Hasil untuk "Meteorology. Climatology"

Xuan YANG, Lu WEI, Baisheng MA et al.

Based on the hourly data of total irradiance observed by 26 ground radiation stations in Henan Province， the paper verified and analyzed the applicability of FY-4A inverted total irradiance products in Henan Province， and The Probability Density Function Matching Method was used to correct the systematic error of the FY-4A total irradiance product.The results showed that： （1） The total irradiance of FY-4A was greater than that of ground observation， and the average error of the two was larger in southern Henan and smaller in northern Henan.Moreover， from the perspective of time evolution， the relative error of the two was smaller in the winter half year and larger in the summer half year， this was related to the influence of meteorological elements such as cloud cover， relative humidity of atmosphere and different underlying surfaces on the total irradiance retrieved by FY-4A.（2） The average error of total irradiance of FY-4A satellite and ground observation varied with different irradiance levels， showing a non-independent systematic error as a whole， that was， it overestimated low irradiance and underestimated high irradiance.（3） The Probability Density Function Matching Method had a good correction ability for the total irradiance of FY-4A， and it was better to establish a revised model on an annual basis in summer to correct the error， and in autumn and winter， it was better to establish a revised model with the season as the time scale.

Abolghasem Akbari, Majid Rajabi Jaghargh, Azizan Abu Samah et al.

Abstract The Google Earth Engine (GEE) was used to investigate the performance of the Global Land Data Assimilation System (GLDAS) soil temperature (ST) data against observed ST from 13 synoptic stations over a semiarid region in Iran. Three‐hourly ST data were collected and analyzed in two depths (0–10 cm; 40–100 cm) and 5 years. In each depth, GLDAS‐Noah ST data were evaluated for daily minimum, maximum, and average ST (i.e., Tmin, Tmax, and Tavg). Based on the correlation coefficient, Kling–Gupta Efficiency, and Nash–Sutcliffe Efficiency the overall performance of the GLDAS‐Noah is 0.96, 0.66, and 0.79 for Tmin; 0.97, 0.84, and 0.89 for Tavg; and 0.95, 0.89, and 0.89 for Tmax, respectively in the first layer. Likewise, 0.97, 0.85, and 0.86 for Tmin; 0.97, 0.77, and 0.80 for Tavg; and 0.97, 0.69, and 0.69 for Tmax are obtained in the second layer. However, there is a significant negative bias which tends to underestimate ST in the two investigated layers, given by an average bias over all the stations analyzed of −24%, −12%, and −5% for Tmin, Tavg, and Tmax in the first layer, and average bias of −8%, −13%, and −17% for Tmin, Tavg, and Tmax in the second layer. This study reveals that GLDAS‐Noah‐derived ST can be used in arid regions where little or no observation data is available. Moreover, GEE performed as an advanced geospatial processing tool in regional scale analysis of ST in different layers.

Jinge Zhang, Chunxiang Li, Tianbao Zhao

Predicting future mean precipitation poses significant challenges due to uncertainties among climate models, complicating water resource management. In this study, we introduce a novel methodology to mitigate uncertainty in future mean precipitation projections over China on a grid-by-grid basis. By constraining precipitation parameters of the Gamma distribution, we establish emergent constraints on parameters, revealing significant correlations between historical and future simulations. Our analysis spans the periods 2040–2069 and 2070–2099 under low-to-moderate and high emission scenarios. We observe reductions in uncertainty across most regions of China, with constrained mean precipitation indicating increases in monsoon regions and decreases in non-monsoon zones relative to raw projections. Notably, the observed 30%–40% increase in mean precipitation for the whole of China underscores the efficacy of our methodology. These observationally constrained results provide valuable insights into current precipitation projections, offering actionable information for water resource planning and climate adaptation strategies amidst future uncertainties.

Anjali Thomas, Adrian McDonald, James Renwick et al.

This study quantifies the influences of anthropogenic forcing to date on precipitation over Aotearoa New Zealand (ANZ). Large ensembles of simulations from the weather@home regional climate model experiments are analysed under two scenarios, a natural (NAT) or counter-factual scenario which excludes human-induced changes to the climate system and an anthropogenic (ANT) or factual scenario. The impacts of anthropogenic forcing on precipitation are analysed in the context of large-scale circulation types characterized using an existing Self Organizing Map classification. The combined effect of both thermodynamics and dynamics are compared with values expected from the Clausius–Clapeyron (C–C) relation. Changes in the precipitation intensity due to greenhouse gas-forced temperature rise are lower than the expected C–C value. However extreme precipitation changes approach the C–C value for some circulation types. Specifically westerly flows enhance precipitation change across ANZ relative to the C–C rate, particularly over the West Coast. Conversely, northwesterly flows reduce the change over the North Island relative to the C–C value. Moreover, the wet day frequency generally reduces in the ANT scenario relative to NAT, reductions are largest on the West Coast of the South Island for westerly flows. Additionally, the frequency of days with extreme precipitation rises over ANZ for most circulation patterns, except in Northland and for northwesterly flows. This underscores the combined influence of dynamics and thermodynamics in shaping both precipitation intensity and frequency patterns across ANZ.

Andrew Collins, Michael Brown, Barrett Gutter et al.

This study examines heat exposure and its impact on the thermal comfort and health of spectators within a semi-outdoor American college football stadium in the southeastern United States. Over 50 sensors were deployed during the 2016 season from late August to late November to measure temperature and humidity across various stadium locations. Significant variations in temperature, heat index, and a modified version of the physiological equivalent temperature (mPET) were found within the stadium, with some areas exceeding National Weather Service heat alert thresholds during certain games. Moreover, mean temperatures in the stadium were higher than those measured at a nearby weather station, while the mean heat index was higher in the seating areas than in other stadium locations and at the nearby weather station. Reductions in modeled wind speed resulted in significant decreases in thermal comfort and greater physical stress among spectators, particularly when the wind was calm. Heat-related illness comprised up to two-thirds of all cases treated by first aid and emergency medical services during particularly hot games. Most of these occurred in the most thermally oppressive parts of the stadium. These results highlight the need for greater monitoring of heat exposure inside stadiums, earlier implementation of heat action plans to raise awareness and educate spectators on heat mitigation strategies, and incorporation of stadium design modifications that improve circulation, increase shade, and reduce crowding.

Muhammad Imran Khan, Qaisar Saddique, Xingye Zhu et al.

The Crop Water Stress Index (CWSI) is a useful tool for evaluating irrigation scheduling and achieving water conservation and crop yield goals. This study examined the CWSI under different water stress conditions for the scheduling of wheat crop irrigation and developed indices using the leaf canopy temperature in Faisalabad, Pakistan. The experiments were conducted using a randomized, complete block design and four irrigation treatments with deficit levels of D_0%, D_20%, and D_40% from the field capacity (FC) and D_100% (100% deficit level). The CWSI was determined at pre-heading and post-heading stages through the lower baseline (fully watered crop) and upper limit (maximum stress). These baselines were computed using the air temperature and canopy temperature of plant leaves and the vapor pressure deficit (VPD). The CWSI for each irrigation treatment was calculated and the average seasonal CWSI value for the whole season was used to develop the empirical relationships for scheduling irrigation. The relationships between the air canopy temperatures and the VPD resulted in slope (x) = −0.735 and interception (c) = −0.8731 as well as x = −0.5143 and c = −1.273 at the pre- and post-heading stages, respectively. The values of the CWSI for the treatment at deficit levels of D_0%, D_20%, D_40%, and D_100% were found to be 0.08, 0.61, 0.20, and 0.64, respectively. The CWSI values developed in this study can be effectively used to promote better the monitoring of irrigated wheat crops in the region.

Li-Wei Lai

Visibility is important because it influences transportation safety. This study examined the relationships among sea–land breezes, relative humidity (RH), and the urban heat island (UHI) effect. The study also sought to understand how the synergistic effects of fine particulate matter (PM_2.5) and RH influence visibility. Hourly meteorological, PM_2.5 concentration, and visibility data from 2016 to 2019 were obtained from government-owned stations. This study used quadratic equations, exponential functions, and multi-regression models, along with a comparison test, to analyse the relationships between these variables. While sea breezes alone cannot explain the presence of PM_2.5, UHI circulation coupled with sea breezes during winter can promote the accumulation of PM_2.5. The synergistic effects of RH, PM_2,5, and aerosol hygroscopicity exist in synoptic patterns type I and type III. PM_2.5 was negatively correlated with visibility in the winter, when the RH was 67–95% and the continental cold high-pressure (CCHP) system was over the Asian continent (type I), or when the RH was 49–89% and the CCHP had moved eastward, with its centre located beyond 125° E (type III). The synergistic predictor variable PM_2.5×RH was more important than PM_2.5 and RH individually in explaining the variation in visibility.

Adrija Roy, Raghu Murtugudde, A.K. Sahai et al.

The Extended Range Predictions (ERP) provide Sub-seasonal to Seasonal (S2S) prediction of meteorological variables at a lead time of multiple weeks. Despite the considerable improvements in the ERP system, their applications in real-time irrigation water management are limited. Such limited use of ERP is due to uncertainty in predictions and a spatial mismatch in scales between the model grids and farms. Here, we develop a chance-constrained optimization framework for farm-scale irrigation water management planning for multiple weeks in advance. The degrading model performance with time and the related uncertainty are addressed by generating large ensembles using weather generators. Working with grape farmers in India has revealed that such an advance planning could save water by 3–25 % at a farm-scale without losing yield, compared with the existing approach requiring near real-time decisions. Moreover, the co-development of such irrigation tools with farmers increases the use and usability of S2S predictions.

Keyi Chen, Jiao Fan, Zhipeng Xian

The dynamic emissivity retrieved from window channels of the microwave humidity sounder II (MWHS-2) onboard the China Meteorological Administration’s FengYun (FY)-3C polar orbiting satellite can provide more realistic emissivity over lands and potentially improve the numerical weather prediction (NWP) forecasts. However, whether the assimilation with the dynamic emissivity works for the precipitation forecasts over the complex geography is less investigated. In this paper, a typical precipitating case generated by the Southwest Vortex is selected and the Weather Research and Forecasting data assimilation (WRFDA) system is applied to examine the impacts of assimilating MWHS-2/FY-3C with the uses of the emissivity atlas and the dynamic emissivity on the forecasts. The results indicate that the use of the dynamic emissivity retrieved from the 89 GHz channel of MWHS-2/FY-3C apparently increases the used data number for assimilation and does improve the initial fields and the 24-hour forecasts (from 0000 UTC 24 June 2016 to 0000 UTC 25 June 2016) of precipitation distribution and intensity except for the rainfall over 100 mm. But these positive impacts are not evidently better than those with the emissivity atlas. In general, these results still suggest that the future use of the dynamic emissivity in the assimilation over the complex terrain is promising.

Senad Dizdar, Yezhe Lyu, Conny Lampa et al.

Airborne wear particle emission has been investigated in a pin-on-disc tribometer equipped with particle analysis equipment. The pins are cut out from commercial powder metallurgy automotive brake pads as with and without copper content. The discs are cut out from a commercial grey cast iron automotive brake disc as cut out and as in addition to a laser cladded with a powder mix of Ni-self fluxing alloy + 60% spheroidized fused tungsten carbide and then fine-ground. Dry sliding wear testing runs under a contact pressure of 0.6 MPa, sliding velocity of 2 m/s and a total sliding distance of 14,400 m. The test results show both wear and particle emission improvement by using laser cladded discs. The laser cladded discs in comparison to the reference grey cast iron discs do not alter pin wear substantially but achieves halved mass loss and quartered specific wear. Comparing in the same way, the friction coefficient increases from 0.5 to 0.6, and the particle number concentration decreases from over 100 to some 70 (1/cm³) and the partition of particles below 7 µm is approximately halved.

Gisela Dreschhoff, Högne Jungner, Claude M. Laird

In order to support the very high time resolution required to observe short-term variations in nitrates and all other ions represented by electrical conductivity in polar ice, a Fourier transform infrared spectrometer was developed for measurement of deuterium concentration in ice samples, as an additional support for the timescale of ultra-high resolution. The portable instrument provided the possibility to measure deuterium concentration on exactly the same samples as used for measuring nitrate concentrations and liquid electrical conductivity, thus verifying that the original dating of the annual variations in nitrate was correct. We present basic information about how the high-resolution data were obtained and discuss their reliability and significance.

Haili Wang, Changming Dong, Yongzeng Yang et al.

Turbulent motions in the thin ocean surface boundary layer control exchanges of momentum, heat and trace gases between the atmosphere and ocean. However, present parametric equations of turbulent motions that are applied to global climate models result in systematic or substantial errors in the ocean surface boundary layer. Significant mixing caused by surface wave processes is missed in most parametric equations. A Large Eddy Simulation model is applied to investigate the wave-induced mixed layer structure. In the wave-averaged equations, wave effects are calculated as Stokes forces and breaking waves. To examine the effects of wave parameters on mixing, a series of wave conditions with varying wavelengths and heights are used to drive the model, resulting in a variety of Langmuir turbulence and wave breaking outcomes. These experiments suggest that wave-induced mixing is more sensitive to wave heights than to the wavelength. A series of numerical experiments with different wind intensities-induced Stokes drifts are also conducted to investigate wave-induced mixing. As the wind speed increases, the influence depth of Langmuir circulation deepens. Additionally, it is observed that breaking waves could destroy Langmuir cells mainly at the sea surface, rather than at deeper layers.

Kingsley K. Kumah, Joost C. B. Hoedjes, Noam David et al.

Accurate rainfall detection and estimation are essential for many research and operational applications. Traditional rainfall detection and estimation techniques have achieved considerable success but with limitations. Thus, in this study, the relationships between the gauge (point measurement) and the microwave links (MWL) rainfall (line measurement), and the MWL to the satellite observations (area-wide measurement) are investigated for (area-wide) rainfall detection and rain rate retrieval. More precisely, we investigate if the combination of MWL with Meteosat Second Generation (MSG) satellite signals could improve rainfall detection and rainfall rate estimates. The investigated procedure includes an initial evaluation of the MWL rainfall estimates using gauge measurements, followed by a joint analysis of the rainfall estimates with the satellite signals by means of a conceptual model in which clouds with high cloud top optical thickness and large particle sizes have high rainfall probabilities and intensities. The analysis produced empirical thresholds that were used to test the capability of the MSG satellite data to detect rainfall on the MWL. The results from Kenya, during the “long rains” of 2013, 2014, and 2018 show convincing performance and reveal the potential of MWL and MSG data for area-wide rainfall detection.

Dudok de Wit Thierry, Bruinsma Sean

The 10.7 cm radio flux (F10.7) is widely used as a proxy for solar UV forcing of the upper atmosphere. However, radio emissions at other centimetric wavelengths have been routinely monitored since the 1950 s, thereby offering prospects for building proxies that may be better tailored to space weather needs. Here we advocate the 30 cm flux (F30) as a proxy that is more sensitive than F10.7 to longer wavelengths in the UV and show that it improves the response of the thermospheric density to solar forcing, as modelled with DTM (Drag Temperature Model). In particular, the model bias drops on average by 0–20% when replacing F10.7 by F30; it is also more stable (the standard deviation of the bias is 15–40% smaller) and the density variation at the the solar rotation period is reproduced with a 35–50% smaller error. We compare F30 to other solar proxies and discuss its assets and limitations.

Panagiota Galiatsatou, Christina Anagnostopoulou, Panayotis Prinos

In this study the generalized extreme value (GEV) distribution function was used to assess nonstationarity in annual maximum wave heights for selected locations in the Greek Seas, both in the present and future climates. The available significant wave height data were divided into groups corresponding to the present period (1951–2000), a first future period (2001–2050), and a second future period (2051–2100). For each time period, the parameters of the GEV distribution were specified as functions of time-varying covariates and estimated using the conditional density network (CDN). For each location and selected time period, a total number of 29 linear and nonlinear models were fitted to the wave data, for a given combination of covariates. The covariates used in the GEV-CDN models consisted of wind fields resulting from the Regional Climate Model version 3 (RegCM3) developed by the International Center for Theoretical Physics (ICTP) with a spatial resolution of 10 km × 10 km, after being processed using principal component analysis (PCA). The results obtained from the best fitted models in the present and future periods for each location were compared, revealing different patterns of relationships between wind components and extreme wave height quantiles in different parts of the Greek Seas and different periods. The analysis demonstrates an increase of extreme wave heights in the first future period as compared with the present period, causing a significant threat to Greek coastal areas in the North Aegean Sea and the Ionian Sea.

A. Vondráková, A. Vávra, V. Voženílek

Tao Che, Lin Xiao, Yuei-An Liou

Latest satellite images have been utilized to update the inventories of glaciers and glacial lakes in the Pumqu river basin, Xizang (Tibet), in the study. Compared to the inventories in 1970s, the areas of glaciers are reduced by 19.05% while the areas of glacial lakes are increased by 26.76%. The magnitudes of glacier retreat rate and glacial lake increase rate during the period of 2001–2013 are more significant than those for the period of the 1970s–2001. The accelerated changes in areas of the glaciers and glacial lakes, as well as the increasing temperature and rising variability of precipitation, have resulted in an increased risk of glacial lake outburst floods (GLOFs) in the Pumqu river basin. Integrated criteria were established to identify potentially dangerous glacial lakes based on a bibliometric analysis method. It is found, in total, 19 glacial lakes were identified as dangerous. Such finding suggests that there is an immediate need to conduct field surveys not only to validate the findings, but also to acquire information for further use in order to assure the welfare of the humans.

P. Jurus, K. Eben, J. Resler et al.

T. Dupont, M. Plu, P. Caroff et al.

Elena Ferrero, Marco Giardino, Francesca Lozar et al.

A geoethical approach to geodiversity allows better understanding of the value of abiotic nature and enhances its conservation and development. Our basic assumption is that even during an economical crisis, geoheritage sites can serve both public and private interests. A set of nine strategic geothematic areas were chosen to represent the geodiversity of the Piemonte region, north-western Italy, each of which is characterized by great potential for scientific studies, enhancement of public understanding of science, recreational activities, and economic support to the local communities. Specialized research teams individuated critical aspects to advance our knowledge of the geological history of the Piemonte region, through climate and environmental changes, natural hazards, soil processes, and georesources. The scientific concepts and techniques were coupled with geodiffusion actions and products: not only geosites, but also museum collections, evidence of mining and quarrying activities, science exhibitions, and nature trails. The preliminary results have allowed action plans to be developed with local partners, to assess the geoheritage management requirements. A series of investigations were carried out to improve the visual representation of the geological processes and the evolutionary scenarios. Further outcomes of the project will include didactic tools for educators, schools, and the public in general.<br />