Quartz-enhanced photoacoutic spectroscopy (QEPAS) was firstly proposed at 2002 by Kosterev. Just ten years past, the technique has been applied to the broad fields, and significait breakthroughs were achieved. The latest research progress of technique was introduced to provide the reference for the QEPAS researchers in relevant fields.

The molecular absorption region has a great advantage on space target detection from the altitude of satellite. The background radiation of the molecular absorption band in infrared region was calculated using the moderate spectral resolution radiative transport model MODTRAN5 at different spectral resolutions. All resolution results of three absorption bands were convolved with the same spectral response function to make an intercomparison and the results show that: for the 4.3 μm region the maximum relative deviation exceeded 10% and the 0.2 cm-1 spectral resolution results had an excellent agreement with the line-by-line calculation; the relative deviation between high and low resolution is rather small at 3.2 μm and 2.7 μm region; the maximum deviation at 2.7 μm region was below 5%. Further intercomparison was carried out between the deviation of MODTRAN4 and MODTRAN5 at 1 cm-1, 5 cm-1 spectral resolution respectively and the line-by-line calculation and the results show that the low resolution MODTRAN5 radiation calculation may result in considerable bias at 4.3 μm region.

The atmospheric coherence length instrument was used to measure atmospheric coherence length for several months in mountainous area of South China. The results show that atmospheric coherence length of November is greater than that of October and December. The measurement results in night are more complex than those of daytime. The results in latter half of the night are greater than those of first half of the night. The frequency results show that central value of atmospheric coherence length in daytime is 8.5 cm and central value of atmospheric coherence length in night is 13.0 cm. The frequency results of distributing atmospheric coherence length in daytime is mainly center around 6 cm to 12 cm, and the same value in night is mainly center around 10 cm to 18 cm. The mean value of atmospheric coherence length in night is apparently larger than that of daytime. Even the thin layer in surface layer can have much influence on turbulence of the whole atmosphere especially by day.

The average annual number of fog days in the past 50 years, and the daily fog observations in the past 10 years in Hefei were selected to analyze the area fog spatial and temporal characteristics. Detailed grid, ECMWF data for interpretation and application of autumn and winter fog are used. The results showed that: Hefei fog appeared slowly linear increase, accounting for 20% fog abnormal years; 91% fog occurring time during the morning hours 04:00～10:00, radiation fog accounting for 94%. In November and January, fog and dense fog occured most frequently. Foggy days in winter are more than that in summer, but in December is less fog. Fog and dense fog in Feixi County stations occured most frequently. Temperature, humidity, wind speed, cloud cover and radiation fog has good correspondence.

With the development of global industrialization and increasing population, the atmosphere environment has been a serious problem. NO2 and aerosols play an important role in atmosphere chemistry. Ground-based multi axis differential optical absorption spectroscopy(MAX-DOAS) has been successfully applied in the measurements of the trace gas vertical column density(VCD) and aerosol optical depth(AOD). NO2 VCD and AOD were measured based on MAX-DOAS in Hefei City during the open stalk burning period. NO2 VCD was compared with the result of OMI, and results of AOD was compared with sunphometer(CE318). It showed that NO2 concentration measured by MAX-DOAS was 1.9 times higher than the result of Ozone Monitoring Instrument(OMI), and both instruments had good accordance during clear days. The correlation coefficient between AOD measured by MAX-DOAS and that by CE318 is larger than 0.9.

Sulfate and nitrate as important components of atmospheric particulates water-soluble components have important effects on climate and human health, thus realization of the fast quantitative detection has important scientific significance. The one-component aqueous solution of sulfate and nitrate were analyzed by attenuated total reflection Fourier transform infrared spectrum (FTIR/ATR). The result shows that the linear relation is good and the correlation coefficients are 0.9982 and 0.9997, respectively. The mixture of sulfate and nitrate was prepared using the orthogonal experiment design, the quantitative analyses of sulfate and nitrate were carried out by one-dimensional linear regression and multivariate calibration based on partial least squares (PLS) model respectively. The result shows that the prediction accuracy of sulfate by one-dimensional linear regression is better than the prediction accuracy of sulfate by multivariate calibration and the average relative error of predictive value is 2.6%, the prediction accuracy of nitrate by multivariate calibration is better than the prediction accuracy of sulfate by one-dimensional linear regression and the average relative error of predictive value is 2.31%. The method is rapid and simple and it is the foundation of the quantitative analysis of sulfate and nitrate in aerosol aqueous solution at the same time.

Because of the advantages of high selectivity, high resolution and fast speed, the tunable diode laser absorption spectroscopy(TDLAS) technology is widely used in such aspects as environmental testing and industrial process testing. The Lorentz linetype fitting, the principle and implementation steps of Levenberg-Marquardt algorithm, and the realization researches of Lorentz linetype fitting of absorption lines based on Levenberg-Marquardt algorithm are investigated. After concentration inversion of six group different concentrations of CO2 standard gas, the correlation coefficient between inversion concentration and the actual concentration is 0.9928. The result shows that Lorentz linetype fitting can invert gas concentration accurately, which has practical guiding significance for concentration inversion in the TDLAS technology.

To carry out a computationally fast and accurate atmospheric correction based on polarized image, an algorithm of atmospheric correction was proposed by combining the intensity and polarization degree information of polarized light. Firstly, based on the vectorized linearized discrete ordinate radiative transfer(VLIDORT) model, a look-up tables (LUTs) which is composed of observation geometry, atmospheric parameters, aerosol model, and surface polarization characteristic were set up. Then the atmospheric correction was carried out through the look-up tables by interpolation method. The experimental results show that the algorithm has a good effect on foggydays, which is a good way to remove the negative impact of fog. After the correction, the image information entropy increased by 0.44 and the contrast increased by 41.84%. And then it is proved that the algorithm can restore the target’s intensity and degree of polarization. It also has a good performance on enhancing the image amount of information and contrast.

In 2008, Stephen put forward a new brightness temperature function and the expression is purely empirical. However, it does not require knowledge of the total amount of atmospheric water vapor in retrieval of cloud-base height. Systematical investigation of the changes of the cloud-based infrared brightness temperature Tb as the zenith angle, water vapor, cloud, aerosol, visibility and other meteorological conditions is performed by using the SBDART model and Stephen brightness temperature function, and the error is analyzed. The results show that zenith angle, water vapor, cloud, aerosol and visibility less than 5 km have a very important influence on Tb. Under different meteorological conditions, the simulation results of Stephen function are similar to SBDART model. Therefore, Stephen brightness temperature function can be used to simulate the cloud-base brightness temperature.

Due to the need of meteorological parameter in remote sensor calibration procedure, National centers for Environmental Prediction(NCEP) FNL data is adopted as the source of meteorological information. The characteristics, involving information, decoding and application algorithms of FNL data are introduced. A FNL data processing and analysis code is programmed based on VC++6.0 on Windows operationing system through which the meteorological parameters like temperature, pressure and ozone of a corresponding calibration site are analyzed. It is proved that the results are of high reliability that could be used as the input parameters of calibration. Rayleigh optical depth, water vapor and ozone optical depth are calculated based on the results. The next direction of investigation is outlined.