High power femtosecond laser pulses undergo nonlinear filamentation in the atmosphere, with supercontinuum generation from the UV to the IR. Further more, the intense filaments can strongly interact with aerosols, stimulating nonlinear emissions like multiphoton-excited fluorescence or plasma emission. The white-light lidar, based on the properties of femtosecond laser pulses propagation, provides novel and multiple detection techniques. A brief review of the principle and applications of white-light lidar is presented. The theory about filamentation and structure of lidar are expounded. Characteristics of main white-light lidar systems reported so far in the world are introduced. The detection approaches and application examples are presented. In the end, perspectives for white-light lidar are analyzed.

Simulating fractional Brownian motion signal is added to the ideal temperature ramp structure. Using the conditional sample technique, and Donoho and Johnostone threshold method, the ramp signal is successfully identified and separated. This method is applied to the actual atmospheric temperature data. The analysis shows that there are the temperature ramp structure in actual atmosphere, and the period is about 30 seconds. Under different stability condition, the form of ramp structure may be different. And the wavelet transform can identify the temperature ramp structure efficiently.

Parameterization of water cloud and ice cloud optical properties included in the libRadtran software package are introduced. These optical properties include single-scattering albedo, extinction coefficient and asymmetry factor. Then simulations for water cloud and ice cloud at 0.65 m, 1.64 m and 2.13 m are conducted. Comparison with SBDART simulation shows that there are similar results in the visible region and significant differences in the solar near-infrared region. Parameterization of ice cloud for various particle habits in the libRadtran have better approximation than Mie calculation for sphere ice particles used in the SBDART. A pre-computed look-up table of the bidirectional reflection in retrieving ice clouds optical thickness and effective particle radius can be improved by libRadtran.

The steady broad band radiation signal, from the infrared radiation source, passed through a collimator and propogated atmosphere. It was received by the ABB Bomem MR 170 FTIR spectrometer, the detection system. Based on the spectrometer, a set of surface atmospheric infrared transmittance measurement system in open air was constructed. In Hefei area, the system was used to measure actual atmospheric transmittance. Compared the measured results with MODTRAN outputs, the correlation coefficients are bigger than 0.9, but there are great differences at regions from 2500 cm-1 to 3000 cm-1 and from 4400 cm-1 to 4800 cm-1. By analyzing the changes of water vapor concentration and the transmittance of 2400 cm-1 along with time, the results indicate that the changes of water vapor parameter of local area environment take effect on the transmittance of atmospheric model.

By means of investigating the echo data on each July from 2003 to 2006 observed by Doppler weather radar in Hefei, the merger regulation of convective cloud in Dabie Mountains was statistically summarized, and a typical merger process was analyzed. The results show that: (1) according to many synoptic systems affecting Anhui, under the background of the low trough of North China, the probability of merger in Dabie Mountains is maximum; (2) the merger generally occurs during the afternoon; (3) after the merger, the development probability of radar echo is more than 70% in area and 66.3% in intensity; the lifetime mainly concentrates on 90 240 minutes.

In the retrieval of atmospheric trace-gas concentrations, it’s a widely used method to fit the calculated reference spectra to the measured spectra with least-squares methods. However, because of inaccuracies of the grating position, thermal changes in the spectrometer, and resolution differences between the two spectra, there is a spectral misalignment between the measured spectra and the reference spectra, that is the measured spectra may be shifted or stretched/squeezed. These misalignments will affect the accuracy of the retrieval. An algorithm for the shift-and-squeeze spectral correction in the process of the retrieval is introduced and the concentration error caused by spectral shift under different resolutions is calculated.

Differential optical absorption spectroscopy technique (DOAS) has been used to measure trace gases in the atmosphere. This technique uses the gases strongly structured absorption of radiation in the UV and visible spectral range to retrieve their concentration. The measurement on monocyclic aromatic hydrocarbons (MAHC) was carried out using the portable DOAS system developed by Anhui Institute of Optics and Fine Mechanics. The retrieval method for measuring MAHC with the system and the effect of relative retrieval and absolute retrieval methods to remove the interference of O were analyzed. The detect limits of portable DOAS are given. The results demonstrate that the portable DOAS system can be applied to polluted sources of MAHC and polluted gases leak monitoring.

The parameters such as sensible heat flux, latent heat flux, soil heat flux, radiation of long-and-short wavelength and the density of CO are separately measured with open-path eddy correlation system, HFP01 heat flux plate, the sensor of CNR1 net radiation and CO /H O analyzer(LI7500). Statics and analysis indicate that the largest value of net radiation at noon in clear days is up to 850 W/m during the period of observation in June, 2008, and 500 W/m2 in November. The reflectivity is 0.148 in summer, and 0.199 in winter. The latent heat flux and sensible heat flux are more or less the same in summer and winter, with the max value between 80 W/m2 and 220 W/m2. The energy equation is obviously lopsided, and the day-time rate of closure increasing with wind speed is basically between 0.4 and 1. The annual statics of the density of CO indicates that the diurnal variation characteristics of CO gas density are obvious during the four seasons, and the range of the density is between 640 W/m2 and 770 W/m3.

Photodetectors are widely used in high technology field. Quantum noise is a main noise source of photodetector, and as an important factor in error analysis, it affects and decides detecting sensitivity. The difference and relation between noise and standard deviation are discussed. Based on the analysis of quantum noise sources, it is checked that the emitted photoelectrons have a Poisson distribution, but the multiplied photoelectrons do not obey Poisson statistics. Noise scale factor is introduced and used to describe and process the standard deviation of photoelectrons of photodetector.

Sensible and latent heat fluxes exchange between surface and atmosphere is a hot topic in eco-environmental research recent years. A software using large aperture scintillometer (LAS) to measure sensible heat fluxes and transverse wind speed is introduced. To meet demands of the data acquisition and disposal of LAS for measuring sensible fluxes and wind speed, the software for the real-time data collection is designed using PCI8340, a data acquisition card, disposing and displaying signals of LAS on Windows platform. It is convenient for persons to get the experimental results quickly and exactly. In addition, it can run automatically because of the data validity check module of the software.

To measure underwater acoustic signals with laser technology, the principle and hardware structure are presented, including photodetector circuit, pre-amplifier circuit, high-pass filter circuit, after-class amplifier circuit, low-pass filter circuit, notch filter circuit of 50 Hz, serial communication circuit, memory expansion circuit, etc. The control and calculating circuit are designed based on digital signal processor TMS320LF2407A, and virtual machines are used to achieve real-time display of signal detection. Experimental results show that the system can detect underwater acoustic signals well.