27 research outputs found
Sorption of uranyl ions from aqueous solutions using crosslinked maleic anhydride-octene-styrene terpolymer
No full textAre greenhouse gas signals of Northern Hemisphere winter extra-tropical cyclone activity dependent on the identification and tracking algorithm?
Get PDFFor Northern Hemisphere extra-tropical cyclone activity, the dependency of a potential anthropogenic climate change signal on the identification method applied is analysed. This study investigates the impact of the used algorithm on the changing signal, not the robustness of the climate change signal itself. Using one single transient AOGCM simulation as standard input for eleven state-of-the-art identification methods, the patterns of model simulated present day climatologies are found to be close to those computed from re-analysis, independent of the method applied. Although differences in the total number of cyclones identified exist, the climate change signals (IPCC SRES A1B) in the model run considered are largely similar between methods for all cyclones. Taking into account all tracks, decreasing numbers are found in the Mediterranean, the Arctic in the Barents and Greenland Seas, the mid-latitude Pacific and North America. Changing patterns are even more similar, if only the most severe systems are considered: the methods reveal a coherent statistically significant increase in frequency over the eastern North Atlantic and North Pacific. We found that the differences between the methods considered are largely due to the different role of weaker systems in the specific methods
IMILAST: a community effort to intercompare extratropical cyclone detection and tracking algorithms
Get PDFThe variability of results from different automated methods of detection and tracking of extratropical cyclones is assessed in order to identify uncertainties related to the choice of method. Fifteen international teams applied their own algorithms to the same dataset—the period 1989–2009 of interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERAInterim) data. This experiment is part of the community project Intercomparison of Mid Latitude Storm Diagnostics (IMILAST; see www.proclim.ch/imilast/index.html). The spread of results for cyclone frequency, intensity, life cycle, and track location is presented to illustrate the impact of using different methods. Globally, methods agree well for geographical distribution in large oceanic regions, interannual variability of cyclone numbers, geographical patterns of strong trends, and distribution shape for many life cycle characteristics. In contrast, the largest disparities exist for the total numbers of cyclones, the detection of weak cyclones, and distribution in some densely populated regions. Consistency between methods is better for strong cyclones than for shallow ones. Two case studies of relatively large, intense cyclones reveal that the identification of the most intense part of the life cycle of these events is robust between methods, but considerable differences exist during the development and the dissolution phases
Original Russian Text © I.I. Mokhov, A
Get PDFWe performed analysis of variations in the characteristics of cyclonic activity and cloudiness, including their mutual variations in the atmosphere of the Northern Hemisphere (NH) from the tropical to polar latitudes based from model calculations under the condition of climate changes in comparison with the satellite data and reanalysis data The objective of the joint analysis of variations in the characteristics of cyclonic activity and cloudiness during climate changes is related to the necessity of diagnosis the joint evolution and mutual influence of the general atmospheric circulation and radiationcloudiness processes in the climate system In our analysis, we used the results of numerical simulations of the daily global fields at sealevel pressure (SLP) and cloudiness with the climate general calculation model (CGCM) IPSL-CM4 In the calculation performed with the CMGH IPSK-CM4 model, we specified anthropogenic emissions of greenhouse gases and aerosol into the atmosphere based on the data of observations for the period 1860-2000 and according to the anthropogenic scenario SRES-A2 for 2001-2100. Cyclones and anticyclones were distinguished as regions of low and high pressure, respectively, limited by closed contour lines (isohypses) based on the data of geopotential similarly to [9] (see also We used for comparison the results of the analysis of cyclonic activit
Original Russian Text © I.I. Mokhov, A
No full textWe performed analysis of variations in the characteristics of cyclonic activity and cloudiness, including their mutual variations in the atmosphere of the Northern Hemisphere (NH) from the tropical to polar latitudes based from model calculations under the condition of climate changes in comparison with the satellite data and reanalysis data The objective of the joint analysis of variations in the characteristics of cyclonic activity and cloudiness during climate changes is related to the necessity of diagnosis the joint evolution and mutual influence of the general atmospheric circulation and radiationcloudiness processes in the climate system In our analysis, we used the results of numerical simulations of the daily global fields at sealevel pressure (SLP) and cloudiness with the climate general calculation model (CGCM) IPSL-CM4 In the calculation performed with the CMGH IPSK-CM4 model, we specified anthropogenic emissions of greenhouse gases and aerosol into the atmosphere based on the data of observations for the period 1860-2000 and according to the anthropogenic scenario SRES-A2 for 2001-2100. Cyclones and anticyclones were distinguished as regions of low and high pressure, respectively, limited by closed contour lines (isohypses) based on the data of geopotential similarly to [9] (see also We used for comparison the results of the analysis of cyclonic activit
The Dynamic Character of Northern Hemisphere Flow Regimes in a Near-Term Climate Change Projection
Get PDFThe dynamic character of an enstrophy-based diagnostic, previously used in the study of atmospheric blocking, is examined here, in near-term future simulations from the Institut Pierre Simon Laplace Climate Model version 4 (IPSL-CM4) and version 5 (IPSL-CM5) climate models of the Northern Hemisphere flow for moderate climate change scenarios. Previous research has shown that integrated regional enstrophy (IE) increases during blocking onset and decay, which is a reflection of planetary-scale instability. In addition, IE has been shown previously to increase during flow regime transitions in general, even those not associated with blocking events. Here, a 31-year IE diagnostic time series is examined for changes in short term (5–40 days) planetary-scale variability that may correspond flow regime changes in an increased carbon dioxide environment. The time-series analysis herein indicates that the IE diagnostic provides evidence for approximately 30–35 atmospheric flow regime transitions per year in a warmer climate, which is similar to that of the control run and the latest 30-year observed climate, as derived from re-analyses. This result has implications regarding the predictability of weather in a warmer world
Integrated Regional Enstrophy and Block Intensity as a Measure of Kolmogorov Entropy
Get PDFEnstrophy in a fluid relates to the dissipation tendency in a fluid that has use in studying turbulent flows. It also corresponds to vorticity as kinetic energy does to velocity. Earlier work showed that the integrated regional enstrophy (IRE) was related to the sum of the positive Lyapunov exponents. Lyapunov exponents are the characteristic exponent(s) of a dynamic system or a measure of the divergence or convergence of system trajectories that are initially close together. Relatively high values of IRE derived from an atmospheric flow field in the study of atmospheric blocking was identified with the onset or demise of blocking events, but also transitions of the large-scale flow in general. Kolmogorv–Sinai Entropy (KSE), also known as metric entropy, is related to the sum of the positive Lyapunov exponents as well. This quantity can be thought of as a measure of predictability (higher values, less predictability) and will be non-zero for a chaotic system. Thus, the measure of IRE is related to KSE as well. This study will show that relatively low (high) values of IRE derived from atmospheric flows correspond to a more stable (transitioning) large-scale flow with a greater (lesser) degree of predictability and KSE. The transition is least predictable and should be associated with higher IRE and KSE
