Assessment of Several Moist Adiabatic Processes Associated with Convective Energy Calculation

Several methods dealing with the moist adiabatic process are described in this paper. They are based on static energy conservation, pseudo-equivalent potential temperature conservation, the strict pseudo- adiabatic equation, and the reversible moist adiabatic process, respectively. Convective energy parame- ters, which are closely related to the moist adiabatic process and which re?ect the gravitational e?ects of condensed liquid water, are reintroduced or de?ned, including MCAPE [Modi?ed-CAPE (convective avail- able potential energy)], DCAPE (Downdraft-CAPE), and MDCAPE (Modi?ed-Downdraft-CAPE). Two real case analyses with special attention given to condensed liquid water show that the selection of moist adiabatic process does a?ect the calculated results of CAPE and the gravitational e?ects of condensed liq- uid water are not negligible in severe storms. Intercomparisons of these methods show that static energy conservation is consistent with pseudo-equivalent potential temperature conservation not only in physical properties but also in calculated results, and both are good approximations to the strict pseudo-adiabatic equation. The lapse rate linked with the reversible moist adiabatic process is relatively smaller than that linked with other moist adiabatic processes, especially when considering solidi?cation of liquid water in the reversible adiabatic process.

Diurnal Variability of Precipitation Depth Over the Tibetan Plateau and Its Surrounding Regions

The diurnal variability of precipitation depth over the Tibetan Plateau and its surrounding regions is investigated using nine years of Tropical Rainfall Measuring Mission （TRMM） precipitation radar （PR） measurements. The Tibetan Plateau, the plains area, and the East China Sea are selected as the focus regions in this study. The average precipitation depths （PD） are about 4.6 km, 5.8 km, and 5.6 km, while convective （stratiform） PDs are about 6.6 （4.5） km, 7.5 （5.7） km, and 6.0 （5.6） km over the plateau, the plains, and the ocean region, respectively. Results demonstrate a prominent PD diurnal cycle, and its diurnal phase is generally a few hours behind the surface precipitation. The spatial variation of the PD diurnal magnitude is weaker near the coastal areas than that of surface precipitation. The height of the PD diurnal peak is around 6 7 km for convective systems and 5-6 km for stratifrom systems. The dominant afternoon diurnal peak for convective PD and the flat diurnal peak for stratiform PD over the Tibetan Plateau indicate that solar diurnal forcing is the key mechanism of the PD diurnal cycle over land. In addition, the diurnal variation is obvious for shallow and deep convective systems, but not for shallow and deep stratiform systems.

The Seasonal and Interannual Variation of Diurnal Precipitation over the Tibetan Plateau and Its Downstream Regions Observed by the Tropical Rainfall Measuring Mission

Using nine years of Tropical Rainfall Measuring Mission(TRMM)2A25 data,based on the probability density function of rainfall,a comparative analysis of the diurnal cycle and its seasonal and interannual variation for convective rain,stratiform rain,and total rain is made between the Tibetan Plateau and the downstream Yangtze River basin and East China Sea.The diurnal convective rain is stronger than the diurnal stratiform rain over the Yangtze River basin,and the convective rain peaks in the afternoon when the stratiform rain maximum happens in the early morning.Convective rain and stratiform rain both peak in the early morning over the East China Sea.The diurnal total rain over the Tibetan Plateau is stronger than its downstream regions.The diurnal cycle appears quite different among the four seasons over the Yangtze River basin,and the seasonal variation of diurnal convective rain is more apparent than diurnal stratiform rain.The seasonal variation of the diurnal cycle is weak over the East China Sea and Tibetan Plateau.The maximum of total rain happens in the afternoon during1998–2002 over the Yangtze River basin,while it peaks in the early morning during 2003–2006,but no obvious phase differences can be found among years in the diurnal rain over the East China Sea and over the Tibetan Plateau.

A Method Fusing Conventional Wind Field with Cloud Motion Wind and Its Application in Location Forecast of the Severe Convection

Based on the fast algorithm of meteorological satellite guide wind vector tracing, cloud motion wind vector is calculated. According to the different characteristics of cloud motion wind field and sounding wind field, a method which fuses conventional data with unconventional data based on variation principle is presented. The fundamental is constructing a cost function that makes the value approach conventional data and the gradient approach unconventional data. Using this method, the conventional wind and the cloud motion wind are fused. The fused wind field has high resolu- tion. Its wind direction approaches cloud motion wind which indicates move direction of the synoptic system, and its velocity approaches conventional wind which indicates move velocity of the synoptic system. The wind field data are used for short-time forecast of severe convective weather location, which gets a good result.

ACCURACY OF THE RETRIEVED TEMPERATURE AND HUMIDITY FIELDS FOR TYPHOON HAIYAN UTILIZING THE ADVANCED TECHNOLOGY MICROWAVE SOUNDER

One-dimensional retrieval was performed on Typhoon Haiyan utilizing the advanced technology microwave sounder onboard the satellite Suomi NPP to retrieve the temperature and water vapor profiles of the typhoon.Comparisons of the retrieved profiles and ECMWF reanalysis were made to assess the results. The main conclusions are as follows.(1) The results have high spatial resolution and therefore can precisely represent the temperature and humidity distribution of the typhoon.(2) The retrieved temperature is low in the areas of low temperature and high in the areas of high temperature; similar patterns are observed for humidity. This means that systematic revision may be needed during routine application.(3) The results of the retrieved temperature and humidity profiles are generally accurate, which is quite important for typhoon monitoring.

An Investigation into the Relationship between Surface Rain Rate and Rain Depth over Southeast Asia

The relationship between surface rain rate and depth of rain system （rain depth） over Southeast Asia is examined using 10-yr Tropical Rainfall Measuring Mission （TRMM） precipitation radar （PR） measurements. Results show that, in general, a large surface rain rate is associated with a deep precipitating system, but a deep rain system may not always correspond with a large surface rain rate. This feature has a regional characteristic, Convective rain develops more frequently over land than over the ocean, while stratiform rain can extend to higher altitudes over the ocean than over land. A light surface rain rate has the largest probability to occur, regardless of rain depth. A convective rain system is more likely associated with a stronger surface rain rate than a stratiform rain system. Results show that precipitation systems involve complex microphysical processes. Rain depth is just one characteristic of precipitation. A linear relationship between surface rain rate and rain depth does not exist. Both deep convective and stratiform rain systems have reflectivity profiles that can be divided into three sections. The main difference in their profiles is at higher levels, from 4.5 km up to 19 km. For shallow stratiform rain systems, a two-section refiectivity profile mainly exists, while for convective systems a three-section profile is more common.

Diagnostic Analysis of a Rainstorm Process in Chongqing

[Objective] The research aimed to analyze a rainstorm process in Chongqing. [Methed] Based on precipitation product datasets and NCEP reanalysis data, synoptic situation and diagnostic analysis of a heavy rain process during 11 -12 May, 2012 in Chongqing were made, and the diagnostic analysis included dynamic and vapor conditions, instability index, vapor helicity and vapor divergence flux. [ Result] The east-south moving short wave trough and east-north moving southwest vortex were the main synoptic systems causing the heavy rain; the positive vorticity advection before trough and after ridge helped the ascending motion from surface; the southwest stream at 700 hPa provided vapor and energy, promoting and maintaining the intense development of convection; the higher vapor helicity and lower vapor divergence flux were well corresponding with higher precipitation area, and had well temporal correlation, which was significant for forecast of precipitation area and its development; the ascended warm wet stream on the lower air came across the cold air on the upper air, triggering the heavy rain; the Kindex and A index were significant for the heavy rain forecasting. [ Conclusion] The research could provide some references for research and forecast of future rainstorm process in Sichuan and Chongqing.

Numerical Simulation on a Heavy Rainfall Event over Jiangxi Province

[Objective] The aim was to discuss the heavy rainfall formation mechanism and to reveal the causes of rainstorm. [Method] Based on the conventional observational data, a numerical simulation and diagnosis analyses have been carried on heavy rainfall event over Jiangxi province from 16 June to 20 June 2010, with a meso-scale REM model. The results showed that this rare rainstorm was a typical heavy rainfall over Meiyu front. The cold air flow behind the 500 hPa East Asia trough and 700 hPa North China vortex joined up the southwestern flow located in the northwest part of the strong and stable subtropical high, thus the cold air and warm air converged and maintained over the northern part of Hunan and Jiangxi province. Since the area that cold air and warm air joined up was stable and the southwestern warm and wet flow was abnormally strong, the vapor, dynamical, and thermodynamic conditions was leading to the trigger development of meso-scale convection systems. The extraordinary rainstorm was caused by the interaction of many factors such as strong vapor and convergence ascending motion, weak cold air activities in middle-levels, the strengthening of southwestern low-level jet, the formation and maintenance of southwestern vortexes, etc. The simulated precipitation of the high resolution model was very similar with the observational rainfall. The model had a good predictive skill for the location, intensity and center of heavy rainfall. By diagnosing the physical variables, it found that the distribution characteristic of the physical variables had an obvious indication for precipitation forecast. [Conclusion] The study provided reference to improve rainstorm forecast.

Equilibrium Mechanism Analysis on the Physical Processes of IAP3.0

Based on the detection of the dynamic and thermodynamic functions of the physical processes in IAP3.0, the equilibrium mechanisms of the temperature, moisture and wind axe analyzed. The negative feedback between the longwave radiation and temperature is verified. The cooling regulation of net radiation on temperature is mostly balanced by the heating of precipitation; the leading actions on temperature of other processes such as vertical diffusion, shallow cumulus convection and friction are merely available for lower air. The moisture consumption of precipitation is compensated on the whole by the provision of shallow cumulus convection, which sustains the moisture conservation to a high degree. The wind field is directly regulated by the momentum redistribution of cumulus, the dry adiabatic convection and vertical diffusion. Yet, the prominent influences of these processes are generally confined to the lower level. The east wind at low latitudes and the west wind at high latitudes are both weakened by the regulations and furthermore, by virtue of the transportation of mean meridional circulation, such a variation exactly maintains the angular momentum conservation.

Seasonal variability in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon

Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations.

Improved SAL method and its application to verifying regional soil moisture forecasting

The regional verification of soil moisture is a vital step in evaluating and improving numerical model performance and utilizing forecast results. Currently, even with improved spatial and temporal resolutions of numerical model, verification methods for soil moisture data still rely on the traditional intensity verification parameters, such as mean error(ME) and root-mean-squared error(RMSE). Those methods provide only incomplete and sometimes inaccurate messages and thus hinder a proper evaluation of a forecast model. The SAL method is an object-based regional verification method with respect to precipitation forecasts. Based on the SAL method, a novel object-based method(SAL-DN) is proposed here, which can be used to test regional soil moisture. Both the ideal experiment and real experiment show that the SAL-DN method can reveal the differences between the observed and forecast soil moisture in three aspects: structure, amplitude, and location, and the results can reflect the actual situation. Furthermore, compared with the SAL method, the SAL-DN method is also capable of verifying physical quantities with high-value and low-value centers like temperature. Therefore, the SAL-DN method enhances verification accuracy and can be applied widely.

Analysis of the relation between ocean internal wave parameters and ocean surface fluctuation

The relation between ocean internal waves (IWs) and surface fluctuation is studied using a quasiincompressible two-dimensional linear ocean wave model.The main conclusions are as follows: the IW parameters can be obtained by solving the boundary value problem of ordinary differential equations with the frequency,wave number,and amplitude of the surface fluctuation.When the ocean surface fluctuation state is given,the ocean IW presents a different structure,i.e.,the uncertainty of the solution,which reflects the characteristics of the inverse problem.To obtain a definite solution,this study proposes constraint conditions for the inverse problem,namely,the relationship among background flow,buoyancy frequency,sea surface height,and geostrophic parameters.The necessary and sufficient conditions for the existence of IWs and external waves (surface wave) can be obtained according to the different constraint conditions.The amplitude of the surface fluctuation is positively correlated with IWs,and they share the same frequency and wave number.We also examined the relationship between the vertical structure,the maximum amplitude,and the constraint conditions.For a certain wave number,when the ocean environment is defined,the natural frequency (characteristic frequency) of IWs can be obtained.If the frequency of the surface fluctuation is similar or equal to the natural frequency,the resonance phenomenon will occur and can result in very strong IWs.The presented theory can serve as a basis for the analytical estimation of IWs.

MONTE-CARLO FORECASTING EXPERIMENT OF MONTHLY MEAN CIRCULATION

In 1974, in order to overcome the difficulty in the moment method, Leith put forward a statistical-dynamic integrated Monte-Carlo (M-C) approximate forecasting method, and used a homogeneity and turbulence two-dimensional model to prove that in minimum

IMPROVEMENT OF A GLOBAL SPECTRAL MODEL BY INTRODUCING THE SECONDLAW OF THERMODYNAMICS

The second law of thermodynamics has never been taken into account in the traditional hydrodynamics and numer- ical weather prediction models,which is a serious oversight in the history of mechanics.Introducing the thermodynamic irreversibility into the hydrodynamic systems,the theory and method proposed in this study would not only lead the outputs of a numerical weather prediction model to noticeable improvement,but lead the structure of hydrodynamics to deepgoing transformation.

Simulation of FY-2D infrared brightness temperature and sensitivity analysis to the errors of WRF simulated cloud variables

This study simulated FY-2 D satellite infrared brightness images based on the WRF and RTTOV models. The effects of prediction errors in WRF micro-and macroscale cloud variables on FY-2 D infrared brightness temperature accuracy were analyzed. The principle findings were as follows. In the T+0–48 h simulation time, the root mean square errors of the simulated brightness temperatures were within the range 10–27 K, i.e., better than the range of 20–40 K achieved previously. In the T+0–24 h simulation time, the correlation coefficients between the simulated and measured brightness temperatures for all four channels were >0.5. The simulation performance of water channel IR3 was stable and the best. The four types of cloud microphysical scheme considered all showed that the simulated values of brightness temperature in clouds were too high and that the distributions of cloud systems were incomplete, especially in typhoon areas. The performance of the THOM scheme was considered best, followed in descending order by the WSM6, WDM6, and LIN schemes. Compared with observed values, the maximum deviation appeared in the range 253–273 K for all schemes. On the microscale, the snow water mixing ratio of the THOM scheme was much bigger than that of the other schemes. Improving the production efficiency or increasing the availability of solid water in the cloud microphysical scheme would provide slight benefit for brightness temperature simulations. On the macroscale, the cloud amount obtained by the scheme used in this study was small. Improving the diagnostic scheme for cloud amount, especially high-level cloud, could improve the accuracy of brightness temperature simulations. These results could provide an intuitive reference for forecasters and constitute technical support for the creation of simulated brightness temperature images for the FY-4 satellite.

TIME SERIES MODEL OF LONG-RANGE PREDICTION AND ITS APPLICATION

By generalizing the concept of mean in mathematical statistics to a mean generation function(MGF), the extended matrix of MGF is defined and then a new model of time series is presented.A calculatingseheme for modelling of monovariate time series is deduced cooperating with a normalization procedure of vector and a couple score criterion.An example of climatic prediction for ten-year scale is given in this paper,the tendency of variation for every year can be predicted skillfully with the model.