Sea Ice Leads Detection Using SARAL/AltiKa Altimeter

Sea ice leads play an essential role in ocean-ice-atmosphere exchange, in ocean circulation, geochemistry, and in ice dynamics. Their precise detection is crucial for altimetric estimations of sea ice thickness and volume. This study evaluates the performance of the SARAL/AltiKa (Satellite with ARgos and ALtiKa) altimeter to detect leads and to monitor their spatio-temporal dynamics. We show that a pulse peakiness parameter (PP) used to detect leads by Envisat RA-2 and ERS-1,-2 altimeters is not suitable because of saturation of AltiKa return echoes over the leads. The signal saturation results in loss of 6–10% of PP data over sea ice. We propose a different parameter—maximal power of waveform—and define the threshold to discriminate the leads. Our algorithm can be applied from December until May. It detects well the leads of small and medium size from 200 m to 3–4 km. So the combination of the high-resolution altimetric estimates with low-resolution thermal infra-red or radiometric lead fraction products could enhance the capability of remote sensing to monitor sea ice fracturing.     

Responses to salt stress in the halophyte Plantago crassifolia (Plantaginaceae)

General responses to salt stress have been investigated in the halophyte Plantago crassifolia. Seed germination was strongly inhibited by NaCl, although seed viability and germination capacity were not affected by salt pre-treatments. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl, which was accompanied by the accumulation of Na⁺ ions in the leaves, as determined by cation exchange HPLC. A 20-fold increase of proline content in leaves was observed when plants were treated with 500 m NaCl, suggesting a protective role against high salinity stress for this amino acid, whose possible mechanism of action is discussed.     

Valuing the recovery of overexploited fish stocks in the context of existence and option values

The current reduction in commercial fish stocks is a problem of global concern. In response to this situation, administrations around the world are attempting to recover critical stocks by implementing new regulations based on catching restrictions and recovery plans. These restrictions have negative effects on local economies, but species recovery also brings important benefits to society in the long term. Given that the recovery of endangered species also results in considerable non-use economic value, this paper employs contingent valuation techniques to measure individual preferences for different recovery levels. We distinguish primarily between existence and option values linked to various levels of the desired stocks and discuss how these values influence willingness to pay (WTP) estimates. Our results show that recovered stocks for hake and Norwegian lobster increase local welfare, and show that the median household WTP is about 17.73€ for a recovery programme regulated by the European Union.     

Targeted GOES Satellite Observations to Improve Hurricane Track Forecast: A Case Study of Hurricane Floyd

This study performs a set of Observing System Simulation Experiments (OSSEs) using Geostationary Operational Environmental Satellite (GOES) soundings. The primary objective of the OSSEs is to demonstrate that targeted observations can improve forecast accuracy by enhancing the initial conditions and mitigating their uncertainties. Hurricane Floyd (1999) is chosen as a study case. The main reason for choosing hurricane Floyd as a test case is that the movement of the storm was dictated by a mid-level complex polar jet steering flow region. This well-defined feature allowed us to examine the inaccuracy of analysis over the steering flow area using GOES soundings as targeted observations and its impact on the forecast track error. The set of experiments starts from a baseline forecast of hurricane Floyd using the Operational Multiscale Environment model with Grid Adaptivity (OMEGA). From GOES satellite soundings, atmospheric vertical profiles were extracted to simulate targeted observations. These data extracts were assimilated in the initial conditions to simulate new forecasts of hurricane Floyd which were then compared against both the baseline track and observed track. It was found that targeted observations in a forecast sensitive area can help to reduce hurricane forecast track error. Assimilation of only the subset of data (about 50 soundings) from the subjectively chosen fully sampled target region produced a considerable reduction of the track forecast errors (about 30%) within the first critical three days of the forecast.     

Detection of Flow Distortions and Systematic Errors in Sonic Anemometry Using the Planar Fit Method

We describe the coordinate transformations that can be used to convert the velocity components measured by a set of sonic anemometers with time-dependent tilt fluctuations into a single, time-independent coordinate system. By applying the planar fit method (PFM) to each anemometer dataset, it is possible, for planar flows, to locate the flow plane at each measurement point and compare its orientation with the topography. Installation on a ship is also considered. An application of this method to intercomparison data has led to the detection of an instrument error due to a misalignment between the assembly of the sonic transducers and the anemometer pedestal. If this error occurs, pedestal levelling does not guarantee that measurements are unbiased. A correction method is proposed and the results of two experiments are shown. Flow planarity at different levels and flow distortion caused by the mast are highlighted. The influence of the error on the evaluation of the Reynolds stresses using PFM or the double rotation method and the triple rotation method is discussed and the tilt corrected stresses calculated using the three methods compared.     

Eastern Mediterranean summer temperatures since 730 CE from Mt. Smolikas tree-ring densities

The Mediterranean has been identified as particularly vulnerable to climate change, yet a high-resolution temperature reconstruction extending back into the Medieval Warm Period is still lacking. Here we present such a record from a high-elevation site on Mt. Smolikas in northern Greece, where some of Europe’s oldest trees provide evidence of warm season temperature variability back to 730 CE. The reconstruction is derived from 192 annually resolved, latewood density series from ancient living and relict Pinus heldreichii trees calibrating at r1911–2015 = 0.73 against regional July–September (JAS) temperatures. Although the recent 1985–2014 period was the warmest 30-year interval (JAS Twrt.1961–1990 = + 0.71 °C) since the eleventh century, temperatures during the ninth to tenth centuries were even warmer, including the warmest reconstructed 30-year period from 876–905 (+ 0.78 °C). These differences between warm periods are statistically insignificant though. Several distinct cold episodes punctuate the Little Ice Age, albeit the coldest 30-year period is centered during high medieval times from 997–1026 (− 1.63 °C). Comparison with reconstructions from the Alps and Scandinavia shows that a similar cold episode occurred in central Europe but was absent at northern latitudes. The reconstructions also reveal different millennial-scale temperature trends (NEur = − 0.73 °C/1000 years, CEur = − 0.13 °C, SEur = + 0.23 °C) potentially triggered by latitudinal changes in summer insolation due to orbital forcing. These features, the opposing millennial-scale temperature trends and the medieval multi-decadal cooling recorded in Central Europe and the Mediterranean, are not well captured in state-of-the-art climate model simulations.     

Urban heat island investigations in Arctic cities of northwestern Russia

Urban microclimate peculiarities in two Arctic cities in northwestern Russia—Kirovsk (67.62°N, 33.67°E) and Apatity (67.57°N, 33.38°E)—were investigated by using mobile temperature records. The experiment was carried out in and around Apatity and Kirovsk in February 2014 and December 2016. The DS18B20 digital thermometer was installed on the roof of a car (height: approximately 1.2 m) to measure and record temperature variations automatically. In addition to the digital thermometer, the car was also equipped with an onboard global positioning system, allowing every temperature measurement to be referenced with an altitude and a latitude/longitude position. The possibility of urban heat island formation in these polar cities, above the Arctic Circle, was studied. Our analysis indicated that on 11 February 2014, the temperature varied in accordance with the background environmental lapse rate (–0.0045°C m^–1), and nearly corresponded to it (–0.0165°C m^–1) on 12 February 2014. On 6 December 2016, a strong local temperature inversion with a positive value of 0.032°C m^–1 was detected, seemingly caused by the formation of a cold air pool in the valley near Kirovsk. It was found that the temperature variations within and outside these cities are strongly influenced by local topographic effects and the physical conditions of the atmospheric boundary layer.     

Modeling climate change and biophysical impacts of crop production in the Austrian Marchfeld Region

Climate change affects major biophysical processes in agricultural crop production (e.g. evaporation of plants and soils, nutrient cycles, and growth of plants). This analysis aims to assess some of these effects by simulating regional climate projections that are integrated in the biophysical process model EPIC (Environmental Policy Integrated Climate). Statistical climate models have been developed for six weather parameters based on daily weather records of a weather station in the Austrian Marchfeld region from 1975 to 2006. These models have been used to estimate daily weather parameters for the period 2007–2038. The resulting projections have been compared to climate scenarios provided from the TYNDALL Centre for Climate Change Research, which are based on General Circulation Models (GCMs). The comparison indicates some differences, namely a smaller temperature increase and a higher precipitation amount in the TYNDALL data. Both climate datasets have been used to simulate impacts of climate change on crop yields, topsoil organic carbon content, and nitrate leaching with EPIC and thus to perform a sensitivity analysis of EPIC. Yield impacts have been assessed for four simulated crops, i.e. 6.2?t/ha for winter wheat for statistical climate projections compared to 5.7?t/ha for TYNDALL scenarios, 10.6?t/ha for corn compared to 10.5?t/ha, 3.9?t/ha for sunflower compared to 3.7?t/ha, and 4.5?t/ha for spring barley compared to 4.3?t/ha—all values as an average over the period 2007–2038. Smaller differences have been simulated for topsoil organic carbon content i.e. 55.1?t/ha for the statistical climate projections compared to 55.3?t/ha for the TYNDALL scenarios and nitrate leaching i.e. 7.1?kg/ha compared to 11.1?kg/ha. All crop yields as well as topsoil organic carbon content and nitrate leaching show highest sensitivity to temperature and solar radiation.     

The Mechanism of Reactive NO3 Uptake on Dry NaX (X=Cl, Br)

A simple kinetic mechanism of nitrate radicals uptake on dry sea-salt NaCl, NaBr surfaces is proposed. The mechanism includes adsorption/desorption equilibrium and unimolecular decomposition of the adsorbed complex: NO₃(g) + NaX(s) (NO₃-NaX)(s); (NO₃-NaX)(s) NaNO₃ + X(s) Two techniques were used: the matrix isolation ESR and mass spectrometry. The uptake coefficient () is found to be dependent on exposure time of salt to NO₃ for raw coating. The initial (t0) is higher than the observable steady-state _obs. At room temperature _obs is independent of [NO₃] at low [NO₃] = 3 × 10⁹ - 10¹¹ cm^-3, but it is inversely proportional to [NO₃] at concentrations higher than 10¹² cm^-3. At temperatures above 100 °C, _obs becomes independent of [NO₃] in a wider range of [NO₃]. An increased number of dislocations is supposed to exist in the case of raw coating. Due to a wide spread of the surface sites binding energy with the ionic lattice near dislocations, the part of surface complexes has lower binding energy and "burns" more rapidly. That burning determines the transition from (t0) down to _obs.The kinetic parameters and elementary rate coefficients are obtained. The recommended for low atmospheric NO₃ concentration are in the range of 0.002 ± 0.04 for NaCl and 0.1-0.3 for NaBr depending on a mechanism of the (t) relaxation.