Atmospheric motion vectors (AMV) in cloud-free region can not be obtained with current operational cloud-motion
tracking and water-vapor channel algorithms. The motivation of this study is to introduce a supplementary algorithm in
order to work out the low-level AMVs in the clear area with FY-2E long wave, window (10.3~11.5, 11.6~12.8 μm)
channel imagery. It has been shown that the weak signals indicating water vapor in “cloud-free region” can be extracted
from FY-2E long wave infrared imagery and may be used as tracers for atmospheric motion vectors. The algorithm,
named as Second Order difference method, has been raised in order to weaken the surface temperature interference to the
weak signals of water vapor in “cloud-free region” by means of split window and temporal difference calculations. The
results from theory analysis and cases study show that this method can make up for the wind data in regions lack of
cloud but rich of water vapor and comparison between the wind vectors from this method and the NCEP reanalysis data
shows a good consistency.
The precipitation radar (PR) on the Tropical Rainfall Measuring Mission (TRMM) satellite has high vertical resolution, and ground radar (GR) has relatively good capability to detect weak precipitation and relatively good horizontal resolution. The joint utilization of PR and GR will be an important factor in maximizing the benefit to be reaped from both instruments. In this paper, we will blend the PR data and GR reflectivity in Nanjing, China based on image fusion algorithm. Integrating PR and GR mainly includes following steps: spatial-temporal matchup of PR and GR data, image fusion algorithms selection and quality evaluation of the fused image.
Refractivity happens due to stratification in the lower boundary layer over oceans due to variability of moisture,
temperature, wind and sea surface temperature which collectively may lead to generate evaporation duct. The
evaporation duct has a significant impact on the spread of electromagnetic waves in the atmosphere over oceans
both from the meteorological and military point of view. This ducting sometimes supports normal propagation of
radar signals and sometimes may cause distortion and attenuation of signals depending on the height of evaporation
duct. This leads to over-estimation and under-estimation of rainfall by weather radar meteorologically and for other
targets militarily. The aim of this study was not only to locate evaporation duct height but also to check the
efficiency of Weather Research and Forecasting Model (WRF) and Babin’s model so that results may be used in
applying correction measures for precise identification of targets by radar. In this study by utilizing the high vertical
resolution of WRF for the simulation of different meteorological parameters, the Babin’s method was used for
calculating the evaporation duct height over South China Sea for the two months, April and July. Very clear duct
heights were calculated at different areas over sea in different time domains. Study reveals that maximum height
existed in the month of April although July was rich with different EDHs in different regions in contrast to April. It
was found that in most of the cases EDH was higher or maximum when relative humidity was comparatively lower
and air temperature and wind speed were comparatively higher. This study paves a way for futuristic study of
evaporation duct monitoring and forecasting by assimilation of remote sensing data especially through that of Geostationary
satellites by incorporating verification measures from radar.
Three-fold restriction technique is used to determine the standard deviation of the error in the total-ozone content
obtained from the three independent data resources such as ground-based station data, TOMS (Total Ozone Mapping
Spectrophotometer) and GOME (The Global Ozone Monitoring Experiment) in 1995-2004. The results show that, in
general, the accuracy of TOMS V8 data is the best and that of ground-based observations is the worst. Since the
ground-based observations can be classified into 3 types according to the equipment principles such as Filter, Brewer
and Dobson, the standard deviation of the errors for the 3 types of ground data are also calculated with the 3-fold
restriction technique and it has been found that the Filter has the largest error, the Brewer is the second, and the Dobson
is the least. The data quality at Shiangher Dobson Station of China is better than either TOMS or GOME. The data
quality at Waliguan Brewer Station of China is better than TOMS, but worse than GOME. The error in TOMS V8 is
evidently less than in TOMS V7 because of the algorithm amelioration of TOMS V8 over TOMS V7.
The relationship between attenuation coefficient, k, and radar reflectivity factor, Z, as well as that between Z and rainfall rate, I, is influenced by the shape of precipitating raindrops and the orientation of their rotatory axes respect to the polarization direction of the incident radar wave. Provided that the orientation of rotatory axes of poly-disperse small spheroid particles is known, correctable thickness of radar echo for attenuation depends mainly on rainfall rate. The heavier the rainfall rate, the thinner the correctable thickness. For an 80mm/hour precipitation uniformly distributed along a radial direction, correctable thickness of radar echo is more than 120km for 5.6cm wavelength and about 50km for 3.2cm if correction algorithm R2 or R3 is used. Orientation information is critically important during attenuation correction. Right k-Z relationship must be coupled with right orientation status.
In the paper, a set for measuring terrain atmospheric visibility is put forward. Principle of the set operating is discussed. The processing of the signals in the set is analyzed. Optical fiber beams are utilized. The fiber beams act as both a field stop and a spatial filter. The errors caused by the limit of the end faces of fiber are smaller than 3.0 % in the set.The errors can be eliminated by means of adjusting the instrument constant of the set. The effect by the forward scattered light on the measuring of transmission light is cut down due to the spatial filter. The measuring of angular scattering coefficient is not affected by the change in the intensity of probing beam, and change in the properties ofpropagation by the depositing of dust. The set can be used in the real-time measuring of visibility. The relative error is about 3.7 % between the total scattering coefficient and that by the transmission light method.
Solar eclipse would result in a shadow on the earth which might be observed by orbiting satellite and shown in a satellite image. Even though this rarely happens, a sequence of images contaminated by solar eclipse has been obtained from a geostationary meteorological satellite. The paper describes how the shadows in the imagery series have been eliminated with image processing technique. A 2D model is designed to simulate the shape and variation of the solar eclipse shadow so that the shadow can be cleared to a certain extent. Cloud tracking and pattern recognition techniques are also applied in verifying the algorithm.
The effects of the hydrometeor spectra and water-coated ice spheres in a precipitating cloud on radiation transfer has been studied in a numerical experiment with an algorithm for analytical solution to microwave radiance based on the Eddington approximation. The results have shown that radiant fluxes at some levels in the cloud would change if either the size spectrum changes or some of the ice spheres are coated with liquid water. Nevertheless, whether the variation can be reflected in out-going brightness temperatures at the earth's surface and cloud top depends on rainfall rate, wavelength, size spectrum of water-coated ice spheres, and the thickness of the coat. Radiation transfer and out-going brightness temperatures at 6.6, 10.7 and 18 GHz are influenced more than at higher frequencies.
Expressions for calculating the attenuation cross sections of poly-disperse, small spheroids, whose rotatory axes are in specific status, have been derived from a universal formula for calculating the attenuation cross section of a particle of arbitrary shape. Attenuation cross sections of liquid, ice, and spongy spheroidal droplets in different size and eccentricity at different wave lengths have been computed and analyzed.
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