基于大气光鲁棒估计的无人机图像去雾方法

针对无人机(UAV)获取的图像易受雾、霾等天气影响导致图像质量降低的问题,本文提出一种基于大气光鲁棒估计的无人机图像去雾方法。首先,选取具有不同表面反照率的像素块,得到各个图像块的像素直线,利用各条像素直线与大气光共面的性质,估计得到大气光的方向;然后,利用无人机对地成像时图像各像素点的景深相似的特点,定义了图像的全局透射率,通过全局透射率和各像素直线在大气光方向上的投影计算得到大气光幅度;最后,通过对雾天图像模型进行变换得到无雾图像。为使本文方法适用于不同类型的图像,采用了自动调整图像块尺寸和条件阈值等措施来提高方法的鲁棒性。通过真实无人机图像的去雾实验证明,相比现有的图像去雾方法,本文方法在去雾的视觉效果和客观评价指标上都有较大的提升。

Vegetation Feedback at the Mid-Pliocene

A global atmospheric general circulation model and an asynchronously coupled global atmosphere-biome model are used to simulate vegetation feedback at the mid-Pliocene approximately 3.3 to 3.0 million years ago.For that period,the simulated vegetation differed from present conditions at 62％ of the global ice-free land surface.Vegetation feedback had little overall impact on the global climate of the mid-Pliocene.At the regional scale,however,the interactive vegetation led to statistically significant increases in annual temperature over Greenland,the high latitudes of North America,the mid-high latitudes of eastern Eurasia,and westem Tibet,and reductions in most of the land areas at low latitudes,owing to vegetation-induced changes in surface albedo.

Self-similarity Based Editing of 3D Surface Textures Using Height and Albedo Maps

This paper presents an inexpensive method for self-similarity based editing of real-world 3D surface textures by using height and albedo maps. Unlike self-similarity based 2D texture editing approaches which only make changes to pixel color or inten- sity values, this technique also allows surface geometry and reflectance of the captured 3D surface textures to be edited and relit us- ing illumination conditions and viewing angles that differ from those of the original. A single editing operation at a given location affects all similar areas and produces changes on all images of the sample rendered under different conditions. Since surface height and albedo maps can be used to describe seabed topography and geologic features, which play important roles in many oceanic proc- esses, the proposed method can be effectively employed in applications regarding visualization and simulation of oceanic phenom- ena.

Three-year changes of surface albedo of degraded grassland and cropland surfaces in a semiarid area

Diurnal, seasonal and interannual variations of surface albedo of degraded grassland and cropland surfaces at a semiarid area of Tognyu have been investigated based on the continuous three years observational data from 2003 to 2005. The changes of surface albedo with solar elevation angle and soil moisture have been discussed also. It has been found that surface albedo has almost the same diurnal and seasonal variations on degraded grassland and cropland surfaces in the semiarid area, while sur- face albedo is large in winter and small in summer. The diurnal variation of the surface albedo has re- lationship with the weather condition. The diurnal cycle of the surface albedo likes the "U" shape curve in sunny day, while it is low-high after the rain, and high-low after the snow. The surface albedo has large variation in cloudy day, while it has no any variation in overcast day. The large difference of the surface albedo can be 0.04 in winter between two land surfaces, because the snow has large effects on the surface albedo in winter. The rainfall is an important factor in summer on the surface albedo, while the difference of the surface albedo is 0.01 only between two land surfaces. The differences of the surface albedo can also be 0.04 in autumn due to vegetation growing. The seasonal-average surface albeo from 2003―2005 is 0.25, 0.22, 0.24, 0.32 respectively in spring, summer, autumn and winter on the degraded grassland surface,while it is 0.25, 0.21, 0.22, 0.33 respectively in spring, summer, autumn and winter on the cropland surface. The surface albedo becomes smaller with the increase of solar elevation angle. When the solar elevation angle is greater than 40°, the surface albedo changes very little and tends to be a constant. The surface albedo has negative exponent functions with soil moisture in the growing season.

Ozone profiles retrieval from SCIAMACHY Chappuis-Wulf limb scattered spectra using MART

The Scanning Imaging Absorption spectroMeter for Atmospheric ChartographY(SCIAMACHY) instrument,launched on the Envisat satellite in March 2002,measures the earthshine radiance,simultaneously from the ultraviolet(UV) to the near infrared(NIR),in the three viewing geometries:nadir,limb,and occultation.These measurements are used to retrieve both the total amount and vertical profiles of a large number of atmospheric constituents.In this paper,stratospheric ozone profiles between 15 and 40 km altitude are retrieved on 3 km grids from SCIAMACHY limb scattered radiance in the Chappuis-Wulf band.The study employs a new multiplicative algebraic reconstruction technique(MART) coupled with the radiative transfer model SCIATRAN.This technique is outstanding in that more than one measurement vector element can be used to retrieve the ozone density at any altitude.Furthermore,it is straightforward to understand,easy to implement and likely to produce stable results.Radiance normalization and wavelength pairing is applied to radiance as an intermediate step,using the wavelengths 525 nm,600 nm and 675 nm.The sensitivity of ozone retrieval by this method to tangent altitude pointing,surface albedo,aerosol and cloud parameters is studied,and the results show that the retrieval impact due to tangent altitude pointing bias is the biggest up to 75% with 1 km shift,and the impact of albedo is limited within 5%.The effect of boundary visibility and cloud parameters can be ignored since their impact is too small.The effectiveness of the retrieval is demonstrated using a set of coincident SCIAMACHY products at Hefei that shows a mean bias of less than 12% between 15 and 40 km,and with a better accuracy of 5% from 16 to 36 km.

火星的业余观测（二）

火星轨道位于地球之外，从地球上看火星相位角可达45°。冲前，火星的相位缺损，火面上的明暗线位于火星视面的西边；冲后，则在火星视面的东边。火星自西向东自转，倒像望远镜中的火星视面的西边(左)是火星周日运动的前进方向。