Surface ozone concentration variability in Moscow and Kiev

The comparison is represented of the results of surface ozone concentration measurements in two megalopolises, Moscow and Kiev. A temporal course of ozone concentration and temperature in both cities is close by the shape and is typical of medium-polluted plain stations. In both megalopolises, two maxima are observed within the seasonal ozone concentration variability, in spring and summer, and during the day, a usual ozone concentration maximum (approximately in 2–3 hours after the local noon) and the night one being typical of big cities. An average ozone concentration and an average temperature in corresponding periods are higher in Kiev than in Moscow. Evidently, the summer maximum is associated with photochemical ozone generation processes, and the spring one, with dynamic processes of its transport in the atmosphere. In both megalopolises, the episodes are observed in the warm period under meteorological conditions being unfavorable for the pollutant scattering in the atmosphere when the ozone concentration exceeds the threshold limit value and is dangerous for health. The repeatability of such episodes is the highest one in July-August. In Kiev, such episodes are more frequent than in Moscow. An effective statistical model is constructed for both megalopolises in which the observed ozone concentration is represented in the form of regression function of temperature and relative humidity.     

Statistical forecast of surface ozone concentration in Moscow

Two synoptic-statistical methods for forecasting daily maximum surface ozone concentrations are proposed based on the relations between surface ozone and meteorological variables in the Moscow region. The methods use current ozone measurements and forecasts of meteorological variables and of synoptic situation. Statistically, the methods provide better forecast results than climatic and persistence methods. Compared with the persistence forecast, the above methods reduce the variance of the forecast error from 1.5 to 2 times. The most significant predictors for forecasting daily maximum surface ozone concentration with lead times of one to three days for Moscow are the forecast time (Julian day of the year), prognostic temperature, relative humidity, indices of the meteorological pollution potential of the atmosphere (MPP), and surface ozone concentration observed on the previous day. The forecast efficiency is demonstrated using the 2006 observational data from the stations of the Institute of Atmospheric Physics of the Russian Academy of Sciences-Moscow State University and Mosecomonitoring State Nature Protection Organization.     

Interannual to decadal summer drought variability over Europe and its relationship to global sea surface temperature

Interannual to decadal variability of European summer drought and its relationship with global sea surface temperature (SST) is investigated using the newly developed self calibrated Palmer drought severity index (scPDSI) and global sea surface temperature (SST) field for the period 1901–2002. A European drought severity index defined as the average of scPDSI over entire Europe shows quasiperiodic variations in the 2.5–5 year band as well as at 12–13 years suggesting a possible potential predictability of averaged drought conditions over Europe. A Canonical Correlation Analysis between summer scPDSI anomalies over Europe and global SST anomalies reveals the existence of three modes of coupled summer drought scPDSI patterns and winter global SST anomalies. The first scPDSI-SST coupled mode represents the long-term trends in the data which manifest in SST as warming over all oceans. The associated long-term trend in scPDSI suggests increasing drought conditions over the central part of Europe. The second mode is related to the inter-annual ENSO and decadal PDO influence on the European climate and the third one captures mainly the drought pattern associated to Atlantic Multidecadal Oscillation. The lag relationships between winter SST and summer drought conditions established in this study can provide a valuable skill for the prediction of drought conditions over Europe on interannual to decadal time scales.     

On the future reduction of snowfall in western and central Europe

Large parts of western and central Europe face a 20–50 % future reduction in snowfall on Hellmann days (days with daily-mean temperatures below freezing). This strong reduction occurs in addition to the expected 75 % decrease of the number of Hellmann days near the end of the twenty first century. The result is insensitive to the exact freezing-level threshold, but is in sharp contrast with the winter daily precipitation, which increases under most global warming scenarios. Not only climate model simulations show this. Observational records also reveal that probabilities for precipitation on Hellmann days have been larger in the past. The future reduction is a consequence of the freezing-level threshold becoming a more extreme quantile of the temperature distribution in the future. Only certain circulation types permit these quantiles to be reached, and it is shown that these have intrinsically low precipitation probability.     

Investigation of ENSO variability using cyclostationary EOFs of observational data

Summary ?The variability of El Ni?o-Southern Oscillation (ENSO) on all time scales, ranging from months to decades, has been studied from the perspective of sea-surface temperature anomaly (SSTA), sea-level pressure anomaly (SLPA), and surface wind anomaly (SWA) fields using a statistical tool called cyclostationary empirical orthogonal function (CSEOF) analysis. The analysis indicates that a significant fraction of variability in the tropical Pacific can be explained in terms of an irregular interplay of two dominant modes: the low-frequency mode and the biennial mode. These modes, and in particular the biennial mode, are well defined coupled modes of the tropical ocean-atmospheric circulation system, as suggested by strong correlation (> 0.9) in the evolution of the different physical variables. The low-frequency mode and its PC time series are very similar to the so-called “interdecadal” mode identified by earlier investigators. The corresponding PC time series of the low-frequency mode has a broad spectral peak at 5.3 yrs. The biennial mode represents the oscillation pattern of El Ni?o and La Ni?a and has a clear biennial cycle, the amplitude of which varies on a longer time scale. There is a broad spectral peak also at 5.3 yrs in the principal component (PC) time series of this mode. Unlike in earlier studies, this biennial mode is clearly separable from the low-frequency mode, since these two modes have different physical evolution patterns. Results of the present study also indicate that the biennial component, having a clear phase-locking tendency, is not as variable as has been suggested in some previous investigations. It is shown that much of the inter-El Ni?o variability can be explained in terms of an irregular interplay between the biennial mode and the low-frequency mode. Finally, the role of the low-frequency mode in the tropical Pacific seems to be more important than has been suggested previously. Specifically, recent warming events since 1975 are shown to be associated with the low-frequency mode rather than with the biennial mode. Received August 15, 2001; revised March 6, 2002     

Compound summer temperature and precipitation extremes over central Europe

Theoretical and Applied Climatology - Reliable knowledge of the near-future climate change signal of extremes is important for adaptation and mitigation strategies. Especially compound extremes,...     

The Last Glacial Maximum climate over Europe and western Siberia: a PMIP comparison between models and data

 Under the framework of the Palaeoclimate Modelling Intercomparison Project (PMIP), 17 climate models, 16 of which are atmospheric general circulation models, have been run to simulate the climate of the Last Glacial Maximum (21 000 years ago) using the same set of boundary conditions. Parallel to these numerical experiments, new, consistent, data bases have been developed on a continental scale. The present work compares the range of the model responses to the large perturbation corresponding to the conditions of the Last Glacial Maximum with consistently derived climate reconstructions from pollen records over Europe and western Siberia. It accounts for the differences in the model results due to the models themselves and directly compares this “error bar” due to the models to the uncertainties in the climate reconstructions from the pollen records. Overall the Last Glacial Maximum climate simulated by the models over western Europe is warmer, especially in winter, and wetter than the one depicted by the reconstructions. This is the region where the reconstructed increase in temperature, precipitation and moisture index from the Last Glacial Maximum to the present conditions is largest. The same disagreement, but of smaller amplitude, is found over Central Europe and the eastern Mediterranean Basin, while models and data are in broad agreement over western Siberia. The numerous modelling results allow a study of the link between the changes in atmospheric circulation and those in temperature, and an interpretation of the discrepancies in precipitation in terms of those in temperature. Received: 1 February 2000 / Accepted: 9 May 2000     

Comparison of two gas-phase chemical kinetic mechanisms of ozone formation over Europe

Two recent gas-phase chemical kinetic mechanisms for tropospheric ozone formation, one based on the lumped-structure approach (CB05) and the other based on the lumped-molecule approach (RACM2), are compared for simulations of ozone over Europe. The host air quality model is POLAIR3D of the Polyphemus modeling platform. A one-month period (15 July to 15 August 2001) is simulated. Model performance is satisfactory with both mechanisms. Overall, the two mechanisms give similar results with a domain-averaged difference of 3 ppb and a mean fractional absolute difference of 5% (values averaged over the month for the daily 8-h average maximum ozone concentrations). This difference results from different treatments in the two mechanisms for both inorganic and organic chemistry. Differences in the treatment of the inorganic chemistry are due mainly to differences in the kinetics of two reactions: NO + O₃ \(\longrightarrow\) NO₂ + O₂ and NO + HO₂ \(\longrightarrow\) NO₂ + OH. These differences lead to a domain-averaged difference in ozone concentration of 5%, with RACM2 kinetics being more conducive to ozone formation. Differences in the treatment of organic chemistry lead to a domain-averaged difference in ozone concentration of 3%, with CB05 chemistry being more conducive to ozone formation. This average difference results in part from compensating effects among various VOC classes and some significant differences are identified at specific locations (the coastline of northern Africa and eastern Europe: 9%) and for specific organic classes (aldehydes, biogenic alkenes and aromatics). Differences in the treatment of the organic chemistry result from various aspects. For some VOC classes, such as aldehydes and biogenic alkenes, the more detailed explicit treatments using more model species in RACM2 lead to either greater or lower reactivity depending on the assumptions made for the oxidation products. For other VOC species, such as aromatics, the assumptions made about the major chemical oxidation pathways (aromatic alcohol formation in CB05 vs. ring opening in RACM2) affect the ozone formation significantly. Reconciliation of different chemical kinetic mechanisms will require experimental data to reduce current uncertainties in the kinetic (e.g., NO oxidation) and mechanistic (e.g., aromatics oxidation) representations of major chemical pathways.     

Intraseasonal variability of winter precipitation over central asia and the western tibetan plateau from 1979 to 2013 and its relationship with the North Atlantic Oscillation

Winter precipitation over Central Asia and the western Tibetan Plateau (CAWTP) is mainly a result of the interaction between the westerly circulation and the high mountains around the plateau. Empirical Orthogonal Functions (EOFs), Singular Value Decomposition (SVD), linear regression and composite analysis were used to analyze winter daily precipitation and other meteorological elements in this region from 1979 to 2013, in order to understand how interactions between the regional circulation and topography affect the intraseasonal variability in precipitation. The SVD analysis shows that the winter daily precipitation variability distribution is characterized by a dipole pattern with opposite signs over the northern Pamir Plateau and over the Karakoram Himalaya, similar to the second mode of EOF analysis. This dipole pattern of precipitation anomaly is associated with local anomalies in both the 700 hPa moisture transport and the 500 hPa geopotential height and is probably caused by oscillations in the regional and large-scale circulations, which can influence the westerly disturbance tracks and water vapor transport. The linear regression shows that the anomalous mid-tropospheric circulation over CAWTP corresponds to an anti-phase variation of the 500 hPa geopotential height anomalies over the southern and northern North Atlantic 10 days earlier (at 95% significance level), that bears a similarity to the North Atlantic Oscillation (NAO). The composite analysis reveals that the NAO impacts the downstream regions including CAWTP by controlling south-north two branches of the middle latitude westerly circulation around the Eurasian border. During the positive phases of the NAO, the northern branch of the westerly circulation goes around the northwest Tibetan Plateau, whereas the southern branch encounters the southwest Tibetan Plateau, which leads to reduced precipitation over the northern Pamir Plateau and increased precipitation over the Karakoram Himalaya, and vice versa.     

WRF ARW and CHIMERE models for numerical forecasting of surface ozone concentration

Results of joint calculations with meteorological WRF ARW model and chemistry transport CHIMERE model are considered as a basis of the modern system of the air quality assessment and forecasting. The system was designed in the Russian Hydrometeorological Center and Institute of Applied Physics of the Russian Academy of Sciences. Detailed prognostic information about the atmosphere state provided by the WRF ARW was used in the CHIMERE model for describing the air mass transport processes, chemical transformation, and pollution deposition. Results of retrieval and forecast of surface ozone concentration as one of main air quality indicators are under consideration. Calculations of ozone concentrations for different configurations of a prognostic system differ in resolution of model grid and in the way the boundary conditions are prescribed.     

Results of surface ozone monitoring in the atmosphere over Ulan-Ude

Presented are the results of surface ozone monitoring in the atmosphere over Ulan-Ude during the period from 2000 to 2012. Revealed are seasonal and diurnal variations of surface ozone. The analysis of the seasonal variability of surface ozone concentration indicates the presence of the clearly pronounced maximum in spring-summer period. A statistical model of forecasting single concentrations of the surface ozone is considered using the multiple regression analysis. Temperature, relative humidity, wind direction, wind speed, turbulence factor, temperature gradient, velocity of vertical flow, and concentrations of minor gas admixtures such as nitrogen oxides are used as predictors. Analyzed are statistical relationships, where observed ozone values are presented in the form of the regression function of the most significant predictors.     

应用MODIS资料对城乡地表热通量的估算

为了揭示城市热岛形成机制,基于MODIS资料,结合自动气象站实测的气象资料,利用地表能量参数化方法估算了地表热通量,分析了城乡地表热通量的空间分布及变化特征.结果表明城乡地气热交换差异明显,与相关文献对比证明该方法是可行、有效的.     

Vertical Ozone Profile over Tibet Using Sage I and II Data

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Long-term variability in the date of monsoon onset over western India

The date of onset of the southwest monsoon in western India is critical for farmers as it influences the timing of crop plantation and the duration of the summer rainy season. Identifying long-term variability in the date of monsoon onset is difficult, however, as onset dates derived from the reanalysis of instrumental rainfall data are only available for the region from 1879. This study uses documentary evidence and newly uncovered instrumental data to reconstruct annual monsoon onset dates for western India for the period 1781–1878, extending the existing record by 97 years. The mean date of monsoon onset over the Mumbai (Bombay) area during the reconstruction period was 10 June with a standard deviation of 6.9 days. This is similar to the mean and standard deviation of the date of monsoon onset derived from instrumental data for the twentieth century. The earliest identified onset date was 23 May (in 1802 and 1839) and the latest 22 June (in 1825). The longer-term perspective provided by this study suggests that the climatic regime that governs monsoon advance over western India did not change substantially from 1781 to 1955. Monsoon onset over Mumbai has occurred at a generally later date since this time. Our results indicate that this change is unprecedented during the last 230 years. Following a discussion of the results, the nature of the relationship between the date of monsoon onset and the El Niño-Southern Oscillation is discussed. This relationship is shown to have been stable since 1781.     

Climatology and long-term variability of the annual cycle of air temperature over Europe

Climatology and long-term variations of characteristics of the annual cycle of air temperature over Europe are studied in terms of amplitudes and phases on the basis of data for 1901–2000. It is shown that the spatial amplitude distribution of the annual cycle of air temperature well reflects a decrease in the influence of the Atlantic and an increase in the continentality of the European climate from west to east. It is found that positive (negative) anomalies of annual mean air temperature are accompanied mainly by negative (positive) anomalies of amplitudes and phases of the annual cycle air temperature. In other words, abnormally warm years are characterized by smaller amplitudes of the annual cycle, and the maximum in the annual cycle of air temperature is observed earlier than usual. The first empirical orthogonal function (EOF) mode of temperature amplitudes is connected with the North Atlantic Oscillation (NAO). It means that at a high NAO index one observes small (large) amplitudes of the annual cycle of air temperature over Europe.     

A meteorological analysis of ozone episodes using HYSPLIT model and surface data

Ozone episodes (> 100 ppbv) were observed frequently in Jinan, an urban site located between the highly polluted Yangtze Delta and Beijing–Tianjin region in East China. In this study, the ozone episodes observed in 2004 were analysed using the Hybrid Single-particle Lagrangian Integrated Trajectory (HYSPLIT) model and surface meteorological data, as well as Air Pollution Index (API). The meteorological conditions of episode days and non-episode days were compared and examined, and categorization of 6 groups of backward trajectories was performed. The results show that, most episodes were caused by local photochemical production (e.g., induced by sufficient sunshine duration and high temperature) and pollutant accumulation (e.g., induced by little rainfall and low wind speed), and transport of pollutants from the highly polluted regions could significantly influence the air quality at the site, especially from Yangtze Delta region. In addition, three typical ozone episodes were analysed using HYSPLIT model to infer any long-distance transport and surface meteorological data to infer the local ozone production potential. At last, the functions and inadequacies about the usage of HYSPLIT model combined with surface meteorological data for the analysis of photochemical pollution were discussed.