Archetypal analysis of Southern Hemisphere extreme circulation events

2020 ◽  
Author(s):  
James Risbey ◽  
Didier Monselesan
Keyword(s):  
Principal Component Analysis ◽  
Southern Hemisphere ◽  
Principal Component ◽  
Temperature Extremes ◽  
Archetypal Analysis ◽  
Long Period ◽  
Circulation Types ◽  
Circulation Patterns ◽  
Extreme Flow ◽  
Flow States

<p>Archetypal analysis of Southern Hemisphere extreme circulation events</p><p>This work conducts an archetypal analysis (AA) of midtropospheric flow<br>in the Southern Hemisphere.  The analysis identifies the archetypical<br>extreme flow states and compares them with the leading modes of<br>variability from Principal Component Analysis (PCA) methods.  In<br>particular, we examine long-lived extreme circulation patterns and<br>events from both AA and PCA, together with their synoptic signatures<br>and surface impacts.  The long-lived circulation types are efficient at<br>generating surface temperature extremes and exhibit long period<br>variability.  Case studies of documented surface extreme events show<br>that they correspond clearly to the midtropospheric flow archetypes.</p><p> </p>

scholarly journals Relationships of surface air temperature anomalies over Europe to persistence of atmospheric circulation patterns conducive to heat waves

2008 ◽  
Vol 14 ◽  
pp. 243-249 ◽  
Author(s):  
J. Kyselý ◽  
R. Huth
Keyword(s):  
Atmospheric Circulation ◽  
Air Temperature ◽  
Heat Waves ◽  
Temperature Extremes ◽  
Human Society ◽  
Positive Temperature ◽  
Temperature Anomalies ◽  
Circulation Types ◽  
Circulation Patterns ◽  
Air Temperature Anomalies

Abstract. Heat waves are among natural hazards with the most severe consequences for human society, including pronounced mortality impacts in mid-latitudes. Recent studies have hypothesized that the enhanced persistence of atmospheric circulation may affect surface climatic extremes, mainly the frequency and severity of heat waves. In this paper we examine relationships between the persistence of the Hess-Brezowsky circulation types conducive to summer heat waves and air temperature anomalies at stations over most of the European continent. We also evaluate differences between temperature anomalies during late and early stages of warm circulation types in all seasons. Results show that more persistent circulation patterns tend to enhance the severity of heat waves and support more pronounced temperature anomalies. Recent sharply rising trends in positive temperature extremes over Europe may be related to the greater persistence of the circulation types, and if similar changes towards enhanced persistence affect other mid-latitudinal regions, analogous consequences and implications for temperature extremes may be expected.

scholarly journals On the fuzziness of circulation types derived from the application of obliquely rotated principal component analysis to a T-mode climatic field

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
Principal Component Analysis ◽  
Frequency Distribution ◽  
Principal Component ◽  
Component Analysis ◽  
Threshold Values ◽  
Study Region ◽  
Probability Of Occurrence ◽  
Circulation Types ◽  
Mean Shape ◽  
The Mean

Abstract This study examined the separability of circulation types (CTs) classified from the application of principal component analysis (PCA) to the T-mode matrix (variable is time series and observation is grid points) of a climatic field that explains atmospheric circulation; in addition to the uncertainty introduced on (i) the probability of occurrence, (ii) the mean shape of the CTs, (iii) the trend in the annual frequency of occurrence, (iv) the frequency distribution of the CTs, by using varying threshold values within the range of 0.2–0.35 to assign days to a given CT. The study region is Africa, south of the equator. Some large clusters were classified with most days in the analysis period assigned to them; these classes are interpreted as the dominant states of the atmosphere and generally, their existence results in the poor separability of the CTs since their features overlap with other CTs. Qualitatively, the choice of the threshold values within the defined range has little or no influence on the overall structure of the probability of occurrence of the CTs, the mean shape of the CTs, and the year-to-year variations in the annual occurrence of the CTs. However, it significantly impacts the frequency distribution of the CTs and the statistical significance of the trend in the annual occurrence of the CTs. Stringent threshold values within the defined range might benefit studies that aim to isolate days when specific CTs are most expressed and analyze their mechanism using composite maps, without focus on the frequency distribution and annual occurrence of the CTs. Overall, for the study region, lower threshold values within the defined range might be recommended since relatively, they do not tend to further constrain the probability of group membership, and equally seem to reveal the mechanisms that might be consistent when a given CT occurred regardless of the strength of its signal at a given time.

Synoptic Circulation Patterns and Climate Regionalization of East Africa

2020 ◽  
Author(s):  
Markos Ware ◽  
Paolo Mori ◽  
Kisten Warrach -Sagi ◽  
Mark Jury ◽  
Thomas Schiwtalla ◽  
...  
Keyword(s):  
East Africa ◽  
Principal Component ◽  
Domain Size ◽  
Optimal Number ◽  
Final Decision ◽  
Test Technique ◽  
Circulation Types ◽  
Circulation Patterns ◽  
Climate Regionalization

<p><strong>Abstract</strong>. Climate regionalization is crucial for climate studies, especially in the case of heterogeneous regions like East Africa. This paper focuses on categorizing Ethiopia into homogeneous climatic sub-regions by applying a classification of circulation patterns on precipitation. The sub-regions obtained will be applied on the verification of WRF-NOAHMP seasonal simulations performed over the Horn of Africa. We analyzed the occurrence of each circulation type per month and per year over the whole country. Then, trend analysis of temperature and precipitation over the respective sub-regions were performed. Principal Component Analysis (PCA) were applied to group daily mean Sea Level Pressure (SLP) into Circulation Types (CTs). Then, PCA coupled with k-means clustering employed to regionalize precipitation fields (distributed spatially) following CTs into homogeneous climatic sub-regions. Observational data were obtained from the National Center for Environmental Prediction (NCEP) reanalysis, Climate Hazards Group Infrared Precipitation with Stations (CHIRPS version 2), and National Meteorology Agency (NMA) of Ethiopia (gauge 1st and 2nd classes). Five principal components, which explain 98% of the total variance, were maintained using the Scree test technique. Ten CTs were obtained using positive and negative phases of each principal component scores following the extreme score values (> 2 and < −2) procedure. From ten CTs, we found that three (CT1, CT3, and CT8) were characterized by low pressure over the southwest corner of the domain, which consequently brings rainfall over the Ethiopian highlands. The number of days classified under different CTs shows different trends. CTs seasonal distribution agreed with the regional seasons. Long-term monthly mean rainfall ranges from 0-600 mm over the region. Ethiopia is clustered into four homogeneous sub-regions based on the spatial distribution of precipitation following CTs. Rainfall from CHIRPS and gauge did not have any specific trend over the sub-regions, however high standardized anomalies were observed compared to the long term mean. The temperature showed a 2 °C change for the past three decades. There was a negligible difference in the shape, size, and location of regions using data from different sources. The final decision on the optimal number of homogeneous climatic sub-regions depends upon the research objective, geographical domain size, and topographic features of the domain. This study provides an assessment and decision pathway.</p><p> </p><p><strong>Keywords: </strong>climatology, regionalization, Ethiopia, precipitation, k-means, circulation types</p>

The applicability of principal component analysis to the separation of multiple plane-wave signals

1975 ◽  
Vol 65 (3) ◽  
pp. 627-635
Author(s):  
Z. A. Der ◽  
E. A. Flinn
Keyword(s):  
Principal Component Analysis ◽  
Plane Wave ◽  
Principal Component ◽  
Component Analysis ◽  
Eigenvalue Decomposition ◽  
Long Period ◽  
Multiple Plane

abstract It is shown that principal component analysis (eigenvector-eigenvalue decomposition of array spectral matrices) can be used for the approximate separation of superposed plane-wave signals only if at least one of the following conditions is satisfied: Application of the method for such cases is demonstrated on composited long-period seismograms using recordings from the D ring and center element of ASA.

scholarly journals Can synoptic patterns influence the track and formation of tropical cyclones in the Mozambique Channel?

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Principal Component ◽  
Large Scale Circulation ◽  
Modes Of Variability ◽  
Mozambique Channel ◽  
Circulation Types ◽  
Mascarene High ◽  
Circulation Patterns ◽  
Grid Points

Abstract The influence of large-scale circulation patterns on the track and formation of tropical cyclones (TCs) in the Mozambique Channel is investigated in this paper. The output of the hourly classification of circulation types (CTs), in Africa, south of the equator, using rotated principal component analysis on the T-mode matrix (variable is time series and observation is grid points) of sea level pressure (SLP) from ERA5 reanalysis from 2010 to 2019 was used to investigate the time development of the CTs at a sub-daily scale. The result showed that at specific seasons, certain CTs can persist for a longer time so that their features overlap with other CTs. CTs with synoptic features favorable for the development of TC in the Mozambique Channel were noted. The 2019 TC season in the Mozambique Channel characterized by TC Idai in March and TC Kenneth afterward in April was used in evaluating how the CTs designated to have TC characteristics played role in the formation and track of the TCs towards their maximum intensity. The results were discussed and it generally showed that large-scale circulation patterns might influence the formation and track of the TCs in the Mozambique Channel especially through the different modes of variability associated with the western branch of the Mascarene high.

scholarly journals Can synoptic patterns influence the track and formation of tropical cyclones in the Mozambique Channel?

2022 ◽  
Vol 8 (1) ◽  
pp. 33-51
Author(s):  
Chibuike Chiedozie Ibebuchi ◽  
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Principal Component ◽  
Precipitable Water ◽  
Cyclonic Activity ◽  
Large Scale Circulation ◽  
Mozambique Channel ◽  
Circulation Types ◽  
Mascarene High ◽  
Circulation Patterns

<abstract> <p>The influence of large-scale circulation patterns on the track and formation of tropical cyclones (TCs) in the Mozambique Channel is investigated in this paper. The output of the hourly classification of circulation types (CTs), in Africa, south of the equator, using rotated principal component analysis on the T-mode matrix (variable is time series and observation is grid points) of sea level pressure (SLP) from ERA5 reanalysis from 2010 to 2019 was used to investigate the time development of the CTs at a sub-daily scale. The result showed that at specific seasons, certain CTs are dominant so that their features overlap with other CTs. CTs with synoptic features, such as enhanced precipitable water and cyclonic activity in the Mozambique Channel that can be favorable for the development of TC in the Channel were noted. The 2019 TC season in the Mozambique Channel characterized by TC Idai in March and TC Kenneth afterward in April were used in evaluating how the CTs designated to have TC characteristics played role in the formation and track of the TCs towards their maximum intensity. The results were discussed and it generally showed that large-scale circulation patterns can influence the formation and track of the TCs in the Mozambique Channel especially through (ⅰ) variations in the position and strength of the anticyclonic circulation at the western branch of the Mascarene high; (ⅱ) modulation of wind speed and wind direction; hence influencing convergence in the Channel; (ⅲ) and modulation of the intensity of cyclonic activity in the Channel that can influence large-scale convection.</p> </abstract>

scholarly journals Climatic impact on atmospheric turbidity at some Indian stations

MAUSAM ◽  
2021 ◽  
Vol 48 (1) ◽  
pp. 33-40
Author(s):  
DEVENDRA SINGH ◽  
B. MUKHOPADHYAY ◽  
H. N. SRIVASTAVA
Keyword(s):  
Principal Component Analysis ◽  
Climatic Factors ◽  
Principal Component ◽  
Surface Fluxes ◽  
Climatic Impact ◽  
Annual Cycles ◽  
Climatic Regions ◽  
Long Period ◽  
Atmospheric Turbidity ◽  
Period Variations

Data from four Indian BAPMoN stations in different climatic regions were analysed using principal component analysis (PCA) for the evaluation of climatic impact upon turbidity.  Spectral analysis (FFT) of the data for these stations has helped to bring out the sub-seasonal, seasonal and annual cycles. It is found that the atmospheric turbidity is predominantly controlled by climatic factors through surface fluxes, transport of dust or rain washout and is mainly a lower tropospheric phenomenon. The performance of the PCA regression model is found satisfactorily in reproducing the annual cycle and long period variations.    

Scanning x-ray fluorescence microscopy and principal component analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1752-1753
Author(s):  
Brian Cross
Keyword(s):  
Principal Component Analysis ◽  
Fluorescence Microscopy ◽  
Spatial Resolution ◽  
High Speed ◽  
Image Acquisition ◽  
Principal Component ◽  
Fluorescence Microscope ◽  
Acquisition Rate ◽  
X Ray ◽  
Speed Up

A relatively new entry, in the field of microscopy, is the Scanning X-Ray Fluorescence Microscope (SXRFM). Using this type of instrument (e.g. Kevex Omicron X-ray Microprobe), one can obtain multiple elemental x-ray images, from the analysis of materials which show heterogeneity. The SXRFM obtains images by collimating an x-ray beam (e.g. 100 μm diameter), and then scanning the sample with a high-speed x-y stage. To speed up the image acquisition, data is acquired "on-the-fly" by slew-scanning the stage along the x-axis, like a TV or SEM scan. To reduce the overhead from "fly-back," the images can be acquired by bi-directional scanning of the x-axis. This results in very little overhead with the re-positioning of the sample stage. The image acquisition rate is dominated by the x-ray acquisition rate. Therefore, the total x-ray image acquisition rate, using the SXRFM, is very comparable to an SEM. Although the x-ray spatial resolution of the SXRFM is worse than an SEM (say 100 vs. 2 μm), there are several other advantages.

A German version of the Intermittent Claudication Questionnaire (ICQ): cultural adaptation and validation

VASA ◽  
2012 ◽  
Vol 41 (5) ◽  
pp. 333-342 ◽  
Author(s):  
Kirchberger ◽  
Finger ◽  
Müller-Bühl
Keyword(s):  
Principal Component Analysis ◽  
Intermittent Claudication ◽  
Completion Time ◽  
Short Form ◽  
Principal Component ◽  
Component Analysis ◽  
German Version ◽  
Average Completion Time ◽  
Sf 36 ◽  
Related Quality

Background: The Intermittent Claudication Questionnaire (ICQ) is a short questionnaire for the assessment of health-related quality of life (HRQOL) in patients with intermittent claudication (IC). The objective of this study was to translate the ICQ into German and to investigate the psychometric properties of the German ICQ version in patients with IC. Patients and methods: The original English version was translated using a forward-backward method. The resulting German version was reviewed by the author of the original version and an experienced clinician. Finally, it was tested for clarity with 5 German patients with IC. A sample of 81 patients were administered the German ICQ. The sample consisted of 58.0 % male patients with a median age of 71 years and a median IC duration of 36 months. Test of feasibility included completeness of questionnaires, completion time, and ratings of clarity, length and relevance. Reliability was assessed through a retest in 13 patients at 14 days, and analysis of Cronbach’s alpha for internal consistency. Construct validity was investigated using principal component analysis. Concurrent validity was assessed by correlating the ICQ scores with the Short Form 36 Health Survey (SF-36) as well as clinical measures. Results: The ICQ was completely filled in by 73 subjects (90.1 %) with an average completion time of 6.3 minutes. Cronbach’s alpha coefficient reached 0.75. Intra-class correlation for test-retest reliability was r = 0.88. Principal component analysis resulted in a 3 factor solution. The first factor explained 51.5 of the total variation and all items had loadings of at least 0.65 on it. The ICQ was significantly associated with the SF-36 and treadmill-walking distances whereas no association was found for resting ABPI. Conclusions: The German version of the ICQ demonstrated good feasibility, satisfactory reliability and good validity. Responsiveness should be investigated in further validation studies.

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