This study applies the maximum temperatures at more than 2000 Chinese stations to investigate the dominant modes of China summer heat waves (HWs). The first empirical orthogonal function (E...

/pdf/dominant-modes-of-china-summer-heat-waves-driven-by-global-9zfiigdtz2.pdf

Dominant Modes of China Summer Heat Waves Driven by Global Sea Surface Temperature and Atmospheric Internal Variability

Occurrence of heat and cold waves in Poland in the years 1966–2015 (1966/1967–2015/2016) was described, and their circulation conditions were determined in this study. A heat wave is defined as a period of at least 3 days with Tmax > 30.0 °C and a cold wave as a period of at least 3 days with Tmax <− 10.0 °C. Heat waves occurred most often in central and southern Poland and cold waves in north-eastern Poland. The occurrence of both heat and cold waves is related to high pressure systems. Anticyclonic blocking patterns both in winter and summer inhibit the zonal flow of air masses and intensify the meridional flow. Positive sea level pressure anomalies occurred over the study area, in the case of heat waves up to 3 hPa and in the case of cold waves up to 11 hPa. Perpendicular profiles showing geopotential height and air temperature anomalies in the troposphere were identified for the selected cases of extreme temperature episodes. Centres of geopotential height positive/negative anomalies were detected at the level of 300–250 hPa geopotential height, right over the area of the positive/negative surface temperature extremes.

/pdf/strong-heat-and-cold-waves-in-poland-in-relation-with-the-5grd94rpcl.pdf

Strong heat and cold waves in Poland in relation with the large-scale atmospheric circulation

The aim of the article was to provide a detailed analysis of pressure conditions, employing the anomalies of geopotential heights, during the occurrence of heat waves in Central Europe, but also in the days preceding and following their occurrence. The study uses data from 1966 to 2015 from the Institute of Meteorology and Water Management—National Research Institute, Deutscher Wetterdienst and the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR). A heat wave was defined as a sequence of at least 3 days with a maximum daily air temperature of >30°C. The study showed an increase in the number of hot days, which was statistically significant in the majority of the area. In the analysed years, an increasing number of heat waves were recorded, and this occurrence was associated with high pressure systems. Anticyclonic blocking in the summer inhibits the zonal flow of air masses and intensifies meridional flow, which in Central Europe in the summer means the presence of polar continental and tropical air masses. During heat waves, there were positive anomalies of isobaric surface heights over the study area with a maximum in the upper troposphere. On average, anomalies at the 300 hPa pressure level began to form over the Atlantic Ocean. Determining atmospheric preconditions of persisting blocking events in summer resulting in heat waves may be helpful in predicting thereof.

Heat waves in Central Europe and tropospheric anomalies of temperature and geopotential heights

Two anomaly-based fields, raw anomaly (RA) and normalized anomaly (NA), have been proven to be useful to indicate different aspects of weather extremes compared to conventional total fields. Based on the previous studies and a case analysis of the Beijing extreme rainfall on July 21, 2012, several unique features of the anomaly-based fields such as maximum height anomaly, positive humidity anomalous axes and zero temperature anomaly isoline are derived to indicate the extreme rain event effectively. Furthermore, complementary roles of the anomaly-based fields are summarized: RA fields can enlarge signals of an anomalous weather system with a clear structure, while NA fields can be used to quantitatively measure the degree of rarity or abnormality of a high-impact weather event. After a comparison between RA and NA variables, a comprehensive approach which combines these two types of anomalies is proposed to improve the extreme weather prediction using the ECMWF model output data. The results show that, for this Beijing extreme rainfall case, the proposed approach made a successful forecast with 156-h lead-time, which is 72 h earlier than the model precipitation forecast. Thus, anomaly-based fields are useful for forecasters to identify severe weather event warnings in practice.

A comprehensive approach from the raw and normalized anomalies to the analysis and prediction of the Beijing extreme rainfall on July 21, 2012

In the summer of 2010, western Russia experienced extreme heat, which was noted for its exceptional spatial spread, long duration, high intensity and impacts. We use an anomaly-based approach to decompose atmospheric variables into daily climatic components and anomalies from two reanalysis datasets. We show that a surface heat wave event results from a downward extension of an anomalously warm air column below a centre of positive geopotential height anomalies in the upper troposphere. Therefore, we use this approach to analyse all summer regional heat wave events with spatial scales larger than 2000 km and durations greater than 5 days over western Eurasia from 1980 to 2014. Our results demonstrate that the rapid increase in regional heat wave events over western Eurasia since 2010 is a direct response to the increasing frequency of large-scale, quasi-stationary positive centres of maximum height anomalies in the upper troposphere.

Three-dimensional structure and long-term trend of heat wave events in western Eurasia revealed with an anomaly-based approach

Comparisons between CMIP5 and CMIP6 models in simulations of the climatology and interannual variability of the east asian summer Monsoon

For the grasping task of the deep-sea hydraulic manipulator, it is necessary to carry out kinematic analysis and point-to-point joint motion planning. To reduce the influence of the structural error of the manipulator caused by manufacturing, assembly, transportation, environment, and other factors on the kinematics parameters of the manipulator, RBF neural network is used to identify the kinematics model parameters of the manipulator to obtain more accurate modified D-H parameters. Based on this model and flow constraints, the PSO algorithm is used to plan the joint space trajectory of the deep-sea hydraulic manipulator. The experimental results show that the method can well meet the needs of joint-space planning of the deep-sea hydraulic manipulator that is subjected to flow constraints and lay a foundation for subsequent complex tasks.

Trajectory Planning of Deep-Sea Hydraulic Manipulator in Joint Space with Flow Constraints

The summertime North Indian Ocean (NIO) and tropical North Atlantic (TNA) sea surface temperature (SST) anomalies exert important impacts on atmospheric circulation and climate variation. Little attention is paid on the interdecadal change of NIO–TNA SST connection. This study reveals that the NIO–TNA SST relationship experiences an obvious interdecadal change around the early 2000s. The NIO and TNA SST correlation is positive and significant before the early 2000s, while this connection becomes weak and insignificant after that. This interdecadal change is closely associated with the changes in the El Niño‐Southern Oscillation (ENSO) intensity. During 1980–2001, strong ENSO forces a sustained SST warming in the southwest Indian Ocean, which further warms the summertime NIO via inducing antisymmetric circulation and reducing the upward surface latent heat flux. Meanwhile, strong ENSO forces a summertime TNA warming via arousing the Pacific North American (PNA) teleconnection. The PNA weakens the TNA trade winds, then reduces the upward surface heat flux and consequently warms the TNA. Thus, NIO and TNA SST connection is established via ENSO events during 1980–2001. In contrast, during 2002–2020, the summertime NIO SST anomaly is still related to ENSO. However, the connection between the TNA SST anomaly and ENSO is interrupted due to the weak ENSO intensity. Such weak ENSO yields a much weaker PNA teleconnection, which is inefficient to generate the TNA warming. Further analysis shows that the TNA warming during 2002–2020 is generated mainly by the negative North Atlantic Oscillation. Therefore, the connection between NIO and TNA SST anomalies collapses under the weak ENSO condition.

The Interdecadal Change of the Relationship Between North Indian Ocean SST and Tropical North Atlantic SST

Recent interdecadal changes in the Tropospheric Biennial Oscillation of the East Asian summer monsoon

For redundant manipulators with non-spherical wrists, we propose a general and computation-effective method of singularity avoidance. Firstly, the dimension of the Jacobian of the redundant manipulator is reduced by the elementary transformation method to obtain the singular factors. Secondly, we use the damped reciprocal method to solve the inverse kinematics solutions of the redundant manipulator. Thirdly, the singularities of the redundant manipulator are divided into non-escapable and escapable singularities, and the singular conditions are determined with the singular factors. Then taking the singularity avoidance as the secondary task of the control system, we propose a singular factor optimization method to avoid both types of singularities of the redundant manipulator. The complexity analysis shows that no need to calculate the pseudo-inverses or partial derivatives of the Jacobian, the proposed method has lower computational complexity. Finally, simulations have been made on the non-escapable and escapable singularities to verify the proposed methods.

A computationally effective singularity avoidance method for redundant manipulators with non-spherical wrists

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