Investigation on Evolutive Laws of Geopotential Height of Two Poles and the Equator at 500hPa Geopotential Height Field

2007 ◽  
Vol 50 (1) ◽  
pp. 58-66 ◽  
Author(s):  
Guo-Qiong SONG ◽  
Hua-Sheng YAN ◽  
Su-Yu YANG ◽  
Wan-Biao LI
Keyword(s):  
Geopotential Height ◽  
Height Field ◽  
Geopotential Height Field

scholarly journals Probabilistic Forecasting of the 500 hPa Geopotential Height over the Northern Hemisphere Using TIGGE Multi-model Ensemble Forecasts

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 253
Author(s):  
Luying Ji ◽  
Qixiang Luo ◽  
Yan Ji ◽  
Xiefei Zhi
Keyword(s):  
Northern Hemisphere ◽  
Geopotential Height ◽  
Prediction Skill ◽  
Ensemble Prediction ◽  
Lead Times ◽  
Height Distribution ◽  
Height Field ◽  
Probabilistic Forecasting ◽  
Ensemble Forecasts ◽  
Geopotential Height Field

Bayesian model averaging (BMA) and ensemble model output statistics (EMOS) were used to improve the prediction skill of the 500 hPa geopotential height field over the northern hemisphere with lead times of 1–7 days based on ensemble forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and UK Met Office (UKMO) ensemble prediction systems. The performance of BMA and EMOS were compared with each other and with the raw ensembles and climatological forecasts from the perspective of both deterministic and probabilistic forecasting. The results show that the deterministic forecasts of the 500 hPa geopotential height distribution obtained from BMA and EMOS are more similar to the observed distribution than the raw ensembles, especially for the prediction of the western Pacific subtropical high. BMA and EMOS provide a better calibrated and sharper probability density function than the raw ensembles. They are also superior to the raw ensembles and climatological forecasts according to the Brier score and the Brier skill score. Comparisons between BMA and EMOS show that EMOS performs slightly better for lead times of 1–4 days, whereas BMA performs better for longer lead times. In general, BMA and EMOS both improve the prediction skill of the 500 hPa geopotential height field.

scholarly journals Identifying Weather Regimes in the Wintertime 500-hPa Geopotential Height Field for the Pacific–North American Sector Using a Limited-Contour Clustering Technique

2007 ◽  
Vol 46 (10) ◽  
pp. 1619-1630 ◽  
Author(s):  
Joseph H. Casola ◽  
John M. Wallace
Keyword(s):  
North American ◽  
Significant Relationship ◽  
Geopotential Height ◽  
Field Method ◽  
Contour Method ◽  
Regime Type ◽  
Height Field ◽  
Full Field ◽  
Geopotential Height Field ◽  
The Pacific

Abstract A hierarchical clustering algorithm using Ward’s method has been applied to the 500-hPa geopotential height field in the Pacific–North American sector. In contrast to previous clustering studies that measure distance between records by using all the grid points within the domain (full-field method), the procedure outlined here, referred to as the limited-contour method, focuses on the coordinates of the 540-dam contour as the distance measure. Comparison between the regimes emerging from the two methods shows that the limited-contour method is more efficient than the full-field method with respect to grouping maps with ridges located at similar longitudes. The four regimes emerging from the limited-contour clustering analysis have been named as follows: Off-Shore Trough, Alaskan Ridge, Coastal Ridge, and Rockies Ridge. The frequencies of occurrence of the regimes have a significant relationship with the phase of the El Niño–Southern Oscillation. El Niño winters exhibit a strong preference for the Rockies Ridge pattern; La Niña winters exhibit a greater diversity of regimes. The frequencies of occurrence of extreme cold outbreaks and episodes of heavy precipitation in the Pacific Northwest show a relatively strong connection to the regime type. For other regions in the western portion of the United States, only the frequency of occurrence of cold outbreaks exhibits a significant relationship to regime type.

scholarly journals Wintertime connections between extreme wind patterns in Spain and large-scale geopotential height field

2013 ◽  
Vol 122 ◽  
pp. 213-228 ◽  
Author(s):  
A. Pascual ◽  
M.L. Martín ◽  
F. Valero ◽  
M.Y. Luna ◽  
A. Morata
Keyword(s):  
Geopotential Height ◽  
Large Scale ◽  
Height Field ◽  
Geopotential Height Field ◽  
Extreme Wind ◽  
Wind Patterns

scholarly journals Seamless Detection of Cutoff Lows and Preexisting Troughs

2021 ◽  
Author(s):  
Satoru Kasuga ◽  
Meiji Honda ◽  
Jinro Ukita ◽  
Shozo Yamane ◽  
Hiroaki Kawase ◽  
...  
Keyword(s):  
Geopotential Height ◽  
Geometric Features ◽  
Height Field ◽  
Height Profile ◽  
Distribution Maps ◽  
Adverse Weather ◽  
Local Background ◽  
Cutoff Low ◽  
Torrential Rainfall ◽  
Height Fields

AbstractWe propose a new scheme based on geopotential height fields to detect cutoff lows starting in the preexisting trough stage. The intensity and scale derived from the proposed scheme will allow for a better understanding of the cutoff low life cycle. These cutoff lows often accompany mesoscale disturbances, causing adverse weather-related events, such as intense torrential rainfall and/or tornadoes. The proposed scheme quantifies the geometric features of a depression from its horizontal height profile. The height slope of a line intersecting the depression bottom and the nearest tangential point (optimal slope) locally indicates the intensity and scale of an isolated depression.The strength of the proposed scheme is that, by removing a local background height slope from a geopotential height field, the cutoff low and its preexisting trough are seamlessly detected as an identical depression. The distribution maps for the detected cutoff lows and preexisting troughs are illustrated along with their intensities, sizes, and local background flows estimated from snapshot height fields. We conducted climatological comparisons of cutoff lows to determine the utility of the proposed scheme.

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