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Semi-arid regions worldwide face critical challenges related to prolonged droughts and limited water availability, which significantly impact ecosystem dynamics and plant productivity. This study investigates the energy balance and the phenomenon of hysteresis between actual evapotranspiration (ET) and environmental variables in areas of Dense Caatinga (DC) and Sparse Caatinga (SC) using micrometeorological data collected between 2013 and 2015. It was observed that sensible heat flux (H) was the main component of the energy balance, representing more than 50% of the available energy. In comparison, latent heat flux (LE) varied between 20% annually and 40% during the rainy season. The energy balance closure was satisfactory, with closure coefficients ranging from 65% to 88% depending on the season and vegetation type. In SC, with a more exposed surface, the conversion of net radiation (Rn) at the surface into H is increased. In both regions, during dry periods, LE decreases mirroring the scarcity of water availability. The hysteresis analysis revealed complex cycles of ET in relation to net radiation (Rn), air temperature (Temp), and vapor pressure deficit (VPD), with significant interannual variations. The correlation between ET and gross primary productivity (GPP) indicated counterclockwise hysteresis patterns in DC, suggesting that changes in GPP precede and influence ET, reflecting a rapid stomatal response to increased photosynthetic activity. In SC, the hysteresis cycles between ET and GPP were more variable, displaying both counterclockwise and clockwise loops, especially during 2015, strongly influenced by the El Niño event, indicating lower efficiency in the ET response to GPP due to water constraints. Canopy conductance (Gc) and the decoupling coefficient (Ω) also showed seasonal variations, reflecting the ecophysiological responses to environmental conditions. The correlation between these two variables suggests that Gc in SC was more influenced by external factors, like radiation and water availability. These results demonstrate that the dynamics of the Caatinga Biome are strongly tied to seasonal rainfall patterns, as the ecosystem's physiological and metabolic traits are primarily regulated by water availability. The variations observed across years and vegetation types underscore the importance of considering interannual variability and the distinctive characteristics of the ecosystem when analyzing climate relationships. [Display omitted] • Investigates energy flux partitioning in Dense and Sparse Caatinga biome from 2013 to 2015. • Identifies significant hysteresis loops between ET and environmental variables. • Energy balance closure ranged from 65% to 88%. • Clockwise and counterclockwise hysteresis loops were observed. • Hysteresis patterns provide insights into ecophysiological responses of Caatinga biome. [ABSTRACT FROM AUTHOR]

The long-range transport of desert dust over the area of the temperate climate zone is associated with the influx of hot air masses due to the location of the sources of this aerosol in the tropical climate zone. Between 24–26 February 2021, such an aerosol outbreak took place and reached Central Europe. The mean temperature of +11.7 °C was recorded during the event. A comparison of this value to the 20-year (2000–2020) average February temperature for Warsaw (−0.2 °C) indicates the uniqueness of the meteorological conditions. It was the first wintertime inflow of Saharan dust over Warsaw, the presence of which was confirmed by lidar and sun-photometer measurements. The properties of the desert dust layers were obtained; the mean values of the particle depolarization for the fully developed mineral dust layer were 13 ± 3% and 22 ± 4% for 355 and 532 nm, respectively. The aerosol optical thickness was high with average values >0.36 for all wavelengths smaller than 500 nm. The three-modal, aerosol size distribution was dominated by coarse-mode particles, with a visible contribution of accumulation-mode particles. It suggests the possible presence of other aerosol types. [ABSTRACT FROM AUTHOR]

Background: DUAL I China, one of the DUAL trials, assessed efficacy/safety of insulin degludec/liraglutide (IDegLira) in Chinese adults with type 2 diabetes (T2D) not controlled by oral antidiabetic drugs (OADs). Methods: This phase 3a, treat‐to‐target multicenter trial randomized participants (glycated hemoglobin [HbA1c] 53.0‐85.8 mmol/mol; previous metformin ± another OAD) 2:1:1 to IDegLira (n = 361), degludec (n = 179), or liraglutide (n = 180). Primary endpoint was change in HbA1c after 26 weeks. Secondary endpoints included: HbA1c < 53.0 mmol/mol attainment, weight change, treatment‐emergent hypoglycemia, end‐of‐treatment insulin dose, and safety. Results: At 26 weeks, HbA1c had decreased by a mean 18.12 mmoL/moL (IDegLira), 12.37 mmoL/moL (degludec) (estimated treatment difference [ETD] −6.50 mmoL/moL; 95% confidence interval [CI] −7.96, −5.04; P <.0001), and 11.33 mmoL/moL (liraglutide) (ETD −6.87 mmoL/moL; 95% CI −8.33, −5.41; P < 0.0001), indicating noninferiority for IDegLira vs degludec and superiority vs liraglutide. HbA1c < 53.0 mmoL/moL attainment was 77.0% (IDegLira), 46.4% (degludec), and 48.3% (liraglutide). Mean weight change with IDegLira (0.1 kg) was superior to degludec (1.2 kg) (ETD −1.08 kg; 96% CI −1.55, −0.62; P < 0.0001). Severe or confirmed hypoglycemic event rates were 0.24 (IDegLira) and 0.17 (degludec) episodes/participant‐year (estimated rate ratio 1.46; 95% CI 0.71, 3.02; P =.3008, not significant). At the end of treatment, the IDegLira insulin dose was lower (24.5 U/d) vs degludec (30.3 U/d) (ETD −5.49 U; 95% CI −7.77, −3.21; P < 0.0001). No unexpected safety issues occurred. Conclusions: IDegLira is efficacious and well tolerated in Chinese adults with T2D not controlled by OADs. [ABSTRACT FROM AUTHOR]

The Fluxpart partitioning model was employed to assess transpiration, photosynthesis and evaporation, respiration based exclusively through high-frequency eddy covariance (EC) data. The model was implemented across three sites with two vegetation cover conditions (dense and sparse) during the drought episode between 2012 and 2015 in the Caatinga biome in Northeast Brazil. Fluxpart, an open-source Python software, partitions data by analyzing the flux variance similarity (FVS) relationship and conducting correlation analyses of EC data. The main contribution to the evapotranspiration (ET) process was transpiration (T), representing about 64 and 67% of the amount ET in areas with dense and sparse vegetation cover, respectively. When the Caatinga biome is in a good state of conservation, it behaves as a carbon sink; the net ecosystem exchange average was −6 g C m−2 day−1 (gram of carbon per square meter daily) for dense vegetation and 3 g C m−2 day−1 for sparse vegetation. Through ET, vapor pressure deficit (VPD), and gross primary production (GPP) via Fluxpart, an assessment was made concerning the underlying water use efficiency (uWUE) to understand the nonlinear effects of VPD on the carbon-water coupling at the ecosystem scale. The overvalues of 60 g C hPa0.5 kg−1 H 2 O−1 (grams of carbon times square root of hectopascals per kilogram of water) prevailing in the rainy season and below 20 g C hPa0.5 kg−1 H 2 O−1 were mostly in the dry season. uWUE was an important indicator of the ability of the Caatinga biome to optimize water loss and carbon gain according to the water available in the soil-plant-atmosphere system to withstand water stress, especially at dense vegetation covers. • The fluxpart model was used to partition water and carbon dioxide fluxes in a Brazilian seasonally dry tropical forest. • Transpiration was the main component of evapotranspiration in areas of dense vegetation covers. • Caatinga biome behaved as a carbon sink when in a good conservation state. • Underlying water use efficiency (uWUE) was an indicator of the Caatinga's ability to optimize water loss and carbon gain. [ABSTRACT FROM AUTHOR]

The Amazon region stands out as Earth's largest and most prominent terrestrial convective center, significantly influencing precipitation patterns through the substantial net radiation at the Earth's surface (Rn). This radiation is further divided into sensible heat (H) and latent heat (LE) fluxes, underscoring the critical need to investigate the intricate exchanges of energy between ecosystems and the atmosphere while also scrutinizing the closure of the energy balance (EBC). Such studies are of paramount importance for gaining a comprehensive understanding of natural process dynamics. This research was undertaken to refine our comprehension of the temporal variability of energy fluxes, energy balance closure, and the phenomenon of evapotranspiration (ET) hysteresis in relation to key atmospheric variables, namely, Rn, air temperature, and vapor pressure deficit (VPD), within the central Amazon region. This investigation spanned a typical year (2014) and accounted for the influence of an El Niño Southern Oscillation (ENSO) event (2015). The findings illuminated that LE constituted the predominant component of the energy balance in both years, comprising approximately 70% of the total energy flux, except during the dry season of 2015 when H took precedence, accounting for 55% of the total energy exchange due to the ENSO event. The EBC exhibited an underestimation of turbulent fluxes (H + LE) of around 24% relative to the available energy (Rn - G). A more robust closure was observed during the dry period of 2015, reaching 82%, suggesting heightened uncertainty in LE estimates. In the context of ET, clockwise hysteresis loops were observed concerning air temperature and VPD. The relationship between ET and Rn displayed a linear response to solar radiation, with the intensity of ET hysteresis becoming more pronounced when correlated with air temperature and VPD. [Display omitted] • Analyze energy fluxes and evapotranspiration in Central Amazon. • Energy imbalance problems over a typical year (2014) and under ENSO event (2015). • The findings provide details into ET hysteresis cycles by meteorological variables. • A better energy closure was observed in the 2015 dry period (ENSO year). • The ET hysteresis showed clockwise loops in relation to meteorological variables. [ABSTRACT FROM AUTHOR]

This work presents a methodology for obtaining vertical profiles of aerosol single scattering properties based on a combination of different measurement techniques. The presented data were obtained under the iAREA (Impact of absorbing aerosols on radiative forcing in the European Arctic) campaigns conducted in Ny-Ålesund (Spitsbergen) during the spring seasons of 2015–2017. The retrieval uses in-situ observations of black carbon concentration and absorption coefficient measured by a micro-aethalometer AE-51 mounted onboard a tethered balloon, as well as remote sensing data obtained from sun photometer and lidar measurements. From a combination of the balloon-borne in-situ and the lidar data, we derived profiles of single scattering albedo (SSA) as well as absorption, extinction, and aerosol number concentration. Results have been obtained in an altitude range from about 400 m up to 1600 m a.s.l. and for cases with increased aerosol load during the Arctic haze seasons of 2015 and 2016. The main results consist of the observation of increasing values of equivalent black carbon (EBC) and absorption coefficient with altitude, and the opposite trend for aerosol concentration for particles larger than 0.3 μm. SSA was retrieved with the use of lidar Raman and Klett algorithms for both 532 and 880 nm wavelengths. In most profiles, SSA shows relatively high temporal and altitude variability. Vertical variability of SSA computed from both methods is consistent; however, some discrepancy is related to Raman retrieval uncertainty and absorption coefficient estimation from AE-51. Typically, very low EBC concentration in Ny-Ålesund leads to large error in the absorbing coefficient. However, SSA uncertainty for both Raman and Klett algorithms seems to be reasonable, e.g. SSA of 0.98 and 0.95 relate to an error of ±0.01 and ± 0.025, respectively. [ABSTRACT FROM AUTHOR]

The Atmospheric Boundary Layer (ABL) over two middle-latitude rural sites was characterized in terms of mean horizontal wind and turbulence sources using a standard classification methodology based on Doppler lidar. The first location was an irrigated olive orchard in Úbeda (Southern Spain), representing one of the most important crops in the Mediterranean basin and a typical site with Mediterranean climate. The second location was PolWET peatland site in Rzecin (Northwestern Poland), representing one of the largest natural terrestrial carbon storages that have a strong interaction with the climate system. The results showed typical situations for non cloud-topped ABL cases, where ABL is fully developed during daytime due to convection, with high turbulent activity and strong positive skewness indicating frequent and powerful updrafts. The cloud-topped cases showed the strong influence that clouds can have on ABL development, preventing it to reach the same maximum height and introducing top-down movements as an important contribution to mixing. The statistical analysis of turbulent sources allowed for finding a common diurnal cycle for convective mixing at both sites, but nocturnal wind shear driven turbulence with marked differences in its vertical distribution. This analysis demonstrates the Doppler lidar measurements and the classification algorithm strong potential to characterize the dynamics of ABL in its full extent and with high temporal resolution. Moreover, some recommendations for future improvement of the classification algorithm were provided on the basis of the experience gained. • Doppler lidar potential for a comprehensive analysis of boundary layer dynamics. • Turbulence classification algorithm able to follow quick changes in the dynamics. • Results suggest some improvements needed in the turbulence classification mask. [ABSTRACT FROM AUTHOR]

• Analysis of central european fen production under different aerosol properties. • Peatland production increases with aerosol optical depth rise during growing season. • AOD and single scattering albedo values effectively impact on global radiation. • Peatland production decreases with SSA drop during growing season. The productivity response of a peatland ecosystem in Rzecin, Poland, was determined based on varying aerosols abundant in the atmosphere. The study was done with the use of a multifactorial model that combined atmospheric and ecosystem modules to describe plant photosynthetic ability from different perspectives. The Gross Ecosystem Production (GEP) was calculated for real conditions in the period from May through September 2018. This period was characterized by increased air temperatures (1.4 °C) and reduced precipitation (17%), when compared to the long-term averages (1981–2010) for the studied area. This also aligned with expected direction of climate change predictions. The multifactorial model was used to show that, depending on the aerosol situation, the peatland ecosystem may react with an average increase (8.2%) as well as a decrease (6%) of GEP during the growing season. The modification of atmospheric optical properties with a step-wise increase of aerosol optical depth (AOD) by 0.2 in relation to the observed value, resulted in the increase of diffuse index (DI) of circa 22%, the decrease of photosynthetic photon flux density (PPFD) of circa 5%, and the increase of GEP of circa 8% in each of analyzed months. The GEP reduction (6%) was caused by the absorbing aerosol presence characterized by low single scattering albedo (SSA) value. Consequently, the CO 2 uptake process could not be maximized by the ecosystem due to reduced levels of available radiant energy. Conversely, the effect of non-absorbing aerosols presence on GEP was found negligible due to the continental clean aerosols prevailed in the air mass during the study period. Generally speaking, the estimation of the effects of aerosol optical properties on Rzecin peatland production shows that more absorbing aerosols occurrence cause GEP reduction while AOD rise results in GEP gain. [ABSTRACT FROM AUTHOR]

High quality lidar measurements of PollyXT operating at the University of Warsaw in the years 2013-2022 were analyzed to present a comprehensive optical characterization of biomass burning aerosols over Warsaw. The directions of the aerosol inflows were analyzed by dividing advection cases into four types, according to the area of origin: Western Europe, Eastern Europe, the Iberian Peninsula, and North America. It was shown that optical properties of smoke vary in each of these types, and emphasized that aerosol aging processes are important. It was found that as aerosol's age increases, there is more backscattering and less extinction at 355 nm in relation to 532 nm. The analysis of the lidar ratio demonstrated that the main changes of the aging process were observed in the UV spectra.

Urban areas, as major sources of aerosol black carbon emissions, contribute to increased pollution levels in surrounding regions by air mass long-range transport, which should be taken into account in implementation of emission-reduction strategies. Properties of light-absorbing aerosol particles and a novel approach to assess the impact of long-range transport on black carbon (BC) pollution in two under-investigated urban environments: Warsaw (Poland, Central Europe) and Vilnius (Lithuania, North-Eastern Europe) are presented. During the warm season of May-August 2022, BC mass concentration and aerosol optical properties: the scattering Ångström exponent (SAE), absorption Ångström exponent (AAE), and single scattering albedo (SSA) were investigated. Generally, the mean BC mass concentration was higher at the more polluted site in Warsaw (1.07 μg/m 3 ) than in Vilnius (0.77 μg/m 3 ). The BC source apportionment to biomass burning (BC BB ) and fossil fuel combustion (BC FF ) showed similar contributions for both sites with BC BB (13-19%) being significantly lower than BCFF (81-87%). A uniform flow of air masses transporting aerosol particles over long distances to both sites was observed for 42% of the days. It affected BC mass concentration as follows: BC decrease was found similar at both sites (42% in Warsaw, 50% in Vilnius) but increase was twice higher in Vilnius (64%) than in Warsaw (30%). Despite variations in BC mass concentration, both sites exhibited a comparable abundance (90%) of submicron (SAE<1.3), BC-dominated (AAE<1.5) particles. The mean SSA was very low (0.69 ± 0.1 in Warsaw, 0.72 ± 0.1 in Vilnius), which indicates a very strong contribution of light-absorbing aerosol particles in both environments. The local episodes of biomass burning due to celebrations of May Days on 1st - 3rd May in Warsaw and Midsummer on 24th June in Vilnius showed similar aerosol properties in both cities (1.5