The performance of the weather research and forecasting (WRF) model relies on the accuracy of the initial field provided by data assimilation. The initial field usually contains large uncertainties, especially for regions where observations are sparse or lacking. Assimilating additional observations is an efficient way to reduce this uncertainty. The moderate resolution imaging spectroradiometer (MODIS) is one of the most critical data sources of various indirect assimilating applications due to its wide swath and remarkable quality. Therefore, assimilating MODIS data into WRF data assimilation (WRFDA) system is meaningful to improve the accuracy of weather forecasts. This study developed a module to directly assimilate the MODIS radiances into the WRFDA based on the 3-D variational data assimilation method and community radiative transfer model. An assimilation experiment was carried out on August 2014, from which the background field has been relatively improved. Specifically, the improvement of the temperature, humidity, and wind speed at the near surface layer is about 0.2°C, 1.2%, and 0.2 m/s, respectively. Additional capabilities and increased potential of MODIS data assimilation based on WRFDA need to be further investigated and tested under various conditions and applications.
Clouds’ macrophysical characteristics play an important role in the climate system and dramatically vary because of the diverse climatic and geographic factors in China. We analyze cloud macrophysical characteristics and the differences between subregions in China (18°–54°N, 73°–135°E) from March 2012 to February 2015 based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, including cloud fractions, cloud vertical distribution, and cloud geometrical properties with the perspective of daytime and nighttime. We found that annual single layer, multilayer (ML), and total cloud fractions are 40.4±1.1%, 22.4±0.4%, and 62.8±1.5%, respectively, and clouds are generally located between 6 and 12 km. The cloud fractions in daytime are less than that in nighttime over the south while that of Tibet shows the reverse trend. In the vertical direction, except for Tibet, the clouds in nighttime have larger spatial coverage and are higher in altitude than that in daytime. The regional average values of cloud macrophysical characteristics in the south are highest, followed successively by Tibet, north, and northwest. Cloud geometrical depth and spacing show a gradually declining trend with the increase in layers and decrease of altitude in ML cloud system.
In this paper a new technique of objects measurement based on multi-wavelength lidar system has been proposed and developed to make horizontal-path laser measurements of objects. The two or more wavelengths laser transmitter operates within and adjacent to the sensitive bands exhibited by the characteristics of each object, the result could be used to establish inversion models of the laser transmitting backscatter signals. The application value and the key techniques of the spectral lidar are analyzed. The lidar wavelength selection method is studied and a hyperspectral experiment had
been down to testify the feasibility of the theory. Also issues to approach the final goal of this new technique are discussed.
Space borne LIDAR is a fire-new method for aerosol observations, it help us to acquire the global data on the structures
and optical properties of aerosols. In this paper, a lidar ratio selection algorithm is introduced, since lidar ratio (the
aerosol extinction-to-backscatter ratio, a S ) is an important parameter for aerosol retrieval. Then we use an appropriate
retrieval algorithm for signals which is observed by a space borne backscatter lidar, after inversion the distribution state
of aerosol optical depth can be obtained. The distribution of aerosol optical depth is not only related to the earth's surface
and the geographic location of the aerosol emission, but also related to other meteorological factor. Such as turbulent,
wind gusts, hurricanes, tornadoes, and land clearing and development activities, all of these cause aerosol drift from
initial geographic location.From summer to autumn, the changing characteristic of aerosol optical depth in Central
Southern China is analyzed by retrieving the space borne lidar signal. On a short term, through analyze the aerosol
distribution, whether or how atmospheric motion influences on aerosol particle diffusion is available.
Aerosol particles are important components of the earth-atmosphere system, not only affecting atmospheric visibility of
the earth's surface from space, but also be an important element to the occurrence of cloud that aerosol particles serve as
the primary source of cloud condensation nuclei(CCN). Remote sensing of aerosol properties from space/satellite can
reveal the tendency of temporal-spatial distribution in global scale, however, whose precision can't satisfy the request of
quantitative remote sensing. Thus, in this paper proposes the method combined sunphotometer (passive measurements)
and Lidar (active remote sensing measurements) developed by Wuhan University to retrieve the aerosol optical depth.
The primary results show that the proposed method improved the precision of aerosol optical depth effectively.
Furthermore, long-term atmospheric and aerosol data could be obtained by consecutive Lidar and sunphotometer
observations. Also these data will be used for emending the existing atmospheric model and aerosol type, and make
them more compliant for China area application.
In this paper a new technique of objects measurement based on multi-wavelength lidar system has been proposed and
developed to make horizontal-path laser measurements of objects. The two or more wavelengths laser transmitter
operates within and adjacent to the sensitive bands exhibited by the characteristics of each object, the result could be
used to establish inversion models of the laser transmitting backscatter signals. The application value and the key
techniques of the spectral lidar are analyzed. The lidar wavelength selection method is studied and a hyperspectral
experiment had been down to testify the feasibility of the theory and the lidar detection is simulated. Also issues to
approach the final goal of this new technique are discussed.
Aerosol particles play important role in both global climate system and earth observation application. We have
developed a portable scanning Mie lidar, with the combination of spectrograph, active and passive earth observation
satellite data, and the ground sensor data, severe weather research and earth observation atmospheric correction work
could be conducted. To obtain more accurate aerosol information, we are developing a new multi-channel Raman lidar
system. Also we have developed a simulation model for system performance simulation and data simulation. In this
paper, the lidar system development, simulation modeling, and primary experimental work result will be described.
Aerosols have large impacts on radiative transfer through scattering and extinction, which distort the satellite signals in earth observation application. In the paper, we apply lidar for measuring aerosol signals simultaneously when earth observation satellite flyover. In this way, the aerosol influence could be removed precisely by the combination of real-time lidar data and atmospheric radiance transmission model. Here, the aerosol optical depth retrieved by lidar data is integrated into the 6S model for satellite image atmospheric correction. The primary results are shown in this paper.
Aerosol particles are important components of the earth-atmosphere system, which change the radiance balance of earth-atmosphere system by the two processes of absorption and scattering, also distort the signal of earth observation satellite. For understanding the atmospheric attenuating effect of aerosols to satellite signals, a portable Mie Lidar system is developed, which is mainly used for measuring the optical properties of aerosol. At the same time, a radiative transfer model is introduced for implementing atmospheric correction of satellite signal. The aerosol data from lidar measurement are fed into radiative transfer code, instead of the model transcendental value. The primary results are shown in this paper. Furthermore, long-term atmospheric and aerosol data could be obtained by consecutive lidar observations. Also these data will be used for emending the existing atmospheric model and make it more compliant for China area application.
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