Modelling wildfire activity in Iberia with different atmospheric circulation weather types

2013 ◽  
Vol 36 (7) ◽  
pp. 2761-2778 ◽  
Author(s):  
Ricardo M. Trigo ◽  
Pedro M. Sousa ◽  
Mário G. Pereira ◽  
Domingo Rasilla ◽  
Célia M. Gouveia
Keyword(s):  
Atmospheric Circulation ◽  
Weather Types

scholarly journals Atmospheric circulation influence on the interannual variability of snow pack in the Spanish Pyrenees during the second half of the 20th century

2007 ◽  
Vol 38 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Juan I. López-Moreno ◽  
Sergio M. Vicente-Serrano
Keyword(s):  
Atmospheric Circulation ◽  
20Th Century ◽  
Large Scale ◽  
Spatial Scales ◽  
Cold Season ◽  
Snow Accumulation ◽  
Positive Trend ◽  
Snow Pack ◽  
Weather Types ◽  
Spanish Pyrenees

Large areas in the Spanish Pyrenees are covered by snow between December and April, especially above 1650 m a.s.l., the location of the cold season 0°C isotherm. However, a significant negative trend in Pyrenean snow pack was detected during the second half of the 20th century. This paper analyses the interannual evolution of snow accumulation in these mountains in relation to the variability of atmospheric circulation. The study considers two spatial scales, from weather types over the Iberian Peninsula to hemispheric atmospheric patterns. The results show strong relationships between the annual occurrence of several weather types and spring snow accumulation. Changes in the frequency of several weather types are explained by the evolution of large scale hemispheric circulation patterns, especially the North Atlantic Oscillation (NAO). Thus, the positive trend observed in the NAO index leads to a decrease in the occurrence of types that favour snow accumulation and an increase in unfavourable conditions for snow pack during the second half of the 20th century.

Transition probabilities between synoptic weather types as a fingerprint for climate model evaluation

2021 ◽  
Author(s):  
Juan Antonio Fernandez-Granja ◽  
Ana Casanueva ◽  
Joaquín Bedia ◽  
Jesús Fernández
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Transition Probabilities ◽  
Transition Probability ◽  
Transition Probability Matrix ◽  
Weather Types ◽  
Observational Uncertainty ◽  
Leibler Divergence ◽  
Synoptic Conditions ◽  
Large Scale Atmospheric Circulation

<p>Global Climate Models (GCMs) generally exhibit significant biases in the representation of large-scale atmospheric circulation. Even after bias adjustment, these errors remain and are inherited to some extent by the derived downscaling products, impairing the credibility of future regional projections. </p><p>We perform a process-based evaluation of state-of-the-art GCMs from CMIP5 and CMIP6, with a focus on the simulation of the synoptic climatological patterns having a most prominent effect on the European climate. To this aim, we use the Lamb Weather Type Classification (LWT, Lamb, 1972). We undertake a comprehensive assessment based on several evaluation measures, such as Kullback-Leibler divergence (KL), Relative Bias and Transition Probability Matrix Score (TPMS), used to assess the ability of the GCMs in reproducing not only the frequencies of the different Lamb Weather Types (LWTs), but also the daily probabilities of transitions among them. We show that the novel TPMS score poses a stringent test on the GCM performance, allowing for a convenient model ranking based on each model’s transition probability matrix fingerprint. Deficiencies in the transition probabilities from one LWT to another might explain the misrepresentation of the synoptic conditions and their frequencies by the GCMs. Four different reanalysis products of varying characteristics are considered as pseudo-observational reference in order to assess observational uncertainty. </p><p>Our results unveil an overall improvement of salient atmospheric circulation features of CMIP6 with respect to CMIP5, demonstrating the ability of the new models to better capture key synoptic conditions. The improvement is consistent across observational references, although it is uneven across models and large frequency biases still remain for the dominant LWTs in many cases. In particular, some CMIP6 models attain similar or even worse results than their CMIP5 counterparts. In light of the large differences found across models, we advocate for a careful selection of driving GCMs in downscaling experiments with a special focus on large-scale atmospheric circulation aspects.</p><p> </p>

scholarly journals Mapping Weather-Type Influence on Senegal Precipitation Based on a Spatial–Temporal Statistical Model*

2013 ◽  
Vol 26 (20) ◽  
pp. 8189-8209 ◽  
Author(s):  
Henning W. Rust ◽  
Mathieu Vrac ◽  
Benjamin Sultan ◽  
Matthieu Lengaigne
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Pearson Correlation ◽  
Precipitation Amount ◽  
Correlation Coefficients ◽  
Drought Risk ◽  
Synoptic Scale ◽  
Weather Types ◽  
Easterly Waves ◽  
Precipitation Occurrence

Abstract Senegal is particularly vulnerable to precipitation variability. To investigate the influence of large-scale circulation on local-scale precipitation, a full spatial–statistical description of precipitation occurrence and amount for Senegal is developed. These regression-type models have been built on the basis of daily records at 137 locations and were developed in two stages: (i) a baseline model describing the expected daily occurrence probability and precipitation amount as spatial fields from monsoon onset to offset, and (ii) the inclusion of weather types defined from the NCEP–NCAR reanalysis 850-hPa winds and 925-hPa relative humidity establishing the link to the synoptic-scale atmospheric circulation. During peak phase, the resulting types appear in two main cycles that can be linked to passing African easterly waves. The models allow the investigation of the spatial response of precipitation occurrence and amount to a discrete set of preferred states of the atmospheric circulation. As such, they can be used for drought risk mapping and the downscaling of climate change projections. Necessary choices, such as filtering and scaling of the atmospheric data (as well as the number of weather types to be used), have been made on the basis of the precipitation models' performance instead of relying on external criteria. It could be demonstrated that the inclusion of the synoptic-scale weather types lead to skill on the local and daily scale. On the interannual scale, the models for precipitation occurrence and amount capture 26% and 38% of the interannual spatially averaged variability, corresponding to Pearson correlation coefficients of rO = 0.52 and ri = 0.65, respectively.

scholarly journals Synoptic classification of atmospheric circulation over the south Eastern Siberia and its relationship with glacier dynamics

2021 ◽  
Author(s):  
Olga Osipova ◽  
Eduard Osipov
Keyword(s):  
Atmospheric Circulation ◽  
Lower Troposphere ◽  
Basic Research ◽  
Eastern Siberia ◽  
Weather Types ◽  
Synoptic Classification ◽  
South Eastern ◽  
Environmental Prediction ◽  
Autumn And Winter

<p>The energy balance of a glacial surface and its melting is strongly controlled by altering synoptic processes in the lower troposphere. Therefore, classification of the processes of atmospheric circulation over the glaciarized regions is very important for better understanding of long-term trends in glacier changes. The glaciers of the Kodar Ridge (south Eastern Siberia) have shrunk in area by about 60% since the mid-19th century, with the largest decline taking place at the end of the 20th century. We have compiled the daily catalog of the weather types (WTs) from 1970 to 2020 based on the Jenkinson and Collison objective classification applied for the area (47.5–67.5° N, 102.5–132.5° E) centered over the Kodar Ridge. The gridded sea level pressure (SLP) and isobaric 700 hPa data was obtained from the National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) reanalysis. In total, 26 WTs were identified and the frequency of different synoptic types was statistically analyzed. The most frequent group of WTs is advective (40%), followed by anticyclonic (34%) and cyclonic (14%). The unclassified type totally accounts for 13%. We revealed the differences between the frequency of synoptic processes in seasonal cycle and at different atmospheric levels (SLP and 700 hPa). Cyclonic weather types usually prevail in summer, while anticyclonic ones in autumn and winter. At 700 hPa level, the frequency of anticyclonic WTs increases in summer, while the frequency of advective types increases in all seasons. Over the past 50 years, the frequency of anticyclonic types demonstrates decreasing trend, while that of cyclonic and advective weather types increased (SLP data). In the 1980s and early 1990s the frequency of cyclonic WTs decreased, which could lead to a decrease in cloud cover over the Kodar region and an increase in net radiation of glacier surfaces. This study was supported by the Russian Foundation for Basic Research (project No. 19-05-00668).</p>

scholarly journals Identifying wildfire-prone atmospheric circulation weather types on mainland Spain

2019 ◽  
Vol 264 ◽  
pp. 92-103 ◽  
Author(s):  
Marcos Rodrigues ◽  
José Carlos González-Hidalgo ◽  
Dhais Peña-Angulo ◽  
Adrián Jiménez-Ruano
Keyword(s):  
Atmospheric Circulation ◽  
Weather Types

scholarly journals Weather Types in the Norwegian Arctic

2009 ◽  
Vol 2 (1) ◽  
pp. 107-120
Author(s):  
Andrzej Araźny
Keyword(s):  
Atmospheric Circulation ◽  
Outdoor Recreation ◽  
Human Life ◽  
Weather Conditions ◽  
Weather Types ◽  
Outdoor Activities ◽  
Circulation Types ◽  
Bioclimatic Conditions

Abstract In order to assess the usefulness of Norwegian Arctic bioclimatic conditions for outdoor activities in the years 1971-2000, the author applied his own weather typology developed on the basis of the classification proposed by Błażejczyk (1979). The typology classified four weather groups for the study area. Atmospheric circulation types proposed by Niedźwiedź (2002) were used to determine the synoptic situations and types of favourable weather conditions for outdoor recreation, tourism and work, as well as those that may pose a threat to human life.

Sign in / Sign up

Export Citation Format

Share Document