scholarly journals Análise do Eixo Vertical de dois Ciclones Extratropicais na América do Sul

2021 ◽  
Vol 14 (1) ◽  
pp. 068
Author(s):  
Lanzoerques Gomes da Silva Júnior ◽  
André Becker Nunes
Keyword(s):  
Grid Point ◽  
Baroclinic Instability ◽  
Vertical Axis ◽  
Climate Forecast ◽  
Forecast System ◽  
Cyclonic Vorticity ◽  
Climate Forecast System ◽  
Atmospheric Research ◽  
Point Data ◽  
Period Of Occurrence

Ciclones extratropicais (CE) são sistemas de baixa pressão que ocorrem em latitudes médias (LM) ao longo do ano. São fenômenos vastamente estudados por serem normalmente associados à eventos de precipitação intensa, tempestades e grandes variações de temperatura. Os CEs são inicialmente identificados em superfície, contudo, também são observados até a tropopausa. Características como intensidade e tempo de vida podem estar relacionadas ao seu desenvolvimento em níveis superiores. Assim, este trabalho analisa por meio da estrutura vertical o ciclo de vida de dois CE, os quais se formaram em 31 de dezembro de 2012 e 12 de junho de 2014. Para isto foram utilizados dados em ponto de grade do Climate Forecast System Version 2/National Center for Atmospheric Research (CFSv2/NCAR). Ambos casos apresentaram: maior defasagem (diferença longitudinal entre o sistema em altos e baixos níveis devido à inclinação do seu eixo vertical para oeste) ao longo de seu desenvolvimento, similaridade no período de ocorrência e no menor valor da pressão central, assim como no aprofundamento do ciclone sendo superior a 24 hPa em 24 horas. No inverno (verão) o ciclone obteve maior (menor) defasagem e intensificou-se menos (mais), não sugerindo relação entre a inclinação do eixo vertical e a intensificação do ciclone. A inclinação na vertical para oeste foi mais (menos) acentuada no caso do inverno (verão), além de esboçar um comportamento menos (mais) retilíneo até ficar ocluso. Em ambos casos a vorticidade ciclônica esteve ligeiramente à leste do eixo vertical, estando mais próxima do mesmo no caso do verão.  Analysis of Vertical Axis of two Extratropical Cyclones in South America A B S T R A C TExtratropical cyclones (EC) are low pressure systems that occur in mid latitudes (ML) throughout the year. CEs are widely studied phenomena since they are usually associated to events of intense precipitation, storms and large variations of temperature. These systems are initially identified on surface, however, they are also observed up to tropopause. This work analyzes the vertical structure of the life cycle of two EC formed on December 2012 and June 2014. Grid point data (0.5 ° x 0.5 °) from the Climate Forecast System Version 2 / National Center for Atmospheric Research (CFSv2 / NCAR) were used to identify and obtain the longitudinal lag of the pressure centers on the surface and in high levels. Both cases presented: greater lag – longitudinal difference between upper and lower levels due to westward vertical tilt of the axis system – during their development, similarity in the period of occurrence and in the lowest value of central pressure, as well as in the deepening of the cyclone being greater than 24 hPa in 24 hours. In winter (summer) the cyclone obtained a larger (smaller) lag and intensified less (more), suggesting no relationship between the inclination of the vertical axis and the cyclone intensification. The westward vertical tilt was more (less) pronounced in winter (summer) case, besides presenting a behavior less (more) rectilinear until it is occluded. In both cases the most intense cyclonic vorticity was slightly east from vertical axis, being closer of the axis in summer case.Keywords: baroclinic instability; axis of the trough; vertical tilt. 

Dynamical prediction of the East Asian winter monsoon by the NCEP Climate Forecast System

2013 ◽  
Vol 118 (3) ◽  
pp. 1312-1328 ◽  
Author(s):  
Xingwen Jiang ◽  
Song Yang ◽  
Yueqing Li ◽  
Arun Kumar ◽  
Wanqiu Wang ◽  
...  
Keyword(s):  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Asian Winter Monsoon ◽  
Ncep Climate Forecast System

scholarly journals The German Climate Forecast System: GCFS

2020 ◽  
Author(s):  
Kristina Fröhlich ◽  
Mikhail Dobrynin ◽  
Katharina Isensee ◽  
Claudia Gessner ◽  
Andreas Paxian ◽  
...  
Keyword(s):  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System

scholarly journals Reanalysis intercomparisons of stratospheric polar processing diagnostics

2018 ◽  
Vol 18 (18) ◽  
pp. 13547-13579 ◽  
Author(s):  
Zachary D. Lawrence ◽  
Gloria L. Manney ◽  
Krzysztof Wargan
Keyword(s):  
Interannual Variability ◽  
Winter Season ◽  
Polar Vortex ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Stratospheric Polar Vortex ◽  
Scientific Results ◽  
Environmental Prediction ◽  
Low Sensitivity

Abstract. We compare herein polar processing diagnostics derived from the four most recent “full-input” reanalysis datasets: the National Centers for Environmental Prediction Climate Forecast System Reanalysis/Climate Forecast System, version 2 (CFSR/CFSv2), the European Centre for Medium-Range Weather Forecasts Interim (ERA-Interim) reanalysis, the Japanese Meteorological Agency's 55-year (JRA-55) reanalysis, and the National Aeronautics and Space Administration (NASA) Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2). We focus on diagnostics based on temperatures and potential vorticity (PV) in the lower-to-middle stratosphere that are related to formation of polar stratospheric clouds (PSCs), chlorine activation, and the strength, size, and longevity of the stratospheric polar vortex. Polar minimum temperatures (Tmin) and the area of regions having temperatures below PSC formation thresholds (APSC) show large persistent differences between the reanalyses, especially in the Southern Hemisphere (SH), for years prior to 1999. Average absolute differences of the reanalyses from the reanalysis ensemble mean (REM) in Tmin are as large as 3 K at some levels in the SH (1.5 K in the Northern Hemisphere – NH), and absolute differences of reanalysis APSC from the REM up to 1.5 % of a hemisphere (0.75 % of a hemisphere in the NH). After 1999, the reanalyses converge toward better agreement in both hemispheres, dramatically so in the SH: average Tmin differences from the REM are generally less than 1 K in both hemispheres, and average APSC differences less than 0.3 % of a hemisphere. The comparisons of diagnostics based on isentropic PV for assessing polar vortex characteristics, including maximum PV gradients (MPVGs) and the area of the vortex in sunlight (or sunlit vortex area, SVA), show more complex behavior: SH MPVGs showed convergence toward better agreement with the REM after 1999, while NH MPVGs differences remained largely constant over time; differences in SVA remained relatively constant in both hemispheres. While the average differences from the REM are generally small for these vortex diagnostics, understanding such differences among the reanalyses is complicated by the need to use different methods to obtain vertically resolved PV for the different reanalyses. We also evaluated other winter season summary diagnostics, including the winter mean volume of air below PSC thresholds, and vortex decay dates. For the volume of air below PSC thresholds, the reanalyses generally agree best in the SH, where relatively small interannual variability has led to many winter seasons with similar polar processing potential and duration, and thus low sensitivity to differences in meteorological conditions among the reanalyses. In contrast, the large interannual variability of NH winters has given rise to many seasons with marginal conditions that are more sensitive to reanalysis differences. For vortex decay dates, larger differences are seen in the SH than in the NH; in general, the differences in decay dates among the reanalyses follow from persistent differences in their vortex areas. Our results indicate that the transition from the reanalyses assimilating Tiros Operational Vertical Sounder (TOVS) data to advanced TOVS and other data around 1998–2000 resulted in a profound improvement in the agreement of the temperature diagnostics presented (especially in the SH) and to a lesser extent the agreement of the vortex diagnostics. We present several recommendations for using reanalyses in polar processing studies, particularly related to the sensitivity to changes in data inputs and assimilation. Because of these sensitivities, we urge great caution for studies aiming to assess trends derived from reanalysis temperatures. We also argue that one of the best ways to assess the sensitivity of scientific results on polar processing is to use multiple reanalysis datasets.

Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system

2013 ◽  
Vol 42 (7-8) ◽  
pp. 1925-1947 ◽  
Author(s):  
J. S. Chowdary ◽  
H. S. Chaudhari ◽  
C. Gnanaseelan ◽  
Anant Parekh ◽  
A. Suryachandra Rao ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Tropical Indian Ocean ◽  
Monsoon Circulation ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Ncep Climate Forecast System

scholarly journals A Hybrid Global Ocean Data Assimilation System at NCEP

2015 ◽  
Vol 143 (11) ◽  
pp. 4660-4677 ◽  
Author(s):  
Stephen G. Penny ◽  
David W. Behringer ◽  
James A. Carton ◽  
Eugenia Kalnay
Keyword(s):  
Data Assimilation ◽  
Initial Conditions ◽  
Global Ocean ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Ocean Data Assimilation ◽  
Data Assimilation System ◽  
Ncep Climate Forecast System ◽  
Assimilation System

Abstract Seasonal forecasting with a coupled model requires accurate initial conditions for the ocean. A hybrid data assimilation has been implemented within the National Centers for Environmental Prediction (NCEP) Global Ocean Data Assimilation System (GODAS) as a future replacement of the operational three-dimensional variational data assimilation (3DVar) method. This Hybrid-GODAS provides improved representation of model uncertainties by using a combination of dynamic and static background error covariances, and by using an ensemble forced by different realizations of atmospheric surface conditions. An observing system simulation experiment (OSSE) is presented spanning January 1991 to January 1999, with a bias imposed on the surface forcing conditions to emulate an imperfect model. The OSSE compares the 3DVar used by the NCEP Climate Forecast System (CFSv2) with the new hybrid, using simulated in situ ocean observations corresponding to those used for the NCEP Climate Forecast System Reanalysis (CFSR). The Hybrid-GODAS reduces errors for all prognostic model variables over the majority of the experiment duration, both globally and regionally. Compared to an ensemble Kalman filter (EnKF) used alone, the hybrid further reduces errors in the tropical Pacific. The hybrid eliminates growth in biases of temperature and salinity present in the EnKF and 3DVar, respectively. A preliminary reanalysis using real data shows that reductions in errors and biases are qualitatively similar to the results from the OSSE. The Hybrid-GODAS is currently being implemented as the ocean component in a prototype next-generation CFSv3, and will be used in studies by the Climate Prediction Center to evaluate impacts on ENSO prediction.

scholarly journals Do CFSv2 Seasonal Forecasts Help Improve the Forecast of Meteorological Drought over Mainland China?

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2010
Author(s):  
Yang Lang ◽  
Lifeng Luo ◽  
Aizhong Ye ◽  
Qingyun Duan
Keyword(s):  
Mainland China ◽  
Meteorological Drought ◽  
Lead Times ◽  
Climate Forecast ◽  
Seasonal Forecasts ◽  
Dynamical Models ◽  
Standard Precipitation Index ◽  
Forecast System ◽  
Climate Forecast System ◽  
Drought Prediction

Seasonal forecasts from dynamical models are expected to be useful for drought predictions in many regions. This study investigated the usefulness of the Climate Forecast System version 2 (CFSv2) in improving meteorological drought prediction in China based on its 25-year reforecast. The six-month standard precipitation index (SPI6) was used as the drought indicator, and its persistence forecast served as the benchmark against which CFSv2 forecasts were evaluated. The analysis found that the SPI6 persistence forecast shows good skills in all regions at short lead times, and CFSv2 forecast can further improve those skills in most regions. The improvement is particularly pronounced at longer lead times and over the humid regions in the southeast. This study also examined the seasonality and regionality of persistence forecast skills and CFSv2 contributions, and reveals regions where CFSv2 forecast shows no or sometimes even negative contributions.

Climatic characteristics of drift ice in the northern Barents Sea

2019 ◽  
Vol 11 (3) ◽  
pp. 800-811
Author(s):  
Chenglin Duan ◽  
Sheng Dong ◽  
Zhifeng Wang ◽  
Zhenkun Liao
Keyword(s):  
Barents Sea ◽  
Ice Thickness ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Ice Velocity ◽  
Environmental Prediction ◽  
Climatic Characteristics

Abstract In this paper, a preliminary climatic description of the long-term offshore drift ice characteristics in the northern Barents Sea has been investigated from 1987 to 2016 based on the satellite ice motion datasets from National Snow and Ice Data Center (NSIDC) and reanalysis ice thickness datasets from National Centers for Environmental Prediction (NCEP)-Climate Forecast System Reanalysis (CFSR) and Climate Forecast System Version 2 (CFSv2). Both the ice velocity and thickness conditions have been studied at the three fixed locations from west to east. Annual and monthly drift ice roses indicate that the directions from WSW to SE are primarily prevailing, particularly in winter months. Besides, the annual ice speed extremums exceeding 40 cm s–1 mostly occur in the southerly directions from November to April. For the ice thickness, results reveal that it is prominently distributed in a thicker interval between 70 and 120 cm, and a thinner interval between 20 and 70 cm. The annual thickness maxima approximately range from 90 to 170 cm, primarily occurring from May to June, and demonstrate a light decreasing trend.

Sign in / Sign up

Export Citation Format

Share Document