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1.
The longwave (0-2380 cm-1) cooling rate due to water vapor in the troposphere and the stratosphere has been calculated by a new infrared transmission model in this paper. An exact scheme is used for treating the integration over wavenumber and the inhomogeneous path in the atmosphere. It is shown that the atmospheric window region (730-1200 cm-1) (mainly water vapor continuum) plays an important role in the total cooling near the surface, about 72% of the total cooling lying in this region at the height of 1 km; the CG approximation used for an inhomogeneous path is fairly applicable for calculating the cooling rate due to water vapor, with a maximum error of 0.16 K/day throughout the troposhere and the stratosphere; on the other hand, the error due to the diffusivity factor of 1.66 appears to be slightly larger near the surface. In this study, the influences on the calculation of above infrared cooling rate, of the temperature-dependence of the absorption coefficients of water vapor, the upper level cu  相似文献   

2.
A review of ten-year's practice in developing the improved simultaneous physical retrievalmethod(ISPRM)is given in the hope that some creative ideas can be drawn from it.Theimprovement upon the SPRM is associated with the under-determinedness of this ill-posed inverseproblem.In our experiment,the precondition is observed that prior information must beindependent of the satellite measurements.The well-posed retrieval theory has told us that theforward process is fundamental for the retrieval,and it is the bridge between the input of satelliteradiance and the output of retrievals.In order to obtain a better result from the forward process.the full advantage of every prior information available must be taken.It is necessary to turn the ill-posed inverse problem into the well-posed one.Then by using the Ridge regression or Bayesalgorithm to find the optimal combination among the first guess,the theoretical analogueinformation and the satellite observations,the impact of the under-determinedness of this inverseproblem on the numerical solution is minimized.  相似文献   

3.
The relationship between the radiance ratio (radiance at wavelength 450 nm to 650 nm) and aerosol optical depth (AOD) is analyzed in this paper by numerical simulation and a "LUT" (look-up table) approach is then presented for the retrieval of AOD from the radiance ratio. In this LUT approach, the AOD retrieval error depends mainly on the assumption of aerosol types. From the preliminary simulation, a typical error of 15%–20% in AOD obtained from the radiance ratio is estimated, due to neglecting changes in...  相似文献   

4.
PRECIPITABLE WATER MEASUREMENTS WITH SUN-PHOTOMETER   总被引：6，自引：0，他引：6       下载免费PDF全文
In this paper a method is described of retrieving precipitable water from sun-photometermeasurements.The quantitative relationship between water vapor transmission and precipitablewater is established by means of LOWTRAN 7 model.Calibration of the water vapor absorptionchannel is made through a modified Langley method.The good agreement between the sun-photometer and radiosonde water vapor retrieval indicates that this method is feasible.The sun-photometer is operated at Hefei to monitor the precipitable water within one yearperiod.Characteristics of both diurnal evolution and within-one-year variation of the precipitablewater and their relation with synoptic system as well as surface dew-point temperature arepresented and analyzed.Errors in the retrieved precipitable water from the sun-photometermeasurements are also calculated and discussed.  相似文献   

5.
A new method applying an artificial neural network （ANN） to retrieve water vapor profiles in the troposphere is presented. In this paper, a fully-connected, three-layer network based on the backpropagation algorithm is constructed. Month, latitude, altitude and bending angle are chosen as the input vectors and water vapor pressure as the output vector. There are 130 groups of occultation measurements from June to November 2002 in the dataset. Seventy pairs of bending angles and water vapor pressure profiles are used to train the ANN, and the sixty remaining pairs of profiles are applied to the validation of the retrieval. By comparing the retrieved profiles with the corresponding ones from the Information System and Data Center of the Challenging Mini-Satellite Payload for Geoscientific Research and Application （CHAMP-ISDC）, it can be concluded that the ANN is relatively convenient and accurate. Its results can be provided as the first guess for the iterative methods or the non-linear optimal estimation inverse method.  相似文献   

6.
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7.
An adjoint sensitivity analysis of one mesoscale low on the mei-yu Front is presented in this paper. The sensitivity gradient of simulation error dry energy with respect to initial analysis is calculated. And after verifying the ability of a tangent linear and adjoint model to describe small perturbations in the nonlinear model, the sensitivity gradient analysis is implemented in detail. The sensitivity gradient with respect to different physical fields are not uniform in intensity, simulation error is most sensitive to the vapor mixed ratio. The localization and consistency are obvious characters of horizontal distribution of the sensitivity gradient, which is useful for the practical implementation of adaptive observation. The sensitivity region tilts to the northwest with height increasing; the singular vector calculation proves that this tilting characterizes a quick-growing structure, which denotes that using the leading singular vectors to decide the adaptive observation region is proper. When connected with simulation of a mesoscale low on the mei-yu Front, the sensitivity gradient has the following physical characters： the obvious sensitive region is mesoscale, concentrated in the middle-upper troposphere, and locates around the key system; and the sensitivity gradient of different physical fields correlates dynamically.  相似文献   

8.
This study investigates the use of dynamic a priori error information according to atmospheric moistness and the use of quality controls in temperature and water vapor profile retrievals from hyperspectral infrared (IR) sounders. Temperature and water vapor profiles are retrieved from Atmospheric InfraRed Sounder (AIRS) radiance measurements by applying a physical iterative method using regression retrieval as the first guess. Based on the dependency of first-guess errors on the degree of atmospheric moistness, the a priori first-guess errors classified by total precipitable water (TPW) are applied in the AIRS physical retrieval procedure. Compared to the retrieval results from a fixed a priori error, boundary layer moisture retrievals appear to be improved via TPW classification of a priori first-guess errors. Six quality control (QC) tests, which check non-converged or bad retrievals, large residuals, high terrain and desert areas, and large temperature and moisture deviations from the first guess regression retrieval, are also applied in the AIRS physical retrievals. Significantly large errors are found for the retrievals rejected by these six QCs, and the retrieval errors are substantially reduced via QC over land, which suggest the usefulness and high impact of the QCs, especially over land. In conclusion, the use of dynamic a priori error information according to atmospheric moistness, and the use of appropriate QCs dealing with the geographical information and the deviation from the first-guess as well as the conventional inverse performance are suggested to improve temperature and moisture retrievals and their applications.  相似文献   

9.
This paper presents an analysis of a technique for retrieving upper tropospheric relative humidity through the GMS-5 satellite‘s 6.7-micron water vapor channel brightness temperature. NCEP analysis shows that a critical assumption of the retrieval theory, namely the constant temperature lapse rate,matches only in the tropical atmosphere. By statistical analyses of brightness temperature simulated by a radiative transfer model and of relative humidity, we examine the effect of lapse rate on this retrieval method and obtain retrieval parameters and error estimates applicable to the GMS-5 satellite over East Asia. If the retrieval parameters are properly chosen, the relative error of retrieving the upper tropospheric relative humidity in this region is less than 10%, and if applied to the low-latitude summer atmosphere, it is less than 5%.  相似文献   

10.
Li Jun 《大气科学进展》1994,11(4):421-426
Linearization of Radiative Transfer Equation (RTE) is the key step in physical retrieval of atmospheric temperature and moisture profiles from InfRared (IR) sounder observations. In this paper, the successive forms of temperature and water vapor mixing ratio component weighting functions are derived by applying one term variation method to RTE with surface emissivity and solar reflectivity contained. Retrivals of temperature and water vapor mixing ratio profiles from simulated Atmospheric Infrared Sounder (AIRS) observations with surface emissivity and solar reflectivity are presented.  相似文献   

11.
In this paper,TOVS satellite data are used through variational method on the data-sparseplateau area.Diagnoses are carried out to find a way to solve the large error problem of modelinitial field.It is put forward that TOVS retrieval data can be used to improve the initial field ofnumerical prediction model on Tibetan Plateau area.Through variational method,TOVS data areprocessed and the liability of the initial information on the plateau is improved.Diagnostic resultsconfirm further that the application of TOVS retrieval data can improve our capability to describethe dynamic system features on the plateau and the objectivity of related initial information such asthe distribution of water vapor channel and stratification stability.  相似文献   

12.
Although radar observations capture storm structures with high spatiotemporal resolutions, they are limited within the storm region after the precipitation formed. Geostationary satellites data cover the gaps in the radar network prior to the formation of the precipitation for the storms and their environment. The study explores the effects of assimilating the water vapor channel radiances from Himawari-8 data with Weather Research and Forecasting model data assimilation system(WRFDA) for a severe storm case over north China. A fast cloud detection scheme for Advanced Himawari imager(AHI)radiance is enhanced in the framework of the WRFDA system initially in this study. The bias corrections, the cloud detection for the clear-sky AHI radiance, and the observation error modeling for cloudy radiance are conducted before the data assimilation. All AHI radiance observations are fully applied without any quality control for all-sky AHI radiance data assimilation. Results show that the simulated all-sky AHI radiance fits the observations better by using the cloud dependent observation error model, further improving the cloud heights. The all-sky AHI radiance assimilation adjusts all types of hydrometeor variables, especially cloud water and precipitation snow. It is proven that assimilating all-sky AHI data improves hydrometeor specifications when verified against the radar reflectivity. Consequently, the assimilation of AHI observations under the all-sky condition has an overall improved impact on both the precipitation locations and intensity compared to the experiment with only conventional and AHI clear-sky radiance data.  相似文献   

13.
Based on a successful simulation of Typhoon Haikui (2012) using WRF (Weather Research & Forecasting) model with the WSM6 microphysics scheme, a high-resolution model output is presented and analyzed in this study. To understand the cause of the average gridded rainfall stability and increases after Haikui’s landfall, this research examines the fields of the physical terms as well as the vapor and condensate distributions and budgets, including their respective changes during the landing process. The environmental vapor supply following the typhoon landfall has no significant difference from that before the landfall. Although Haikui’s secondary circulation weakens, this circulation is not conducive to typhoon rainfall stability or increases, although the amounts of the six kinds of water substances (vapor, cloud water, cloud ice, snow, rain, and graupel) increase in the outer region of the typhoon. This reallocation of water substances is essential to the maintenance of rainfall. The six kinds of water substances are classified as vapor, clouds (cloud water and ice) and precipitation (snow, rain, and graupel) to diagnose their budgets. This sorting reveals that the changes in the budgets of different kinds of water substances, caused by the reduced mixing ratios of snow and ice, the water consumption of clouds, and the transformation of graupel, induce increased concentrations of precipitation fallout, which occur closer to the ground after typhoon landfall. In addition, this pattern is an efficient way for Haikui’s rainfall to remain stable after its landfall. Thus, the allocation and budget analyses of water substances are meaningful when forecasting the typhoon rainfall stability and increases after landfall.  相似文献   

14.
Based on the radiative transfer calculation results, three approximate expressions of the sky radiance in almucantar and its increment caused by surface albedo are presented. They are simple, but accurate enough. The dependence of the fitted aerosol scattering phase functions on refractive index is also studied, and its reasonable form is given. For Junge size distribution, the approximate equations of the phase functions with some special scattering angles are obtained. These approximate equations significantly simplify the retrieval algorithm of simultaneous determination of aerosol size distribution and its refractive index and surface albedo. This method can be realized with a microcomputer, and has been used to process and analyse the experimental data measured in Hefei of Anhui Province.  相似文献   

15.
In this study, we attempted to improve the nowcasting of GRAPES model by adjusting the model initial field through modifying the cloud water, rain water and vapor as well as revising vapor-following rain water. The results show that the model nowcasting is improved when only the cloud water and rain water are adjusted or all of the cloud water, rain water and vapor are adjusted in the initial field. The forecasting of the former （latter） approach during 0-3 （0-6） hours is significantly improved. Furthermore, for the forecast for 0-3 hours, the latter approach is better than the former. Compared with the forecasting results for which the vapor of the model initial field is adjusted by the background vapor with those by the revised vapor, the nowcasting of the revised vapor is much better than that of background vapor. Analysis of the reasons indicated that when the vapor is adjusted in the model initial field, especially when the saturated vapor is considered, the forecasting of the vapor field is significantly affected. The changed vapor field influences the circulation, which in turn improves the model forecasting of radar reflectivity and rainfall.  相似文献   

16.
Although satellite observations provide large amount of information of clouds and precipitation and play an important role in the forecast of heavy rainfall, they have not been fully taken advantage of in data assimilation of numerical weather predictions, especially those in infrared channels. Assimilating radiances is common under clear-sky conditions since it is extremely difficult to simulate infrared transmittance in cloudy sky. Based on the Global and Regional Assimilation and Prediction Enhanced System 3-dimensional variance (GRAPES-3DVar), cloud liquid water content, ice-water content and cloud cover are employed as governing variables in the assimilation system. This scheme can improve the simulation of infrared transmittance by a fast radiative transfer model for TOVS (RTTOV) and adjust the atmospheric and cloud parameters based on infrared radiance observations. In this paper, we investigate a heavy rainfall over Guangdong province on May 26, 2007, which is right after the onset of a South China Sea monsoon. In this case, channels of the Moderate Resolution Imaging Spectroradiometer (MODIS) for observing water vapor (Channel 27) and cloud top altitude (Channel 36) are selected for the assimilation. The process of heavy rainfall is simulated by the Weather Research and Forecasting (WRF) model. Our results show that the assimilated MODIS data can improve the distribution of water vapor and temperature in the first guess field and indirectly adjust the upper-level wind field. The tendency of adjustment agrees well with the satellite observations. The assimilation scheme has positive impacts on the short-range forecasting of rainstorm.  相似文献   

17.
The sky radiance and degree of polarization with multiple scattering process considered were calculated inthis paper by solving vector form radiative transfer equation iteratively. Numerical experiment for simultaneouslyretriving the size distribution (SD) and the complex refractive index (CRI) of aerosol particle was conductedwith the degree of polarization of skylight (DPS) and the library method used. It is shown from the resultsthat the real part of CRI is always sensitive to DPS. But situation is somewhat complicated for the imaginarypart of CRI. Therefore, it is expected that the real part of CRI can be retrieved from DPS and its imaginarypart should be retrieved as the particle is large in size. In this paper, seven sets of DPS measurements on 6 January,1990 in Beijing were given and the optical characteristics of aerosol were retrieved.  相似文献   

18.
Deviation exists between measured and simulated microwave radiometer sounding data. The bias results in low-accuracy atmospheric temperature and humidity profiles simulated by Back Propagation artificial neural network models. This paper evaluated a retrieving atmospheric temperature and humidity profiles method by adopting an input data adjustment-based Back Propagation artificial neural networks model. First, the sounding data acquired at a Nanjing meteorological site in June 2014 are inputted into the MonoRTM Radiative transfer model to simulate atmospheric downwelling radiance at the 22 spectral channels from 22.234GHz to 58.8GHz, and we performed a comparison and analysis of the real observed data; an adjustment model for the measured microwave radiometer sounding data was built. Second, we simulated the sounding data of the 22 channels using the sounding data acquired at the site from 2011 to 2013. Based on the simulated rightness temperature data and the sounding data, BP neural network-based models were trained for the retrieval of atmospheric temperature, water vapor density and relative humidity profiles. Finally, we applied the adjustment model to the microwave radiometer sounding data collected in July 2014, generating the corrected data. After that, we inputted the corrected data into the BP neural network regression model to predict the atmospheric temperature, vapor density and relative humidity profile at 58 high levels from 0 to 10 km. We evaluated our model’s effect by comparing its output with the real measured data and the microwave radiometer’s own second-level product. The experiments showed that the inversion model improves atmospheric temperature and humidity profile retrieval accuracy; the atmospheric temperature RMS error is between 1K and 2.0K; the water vapor density’s RMS error is between 0.2 g/m3 and 1.93g/m3; and the relative humidity’s RMS error is between 2.5% and 18.6%.  相似文献   

19.
Dynamical Framework of IAP Nine-Level Atmospheric General Circulation Model   总被引：4，自引：1，他引：3  
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20.
In this paper, Wu and Blumen's boundary layer geostrophic momentum approximation model (Wu and Blu-men, 1982) is applied to baroclinic and non-neutral PBL, the motion equations for the PBL under the geostrophic momentum approximation are solved, in which the eddy transfer coefficient is a function of the distributions of the wind and temperature. The results are compared with those in barotropic and neutral conditions with the geostrophic momentum approximation. It is found that in the baroclinic condition, the wind distribution has both the characteristics of a steady, homogeneous and baroclinic PBL and those caused by the geostrophic momentum approximation. Those in non-neutral conditions show that they retain the intrinsic characteristics for the wind in non-neutral PBL, at the same time, the effects of the large-scale advection and local variation are also included. We can predict the wind in the non-neutral and baroclinic PBL by use of the geostrophic momentum approximation when the temporal and sp  相似文献   

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