Comparing data obtained from ground-based measurements of the total contents of O<Subscript>3</Subscript>, HNO<Subscript>3</Subscript>,HCl,and NO<Subscript>2</Subscript> and from their numerical simulation

Chemistry climate models of the gas composition of the atmosphere make it possible to simulate both space and time variations in atmospheric trace-gas components (TGCs) and predict their changes. Both verification and improvement of such models on the basis of a comparison with experimental data are of great importance. Data obtained from the 2009–2012 ground-based spectrometric measurements of the total contents (TCs) of a number of TGCs (ozone, HNO₃, HCl, and NO₂) in the atmosphere over the St. Petersburg region (Petergof station, St. Petersburg State University) have been compared to analogous EMAC model data. Both daily and monthly means of their TCs for this period have been analyzed in detail. The seasonal dependences of the TCs of the gases under study are shown to be adequately reproduced by the EMAC model. At the same time, a number of disagreements (including systematic ones) have been revealed between model and measurement data. Thus, for example, the EMAC model underestimates the TCs of NO₂, HCl, and HNO₃, when compared to measurement data, on average, by 14, 22, and 35%, respectively. However, the TC of ozone is overestimated by the EMAC model (on average, by 12%) when compared to measurement data. In order to reveal the reasons for such disagreements between simulated and measured data on the TCs of TGCs, it is necessary to continue studies on comparisons of the contents of TGCs in different atmospheric layers.     

The comparison of IR and MW ground-based measurements of total precipitable water

Water vapor is one of the basic climate gases playing a key role in various processes at different altitudes of the Earth’s atmosphere. An intercomparison and validation of different total precipitable water (TPW) measurement methods are important for determining the true accuracy of these methods, the shared use of data from multiple sources, the creation of data archives of different measurements, etc. In this paper, the TPW values obtained from measurements of solar IR spectral radiation (~8–9 μm absorption band) and thermal MW radiation of the atmosphere (1.35 cm absorption line) for 138 days of observation are compared. Measurements have been carried out from March 2013 to June 2014 at Peterhof station of the St. Petersburg State University in (59.88° N, 29.82° E). It is shown that MW measurements usually give higher TPW values than IR measurements. The bias between the two methods varies from 1 to 8% for small and large TPW values, respectively. With increasing TPW values, the bias reduces and for TPW > 1 cm it is ~1%. Standard deviation (SD) between the two methods reaches 7% for TPW < 0.4 cm and 3–5% for TPW > 1 cm. These data show the high quality of both remote sensing methods. Moreover, the IR measurements have a higher accuracy than MW measurements for small TPW values.     

Possibilities for determining temperature and emissivity of the land surface from data of satellite IR sounders with high spectral resolution (IRFS-2)

Numerical experiments on the simultaneous retrieval of the temperature and spectral emissivity of different land types are performed on the basis of inversion of the simulated high spectral resolution measurements by the IRFS-2 satellite IR sounder. The IRFS-2 data inversion method is based on using a priori information on the spectral behavior of emissivity of different land types and the multiple linear regression technique. The rms errors of determination of the underlying surface temperature using different solving operators are 0.26–0.71 K. The application of the developed IRFS-2 measurement inversion method makes it possible to estimate the land surface emissivity with an rms error not larger than 0.015.     

USE OF SATELLITE INFORMATION IN THE PREDICTION OF EL NIÑO EVENTS

Materials from surveys of 1982–1983 and 1997–1998 are analyzed for the two most powerful El Niño events in the 20th century, and four medium-intensity events are examined for the period 1986–1995. On the basis of online tracking of the dynamics of radiation processes in the equatorial ocean from space, a method is proposed for predicting different El Niño phases in five standard regions for up to 16 months in advance.     

Analysis of Capabilities for Satellite Monitoring of Atmospheric Gaseous Composition Using IRFS-2 Instrument

Capabilities of the total column monitoring of different minor gaseous compounds of the atmosphere with the satellite IRFS-2 Fourier interferometer have been studied. The possibilities of determining the СО₂, О₃, СH₄, HNO₃, N₂O, CH₃OH, HCFC-22, CFC-11, CFC-12, PAN, and ССl₄ total columns have been investigated on the basis of line-by-line calculations of the forward problem operator and calculation of error matrices by the optimal estimation method. It has been shown that the IRFS-2 device could be used to measure the total columns of СО₂, О₃, N₂O, СH₄, and HNO₃. In the information-gathering mode, it is also possible to retrieve the CH₃OH, HCFC-22, CFC-11, CFC-12, PAN, and ССl₄ total columns due to the suppression of random measurement errors.     

Intercomparison of satellite and ground-based ozone total column measurements

Ozone total column (OTC) measurements made in 2009–2012 near St. Petersburg by a Fourier Transform Infrared (FTIR) spectrometer (Peterhof, St. Petersburg State University (SPbSU)), an M-124 filter ozonometer, and a Dobson spectrophotometer (Voeikovo, MGO), as well as measurements made by a spectrometer ozone monitoring instrument (OMI) (onboard the AURA satellite) have been analyzed and compared. Comparisons have been performed both between ensembles of ground-based measurement data, as well as between ground-based and satellite data. It has been shown that the standard deviation for all devices is 2.5–4.5%; here, the FTIR and Dobson instruments measuring the direct sun are in better agreement with OMI than the M-124 ozonometer measuring the zenith-scattered solar radiation as well. A seasonal cycle in discrepancy with amplitude of 1.5% has been detected between two series of OTC measurements made by M-124 and OMI instruments for a total of 850 days. In fall and winter, the ground-based measurements underestimate the OTC values in comparison with satellite data; in spring and summer, the situation is reversed: ground-based data overestimate the OTC values. Also, it has been revealed that FTIR measurements systematically overestimate the OTC values in comparison with other instruments: from 1.4% (for Dobson) to 3.4% (for OMI). Taking into account the spatial and temporal discrepancy of independent ensembles of measurements and an analysis of standard deviations between ground-based and satellite measurement data, the FTIR spectrometer (SPbSU) can be recommended for OTC satellite data validation.     

The Satellite Atmospheric Sounder IKFS-2: 2. Validation of the Temperature Sounding of the Atmosphere

Izvestiya, Atmospheric and Oceanic Physics - The validation of measurements of vertical temperature profiles by the IKFS-2 instrument (the Meteor-M no. 2 satellite) in cloudless conditions was...     

Experimental Estimates of Integral Anthropogenic CO2 Emissions in the City of St. Petersburg

Izvestiya, Atmospheric and Oceanic Physics - The increase in the content of greenhouse gases (CO2, CH4, N2O, etc.) in the Earth’s atmosphere is changing the radiation balance and leading to...     

MIRIAM — a space-borne sun occultation experiment for atmospheric trace gas spectroscopy

The distribution of trace gases in earth's atmosphere will be analysed in a long term German-Russian space mission for more than three years, beginning in 1994. The FTIR-spectrometer, designed for this mission, has been tested with sun occultation measurements from the ground. The column contents of CH₄, CO₂, N₂O, CO, H₂, and O₃ could be retrieved. Spectral intervals for 25 different trace gases for the space mission have been identified and their retrieval accuracies were computed. The analysis shows, that with MIRIAM the lateral and vertical distribution of many trace gases can be analyzed as well as their long term variations.     

Ozone Temporal Variability in the Subarctic Region: Comparison of Satellite Measurements with Numerical Simulations

Fourier and wavelet spectra of time series for the ozone column abundance in the atmospheric 0–25 and 25–60 km layers are analyzed from SBUV satellite observations and from numerical simulations based on the RSHU and EMAC models. The analysis uses datasets for three subarctic locations (St. Petersburg, Harestua, and Kiruna) for 2000–2014. The Fourier and wavelet spectra show periodicities in the range from ~10 days to ~10 years and from ~1 day to ~2 years, respectively. The comparison of the spectra shows overall agreement between the observational and modeled datasets. However, the analysis has revealed differences both between the measurements and the models and between the models themselves. The differences primarily concern the Rossby wave period region and the 11-year and semiannual periodicities. Possible reasons are given for the differences between the models and the measurements.