A numerical experiment for the simulating effects of Kuwait oil fire and volcanoes in Philippines and Japan on the general circulation and climate

With an AGCM/ mixed-layer ocean model, a numerical experiment to investigate the ef-fects of Kuwait oil fire and volcanoes in Philippines and Japan on atmospheric general cireulationand climate is camed out. It is shown from the simulation that the effect of smoke on climate issignificant near the smoke sources, and quite weak-and-indirect in the distant areas. In the experi-ment, it is not found that the smoke had a significant effect on SST anomialy along the tropicaloceans and flood in Yangtze-Huaihe river's basin of China in the spring and summer of 1991.

Multi-year Simulations and Experimental Seasonal Predictions for Rainy Seasons in China by Using a Nested Regional Climate Model (RegCM_NCC). Part Ⅰ: Sensitivity Study

A modified version of the NCAR/RegCM2 has been developed at the National Climate Center （NCC）, China Meteorological Administration, through a series of sensitivity experiments and multi-year simulations and hindcasts, with a special emphasis on the adequate choice of physical parameterization schemes suitable for the East Asian monsoon climate. This regional climate model is nested with the NCC/IAP （Institute of Atmospheric Physics） T63 coupled GCM to make an experimental seasonal prediction for China and East Asia. The four-year （2001 to 2004） prediction results are encouraging. This paper is the first part of a two-part paper, and it mainly describes the sensitivity study of the physical process paraxneterization represented in the model. The systematic errors produced by the different physical parameterization schemes such as the land surface processes, convective precipitation, cloud-radiation transfer process, boundary layer process and large-scale terrain features have been identified based on multi-year and extreme flooding event simulations. A number of comparative experiments has shown that the mass flux scheme （MFS） and Betts-Miller scheme （BM） for convective precipitation, the LPMI （land surface process model I） and LPMII （land surface process model Ⅱ） for the land surface process, the CCM3 radiation transfer scheme for cloud-radiation transfer processes, the TKE （turbulent kinetic energy） scheme for the boundary layer processes and the topography treatment schemes for the Tibetan Plateau are suitable for simulations and prediction of the East Asia monsoon climate in rainy seasons. Based on the above sensitivity study, a modified version of the RegCM2 （RegCM_NCC） has been set up for climate simulations and seasonal predictions.

Adjoint Sensitivity Experiments of a Meso-β-scale Vortex in the Middle Reaches of the Yangtze River

A relatively independent and small-scale heavy rainfall event occurred to the south of a slow eastwardmoving meso-α-scale vortex. The analysis shows that a meso-β-scale system is heavily responsible for the intense precipitation. An attempt to simulate it met with some failures. In view of its small scale, short lifetime and relatively sparse observations at the initial time, an adjoint model was used to examine the sensitivity of the meso-β-scale vortex simulation with respect to initial conditions. The adjoint sensitivity indicates how small perturbations of initial model variables anywhere in the model domain can influence the central vorticity of the vortex. The largest sensitivity for both the wind and temperature perturbation is located below 700 hPa, especially at the low level. The largest sensitivity for the water vapor perturbation is located below 500 hPa, especially at the middle and low levels. The horizontal adjoint sensitivity for all variables is mainly located toward the upper reaches of the Yangtze River with respect to the simulated meso-β-scale system in Hunan and Jiangxi provinces with strong locality. The sensitivity shows that warm cyclonic perturbations in the upper reaches can have a great effect on the development of the meso-β-scale vortex. Based on adjoint sensitivity, forward sensitivity experiments were conducted to identify factors influencing the development of the meso-β-scale vortex and to explore ways of improving the prediction. A realistic prediction was achieved by using adjoint sensitivity to modify the initial conditions and implanting a warm cyclone at the initial time in the upper reaches of the river with respect to the meso-β-scale vortex, as is commonly done in tropical cyclone prediction.

AN EFFICIENT SEQUENTIAL DESIGN FOR SENSITIVITY EXPERIMENTS

In sensitivity experiments, the response is binary and each experimental unit has a critical stimulus level that cannot be observed directly. It is often of interest to estimate extreme quantiles of the distribution of these critical stimulus levels over the tested products. For this purpose a new sequential scheme is proposed with some commonly used models. By using the bootstrap repeated-sampling principle, reasonable prior distributions based on a historic data set are specified. Then, a Bayesian strategy for the sequential procedure is provided and the estimator is given. Further, a high order approximation for such an estimator is explored and its consistency is proven. A simulation study shows that the proposed method gives superior performances over the existing methods.

Experimental Measurements of the Sensitivity of Fiber-optic Bragg Grating Sensors with a Soft Polymeric Coating under Mechanical Loading,Thermal and Magnetic under Cryogenic Conditions

The strain and temperature sensing performance of fiber-optic Bragg gratings （FBGs） with soft polymeric coating, which can be used to sense internal strain in superconducting coils, are evaluated under variable cryogenic field and magnetic field. The response to a temperature and strain change of coated-soft polymeric FBGs is tested by comparing with those of coated-metal FBGs. The results indicate that the coated-soft polymeric FBGs can freely detect temperature and thermal strain, their At variable magnetic field, the tested results indicate accuracy and repeatability are also discussed in detail. that the cross-coupling effects of FBGs with different matrixes are not negligible to measure electromagnetic strain during fast excitation. The present results are expected to be able to provide basis measurements on the strain of pulsed superconducting magnet/cable （cable- around-conduit conductors, cable-in-conduit conductors）, independently or utilized together with other strain measurement methods.

Effect of compressive strength on the performance of the NEMO-LIM model in Arctic Sea ice simulation

Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s.The prediction of sea ice is highly important,but accurate simulation of sea ice variations remains highly challenging.For improving model performance,sensitivity experiments were conducted using the coupled ocean and sea ice model(NEMO-LIM),and the simulation results were compared against satellite observations.Moreover,the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed.The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant(C^(rhg)).By reducing the C^(rhg) constant,the sea ice compressive strength increases,leading to improved simulated sea ice states.The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength.Meanwhile,dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration,reducing the simulation bias in the central Arctic Ocean in summer.The root mean square error(RMSE)between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution.The ice thickness,especially of multiyear thick ice,was also reduced and matched with the satellite observation better in the freezing season.These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes.

A Heavy Sea Fog Event over the Yellow Sea in March 2005: Analysis and Numerical Modeling

In this paper, a heavy sea fog episode that occurred over the Yellow Sea on 9 March 2005 is investigated. The sea fog patch, with a spatial scale of several hundred kilometers at its mature stage, reduced visibility along the Shandong Peninsula coast to 100 m or much less at some sites. Satellite images, surface observations and soundings at islands and coasts, and analyses from the Japan Meteorology Agency （JMA） axe used to describe and analyze this event. The analysis indicates that this sea fog can be categorized as advection cooling fog. The main features of this sea fog including fog area and its movement axe reasonably reproduced by the Fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model （MM5）. Model results suggest that the formation and evolution of this event can be outlined as： （1） southerly warm/moist advection of low-level air resulted in a strong sea-surface-based inversion with a thickness of about 600 m; （2） when the inversion moved from the warmer East Sea to the colder Yellow Sea, a thermal internal boundary layer （TIBL） gradually formed at the base of the inversion while the sea fog grew in response to cooling and moistening by turbulence mixing; （3） the sea fog developed as the TIBL moved northward and （4） strong northerly cold and dry wind destroyed the TIBL and dissipated the sea fog. The principal findings of this study axe that sea fog forms in response to relatively persistent southerly waxm/moist wind and a cold sea surface, and that turbulence mixing by wind shear is the primary mechanism for the cooling and moistening the marine layer. In addition, the study of sensitivity experiments indicates that deterministic numerical modeling offers a promising approach to the prediction of sea fog over the Yellow Sea but it may be more efficient to consider ensemble numerical modeling because of the extreme sensitivity to model input.

New Evidences on the Climatic Causes of the Formation of the Spring Persistent Rains over Southeastern China

The spring persistent rains（SPR）over southeastern China（SEC）are a unique synoptic and climatic phenomenon in East Asia.A former study has found that the southwesterly flow which lies on the southeastern flank of the Tibetan Plateau（TP）is one of the deflected westerly flows of the TP,and it is suggested to be the direct climatic cause of SPR.This study found that the southwesterly flow is also highly correlated with the sensible heating of the southeastern TP in interannual variability,in addition to having a high correlation in seasonal variability.These facts suggest that the thermal forcing of the TP is another important climatic cause of SPR.Numerical sensitivity experiments further prove that the mechanical and thermal forcings of the TP are the climatic causes of the formation of the SPR.On the other hand,the Nanling Mountains and Wuyi Mountains（NWM）over southeastern China not only increase the SPR precipitation amount evidently,but also make the SPR rain belt move to the south by blocking the strong southwesterly flow.

Primary Reasoning behind the Double ITCZ Phenomenon in a Coupled Ocean-Atmosphere General Circulation Model

This paper investigates the processes behind the double ITCZ phenomenon, a common problem in Coupled ocean-atmosphere General Circulation Models (CGCMs), using a CGCM—FGCM-0 (Flexible General Circulation Model, version 0). The double ITCZ mode develops rapidly during the ?rst two years of the integration and becomes a perennial phenomenon afterwards in the model. By way of Singular Value Decomposition (SVD) for SST, sea surface pressure, and sea surface wind, some air-sea interactions are analyzed. These interactions prompt the anomalous signals that appear at the beginning of the coupling to develop rapidly. There are two possible reasons, proved by sensitivity experiments: (1) the overestimated east-west gradient of SST in the equatorial Paci?c in the ocean spin-up process, and (2) the underestimated amount of low-level stratus over the Peruvian coast in CCM3 (the Community Climate Model, Version Three). The overestimated east-west gradient of SST brings the anomalous equatorial easterly. The anomalous easterly, a?ected by the Coriolis force in the Southern Hemisphere, turns into an anomalous westerly in a broad area south of the equator and is enhanced by atmospheric anomalous circulation due to the underestimated amount of low-level stratus over the Peruvian coast simulated by CCM3. The anomalous westerly leads to anomalous warm advection that makes the SST warm in the southeast Paci?c. The double ITCZ phenomenon in the CGCM is a result of a series of nonlocal and nonlinear adjustment processes in the coupled system, which can be traced to the uncoupled models, oceanic component, and atmospheric component. The zonal gradient of the equatorial SST is too large in the ocean component and the amount of low-level stratus over the Peruvian coast is too low in the atmosphere component.

A Nine-layer Atmospheric General Circulation Model and Its Performance

Different versions of a new nine-layer general circulation model which is rhomboidally truncated at zonal wavenumber 15(L9R15)are introduced in this paper.On using the observed global monthly sea surfaCe temperature(SST)and sea ice(SI)data from 1979 to 1988 offered by the internahonal Atmospheric Model Iute-comparison Program(AMIP),these different model versions were integrated for the ten-year AMIP period. Results show that the model iscapable of simulating the basic states of the atmosphere and its interannual variability,and in performing reasonablesensitivity experiments.

Impacts of Initial Conditions on Cloud-Resolving Model Simulations

Impacts of initial conditions on cloud-resolving model simulations are investigated using a series of sensitivity experiments. Five experiments with perturbed initial temperature, moisture, and cloud conditions are conducted and compared to the control experiment. The model is forced by the large-scale vertical velocity and zonal wind observed and derived from NCEP/Global Data Assimilation System （GDAS）. The results indicate that model predictions of rainfall are much more sensitive to the initial conditions than those of temperature and moisture. Further analyses of the surface rainfall equation and the moisture and cloud hydrometeor budgets reveal that the calculations of vapor condensation and deposition rates in the model account for the large sensitivities in rainfall simulations.

Simulating global soil-CO_2 flux and its response to climate change

It has been argued that increased soil respiration would become a major atmospheric source of CO\-2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0 5°×0 5° longitude/latitude resolution to simulate global soil\|CO\-2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil\|CO\-2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil\|CO\-2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature, precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil\|CO 2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO 2, it can be found that the largest increases in soil\|CO 2 fluxes were associated with the boreal and tundra regions. The globally averaged soil\|CO 2 fluxes were estimated to increase by about 35% above current values, providing a positive feedback to the greenhouse effect.

Sensitivity and nonlinearity of Eurasian winter temperature response to recent Arctic sea ice loss

The recent decline in the Arctic sea ice has coincided with more cold winters in Eurasia. It has been hypothesized that the Arctic sea ice loss is causing more mid-latitude cold extremes and cold winters, yet there is lack of consensus in modeling studies on the impact of Arctic sea ice loss. Here we conducted modeling experiments with Community Atmosphere Model Version 5 （CAM5） to investigate the sensitivity and linearity of Eurasian winter temperature response to the Atlantic sector and Pacific sector of the Arctic sea ice loss. Our experiments indicate that the Arctic sea ice reduction can significantly affect the atmospheric circulation by strengthening the Siberian High, exciting the stationary Rossby wave train, and weakening the polar jet stream, which in turn induce the cooling in Eurasia. The temperature decreases by more than I^C in response to the ice loss in the Atlantic sector and the cooling is less and more shifts southward in response to the ice loss in the Pacific sector. More interestingly, sea ice loss in the Atlantic and Pacific sectors together barely induces cold temperatures in Eurasia, suggesting the nonlinearity of the atmospheric response to the Arctic sea ice loss.

Forecasting the western Pacific subtropical high index during typhoon activity using a hybrid deep learning model

Seasonal location and intensity changes in the western Pacific subtropical high(WPSH)are important factors dominating the synoptic weather and the distribution and magnitude of precipitation in the rain belt over East Asia.Therefore,this article delves into the forecast of the western Pacific subtropical high index during typhoon activity by adopting a hybrid deep learning model.Firstly,the predictors,which are the inputs of the model,are analysed based on three characteristics:the first is the statistical discipline of the WPSH index anomalies corresponding to the three types of typhoon paths;the second is the correspondence of distributions between sea surface temperature,850 hPa zonal wind(u),meridional wind(v),and 500 hPa potential height field;and the third is the numerical sensitivity experiment,which reflects the evident impact of variations in the physical field around the typhoon to the WPSH index.Secondly,the model is repeatedly trained through the backward propagation algorithm to predict the WPSH index using 2011–2018 atmospheric variables as the input of the training set.The model predicts the WPSH index after 6 h,24 h,48 h,and 72 h.The validation set using independent data in 2019 is utilized to illustrate the performance.Finally,the model is improved by changing the CNN2D module to the DeCNN module to enhance its ability to predict images.Taking the 2019 typhoon“Lekima”as an example,it shows the promising performance of this model to predict the 500 hPa potential height field.

A GCM Study on the Mechanism of Seasonal Abrupt Changes

In this paper the observational studies and some related dynamical and numerical researches on seasonal abrupt changes were reviewed first. Then a speculation that the seasonal variation of insolation and the nonlinear dynamic interaction account for the abrupt changes was put forward and was asserted by a set of GCM sensitivity experiments. The results show that the abrupt changes would exist in case that all the earth surface was grass land and there was no topography. However, many factors may have influences on the abrupt changes. Hence this phenomenon is quite complicated and needs further investigations.

Impact of Different Guidances on Sensitive Areas of Targeting Observations Based on the CNOP Method

The conditional nonlinear optimal perturbations（CNOPs） obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional prediction model-the Global/Regional Assimilation and PrEdiction System（GRAPES）.Through a series of sensitivity experiments,several issues on targeting strategy design are discussed,including the effectivity of different guidances to determine the sensitive area（or targeting area） and the impact of sensitive area size on improving the 24-h forecast.In this study,three guidances are used along with the CNOP to find sensitive area for improving the 24-h prediction of sea level pressure and accumulated rainfall in the verification region.The three guidances are based on winds only;on winds,geopotential height,and specific humidity;and on winds,geopotential height,specific humidity,and observation error,respectively.The distribution and effectivity of the sensitive areas are compared with each other,and the results show that the sensitive areas identified by the three guidances are different in terms of convergence and effectivity.All the sensitive areas determined by these guidances can lead to improvement of the 24-h forecast of interest. The second and third guidances are more effective and can identify more similar sensitive areas than the first one.Further,the size of sensitive areas is changed the same way for three guidances and the 24-h accumulated rainfall prediction is examined.The results suggest that a larger sensitive area can result in better prediction skill,provided that the guidance is sensitive to the size of sensitive areas.

MODIFIED MASS FLUX CUMULUS CONVECTIVE PARAMETERIZATION SCHEME AND ITS SIMULATION EXPERIMENT—PART II:CUMULUS CONVECTION ACTIVITIES SIMULATED FROM THREE SCHEMES AND SENSITIVITY EXPERIMENTS BY USE OF MASS FLUX SCHEME

By comparison of simulated cumulus convection processes in RegCM2,using the Kuo scheme, the Grell scheme and the mass flux scheme (MFS),it is found that the MFS can simulate the cumulus heating and moistening very well.A series of sensitivity tests show that the parameters for specifying the conversion coefficient from cloud droplets to raindrops,the turbulent entrainment and detrainment rates in updrafts anddowndrafts,and the intensity of thedowndrafts have different degrees of influence upon the cumulus convection.Therefore.it is quite important for cumulus parameterization scheme to define these parameters as accurately as possible.

AN IMPROVED LAND-SURFACE PROCESS MODEL AND ITS SIMULATION EXPERIMENT——PART I:LAND-SURFACE PROCESS MODEL AND ITS“OFF-LINE”TESTS AND PERFORMANCE ANALYSES

Based on the existing land-surface schemes and models,an improved Land-surface Process Model(LPM-ZD)has been developed.It has the following major characteristics:(1)The combination of physical equations and empirical analytical formulae are used to construct the governing equations of soil temperature and moisture.Higher resolution of model level and physical equations are adopted for the upper soil layers,and for the lower soil layers,lower resolution of model level is adopted and empirical analytical formulae are used.(2)In land surface hydrological process,the sub-grid distribution of rainfall and its effects are taken into account. (3)A simple snow cover submodel has been used,which includes effects of snow cover on soil thermodynamics and hydrology,as well as albedo. By use of this model and three groups of point observation data,a series of“off-line”tests have been carried out.The simulation results indicate that land-surface process model has good performance and can well simulate diurnal and seasonal variation of land surface processes for many kinds of land surface covers(forest,grass,crops and desert)in different climate zone.The results simulated by the model are consistent with the observations.Later,by use of one group of observation data and the model,a series of sensitivity experiments have been done.It is shown that the model is much sensitive to some parameters,such as initial soil moisture,vegetation physical parameters as well as the proportion of the grid covered with rain.Therefore it is much important for land-surface process model to define these parameters as accurately as possible.

NUMERICAL PREDICTION EXPERIMENT OF AN ADVECTION FOG IN NANLING MOUNTAIN AREA

Now more comprehensive cloud microphysical processes have been included in advanced three- dimensional mesoscale meteorological model such as PSU/NCAR MM5 model,so the model can be used in the prediction of fog.In this paper,MM5 was utilized to simulate an advection fog occurring in Nanling Mountain area.The simulated results were compared with the facts obtained by detailed observation experiment.The results showed that the simulation was successful in the following aspects:(1)the formation and development of the fog;(2)the temporal variation of the maximum liquid water content;(3)the diffusion of the cold air,especially the temporal variation of the ground temperature;and (4)the uplift of the air and the formation and development of the low-lever inversion.Besides,we did some sensitivity numerical experiments and discussed the effects of the radiation,the release of condensation latent heat and the change of soil moisture and temperature on the formation and development of fog.The success of numerical simulation experiment of fog has proved that the numerical forecasting of fog is promising.

DEVELOPMENT OF THE 2-D COUPLED STRATOSPHERICTROPOSPHERIC DYNAMICAL-RADIATIVE-CHEMICAL MODEL—PART Ⅱ:THE RESULTS AND DISCUSSION OF SENSITIVITY EXPERIMENTS

By using the 2-D stratospheric-tropospheric dynamic-radiative-chemical coupled model,some sensitivity experiments have been done,which are interactions among ozone,radiation and temperature,vapor effects,as well as effects of source and sink.The result of temperature experiment shows that feedback interaction among ozone,radiation and temperature,mainly occurs in the upper and middle stratosphere,the maximum of ozone concentration decrease is 1 ppm,the maximum of temperature change is 6 K,and the maximum of total ozone change is 20 DU.From the experiment of water vapor,we can see that the area of the middle and high latitudes of the Northern Hemisphere is sensitive to vapor change.When the maximum difference between both surface sources is in the Antarctic,the maximum of ozone change is also there.Because the character of surface varies with latitude,dry deposition is different in different latitudes.The change of dry deposition makes ozone in boundary layer quite obvious,especially in both poles. The maximum change of total volume ozone in experiments of vapor,source and sink is more than 12 DU.