Titan-like features in an Earth-like GCM with minimal changes to its fundamental parameters. This suggests that Earth-like planets could have a large range of global climate states throughout their history just through changes in topography. Similarly, Titan may have experienced more Earth-like climate states in periods where its tropics were wetter.

Role of atmospheric rivers in shaping long term Arctic moisture variability

Atmospheric rivers (ARs) reaching high-latitudes in summer contribute to the majority of climatological poleward water vapor transport into the Arctic. This transport has exhibited long term changes over the past decades, which cannot be entirely explained by anthropogenic forcing according to ensemble model responses. Here, through observational analyses and model experiments in which winds are adjusted to match observations, we demonstrate that low-frequency, large-scale circulation changes in the Arctic play a decisive role in regulating AR activity and thus inducing the recent upsurge of this activity in the region. It is estimated that the trend in summertime AR activity may contribute to 36% of the increasing trend of atmospheric summer moisture over the entire Arctic since 1979 and account for over half of the humidity trends in certain areas experiencing significant recent warming, such as western Greenland, northern Europe, and eastern Siberia. This indicates that AR activity, mostly driven by strong synoptic weather systems often regarded as stochastic, may serve as a vital mechanism in regulating long term moisture variability in the Arctic.

The Association Between Cloud Droplet Number over the Summer Southern Ocean and Air Mass History

AbstractThe cloud properties and governing processes in Southern Ocean marine boundary layer clouds have emerged as a central issue in understanding the Earth's climate sensitivity. While our understanding of Southern Ocean cloud feedbacks have evolved in the most recent climate model intercomparison, the background properties of simulated summertime clouds in the Southern Ocean are not consistent with measurements due to known biases in simulating cloud condensation nuclei concentrations. This paper presents several case studies collected during the Capricorn 2 and Marcus campaigns held aboard Australian research vessels in the Austral Summer of 2018. Combining the surface‐observed cases with MODIS data along forward and backward air mass trajectories, we demonstrate the evolution of cloud properties with time. These cases are consistent with multi‐year statistics showing that long trajectories of air masses over the Antarctic ice sheet are critical to creating high droplet number clouds in the high latitude summer Southern Ocean. We speculate that secondary aerosol production via the oxidation of biogenically derived aerosol precursor gasses over the high actinic flux region of the high latitude ice sheets is fundamental to maintaining relatively high droplet numbers in Southern Ocean clouds during Summer.

Atmospheric CO2 controls on the MIS 6 glaciation: 10Be chronology of moraines in the Haizishan area, southeastern Tibetan Plateau

A unifying theory interpreting the cause of ice-age cycles remains elusive, in view of the near-synchronous interhemispheric major climate shifts but anti-phased summer solar insolation signatures between hemispheres. Determining the timing and magnitude of mountain glaciations helps in shedding new light on this long-standing unsolved puzzle. Yet, robust glacial chronologies are limited for the pre-Last Glaciation time periods, impeding a full understanding of glacial histories and climatic mechanisms behind them in mountainous regions, such as the Tibetan Plateau (TP). Here, we report thirty-five new 10Be exposure-ages from moraine boulders in the Niqingqu Valley, eastern Haizishan Plateau, which adds to the existing glacial chronologies of the Hengduan Mountains, southeastern TP. The dating results indicate that four centennial to millennial-scale glacial activities occurred around 168.4 ka in the studied valley. Despite being indistinguishable in age, these high-frequency glacial fluctuations allow us to draw a conclusion that glaciers in the studied valley achieved the marine isotope stage 6 (MIS 6) glacial maximum prior to the Penultimate Glacial Maximum (PGM), inconsistent with Northern Hemisphere. We attribute the MIS 6 glacial maximum identified here to the response of glaciers to a combination of low-level atmospheric CO2 content and low northern high-latitude summer solar insolation/high summer-monsoon precipitation. The consistent local PGM and low CO2 levels suggest that low atmospheric CO2 contents are likely a necessary prerequisite for the MIS 6 glaciation.

Spatial-temporal variation of soil organic matter decomposition potential in China

Soil organic matter decomposition is an essential process of the ecosystem biogeochemical cycle. However, the comprehension of soil organic matter decomposition mechanisms at a large-scale level remains relatively inadequate, especially due to the high variability in organic matter quality, which poses challenges for standardized analysis of decomposition. Therefore, in this study, standardized cotton strips (to represent cellulose) and wooden sticks (to represent lignin) were used to conduct field research on the decomposition potential of soil organic matter, comparing the mass loss of these standardized materials across 23 sites situated in different climate types in China. After 6 months of incubation, the decomposition rate of both substrates displayed an increasing trend from north to south and a decreasing trend from east to west, driven by variations in temperature and precipitation at a large scale. However, the decomposition pattern of wooden sticks along the latitude exhibited a reversal during summer, with a positive correlation between mass loss per unit temperature and latitude, possibly attributable to reduced constraints on decomposer activity at high latitudes in summer. These results suggest that the decomposition ability of decomposers is more powerful at high latitudes compared with the decomposers at low latitudes. Random forest analysis showed that decomposers, soil conditions and climate had significant effects on the decomposition of standardized organic matter at the large-scale. Notably, as decomposition progressed, the relative influence of the decomposers on the cotton strips mass loss significantly increased, while for wooden sticks, the relative influence of climate significantly increased. In summary, this study provides crucial evidence for the spatial characteristics and temporal dynamics of soil organic matter decomposition in large-scale patterns.

Overlooked Long‐Term Atmospheric Chemical Feedbacks Alter the Impact of Solar Geoengineering: Implications for Tropospheric Oxidative Capacity

AbstractStudies of the impacts of solar geoengineering have mostly ignored tropospheric chemistry. By decreasing the sunlight reaching Earth's surface, geoengineering may help mitigate anthropogenic climate change, but changing sunlight also alters the rates of chemical reactions throughout the troposphere. Using the GEOS‐Chem atmospheric chemistry model, we show that stratospheric aerosol injection (SAI) with sulfate, a frequently studied solar geoengineering method, can perturb tropospheric composition over a span of 10 years, increasing tropospheric oxidative capacity by 9% and reducing methane lifetime. SAI decreases the overall flux of shortwave radiation into the troposphere, but increases flux at certain UV wavelengths due to stratospheric ozone depletion. These radiative changes, in turn, perturb tropospheric photochemistry, driving chemical feedbacks that can substantially influence the seasonal and spatial patterns of radiative forcing beyond what is caused by enhanced stratospheric aerosol concentrations alone. For example, chemical feedbacks decrease the radiative effectiveness of geoengineering in northern high latitude summer by 20%. Atmospheric chemical feedbacks also imply the potential for net global public health benefits associated with stratospheric ozone depletion, as the decreases in mortality resulting from SAI‐induced improvements in air quality outweigh the increases in mortality due to increased UV radiation exposure. Such chemical feedbacks also lead to improved plant growth. Our results show the importance of including fuller representations of atmospheric chemistry in studies of solar geoengineering and underscore the risk of surprises from this technology that could carry unexpected consequences for Earth's climate, the biosphere, and human health.

Deep-future climate change scenarios for site selection of nuclear waste disposal in Germany

Abstract. Glacial cycles are primarily attributed to Earth's evolving orbital parameters, which change the amount of insolation received by the high latitudes in summer. Another significant aspect is how much of this solar energy is retained. Recent research (Ganopolski et al., 2016) has shown a connection between the maximum summer insolation at 65∘ N and CO2 concentration needed for glacial inception. As available fossil fuel reserves have the capacity to impact the climate hundreds of thousands of years into the future (Archer and Ganopolski, 2005), there is a great deal of uncertainty regarding when (and how) glacial cycles will resume under different emission scenarios. Using the newly developed Earth system model of intermediate complexity, CLIMBER-X (Willeit et al., 2022), in conjunction to a reduced complexity model of glacial cycles (Talento and Ganopolski, 2021), the Potsdam Institute for Climate Impact Research (PIK) will provide a set of deep-future climate change scenarios for Germany for the next 100 000 years (more detailed scenarios) and for the next 1 million years. These experiments will be evaluated in collaboration with other project partners and seek to quantify the degree of uncertainty in Earth's climate for the site selection planning of a deep geological repository. The tuning of CLIMBER-X to current glacial conditions is displayed with regards to paleoclimatic data. Variables in the climate, such as temperature, precipitation, and sea level, are showcased for different emission scenarios. Conditions of the European ice sheet complex during future glacial cycles are presented. We argue that these results should be considered when discussing processes which effect the safety of a nuclear waste repository, including subterranean stress, permafrost, groundwater changes, chemical reactions, erosion, and subrosion. A detailed analysis and sensitivity study of the model simulations will be performed to assess the overall uncertainty associated with the climate response due to different cumulative anthropogenic CO2 emissions and model parameters.

Bidimensional climatology and trends of Northern Hemisphere blocking utilizing a new detection method

AbstractIn this article, the meridional gradient of daily potential vorticity (PV) on the 330 K isentropic surface is used to identify atmospheric blocking events for the period 1979–2019. The associated two‐dimensional index considers not only Rossby wave breaking, but also energy dispersion and nonlinearity of blocking systems, and thus has a solid theoretical foundation. It also has the advantage of automatically excluding subtropical high‐pressure systems in summer and autumn. The index reveals that the Northern Hemisphere exhibits high blocking frequency over Euro‐Atlantic, North Pacific and Greenland in winter, spring and autumn, and over two wide‐extended bands at high latitudes in summer. Two prominent blocking episode (BE) intensity centres are found over the eastern Atlantic and eastern Pacific in all seasons, while the long‐lived BE is primarily situated in regions with high BE frequency. There is more frequent and longer‐lived BE in the Euro‐Atlantic sector than in the North Pacific, whereas the BE in the North Pacific is more intense. Notably, with the same poleward criterion for the four seasons, the BE frequency and duration are supposed to be overestimated in summer. Comparing our blocking detection method with previous blocking indices provides additional information about the long‐term trends for blocking frequency and intensity, which can be useful to our understanding of future extremes on climate time‐scales. It is found that both blocking frequency and intensity exhibit upward linear trends in the Ural region and Barents–Kara Sea in winter, Europe, northern North Pacific and East Siberia in spring, western Greenland in summer, as well as Norwegian Sea, Europe and North Atlantic in autumn, which point to increases in high‐impact weather events in these regions.

Investigation on Thermal Comfort and Thermal Adaptive Behaviors of Rural Residents in Suibin Town, China, in Summer

With global warming, the climate is becoming hotter, even at higher latitudes. In order to clarify the thermal environment and thermal comfort level of rural residents at higher latitudes in summer, a field survey on thermal comfort was conducted in Suibin Town, China. The results show the following: (1) The correlation between the operative temperature and the mean thermal sensation score is stronger than that between the operative temperature and the thermal sensation score. Moreover, the applicability of the thermal comfort evaluation index of the operative temperature in severely cold areas was verified. The linear regression method showed that the neutral temperature is 25.1 °C and the thermal acceptable range is 22.5–27.6 °C. (2) There is a strong correlation between thermal sensation and thermal acceptability. (3) The preferred temperature in summer is 25.3 °C. Moreover, rural residents prefer cooler indoor temperatures in summer. (4) The clothing insulation of rural residents decreases with an increase in the indoor operative temperature. (5) Rural residents’ acceptance of the indoor temperature in summer is influenced by the economy, psychology, adaptive behaviors, etc. Moreover, rural residents expect cooler indoor temperatures in summer and will adapt to the thermal environment via low-cost adaptive behaviors.

Vertical characteristics and potential sources of aerosols over northeast China using ground-based MAX-DOAS

Information on the vertical distribution of air pollutants is essential to understand the potential mechanisms of haze pollution. Multiaxial differential optical absorption spectrometry (MAX-DOAS) is an effective method to detect the vertical distribution of air pollutants. In this study, we used MAX-DOAS to continuously analyze the vertical aerosol distribution throughout the year (from January 2019 to December 2019) in Shenyang. In winter, the aerosol extinction coefficient (AEC) was the highest (0.63 ± 0.09 km−1), followed by summer (0.53 ± 0.08 km−1), spring (0.51 ± 0.08 km−1), and autumn (0.47 ± 0.09 km−1). The aerosol extinction coefficients in various seasons were affected by the weather type. The hygroscopic growth of small particles lead to a surface AEC reaching 1.45 ± 0.23 km−1 in summer, resulting in heavy haze. The coal burning for heating and automobile exhaust in winter increased the possibility of winter haze, wherein the surface AEC can reach 1.27 ± 0.19 km−1. Signs of aerosol transport can be observed at high latitudes in summer, and when combined with backward trajectories, the transport of pollutants from Inner Mongolia to Liaoning Province is evident. The possible sources of air pollutants were investigated using a concentration weighted trajectory (CWT) model. In addition to the nearby Liaoning Province, both Beijing and Tianjin were also the main sources of pollution in Shenyang (0.04 km; Shandong Province was the main source of pollution at 0.44 km).

A note on a mother-foetus pair and alleged father match in the Atlantic fin whale (Balaenoptera physalus) off Iceland

The North Atlantic fin whale (Balaenoptera physalus) undertakes long-distance annual migration between high-latitude summer feeding locations and low-latitude winter mating locations, like most of the baleen whales. By statistically comparing genotype profiles of mother-foetus pairs (n = 23) to that of the potential alleged father (n = 139) captured at the same feeding location in Iceland, we found a matching pairing of a mother-foetus captured in 2009 and a father captured in 2010. To our knowledge, the present study is the first one to detect a mother-foetus pair matching with an alleged father, caught at exactly the same feeding area one year later.

Adaptation of Drosophila melanogaster to Long Photoperiods of High-Latitude Summers Is Facilitated by the ls-Timeless Allele.

Circadian clocks help animals to be active at the optimal time of the day whereby for most species the daily light-dark cycle is the most important zeitgeber for their circadian clock. In this respect, long arctic summer days are particularly challenging as light is present almost 24 h per day, and continuous light makes the circadian clocks of many animals arrhythmic. This is especially true for the fruit fly, Drosophila melanogaster, which possesses a very light-sensitive clock. The blue-light photoreceptor Cryptochrome (CRY) and the clock protein Timeless (TIM) are the light-sensitive components of the circadian clock and are responsible for constant light-induced arrhythmicity even at very low light intensities. Nevertheless, D. melanogaster was able to spread from its tropical origin and invade northern latitudes. Here, we tested whether a natural polymorphism at the timeless (tim) locus, s-tim and ls-tim, helped adaptation to very long photoperiods. The recently evolved natural allele, ls-tim, encodes a longer, less light sensitive form of TIM (L-TIM) in addition to the shorter (S-TIM) form, the only form encoded by the ancient s-tim allele. ls-tim has evolved in southeastern Italy and slowly spreads to higher latitudes. L-TIM is known to interact less efficiently with CRY as compared with S-TIM. Here, we studied the locomotor activity patterns of ~40 wild s-tim and ls-tim isofemale lines caught at different latitudes under simulated high-latitude summer light conditions (continuous light or long photoperiods with 20-h daily light). We found that the ls-tim lines were significantly more rhythmic under continuous light than the s-tim lines. Importantly, the ls-tim lines can delay their evening activity under long photoperiods, a behavioral adaptation that appears to be optimal under high-latitude conditions. Our observations suggest that the functional gain associated with ls-tim may drive the northern spread of this allele by directional selection.

Three‐Dimensional Analysis of Global Gravity Waves Based on COSMIC Multi‐Satellite Observations

AbstractGravity waves (GWs) transport momentum and energy in the atmosphere, and it has become a difficult problem how to use satellites data to extract the horizontal parameters of GWs. We firstly applied the multi‐channel maximum entropy method to the temperature profile triples based on the favorable conditions of satellite flight between year 2006 and 2007 after COSMIC launch, and analyzed the three‐dimensional properties of GWs. The latitudinal and seasonal distribution of horizontal wavelengths of gravity waves were obtained. The momentum fluxes showed the maximum in the summertime subtropics and the wintertime high latitudes, which revealed possible convective sources in the summertime subtropics and mountain waves expected to occur in the winter jet region in the winter hemisphere high latitudes. The fluxes also showed the maximum at summer high latitudes, which were seldom reported.

Near-constant retreat rate of a terrestrial margin of the Laurentide Ice Sheet during the last deglaciation

Abstract The Laurentide Ice Sheet (LIS) was the largest ice sheet during the last glacial period. An accurate representation of its behavior during the last deglaciation is critical to understanding its influence on and response to a changing climate. We use 10Be dating and Bayesian modeling to track the recession of the southwest sector of the Labrador Dome of the LIS along an ∼500-km-long transect west of Lake Superior during the last deglaciation. This transect reflects terrestrial ice-margin retreat and crosses multiple moraine sets, with the southwestern part of the transect deglaciated by ca. 19 ka and the northeastern part deglaciated by ca. 10 ka. The predominant behavior of the ice margin during this interval is near-constant retreat with retreat rates varying between ∼59 m/a and 38 m/a. The moraine sets mark standstills and/or readvances that in total constitute only ∼17% of the retreat interval. The spatial and temporal pattern of ice-margin retreat tracked here differs from existing reconstructions that are based on using isochrons to define ice-margin positions. Acknowledging the uncertainties associated with the modeled ages of ice-margin retreat, we suggest that the overall retreat pattern is consistent with forcing by a gradual increase in Northern Hemisphere, high-latitude summer insolation. The pattern of ice-margin retreat is inconsistent with Greenland ice-core temperature records, and thus these records may not be suitable to drive models of the LIS.

Late Quaternary glacial history of the Altyn Tagh Range, northern Tibetan Plateau

Quantifying the timing and extent of late Quaternary glaciations across the Tibetan Plateau (TP) is critical to understanding regional and global climate changes. Despite significant advancements in our knowledge of glacial histories of the TP over the past several decades, chronological constraints are still lacking for the high glaciated mountain ranges on the northern TP, including the Altyn Tagh Range. In this study, we provide thirty-two new 10Be exposure-ages to construct a late Quaternary glacial history of the Altyn Tagh Range at the Altyn “Pass” and Akato Tagh. The dating results from Altyn “Pass” indicate that glacier might have fully melted out of this area after Marine Isotope Stage 3 (MIS 3). The tentatively-defined minimum moraine ages north of Akato Tagh show that four glacial culminations possibly occurred during MIS 5, MIS 4, MIS 3 or 2, and the late Holocene. These dating results, together with the compiled exposure-ages from Sulamu Tagh, imply that the last glacial glacier fluctuations along the Altyn Tagh Range were likely driven by several factors: North Atlantic climate oscillations, northern hemispheric high-latitude summer solar insolation, atmospheric CO2 concentrations, and geometry of glacier catchment. The progressive reduction in glacier extent during the last glacial is likely associated with available precipitation, controlled by the mid-latitude westerlies.

The Diurnal Variation in Stratospheric Ozone from MACC Reanalysis, ERA-Interim, WACCM, and Earth Observation Data: Characteristics and Intercomparison

In this study, we compare the diurnal variation in stratospheric ozone of the MACC (Monitoring Atmospheric Composition and Climate) reanalysis, ECMWF Reanalysis Interim (ERA-Interim), and the free-running WACCM (Whole Atmosphere Community Climate Model). The diurnal variation of stratospheric ozone results from photochemical and dynamical processes depending on altitude, latitude, and season. MACC reanalysis and WACCM use similar chemistry modules and calculate a similar diurnal cycle in ozone when it is caused by a photochemical variation. The results of the two model systems are confirmed by observations of the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) experiment and three selected sites of the Network for Detection of Atmospheric Composition Change (NDACC) at Mauna Loa, Hawaii (tropics), Bern, Switzerland (midlatitudes), and Ny-Ålesund, Svalbard (high latitudes). On the other hand, the ozone product of ERA-Interim shows considerably less diurnal variation due to photochemical variations. The global maxima of diurnal variation occur at high latitudes in summer, e.g., near the Arctic NDACC site at Ny-Ålesund, Svalbard. The local OZORAM radiometer observes this effect in good agreement with MACC reanalysis and WACCM. The sensed diurnal variation at Ny-Ålesund is up to 8% (0.4 ppmv) due to photochemical variations in summer and negligible during the dynamically dominated winter. However, when dynamics play a major role for the diurnal ozone variation as in the lower stratosphere (100–20 hPa), the reanalysis models ERA-Interim and MACC which assimilate data from radiosondes and satellites outperform the free-running WACCM. Such a domain is the Antarctic polar winter where a surprising novel feature of diurnal variation is indicated by MACC reanalysis and ERA-Interim at the edge of the polar vortex. This effect accounts for up to 8% (0.4 ppmv) in both model systems. In summary, MACC reanalysis provides a global description of the diurnal variation of stratospheric ozone caused by dynamics and photochemical variations. This is of high interest for ozone trend analysis and other research which is based on merged satellite data or measurements at different local time.

Land–sea temperature contrasts at the Last Interglacial and their impact on the hydrological cycle

Abstract. Due to different orbital configurations, high northern latitude summer insolation was higher during the Last Interglacial period (LIG; 129–116 thousand years before present, ka) than during the pre-industrial period (PI), while high southern latitude summer insolation was lower. The climatic response to these changes is studied here with focus on the Southern Hemisphere monsoons, by performing an equilibrium experiment of the LIG at 127 ka with the Australian Earth System Model, ACCESS-ESM1.5, as part of the Paleoclimate Model Intercomparison Project 4 (PMIP4). Simulated mean surface air temperature between 40 and 60∘ N over land during boreal summer is 6.5 ∘C higher at the LIG compared to PI, which leads to a northward shift of the Intertropical Convergence Zone (ITCZ) and a strengthening of the North African and Indian monsoons. Despite 0.4 ∘C cooler conditions in austral summer in the Southern Hemisphere (0–90∘ S), annual mean air temperatures are 1.2 ∘C higher at southern mid-latitudes to high latitudes (40–80∘ S). These differences in temperature are coincident with a large-scale reorganisation of the atmospheric circulation. The ITCZ shifts southward in the Atlantic and Indian sectors during the LIG austral summer compared to PI, leading to increased precipitation over the southern tropical oceans. However, weaker Southern Hemisphere insolation during LIG austral summer induces a significant cooling over land, which in turn weakens the land–sea temperature contrast, leading to an overall reduction (−20 %) in monsoonal precipitation over the Southern Hemisphere's continental regions compared to PI. The intensity and areal extent of the Australian, South American and South African monsoons are consistently reduced in LIG. This is associated with greater pressure and subsidence over land due to a strengthening of the Southern Hemisphere Hadley cell during austral summer.

The Role of Inertial Instability in Cross-Hemispheric Coupling

AbstractRecent studies suggest linkages between anomalously warm temperatures in the winter stratosphere, and the high-latitude summer mesopause. The summer temperature anomaly is manifested in the decline of polar mesospheric clouds. The 2-day wave is a strong-amplitude and transient summer feature that interacts with the background state so as to warm the high-latitude summer mesopause. This wave has been linked to a low-latitude phenomenon called inertial instability, which is organized by breaking planetary waves in the winter stratosphere. Hence, inertial instability has been identified as a possible nexus between the disturbed winter stratosphere, and summer mesopause warming. We investigate a sustained occurrence of inertial instability during 19 July–8 August 2014. During this period, stratospheric winter temperatures warmed by about 10 K, while a steep decline in polar mesospheric clouds was reported between 26 July and 6 August. We present, for the first time, wave driving associated with observed inertial instability. The effect of inertial instability is to export eastward momentum from the winter hemisphere across the equator into the summer hemisphere. Using a primitive equation model, we demonstrate that the wave stresses destabilize the stratopause summer easterly jet. The reconfigured wind profile excites the wavenumber-4 component of the 2-day wave, leading to enhanced warming of the summer mesopause. This work supports previous numerical investigations that identified planetary wave–driven inertial instability as a source of the 2-day wave.

Terahertz band channel properties according to transmit power estimation

Over the last decade, short-range communications in the THz (Terahertz) band have been extensively studied as a technology-enabler for dense and ultra-dense wireless networks. The increasing demand for high data rates for wireless communication systems will inevitably lead to the extension of operation frequencies with larger bandwidths. THz range enables bandwidths on the order or hundreds of GHz. Thus, THz Band communication will alleviate the capacity limitations and spectrum scarcity of current wireless systems, and enable new classical networks and novel nanoscale networks applications. The main aim of this paper is to provide design guidelines for close proximity links with transmission capacity beyond 100 Gbit/s. We present the path loss, absorption loss, signal to noise ratio (SNR) and capacity of propagating electromagnetic waves at THz Band in different air medium types. The channel capacity and SNR properties are calculated according to transmit power estimation. In this paper, five air medium types are investigated which are average latitude—summer, high latitude—summer, average latitude—winter, high latitude—winter and tropics.