A Later Onset of the Rainy Season in California Luković, Jelena; Chiang, John C. H.; Blagojević, Dragan ...
Geophysical research letters,
28 February 2021, 2021-02-28, Letnik:
48, Številka:
4
Journal Article
Recenzirano
Californian hydroclimate is strongly seasonal and prone to severe water shortages. Recent changes in climate trends have induced shifts in seasonality, thus exacerbating droughts, wildfires, and ...adverse water shortage effects on the environment and economy. Previous studies have examined the timing of the seasonal cycle shifts mainly as temperature driven earlier onset of the spring season. In this paper, we address quantitative changes in the onset, amounts, and termination of the precipitation season over the past 6 decades, as well as the large‐scale atmospheric circulation underpinning the seasonal cycle changes. We discover that the onset of the rainy season has been progressively delayed since the 1960s, and as a result the precipitation season has become shorter and sharper in California. The progressively later onset of the rainy season is shown to be related to the summer circulation pattern extending into autumn across the North Pacific, in particular, a delay in the strengthening of the Aleutian Low and later southward displacement of the North Pacific westerlies.
Plain Language Summary
The rainy season over California is projected to show a distinct sharpening of the mean seasonal cycle, with winter precipitation increasing, and both autumn and spring precipitation decreasing. Our analysis of the past 6 decades of data for California suggests autumn decrease is already underway. A delayed start of the rainy season of 27 days since 1960s can exacerbate seasonal droughts and prolong the wildfire season. This delay occurs due to a number of conditions that controls precipitation: the summer circulation pattern has been extending throughout November across the North Pacific, and the wintertime strengthening of the Aleutian Low is delayed. Accordingly, the southward migration of the North Pacific jet stream as well as extratropical storm tracks are delayed, which marks the start of the California rainy season, are delayed. More work, using climate models, will be needed to provide a better understanding of atmospheric conditions across the North America and the North Pacific. However, our findings provide observational evidence for the projected rainfall change over California and inform ongoing discussion about the drying/wetting tendencies of the rainy season in California.
Key Points
Rainfall data over the last 6 decades suggests a progressively delayed onset to the rainy season over California
A corresponding delay occurs in the transition from summer to wintertime circulation over the North Pacific
Observed autumn trends appear consistent with projected future shortening of the California rainy season
Using the Rescaled Adjusted Partial Sums (RAPS) and spectral analysis methods, the study aimed to extract subperiods (a break point analysis) based on data from 18 meteorological stations in ...Montenegro and determine the elementary periodicity using the Lomb periodogram of mean seasonal and annual air temperatures and precipitation totals for the period 1961–2020. Prior to this, trend calculations were performed, which showed a significant increase in mean seasonal and annual temperatures, with the most intense warming occurring in the summer (from 0.30 to 0.75 °C/decade). Trends in seasonal and annual precipitation totals are insignificant. According to RAPS values, two subperiods are clearly distinguished for temperatures, and a sudden increase in mean annual temperatures at 11 stations (61.1%) occurred only in 1997 and 1998. The year 1991 was a break point in 22.1% of cases. For seasonal and annual precipitation totals, a minimum of 4 subseries can be distinguished at all stations. According to the RAPS method, the years 2002 and 2003 most frequently appear as the last pivotal points leading to an increase in annual precipitation totals. In terms of precipitation, the most prominent periodicity observed is at 2.1 and 3.6 years, suggesting a quasi-biennial oscillation. Additionally, a 14.7-year periodicity is noted in winter precipitation, and a 3-year periodicity signals ENSO. Regarding average annual and seasonal temperatures, short-term (2–3 years), medium-term (4–5 years) and long-term (6, 8 and over 20 years) periodicities are distinguished. Only at two stations, was the Markowitz wave (MW) signal.
Ab initio calculations using hybrid B3LYP functional were performed in order to investigate structural, electronic and mechanical properties of aluminum nitride as function of pressure. Electronic ...properties of the experimentally observed aluminum nitride modifications at standard and high pressures have been investigated. Furthermore, mechanical properties for each of the predicted and experimentally observed AlN modifications have been investigated in order to get insight into the phase stability. In addition, ductility/brittleness relationship, character of the bonding, and the relationship between calculated hardness Hv, Young's modulus E, bulk modulus B, and shear modulus K have been investigated. In this way, we address new possibilities for improving the mechanical and elastic properties of AlN based ceramic materials, as well as possible band gap tuning, which might have applications in optoelectronic devices.
•Electronic properties of aluminum nitride.•Mechanical stability of the novel AlN structure types.•High pressure investigations.•Band gap tuning with possible applications in optoelectronics.•Elastic properties with improved corrosion resistance of AlN based ceramic materials.
Metabolism of metals in microalgae and adaptation to metal excess are of significant environmental importance. We report a three-step mechanism that the green microalga Chlorella sorokiniana ...activates during the acquisition of and adaptation to manganese (Mn), which is both an essential trace metal and a pollutant of waters. In the early stage, Mn2+ was mainly bound to membrane phospholipids and phosphates in released mucilage. The outer cell wall was reorganized and lipids were accumulated, with a relative increase in lipid saturation. Intracellular redox settings were rapidly altered in the presence of Mn excess, with increased production of reactive oxygen species that resulted in lipid peroxidation and a decrease in the concentration of thiols. In the later stage, Mn2+ was chelated by polyphosphates and accumulated in the cells. The structure of the inner cell wall was modified and the redox milieu established a new balance. Polyphosphates serve as a transient Mn2+ storage ligand, as proposed previously. In the final stage, Mn was stored in multivalent Mn clusters that resemble the structure of the tetramanganese-calcium core of the oxygen-evolving complex. The present findings elucidate the bioinorganic chemistry and metabolism of Mn in microalgae, and may shed new light on water-splitting Mn clusters.
Characterizing the landscape of clinical trials including brachytherapy can provide an overview of the current status and research trends which may guide further areas of investigation.
We queried ...449,849 clinical trials from the ClinicalTrials.gov registry using brachytherapy-related keywords from 1980 to 2023, yielding 245 multi-arm and 201 single-arm, brachytherapy trials. Multi-arm and single-arm brachytherapy trials were compared using 12 trial protocol elements.
The number of trials including brachytherapy has increased over time, with over 60% of trials registered in 2010 onwards. The majority of clinical trials were Phase 2 or 3, evaluated both safety and efficacy, and were funded by academic sponsors. The most common tumor sites evaluated in brachytherapy clinical trials include prostate, cervix, liver, endometrium, and breast.
There remains continued interest in clinical trials including brachytherapy focused on evaluation of novel delivery systems, treatment planning, and new indications. More brachytherapy clinical trials are needed to define the optimal clinical utilization and advance prospective research in this field.
The spatial analysis of annual and seasonal temperature trends in Serbia during the period 1961–2010 was carried out using mean monthly data from 64 meteorological stations. Change year detection was ...achieved using cumulative sum charts. The magnitude of trends was derived from the slopes of linear trends using the least square method. The same formalism of least square method was used to assess the statistical significance of the determined trends. Maps of temperature trends were generated by applying a spatial regression method to visualize the detected tendencies. The obtained results indicate a negative temperature trend for the period before the change year except for winter and a more pronounced positive trend after the change year. Besides being more pronounced, the vast majority of trends after the change year were also clearly statistically significant. Our estimate of the average temperature trend over Serbia is in agreement with those obtained at the global and European scale. Calculated global autocorrelation statistics (Moran’s I) indicate an apparent random spatial pattern of temperature trends across the Serbia for both periods before and after the change year.
ABSTRACT
Rain spells are a key parameter in examining rainfall regime. A rain spell is defined as a series of consecutive days above a certain daily rainfall threshold (DRT). For each rain spell, its ...duration (RSD), yield (RSY) and average intensity (RSI), as well as their total number (NRS) in each year, were calculated.
The present study analyses daily rainfall series from 22 stations representing the different regions of Serbia and Montenegro in the period 1949–2007. This study highlights the temporal variability (both inter‐ and intra‐annual) and the complexity of the rainfall regime in both countries.
In each station, all years were divided into three categories: wet, normal and dry according to their standard scores. Then, on the basis of these scores, the entire year was categorized accordingly. The various rain‐spell parameters were calculated and are presented for each of these three categories. The relationships between NRS (exponential), RSY (linear) and RSI (power) with the RSD were calculated for each station and their coefficients were plotted.
The entire study area was divided into three sub‐regions in terms of similar annual behaviour, using the factor analysis. The regions are as follows: northern and central Serbia, eastern and southern Serbia and Montenegro.
All years were grouped into several clusters, each representing a different spatial distribution. Their characteristics and probabilities are presented.
Overall, Montenegro is much rainier than Serbia, having longer and more intense rain spells. Serbia, on the other hand, has more short rain spells than Montenegro and demonstrates no real summer dryness such as in Montenegro. Intra‐annual variability is relatively high in both countries, slightly higher in Montenegro.
The impact of ionizing radiation on microorganisms such as microalgae is a topic of increasing importance for understanding the dynamics of aquatic ecosystems in response to environmental radiation, ...and for the development of efficient approaches for bioremediation of mining and nuclear power plants wastewaters. Currently, nothing is known about the effects of ionizing radiation on the microalgal cell wall, which represents the first line of defence against chemical and physical environmental stresses. Using various microscopy, spectroscopy and biochemical techniques we show that the unicellular alga Chlorella sorokiniana elicits a fast response to ionizing radiation. Within one day after irradiation with doses of 1–5 Gy, the fibrilar layer of the cell wall became thicker, the fraction of uronic acids was higher, and the capacity to remove the main reactive product of water radiolysis increased. In addition, the isolated cell wall fraction showed significant binding capacity for Cu2+, Mn2+, and Cr3+. The irradiation further increased the binding capacity for Cu2+, which appears to be mainly bound to glucosamine moieties within a chitosan-like polymer in the outer rigid layer of the wall. These results imply that the cell wall represents a dynamic structure that is involved in the protective response of microalgae to ionizing radiation. It appears that microalgae may exhibit a significant control of metal mobility in aquatic ecosystems via biosorption by the cell wall matrix.
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•Ionizing radiation represents an environmental factor of increasing importance.•Microalga Chlorella sorokiniana elicits a fast response to ionizing radiation.•The fibrilar layer of the cell wall becomes thicker.•Antioxidative and metal-binding capacities of the cell wall increase.•Cell wall is involved in the protective response of microalgae to radiation.
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