Atmospheric Circulation Research Papers - Academia.edu (original) (raw)
Generally, the severe weather phenomena are associated with cyclonic activity over Romania. The aim of this paper is to assess a correlation between the cyclone frequency into a representative area for Romania and the circulation types... more
Generally, the severe weather phenomena are associated with cyclonic activity over Romania. The aim of this paper is to assess a correlation between the cyclone frequency into a representative area for Romania and the circulation types conform to "COST733 Catalogue". The selected domain was between 10° and 35° E longitude and 35° and 55° N latitude. The selected area is similar to Domain 10 from COST733 Catalogue. The Mediterranean cyclones, reaching this domain from the south-west can be accounted for. The cyclones of Icelandic origin with north-west to south-east trajectories sometimes are reactivated in Central Europe through cold air penetrating the upper troposphere and reach over Romanian territory. A peculiar category is that of cyclones moving along retrograde tracks. Using daily NCEP/NCAR reanalysis data for the sea level pressure, a subjective analysis of cyclone frequency has been performed for the cold period (the 1 st of November- the 31 st of March) between 1...
The paper presents results from a study examining the relationship between large-scale modes of climate variability with the fluctuations in the yield of barley, durum wheat, olives and sunflower crops in Tuscany, Italy. In particular,... more
The paper presents results from a study examining the relationship between large-scale modes of climate variability with the fluctuations in the yield of barley, durum wheat, olives and sunflower crops in Tuscany, Italy. In particular, the blocking circulation over the growing season, with associated hot and dry conditions, decreased yield for olive crops, barley and durum wheat. The teleconnections analysed in this study are the winter North Atlantic Oscillation (NAO) and the Summer North Atlantic Oscillation (SNAO); the West African Monsoon (WAM) and the Intertropical Front (ITF); and although NAO, SNAO, ITF and WAM are not strictly related to each other, the values of these indices are strongly related to the atmospheric circulation regimes and related weather types. Thus, they have an impact on precipitation and temperature patterns in Italy and on yields of important crops in Tuscany. Results show that the large-scale temperate and tropical variability directly influences the c...
The understanding of past and present glacier variations is a key task for evaluating current climate change. Historical and proxy-records have documented a partly asynchronous evolution in temperature, precipitation and glacial... more
The understanding of past and present glacier variations is a key task for evaluating current climate change. Historical and proxy-records have documented a partly asynchronous evolution in temperature, precipitation and glacial variations between European regions during the Little Ice Age (LIA), with the causes of these temporal anomalies yet being poorly understood. The comparison between the Alps and Scandinavia allows an assessment of the spatial distribution of glacier fluctuations in the studied areas during the last few centuries. Here we present temporally high-resolved glacier reconstructions for southern Norway covering the period back to the 17th century, based on newly discovered historical material. Length changes were determined by the interpretation of high-quality historical documents such as drawings, paintings, prints, photographs, maps and written sources that are abundant for selected glaciers in the area (Folgefonna, Jostedalsbreen). Historical material is only ...
The South American monsoon system (SAMS) is the most important climatic feature in South America and is characterized by pronounced seasonality in precipitation during the austral summer. This study compares several statistical properties... more
The South American monsoon system (SAMS) is the most important climatic feature in South America and is characterized by pronounced seasonality in precipitation during the austral summer. This study compares several statistical properties of daily gridded precipitation from different data (1998–2008): 1) Physical Sciences Division (PSD), Earth System Research Laboratory [1.0° and 2.5° latitude (lat)/longitude (lon)]; 2) Global Precipitation Climatology Project (GPCP; 1° lat/lon); 3) Climate Prediction Center (CPC) unified gauge (CPC-uni) (0.5° lat/lon); 4) NCEP Climate Forecast System Reanalysis (CFSR) (0.5° lat/lon); 5) NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis (0.5° lat/0.3° lon); and 6) Tropical Rainfall Measuring Mission (TRMM) 3B42 V6 data (0.25° lat/lon). The same statistical analyses are applied to data in 1) a common 2.5° lat/lon grid and 2) in the original resolutions of the datasets. All datasets consistently represent the larg...
We find that part of the uncertainty in the amplitude and pattern of the modeled precipitation response to CO2 forcing traces to tropical condensation not directly involved with parameterized convection. The fraction of tropical rainfall... more
We find that part of the uncertainty in the amplitude and pattern of the modeled precipitation response to CO2 forcing traces to tropical condensation not directly involved with parameterized convection. The fraction of tropical rainfall associated with large-scale condensation can vary from a few percent to well over half depending on model details and parameter settings. In turn, because of the coupling between condensation and tropical circulation, the different ways model assumptions affect the large-scale rainfall fraction also affect the patterns of the response within individual models. In two single-model ensembles based on the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM), versions 3.1 and 5.3, we find strong correlations between the fraction of tropical large-scale rain and both climatological rainfall and circulation and the response to CO2 forcing. While the effects of an increasing tropical large-scale rain fraction are opposite in som...
A seasonal forecasting technique to produce probabilistic and deterministic streamflow forecasts for 23 basins in Norway and northern Sweden is developed in this work. Large scale circulation and moisture fields, forecasted by the... more
A seasonal forecasting technique to produce probabilistic and deterministic streamflow forecasts for 23 basins in Norway and northern Sweden is developed in this work. Large scale circulation and moisture fields, forecasted by the ECHAM4.5 model 4 months in advance, are used to forecast spring flows. The technique includes model output statistics (MOS) based on a non-linear Neural Network (NN) approach. Results show that streamflow forecasts from Global Circulation Model (GCM) predictions, for the Scandinavia region are viable and highest skill values were found for basins located in south-western Norway. The physical interpretation of the forecasting skill is that stations close to the Norwegian coast are directly exposed to prevailing winds from the Atlantic Ocean, which constitute the principal source of predictive information from the atmosphere on the seasonal timescale.
The interannual rainfall variability over the southeast Australian state of Victoria is known to be influenced by a number of large scale and regional phenomena, including the Indian Ocean Dipole (IOD), Southern Oscillation Index (SOI),... more
The interannual rainfall variability over the southeast Australian state of Victoria is known to be influenced by a number of large scale and regional phenomena, including the Indian Ocean Dipole (IOD), Southern Oscillation Index (SOI), and Southern Annular Mode (SAM). However, the role of ‘upstream’ regional circulation or pressure anomalies has received only modest attention. The amount of winter (May-August) rainfall over the state has declined over the past few decades, especially from 1960 to 2017. Using the Center of Action (COA) technique this study examines the relationship between winter precipitation over Victoria and the characteristics of the Indian Ocean High (IOH) over the period 1951–2021. We show that variations of the IOH are strongly linked with those of precipitation over Victoria. The strongest link is with the Indian Ocean High pressure (IOH_P) and its longitudinal position (IOH_LN), whereas the Indian Ocean High latitude (IOH_LT) has little impact. Less precipitation is observed across the state when IOH_P anomalies are positive, whereas the eastward shift of the IOH_LN is a major factor in the reduction of precipitation. Using correlation and multiple regression analyses, we find that the IOH indices explain 54% of the winter precipitation variation. The strength of this relationship is somewhat weaker in the northern part of the state, partly because of the additional influence of ‘north-west cloud bands’ north of the Great Diving Range. Finally, we perform composite analyses of anomalous high (low) years of IOH to establish evidence of IOH influencing Victorian rainfall. his allows us to reveal the dynamical mechanisms behind the revealed associations.
ABSTRACTComplex orography of elevated terrain and numerous peaks can act as an important physical barrier to the atmospheric flow and can generate a range of meteorological phenomena. The objective of this study is to investigate the... more
ABSTRACTComplex orography of elevated terrain and numerous peaks can act as an important physical barrier to the atmospheric flow and can generate a range of meteorological phenomena. The objective of this study is to investigate the effect of the Brazilian Plateau on the spatial distribution of cold fronts and their climatology for the period between 1979 and 2010 using Climate Forecast System Reanalysis data. The cold fronts are detected and divided into three groups, according to their frequency and trajectory over South America: the continental fronts are referred to as the AN group; the fronts that pass over the coastal region of São Paulo are referred to as the SP group; and the fronts that pass over the two areas are referred to as the ANSP group. Composites of means and anomalies of atmospheric variables are constructed for each group. The investigation focuses on the orographic effects of the Brazilian Plateau on the climatology of the cold fronts. The Brazilian Plateau aff...
A detailed non parametric statistical analysis of the evolutions of the daily mean and variance of seasonal tem-perature in Europe revealed a rather strong link between the trends in mean and variance. In winter, variance generally... more
A detailed non parametric statistical analysis of the evolutions of the daily mean and variance of seasonal tem-perature in Europe revealed a rather strong link between the trends in mean and variance. In winter, variance generally decreases when mean increases whereas in ...
In both the tropical and extratropical regions there are a large number of dynamical problems which can be addressed by mesosphere-stratosphere-troposphere (MST) radars. The distinct advantage the MST radar has over rocket observations is... more
In both the tropical and extratropical regions there are a large number of dynamical problems which can be addressed by mesosphere-stratosphere-troposphere (MST) radars. The distinct advantage the MST radar has over rocket observations is continuous data acquisition. Without a doubt, the time-space spectrum of the mesospheric flow field is rich in high frequency motions associated with gravity waves rather than turbulent (random) fluctuations, and these events are particularly amenable to analysis with continuous data sets. In addition to the high frequency motions these are longer period fluctuations in the upper stratosphere and mesosphere wind fields which, combined with temperature fields derived from satellite data or lidars, can greatly enhance our knowledge of the upper atmosphere.