Brd Algorithm, Satellite Retrieval Of Sulfur Dioxide

Sulfur dioxide is one of the colorless and irritant trace gases,and its concentration in atmosphere is an important index for air quality.It plays very important role in global environment change study.At present,atmospheric composition monitoring instruments boarded in satellite and remote sensing technology of sulfur dioxide have got the advance rapidly.GOME(Global Ozone Monitoring Experiment) and SICAMACHY(Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY) of Europe,TOMS(Total Ozone Mapping Spectrometer) and OMI(Ozone Monitoring Instrument) of America have successively got the detection ablility of sulfur dioxide.At first,the main atmospheric composition monitoring instruments boarded in Erupean and American satellite have been systematic reviewed,including the analysis of the instrument detection ablility of sulfur dioxide from aspects of spectral resolution,spatial resolutin and the duration of global coverage.Then the main retrieval algorithm of sulfur dioxide,like DOAS(Difference Optical Absorption Spectroscopy),BRD(Band Residual Difference),LF(Linear Fit) algorithm of sulfur dioxide,have been compared and analyzed. The fluctuant change of sulfur dioxide absorption at Hugging band(305-315nm) has been utilized by BRD algorithm.Combination of adjacent band pairs,which one is at wave peak of absorption and the other one is at wave through of absorption,not only removes the infulence of scattering but also has high detection ablility of small change of low sulfur dioxide concertrain.So compared with other two algorithm,BRD algorithm has ability and advantage to detect sulfur dioxide ofanthropogenic pollution.In BRD algorithm,AMF(Air mass factor) is the main factor affecting retrieval precision of sulfur dioxide.Many factors can affect AMF,including LER(Lambertian effective reflectivity),geometric condition of satellite measuement and ozone column amounts and so on.AMF sensitivity experiments were carried out by TOMRAD forward model.Many affecting factors of AMF were simulated and the order of affecting factors have been achieved. Based on the two important affecting factors(ozone amounts and surface reflectivity), three-dimensional look up tables has been built to improve sulfur dioxide retrieval precision.The first estimated ozone and LER are used as parameter in BRD algorithm.They are computed by ozone algorithm of TOMS in this paper,and the computing results is consistent with OMI official products.Obtaining the first estimated ozone and LER is a basis for retrieval of sulfur dioxide by BRD algorithm.Based on BRD algorithm,a set of program for retrieving sulfur dioxide in atmosphere has been successfully developed.Because of retrieval biases resulting from nonperfect instrument calibration as well as from forward model simulations,the empirically correction has been tried in this paper.Average residual is calculated by daily residual of global equatorial nonpolluted area,and retrieval biases of sulfur dioxide was reduced by pixel residual subtracting average residual.Sulfur dioxide retrieved by OMI L1B data,was compared with sulfur dioxide from OMI L2 products,which proves the retrieval results are consistent with American official products.Based on developed retrieval program in this paper,the distribution of sulfur dioxide in China area and two cases of volcanic eruptions in 2008 were analysised.The results shows the high concerntration area of sulfur dioxide in China are mainly at northern China,eastern China,Sichuan Basin.The image of sulfur dioxide from two volcanic eruptions in 2008 shows the strengths of volcanic eruption,moving trace of smoke following winds,and duration of smoke in atmosphere.Based on this work,retrieval method of sulfur dioxide was applied on observation data from TOU(Total Ozone Units) instrument boarded on FY-3 to try to retrieve sulfur dioxide of volcanic eruptions.The result shows observation data of TOU can be used to obtain the change of high sulfur dioxide concertration from volcanic eruptions.The retrieval results were compared with sulfur dioxide from OMI L2 products,showing consistency in spatial distribution and quantity trend,preliminary approving that TOU instrument has an considerable ability for detection of sulfur dioxide from volcanic eruption.But compared with the detection results of foreign instruments,spectral resolution and detection sensitivity of TOU has limitation.Quantitatively remote sensing of sulfur dioxide in atmosphere by TOU has some uncertainty and limitation.The rational suggetion about TOU instrument is that moving 312.6nm channel to the postion of 311.9nm to improving the detection ablility of sulfur dioxide in condition of not affecting the detection of zone.It will lay a foundation for improvement of parameters of atmospheric composition monitoring boarded in subsequent FY-3 satellite.There are mainly four article feature of this paper:1) the main present international instruments and method of satellite remote sensing of sulfur dioxide;2) forward modeling has been analyzed for physical parameters of affecting AMF and the influence of the main physical parameter to retrieval precison of sulfur dioxide;3) Based on BRD algorithm, independent development of retrieval program of sulfur dioxide has been tried.Observation data of American OMI and Chinese TOU also be processed;4) Acorrding to the results of this paper,some suggestions have been given to improving the channel design of TOU instrument. Above research lays a solid foundation for developing the remote sensing detection ablility of Chinsese atmospheric compsition monitoring instrument boarded in FY satellite.