This paper aims to explore improving the accuracy of water vapor retrieval in all-weather conditions by combining the recordings of the near-infrared (NIR) and thermal infrared (TIR) bands of the ...Moderate-resolution Imaging Spectroradiometer (MODIS). When analyzing different input parameters, we found that the NIR methods are more strongly influenced by a high cloud density than the IR methods. This motivated us to developed an improved model, named Resilient Combination Model of NIR and TIR bands (RCMNT), that is based on machine learning algorithms and optimizes the accuracy of water vapor retrieval depending on varying cloud cover densities. The RCMNT uses high-precision Precipitable Water Vapor (PWV) retrieved by the Global Navigation Satellite System (GNSS) as reference for model training. Compared with GNSS PWV, the results show that the RCMNT is superior to the MOD05 in terms of spatio-temporal forecast accuracy. The RCMNT reveals a significant improvement in accuracy of 69.06% and a reduction in the root mean square error (RMSE) by 6.9335 mm under all-weather conditions compared to MOD05. The RCMNT also shows a substantial enhancement under cloudy conditions, with an increase in temporal prediction accuracy of 69.47% and an improvement in spatial prediction accuracy of 69.84%. The RMSE of the RCMNT decreased by 7.0251 mm, resulting in a 69.50% improvement in accuracy compared to MOD05 under cloudy conditions. Overall, the RCMNT shows its potential through a combined analysis of NIR and TIR data, achieving more accurate results for PWV retrieval across various spatio-temporal scales and weather conditions.
In recent decades, an increasing persistence of atmospheric circulation patterns has been observed. In the course of the associated long-lasting anticyclonic summer circulations, heatwaves and ...drought spells often coincide, leading to so-called hotter droughts. Previous hotter droughts caused a decrease in agricultural yields and an increase in tree mortality. Thus, they had a remarkable effect on carbon budgets and negative economic impacts. Consequently, a quantification of ecosystem responses to hotter droughts and a better understanding of the underlying mechanisms are crucial. In this context, the European hotter drought of the year 2018 may be considered a key event. As a first step towards the quantification of its causes and consequences, we here assess anomalies of atmospheric circulation patterns, maximum temperature, and climatic water balance as potential drivers of ecosystem responses which are quantified by remote sensing using the MODIS vegetation indices (VIs) normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). To place the drought of 2018 within a climatological context, we compare its climatic features and remotely sensed ecosystem response with the extreme hot drought of 2003. The year 2018 was characterized by a climatic dipole, featuring extremely hot and dry weather conditions north of the Alps but comparably cool and moist conditions across large parts of the Mediterranean. Analysing the ecosystem response of five dominant land cover classes, we found significant positive effects of climatic water balance on ecosystem VI response. Negative drought impacts appeared to affect an area 1.5 times larger and to be significantly stronger in July 2018 compared to August 2003, i.e. at the respective peak of drought. Moreover, we found a significantly higher sensitivity of pastures and arable land to climatic water balance compared to forests in both years. We explain the stronger coupling and higher sensitivity of ecosystem response in 2018 by the prevailing climatic dipole: while the generally water-limited ecosystems of the Mediterranean experienced above-average climatic water balance, the less drought-adapted ecosystems of central and northern Europe experienced a record hot drought. In conclusion, this study quantifies the drought of 2018 as a yet unprecedented event, outlines hotspots of drought-impacted areas in 2018 which should be given particular attention in follow-up studies, and provides valuable insights into the heterogeneous responses of the dominant European ecosystems to hotter drought.
Alternaria conidia have high allergenic potential and they can trigger important respiratory diseases. Due to that and to their extensive detection period, airborne Alternaria spores are considered ...as a relevant airborne allergenic particle. Several studies have been developed in order to predict the human exposure to this aeroallergen and to prevent their negative effects on sensitive population. These studies revealed that some sampling locations usually have just one single Alternaria spore season while other locations generally have two seasons within the same year. However, the reasons of these two different seasonal patterns remain unclear. To understand them better, the present study was carried out in order to determine if there are any weather conditions that influence these different behaviours at different sampling locations. With this purpose, the airborne Alternaria spore concentrations of 18 sampling locations in a wide range of latitudinal, altitudinal and climate ranges of Spain were studied. The aerobiological samples were obtained by means of Hirst-Type volumetric pollen traps, and the seasonality of the airborne Alternaria spores were analysed. The optimal weather conditions for spore production were studied, and the main weather factor affecting Alternaria spore seasonality were analysed by means of random forests and regression trees. The results showed that the temperature was the most relevant variable for the Alternaria spore dispersion and it influenced both the spore integrals and their seasonality. The water availability was also a very significant variable. Warmer sampling locations generally have a longer period of Alternaria spore detection. However, the spore production declines during the summer when the temperatures are extremely warm, what splits the favourable period for Alternaria spore production and dispersion into two separate ones, detected as two Alternaria spore seasons within the same year.
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•Temperature is the main driving factor for the seasonality of Alternaria spores.•Warmer sampling locations have longer Alternaria spore seasons.•The water availability is also a relevant variable for Alternaria spore production.•Warm summers split in two the Alternaria spore season.
THE International Maritime Organization (IMO) has delineated several Emission Control Areas (ECAs), where ships must use more expensive low-sulphur fuel. To minimize total navigation costs, shipping ...companies should optimize both route and speed for any shipping event. There have been many studies on this topic, which have optimized route and speed separately. These studies can be divided into two categories according to route optimization strategy: cell-based and cell-free. The cell-based approach limits the searching direction, as the cell shapes are fixed; the cell-free approach cannot identify the time points when entering and leaving ECAs. This study proposed an improved cell-based method that considers the ECA regulations and weather conditions to simultaneously optimize the route and speed, which can overcome the shortcomings in cell-based and cell-free approach. Finally, a computational studies and comparative analysis with some other existing methods were performed. The results show that the proposed method can effectively reduce the total costs and the ship emissions within ECAs, but might increase the total emissions of the whole shipping event.
•Proposed a method for simultaneously optimizing ship route and speed under emissions control area regulations.•We perform and a comparative test with other methods.•Ship emissions within ECA are reduced and total emissions may increase.
Pyrocumulonimbus (pyroCb) wildfires cause devastation in many regions globally. Given that fire‐atmosphere coupling is associated with pyroCbs, future changes in coincident high index values of ...atmospheric instability and dryness (C‐Haines) and near‐surface fire weather are assessed for southeastern Australia using a regional climate projection ensemble. We show that observed pyroCb events occur predominantly on forested, rugged landscapes during extreme C‐Haines conditions, but over a wide range of surface fire weather conditions. Statistically significant increases in the number of days where both C‐Haines and near‐surface fire weather values are conducive to pyroCb development are projected across southeastern Australia, predominantly for November (spring), and less strongly for December (summer) in 2060‐2079 versus 1990‐2009, with future C‐Haines increases linked to increased 850‐hPa dewpoint depression. The increased future occurrence of conditions conducive to pyroCb development and their extension into spring have implications for mitigating these dangerous wildfires and urbanizing fire‐prone landscapes.
Plain Language Summary
Pyrocumulonimbus wildfires (pyroCb) are extreme wildfires. They involve a coupling between the fire and the atmosphere, which drives dangerous fire conditions that result in fatalities and considerable damage. Climate change could amplify the conditions associated with pyroCb development. We use high‐resolution regional climate projection data to assess future changes in the risk of pyroCb occurrence for southeastern Australia. We demonstrate that atmospheric instability and dryness is a better indicator of pyroCb development than surface fire weather conditions, with topographic roughness and vegetation type also playing roles. Coincidences of high index values of atmospheric conditions (tropospheric instability and dryness) and surface fire weather conditions (temperature, humidity, wind speed, and precipitation) associated with pyroCb development are projected to increase in frequency predominantly for November (spring) in 2060‐2079 versus 1990‐2009, but less so for summer. The extension of the season conducive to pyroCbs into spring is important because Australian pyroCbs are typically summer phenomena. A change in seasonality has implications for resource allocations by fire agencies. Projected changes in the conditions conducive to pyroCbs are primarily associated with increased dryness at 1.5‐km altitude. These findings are relevant to the mitigation of pyroCbs, and they have implications for continued urban expansion on fire‐prone landscapes.
Key Points
Significant increases in the frequency of conditions conducive to pyrocumulonimbus fires occur in November (Spring) 2060‐2079 versus 1990‐2009
Atmospheric instability and dryness are better indicators of pyrocumulonimbus fire development than surface fire weather
Locations in southeast Australia where these changes are projected to occur are identified
This paper provides an overview of existing literature on vessel/ship detection and classification from optical satellite imagery. Although SAR (Synthetic Aperture Radar) is still the leading ...technology for maritime monitoring, the number of studies based on optical satellite data is quickly growing. Altogether we analysed 119 papers on optical vessel detection and classification for the period from 1978 to March 2017. We start by introducing all the existing sensor systems for vessel detection, but subsequently focus only on optical imaging satellites. The article demonstrates the temporal development of optical satellite characteristics and connects this to the number and frequency of publications on vessel detection. After presenting the methods used for optical imagery-based vessel detection and classification in detail, along with the achieved detection accuracies, we also report possibilities for fusing optical data with other data sources. The studied papers show that the most common factors greatly influencing the vessel detection accuracy are the following: different weather conditions affecting sea surface characteristics, the quantity of clouds and haze, solar angle, and imaging sensor characteristics. All these factors bring great variations in the selection of the most suitable method; some still continue to pose unsolved challenges. For higher relevance and wider usage, we suggest that the algorithms for detection and classification should support a variety of targets and meteorological conditions, and ideally also a variety of optical satellite sensors. At least, they should be tested on many images under different conditions. This is not usually the case in the existent literature. We also observed that many authors omit an appropriate performance quantification, which is critical for a practical assessment and a numerical comparison of the presented algorithms. Overall it can be seen that vessel monitoring from spaceborne optical images is a popular research topic and has a great operational potential in the near future due to the large amount of satellite data, much of it free and open.
•A review of 119 papers on ship detection and classification from optical satellite.•From 1978 to March 2017, showing an exponential growth in the number of papers.•Most published methods have very limited validation.•While big steps have been made, automatic algorithms are still far from perfect.•Increase in new observation and processing capabilities promises rapid advances.
Abstract We introduce a 0.7 m telescope system at the Miryang Arirang Astronomical Observatory (MAAO), a public observatory in Miryang, Korea. System integration and a scheduling program enable the ...0.7 m telescope system to operate completely robotically during nighttime, eliminating the need for human intervention. Using the 0.7 m telescope system, we obtain atmospheric extinction coefficients and the zero-point magnitudes by observing standard stars. As a result, we find that atmospheric extinctions are moderate but they can sometimes increase depending on the weather conditions. The measured 5 σ limiting magnitudes reach down to BVRI = 19.4–19.6 AB mag for a point source with a total integrated time of 10 minutes under clear weather conditions, demonstrating comparable performance with other observational facilities operating under similar specifications and sky conditions. We expect that the newly established MAAO 0.7 m telescope system will contribute significantly to the observational studies of astronomy. Particularly, with its capability for robotic observations, this system, although its primary duty is for public viewing, can be extensively used for the time-series observation of transients.
During recent winters, hazes often occurred in Beijing, causing major environmental problems. To understand the causes of this “Beijing Haze”, a haze episode (from Oct. 21 to Oct. 31, 2013) in ...Beijing was analyzed. During the episode, the daily mean concentration of fine particulate matter (PM2.5) reached a peak value of 270 μg/m3 on Oct. 28, 2013, and rapidly decreased to 50 μg/m3 the next day (Oct. 29, 2013). This strong variability provided a good opportunity to study the causes of a “Beijing Haze”. Two numerical models were applied for this study. The first model is a chemical/dynamical regional model (WRF-Chem). This model is mainly used to study the effects that weather conditions have on PM2.5 concentrations in the Beijing region. The results show that the presence of high air pressure in northwest Beijing (NW-High) generally produced strong northwest winds with clean upwind air. As a result, the NW-High played an important role in cleaning Beijing's PM. However, the NW-High's cleaning effect did not occur in every situation. When there was low air pressure in southeast Beijing (SE-Low) accompanied by an NW-High, an air convergent zone appeared in Beijing. The pollutants became sandwiched, producing high PM2.5 concentrations in the Beijing region. The second model used in this study is a box model, which is applied to estimate some crucial parameters associated with the budget of PM2.5 in the Beijing region. Under calm winds, the calculations show that continuous local emissions rapidly accumulate pollutants. The PM2.5 concentrations reached 150 μg/m3 and 250 μg/m3 within one (1) day and two (2) days, respectively. Without horizontal dilution, this estimate can be considered as an upper time limit (the fastest time) for the occurrences of haze events in the Beijing region. The wind speed (WSb) is calculated for the balance between the continuous emissions and atmospheric clean processes. The results show that the WSb is strongly dependent on the planetary boundary layer (PBL) height and the wind direction. Under SE-Low weather conditions, the WSb is 2 m/s with a higher PBL height (700 m). However, under lower PBL heights, the WSb rapidly increases, reaching 4.5 m/s and 7.0 m/s with PBL heights of 300 m and 200 m, respectively. In contrast, under NW-High weather conditions, the WSb reduces to 2.5 m/s and 4.0 m/s. These results suggest that when the prevailing wind in Beijing is a northwest wind (with wind speeds of >4 m/s), particulate matter (PM) begins to decrease.
•A haze episode with a very strong variability in Beijing was analyzed.•WRF-Chem and a box model are used for the budget analysis of haze formation.•Under calm winds, a heavy haze can be formed in one (1) day.•The wind speed to balance emission-clean processes was calculated.
To circumvent this type of data-access issue, some have called for online information spaces to be studied in the same way as one might study pollution - in an 'ecological' framework that analyses ...the interactions of individuals with online applications in their natural environments5. Similar to the way in which environmental scientists install sensors around the globe to collect ecological data about weather conditions and pollution, the authors asked survey participants - US citizens recruited through a third party - to install an extension on their browser that allowed the researchers to gather information about three types of data: In 2021, the US National Science Foundation awarded US$9 million to 12 groups to research trust and authenticity in communication systems (see https://bit.ly/3WZMmhI), recognizing it as a 'complex societal challenge' It is a valuable investment, but more public funding and institutional support, including public-safeguarding policies (similar to those set by the US Food and Drug Administration), are needed to achieve a lasting impact.
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