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Squall lines often produce extremely disastrous gales and play a crucial role in the safety of hytropower stations.This article explores a squall line event over the lower reaches of Jinsha River on June 4， 2016， which brought 13-level wind at the canyon of Baihetan Hytropower Station.This research detect the formation mechanism of this squall line from environmental conditions and medium-scale meteorology.The following conclusions are obtained： （1） Before the squall line arrived， the ground pressure dropped steadily by 9 hPa because of the low pressure， and the temperature of the canyon rises up above 14 ℃.As the squall line arrived， the pressure rises sharply with thunderstorm high pressure， and the temperature dropped more than 10 ℃.At the same time， the relative humidity reached as higher as 70%， accompanied by short-term precipitation.After the squall line left， the aforementioned meteorological elements restored to their original values.（2） Analysis on the synoptic scale circulation， we finds that Baihetan hytropower station located in the south of southwest vortex， which induced a wind convergence background at the low level.Meanwhile， the station lied in right side of the jet stream inlet at upper level， and strong vertical motion formed by the wind shear.As a result， the squall line to come into being.Furthermore， in the troposphere before the squall line， the atmospheric circulation displayed a dry-cold advection in the middle-upper level superimposed over a warm-wet advection and higher ground temperature in the lower levels， increasing the temperature lapse rate.t As a result， the strong static instability and convection accumulated， and the conditions were favorable for the squall line to live a long time.The analyses from vertical wind speed showed that the subsidence movement made the momentum spread down， and promoted the uplift in the front side of line， and a positive feedback effect developed， promoting a stable mechanism for the strong storm.（3） Radar of Zhaotong detection indicates that echo cell that greater than 30 dBZ aggregated costly into a band and embed with the strong echo cores of greater than 50 dBZ， as a cylindrical convective cloud of higher than 10 km.On the radical velocity field， the meso-scale convergence line coinciding with the banded strong echo， as well as MARC （Mid-Altitude Radial Convergence） characteristics of the mid-altitude radial convergence， were the trigger mechanism for the squall line.As the cloud structure of the storm， strong upward movement in front of the squall line leaded to the dome.As the squall line arrived， the echo core dropped rapidly， and the extreme gale of downburst formed， resulted the new convective monomers come in being along the canyon.

Changes in the jet stream not only affect the persistence of climate change and the frequency of extreme weather but are also closely related to climate change phenomena such as global warming. The manual way of drawing the jet stream axes in meteorological operations suffers from low efficiency and subjectivity issues. Automatic identification algorithms based on wind field analysis have some shortcomings, such as poor generalization ability, and it is difficult to handle merging and splitting. A semi-supervised learning jet stream axis identification method is proposed combining consistency learning and self-training. First, a segmentation model is trained via semi-supervised learning. In semi-supervised learning, two neural networks with the same structure are initialized with different methods, based on which pseudo-labels are obtained. The high-confidence pseudo-labels are selected by adding perturbation into the feature layer, and the selected pseudo-labels are incorporated into the training set for further self-training. Then, the jet stream narrow regions are segmented via the trained segmentation model. Finally, the jet stream axes are obtained with the skeleton extraction method. This paper uses the semi-supervised jet stream axis identification method to learn features from unlabeled data to achieve a small amount of labeled data to effectively train the model and improve the method’s generalization ability in a small number of labeled cases. Experiments on the jet stream axis dataset show that the identification precision of the presented method on the test set exceeds about 78% for SOTA baselines, and the improved method exhibits better performance compared to the correlation network model and the semi-supervised method.

Precipitation decline in northern China since the mid-Holocene was probably driven by suppression of convective precipitation due to vegetation changes rather than by weakening of the East Asian summer monsoon, according to transient numerical experiments.

In this paper， the ability of CMIP6's 10 global climate models to simulate the historical climate change of Qilian Mountains is tested by using a variety of test parameters.We found that the CESM2-WACCM model has the best simulation effect on projection of climate variation in Qilian Mountains.Therefore， the variation characteristics of temperature， precipitation and humidity in Qilian Mountains from 2020 to 2064 are analyzed under three emission scenarios.They are low， medium and high emission scenario.The results are as follows： （1） In the next half century， the temperature at northern part of Qilian Mountains will be higher， lower at the southern part and higher at both ends， the possibility of heating up is high， the characteristics of warm winter are more obvious than that of warm summer.Comparing the future rise amplitude of Qilian Mountains temperature under different scenarios， it is found that under the high emission scenario， the temperature rises most significantly in winter and summer， while the rise amplitude of medium emission scenario is the lowest.（2） In the future， the precipitation in Qilian Mountains will increase in summer， and the possibility of "humidification" is relatively large.Especially under the scenario of high emission， the intensity of "humidification" is the highest in the eastern part of Qilian Mountains， and it is consistent with the water vapor convergence area shown by the divergence of water vapor flux.（3） The future water vapor variation in Qilian Mountains expressed by atmospheric specific humidity show that atmospheric humidity is more likely to increase in summer， and the variation in southern Qilian Mountains is obvious than that in Northern Qilian Mountains， especially in the scenario of high emission， the East will become more humid in the future， which is consistent with the increase of future precipitation in Qilian Mountains.

A convenient and fast multi-residue method for the efficient identification and quantification of 72 pesticides belonging to different chemical classes in red and white grape wines has been developed. The analysis was based on gas chromatography tandem quadrupole mass spectrometric determination (GC–MS/MS). The optimization strategy involved the selection of the amount of multi-walled carbon nanotubes (MWCNTs) and the number of cleanup procedure cycles for multi-plug filtration cleanup (m-PFC) to achieve ideal recoveries and reduce the sample matrix compounds in the final extracts. The optimized procedure obtained consistent recoveries between 70.2 and 108.8% (70.2 and 108.8% for white wine, and 72.3 and 108.4% for red wine), with relative standard deviations (RSDs) that were generally lower than 9.2% at the three spiking levels of 0.01, 0.05 and 0.1 mg/kg. The linearity was studied in the range between 0.002 and 0.1 mg/kg using pesticide standards prepared both in pure solvent and in the presence of the matrix, showing coefficients of determination (R2) higher than 0.9495 for all the pesticides. To improve accuracy, matrix-matched calibration curves were used for calculating the quantification results. Finally, the method was used successfully for detecting pesticide residues in commercial grape wines.

The residue levels of thiram during potato cultivation in open field were evaluated. Thiram residues were determined by methylation derivation method with high performance liquid chromatography (HPLC). Wettable powder (WP) formulation containing 25% thiram was applied at 2320 g active gradient hm−2 (a.i. hm−2) dosage for the dissipation study. The decline rate in potato leave and soil followed first-order kinetics equation, and the half-life ranged from 2.8 to 5.4 days and 2.6 to 9.9 days, respectively. In terminal residue, the thiram was sprayed at 580 g a.i. hm−2 (low concentration, recommended dosage) and 1160 g a.i. hm−2 (high concentration, double of recommended dosage). The residues of thiram in potato and soil samples collected in the field at preharvest interval of 21 days and 30 days were all below 0.02 mg kg−1. The results show that thiram possesses low dietary risk in potato at harvest according to supervised residue field trial. It may be safe when used at recommended rate of application.

Based on the meteorological and geological disaster data, ground observation data set, CLDAS grid point data set, and EC, B.l and other model product data during 2(X)8 -2020, the temporal and spatial distribution characteristics of meteorological and geological disasters and precipitation were analyzed, and the causes of the occurrence of meteorological geological disasters and the deviation of model precipitation forecast were revealed. Besides, an objective precipitation forecast system and a forecast and early warning system of meteorological and geological disasters were established. The results show that meteorological and geological disasters and precipitation were mainly concentrated from May to October, of which continuous precipitation appeared frequently in June and September, and convective precipitation was mainly distributed in July - August; the occurrence frequency of meteorological and geological disasters was basically consistent with the distribution of accumulated precipitation and short-term heavy precipitation, and they were mainly concentrated in the southern and eastern parts of Qinghai. Meteorological and geological disasters were basically caused by heavy rain and above, and meteorological and geological disasters were divided into three types; continuous precipitation (type I), short-term heavy precipitation (type II) and mixed precipitation (type III). For type I, the early warning conditions of meteorological and geological disasters in Qinghai are as follows; if the soil volumetric water content difference between 0-10 and 10 -40 cm is 0. 03 mm3/mm3, or the soil volumetric water content at one of the depths is 0.25 mm3/mm3, the future effective precipitation reaches 8.4 mm in 1 h, 10.2 mm in 2 h, 11.5 mm in 3 h, 14.2 mm in 6 h, 17.7 mm in 12 h, and 18.2 mm in 24 h, and such warning conditions are mainly used in Yushu, Guoluo, southern Hainan, southern Huangnan and other places. For type 11, when the future effective precipitation is up to 11.5 mm in 1 h, 14.9 mm in 2 h, 16.2 mm in 3 h, 19.9 mm in 6 h, 25.3 mm in 12 h, and 26.3 mm in 24 h, such precipitation thresholds are mainly used in Hainan, Huangnan, and eastern Guoluo; as it is up to 13.3 mm in 1 h, 15.5 mm in 2 h, 16.6 mm in 3 h, 19.9 mm in 6 h, 31. 1 mm in 12 h, and 34. 0 mm in 24 h, such precipitation thresholds are mainly used in Hehuang valley. The precipitation thresholds of type HI are between type I and type II, and closer to that of type II; such precipitation thresholds are mainly used in Hainan, Huangnan, and northern Guoluo. The forecasting ability of global models for heavy rain and above was not as good as that of mesascale numerical prediction model, and global models had a wet bias for small-scale precipitation and a dry bias for large-scale precipitation; meso-scale models had a significantly larger precipitation bias. The forecast ability of precipitation objective forecast system constructed by frequency matching and multi-model integration has improved. At the same time, the constructed grid forecast and early warning system of meteorological and geological disasters is more precise and accurate, and is of instructive significance for the forecast and early warning of meteorological and geological disasters. [ABSTRACT FROM AUTHOR]

Climatological features and variations of wet spells, especially their trends over China, are investigated using a dataset of 594 meteorological stations across China from 1951 to 2003. The results show that the lower the latitude is, the longer the annual duration of wet spells is. The mean annual precipitation from wet spells is higher in southeastern coastal areas and much lower in western and northern China. The longest wet spells are found in Southwest China and the eastern Tibetan Plateau. The maximum daily precipitation of wet spells decreases from the southeast to the northwest, with the highest in southeastern coastal areas and the lowest in western China. The trends of wet spells exhibit striking regional differences. In most areas of western China, the annual number of days in wet spells has slightly increased, but significantly decreased over North China, Central China and Southwest China. The annual precipitation amount from wet spells displays significant downward trends in North China, eastern Northeast China and the eastern part of Southwest China, but upward trends in the eastern Tibetan Plateau and some southeastern coastal areas. Two clearly-contrasting regions in climatic changes of wet spells are the mid-lower reaches of the Yellow River and the eastern Tibetan Plateau, characterized by a decrease of about 24 days and an increase of about 6 days in annual wet spell days from 1953 to 2003, respectively. [ABSTRACT FROM AUTHOR]

The article discusses a research study on the use of direct analysis in real time (DART) source with single-quadrupole mass spectrometry (MS) for detecting caffeine in instant coffee, tea and soft drink. Materials, chemicals and reagents used include caffeine standard, acetonitrile and supermarket-purchased instant coffee, tea and soft drink. Results showed rapid identification and detection of caffiene in different samples with the DART-MS in real-time analysis.