Multi-annual Mean Research Articles

Intercomparison of gross primary productivity in spatio-temporal distribution over a typical tropical region based on different datasets.

Gross Primary Productivity (GPP) plays a vital role in the carbon cycle of terrestrial ecosystems. For the purpose of assessing the performance of various GPP products in a typical tropical area, this study conducted an intercomparison of seven different GPP products over Hainan Island, China, and analyzed spatiotemporal characteristics of GPP in different elevation regions and vegetation types over study area. The results showed that although the GPP spatial distribution pattern over Hainan Island, as presented by different GPP products, is similar- showing that GPP values in the southwest are higher than those in the northeast- there are significant differences in the spatial distributions and magnitudes of each GPP product. The multi-annual mean GPP values from the seven GPP products exhibited similar temporal variation trends, with GOSIF being obviously higher than other GPP products. The GPP products indicated significant differences in different elevation and vegetation type groups. The GPP gap between GLASS AVHRR and BESS V2 decreases slightly with the increase in elevation. Most GPP products show a consistent change trend over time. There were also significant differences in the results of significance tests for the change trends of GPP products. Though GOSIF is significantly higher than other GPP products, it demonstrated a relatively high correlation with all GPP products, while AGPP exhibited relatively low correlations with all GPP products. The quantitatively comparative analysis of seven different GPP products in this study is valuable for improving GPP retrieval models and can also serve as a scientific reference for the application of GPP products in tropical region vegetation studies.

Quantifying the water use efficiency of karst ecosystems and response to environmental factors

Study regionThe study area is located in Guizhou province, the centre of the karst region in southwest China. Study focusAs a typical karst region, Guizhou has long faced challenges with water scarcity. Quantifying water use efficiency (WUE) is crucial for the efficient use of water resources and sustainable management. This study examined the spatio-temporal evolution patterns and its driving factors on WUE in Guizhou using Theil-Sen's slope, partial correlation methods, and the geographic detector model. New hydrological insights for the region(1) The multi-annual mean WUE of non-karst region (NKR, 2.75 gC kg−1 H2O yr−1) is higher than that of karst region (KR, 2.10 gC kg−1 H2O yr−1) during 2001–2020. (2) The rate of increase of WUE was three times higher in KR than in NKR. (3) Precipitation and temperature were identified as the key factors influencing WUE. Interactions between each environmental factors were observed to have both bi-variate and non-linear enhancement effects. Notably, in the NKR, soil moisture, vegetation type and leaf area index were the dominant factors influencing WUE, with interactions between environmental factors had both enhanced and weakened effect on WUE. (4) The synergistic effects of these interactions exceeded the individual or cumulative effects of the two environmental factors. These findings contribute to our understanding of the environmental factors driving changes in WUE in the KR.

Evolutionary characteristics of carbon sources/sinks in Chinese terrestrial ecosystems regarding to temporal effects and geographical partitioning

Whereas the current complex diversity in Chinese terrestrial ecosystems and the significant differences in net ecosystem productivity (NEP) among various regions, as well as the temporal effect between vegetation and climate factors, the NEP in Chinese terrestrial ecosystems was estimated between 2001 and 2020, and characterized the spatiotemporal dynamics of NEP and its driving mechanisms, taking into account geographic subdivisions. The results demonstrated that the multiannual mean of NEP in Chinese terrestrial ecosystems ranged from 42.79 to 61.91 g C/m2a over the past two decades, indicating a volatile upward trend. Spatially, the NEP of Chinese terrestrial ecosystems indicated significant spatial differentiation, with carbon sinks encompassing 68.83 %, primarily focused in Northeast Region (DB), East China (HD), South China (HN), and Central China (HZ). Moving forward, Chinese terrestrial ecosystems will be predominantly restored, with 40.88 % of the area going from degradation to improvement, and 14.17 % of the area undergoing sustained improvement. There were geographic differences in the temporal effects between NEP and climate elements (precipitation and temperature). Precipitation was identified as the dominant factor affecting the variation of NEP in DB, HB, HZ, XB, and XN. While solar radiation was the major factor influencing the variation of NEP in HD (51.72 %) and HN (76.07 %). Compared with human activities, climate change emerged as the primary driver impacting the spatiotemporal evolution of NEP in Chinese terrestrial ecosystems, with 61.40 % of the area of NEP increasing due to climate change, while 58.42 % increased due to human activities. Additionally, changes in land use/land cover played a crucial role in altering NEP of terrestrial ecosystems in China.

Exploring the contribution of environmental factors to evapotranspiration dynamics in the Three-River-Source region, China

Evapotranspiration (ET) exerts substantial effects on terrestrial ecosystem carbon and water cycles. A deep understanding of the spatial and temporal variability in ET and its dominant controls has crucial implications for future ecological management, especially for the ecologically-fragile Three-River-Source region (TRSR) in China. The study examined the performance of three ET products including Global Land Evaporation Amsterdam Model (GLEAM), Famine Early Warning Systems Network Land Data Assimilation System (FLDAS) and Global Land Surface Satellite (GLASS) based on eddy covariance-based flux observations. On this basis, ET dynamics in the TRSR from 1982 to 2018 were analyzed at two time scales using the GLASS ET product. Spatially, the pattern in ET showed a gradual upward trend from northwest to southeast. Meanwhile, ET in the majority of regions significantly enhanced, with multiannual mean ET and summer ET (June to August) increasing by 0.609 mm/yr and 0.765 mm/yr, respectively. Especially, ET in summer dominated the interannual dynamics of ET in the TRSR. The individual contributions of five environmental factors including Leaf Area Index (LAI), solar radiation (Rs), air temperature (Ta), precipitation (PRE) and vapour pressure deficit (VPD), to the variability in ET were isolated using ridge regression. Significant differences appeared when explaining ET over different time scales. Rs (33.05 %) and LAI (25.29 %) were the dominant control variables in shaping the interannual ET, with VPD contributing the least by 7.19 %. However, the long-term dynamics in summer ET were mainly controlled by LAI (35.73 %) and PRE (31.19 %), and Ta exerted the least effect by 5.73 %. All analyses will strengthen our understanding of the relationships between climate, vegetation and ET in the TRSR area, China.

Significant discrepancies of land surface daily net radiation among ten remotely sensed and reanalysis products

ABSTRACT Land surface all-wave net radiation (Rn) is crucial in determining Earth's climate by contributing to the surface radiation budget. This study evaluated seven satellite and three reanalysis long-term land surface Rn products under different spatial scales, spatial and temporal variations, and different conditions. The results showed that during 2000-2018, Global Land Surface Satellite Product (GLASS)-Moderate Resolution Imaging Spectroradiometer (MODIS) performed the best (RMSE=25.54 Wm-2, bias=−1.26 Wm-2), followed by ERA5 (the fifth-generation of European Centre for Medium-Range Weather Forecast Reanalysis) (RMSE=32.17 Wm-2, bias=−4.88 Wm-2) and GLASS-AVHRR (Advanced Very-High-Resolution Radiometer) (RMSE=33.10 Wm-2, bias=4.03 Wm-2). During 1983-2018, GLASS-AVHRR and ERA5 ranked top and performed similarly, with RMSE values of 31.70 and 33.08 Wm-2 and biases of −4.56 and 3.48 Wm-2, respectively. The averaged multi-annual mean Rn over the global land surface of satellite products was higher than that of reanalysis products by about 10∼30 Wm-2. These products differed remarkably in long-term trends variations, particularly pre-2000, but no significant trends were observed. Discrepancies were more frequent in satellite data, while reanalysis products showed smoother variations. Large discrepancies were found in regions with high latitudes, reflectance, and elevation which could be attributed to input radiative components, meteorological variables (e.g., cloud properties, aerosol optical thickness), and applicability of the algorithms used. While further research is needed for detailed insights.

A long record of European windstorm losses and its comparison to standard climate indices

Abstract. Traditional insurance has both a great exposure to decadal variations in European storm activity and the ability to adjust its business strategy over these timescales. Hence, the recent development of skilful predictions of multiannual mean European winter climate seems a very welcome addition to the long list of ways that researchers have improved management of windstorm risk. Yet companies do not use these forecasts of mean winter climate to adjust their view of risk. The main reason is the lack of a long, reliable record of losses to understand how forecasted time-mean circulation anomalies relate to the damage from a few, intense storms. This study fills that gap with a European windstorm loss record from 1950 to 2022, based on ERA5 peak near-surface winds per event which were converted to losses using an established damage function. The resulting dataset successfully identifies major storms over the past 70 years and simulates the multidecadal variations from low values in the 1960s up to high levels in the 1980s and 1990s then down to the 2010s. However, it underestimated the steepness of the observed loss decline from the stormy end of the 20th century to the lull over the past 20 years. This was caused by a quite flat trend in ERA5 extreme winds over the period, in contrast to the significant decline in observed peak gusts. Imposing these gust trends on ERA5 peak winds reconciled modelled losses with industry experience over the past few decades. Indices of European winter climate used in long-range forecasting were compared to the new modelled loss dataset. They had correlations of around 0.4 at interannual timescales, rising to about 0.7 for decadal and longer variations. Notably, the climate indices have a similar multidecadal trend as ERA5 extreme winds in modern times, including a less steep decline than found in observed gusts and losses. Further investigation of the modern-day divergence between climate indices and losses may help connect decadal forecasting to insurance.

ЙМОВІРНІСНІ ХАРАКТЕРИСТИКИ І СТАТИСТИЧНІ ПАРАМЕТРИ СТРОКІВ НАСТАННЯ ОСНОВНИХ ФАЗ ЛЬОДОВОГО РЕЖИМУ РІЧОК БАСЕЙНУ ПРИП’ЯТІ У МЕЖАХ УКРАЇНИ

Probabilistic characteristics of the water body ice regimes significantly expands knowledge about their variability, magnitudes and appearance timing of main phases. Such knowledge is important for the design and operation of hydraulic structures. Along with this, the probabilistic characteristics of the river ice regimes of Ukraine were calculated in the 70s of the 20th century, including for some rivers of the Pripyat basin. Therefore, the main objective of this research is to determine the probabilistic characteristics and statistical parameters of the appearance dates of main phases of river ice regimes, namely appearance date of ice, date of freeze-up, break-up date (i.e., melt onset), date of ice disappearance in the Prypiat River basin within Ukraine, as well as the analysis of the obtained results. The research was carried out based on the data of 29 water gauges for the period from the beginning of observations to 2020. Such indicators as the multi-annual mean, standard deviation and asymmetry coefficient were used as statistical parameters. The analytical distribution of the appearance dates of main phases of river ice regimes is determined by the Pearson curve of type III, and empirical distribution is determined by the Weibull formula. Statistical series of the appearance dates of main phases of river ice regimes were arranged from early to late dates, namely low probability values were assigned to early dates, and large probability values were assigned to later dates. Pearson probability distribution of type III quite successfully describes the empirical points of main phases of river ice regimes of the Pripyat basin within of Ukraine. Analytical distribution curves have a slight negative asymmetry for the dates of the ice appearance and freeze-up, and a positive asymmetry for the dates of the break-up and ice disappearance. The variability of standard deviation and multi-annual mean of the appearance dates of main phases of river ice regimes is within ±7.5-10 days and 3-4 weeks, respectively. In general, the appearance dates of main phases of river ice regimes, as well as their statistical parameters and probabilistic characteristics have close values that are subject to geographic zoning. The analysis of changes over time in probabilistic characteristics and statistical parameters of the dates of ice appearance and freeze-up showed that the greatest changes have by probabilities that are not repeated often, and the smallest – by multi-annual mean and asymmetry coefficients.

Plant richness, land use and temperature differently shape invertebrate leaf-chewing herbivory on plant functional groups

Higher temperatures can increase metabolic rates and carbon demands of invertebrate herbivores, which may shift leaf-chewing herbivory among plant functional groups differing in C:N (carbon:nitrogen) ratios. Biotic factors influencing herbivore species richness may modulate these temperature effects. Yet, systematic studies comparing leaf-chewing herbivory among plant functional groups in different habitats and landscapes along temperature gradients are lacking. This study was conducted on 80 plots covering large gradients of temperature, plant richness and land use in Bavaria, Germany. We investigated proportional leaf area loss by chewing invertebrates (‘herbivory’) in three plant functional groups on open herbaceous vegetation. As potential drivers, we considered local mean temperature (range 8.4–18.8 °C), multi-annual mean temperature (range 6.5–10.0 °C), local plant richness (species and family level, ranges 10–51 species, 5–25 families), adjacent habitat type (forest, grassland, arable field, settlement), proportion of grassland and landscape diversity (0.2–3 km scale). We observed differential responses of leaf-chewing herbivory among plant functional groups in response to plant richness (family level only) and habitat type, but not to grassland proportion, landscape diversity and temperature—except for multi-annual mean temperature influencing herbivory on grassland plots. Three-way interactions of plant functional group, temperature and predictors of plant richness or land use did not substantially impact herbivory. We conclude that abiotic and biotic factors can assert different effects on leaf-chewing herbivory among plant functional groups. At present, effects of plant richness and habitat type outweigh effects of temperature and landscape-scale land use on herbivory among legumes, forbs and grasses.

Landscape diversity and local temperature, but not climate, affect arthropod predation among habitat types.

Arthropod predators are important for ecosystem functioning by providing top-down regulation of insect herbivores. As predator communities and activity are influenced by biotic and abiotic factors on different spatial scales, the strength of top-down regulation ('arthropod predation') is also likely to vary. Understanding the combined effects of potential drivers on arthropod predation is urgently needed with regard to anthropogenic climate and land-use change. In a large-scale study, we recorded arthropod predation rates using artificial caterpillars on 113 plots of open herbaceous vegetation embedded in contrasting habitat types (forest, grassland, arable field, settlement) along climate and land-use gradients in Bavaria, Germany. As potential drivers we included habitat characteristics (habitat type, plant species richness, local mean temperature and mean relative humidity during artificial caterpillar exposure), landscape diversity (0.5-3.0-km, six scales), climate (multi-annual mean temperature, 'MAT') and interactive effects of habitat type with other drivers. We observed no substantial differences in arthropod predation rates between the studied habitat types, related to plant species richness and across the Bavarian-wide climatic gradient, but predation was limited when local mean temperatures were low and tended to decrease towards higher relative humidity. Arthropod predation rates increased towards more diverse landscapes at a 2-km scale. Interactive effects of habitat type with local weather conditions, plant species richness, landscape diversity and MAT were not observed. We conclude that landscape diversity favours high arthropod predation rates in open herbaceous vegetation independent of the dominant habitat in the vicinity. This finding may be harnessed to improve top-down control of herbivores, e.g. agricultural pests, but further research is needed for more specific recommendations on landscape management. The absence of MAT effects suggests that high predation rates may occur independent of moderate increases of MAT in the near future.

Mesoscale, Tidal, and Seasonal/Interannual Drivers of the Weddell Sea Overturning Circulation

Abstract The Weddell Sea supplies 40%–50% of the Antarctic Bottom Water that fills the global ocean abyss, and therefore exerts significant influence over global circulation and climate. Previous studies have identified a range of different processes that may contribute to dense shelf water (DSW) formation and export on the southern Weddell Sea continental shelf. However, the relative importance of these processes has not been quantified, which hampers prioritization of observational deployments and development of model parameterizations in this region. In this study a high-resolution (1/12°) regional model of the southern Weddell Sea is used to quantify the overturning circulation and decompose it into contributions due to multiannual mean flows, seasonal/interannual variability, tides, and other submonthly variability. It is shown that tides primarily influence the overturning by changing the melt rate of the Filchner–Ronne Ice Shelf (FRIS). The resulting ∼0.2 Sv (1 Sv ≡ 106 m3 s−1) decrease in DSW transport is comparable to the magnitude of the overturning in the FRIS cavity, but small compared to DSW export across the continental shelf break. Seasonal/interannual fluctuations exert a modest influence on the overturning circulation due to the relatively short (8-yr) analysis period. Analysis of the transient energy budget indicates that the nontidal, submonthly variability is primarily baroclinically generated eddies associated with dense overflows. These eddies play a comparable role to the mean flow in exporting dense shelf waters across the continental shelf break, and account for 100% of the transfer of heat onto the continental shelf. The eddy component of the overturning is sensitive to model resolution, decreasing by a factor of ∼2 as the horizontal grid spacing is refined from 1/3° to 1/12°.

The geostatistical analysis of the atmospheric precipitation in Europe on a West-East line transect

The general warming trend of the planet cannot be denied (the average global air temperature has increased by approx. 0.85°C between 1880-2012 (IPCC, 2013). The direct consequence of this warming is an increase in extreme weather events and hence in climate risks. The monitoring and assessing precipitation, identifying the physical laws governing its course in order to be able to estimate and forecast it in the future is therefore of great interest nowadays. Using geostatistical spatial analysis methods, this paper aims at identifying the correlations between longitude and precipitation (due to the specificity of the European climate, given by the major influence of the western circulation) and then an estimation - using linear regression equations - of precipitation amounts depending on longitude. Two variables were calculated for the statistical analysis: the proportion of the mean number of days with precipitation ≥ 10 mm of the multiannual mean of precipitation days (≥0,1 mm) and the precipitation ratio between the mean precipitation quantities in summer, compared to those in winter (hereinafter referred to as summer/winter precipitation ratio). The geostatistical analysis carried out on a sample of 40 weather stations aligned from west-south-west to east-north-east argues the existence of a strong correlation between longitude and the multiannual mean of days with precipitation ≥10 mm and between longitude and the summer/winter precipitation ratio.

The middle atmospheric meridional circulation for 2002–2012 derived from MIPAS observations

Abstract. Measurements of long-lived trace gases (SF6, CFC-11, CFC-12, HCFC-22, CCl4, N2O, CH4, H2O, and CO) performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) have been used to infer the stratospheric and mesospheric meridional circulation. The MIPAS data set covers the time period from July 2002 to April 2012. The method used for this purpose was the direct inversion of the two-dimensional continuity equation for the concentrations of trace gases and air density. This inversion predicts an “effective velocity” that gives the best fit for the evolution of the concentrations on the assumption that an explicit treatment of Fickian diffusion can be neglected. These effective velocity fields are used to characterize the mean meridional circulation. Multiannual monthly mean effective velocity fields are presented, along with their variabilities. According to this measure, the stratospheric circulation is found to be highly variable over the year, with a quite robust annual cycle. The new method allows us to track the evolution of various circulation patterns over the year in more detail than before. According to the effective velocity characterization of the circulation, the deep branch of the Brewer–Dobson circulation and the mesospheric overturning pole-to-pole circulation are not separate but intertwined phenomena. The latitude of stratospheric uplift in the middle and upper stratosphere is found to be quite variable and is not always found at equatorial latitudes. The usual schematic of stratospheric circulation with the deep and the shallow branch of the Brewer–Dobson circulation and the mesospheric overturning circulation is an idealization which best describes the observed atmosphere around equinox. Sudden stratospheric warmings and the quasi-biennial oscillation cause a pronounced year-to-year variability of the meridional circulation.

Human health impact assessment and temporal distribution of trace elements in Cop\u0219a Mic\u0103- Romania

The present study aims to analyze the temporal variations of PM10 and to assess the health risk indexes caused by trace elements from particulate matter (PM10) via inhalation, ingestion, and dermal absorption by adults and children in Copșa Mică (Romania) during 2009–2019. The results revealed a high multi-annual mean concentration of PM10 and trace elements. The analyzed air pollutants showed a decreasing trend during the studied years, therefore 44.11%, 43.48%, 36.07%, 16.02%, and 15.80% lower values were observed for As, Cd, Ni, PM10, and Pb, respectively, due to environmental regulations. The daily exceedance percentage of Pb and Cd was very high, representing 21.74% and 11.26%, followed by PM10 and As concentrations with 4.72% and 3.92%. The ratio between the trace element concentration measured in Copșa Mică and the country average was 2.46, 4.01, 2.44 and 10.52 times higher for As, Cd, Ni and Pb. The calculated Hazard Quotient values via inhalation were higher than the safe limit (1), which accounted 1.81, 3.89 and 4.52, for As, Cd and Ni, respectively, indicating that the trace elements might present a non-carcinogenic risk to both adults and children. Furthermore, the concentration of all studied trace elements in Copșa Mică showed cancer risk for adults via inhalation and dermal absorption as well.

Spatial distribution of trace elements (As, Cd, Ni, Pb) from PM10 aerosols and human health impact assessment in an Eastern European country, Romania

In the present study, the concentrations of trace elements in PM10 were determined and analyzed at 115 monitoring stations in Romania throughout the period 2009–2018. The spatiotemporal distribution of trace element concentrations of PM10, the source apportionment and health impact assessment, was carried out. The results showed a very high multi-annual mean concentration for PM10 and trace elements as well. The multiannual average concentration of PM10 was higher by 29.75% than the World Health Organization recommendation. All studied air pollutants showed a decreasing trend during the studied years, showing with 17.84%, 50.21%, 43.36%, 11.27%, and 72.09% lower values for PM10, As-, Cd-, Ni-, and Pb-, respectively, due to environmental regulations. To assess the human health impact, the hazard quotient (HQ) and cancer risk (CR) were calculated using the health risk model developed by the US Environmental Protection Agency (EPA). The Cd and Ni might present a non-carcinogenic risk to both adults and children; however, the hazard quotient values are higher than the safe limit, with 9.53 and 1.93, respectively. In addition, our study results revealed that the inhalation of As, Cd and the dermal absorption of all studied trace elements were considered as the most important risk factors for developing cancer, especially in case of adults.

Danube. Hydrographycal, hydrologycal and qualitative characteristics water with references on the Pontic Sector

The Danube is the second largest water course in Europe (after the Volga) in terms of length (2860 km) and area (817,000 km2) The river springs from the central-western part of Europe (Schwarzwald), runs through the central part of the continent, crosses the Pannonian Depression to the confluence with the Drava, then pierces the Carpathian Mountains through the Iron Gate Gorge. Farther down it separates the southern part of the Romanian Plain from the Prebalkan Plateau, and the eastern part of Sea, encompasses the Delta area. In Romania the Danube is 1075 km long and drains 97% of the country’s territory. It flows through European regions affected by Oceanic, Baltic, Mediterranean and temperate-continental climatic influences that stamp their mark on the morpho-hydrographic and hydrologic characteristics of the river. The Danube discharge regime depends on its upper course tributaries which come from the Alps with high waters in June. In its middle and lower course it depends on the Drava and the Sava, with high waters in spring (April –May) and lower ones in autumn (September – October). The Danube’s multiannual mean discharge increases downstream as follows: 1,470 m²/s at Passau, after confluencing with the Inn River; 1,920 m²/s in Vienna; 2,350 m²/s in Budapest and 5,300 m²/s after its junction with the Drava, Tisa and Sava rivers. This water volume enters Romania at Baziaş with 5560 m²/s. Hence forward values continue to rise through the contribution of its lower course tributaries, reaching 6,495 m²/s (over the 1840-2016 period) when flowing into the Delta-Ceatal Chilia. Maximum discharge is recorded during the high spring waters, but occasionally in summer, too: 15,800 m³/sec at Baziaș in April 2006; 15,300 m²/s at Giurgiu, and 15,900 m²/s at Ceatal Chilia. Minimum discharge occur in autumn and occasionally in winter: 1,040 m²/s at Baziaș 1949; and 1,790 m²/s at Ceatal Chilia in 1947.The alluvial discharge (1840-2000) was 53 million tons/ year, respectively 1,681kg/s, of which 2.81 million tons /year represented coarse alluvia (sands). The extreme values during that interval were 4,470 kg/sec (141 million tons/year) in 1871 and only 229 kg/sec (7.2 million tons/year) in 1990. Throughout that period there was a tendency to decrease at an annual rate of 8.3 kg/year, naturally with fluctuations in terms of the liquid discharge. The mineralisation degree is still moderate despite the higher quantities of polluting wastes being spilled into the river in front of large cities – Vienna, Bratislava, Budapest and Belgrade (values coming close to 350 – 400 mg/l due mainly to chlorine and natrium). The Danube’s great self-purification capacity makes it recover in the lower course. The qualitative characteristics of the water was implemented in 1996 by Danube Transnational Monitoring Network - TNMN, the objectives and programs in view of ensuring the concentrations and loads of relevant pollutans and identifyng of the major sources of pollution. The spatial and temporal variation in the pontic sector of the physico-chemical quality indicators, reflect the general characteristics and the effect / impact of the main pressures identified at basin level for the period 1996-2015, in 6 monitoring sections (from Baziaș to Reni). The type of surface water body (river, lake, transient water, coastal water) is an aquatic unit that has an aquatic flora and fauna determined by the climatic, lithological and morphological conditons of the minor riverbed, hydrological and physical. significant anthropogenic unmodified chemicals.

Variability in the global energy budget and transports 1985\u20132017

The study of energy flows in the Earth system is essential for understanding current climate change. To understand how energy is accumulating and being distributed within the climate system, an updated reconstruction of energy fluxes at the top of atmosphere, surface and within the atmosphere derived from observations is presented. New satellite and ocean data are combined with an improved methodology to quantify recent variability in meridional and ocean to land heat transports since 1985. A global top of atmosphere net imbalance is found to increase from 0.10 ± 0.61 W m−2 over 1985–1999 to 0.62 ± 0.1 W m−2 over 2000–2016, and the uncertainty of ± 0.61 W m−2 is related to the Argo ocean heat content changes (± 0.1 W m−2) and an additional uncertainty applying prior to 2000 relating to homogeneity adjustments. The net top of atmosphere radiative flux imbalance is dominated by the southern hemisphere (0.36 ± 0.04 PW, about 1.41 ± 0.16 W m−2) with an even larger surface net flux into the southern hemisphere ocean (0.79 ± 0.16 PW, about 3.1 ± 0.6 W m−2) over 2006–2013. In the northern hemisphere the surface net flux is of opposite sign and directed from the ocean toward the atmosphere (0.44 ± 0.16 PW, about 1.7 ± 0.6 W m−2). The sea ice melting and freezing are accounted for in the estimation of surface heat flux into the ocean. The northward oceanic heat transports are inferred from the derived surface fluxes and estimates of ocean heat accumulation. The derived cross-equatorial oceanic heat transport of 0.50 PW is higher than most previous studies, and the derived mean meridional transport of 1.23 PW at 26° N is very close to 1.22 PW from RAPID observation. The surface flux contribution dominates the magnitude of the oceanic transport, but the integrated ocean heat storage controls the interannual variability. Poleward heat transport by the atmosphere at 30° N is found to increase after 2000 (0.17 PW decade−1). The multiannual mean (2006–2013) transport of energy by the atmosphere from ocean to land is estimated as 2.65 PW, and is closely related to the ENSO variability.

Surface wave field under binary typhoons Sarika and Haima (2016) in South China Sea

The effects of the binary typhoon on the surface wave field in the South China Sea (SCS) were investigated using the third-generation wave model WaveWatch Ⅲ (WWⅢ). The surface wave field during the binary typhoons Sarika and Haima (2016) was reproduced with blended winds and two nested domains, and the simulation results obtained are in good agreement with the satellite altimeter data. To investigate different wave characteristics under binary and individual typhoons, a numerical experiment was designed with the multi-annual mean winds replacing one cyclone of the blended binary typhoons, and its results were compared with the simulation results of realistic binary typhoons. The comparison suggests that the surface waves induced by the binary typhoon not only have higher intensity, but also exhibit more complex behaviors. Binary typhoons cause an increase in the significant wave height (Hs) inside the maximum wind radius of the latter typhoon (Haima). Factors affecting the enhanced Hs on the surface wave field include typhoon intensity, maximum wind radius, and typhoon translation speeds. The interactions between waves generated by Haima and Sarika enhance extreme waves by 4%–5%. The response of wave characteristics of Sarika and Haima to the monsoon winds is different. For wave spectra, bi-modal features are widespread on the surface wave field between the interval of the two typhoons, even if the separation distance between them is greater than 1700 km.

Cloud_cci Advanced Very High Resolution Radiometer post meridiem (AVHRR-PM) dataset version 3: 35-year climatology of global cloud and radiation properties

Abstract. We present version 3 of the Cloud_cci Advanced Very High Resolution Radiometer post meridiem (AVHRR-PM) dataset, which contains a comprehensive set of cloud and radiative flux properties on a global scale covering the period of 1982 to 2016. The properties were retrieved from AVHRR measurements recorded by the afternoon (post meridiem – PM) satellites of the National Oceanic and Atmospheric Administration (NOAA) Polar Operational Environmental Satellite (POES) missions. The cloud properties in version 3 are of improved quality compared with the precursor dataset version 2, providing better global quality scores for cloud detection, cloud phase and ice water path based on validation results against A-Train sensors. Furthermore, the parameter set was extended by a suite of broadband radiative flux properties. They were calculated by combining the retrieved cloud properties with thermodynamic profiles from reanalysis and surface properties. The flux properties comprise upwelling and downwelling and shortwave and longwave broadband fluxes at the surface (bottom of atmosphere – BOA) and top of atmosphere (TOA). All fluxes were determined at the AVHRR pixel level for all-sky and clear-sky conditions, which will particularly facilitate the assessment of the cloud radiative effect at the BOA and TOA in future studies. Validation of the BOA downwelling fluxes against the Baseline Surface Radiation Network (BSRN) shows a very good agreement. This is supported by comparisons of multi-annual mean maps with NASA's Clouds and the Earth's Radiant Energy System (CERES) products for all fluxes at the BOA and TOA. The Cloud_cci AVHRR-PM version 3 (Cloud_cci AVHRR-PMv3) dataset allows for a large variety of climate applications that build on cloud properties, radiative flux properties and/or the link between them. For the presented Cloud_cci AVHRR-PMv3 dataset a digital object identifier has been issued: https://doi.org/10.5676/DWD/ESA_Cloud_cci/AVHRR-PM/V003 (Stengel et al., 2019).

Impact of weather types on UK ambient particulate matter concentrations

Each year more than 29,000 premature deaths in the UK are linked to long term-exposure to ambient particulate matter (PM) with a diameter less than 2.5 μm (PM 2.5 ). Many studies have focused on the long-term impacts of exposure to PM, but short-term increases in pollution can also exacerbate health effects, leading to deaths brought forward within exposed populations. This study investigates the impact of different atmospheric circulation patterns on UK PM 2.5 concentrations and the relative contribution of local and transboundary pollutants to variations in PM 2.5 concentrations. Daily mean PM 2.5 observations from 42 UK background sites indicate that easterly, south-easterly and southerly wind directions and anticyclonic circulation patterns enhance background concentrations of PM 2.5 at all UK sites by up to 12 μg m -3 . Results from back trajectory analysis and the European Monitoring and Evaluation Programme for UK model (EMEP4UK) show this is due to the transboundary transport of pollutants from continental Europe. While back trajectories indicate under easterly, south-easterly and southerly flow 25–50% of the total accumulated primary PM 2.5 emissions originate outside of the UK, with a very polluted footprint (0.25–0.35 μg m -2 ). Anticyclonic conditions, which occur frequently (21%), also lead to increases in PM 2.5 concentrations (UK multi-annual mean 14.7 μg m -3 ). EMEP4UK results indicate this is likely due the build-up of local emissions due to slack winds. Under westerly and north-westerly flow 15–30% of the total accumulated primary PM 2.5 emissions originate outside of the UK, and are much less polluted (0.1 μg m -2 ) with model results indicating transport of clean maritime air masses from the Atlantic. Results indicate that both wind-direction and stability under anticyclonic conditions are important in controlling ambient PM 2.5 concentrations across the UK. There is also a strong dependence of high PM 2.5 Daily Air Quality Index (DAQI) values on easterly, south-easterly and southerly wind-directions, with >70% of occurrences of observed 48–71+ μg m -3 concentrations occurring under these wind directions. While north-westerly and cyclonic conditions reduce PM 2.5 concentrations at all sites by up to 8 μg m -3 . PM 2.5 DAQI values are also lowest under these conditions, with >80% of 0–11 μg m -3 concentrations and >50% of 12–23 μg m -3 concentrations observed during westerly, north-westerly and northerly wind directions. Indicating that these conditions are likely to be associated with a reduction in the potential health effects from exposure to ambient levels of PM 2.5 . • Easterly, south-easterly and southerly winds increase ambient PM 2.5 across the UK. • Increased PM 2.5 is due to long-range transport of PM 2.5 from continental Europe. • Anticyclonic conditions also increase PM 2.5 due to low wind-speeds. • This leads to the build-up of pollutants from local emissions. • Both long-range transport and local emissions are important in controlling UK PM 2.5 .

ОЦІНКА ВПЛИВУ ЗМІН КЛІМАТУ НА АГРОКЛІМАТИЧНІ УМОВИ ФОРМУВАННЯ ПРОДУКТИВНОСТІ ЛУЧНОЇ ТА СТЕПОВОЇ РОСЛИННОСТІ ПІВНІЧНОГО СТЕПУ УКРАЇНИ

Impact of climate change on the agro climatic conditions of growth, development and productivity of grassland and steppe vegetation in the Ukrainian Steppe is studied for three periods of 2021–2030 years, 2031–2040 years, 2041–2050 years by comparing the multiannual means for the 1961-1990 period. The expected conditions in three periods are calculated under the RCP4.5 and RCP8.5 scenarios. Three categories of the productivity of grasses, namely potential yield, meteorologically possible yield, practically possible yield, and conditions of forming of leaf surface, rate of photosynthesis and photosynthetic potential, are considered. Under the mean multiannual agricultural meteorology conditions, the potential yield of all dry matter in grass is 385 center/ha. Calculations based on scenarios show, that during two first appraisal periods potential yields will amount to 124–127% from the multiannual mean, and for the third calculation period potential yield will amount to 108% from the multiannual mean. Dry matter in meteorologically possible yield in the first period under both scenarios will be expected at the level of 130–136% of the multiannual mean, relatively fewer one will be expected in the second and third appraisal periods – within the limits of 123–130% from the multiannual mean. The practically possible yield of dry matter in plants, stipulated by natural fertility of soil, will amount to 138% from the multiannual mean in the first period, in the second and third periods such yield will be 123–131%. It is found that under the multiannual mean conditions yield of above-ground mass in steppe vegetation under the standard humidity of 16% is 1,3 t/ha. In scenario periods the potential yields will be expected at the level of 120–123% from the multiannual mean. Calculations showed that under the climate change in the case of realization of scenarios of RCP4.5 and RCP8.5 the increase of humus balance is assumed in all three appraisal periods. In the first period the increase will reach 136% from the multiannual mean, in the second and third ones the increase will be to 125–130%.