The potential impact of climate changes on winter wheat production in China was evaluated using an approach liking the CERES-Wheat model to both the local current weather data and the doubled CO2 climate change scenario generated by the GISS GCM. Changes in overall output of winter wheat in China were also estimated, using a statistical model. Several agroclimatic indices were finally adopted to analyze possible changes in moisture condition, northern limits, varietal disposition, and cropping systems for winter wheat throughout the country.
Abstract Tropical cyclone (TC) genesis forecasts during 2018–20 from two operational global ensemble prediction systems (EPSs) are evaluated over three basins in this study. The two ensembles are from the European Centre for Medium-Range Weather Forecasts (ECMWF-EPS) and the MetOffice in the United Kingdom (UKMO-EPS). The three basins include the northwest Pacific, northeast Pacific, and the North Atlantic. It is found that the ensemble members in each EPS show a good level of agreement in forecast skill, but their forecasts are complementary. Probability of detection (POD) can be doubled by taking all the member forecasts in the EPS into account. Even if an ensemble member does not make a hit forecast, it may predict the presence of cyclonic vortices. Statistically, a hit forecast has more nearby disturbance forecasts in the ensemble than a false alarm. Based on the above analysis, we grouped the nearby forecasts at each model initialization time to define ensemble genesis forecasts, and verified these forecasts to represent the performance of the ensemble system. The PODs are found to be more than twice that of the individual ensemble members at most lead times, which is about 59% and 38% at the 5-day lead time in UKMO-EPS and ECMWF-EPS, respectively; while the success ratios are smaller compared with that of the ensemble members. In addition, predictability differs in different basins, and genesis events in the North Atlantic basin are the most difficult to forecast in EPS, and its POD at the 5-day lead time is only 46% and 23% in UKMO-EPS and ECMWF-EPS, respectively. Significance Statement Operational forecasting of tropical cyclone (TC) genesis relies greatly on numerical models. Compared with deterministic forecasts, ensemble prediction systems (EPSs) can provide uncertainty information for forecasters. This study examined the predictability of TC genesis in two operational EPSs. We found that the forecasts of ensemble members complement each other, and the detection ratio of observed genesis will be doubled by considering the forecasts of all members, as multiple simulations conducted by the EPS partially reflect the inherent uncertainties of the genesis process. Successful forecasts are surrounded by more cyclonic vortices in the ensemble than false alarms, so the vortex information is used to group the nearby forecasts at each model initialization to define ensemble genesis forecasts when evaluating the ensemble performance. The results demonstrate that the global ensemble models can serve as a valuable reference for TC genesis forecasting.
Abstract Recent composite analysis of landfalling tropical cyclones (TCs) suggests a rain rate peak in the early morning, which contradicts the typically observed peak in convective precipitation over land seen in the late afternoon to early evening. We conducted a set of idealized simulations of TCs and analyzed observational data from TC Bebinca (2018), which stalled near the shoreline of southern China. We show a distinct land–sea contrast in the diurnal variation of TC precipitation and an 8–12 hr offset between the peak precipitation time over land compared with that over the sea in a TC that stalls at the shoreline. The highest land surface temperature and maximum low‐level buoyancy during the afternoon led to peak precipitation over land at this time. However, the peak precipitation over the sea in the early morning was generated by the increase in relative humidity caused by nighttime radiative cooling and enhanced instability.
With the use of conventional observations,NCEP/NCAR reanalysis,FY-2E infrared satellite imagery,Doppler radar and automatic weather stations data,synoptic analysis is conducted of the severe convection event on 6 May 2010 in Chongqing,focusing on the evolutions of different weather systems and their interactions.A conceptual model of synoptic background for this case is proposed.The results show that this event occurred under the background that midlatitude cyclone,anticyclone and upper trough were growing.Between the surface cyclone and anticyclone,a cold front emerged and intensified during southward propagation.Moreover,the extratropical weather systems made up a deformation field with the cyclone in the southwest and the subtropical high which caused frontogenesis north to Chongqing.Consequently,not only the cold front intensified,but a positive feedback interaction resulted as well between low level frontogenesis and midlevel jet via secondary circulation,which enhanced the lower level convergence and associated lifting over Chongqing,destabilizing the atmosphere and providing a possible initiation mechanism.Meanwhile,lower levels over Chongqing was constantly dominated by southerly wind in the eastern part of the southwest cyclone,which transported abundant moisture from South China Sea and provided a very warm environment in company with solar radiation,resulting in conditional instability.Up to the evening of 5 May the cold front had arrived Chongqing and the strong convergence nearby caused initial development of convection.It appears that the formation of the convergence directly responsible for the storms initiation should be related to the downslope topography when the cold front entered into Sichuan Basin.In addition,the subtropical upper level jet induced strong vertical wind shear and upper level divergence were also favorable for the development of deep convection.
Finance is an essential factor for accelerating the process of urbanization.Prospected from the system,the delay of the reform of rural financial system is one of the most important factors that restrict the process of urbanization.It is believed that the imperfect structure of the rural financial system and the lack of supportive environment are the main problems of rural financial system in the process of urbanization.For this reason,the reform of rural financial system should be carried out from the viewpoint of improving the structure of rural financial system in the process of urbanization,which includes perfecting organization system,market system,regulatory system and government function.A favorable environment should be created for the operation of finance in order to accelerate the process of urbanization.
Challenges persist in accurately predicting sharp changes in tropical cyclone (TC) motion over a short period of time, even with the employment of state-of-art forecasting technologies. The precise connection between these sudden changes and specific TC structure remains unclear. Here, we delve into the relationship between TC asymmetry (TCA) of outer-core size and anomalous motion, using best-track data spanning the period from 2001 to 2022. Results indicate that TCs characterized by lower TCA tend to display more pronounced deflections than their normal motion. Furthermore, fast-moving TCs exhibit heightened asymmetry and a propensity to accelerate, whereas slow-moving ones lean towards greater symmetry. In addition, TCs demonstrating substantial angular deviations are more prevalent at lower speeds, while fast-moving ones rarely generate anomalous deflections. These findings provide valuable insights into the potential impact of TCA on anomalous TC motion, which can ultimately be used to enhance the accuracy of TC track forecasting.
In this work, the impact of topography on the geostrophic adjustment process is discussed with a simple two-layer shallow water model, in which the lower-layer uid is initially stationary while the upper-layer is perturbed by the impulsive injection of momentum. During the geostrophic adjustment process of this ideal model, the initial kinetic energy is released and a fraction of it is converted into potential energy of the nal geostrophically adjusted state. Thus, after the geostrophic adjustment, the kinetic energy of the system is reduced while the potential energy is enhanced. As the topographic eect is considered, it is found that the decrease of the kinetic energy ( KE) and the increase of the potential energy ( P E) of the system are weakened as compared to the case that the lower boundary is at. Furthermore, the topographic eect on P E is less pronounced than that on KE, which implicates that the topography tends to inhibit the energy dispersion of the inertio-gravity wave. The numerical simulation of the geostrophic adjustment process shows that, due to the impact of topography, the convergence and divergence in the low layer are reduced and the undulation of the interface between the lower-layer and upper-layer is weakened. This means that the amplitude of the inertio-gravity wave is decreased, and thus, the energy radiated by the inertio-gravity wave is lessened.
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