Presented are the data of measurements of aerosol optical depth (AOD) of the atmosphere at the wavelength of 500 nm for the period from 1984 to 2009 at Issyk Kul monitoring station located in the central part of Eurasia. The decrease in AOD by about 4.3% took place during the measurement period. Revealed are the seasonal variations, linear trends, and periods of AOD increase associated with volcanic eruptions. The spectral analysis of measurement data using the Fourier and wavelet transforms enabled determining the basic characteristics of the constituents of AOD variations. The linear trend changes from positive to negative from 1995 to 2009 that may indicate increase in the amount of aerosol in these years. Proposed is a simple statistical model for describing the temporal variations of AOD.

The results of measurements of the CO content in the atmospheric thickness by the method of solar molecular-absorption spectroscopy are presented. Over 87 months of observations, the annual mean CO content decreased by ∼19% at a mean rate of changes equal to −(0.14 ± 0.02) atm cm per year. Maxima and minima of seasonal variations most often fall on February and September, respectively. The mean overall amplitude of changes in the CO content during the annual cycle is about 50% of the mean value. The Fourier analysis revealed variations in the CO composition with periods from 3 to 84 months. A simple statistical model satisfactorily describes time changes in the CO content in the atmospheric thickness. The results of measurements of the CO content in the atmospheric thickness are compared with the data of CO measurements in samples of surface air at stations of the Global Atmospheric Watch.

The results of an analysis of data on the total content of nitrogen dioxide in a vertical atmospheric column are given. These data have been obtained from measurements with the twilight method over a period of 25 years. The monthly and annual means (the arithmetic means of both morning and evening values) of NO2, on the whole, have increased by ∼6% in spite of its rapid decrease in 1991–1995 due to the Pinatubo eruption. The linear-trend index amounts to 0.23% per year. The annual mean over the entire observation time is equal to (3.18 ± 0.05) × 1015 mol/cm2, and the amplitude of seasonal variations amounts to (2.39 ± 0.04) × 1015 mol/cm2. Spectral analysis of the experimental data has revealed compound oscillations with periods of 6 to 253 months, the values of which do not contradict published data. Most of these oscillations are nonharmonic. A simple statistical model satisfactorily describes time variations in the monthly and annual means of NO2 with rms deviations of ∼4% and 1%, respectively.

We present the data of measurements of the atmospheric transparency at a wavelength of 500 nm in the period from 1982 to 2007 at the Issyk Kul station, located in a mountainous region of Central Asia. Seasonal variations, a linear trend, and the period of a noticeable decrease in the transparency associated with volcanic eruptions are revealed. We note that in recent years (1995–2007) the linear trend has become negative: B = −(1.50±0.06) × 10−3 rel. units per year at P 0 = (0.80±0.01) rel. units. This observation may indicate that the aerosol content in the atmosphere increased, although there were no powerful volcanic eruptions during the specified period. Spectral analysis of the data of atmospheric transparency measurements was performed with the use of the Fourier and wavelet transforms. The main characteristics of transparency variations are determined. A simple statistical model was used for the description of time variations in monthly and annual means of the transparency.

Ground‐based UV‐visible instruments for NO2 vertical column measurements have been operating at Issyk‐Kul station, in Kyrgyzstan, and Observatoire de Haute‐Provence (OHP), in France, since 1983 and 1992, respectively. These measurements have already been used for validation of ERS‐2 Global Ozone Monitoring Experiment (GOME) and Envisat Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) NO2 column data. Building upon the successful missions of GOME and SCIAMACHY, the Ozone Monitoring Experiment (OMI) was launched by NASA onboard the EOS Aura satellite in July 2004. Here we present the results of recent comparisons between OMI NO2 operational data (standard product) and correlative ground‐based twilight measurements in midlatitudes, at Issyk‐Kul and OHP, in 2004–2006. The stratospheric NO2 columns, observed by OMI and our ground‐based instruments, have been corrected for NO2 diurnal change and normalized to local noon values using a photochemical box model. According to our comparison, OMI stratospheric NO2 columns underestimate ground‐based measurements by (0.3 ± 0.3) × 1015 molecules/cm2 and (0.7 ± 0.6) × 1015 molecules/cm2 at Issyk‐Kul and OHP, respectively. The effect of tropospheric pollution on the NO2 measurements in both regions of observations has been identified and discussed.

The results are presented of statistical analysis of the data obtained from the 1980–2006 systematic measurements of the volume concentration of carbon dioxide in the atmospheric thickness over central Eurasia. The trends of both monthly and yearly means of CO2 concentration are determined. During these 26 years, the yearly mean concentration increased by ∼42 ppm at a mean rate of (1.56 ± 0.18) ppm per year and reached ∼382.7 ppm. General statistical characteristics are found. The distribution function of the monthly mean concentrations of CO2 is characterized by the presence of a second maximum and a bias of the principal mode toward large values, and the mean (over the measurement time) monthly concentration and the median almost coincide. The distribution function of the yearly mean concentrations of CO2 is close to a normal distribution, and the mean (over the measurement time) yearly concentration, the median, and the mode also coincide. The trends of short-and long-period variations in the carbon dioxide concentration and their possible relation to a number of geophysical phenomena are revealed. Spectral analysis of the measuring data on CO2 revealed oscillations with periods of 4, 6, 12, 15, 21, 29, 40, 53, 84, and 183 months. A statistical model with the parameters of these oscillations describes the experimental monthly mean concentrations of carbon dioxide with an rms deviation of 2.3 ppm (±0.6% of the mean over the entire period 361.9 ppm) and the yearly mean concentrations with an rms deviation of 0.9 ppm (∼±0.3%).

Refined data of systematic measurements of total water vapor in the atmosphere from May 1980 to April 2005 are presented. The data were obtained at the Issyk Kul atmospheric-monitoring station by the method of solar molecular-absorption spectroscopy. Over 25 years, the annual mean water-vapor content in the atmosphere increased by 4.5% at a mean rate of increase of 0.18% per year. However, the water-vapor content decreased in the last five years. The results of statistical processing of experimental data (general statistical characteristics, correlation coefficients, composite oscillations) are described. A refined model is proposed for forecasts of temporal variations in the monthly mean and annual mean water-vapor contents for the coming years. The model includes a linear trend and the sum of oscillations with periods close to the periods of a number of well-known geophysical phenomena. Regression equations are proposed to relate the water-vapor content in the atmospheric column to the surface temperature and absolute humidity.

The results of long-term (1980–2003) systematic measurements of the total ozone content at the Issyk Kul station (42.6° N, 77.0° E; 1650 m above sea level) are presented. The statistical characteristics and spectral structure of variations in the total ozone and the main tendencies of its temporal variability are determined. It is found that the total ozone content decreased in 1980–2003 at an average rate of (−1.29±0.08) DU/yr. The results of Fourier and wavelet analyses have shown that only oscillations with periods of 12, 27–29, and 102–105 months are rather stable and can be represented as harmonic oscillations. Oscillations with periods shorter than six months have the character of periodically arising pulsations. Among these, oscillations with periods of 27–29 and 34–37 days can be distinguished. It is noted that the spectral-temporal structure of variations in the total ozone content obtained from ground-based measurements at the Issyk Kul station is in good agreement with the corresponding structure obtained from TOMS satellite measurements.

Aerosol optical depth measurements over Issyk‐Kul Lake acquired with the handheld sun photometer Microtops II are analyzed. Aerosol found over the mountainous region at the elevation of 1650 m above sea level resembles mostly clean background conditions. The yearly aerosol optical depth at a wavelength 500 nm ∼0.10 ± 0.03 is in agreement with the multi‐year means from the background sites of the Aerosol Robotic Network (AERONET). Over a period of 4 years optical depth showed a seasonal pattern, with a maximum observed during summer. A link has been made between new and previously acquired data in order to provide a reliable trend for the region.

Long‐term tropospheric nitrogen dioxide (NO2) column data obtained by the Global Ozone Monitoring Experiment (GOME) (G‐NO2) are evaluated to confirm the trends found in tropospheric NO2 abundances over East Asia between 1996 and 2002. For three locations in Central and East Asia, the G‐NO2 values are compared with tropospheric columns estimated from coincident observations of total NO2 by ground‐based UV/visible spectrometers and stratospheric NO2 by satellite solar occultation sensors (E‐NO2). The comparisons show a slight linear drift in G‐NO2 data from 1996 to 2002. However, it is much smaller than the standard deviation of the differences between G‐NO2 and E‐NO2 and much smaller than the increasing trends in NO2 seen by GOME over the industrial areas of China, demonstrating the validity of the trends estimated using the GOME data.

Here we present the results of comparison between operational NO2 vertical column data by Global Ozone Monitoring Experiment (GOME) onboard ERS-2 satellite and ground-based measurements at Issyk-Kul station in Kyrgyzstan, northern Tien Shan. The data of GOME, taken for the period of 1996–2002, was found to be reasonably close to the results of ground-based sunrise measurements. The latter were adjusted to the time of GOME overpass nearby noon, providing direct comparison between satellite and ground-based data. According to the results, there is 0.6 × 1015 mol/cm2 (∼18%) overestimation of NO2 vertical column by GOME, compared to our ground-based data.

The paper summarize results of comparisons between SCIAMACHY level 2 products and ground-based measurements at a number of stations in Russia and NIS, carried out for the period of ENVISAT commissioning phase validation in 2002 (ENVISAT AO-427). Basically, the study presents preliminary validation of SCIAMACHY ozone and NO2 vertical column data, coming from nadir-mode measurements in July-December 2002, and generated with the processor version 5.01 (SCIAMACHY Validation MasterSet). The comparison involves regular observations of total ozone at about 20 locations over Russia and NIS, and 2 sites of twilight NO2 vertical column measurements. In addition, CH4 vertical column data was compared to ground-based observations at 3 sites. The main results are compared to those achieved before with the similar studies on SCIAMACHY data version 3.53.

The results of long-term measurements of total ozone (TO) obtained during 1979-2001 over Tien Shan at the Issyk Kul (IK) station have been analyzed by the Fourier transform and the wavelet method. The results of the spectral analysis for TO were compared with similar results for the ground surface temperatures. It has been found that the variability of the surface temperature behavior correlates with the TO variations. To study the temperature spectral harmonics variations with altitude the NCER/NCAR data on temperature vertical distributions were used. It was found that within the range of 850-10 mb the temperature spectra behaved differently mainly at the heights less than those of the surrounding mountains (500 mb), below the polar tropopause (similar to250 mbar) and between the polar and tropical tropopauses. The peculiarities of TO harmonics for the periods from 15 to 45 months are in higher correlation with the temperature spectral harmonics up to levels of 100-50 mbar (over the tropical tropopause).

Present report summariz e th e firs t results of comparison s betw een SCIAMACHY leve l 2 products an d ground-based measurements at a number of station s in Russia and NIS, carried out for the period of commissioning phase validation. Basically, the study presents preliminary validation of SCIAMACHY ozone, NO2, CO, CH4 and H2O vertical column data, coming from the measurements of SCIAMACHY in nadir mode.

The data of long-term (1980-2000) continuous spectroscopic measurements of total water vapor content in the column of the continental atmosphere (the Issyk Kul station, the center of Eurasia) are given. The amplitudes and phases of water vapor seasonal variations have been defined, their long-term values and seasonal differences of the gas content variability are given for the observation site depending on the atmospheric temperature. A year-to-year variability of atmospheric total water vapor content is stated under a linear approximation that corresponds to an annual increase of its content by 0,015 g/cm(2). With the help of the spectral analysis of the data the main periodic components of water vapor variability were revealed with the periods of 6, 12, 35, 51 and 110 months. Their connection is shown with the temperature seasonal variations (periods of 6 and 12 months), with the El Nino phenomenon global consequences (a 51 month period) and with powerful volcanic eruptions (periods of 35, 51 and 110 months). An empirical statistical model was constructed for the atmospheric water vapor variability, that describes its mean monthly contents with an error of +/-13%.